Air enters the compressor of an ideal gas refrigeration cycle at 12°C and 50 kPa and the turbine at 47°C and 250 kPa. The mass flow rate of air through the cycle is 0.08 kg/s. Assuming variable specific heats for air, determine (a) the rate of refrigeration, (b) the net power input, and (c) the coefficient of performance.

Air enters the compressor of an ideal gas refrigeration cycle at 12°C and 50 kPa and the turbine at 47°C and 250 kPa. The mass flow rate of air through the cycle is 0.08 kg/s. Assuming variable specific heats for air, determine (a) the rate of refrigeration, (b) the net power input, and (c) the coefficient of performance.

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

Chapter28: Special Refrigeration Applications

Section: Chapter Questions

Problem 15RQ: Why is two-stage compression popular for extra-low-temperature refrigeration systems?

See similar textbooks

Similar questions

A heat pump using refrigerant-134a heats a house by using underground water at 8°C as the heat source. The house is losing heat at a rate of 60,000 kJ/h. The refrigerant enters the compressor at 280 kPa and 0°C, and it leaves at 1 MPa and 60°C. The refrigerant exits the condenser at 30°C. Investigate the effect of varying the compressor isentropic efficiency over the range [60 to 100 percent]. Plot the power input to the compressor and the electric power saved by using a heat pump rather than electric resistance heating as functions of compressor efficiency and discuss the results.
Consider a refrigeration system using refrigerant-134a as the working fluid. If this refrigerator is to operate in an environment at 20°C, what is the minimum pressure to which the refrigerant should be compressed? Why?
The COP of vapor-compression refrigeration cycles improves when the refrigerant is subcooled before it enters the throttling valve. Can the refrigerant be subcooled indefinitely to maximize this effect, or is there a lower limit? Explain.
Refrigerant-134a enters the compressor of a refrigerator at 140 kPa and -10°C at a rate of 0.3 m3/min and leaves at 1 MPa. The isentropic efficiency of the compressor is 78 percent. The refrigerant enters the throttling valve at 0.95 MPa and 30°C and leaves the evaporator as saturated vapor at -18.5°C. Show the cycle on a T-s diagram with respect to saturation lines, and determine (a) the power input to the compressor, (b) the rate of heat removal from the refrigerated space, and (c) the pressure drop andrate of heat gain in the line between the evaporator and the compressor. answers 1.88 kW, 7.11 kW, 1.72 kPa, 0.24 kW
Determine the power required to operate a refrigerator using the ideal vapor-compression cycle with R-134a to remove 8 kW of heat and within the pressure limits of 320 and 700 kPa.
Steam enters the high-pressure turbine of a steam power plant that operates on the reheat Rankine cycle at 10 MPa and 600°C and leaves at 4 MPa. Steam is then reheated to 500°C before it expands to a pressure of 30 kPa. The enthalpy of steam is 3330 kJ/kg at the exit of the high-pressure turbine, and 2600 kJ/kg at the exit of the low-pressure turbine. Disregarding the pump work, the cycle efficiency is
Consider a refrigrator that operates on the vapor compression refrigeration cycle with R-134a as the working fluid. The refrigerant enters the compressor as saturated vapor at 70 kPa, and exits at 1200 kPa and 90°C, and leaves the condenser as saturated liquid at 1200 kPa. The coefficient of performance of this refrigrator is
A refrigerator uses R-134a as the working fluid and operates on an ideal vapor compression cycle between 0.14 MPa and 0.8 MPa. If the mass flow rate of the refrigerant is 0.06 kg/s, determine (a) the rate of heat removal from the refrigerated space, (b) the power input to the compressor, (c) the heat rejection rate in the condenser, and (d) the COP.
Consider the following ideal cascade refrigeration system with pressures of 0.9, 0.4, and 0.12 MPa.If the lower cycle transfers 69kW of energy to the upper cycle, determine the mass flowrate of R-134A (in kg/s) in the upper cycle. a.0.3987 b.0.4114 c.0.3600 d.0.4480
Refrigerant-134a enters the compressor of a refrigerator at 0.14MPa and -10°C at a rate of 0.05 kg/s and leaves at 0.8 MPa and 50°C. The refrigerant is cooled in the condenser to 26°C and 0.72 MPa and is throttled to 0.15 MPa. Determine (a) the rate of heat removal from the refrigerated space and the power input to the compressor, (b) the isentropic efficiency of the compressor, and (c) the coefficient of performance of the refrigerator. Answers: (a) 7.93 kW, 2.02 kW, (b) 0.939, (c) 3.93
A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at 10°C by rejecting waste heat to cooling water that enters the condenser at 18°C at a rate of 0.25 kg/s and leaves at 26°C. The refrigerant enters the condenser at 1.2 MPa and 50°C and leaves at the same pressure subcooled by 5°C. If the compressor consumes 2.3 kW of power, determine the COP?
Consider a regenerative gas-turbine power plant with two stages of compression and two stages of expansion. The overall pressure ratio of the cycle is 9. The air enters each stage of the compressor at 300 K and each stage of the turbine at 1200 K. Accounting for the variation of specific heats with temperature, determine the minimum mass flow rate of air needed to develop a net power output of 110 MW.