Analysis of low GWP ternary zeotropic mixtures applied in high-temperature heat pump for waste heat recovery

Abstract

In this study, the novel low GWP ternary large glide temperature zeotropic mixtures were proposed to apply in the high-temperature heat pump for waste heat recovery. The ternary zeotropic mixtures were composed of two retardants (CO2 and R1233zd(E)) and one flammable, including (R600a, R290, R1270, and RE170). First, a novel method, which combines the operated pressure, glide temperature, flammability, safety, energy, and exergy efficiency, were proposed to select the proper ternary zeotropic mixture applied in the high temperature heat pump. Besides, the effect of operated temperature parameters, including the subcooling degree (Tsc), superheating degree (Tsh), dew point temperature in evaporator (Tdew,evap), and dew point temperature in condenser(Tdew,cond), on the performance of the high temperature heat pump using the selected optimal ternary zeotropic mixture was conducted further. The results show that the ternary zeotropic mixture CO2/R600a/R1233zd(E) was selected to applied in the high temperature heat pump with the mass fraction of 0.2/0.7/0.1, and the maximum heating coefficient of performance (COPh), volumetric heating capacity (qv) and exergy efficiency (ηex) are 3.22, 3017 kJ/m3 and 0.402, respectively under the selected condition. Besides, compared with the Tsc and Tsh, the Tdew,cond and Tdew,evap affect the performance notable for the selected ternary zeotropic mixture, especially for the Tdew,cond, which affect the condensation pressure significantly and should be gain more attention for the high temperature application. Among the Tdew,cond and Tdew,evap, The COPh and qv are sensitive to the Tdew,cond and the Tdew,evap, respectively. The results hope to promote the application and research of low GWP zeotropic mixtures in the high-temperature heat pump.