2. The cabin air in an empty aircraft on the ground in a tropical country is maintained at a constant 21°C (=T) by air-conditioning when the outside temperature is 35°C (=Ta). The radius of the fuselage is 3.7m (=r), the thermal conductivity of the cabin wall is 0.4 W/m.K (=k)and the heat transfer coefficients are 9 (=h) and 39 (=ha) W/m.K for the air in the cabin and the external atmosphere respectively. Assume that the effects of radiation are negligible. (a) Draw a sketch of the fuselage showing the dimensions, heat transfers, temperatures as well as the values of thermal conductivity and heat transfer coefficients. Identify the types of heat transfer occurring and express them in terms of the appropriate temperatures and constants of proportionality. Identify the relationships between the temperature differences associated with the heat transfers; and, hence show that the heat transfer unit length of fuselage (b) (c) is (Ta-Te) = = 2ar: Aha'k'hc If the air-conditioning unit is 50% efficient and the fuselage is 40m long and its wall thickness is 0.1m, then how much power is required to maintain these conditions? (d) [Answer: 43.3 kW]

2. The cabin air in an empty aircraft on the ground in a tropical country is maintained at a constant 21°C (=T) by air-conditioning when the outside temperature is 35°C (=Ta). The radius of the fuselage is 3.7m (=r), the thermal conductivity of the cabin wall is 0.4 W/m.K (=k)and the heat transfer coefficients are 9 (=h) and 39 (=ha) W/m.K for the air in the cabin and the external atmosphere respectively. Assume that the effects of radiation are negligible. (a) Draw a sketch of the fuselage showing the dimensions, heat transfers, temperatures as well as the values of thermal conductivity and heat transfer coefficients. Identify the types of heat transfer occurring and express them in terms of the appropriate temperatures and constants of proportionality. Identify the relationships between the temperature differences associated with the heat transfers; and, hence show that the heat transfer unit length of fuselage (b) (c) is (Ta-Te) = = 2ar: Aha'k'hc If the air-conditioning unit is 50% efficient and the fuselage is 40m long and its wall thickness is 0.1m, then how much power is required to maintain these conditions? (d) [Answer: 43.3 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.

Chapter7: Forced Convection Inside Tubes And Ducts

Section: Chapter Questions

Problem 7.21P

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