Parameters of a cascade two-stage air-to-water heat pump at low ambient temperature

The results of the numerical calculation of the thermodynamic parameters of a cascade (two-stage) air-to-water heat pump at low atmospheric air temperatures are presented. A Freon R407c is used in the first circuit and a R152a is used in the second circuit. Calculations are made for ambient temperatures from 7°С to –25°С. The effect of underrecovery temperatures in heat exchange equipment is shown. Cycles with R245fa, R142b, R114, R123, R290, R236fa, R600a refrigerants, a mixture of isobutane and isopentane have been investigated. The effect of the complexity of a two-stage scheme on the efficiency of the cycle has been evaluated. The use of more complex schemes (for example, with liquid injection) does not affect the thermodynamic perfection of the heat pump and may be appropriate only to ensure operational reliability. Reducing the underrecovery temperature to 1 K is shown to increase the thermodynamic efficiency of the installation.