High-Temperature, WHR, Spinning Scroll Expander, Scroll Pump
Organic Rankine Cycles (ORC) are widely employed to extracting work from different heat sources to improve the operational efficiency of thermal systems. High-temperature ORCs (> 250 – 300 °C) are still particularly challenging especially when hydrocarbons cannot be used as the working fluids. Generators for Small Electric and Thermal Systems (GENSETs) are one example of systems where ORCs can be used as a bottoming cycle. A 1 kWe ORC has been previously constructed to evaluate the feasibility of designing an ORC with a heat source inlet temperature of approximately 500 °C. The test stand utilizes microtube evaporator, an air-cooled microchannel condenser, a plate heat exchanger as regenerator, scroll rotating machines as both expander and pump. To increase the efficiency of the ORC, novel scroll pump design and Oldham Ring scroll expander were installed. An extensive experimental campaign was carried out to map the performance of the expander and the pump along with the overall system performance using R245fa as the working fluid. In addition, thermocouple mesh has been inserted at the upstream and downstream of the evaporator to study the temperature maldistribution from the heat source. The performance was mapped at steady state over a range of operating conditions. The mapped performance has been used to develop a charge-sensitive dynamic model of the ORC system to be predict performance at off-design conditions and develop a control strategy. A discussion on the degradation of the lubricant oil in the system has also been included.