13468-11-45P AID: 1825 | 05/12/2014

Show the heat pump that operates on the ideal vapor-compression refrigeration cycle, with refrigerant-134a as the working fluid, on diagram as in Figure (1).

For the given ideal vapor-compression refrigeration cycle, with refrigerant-134a as the working fluid, the temperature, specific enthalpy, pressure, and specific entropy at state are , , , and respectively. Also, the saturated liquid state is denoted by the subscript f, the saturated vapor is denoted by the subscript g, and the properties at latent stage are denoted by the subscript fg.

Use saturated refrigerant-134a pressure table, to find and of refrigerant-134a, at 50 psia.

For the isentropic process 1-2, entropy remains constant, hence, and are equal. Use superheated refrigerant-134a table, to find of refrigerant-134a, at 120 psia, and at . Use interpolation method to find .

Use saturated refrigerant-134a pressure table, to find of refrigerant-134a, at .

For the isenthalpic process 3-4, specific enthalpy remains constant, hence and are equal.

Find the mass flow rate of the refrigerant .

Here, the heating load for the given heat pump is .

Substitute for , for , and for to find .

Find the power input to the compressor for the given heat pump.

Substitute for , for , and for .

Hence, the power input to the compressor for the given heat pump is .

Calculate the electrical power required without the heat pump .

Find the electric power saved by using a heat pump instead of a resistance heater .

Substitute 23.58 hpfor , and 2.46 hp for .

Hence, the electric power saved by using a heat pump instead of resistance heater is .