Studies on direct expansion solar Thermal heat pump systems using R430a as a substitute to r134a

Abstract

The heat pumps have been widely using for heating applications such as drying, water heating, space heating and desalination due to its higher energy efficiency when compared to other heating systems. Most of the heat pumps are using halogen-based refrigerants owing to its good thermodynamic and thermo-physical properties. However, the halogen-based refrigerants are having poor environmental properties such as ozone depletion potential and global warming potential. As a result, the use of halogen-based refrigerants in heat pump applications is restricted. Therefore, it is necessary to identify the refrigerants with global warming potential lower than 150 for heat pump applications. The main scope of this research work is to test the possibility of using R430A in solar assisted heat pump heating systems. The energy, exergy, refrigerant-lubricant interaction, safety and service issues of direct expansion solar thermal heat pump systems are investigated using R134a and R430A as a possible alternative working fluid. The refrigerant R430A is a binary refrigerant mixture composed R152a and R600a (in the ratio of 76:24, by mass). The presence of R600a in the mixture is miscible with both mineral oil and synthetic lubricants. Hence, the lubricants using in R134a compressors can be retained while using R430A as working fluid. The thermo-physical properties such as vapour pressure, liquid density, latent heat, viscosity, specific heat and thermal conductivity of R134a and R430A are compared across wide range of temperatures between 0 and 90oC. The thermodynamic properties such as molecular weight, critical temperature, critical pressure and boiling point of R134a and R430A are compared newline newline newline