(a)
The volume flow rate of air into the cooling tower.
(a)
Answer to Problem 111P
The volume flow rate of air into the cooling tower is
Explanation of Solution
As the process is a steady flow and thus the mass flow rate of dry air remains constant during the entire process.
Here, the mass flow rate of air at inlet is
Express the water mass balance:
Here, mass flow rate of water at inlet and exit is
Express the energy balance.
Here, the rate of total energy entering the system is
Express initial partial pressure.
Here, relative humidity at state 1 is
Express partial pressure of air at state 1.
Here, pressure at state 1 is
Express specific volume at state 1.
Here, gas constant of air is
Express initial humidity ratio.
Express initial enthalpy.
Here, specific heat at constant pressure is
Express final partial pressure.
Here, relative humidity at state 2 is
Express final humidity ratio.
Here, pressure at state 2 is
Express final enthalpy.
Here, final specific enthalpy saturated vapor at temperature of
Express the volume flow rate of air into the cooling tower.
Here, specific volume at inlet is
Conclusion:
Refer Table A-2, “ideal-gas specific heats of various common gases”, and write the properties of air.
Refer Table A-4, “saturated water-temperature table”, and write the saturation pressure and initial specific enthalpy saturated vapor at temperature of
Substitute
Substitute
Substitute
Substitute
Substitute
Refer Table A-4, “saturated water-temperature table”, and write the saturation pressure and final specific enthalpy saturated vapor at temperature of
Substitute
Substitute
Substitute
Refer Table A-4, “saturated water-temperature table”, and write the enthalpy at state 3 at temperature of
Here, enthalpy of saturation liquid is
Refer Table A-4, “saturated water-temperature table”, and write the enthalpy at state 4 at temperature of
Substitute
Substitute
Hence, the volume flow rate of air into the cooling tower is
(b)
The mass flow rate of the required makeup water.
(b)
Answer to Problem 111P
The mass flow rate of the required makeup water is
Explanation of Solution
Express the mass flow rate of the required makeup water.
Conclusion:
Substitute
Hence, the mass flow rate of the required makeup water is
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Chapter 14 Solutions
THERMODYNAMICS FDOC PRINT COMP
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