
(a)
The mass flow rate of the refrigerant.
(a)

Explanation of Solution
Given:
The refrigerated temperature is
The cooling water inlet temperature
The cooling water outlet temperature
The mass flow rate of the water
The inlet and outlet pressure of the condenser is 1.2 MPa.
The power input consumed by compressor
Calculation:
First find out the state properties of the system as shown below:
From the Table A-13, “Superheated refrigerant R-134a” obtain the value of enthalpy of the refrigerant at the inlet of the condenser at the 1.2 MPa of pressure and
At state 2, the refrigerant is subcooled by
Here, the temperature leave from the condenser is
From the Table A-13, “Superheated refrigerant R-134a” obtain the value of temperature of the refrigerant at the inlet of the condenser at the 1.2 MPa of pressure as,
Calculate the exit temperature
Refer to Table A-11, “Saturated refrigerant R-134a”, obtain the below exit enthalpy of the condenser at compressed liquid state on the basis of exit temperature of
S. No |
Temperature, |
enthalpy of vaporization |
1 | ||
2 | ||
3 |
Calculate exit enthalpy of the condenser using interpolation method.
Substitute
From above calculation the exit enthalpy of the condenser at compressed liquid state on the basis of exit temperature of
Repeat the above Equation (II) to obtain the value of enthalpy of saturated liquid that entering the inlet of the condenser at the
Repeat the above Equation (IV) to obtain the value of enthalpy of saturated liquid which is leaving the condenser at the
Calculate the rate of heat transferred to the water.
Calculate the mass flow rate of a refrigerant.
Thus, the mass flow rate of the refrigerant is
(b)
The refrigeration load of the refrigerator.
(b)

Explanation of Solution
Calculate the refrigeration load of the refrigerator.
Thus, the refrigeration load of the refrigerator is
(c)
The COP of a reversible refrigerator operating between the same temperature limits.
(c)

Explanation of Solution
Determine the coefficient of performance of the refrigerator.
Thus, the COP of a reversible refrigerator operating between the same temperature limits is
(d)
The minimum power input to the compressor.
(d)

Explanation of Solution
Calculate the maximum coefficient of performance of the reversible refrigerator operating between the same temperature limits.
Here, the temperature of higher temperature body is
Calculate the minimum power input to the condenser for the same refrigerator load.
Thus, the minimum power input to the compressor is
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Chapter 7 Solutions
Fundamentals of Thermal-Fluid Sciences
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