Highlighting the effect of the lower operating limit of the condenser on ORC working fluids selection

Abstract

In this paper, the study of the effect of the lower operating limit of the condenser on ORC working fluids selection was studied. A sample of 56 fluids constituting the starting universe was extracted in EES software. Two scenarios were studied depending on the definition of the condensing limit. The results shown that the starting universe is partitioned into two quite defined and distinct sub-universes for which two fluids taken separately in each sub-universe cannot be compared due to a condensing limit constraint. Furthermore, it was found that the size of each sub-universe depends not only on the operating condition of the condenser but also on the condensing limit constraint. By extending the study to a subcritical organic Rankine cycle with an internal heat exchanger, it was found that good performance can be obtained by defining the condensing limit from pressure compared to that obtained using temperature. Therefore, it was established that the lower operating limit of the condenser is an additional criterion to be taken into account when performing a working fluids selection for an ORC system in order to conduct a real comparative study. The work could shed some lights on designing of ORC.