Q1: A house has a composite wall of wood, fiberglass insulation, and plaster board, as indicated in the sketch. On a cold winter day the convection heat transfer coefficients are ho3D60 W/m2. C and h; = 30 W/m2. °C. The total wall surface area is 350 m2. Take k= 0.038 W/m. °C, k,= 0.17 W/m. °C, k,= 0.12 W/m. °C, and k= 0.026 W/m. °C. (a) Determine a symbolic expression for the total thermal resistance of the wall, including inside and outside convection effects for the prescribed conditions. (b) Determine the total heat loss through the wall.

Q1: A house has a composite wall of wood, fiberglass insulation, and plaster board, as indicated in the sketch. On a cold winter day the convection heat transfer coefficients are ho3D60 W/m2. C and h; = 30 W/m2. °C. The total wall surface area is 350 m2. Take k= 0.038 W/m. °C, k,= 0.17 W/m. °C, k,= 0.12 W/m. °C, and k= 0.026 W/m. °C. (a) Determine a symbolic expression for the total thermal resistance of the wall, including inside and outside convection effects for the prescribed conditions. (b) Determine the total heat loss through the wall.

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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A pipe with 8 cm internal diameter, 9 cm outer diameter, 2 meter long, thermal conductivity 30W/mK is insulated by glass wool material with which thermal conductivity 0,05W/mK, thickness 4 cm. Internal surface temperature of the pipe T1 is 80°C, surrounding temperature where pipe is located is 20°C, convection heat transfer constant on outer surface of insulation is 25W/m?K. Kpo 30W/mk T.= 20°C h. = 25W/MK 4cm K= 0,05W/mK a. Detemine the heat loss from the pipe to surrounding (W)? b. What is temperature of the surface between glass wooden and pipe (T2)? c. What is critical insulation radius for pipe? Is insulation on the pipe succesful? Explain
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EXAMPLE = wire Consider a long resistance wire of radius ₁ 0.2 cm and thermal conductivity k = 15 W/m . °C in which heat is generated uniformly as a result of resistance heating at a constant rate of g = 50 W/cm3. The wire is embedded in a 0.5-cm-thick layer of ceramic whose thermal conductivity is k = 1.2 W/m °C. If the outer surface temperature of the ceramic layer is measured to be Ts = 45°C, determine the temperatures at the center of the resistance wire and the interface of the wire and the ceramic layer under steady conditions. ceramic 17 Interface Mech. Eng. UOK Wire Ceramic layer T₁=45°C ۳۰/۱۰/۲۰۱۳
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Temp base is 156 not 456 as in the diagram
R8
10.The layout of a wall and the heat transfer parameters are shown in the figure below. Find the internal temperature of the wall, T₁. (o= 5.67 x 10-8 W/m²K4 ) (Ans: 569.5K) T1 k=1.1 W/m.K Icond L=0.12m T2=373K x=0.7 grad Iconv Tsur Air Tex = 300K h = = 290K : 18 W/m².K