Explanation Express the mass rate of water. m ˙ w = m ˙ a ( ω 1 − ω 2 ) (I) Here, mass rate of air is m ˙ a and specific humidity at state 1 and 2 is ω 1 and ω 2 respectively. Express enthalpy of water. h w = h f @15°C (II) Here, enthalpy saturated liquid at temperature of 15°C is h f @15°C . Express enthalpy at state 1. h 1 = c p T 1 + ω 1 h g @30°C (III) Here, specific heat at constant pressure of air is c p , temperature at state 1 is T 1 and enthalpy saturated vapor at temperature of 30°C is h g @30°C . Express enthalpy at state 2. h 2 = c p T 2 + ω 2 h g @15°C (IV) Here, temperature at state 2 is T 2 and enthalpy saturated vapor at temperature of 15°C is h g @15°C . Express the rate of heat removal from the air. Q ˙ = m ˙ a ( h 1 − h 2 ) − m ˙ w h w (V) Conclusion: Substitute 0 .4 kg / s for m ˙ a , 0 .023 kg / kg dry air for ω 1 and 0 .015 kg / kg dry air for ω 2 in Equation (I). m ˙ w = ( 0 .4 kg / s ) [ ( 0 .023 − 0.015 ) kg / kg dry air ] = 0.0032 kg / s Refer Table A-4, “saturated water-temperature table”, and write enthalpy saturated liquid at temperature of 15°C . h f @15°C = 62.982 kJ / kg Substitute 62.982 kJ / kg for h f @15°C in Equation (II). h w = 62.982 kJ / kg Refer Table A-4, “saturated water-temperature table”, and write enthalpy saturated vapor at temperature of 30°C and 15°C . h g @30°C = 2555.6 kJ / kg h g @15°C = 2528.3 kJ / kg Refer Table A-2, “ideal gas specific heats of various common gases”, and write specific heat at constant pressure of air. c p = 1.005 kJ / kg ⋅ °C Substitute 1

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Chapter 14.7, Problem 146FEP

To determine

The rate of heat removal from the air is:

(a) 6 kJ/s

(b) 8 kJ/s

(c) 11 kJ/s

(d) 14 kJ/s

(e) 16 kJ/s

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Chapter 14.7, Problem 145FEP

Chapter 14.7, Problem 147FEP

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The rate of heat removal from the air is: (a) 6 kJ / s (b) 8 kJ / s (c) 11 kJ / s (d) 14 kJ / s (e) 16 kJ / s

Solution Summary: The author explains the rate of heat removal from the air and the enthalpy of water.

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The rate of heat removal from the air is:

(a) 6 kJ/s

(b) 8 kJ/s

(c) 11 kJ/s

(d) 14 kJ/s

(e) 16 kJ/s

Want to see the full answer?

Chapter 14 Solutions

The rate of heat removal from the air is: (a) 6 kJ / s (b) 8 kJ / s (c) 11 kJ / s (d) 14 kJ / s (e) 16 kJ / s

Solution Summary: The author explains the rate of heat removal from the air and the enthalpy of water.

Videos

The rate of heat removal from the air is: (a) 6 kJ/s (b) 8 kJ/s (c) 11 kJ/s (d) 14 kJ/s (e) 16 kJ/s

Want to see the full answer?

Chapter 14 Solutions

The rate of heat removal from the air is:

(a) 6 kJ/s

(b) 8 kJ/s

(c) 11 kJ/s

(d) 14 kJ/s

(e) 16 kJ/s