Consider an apartment in a tower block as a cube of side L = 7.26 m. Since this apartment is designed to be rented by a student, it has no windows. The floor and ceiling are perfectly insulated, but the wall is made of concrete of thickness d = 19.1 cm. The thermal conductivity of the concrete is k = 0.567 Wm¬'K¯!. Part 1) The outside temperature is stable at Tout = 35.6°C. What is the heat load (rate of heat transfer) on the air conditioner if the occupant wants to keep the inside temperature stable at Tn = 20.3°C? P = kW Part 2) A layer of insulation of thickness dins = 30.7 mm and thermal conductivity kins = 0.0105 Wm¬'K¯l is added to the walls. What is the heat load now? P = kW Part 3) The occupant complains that the apartment is dank and dark, so the landlord is forced to install windows and a door. These are constructed, but then drafts from the gaps around the windows and doors allow the air in the apartment to change every 2 hours. How much additional heat load does changing this air add. The specific heat of air is c = 1.0 kJkg¯'K¯ and the density of air is p = 1.0kgm¯* AP = kW

Consider an apartment in a tower block as a cube of side L = 7.26 m. Since this apartment is designed to be rented by a student, it has no windows. The floor and ceiling are perfectly insulated, but the wall is made of concrete of thickness d = 19.1 cm. The thermal conductivity of the concrete is k = 0.567 Wm¬'K¯!. Part 1) The outside temperature is stable at Tout = 35.6°C. What is the heat load (rate of heat transfer) on the air conditioner if the occupant wants to keep the inside temperature stable at Tn = 20.3°C? P = kW Part 2) A layer of insulation of thickness dins = 30.7 mm and thermal conductivity kins = 0.0105 Wm¬'K¯l is added to the walls. What is the heat load now? P = kW Part 3) The occupant complains that the apartment is dank and dark, so the landlord is forced to install windows and a door. These are constructed, but then drafts from the gaps around the windows and doors allow the air in the apartment to change every 2 hours. How much additional heat load does changing this air add. The specific heat of air is c = 1.0 kJkg¯'K¯ and the density of air is p = 1.0kgm¯* AP = kW

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.9P

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