Analysis of a solar assisted heat pump system with hydrocarbon refrigerants suitable for heating applications

Abstract

Heat pumps are considered as energy augmenting devices due to its capability of delivering more heat output than the equivalent input it takes for running the compressors. The performance of heat pump can be enhanced by integrating it with various renewable energy options such as solar, geothermal and their hybrid forms. Moreover, electric heat pumps can operate using the grid power and based on the electricity prices it can contribute to optimal load management. The initial investments for geothermal based heat pumps are more compared to that of the solar assisted heat pump systems. Hence, the first research and development initiatives have been made on solar assisted heat pump systems. Most of the solar assisted heat pump systems are working with R22 as refrigerant due to its good thermo-physical and thermodynamic properties. However, R22 is having poor environmental related characteristics (higher ozone depletion and global warming potential values). Hence, it is essential to identify possible immediate alternative refrigerants to phase out R22 wherever it is being used. This is particularly true with respect to the solar assisted heat pump applications. The performance of various alternatives (R290, R1270, R433A, and NHCM (50:50 of R290/R1270, by mass) have been experimentally investigated in the present work. The energy and exergy analysis have been carried out to quantify the energy conversion, and to identify the inefficiency of components used in the solar heat pump system. The selected hydrocarbon refrigerant properties such as vapor pressure, latent heat, density, thermal conductivity, viscosity, boiling temperature, critical pressure, and temperature were predicted using the REFPROP® database. Comparisons of new refrigerant properties are attempted (with that of R22) in order to arrive at the best alternative refrigerant. newline