5th International Seminar on
ORC Power Systems
Athens Greece

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17:20   Poster session and Ouzo tasting in room Kallirhoe Performance and Cost Effects of Nanonrefrigerants Within a Low-temperature ORC for Waste Heat Recovery George Kosmadakis, Panagiotis Neofytou Abstract: The mixing of nanoparticles (NPs) with refrigerants introduces some favourable effects, with the main being the heat transfer enhancement during boiling and condensation. However, the resulting effective viscosity increases for higher NP loading, resulting to a larger pressure drop. Various nanorefrigerants have been examined in refrigeration and heat pump units, demonstrating the heat transfer coefficient increase. The present work provides some further insights of nanorefrigerants in an ORC supplied by a low-temperature heat source of 100 oC, employing R245fa and R1234ze(Z) as the base fluids. For this purpose, an existing thermodynamic model is extended to account for these particles, introducing their effect in the energy balance, and the heat transfer and pressure drop correlations. Two NP materials with different thermophysical properties are considered, already used in many refrigeration cases, namely Al2O3 and Cu. The numerical model has been applied to simulate the ORC with a variable NP mass fraction (from 0 up to 10% wt.), with the aim to identify the performance improvement. Focus is given on the heat transfer coefficients in the evaporator and the condenser, as well as the pressure drop in the different parts of the cycle. The results show that the thermal efficiency slightly increases for higher NP mass fraction and especially with the use of Al2O3. This is mostly attributed to the expansion process, in which the NPs act as internal heat sources to the vapour organic fluid during this process. The effect of the NPs on the heat transfer process in the two heat exchangers is minor, due to their low volume fraction in the vapour phase, resulting to small changes in the thermal conductivity. The increase in the pressure drop is minor even if the effective viscosity increases for higher NP mass fraction. Finally, a preliminary cost analysis of the nanorefrigerants in an ORC has been conducted, showing that their use results to a payback period of 12.8 years with Al2O3. The sensitivity analysis revealed that this period can be reduced to half, assuming that they can sustain a long-term operation under cycling conditions. Modelling of Commercial Biomass-fired ORC System Using EBSILON Professional (TM) Software Mateusz Świerzewski, Jacek Kalina Abstract: This paper demonstrates the use of the commercial software Ebsilon ProfessionalTM for modelling and diagnostics of an industrial scale biomass-fired cogeneration system with ORC technology. The software is an object oriented simulator of thermodynamic systems in steady state conditions. It is capable of modelling of complex energy conversion systems under design and off-design conditions (i.e. under nominal and partial load). The model consists of a system of individual components. The model equations describe individual thermodynamic processes as well as mass and energy balances. Each component is additionally described with relevant equations of built-in operational characteristics, which can be modified by the user. Detailed model of the real plant in Krosno (Poland) with the Turboden T14 CHP Split ORC unit and the VAS biomass boiler is built. All stages of the model development are presented as well as functionality of the model is discussed. The model comprises biomass combustion system, thermal oil circuit and the ORC process. It is calibrated with the plant measurement data obtained from the SCADA system. Then the analysis of plant’s performance under variable operational conditions such as biomass humidity, thermal oil temperature, network water temperature, etc. is performed. The results reveal off-design characteristics of the system that is represented by power output, heat to power ratio, power generation efficiency and overall efficiency. Finally there is presented an example of using the model for sizing of a heat storage vessel. ORC Integrated into Engine for Simplified Direct Waste Heat Recovery from Cooling and Flue Gas – System Considerations David Szucs, Jan Spale, Vaclav Novotny, Vaclav Vodicka, Jacub Mascuch Abstract: Current systems of waste heat recovery (WHR) in internal combustion engines (ICE) are typically considered only for exhaust gas of the engine. The heat can be utilized directly for recuperation into heating system or in bottoming ORC system. These applications are mostly mature technologies. ICE additionally requires cooling of the cylinders to prevent overheating. Low-potential heat recovered from engine cooling system is not typically utilized and is released to the environment. Some projects have studied a use of jacket-cooling heat in a bottoming cycle or for preheating of the working fluid, but only through an intermediate cooling fluid loop. A novel integrated ICE-ORC system that uses both high-potential heat from the exhaust gas and low-potential heat from the jacket cooling system is presented. The novelty is in direct use of the organic working fluid of the ORC system in the jacket cooling. The ability and the limits of the cooling systems of conventional ICEs are explored and analysed in the work. The advantage of the novel ICE-ORC system is in reduction of capital costs and complexity of the system by eliminating the intermediate cooling fluid loop, as well as in an increase of total power output and fuel utilization efficiency. This work presents the results for ORC integration into a small-scale 22 kWe ICE. Theoretical analyses for a range of system parameters of the novel system show expectation of 5-6 % increase in total power output. Design considerations are discussed, such as material compatibility, pressure limits, heat transfer considerations or overall operation regimes. Lastly an experimental design for future experiments is shown. Potential and Cost Effectiveness of a Reversible High-temperature Heat Pump/ORC Unit for the Exploitation of Industrial Waste Heat George Kosmadakis, Panagiotis Neofytou Abstract: ORC units have demonstrated their potential for the exploitation of waste heat sources in industry, with many applications even at low-temperatures of 100 oC. At the same time, high-temperature heat pumps have been developed for various industrial sectors to exploit the waste heat thus producing useful heat, and subsequently recycling the heat quantities instead of rejecting them to the ambient. These two components can be combined within a single unit, by reversing the heat pump cycle for operation as a heat-to-power unit, resulting to an ORC. This is achieved with few modifications, such as the addition of a pump for ORC mode and minor auxiliaries. The resulting reversible high-temperature heat pump/ORC can then exploit the low-temperature industrial waste heat and produce either electricity (ORC operation) or upgraded heat (heat pump operation), according to: (1) the real-time needs for process heating and electricity, and (2) the economic benefits derived from each operating mode, which depend on the local energy prices and fluctuations. The current work investigates the potential of this reversible concept at industrial settings. Focus is given on the exploitation of low-temperature waste heat of 100 oC, in order for the heat pump to produce useful heat with a temperature lift of up to 50 K, which is close to its upper temperature limit, while at ORC mode the thermal efficiency is 4.5%. The maximum heat pump capacity is 1000 kW, defining accordingly the maximum ORC capacity, representing the actual sizes in small/medium-scale industries, and considering a variable operating load. Various scenarios are examined that lead to different operational hours of each mode, according to the temporal profile of the heating load and the heat pump capacity. The results of this analysis show the energy production of each mode, as well as of the whole reversible unit. To quantify the benefits of this reversible unit, a cost analysis is implemented, using average energy prices for electricity and gas of medium-sized EU industries, subjected to a sensitivity analysis. Various scenarios are considered, showing that the payback period of the high-temperature heat pump only can be as short as 5 years, and of the complete reversible unit lower by about 20% in some conditions. Therefore, the reversibility option except from introducing superior flexibility on operation, it also enhances the cost-effectiveness and fully justifies the more complex configuration. Preliminary Experimental Investigation of a Biomass-fired ORC-based CHP System for an Indoor Swimming Pool Márcio Santos, Jorge André, Ricardo Mendes, José Ribeiro Abstract: Small-scale CHP systems are particularly suitable for applications in commercial and domestic buildings because not only reduces the losses of the energy conversion process but also avoids the losses associated with its transportation and distribution, improving the sustainability of the whole process. This work presents the preliminary results of an experimental investigation of a biomass-fired CHP system based on an organic Rankine cycle (ORC) in a lab-scale test-rig that intends to emulate an indoor swimming pool. After a thorough investigation of possible CHP applications, indoor swimming pools fitted the requirements, reasonable high thermal needs at relatively low temperature. For a real cycle, the performance of the ORCs vary with several factors, such as the heat source temperature, heat sink conditions, the load of the system and the expansion machine. The test-rig includes a biomass boiler (350 kWt) as heat source and uses the hot water at 95ºC to evaporate the working fluid of the ORC and to heat up the domestic hot waters. The use of hot water from the boiler at a quite low temperature allows the application of the ORC module to existing installations. The organic Rankine cycle runs with R245fa as the ORC working fluid, plate heat exchangers are adopted for evaporator and condenser and a radial flow type turbine to simultaneously heat the indoor swimming pool water and produce electricity. Experiments were conducted to evaluate the performance of the developed system for different customer heat demands. The impact of the fluid charge on the ORC was evaluated on the CHP performance in the design and part-load conditions. The experimental data obtained in the tests were compared with the previously developed simulation model. The system developed in this study and the experimental results may serve as tools for proof of concept and further optimization of ORC-based CHP systems. Performance of Two Absorption-compression Hybrid Refrigeration Systems Using R1234ze(E)/Ionic Liquid as Working Pair Zheng Ye, Xiangyang Liu, Chang Song, Maogang He Abstract: Energy consumption is growing fast all over the world, the low-grade heat like solar energy, geothermal energy and waste heat released during industry processes is viewed as a source of recyclable energy. Absorption refrigeration technology has attracted much attention and been investigated from different aspects in recent years due to its feasibility to be driven by low-grade heat. However, the most commonly used working pairs of the absorption refrigeration system are NH3/H2O and H2O/LiBr have some obvious drawbacks including crystallization, corrosion, negative pressure operation and toxicity, etc. Ionic liquids (ILs) are a class of liquid salts with many advantages such as non-volatility, good thermal and chemical stability, low melting point, nontoxicity, etc. Hydrofluoroolefin (HFO) is the promising alternative of HFC, which has no damage to ozone layer and nearly won’t lead to global warming. Therefore, HFO/IL is a kind of promising working pair to replace H2O/LiBr and NH3/H2O. In this work, two new absorption-compression hybrid refrigeration systems using R1234ze(E)/[HMIM][BF4], R1234ze(E)/[EMIM][BF4] and R1234ze(E)/[OMIM][BF4] as novel working pair are proposed. The effects of compressor position, compression ratio, generation temperature, evaporation temperature, condensation temperature and absorption temperature on the coefficient of performance (COP) and circulation ratio (f) were analyzed. Comparison result shows that the two systems have many advantages over the single-effect absorption refrigeration system including increasing COP, reducing the heat load of condenser and f, and enlarge the operation range of generation temperature, evaporation temperature and absorption temperature. R1234ze(E)/[OMIM][BF4] shows better cooling performance than R1234ze(E)/[EMIM][BF4] and R1234ze(E)/[HMIM][BF4] due to its favourable thermophysical properties. Thermodynamic Analysis of a Novel Organic Rankine Cycle Integrated with Absorption-compression Refrigeration Cycle with Hydrofluoroolefins/Ionic Liquid as Working Fluid Zheng Ye, Xiangyang Liu, Chang Song, Maogang He Abstract: With the development of industrialization, the energy consumption rises very rapidly. Organic Rankine cycle (ORC) is able to convert the exhaust heat into useable energy, so it has attached much attention. However, the exhaust vapor of ORC still have high-temperature heat which can be recovered. Absorption refrigeration cycle (ARC) is an effective way to recover waste heat of the exhaust vapor of ORC. However, the widely used working pairs (NH3/H2O and H2O/LiBr) of ARC have obvious drawbacks including crystallization, corrosion, negative pressure operation and toxicity, etc. Ionic liquids (ILs) are a new class of liquids which are thought to be superior substitute for conventional absorbent because of their advantages such as non-volatility, good thermal and chemical stability, low melting point, non-crystallization, nontoxicity, etc. Hydrofluoroolefin (HFO) is the possible alternative of HFC, which has zero ozone depletion potential and nearly zero global warming potential. Therefore, HFO and ionic liquid are promising working pair for ARC. In this paper, a novel system combining absorption-compression refrigeration cycle (ACRC) with ORC using HFO/IL working fluid is proposed. The ACRC unitizes the heat of the exhaust vapor of ORC while ORC can provide the power required by compressor in ACRC. The exhaust vapor of ORC and the solution of ACRC exchange heat by mixing directly in desorber to reduce heat loss. R1234ze(E) and R1234yf are used as the working fluid of ORC while R1234ze(E)/[HMIM][Tf2N] and R1234yf/[HMIM][Tf2N] are used as the working pair of ACRC. Analyzed results show that the new system has better thermodynamic performance than original ORC. Performance Analysis of Low-temperature Organic Rankine Cycle Using HFO Working Fluids and Single Screw Expander Xinxin Zhang, Yin Zhang, Min Cao, Jingfu Wang, Yuting Wu, Chongfang Ma Abstract: The organic Rankine cycle(ORC) is a popular technology used in waste heat recovery and medium-low-temperature heat utilization. In the field of low-temperature heat utilization, the net work output and thermal efficiency are two critical evaluation indicators of ORC system due to the low grade of heat source. Nowadays, as environmentally friendly working fluids, hydrofluoroolefins (HFOs) have attracted more and more attention. Moreover, as a novel expander, single-screw expander also becomes research focus. Compared with other type expander, one of the advantages of single-screw configuration is that it can conduct a vapour-liquid wet expansion. In order to use this advantage, an ORC using single-screw expander and R1234yf and R1234ze, two popular HFO working fluids, was established. Net work output is the critical evaluation indicator for open type heat source. While thermal efficiency is the one for closed type heat source. Heat exchange load of condenser is the critical indicator for calculating the cost of condenser that greatly influences the cost and economic performance of entire ORC system. Therefore, three indicators, namely net work output, themal efficiency, and heat exchange load of expander, were used to analyze the performance of an ORC system using HFO working fluid and single-screw expander. Through calculation and analysis, it can be seen that compared with the traditional cycle process, the ORC system which uses single-screw expander and undergoes a vapour-liquid wet expansion can obtain a higher thermal efficiency, more net work output, and smaller heat exchange load of condenser. Design of an Experimental ORC Expander Setup Using Natural Working Fluids Ángel Á. Pardiñas, Marcin Pilarczyk, Lars O. Nord, Roberto Agromayor Abstract: Organic Rankine Cycles (ORCs) are a potential solution to recover energy and generate power from surplus heat that different industries, such as metal production and the oil and gas industry in Norway, are currently releasing to the ambient. The industries are often in remote locations, which complicates direct use of the heat. The expander is a crucial component in any ORC system since it transforms the energy of the working fluid into shaft power. This potential for waste heat recovery, combined with the future restrictions on some of the fluids normally used in these units, justify the need for further research on ORC expanders using natural working fluids, such as hydrocarbons. To the knowledge of the authors, there is no experimental data available in the open literature for flows involving natural working fluids and operating conditions representative of ORC expanders. As a result, the fluid dynamic design methodologies used for ORC expanders often rely on tools that have not been validated. In response to this lack of experimental data, a test rig to characterize the performance of expanders in the 100 kW range will be designed and built at NTNU. This unit, named Expander Test Rig, is a part of the infrastructure project HighEFF-Lab, sponsored by The Research Council of Norway. In this work, the design of the Expander Test Rig is presented. The experimental setup design aims to be flexible enough to study the performance of both turbo- and volumetric expanders operating with different natural working fluids and their mixtures, at various operating conditions. To cover a range of operating conditions relevant for industrial applications, the test rig was designed for electrical power outputs between 30 and 50 kW, pressure ratios ranging from 2 to 8 and static temperatures at the inlet from 100 °C to 150 °C. In addition, the unit was designed to operate in the gas phase only to reduce the heating and cooling needs as well as the charge of working fluid, which is particularly important with hydrocarbons, the family of substances targeted in the design. A tailor-made, single-stage axial turbine operating with isobutane (R600a) was selected as the starting expander configuration. Performance and Exergy Analysis of Transcritical Organic Rankine Cycle Associated with Mixture Working Fluids Jui Ching Hsieh, Ding Xuan Huang, Ling Yu Kong Abstract: The low-enthalpy heat in geothermal fluids is extracted by using a binary cycle and is converted into electricity. Conventional ORCs are used widely in low-enthalpy geothermal power plants as an effective solution to convert low-grade heat into power. However, conventional ORCs are characterized by high exergy destruction during heat transfer in the evaporator and condenser. The isothermal evaporation destruction and exergy loss of the heat source can be reduced by employing transcritical organic Rankine cycles (TRCs) to generate more electricity. In the present study, a thermodynamic analysis of the mixtures R245fa/R134a, R245fa/R1234yf and R245fa/R290 associated with TRC was conducted to investigate effects of the inlet pressures of expander on irreversibility, first law efficiency, and specific power. The mixtures were examined at the heat source temperature ranging from 160 to 210 ℃. Meanwhile, the inlet pressures of expander for R245fa/R134a, R245fa/R1234yf were ranged from 4 to 8 MPa, and R245fa/R290 was ranged from 5 to 9 MPa, respectively. In the present study, the first thermodynamic efficiency of the mixtures was significantly affected by the inlet temperatures and the inlet pressures of expander, especially at higher inlet temperature and pressure. However, the specific power was slightly increased with the inlet pressures of the expander. Finally, a maximum themal efficiency and specific power corresponding to a optimal pressure were observed at each inlet temperature due to the evaporate and condense irreversibility and, pmp and expander irreversibility decreased and increased with the inlet pressure, respectively. Analysis of Organic Rankine Cycles Using HFC and HC-based Zeotropic Mixtures under Different Heat Source Temperatures Jui Ching Hsieh, Chung Cheng Yeh, Hsuah Cheng Liu, Wen Chieh Wu, Wei Hung Shih Abstract: Owing to growing industrialization, the energy consumption has increased considerably over the past few decades, which has led as acid rain, ozone layer depletion, and global warming. Most industries exhaust a lot of low-grade heat to environment, especially as temperature below 100 ℃. For low-grade heat, ORC (organic Rankine cycle) is one of effective methods for conversion of low-grade heat into electricity. Conversion efficiency of ORC is significantly affected by the temperature difference between heating and cooling source, and working fluids. Actually, working fluids cause great damage on the environment, especially for high global warming potential (GWP). Hydro-fluorocarbon (HFC) refrigerants, which have high GWP, but they are popular working fluids owing to excellent conversion efficiency in low-grade heat. By contrast, hydro-carbon (HC) refrigerants have low GWP and high flammability, and they’re suitable in high and medium temperature of the heat source. To achieve high conversion efficiency of system and low GWP of working fluids, HFCs and HCs could be mixed to use as working fluid in ORC system. The purpose of the present study was to develop a thermodynamic analysis model by using MATLAB and to investigate performance of the mixtures at heat source temperature ranging from 100 to 210 ℃. Meanwhile, the evaporate temperatures was set at 70℃. In the present study, R290, R134a and R1234yf with low critical temperature were mixed with R245fa and R600a with high critical temperature to investigate effect of the inlet temperature of the heat source on the optimal mole fraction, change of the evaporate pinch point, first law efficiency of thermodynamic and specific power. Experimental Study on the Expansion Ratio of Single Screw Expanders under Variable Working Conditions Wei Wang, Yuting Wu, Chongfang Ma Abstract: In the recovery utilization of medium and low temperature waste heat, the organic Rankine cycle(ORC) is regarded as the most potential technique. The expander plays an important role as the output power equipment of the ORC, and the single screw expander has a great prospect due to its unique structure and working characteristics. In addition to the expander efficiency, the expansion ratio is another important performance parameter of the expander, which has a great influence on the thermal efficiency of the ORC system. Based on the experimental study of the single screw expander in this laboratory, the change of the internal and external expansion ratio of single screw expander is analyzed. The experimental results show that the expansion ratio increases with the increase of rotational speed, and the external expansion ratio decreases gradually. The internal and external expansion ratio of single screw expander increases with the increase of inlet pressure. When the inlet pressure interval is 0.4~0.65 MPa, the external expansion ratio is 3.26~ 3.73, and the internal expansion ratio is 4.8~ 8.0. It can be found that the effects of internal expansion ratio of single screw expander on the working condition lager than external expansion ratio, while the latter is affected by the back pressure, but the variation is small. Study on a Recompression Supercritical CO2 Brayton Cycle for a Solar Power Tower System under off-design Conditions Jingze Yang, Zhen Yang, Yuanyuan Duan Abstract: Concentrated solar power (CSP) with thermal energy storage (TES) is a promising technology to provide a dispatchable power output. When it is used for peak load shaving in the power grid, the system runs under operating conditions deviating from the design point (off-design conditions). Among several CSP technologies, solar power tower (SPT) integrated with the supercritical CO2 (S-CO2) Brayton cycle attracts extensive attention for high efficiency. Recompression S-CO2 Brayton cycle with high-temperature and low-temperature recuperators is proposed to decrease the irreversible loss of heat transfer, compared with using a single recuperator, and thus to achieve a preferable thermodynamic performance. Therefore, to meet the variable power demand with possibly higher thermal efficiency, the performance of recompression S-CO2 Brayton cycle under off-design conditions is necessary to be well understood. However, relevant researches on this aspect are rarely reported. In this study, a power system of the recompression S-CO2 Brayton cycle with reheating integrated with the SPT is proposed. Under off-design conditions, sliding pressure operation control strategy is adopted for the power cycle with variable load. The molten salt temperature at the inlet of heater remains constant, whereas the mass flow rate is adjusted to deliver the requested heat to the power cycle. The operating parameters including split ratio and intermediate pressure for reheating are optimized for variable off-design conditions. The results show that the cycle thermal efficiency decreases as the load decreases. The optimal split ratio and intermediate pressure for reheating change for different off-design conditions. Experimental Study on the Influence of Heat Exchanger on the Organic Rankine Cycle Performance Yingzong Liang, Xianglong Luo, Xiaosheng Zheng, Jianyong Chen, Zhi Yang, Ying Chen Abstract: Organic Rankine cycle (ORC) is a common accepted low-grade heat-to-power technology. Although the ORC has been extensively investigated in the past decades, experimentally validated works occupy only a small fraction of published literature. The experimental test rig in most of the previous studies are mostly focus on the expander, cycle configuration, working fluid, and system performance. The experimental investigation on the heat exchanger is quite limited though the heat exchanger occupies important role in investments cost and irreversible loss. In the present study, a novel ORC experimental test rig with switchable heat exchangers and scroll expander is introduced. The steady test is first conducted. Then, the influence of working fluid flowrate from 0.1kg/s to 0.16kg/s on the cycle performance is conducted for ORC1 with 6.56m2 evaporator and 13.59m2 under design conditions. Next, the component and cycle performances are investigated under different heat source temperature range from 120oC to 140oC and heat sink temperature range from 15 oC to 25 oC. Finally, the system performance test and comparison are conducted for six ORCs with different heat exchanger area, namely ORC1, ORC2 with 6.56m2 evaporator and 10 m2, ORC3 with 6.56m2 evaporator and 5.42m2, ORC4 with 3.71m2 evaporator and 13.59m2, ORC5 with 3.71m2 evaporator and 10 m2, ORC6 with 5.42m2 evaporator and 13.59 m2. Results show that the thermal efficiency of ORC first increases then decreases with working fluid mass flowrate for ORC1 under design heat source/sink conditions. The thermal efficiency of ORC increases with the inlet temperature difference of heat source and heat sink. ORC2 features the maximum thermal efficiency at working fluid flow rate 0.12kg/s, heat source temperature 150oC, and heat sink temperature 15oC. The comparison between different ORCs show that the condenser area is large than assumed and the pinch point temperature difference is very small in most of the studied operating conditions. The results show that the ORC performance is remarkably affected by the heat exchanger size and the present experimental study provide a valuable guidance for the reasonable heat exchanger design and to improve the ORC performance. Experimental Investigation and Performance Assessment of Scroll Expanders in Series Configuration of a Small Scale Two-stage ORC Unit Dimitris Manolakos, George Kosmadakis, Erika Ntavou, Bertrand Tchanche, George Papadakis Abstract: The paper presents the results of performance assessment of scroll expanders integrated into a two-stage ORC unit supplied with heat from vacuum tubes solar collectors at a temperature around 130 oC. The system under investigation uses R245fa as working fluid and two scroll expanders (hermetic scroll compressors in reverse operation) connected in series. The system is designed so as to obtain optimal performance as that indicated by the variation of the heat source temperature, ranging between 95-130 oC, respecting to a pressure ratio in the order of 10 and given that each scroll expander pressure ratio is in the order of 3, similar to its built-in volume ratio. Effects of temperature variation are investigated to predict the performance of system driven by intermittent solar heat, where partial load operation prevails. In the two scrolls connected in series, the outlet of the first expander defines the inlet conditions of the second expander, thus strongly affecting its performance. During laboratory tests under controlled conditions, the ORC system was supplied with a mixture of hot water and glycol from using an electric heater of 100 kWth capacity with variable heat flow and temperature, while the total (maximum) expansion work is ~10 kWel. Under this variation of the heat source temperature, the key operational parameters of the two expanders were calculated (i.e. pressure and volume ratio, filling factor) to reveal their interrelation and influence on the expanders’ performance, with direct effect on the cycle performance as well. Expanders showed isentropic efficiency as higher as 60% for the first expander and 80% for the second. Design Guidelines for Axial Turbines Operating with Non-ideal Compressible Flows Andrea Giuffre', Matteo Pini Abstract: Preliminary design methods based on similarity theory. i.e. the Smith’s chart, are a powerful and well-established tool to provide estimate of the size, the shape of the velocity triangles, and the fluid-dynamic performance of gas turbine stages. However, such criteria are arguably not suitable for the design of turbomachines operating with highly complex molecules that exhibit non-ideal fluid dynamic behaviour. In these machines, the departure of the flow from the ideal gas law can significantly alter the amount of dissipation induced by the various loss mechanisms, which may eventually result in shifts of the optimal design region. Currently, physical comprehension of loss mechanisms in these turbines is mainly revealed through computational fluid-dynamic studies, which are indeed machine-specific and cannot be used to draw best design practices. On the other hand, the existing body of work [1] on design guidelines using meanline methods rely on semi-empirical loss correlations and lacks of thorough validation using higher-fidelity models. This work aims to bridge this gap by proposing a meanline design procedure based on scaling analysis and coupled to a first principles loss model [2] extended to arbitrary fluid thermo-physical models. The developed model is used to investigate the performance trends of axial turbine stages operating with fluids of increasing molecular complexity (CO2 and MM) and operating in the ideal and non-ideal thermodynamic region. The specific objectives are i) to draw improved design guidelines and performance maps valid for axial turbines, ii) to gain insight of the main loss mechanisms in these stages, and iii) to provide physical understanding behind such loss mechanisms. The outcomes of the study suggest that the so-called Smith line, i.e. the locus of the optimal duty coefficients, is function of the fluid molecule and the turbine expansion ratio. An increase of the expansion ratio directly translates into stronger shocks-induced losses, associated with higher Mach numbers along the stage. Molecular complexity mainly affects dissipation due to mixing, e.g. trailing edge wake and leakage flow, shifting the region of optimal performance towards lower flow coefficients. 3D RANS CFD calculations are finally used to verify the predicted trends. The results corroborate the findings based on scaling analysis, paving the way to best design practices for single and multi-stage axial turbines operating with non-ideal compressible flows. IMPACT of ORC Micro-turbine Flowpath Optimisation on the off-design Performance Łukasz Witanowski, Piotr Klonowicz, Piotr Lampart Abstract: The optimisation of power systems enables their efficiency to be increased, with a consequent increase in the mechanical and electric power generated by the components. For ORC systems, in which cycle efficiency is relatively low (up to 30%)[1–4], designing a high efficiency system increases the competitiveness of the entire undertaking. In this article, a single-criterion rotor geometry optimisation method is presented for a 10 kWe axial micro-turbine operating in an ORC system. Calculations were performed using deterministic, stochastic and hybrid algorithms. Isentropic efficiency was defined as the objective function. Single channel calculations were performed using a Matlab application and commercial simulation code. This paper presents a rotor blade, hub and shroud shapes parametrisation method. The quantitative and qualitative results are listed for the optimisation algorithms used. Micro-turbine characteristic measurements were determined. A micro-turbine operation analysis was conducted under off-design conditions, before and after optimisation. As a result of the optimisation process, micro-turbine efficiency was increased and the types of losses showing the most impact on geometric improvement were identified. [1] Turboden S.p.A., www.turboden.com. [2] B.F. Tchanche, G. Lambrinos, A. Frangoudakis, G. Papadakis, Low-grade heat conversion into power using organic Rankine cycles – A review of various applications, Renew. Sustain. Energy Rev. 15 (2011) 3963–3979. doi:10.1016/j.rser.2011.07.024. [3] S. Quoilin, M. Van Den Broek, S. Declaye, P. Dewallef, V. Lemort, Techno-economic survey of Organic Rankine Cycle (ORC) systems, Renew. Sustain. Energy Rev. 22 (2013) 168–186. doi:10.1016/j.rser.2013.01.028. [4] T.Z. Kaczmarczyk, G. Żywica, E. Ihnatowicz, The impact of changes in the geometry of a radial microturbine stage on the efficiency of the micro CHP plant based on ORC, Energy. 137 (2017) 530–543. doi:10.1016/j.energy.2017.05.166. THERMODYNAMIC, Economic and Environmental Multi-objective Optimization of ORC under Varying Weight Hu Shuozhuo, Li Jian, Yang Fubin, Duan Yuanyuan, Yang Zhen Abstract: Organic Rankine cycle (ORC) is an effective, simple and environmental friendly technology to make use of waste heat or renewable energy such as solar energy, geothermal energy and biomass. With the research on ORC develops, the optimization method gradually turns from single-objective optimization to multi-objective optimization (MOO). Thermodynamic, economic and environmental performance are key indicators to evaluate the ORC system. Recently there are mainly two ways to comprehensively optimize an ORC system such as (1) transform multiple objectives into single objective based on linear weighting method. (2) optimize several objectives simultaneously using multi-objective optimization algorithm. However, most researches optimize the ORC system under a fixed weight of objective and pays little attention to the effects of weight on parameter design and fluid selection. Actually objective weight directly affects the final optimal solution in decision-making progress and thus affects the system parameters and selection of working fluid. This study focus on the effects of various weights on the system design and optimization. Three indexes as levelized energy cost (LEC), exergy efficiency, and carbon dioxide emission reduction (CER) are selected as system evaluation indicators with a heat source of 100 ℃, in which CER is calculated by the Life Cycle Climate Performance (LCCP) method. Three working fluids as R1234yf, R290, and R134a are calculated and compared using Non-dominated Sorting Genetic Algorithm II (NSGA-II) algorithm. A multi-criteria decision making (MCDM) method applies in selecting from the Pareto frontier when weights of three objectives vary from 0 to 1 increasing by 0.05. The selection of working fluid and system parameters is discussed under all weights. The results show that R134a exhibits the best thermodynamic performance but the worst environmental performance. R1234yf is the optimum fluid when weight of CER is over 0.25 while R134a is optimal when weight of CER is under 0.2. In terms of system parameter, evaporation temperature and superheat degree are the most two sensitive parameters while pinch point temperature difference and heat sink outlet temperature are least sensitive to weight of CER and LEC since they are the minimum under all weights. This study firstly analyses the effects of objective weight on the system parameters and working fluid selection quantitatively using MOO and MCDM method. Which facilitates the comprehensive optimization of ORC system in future. Integrating Working Fluid Design into Dynamic ORC Process Design for Mobile ORC Applications Dominik Tillmanns, Jonas Petzschmann, Johannes Schilling, Christoph Gertig, André Bardow Abstract: Organic Rankine Cycles (ORC) generate power from low temperature heat sources. To maximize the generated power, both the ORC working fluid and process have to be tailored to the specific application. The resulting integrated design problem for ORC working fluid and process has been studied intensively for steady-state applications [1,2]. However, recently, ORCs are increasingly used in applications with transient conditions such as exhaust gas waste-heat recovery on heavy-duty vehicles [3]. For such transient applications, steady-state design approaches can result in suboptimal solutions due to the neglect of the dynamic process behavior. In this work, we integrate working fluid design into ORC process design while considering the dynamic process behavior in transient applications. The resulting integrated design approach is based on the Continuous-Molecular Targeting−Computer-aided Molecular Design (CoMT-CAMD) framework [2,4]. Herein, the physically-based Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) [5] is used to calculate the thermodynamic properties of the working fluid. In PC-SAFT, a working fluid is characterized by pure component parameters, which are directly considered as degree of freedom during process optimization in CoMT-CAMD. So far, CoMT-CAMD has been limited to one steady-state design point. To consider transient applications, dynamic models for the ORC equipment are integrated into the CoMT-CAMD formulation resulting in a dynamic mixed-integer optimal control problem. For a given transient input, the resulting dynamic CoMT-CAMD approach provides the optimal working fluid and the corresponding optimal design and control of the ORC process. The resulting dynamic CoMT-CAMD approach is applied to tailor an ORC for waste-heat recovery on a heavy-duty vehicle. Dynamic CoMT-CAMD reliably identifies the optimal working fluid jointly with the optimally controlled ORC process that best exploit the transient exhaust gas of heavy-duty vehicles. Acknowledgements We thank the Deutsche Forschungsgemeinschaft (DFG) for funding this work (BA2884/4-2). References [1] White et al., Energy Convers. Manage. 150, 2017, 851-869. [2] Lampe et al., Comp. & Chem. Eng. 81, 2015, 278-287. [3] Eichler et al., SAE Int. J. Commer. Veh. 8, 2015, 491-505. [4] Schilling et al., Mol. Syst. Des. Eng., 2, 2017, 301-320. [5] Gross and Sadowski, Ind. Eng. Chem. Res. 40, 2001, 1244-1260. Investigation of a topping/bottoming ORC Based CHP Configuration Integrating a New Evaporator Concept for Residential Applications João S Pereira, José B Ribeiro, Ricardo Mendes, Jorge C André Abstract: The recommended design principles for the development of evaporators for ORC based micro-CHP systems attempting to retrofit the current combi-boilers are presented and discussed in this paper. From those principles, among which is the need of organic fluid direct vaporization, emerged a hybrid (topping/bottoming) CHP configuration in which the thermal energy is produced stepwise: firstly in the ORC-condenser and then in a post-heater, that is integrated on the ORC-evaporator, directly with the combustion gases. A model of this configuration was developed to determine the fraction of the CHP water heating process performed in the post-heater that maximizes the primary energy savings and ORC net power output for a wide range of CHP operating conditions. When compared to a standard CHP configuration, this solution show benefits for the greater part of those conditions. Besides solving the safety issue posed by the ORC-evaporator requirements and the performance benefits shown, this configuration has an additional positive side effect: the decrease of the combustion gases’ temperature before they reach the organic working fluid heat-exchanger section in the ORC-evaporator that leads to a reduction of the risk of the working fluid thermal degradation. The Analysis on Powering the ORC (Organic Rankine Cycle) System by Heat Storage Device Piotr Kolasiński Abstract: Some of the heat sources, such as e.g. waste or solar, are featuring floating thermal and output characteristics. Heat recovery from such sources is difficult while the changes in the heat source output and heat carrier temperature negatively influences the continuity and operational conditions of energy conversion systems and devices. Especially vapour power plants, such as ORCs, should utilize the heat sources having steady thermal and output characteristics. The heat source floating characteristics can be stabilized using the heat storage devices providing the thermal energy accumulation at stable output and temperature level. Heat storage device can be adopted as a steady-level heat source for ORC system. In this paper the results of the experiments carried on the ORC system powering from heat storage system, which were carried out on a prototype ORC test-stand are presented. The results showed that adopting the heat storage devices for powering the ORC systems is a promising way of utilizing the floating waste and solar heat sources. Analysis of Low Global Warming Potential Alternatives to HFC-245fa in Micro Scale Low Temperature Organic Rankine Cycles Francisco Molés, Joaquín Navarro-Esbrí, Marta Amat-Albuixech, Adrián Mota-Babiloni, Carlos Mateu-Royo, Roberto Collado Abstract: The Organic Rankine Cycle is a power cycle for the valorization of low-temperature heat sources, being similar to a conventional Rankine cycle, but using an organic working fluid instead of water. Focusing on micro-scale low-temperature applications up to 100ºC, HFC-245fa and R134a are the most common working fluids, which stands out for its suitable thermodynamic and security properties. Nevertheless, due to new legislations, finding a low global warming potential working fluid is becoming increasingly necessary. New HFOs and HCFOs have been recently presented as potential low GWP alternatives for their use in low-temperature micro-scale ORC technology. The purpose of the present study is to analyze the behavior of these low-GWP substitutes in typical configurations, basic cycle and regenerative cycle, under generation and cogeneration operating conditions. The different working fluids will be tested in a theoretical model, which has been computed taking as a reference real installation with similar features. Finally, the main conclusions about the main strategies in order to design a new installation or to face a drop-in replacement with these low GWP working fluids are commented. Component Testing and Integration of a Plug and Play sCO2 Power Generation System Romain Loeb, Giuseppe Bianchi, Samira Sayad Saravi, Arthur Leroux, Savvas A. Tassou Abstract: The supercritical carbon dioxide (sCO2) heat to power generation cycle is the subject of increasing academic and industry research. Based on its high energetic density and compressibility, the thermodynamic efficiency at high heat source temperatures of the sCO2 power cycle promises to be higher than conventional Rankine cycles currently available on the market. While most projects are targeting large power plants - such as coal, solar and nuclear of MW power output capacity, the sCO2 system being developed under the H2020 I-ThERM project has been designed for Plug-&-Play distributed power generation applications primarily from waste heat sources. A compact 50 kWe integrated solution within a mobile container aims to be adaptable to various Waste Heat Recovery (WHR) and operating conditions. Such applications include iron & steel, chemical processes, cement and glass manufacturing as well as other highly energy intensive industries. All these industries can benefit from this high temperature heat to power conversion technology being developed in this project. The turbo-machinery is a single shaft Compressor Generator and Turbine (CGT) system. After successful fabrication and description of initial rotational tests using air as the working fluid, this paper will focus on the integration phase of the CGT with the rest of the components of the sCO2 cycle. This step brings some technical challenges. First, high pressure testing to comply with the Pressure Equipment Directive (PED) are undertaken. These are followed by the selection and integration of sensors, automation controls and by component assembly. The thermodynamic cycle is designed for sCO2 pressures up to 127 bar and temperatures up to 400 °C. To test the system at these conditions, a High Temperature Heat To power Conversion facility (HT2C) has been designed and is being built at Brunel University London, UK. The paper will discuss these facilities and their integration to enable the testing and evaluation of the sCO2 system over a wide range of operating conditions. The results will enable design and control optimisation of the system and will lead to further development of individual components and the overall system towards commercialisation. Optimal Mixtures for Organic Rankine Cycles: Integrated Design of Process and Mixture Using PC-saft Johannes Schilling, Marten Entrup, Madlen Hopp, Joachim Gross, André Bardow Abstract: Organic Rankine Cycles (ORC) generate electrical power from low-temperature heat. To exploit the full potential of ORCs, an integrated design of ORC process and working fluid is required. Today, methods for an integrated design are commonly limited to the design of pure working fluids [1]. However, mixtures can improve the ORC efficiency significantly due to favourable thermodynamic properties [2]. In this work, we present a method for the integrated design of ORC process and working fluid mixtures based on the 1-stage Continuous-Molecular Targeting – Computer-Aided Molecular Design (1-stage CoMT-CAMD) method [3]. In 1-stage CoMT-CAMD, the thermodynamic properties are modelled using the physically-based PC-SAFT equation of state. A computer-aided molecular design (CAMD) formulation enables us to consider the molecular structure as degree of freedom during process optimization. Detailed models for equipment sizing allow the optimization of an economic objective. The resulting mixed-integer nonlinear program (MINLP) optimization problem identifies the optimal working fluid jointly with the optimal process conditions and equipment. However, so far, 1-stage CoMT-CAMD was limited to the design of pure working fluids. In this work, we extend the CAMD formulation, the process model as well as the models for equipment sizing to consider a working fluid mixture as degree of freedom of the MINLP. Thereby, the optimal working fluid mixture is identified in a single optimization problem jointly with the corresponding optimal process and equipment. The resulting approach is applied for the design of an ORC for waste heat recovery. The integrated design of ORC process and working fluid mixture is performed considering thermodynamic as well as thermo-economic objective functions. The presented method allows us to systematically exploit the potential of working fluid mixtures for ORCs. Acknowledgements We thank the Deutsche Forschungsgemeinschaft (DFG) for funding this work (BA2884/4-2). [1] Angelino, G., Colonna, P. (1998). Multicomponent Working Fluids for Organic Rankine Cycles (ORCs). Energy, 23(6), 449–463. [2] Papadopoulos, A. I., Tsivintzelis, I., Linke, P., Seferlis, P. (2018). Computer-Aided Molecular Design: Fundamentals, Methods, and Applications. Reference Module in Chemistry, Molecular Sciences and Chemical Engineering, Elsevier. https://doi.org/10.1016/B978-0-12-409547-2.14342-2.0 [3] Schilling, J., Tillmanns, D., Lampe, M., Hopp, M., Gross, J., Bardow, A. (2017). From molecules to dollars: integrating molecular design into thermo-economic process design using consistent thermodynamic modeling. Mol. Sys. Des. Eng., 2(3), 301-320. Towards Superstructure-based Design of ORC processes, Working Fluids and Process Flowsheets Using PC-saft Johannes Schilling, Christian Horend, Dominik Tillmanns, André Bardow Abstract: Organic Rankine Cycles (ORC) transform low-temperature heat into electrical power. To best exploit the heat input, several methods have been proposed that integrate the design of ORC processes and working fluids [1]. Beside the process conditions and the working fluid, the optimal process flowsheet is essential, e.g., the optional usage of a heat exchanger for regeneration or steam bleeding in the turbine. However, the process flowsheet is commonly analysed only for a set of preselected working fluids. If the preselection fails, solutions will be suboptimal. To obtain overall optimal combinations of process conditions, working fluid and process flowsheet, the design of the process flowsheet has to be integrated into the process and working fluid design. In this work, we present a method for the integrated design of ORC processes, working fluids and process flowsheets. The presented method is based on the 1-stage Continuous-Molecular Targeting – Computer-Aided Molecular Design method (1-stage CoMT-CAMD) [2]. In 1-stage CoMT-CAMD the PC-SAFT equation of state is used as physically-based thermodynamic model for both, equilibrium and transport properties. So far, 1-stage CoMT-CAMD was limited to the integrated thermo-economic design of process and working fluid based on the a priori definition of the process flowsheet. Here, we extend the method by a superstructure for the ORC flowsheet. Within the ORC superstructure, optional configurations for regeneration, reheating and turbine bleeding are considered. Thereby, the ORC process flowsheet can be directly considered as degree of freedom within 1-stage CoMT-CAMD using binary structural variables. For ease of use, the method is implemented in the process flowsheeting software gPROMS [3]. The resulting method is demonstrated for the design of a subcritical ORC for waste heat recovery. The integrated design is performed considering thermo-economic as well as thermodynamic objective functions. The result of the extended 1-stage CoMT-CAMD is an optimal combination of the ORC process conditions, working fluid and process flowsheet. Acknowledgements We thank the Deutsche Forschungsgemeinschaft (DFG) for funding this work (BA2884/4-2). [1] Papadopoulos, A. I., Tsivintzelis, I., Linke, P., Seferlis, P. (2018). Computer-Aided Molecular Design: Fundamentals, Methods, and Applications. Reference Module in Chemistry, Molecular Sciences and Chemical Engineering, Elsevier. https://doi.org/10.1016/B978-0-12-409547-2.14342-2. [2] Schilling, J., Tillmanns, D., Lampe, M., Hopp, M., Gross, J., Bardow, A. (2017). From molecules to dollars: integrating molecular design into thermo-economic process design using consistent thermodynamic modeling. Mol. Sys. Des. Eng., 2(3), 301-320. [3] Process Systems Enterprise. gPROMS. 1997-2018. Available at: www.psenterprise.com Influence of the Partial Admission and Blade Aspect Ratio on an ORC Turbine Performance Władysław Kryłłowicz, Grzegorz Górecki, Piotr Klonowicz, Łukasz Antczak, Krzysztof Kantyka Abstract: The paper describes the experimental and numerical results of a single stage impulse turbine which is a part of a hermetic turbogenerator working with HFE 7100 fluid. The device is a component of a hybrid micro power plant consisting of two sub-cycles: high temperature steam cycle and an ORC bottoming cycle. The experimental tests included the turbines with two admission sizes: ε = 0.25 and ε = 0.5. For each admission size different blade heights were tested. For the selected geometrical cases steady-state RANS simulations have been performed in which the real gas equations of state has been applied in form of a look-up table. The influence of the blade height (aspect ratio) and the tip clearance on the stage losses was investigated. The results have been compared with the selected empirical loss models as well as with the obtained experimental results. Determining the Heat Transfer Characteristics of R125 at Supercritical Pressures Marija Lazova, Steven Lecompte, Michael de Paepe Abstract: Heat exchangers are components of high importance for the proper operation of the organic Rankine cycles (ORC’s). Furthermore, the efficiency of the trans-critical ORC’s can be improved by acquiring supercritical heat transfer in the heat exchanger at the hot side. However, heat transfer correlations for designing heat exchangers suitable to operate under these conditions are lacking. Therefore, heat transfer experiments at supercritical state of the working fluid R125 were conducted on the novel test set-up. The test section is a tube-in-tube heat exchanger with a diameter of the inner tube of 28.6mm and is horizontally positioned. Experiments were conducted at various mass fluxes and the pressure was in the range of 1.05 Simultaneous Working Medium Selection, Process and Control System Design for Organic Rankine Cycles Theodoros Zarogiannis, Alexios Kyriakides, Athanasios Papadopoulos, Panos Seferlis, Spyros Voutetakis Abstract: The present work addresses the integrated ORC process design and control for a set of potentially promising working media under a unified framework. The proposed work aims to investigate the optimal combination of the working mixture with the ORC configuration that satisfy an economic criterion under steady-state and closed loop conditions. Therefore, for a selected working mixture the steady-state design of the ORC is performed based on economic optimization, where the optimal configuration and sizing of the equipment is obtained. In addition, a set of disturbance scenarios is constructed that are representative of the most commonly occurring operating conditions for the process. A model predictive control (MPC) scheme is employed for the satisfaction of the process goals under process variability and disturbance influence. The use of a MPC enables the best handling of the interactions among the various processes in the cyclic process. The integrated design framework enables the determination of the most suitable input-output structure for the controller by allowing the selection of the controlled and manipulated variables from a pool of screened options. The performance of the MPC under the specified disturbance scenarios is calculated through dynamic simulations for the selected working medium and process flowsheet configuration, in each optimization iteration. The dynamic performance is converted to an economic equivalent term so that it can be combined with the steady-state design economic term to generate the overall objective function value. Novel and conventional hydrocarbon- and halogenated hydrocarbon-based mixtures are considered for the integrated ORC process and control system design under the proposed unified framework. Variation in the hot and cold source streams is considered in the system where the employed MPC aims to maintain the evaporator temperature at the desired level and achieve the maximum work in the expander. The simultaneous problem of working mixture selection and process design under static and closed loop conditions is solved using a stochastic optimization technique. The results provide significant insights in the behavior of the ORC system under closed loop conditions. The ability of the ORC system with the MPC to maintain a high performance under variability is found to be influenced by the sensitivity of the working medium physical properties within the range of variation that is transferred through the system. Mass Flow Rate of Non-ideal Chocked Flows in Turbine Stators Marta Zocca, Alberto Guardone Abstract: The maximum mass flow rate a supersonic turbine stator can discharge is limited by the occurrence of chocked flow conditions at the stator throat. When a turbine is operated away from the design point, the sonic conditions attained at the stator throat change accordingly, and deviations from the design mass flow rate are observed. In this work, non-ideal chocked flows are studied and the dependence of sonic conditions on the total thermodynamic state is thoroughly discussed. Analytical correlations between the sonic and total thermodynamic variables are derived. The correlations highlight an explicit dependence of the sonic variables on the value attained by the fundamental derivative of gasdynamics Γ along the expansion from reservoir to sonic conditions. For a perfect gas, the value of Γ is constant and depends only on the fluid characteristics, regardless of process conditions. For non-ideal flows instead, Γ depends on the total thermodynamic state and shows a significant variation along the expansion. As a result, sonic and total thermodynamic properties are not in a relation of proportionality, contrary to the well-known behaviour of perfect gas flows. The present findings are confirmed by state-of-the-art thermodynamic models applied to selected commercially available fluids for ORC applications. The sonic momentum density is computed for a wide range of operating conditions and maps are reported, which provide the sonic momentum density as function of the total pressure and temperature. Numerical simulations of supersonic expansions in exemplary converging-diverging geometries further confirm the predicted trends. Modeling and Experimental Analysis of a Tesla Turbine for Waste Heat Recovery from Screw Air Compressors Luca Da Lio, Mattia Piazza, Giovanni Manente Abstract: The recovery of low-grade waste heat from industrial processes asks for efficient and cost-effective solutions for both power cycle and equipment. While the organic Rankine cycle (ORC) is universally recognized as the most suitable power cycle for these applications, multiple options are available for the expander especially at small sizes (few kW to tens kW) where piston, scroll, screw expanders, etc., as well as radial inflow and partial admission axial flow turbines are found. Among them, the Tesla turbine has attracted much attention in the last decade due to the possibility of achieving a moderate efficiency with a simple and robust design. This work is about the one-dimensional analysis, development of a test-rig and first experimental results obtained for a Tesla turbine operating with air and organic fluids. The one-dimensional analysis of the rotor is based on the simplification by a systematic order of magnitude analysis of the momentum equation proposed by Carey [1] and extended by Manfrida [2] to relax the assumption of constant density and using real gas properties. The turbine model is embedded in the overall model of the ORC system in the search of a global optimization. The test-rig is built within a cutting-edge company in northeast Italy willing to apply the ORC technology with Tesla turbine for heat recovery from their series of screw air compressors having outlet temperature of 95°C and recoverable thermal power in the range 20-170 kWt. The manufactured turbine has disks with an outer diameter of 0.225 m and an inner diameter of 0.076 m, and a convergent-divergent nozzle to allow for supersonic flow at rotor inlet. The first experimental tests on the Tesla turbine prototype conducted until now using compressed air at different pressures have provided useful indications to solve practical issues related to the leakage of air flow, improve the turbine efficiency and extend the operation to organic fluids. The outcome of the forthcoming experimental tests with enhanced equipment and using R134a will provide additional insights about the optimum operation of the system and enable to assess any difference compared to operation with air. [1] Carey V.P. Assessment of Tesla Turbine Performance for Small Scale Rankine Combined Heat and Power Systems. Journal of Engineering for Gas Turbines and Power 2010;13:122301-8. [2] Manfrida G., Pacini L., Talluri L. A revised Tesla turbine concept for ORC applications. In Proc. of the IV International Seminar on ORC Power Systems (ORC2017), 13-15 September 2017, Milan, Italy. Parametric Study of Radial-inflow Turbine Design for Lower Temperature ORC Michael Deligant, Simone Braccio, Emilie Sauret, Sofiane Khelladi, Farid Bakir Abstract: Low grade heat resources can play a central role in providing new ways to produce electricity at low carbon emission rates, and alleviating the need for fossil fuels. Radial-inflow turbines are compact and efficient expanders for converting low grade heat into electricity. They have been shown to be particularly suitable in Organic Rankine Cycles (ORC) to deliver high cycle efficiencies. The availability and cost reduction of high rotational speed motor/generator allow the development of small turbines in a variety of applications from micro CHP to automotive waste heat recovery (WHR) including solar ORC. In order to provide reliable experimental data, an experimental setup has been designed based on the adaptation of a high speed spindle with a maximum power of 9 kW and a maximum rotational speed of 60,000 rpm. In this study, we considered SES36 as working fluid with fixed inlet pressure and temperature corresponding to a low temperature solar ORC. The design of 4 turbines is considered varying the specific speed but with the same polytropic enthalpy drop at the design point for each turbine. The specific speed is varied through the adjustment of the rotational speed and the cycle power within the limits of the considered generator, which will be used in future experiments. The turbine designs are achieved using adapted 0D/1D meanline models. The performance maps of the turbines are then computed with real gas CFD simulations. The results show the evolution of the maximum efficiency with the specific speed. The off-design behaviour of the different turbines are compared. In future work these designs will be manufactured and tested on the experimental setup providing experimental data for comparisons that will be used to validate and improve the numerical models. Evaporator Heat-transfer Model and Thermal Degradation Analysis of R245fa Used in a Direct Vaporization Arrangement ORC Based Micro-CHP system. João S Pereira, José B Ribeiro, Ricardo Mendes, Jorge C André Abstract: Combined heat and power systems (CHP) can be implemented within all power scales, even at micro-scale where the most promising target lies in the residential sector given the huge dimension of the potential market. At this scale, and for solutions attempting to retrofit wall-mounted combi-boilers, the Organic Rankine Cycle (ORC) appears to be the most promising technology because of its simplicity and available components. Among those components, the evaporator is the only one that, due to its specificities, cannot be found directly in the market or easily adapted from a mass production part of other appliances. Therefore, almost all industrial or academic researches made are implementing an intermediate circuit between the primary energy source and the ORC. One of the reasons why researchers are using this intermediate circuit, where the heat-exchanger is not directly exposed to hot combustion gases, is connected to the thermal degradation of the organic fluid. Nevertheless, besides the common design features (e.g. efficiency or safety), the residential system should also be small, safe and cheap which appears to be easier achieved using a direct vaporization arrangement. This work presents a designed ORC-evaporator that uses the high-temperature combustion gases to vaporize an organic fluid – R245fa. The direct ORC-evaporator is integrated into a real ORC based micro-CHP system to analyze the organic fluid regarding its thermal degradation. The operating conditions of the micro-CHP system do not demand higher temperatures than the ones specified in literature for R245fa thermal degradation (≈ 300 ºC). However, the heat-exchanger is submitted to hot combustion gases and so the thermal boundary layer temperature will have higher values. Nonetheless, there is also the possible occurrence of hot spots in the heat-exchanger due to trapped vapor bubbles in its inside, increasing its temperature until the chemical breaking point. Considering both questions, the goal is to recover the organic fluid after several hours of operation at the system’s maximum temperature and submitted it to a gas chromatograph analysis. Additionally, a heat-transfer model of the designed ORC-evaporator (experimentally validated) is also described to support the conclusions. Variables like thermal boundary layer temperatures and convection heat-transfer coefficients are key outputs of this model. Cloud Based Simulation of ORC Systems Erhard Perz Abstract: With the increasing interest in ORC systems, accurate thermodynamic models of the ORC systems and their integration with other systems such as geothermal plants, biomass combustion and gasification plants, solar power plants or industrial processes are of great value. They provide insight into the process details and can be used to optimize the performance of the system. However, to create such models in a traditional way, substantial locally installed resources are required. If a project is developed in a collaborative effort, the resources need to be replicated for each partner. Cloud based systems are changing the work flow in many areas and make collaboration easier and more efficiency. This paper describes a flexible cloud-based simulation platform for ORC processes, making simulation easier accessible than traditional solutions and offering options for new ways to work on projects. The platform presented allows to create, configure and solve ORC process models in the cloud. All interaction with the model, from defining the model to reporting results, is done via a web browser. It is not necessary to install any software locally. Taking advantage of recent developments in browser technology, in particular HTML5, a browser-based user interface has been developed. It can be used with the current versions of any of the major web browsers. The user interface allows to set up and configure the process model graphically based on predefined component. It is used to specify process parameters and to display simulation results. In this way, the system represents a complete Software as a Service (SaaS) solution. The underlying architecture of the system is presented. The paper presents results obtained for various examples of ORC processes. It explains the capabilities of the platform and discusses benefits and risks of the cloud-based approach. The work presented has been developed with partial funding received from the European Union's Horizon 2020 research and innovation programme under grant agreement Nº685793 Proposal of the Heat Exchangers for Micro-ORC Module Driven by Domestic Gas Boiler Jan Wajs, Dariusz Mikielewicz, Elzbieta Fornalik-Wajs Abstract: Technical development is strictly connected with the energy utilization. It is observed that demand for energy is increasing every year, therefore in parallel to the technological discoveries, new better ways of energy usage are looked for and investigated. New directions in the field of distributed energy generation are also considered as a support for the operation of the centralized system. Therefore, dispersed generation systems are proposed and developed. Moreover, the current approach to the electric energy production is a kind of prosumer one, in which the system user can be the energy consumer and also its seller to the power grid. In accordance with the micro-CHP potential analysis of the European market the distributed systems can be divided in three groups namely: systems with internal combustion (reciprocating gas engine, gas turbine), systems with external combustion (Stirling engine, steam engine, ORC) and fuel cells. Taking into account these technologies and their development, the ORC system seems to be promising among various micro-CHP domestic units (electrical power production below 10 kWe). However practical realization of the ORC cycle in a micro-scale is a kind of technical challenge. The system is equipped with various constituent devices such as the heat source (boiler), expansion device (volumetric engine or vapour microturbine) and heat exchangers. Each of them should be of high performance so that the system as a whole should work efficiently. This is the reason why novel constructions of recuperators or heat transfer enhancement mechanisms are looked for in relation to the evaporator, condenser or regenerator. In the present paper the own constructions of compact heat exchangers with microjets [1,2] and with minichanels (plate [3] and cylindrical [4] constructions) are proposed. They were designed for the purpose of domestic ORC system investigations and for other dispersed energy generation technologies. One of them (the microjets heat exchanger) is a patented design. The features of mentioned above heat exchangers are discussed together with the flow and thermal characteristics of their prototypes. As a summary, an experimental studies of the authors domestic ORC unit equipped with prototype minichannels heat exchangers are also presented. Very good thermal performance of this system was proved. References: [1] Wajs J., Mikielewicz D., Fornalik-Wajs E. (2013) Microjet heat exchanger with a cylindrical geometry, especially for heat recovery from low-temperature waste energy sources. Polish patent, PL224494 (in Polish). [2] Wajs J., Mikielewicz D., Bajor M., Fornalik-Wajs E. (2015) Heat exchanger and method for exchanging heat. European Patent Application EP 3067652 A1. [3] Wajs J., Mikielewicz D., Fornalik-Wajs E. (2016) Thermal performance of a prototype plate heat exchanger with minichannels under boiling conditions. Journal of Physics, Conference Series, vol. 745, art. Nr 032063, doi:10.1088/1742-6596/745/3/032063 [4] Wajs J., Mikielewicz D., Jakubowska B. (2018) Performance of the domestic micro ORC equipped with the shell-and-tube condenser with minichannels. Energy, 157, 853-861. ORC Unit for Heat Recovery from the Compressed Air Industry Łukasz Jędrzejewski, Tomasz Suchocki, Piotr Lampart Abstract: The use of waste heat in industry is becoming a particularly important aspect in the current state of climate change and the growing demand for electricity by individual consumers and by industry. The stability and the availability of such energy plays an important role in the case of electricity production from secondary heat applications. Production of process gases, e.g. compressed air, is an unstable source of waste heat, dependent on production cycle and actual load. This work presents the design of an ORC unit that is dedicated to work in such conditions with secondary heat from the compressed air industry. Oil is the source of heat in the compressors, which acts as a lubricating, sealing and cooling medium for the compression module. The presented ORC plant is intended to cooperate with two screw compressors; 110 kWe power each. The total amount of heat available from two units is on the level of 120 kW. The devices need to stay separated and the oil from two machines cannot be mixed, therefore an intermediate water loop with two exchangers was incorporated. After a series of analyses of several variants of the power plant and operating fluids, a variant without regeneration was proposed. The working medium chosen to operate in the ORC system is a new generation refrigerant R1233zd characterized by very low environmental impact (ODP = 0, GWP = 1). The entire system together with the single-stage axial turbine was made as a hermetic design. There is a high-speed three-phase generator with a capacity of 10 kWe on one shaft with a turbine. Due to the regime of work in changing conditions and the need for a quick start and stop a super-precision rolling bearing system with a self-regulating bearing tension mechanism was used. At the nominal point the turbine operates at a rotational speed of 24,000 RPM and a mass flow of 0.5 kg/s. In addition, the design of the turbine blade system has been optimized in order to maximize efficiency and find the optimal variant to work in the whole range of changing working conditions. Secondary Flow Analysis of an ORC Radial Inflow Turbine Used in Waste Heat Recovery Applications Ashish Alex Sam, Apostolos Pesyridis Abstract: Organic Rankine Cycle (ORC) systems are considered as the most promising technology for engine waste heat recovery applications. ORC systems recover useful power from waste heat and thus results in lower fuel consumption and pollutant emissions. ORC systems used in engine waste heat recovery applications are generally medium-sized ORC power systems, of the range of tens to hundreds of kilowatts that employ radial inflow turbines for expansion. The turbine is regarded as the most critical component in Organic Rankine Cycle (ORC) systems. Any improvement in the system efficiency calls for improvement in the performance of the turbine. This requires detailed analysis of the turbine flow field and identification of the various sources of losses. The design of turbines for ORC systems is quite critical due to the molecularly complex and high dense characteristics of ORC fluids. Moreover, as the single-stage high-pressure radial turbines are generally operated close to the critical point of the working fluids, they will exhibit complex flow characteristics like shock waves. In order to evolve a design that yields better isentropic efficiency, it is imperative to understand the sources of inefficiency by investigating the turbine flow field. In the present work, three-dimensional compressible flow analysis of an ORC radial inflow turbine is performed using Computational Fluid Dynamics (CFD). The turboexpander has been designed based on the design methodologies proposed by Balje, Kun and Sentz and Hasselgruber. The analyses include the identification of the various secondary flows within the turbine, their origins, the corresponding loss in turbine performance, the increase in entropy due to these losses and the effects of various geometrical parameters on these losses. The outcome of this study can also be used to improve the existing preliminary design methodologies for the development of efficient radial inflow turbines for ORC systems. Experimental Results of a Carnot Battery Consisting of an ORC and a High Temperature Latent Heat Thermal Storage Kenny Couvreur, Sergei Gusev, Michel De Paepe, Bruno Vanslambrouck Abstract: ORC systems have extensively been investigated over the years. However, there is limited research in trying to understand the dynamic behaviour of ORC systems and reduce the effects of waste heat fluctuations on ORC system operation. A possible solution to this is the implementation of thermal energy storage (TES) systems to smooth the thermal power fluctuations entering the ORC system. At Ghent University Campus Kortrijk a latent heat thermal energy storage (LHTES) system is commissioned and integrated in a test-rig, consisting of a 250 kWe heater and a 11 kWe ORC, interconnected via a thermal oil circuit. This test-rig is used to demonstrate the advantage of a combined LHTES-ORC system enabling stable ORC operation under fluctuating waste heat conditions. Furthermore, it demonstrates the opportunities of the so called Carnot batteries in overcoming the mismatch between the energy supply and the power demand when generating electricity from renewable energy sources. Based on the experimental characterization of the LHTES and the ORC system a performant control procedure is developed to enable stable ORC operation on the thermal energy retrieved from the LHTES system. With this set-up it is demonstrated that excess (renewable) electricity can effectively be stored as thermal energy at high temperatures (220°C) and afterwards can be recovered by means of a waste heat to power cycle in the form of an ORC. When the LHTES is fully charged, an ORC operation of 1.5h at full capacity can be achieved. Commissioning of the Orchid Experimental Facility Adam Head, Carlo de Servi, Emiliano Casati, Piero Colonna Abstract: Organic Rankine Cycle (ORC) power systems are receiving increased recognition for the conversion of thermal energy into mechanical work or electricity down to power output of, say, 10 kWe. Efficient expanders are the enabling components of such systems, and these machines get more challenging to design as their size decreases. Virtually no experimental gasdynamic data are available in the open literature concerning the fluids and flow conditions of interest for mini-ORC expanders, which hampers the validation of design methodologies and tools. In order to bridge this gap, a new experimental facility capable of continuous operation was designed and built at Delft University of Technology, The Netherlands, starting in 2015. This is called Organic Rankine Cycle Hybrid Integrated Device (ORCHID), and its conceptual and preliminary design were presented in 20161 . This contribution aims at presenting to the ORC community the status of the ORCHID facility, whose commissioning was successfully concluded at the end of 2018. Some exemplary results of commissioning tests using siloxane MM as the working fluid are shown in the figure. The target evaporation temperature (T2) -252 ℃ in this case- is reached and kept stable within ± 1 ℃ for several hours (shaded regions). The larger variations are due to adjustments and checks performed for commissioning purposes. Field monitoring results of an ORC system integrated in a steel mill Miguel Ramirez Stefanoua, Mercedes Gómez de Artechea, Andrea Panizza Abstract: Global warming is a clear threat to the life in our planet and European policies define a long-term strategy to reduce greenhouse gas emissions [1]. Industries, as large energy consumers, play a key role on this transition in which industrial waste heat recovery is a critical point to reduce fossil fuel consumption and therefore CO2 emissions. This work presents the experimental results of the annual performance of a 1,8MWe ORC system integrated in a steel mill. The waste heat recovered from the fumes of an Electric Arc Furnace (EAF) at ORI Martin is used to generate steam to deliver heat to a district heating (DH) grid during heating season and the rest of the year to run an ORC (Turboden). The results of one year of monitoring showed that a total of 45910 MWh of heat was recovered in a period of 4952 hours of plant operation. From the total heat generated 46% was delivered to the DH grid and 33% to the ORC, considering heat losses. The ORC overall efficiency resulted in 17,4% and generated 2631 MWh of electricity which corresponds to approximately 6% of the total energy recovered. The hypothetical case of full ORC operation during a year was simulated and considering the plant´s losses the total electricity generated could reach approximately 7000MWh. This could result in annual carbon savings estimated on 2457 t CO2 based on a carbon footprint for Brescia of 0.353kg CO2 eq. per kWh. [2] [1] European Commission (2018). Our vision for a clean planet for all. [2] Electricitymap. 2019. Climate impact by area. [ONLINE] Available at: https://www.electricitymap.org. [Accessed 25 July 2019].