Explanation Write the expression to obtain the specific humidity ( ω 1 ) of air entering. ω 1 = c p ( T 2 − T 1 ) + ω 2 h f g 2 h g 1 − h f 2 (I) Here, inlet temperature is T 1 , wet bulb temperature is T 2 , constant pressure specific heat is c p , specific humidity of air leaving is ω 2 , enthalpy at evaporation is h f g 2 , enthalpy at saturation vapor is h g 1 , and enthalpy at saturation liquid is h f 2 . Write the expression to obtain the specific humidity ( ω 2 ) of air leaving. ω 2 = 0.622 P g 2 P 2 − P g 2 (II) Here, saturation pressure of water at 75 ° F is P g 2 and total pressure at 90 ° F is P 2 . Conclusion: Refer Table A-4E, “Saturated water – Temperature table”, obtain the properties of water at a temperature of 75 ° F . h f g 2 = 1050.9 Btu / lbm h f 2 = 43.07 Btu / lbm P g 2 = 0.43016 psia Refer Table A-4E, “Saturated water – Temperature table”, obtain the properties of water at a temperature of 90 ° F . h g 1 = 1093.9 Btu / lbm P g 1 = 0.69904 psia Refer Table A-2E, “Ideal gas specific heats of various common gases”, obtain the value of c p for air as 0.240 Btu / lbm ⋅ R . Substitute 0.43016 psia for P g 2 and 1 atm for P 2 in Equation (II). ω 2 = 0.622 ( 0.43016 psia ) ( 1 atm ( 14.696 psi 1 atm ) ) − ( 0

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ISBN: 9780073398174

Author: Yunus A. Cengel Dr., Michael A. Boles

Publisher: McGraw-Hill Education

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Chapter 14.7, Problem 44P

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The adiabatic saturation temperature.

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Chapter 14.7, Problem 43P

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Chapter 14 Solutions

Thermodynamics: An Engineering Approach

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