Parametric study and working fluid selection of modified combined power and refrigeration cycles (MCPRCs) using low-temperature heat sources

Abstract

This paper presents a theoretical analysis of various combined power and refrigeration cycles (CPRCs) as well as the working fluid selection used in these cycles based on the first law of thermodynamics. These proposed cycles include a combination of organic Rankine cycles (ORCs) and an ejector refrigeration cycle (ERC) to produce more power and refrigeration, simultaneously. In all the proposed cycles, the ejector is driven by the exhausts of the turbine. The performance of the proposed cycles for five appropriate working fluids (i.e., isobutane, isobutene, butene, R236fa, and R245fa) is evaluated by the means of their corresponding thermal efficiency and power/refrigeration ratio. It has been demonstrated that among all the proposed working fluids, isobutane is a good candidate with a thermal efficiency of 39.03–44.52%, which is enhanced through these modifications, successively. In this study, simple CPRC and modified regenerative CPRC with an IHE have the minimum and maximum thermal efficiencies, respectively. Thermal efficiency is improved by 8.27, 6.76, 5.63, 5.33, and 5.49%, in the case of R245fa, R236fa, butene, isobutene, and isobutane, respectively. Throughout these state-of-art modifications, rejecting heat has also been decreased. Moreover, the effects of key parameters such as evaporator, condenser, and generator temperatures on each cycle are also investigated.