Influence of evaporating rate on two-phase expansion in the piston expander with cyclone separator

Abstract

The trilateral flash cycle shows a greater potentiality in moderate to low grade heat utilization systems due to its potentiality of obtaining high exergy efficiency, compared to the conventional thermodynamic cycles such as the organic Rankine cycles and the Kalina cycle. The main difference between the trilateral flash cycle and the conventional thermodynamic cycles is that the superheated vapor expansion process is replaced by the two-phase expansion process. The two-phase expansion process actually consists of a flashing of the inlet stream into a vapor and a liquid phase. Most simulations assume an equilibrium model with an instantaneous flashing. Yet, the experiments of pool flashing indicate that there is a flash evaporating rate. The mechanism of this process still remains unclear. In this paper, the flash evaporating rate is introduced into the model of the two-phase expansion process in the reciprocating expander with a cyclone separator. As such, the obtained results reveal the influence of evaporating rate on the efficiency of the two-phase expander.