Experimental Study of Small Scale and High Expansion Ratio ORC for Recovering High Temperature Waste Heat

orc2019 Tracking Number 94

In the recent times, the use and development of small-scale (about 10 kW) ORC systems has received an increasing interest in different applications. In this study, a small-scale ORC system having high operational temperature of close to 300 oC was investigated experimentally. The studied ORC system has a high-speed turbogenerator (rotational speed of 30 000 rpm) including a supersonic radial inflow turbine, a permanent magnet generator and a barske type feed pump assembled on a single shaft. The experimental system uses high molecular weight siloxane MDM as the working fluid. The ORC system under study was designed to be able to operate at high operational temperatures that can be found for example in high temperature exhaust gas heat recovery and in small-scale biomass or biogas applications. The operation of the whole ORC system and especially the operation of the turbogenerator was studied in detail under different operating conditions with varying heat loads and with varying turbogenerator rotational speeds. The experimental results were compared against the results obtained from the numerical ORC cycle model for validating and comparing the numerical and experimental results. Based on the results, the technical potential of using high rotational speed and supersonic turbomachinery in small-scale and high expansion ratio ORC applications was confirmed experimentally. The paper describes and discusses the main advantages and specific operational characteristcs of the studied ORC system as well as discusses the key aspects for further reducing losses in ORC systems adopting small-scale and high rotational speed turbomachinery.