The composite wall of a building consists of a 100 mm layer of common brick, a 100 mm layer of glass fibre (organic bonded), a 10 mm layer of gypsum plaster (perlite aggregate) and a 6 mm of pine panel. If the inside convection coefficient is 10 W/m²K and the outside convection coefficient is 70 W /m².K, calculate: O The total themal resistance of the wall; (1The overall heat transfer coefficient of the wall.

The composite wall of a building consists of a 100 mm layer of common brick, a 100 mm layer of glass fibre (organic bonded), a 10 mm layer of gypsum plaster (perlite aggregate) and a 6 mm of pine panel. If the inside convection coefficient is 10 W/m²K and the outside convection coefficient is 70 W /m².K, calculate: O The total themal resistance of the wall; (1The overall heat transfer coefficient of the wall.

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.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.53P: Determine the power requirement of a soldering iron in which the tip is maintained at 400C. The tip...

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1.1 On a cold winter day, the outer surface of a 0.2-m-thick concrete wall of a warehouse is exposed to temperature of –5°C, while the inner surface is kept at 20°C. The thermal conductivity of the concrete is 1.2 W/m K. Determine the heat loss through the wall, which is 10-m long and 3-m high. Problem 1.1
1.4 To measure thermal conductivity, two similar 1-cm-thick specimens are placed in the apparatus shown in the accompanying sketch. Electric current is supplied to the guard heater, and a wattmeter shows that the power dissipation is 10 W. Thermocouples attached to the warmer and to the cooler surfaces show temperatures of 322 and 300 K, respectively. Calculate the thermal conductivity of the material at the mean temperature in W/m K. Problem 1.4
2.3 The shield of a nuclear reactor is idealized by a large 25-cm-thick flat plate having a thermal conductivity of . Radiation from the interior of the reactor penetrates the shield and there produces heat generation that decreases exponentially from a value of at the inner surface to a value of at a distance of 12.5 cm from the interior surface. If the exterior surface is kept at 38°C by forced convection, determine the temperature at the inner surface of the field. Hint: First set up the differential equation for a system in which the heat generation rate varies according to .
Determine the power requirement of a soldering iron in which the tip is maintained at 400C. The tip is a cylinder 3 mm in diameter and 10 mm long. The surrounding air temperature is 20C, and the average convection heat transfer coefficient over the tip is 20W/m2K. The tip is highly polished initially, giving it a very low emittance.
Calculate the thickness of the magnesia insulation necessary to restrict the heat loss to 5 BTU/hr-ft2 through the walls of a furnace having inside and ambient temperatures of 1500 oF and 150 oF, respectively. The furnace wall is ¼ in, steel plate and 3 in refractory lining. Thermal conductivity in BTU/hr –ft-oF are kref = 0.6, ksteel = 26, kmag=0.03
An insulated steam pipe passes through a room in which the air and walls are at 25°C. The outside diameter of pipe is 70 mm, and its surface temperature and emissivity are 200°C and 0.80, respectively. If the free convection coefficient from the surface to the air is 15 W/m2-K, what is the rate of heat loss from the surface per unit length of pipe?
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A steel pipe (K=45.0 W/mK) having a 0.05m O.D.is covered with a 0.042 m thick layer ofmagnesia (K =0.07W/mK) which in turn coveredwith a 0.024 m layer of fiberglass insulation(K=0.048 W/mK). The pipe wall outsidetemperature is 370K and the outer surfacetemperature of the fiberglass is 305K. What isthe interfacial temperature between the magnesia and fiberglass? also calculate thesteady state heat transfer.
Show the thermal circuit by labeling all the thermal resistances. Calculate and tabulate the thermal resistances (assume Tavg=470 K for the air gaps). If q''rad= 0.25W/cm^2, what is the outer surface temperature of turnout coat for inner temperature of 66C.
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