To determine The heat transfer per unit volume. Explanation Apply the water mass balance equation to the combined cooling and dehumidification section. ∑ m ˙ w , i = ∑ m ˙ w , e m ˙ a 1 ω 1 = m ˙ a 2 ω 2 + m ˙ w m ˙ w = m ˙ a 1 ( ω 2 − ω 1 ) (I) Here, initial and final mass flow rate of dry air is m ˙ a 1 and m ˙ a 2 , specific humidity of air at entering and leaving the cooling coils is ω 1 and ω 2 , and mass flow rate of vapor is m ˙ w . Apply the energy balance equation to the combined cooling and dehumidification section. E ˙ in − E ˙ out = Δ E ˙ system ↵ ( steady ) E ˙ in − E ˙ out = 0 E ˙ in = E ˙ out ∑ m ˙ i h i + Q ˙ in = ∑ m ˙ e h e Q ˙ in = m ˙ a 1 ( h 2 − h 1 ) − m ˙ w h w (II) Here, the amount of energy rate required for cooling coils is E ˙ in , amount of rate of energy rejected from cooling coils is E ˙ out , change in the energy rate of a system is Δ E ˙ system , and rate of heat removal from air is Q ˙ out . Write the expression to obtain the heat transfer per unit volume ( Q in ) . Q in = q in v 1 (III) Conclusion: Refer Table A-4, “Saturated water – Temperature table”, write the enthalpy of saturated liquid water at ( h f @ 20 ° C = h w ) is 83.915 kJ / kg at a temperature of 20 ° C . Refer Fig A-31, “Psychrometric chart at 1 atm total pressure”, at inlet temperature ( T 1 = 18 °C ) , and relative humidity ( ϕ 1 = 11.84 % ) , read the value of inlet enthalpy ( h 1 ) as 21.93 kJ / kg dry air , inlet specific humidity ( ω 1 ) as 0.001504 kg H 2 O / kg dry air , and inlet specific volume of dry air ( v 1 ) as 0.8268 m 3 / kg dry air . Refer Fig A-31, “Psychrometric chart at 1 atm total pressure”, at outlet temperature ( T 2 = 18 °C ) and relative humidity ( ϕ 2 = 50 % ) , read the value of exit enthalpy ( h 2 ) as 34

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ISBN: 9780100257054

Author: CENGEL

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Chapter 14.7, Problem 121RP

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The heat transfer per unit volume.

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Chapter 14.7, Problem 120RP

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Chapter 14 Solutions

EBK THERMODYNAMICS: AN ENGINEERING APPR

Ch. 14.7 - What is the difference between dry air and...Ch. 14.7 - What is the difference between the specific...Ch. 14.7 - Can the water vapor in air be treated as an ideal...Ch. 14.7 - Is the relative humidity of saturated air...Ch. 14.7 - Is it possible to obtain saturated air from...Ch. 14.7 - Moist air is passed through a cooling section...Ch. 14.7 - How will (a) the specific humidity and (b) the...Ch. 14.7 - Prob. 8P Ch. 14.7 - Consider a tank that contains moist air at 3 atm...Ch. 14.7 - Why are the chilled water lines always wrapped...

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