A heat pump operates continuously with 0.5 kg/s of R-134a condensing from a saturated vapor to a saturated liquid at 1200 kPa to provide the heat rejected to the warm space. If the coefficient of performance of the heat pump is 4.50, determine the power required to drive the compressor operating in the heat pump.
Given: R-134a; P = 1200 kPa; x1 = 1.0; x2 = 0.0; m?=0.5kgs; Heat Pump: y= 4.5
Assume: For the refrigerant condensing system: W? = ?KE = ?PE = 0
What will be an ideal response?
The condensing refrigerant is an open system, with a single-inlet, single-outlet, steady-state, steady-flow model. The First Law reduces to Q?=m?(h2?h1)
For R-134a: h1 = 270.99 kJ/kg; h2 = 115.76 kJ/kg
So, Q?= -77.6 kW = Q?H
For the heat pump: |W?|=|Q?H|? = 17.2 kW
Because it is a power input, W?= -17.2 kW
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