Ejector based organic flash combined power and refrigeration cycle (EBOFCP&RC) – A scheme for low grade waste heat recovery

In the present study a conventional waste heat driven organic flash power cycle (OFPC) utilizing R245fa as working fluid is modified by replacing its low pressure throttle valve with an ejector. R245fa coming out from the vapour separator at saturated liquid state is accelerated in the nozzle of the ejector to ensure that saturated vapour from evaporator can enter to the ejector as secondary flow and total mass of R245fa at the exit of the diffuser of the ejector be at condenser pressure. The modified cycle is designated as Ejector based organic flash combined power and refrigeration cycle (EBOFCP&RC). Analysis shows that with varying flash pressure cycle power output initially increases and becomes a maximum corresponding to an optimum flash pressure. However, refrigeration effect increases monotonically with an increase in flash pressure. Also the proposed cycle can yield higher thermal efficiency compared to conventional OFPC. A compressor is to be incorporated between the evaporator and the ejector to maintain a desirable refrigeration effect for higher condenser temperature (say 40 °C).