The ratio of the maximum to minimum pressure.
Answer to Problem 141RP
The ratio of the maximum to minimum pressure is
Explanation of Solution
Determine the COP of a reversible heat pump depends on the temperature limits in the cycle only.
Here, the temperature of higher temperature body is
Determine rate of heat reject by the heat pump minimum.
Here, the power input required to operate the heat pump is
Determine the amount of heat supplied per kg of Carnot heat pump cycle.
Here, the mass flow rate of the working fluid is
Conclusion:
Substitute
Substitute 6.0 for
Substitute
Refer to Table A-4, “Saturated water”, obtain the below properties at the enthalpy of vaporization of
Write the formula of interpolation method of two variables.
Here, the variables denote by x and y are enthalpy of vaporization and temperature.
Show the temperature at
S. No |
enthalpy of vaporization |
Temperature, |
1 | ||
2 | ||
3 |
Calculate final temperature at enthalpy of vaporization of
Substitute
From above calculation the temperature of the working fluid is
Repeat the above Equation (IV) for saturated maximum pressure at
From this cycle maximum absolute temperature in the cycle is 1.2 time the minimum absolute temperature.
Substitute 309.6 K for
Repeat the above Equation (IV) for saturated maximum pressure at
Calculate the ratio of the maximum to minimum pressure.
Here, the minimum pressure is
Substitute 925.3 kPa for
Thus, the ratio of the maximum to minimum pressure is
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Chapter 6 Solutions
CENGEL'S 9TH EDITION OF THERMODYNAMICS:
- Consider a Carnot heat engine cycle executed in a closed system in the saturated liquid-vapor mixture region using 0.8 kg of R-134a as the working fluid. The maximum and minimum temperatures in the cycle are 60°C and 20°C, respectively. It is known that the refrigerant is saturated liquid at the beginning of the heat addition process, and the net work output from the cycle is 13.360 kJ.arrow_forwardA refrigerator using fluid-134a as a work fluid is used to keep the cooling medium at -25 oC. The refrigerator releases the waste heat, which enters the condenser at 18 oC with a flow of 0.30 kg / s and from the condenser at 26 oC to the cooling water. The refrigerant enters the condensate at a pressure of 1.2 MPa and 50 oC, and leaves the condenser at 40 oC at the same pressure. Find a) the mass flow rate of the refrigerant, b) the power consumed by the compressor, c) the COP value, and d) the minimum power that the compressor will consume for the same cooling load.They watch the specific heat of water as ?? = 4.22 ?? / ???.arrow_forwardRefrigerant-134a enters the compressor of a refrigerator as superheated vapor at 0.14 MPa and – 10°C at a rate of 0.12 kg/s, and it leaves at 0.7 MPa and 50°C. The refrigerant is cooled in the condenser to 24°C and 0.65 MPa, and it is throttled to 0.15 MPa. Disregarding any heat transfer and pressure drops in the connecting lines between the components, show the cycle on a T-s diagram with respect to saturation lines, and 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 COP of the refrigerator. T 0.70MPA 2s 50°C 0.65MPA 24°C Win 0.15 MPa 0.14MPA -10°Carrow_forward
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