Analysis of the possibility of using R718 for a heat pump of a heating system based on a liquid-vapor ejector

Abstract

The study explores the possibility of using water (R718) as a refrigerant for a heat pump installation of a heating system. This unit is a vapor compression heat pump with a regenerative heat exchanger in which the vacuum unit based on a liquid-vapor ejector is used instead of a scroll refrigeration compressor. The work-ing process of such an apparatus is based on implement-ing a fundamentally new cycle that does not require the supply of working steam from the outside. Instead, steam is generated inside the vacuum unit. The arti-cle describes the proposed installation and its differ-ences from the traditional one, both in terms of circuit solutions and in terms of the operating cycle. A ther-modynamic calculation was performed for the proposed installation with R718 as the working medium and the traditional heat pump systems operating on refriger-ants R142b, R254fa, and R410a. As a result of the cal-culation, the parameters of all the devices included in these schemes were obtained, and the conversion factors of the cycles were determined. To assess the feasibili-ty of using R718 as a working substance and replacing the scroll refrigeration compressor with a liquid-vapor ejector, an exergy analysis was performed. This made it possible to fairly accurately determine the effective-ness of each circuit, since it implemented the possibility of comparing systems using several types of energy (for example, electrical and thermal). As a result, the val-ues of exergetic efficiency of traditional and proposed schemes were obtained. The final stage of the study was the performance of a thermoeconomic analysis. The esti-mated cost was determined for a unit of heat quantity per ton of the product and per unit of the heated area obtained in a unit with the working substance R718 and traditional installations with the working substances R142b, R254fa, and R410a.