EXPERIMENTAL INVESTIGATION OF A RADIAL MICROTURBINE IN ORGANIC RANKINE CYCLE SYSTEM WITH HFE7100 AS WORKING FLUID

asme-orc2015 Tracking Number 13

The paper presents the results of experimental investigation of the ORC system with prototype microturbine. The prototype of biomass boiler has been used as a heat source. The boiler with a power rating of 25 kWth is powered by biomass (wood pellets) using a screw auger. The biomass boiler heats thermal oil which is directed to the evaporator where the low boiling refrigerant evaporates. The maximum temperature of the thermal oil in the evaporator is about 210 °C – 215 °C. The solvent HFE7100 was used as the working fluid in the ORC system. The prototype of four-stage radial microturbine and biomass boiler has been designed and built at the Institute of Fluid-Flow Machinery of the Polish Academy of Sciences in Gdańsk (Poland). The designed electric capacity of microturbine is 2.7 kWe at maximum speed of 24000 rpm. The isentropic efficiency for this fluid-flow machine is about 70%. The generated electricity is dissipated by an electric heater with a power of 5 kWe and eleven light bulbs 100 W each. Electrical load can be adjusted according to your needs. At the inlet of the microturbine a condensate separator was applied to protect the blades from erosion and to ensure the proper operation of gas bearings. In the initial phase steam microturbine is supplied with a high degree of superheat in the range from 30 K to 40 K - the make warm phase of the microturbine. During normal operation of the microturbine, superheating degree of the low boiling fluid in the range of 5 K to 10 K. The working fluid after expansion in microturbine is directed to the regenerator and then to the condenser. The heat supplied to the condenser dissipated a fan cooler with maximum power of 50 kW. Depending on the flow rate of the glycol in the condenser the absolute pressure in the range of 1.2 bar - 3 bar and a temperature of the working fluid in the range from 20 °C to 65 °C can be obtained. The paper presents the characteristics of the ORC system and radial microturbine for different variants of working medium flow rates (thermal oil, HFE7100, glycol). During testing of the ORC system with prototype of radial microturbine and the biomass boiler (fired with wood pellets) the maximum electrical output power was around 1500 We.