A heat pump based on the vapor-compression refrigeration cycle uses R-134a as the working fluid. The heat pump is used to heat a 1000 SCFM stream of air from 40°F to 90°F. The condenser pressure is 160 psia, the evaporator pressure is 30 psia, and the isentropic efficiency of the compressor is 85%. a) Find the enthalpy of the R-134a exiting the compressor (answer: 122.98 Btu/lbm). b) Find the coefficient of performance of the heat pump (answer: 4.22). c) Find the power input required to drive the compressor (answer: 5.05 hp). A volumetric flow rate in SCFM (standard cubic feet per minute) is converted into a mass flow rate by assuming a density of air at 68°F and 14.696 psia. Use Cengel's R-134a tables posted on Canvas to model the refrigerant. TIN = 40°F Expansion Valve 3 1000 SCFM QCONDENSER 2 Condenser 160 psia Evaporator 30 psia EVAPORATOR TOUT = 90°F Compressor W COMPRESSOR

A heat pump based on the vapor-compression refrigeration cycle uses R-134a as the working fluid. The heat pump is used to heat a 1000 SCFM stream of air from 40°F to 90°F. The condenser pressure is 160 psia, the evaporator pressure is 30 psia, and the isentropic efficiency of the compressor is 85%. a) Find the enthalpy of the R-134a exiting the compressor (answer: 122.98 Btu/lbm). b) Find the coefficient of performance of the heat pump (answer: 4.22). c) Find the power input required to drive the compressor (answer: 5.05 hp). A volumetric flow rate in SCFM (standard cubic feet per minute) is converted into a mass flow rate by assuming a density of air at 68°F and 14.696 psia. Use Cengel's R-134a tables posted on Canvas to model the refrigerant. TIN = 40°F Expansion Valve 3 1000 SCFM QCONDENSER 2 Condenser 160 psia Evaporator 30 psia EVAPORATOR TOUT = 90°F Compressor W COMPRESSOR

Refrigeration and Air Conditioning Technology (MindTap Course List)

8th Edition

ISBN:9781305578296

Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson

Publisher:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson

Chapter3: Refrigeration And Refrigerants

Section: Chapter Questions

Problem 12RQ: The condensing pressure is 260 psig and the condenser outlet temperature is 108F for R-22. By how...

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Question

A heat pump based on the vapor-compression refrigeration cycle uses R-134a as the
working fluid. The heat pump is used to heat a 1000 SCFM stream of air from 40°F to
90°F. The condenser pressure is 160 psia, the evaporator pressure is 30 psia, and the
isentropic efficiency of the compressor is 85%.
a) Find the enthalpy of the R-134a exiting the compressor (answer: 122.98 Btu/lbm).
b) Find the coefficient of performance of the heat pump (answer: 4.22).
c) Find the power input required to drive the compressor (answer: 5.05 hp).
A volumetric flow rate in SCFM (standard cubic feet per minute) is converted into a
mass flow rate by assuming a density of air at 68°F and 14.696 psia.
Use Cengel's R-134a tables posted on Canvas to model the refrigerant.
TIN = 40°F
Expansion
Valve
3
1000 SCFM
QCONDENSER
Condenser
160 psia
Evaporator
30 psia
QEVAPORATOR
TOUT = 90°F
Compressor
W COMPRESSOR

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