Explanation Express the density of ambient air. ρ ambient = P 0 R T 0 (I) Here, atmospheric pressure is P 0 , universal gas constant of air is R and surrounding temperature is T 0 . Express mass flow rate of air. m ˙ air = ρ ambient ν room ACH = ρ ambient ( l b h ) ACH (II) Here, air changes per hour is ACH , volume of room is ν room and length, width and height of room is l b h respectively. Express sensible heat load of the room. Q ˙ infiltration,sensible = m ˙ air c p ( T ambient − T room ) (III) Here, specific heat at constant pressure is c p , room temperature is T room and ambient temperature is T ambient . Express latent heat load of the room. Q ˙ infiltration,latent = m ˙ air ( ω ambient − ω room ) h f g @24°C (IV) Here, humidity ratio of room is ω room , ambient humidity ratio is ω ambient and latent heat of vaporization at temperature of 24°C is h f g @24°C . Express total heat load of the room. Q ˙ infiltration,total = Q ˙ infiltration,sensible + Q ˙ infiltration,latent (V) Conclusion: Take the atmospheric pressure as 101 .325 kPa . Refer Table A-2, “ideal-gas specific heats of various common gases”, and write the universal gas constant and specific heat at constant pressure of air. R = 0.2870 kPa ⋅ m 3 / kg ⋅ K c p = 1.005 kJ / kg ⋅ ° C Refer Table A-4, “Saturated water-temperature table”, and write the specific enthalpy evaporation or latent heat of vaporization at temperature of 24°C . h f g @24°C ≃ h f g @25°C = 2441.7 kJ / kg Here, latent heat of vaporization at temperature of 25°C is h f g @25°C . Refer Figure A-31, “Psychrometric chart at 1 atm total pressure”, and write the ambient humidity ratio corresponding to ambient temperature of 32°C and relative humidity of 35 % . ω ambient = 0.01039 kg / kg dry air Refer Figure A-31, “Psychrometric chart at 1 atm total pressure”, and write the humidity ratio of room corresponding to ambient temperature of 24°C and relative humidity of 55 % . ω room = 0.01024 kg / kg dry air Substitute 101 .325 kPa for P 0 , 0.2870 kPa ⋅ m 3 / kg ⋅ K for R and 32°C for T 0 in Equation (I). ρ ambient = 101 .325 kPa ( 0.2870 kPa ⋅ m 3 / kg ⋅ K ) ( 32°C ) = 101 .325 kPa ( 0.2870 kPa ⋅ m 3 / kg ⋅ K ) ( 32 + 273 ) K = 101 .325 kPa ( 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 58P

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Sensible, latent, and total infiltration heat load of a building at sea level.

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Chapter 14.7, Problem 57P

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Chapter 14 Solutions

Thermodynamics: An Engineering Approach

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Sensible, latent, and total infiltration heat load of a building at sea level.

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