Experimental Investigation on the Effect of a Separator on Operating Parameters of an ORC

orc2019 Tracking Number 50

The article presents the results of the experimental investigation on the effect of a vapour-liquid separator used for a low-boiling medium on operating parameters of an organic Rankine cycle (ORC). A biomass boiler with a thermal power of 25 kWt was used as a heat source. Pellets were used as its fuel. In the ORC system, the working medium (HFE7100) was heated with thermal oil. Expansion of the low-boiling medium took place in a four-stage radial-flow microturbine whose rated electric power and rotational speed are respectively 2.5 kWe and 24 krpm. It is important that the operation of this microturbine is both stable and failure-free. For this, an appropriate vapour overheating degree is needed at the microturbine’s supply side. Therefore, a prototypical inert vapour-liquid separator for the working medium was designed and built. This device allows for two modes of operation for the system; bypass mode and turbine mode. The effect the vapour-liquid separator has on the operating parameters was described and shown using heat and flow characteristics. Those characteristics were prepared on the basis of measurements conducted with thermodynamic flow meters. Observing the process was made possible by using a specifically designed sight vane. It was observed that the tested separator worked as heat storage in the ORC installation. Both during transition states of the microturbine and instantaneous fluctuations in the thermal power of the boiler (stemming from its thermal inertia and the cyclical feeding of fuel), the separator provided stable operating conditions at the proper overheating degree of the working medium’s vapour. It was found that in vapour-fed systems such a separator can also work as a clarifier or a filter for solid particles.