Electrically heated draw batch furnaces are commonly used in the heat treatment industry. Consider a draw batch furnace front made of a 20-mm thick steel plate with a ther- mal conductivity of 25 W/m-K. The furnace is situated in a oom with surrounding air temperature of 20°C and an aver- age convection heat transfer coefficient of 10 W/m2-K. If the nside surface of the furnace front is subjected to uniform neat flux of 5 kW/m² and the outer surface has an emissiv- ty of 0.30, determine the inside surface temperature of the furnace front. T = 20°C Furnace front to = 5 kW/m² Air, 20°C h = 10 W/m K e = 0.30 k= 25 W/m-K To

Electrically heated draw batch furnaces are commonly used in the heat treatment industry. Consider a draw batch furnace front made of a 20-mm thick steel plate with a ther- mal conductivity of 25 W/m-K. The furnace is situated in a oom with surrounding air temperature of 20°C and an aver- age convection heat transfer coefficient of 10 W/m2-K. If the nside surface of the furnace front is subjected to uniform neat flux of 5 kW/m² and the outer surface has an emissiv- ty of 0.30, determine the inside surface temperature of the furnace front. T = 20°C Furnace front to = 5 kW/m² Air, 20°C h = 10 W/m K e = 0.30 k= 25 W/m-K To

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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An industrial freezer is designed to operate with an internal air temperature of -20°C when the external air temperature is 27°C, and the internal and external heattransfer coefficients are 8 W/m2 -K and 12 W/m2 -K, respectively. The walls of thefreezer are composite construction, comprising an inner layer of plastic (k = 0.33 W/m-K, and thickness of 10 mm), and an outer layer of stainless steel (k = 15 W/m-K, and thickness of 3 mm). Sandwiched between these two layers is a layer of insulation material with k = 0.07 W/m-K. Find the width (mm) of the insulation thatis required to reduce the convective heat loss to 60 W/m2.
The wall of a furnace consists of a 0.85 cm-thick layer of steel (ks = 15.1 W/m/K) and an outer layer of brick (kb = .72 W/m/K). The outer surface temperature of the brick, To = 50oC, and is exposed to convection with air at 20oC providing a heat transfer coefficient of 150 W/m^2/K. Determine the steady temperature at the steel brick interface, Tmid, and on the exposed steel surface, Ti, if the brick layer has thickness Lb = 5 cm.
Q) An apple has been put into a freezer at (-18°C) to be cooled. Initially, the apple is at a uniform temperature of 17°C. The convection heat transfer coefficient on its surface is 6 W/m2°C. Assuming the apple as a sphere having a diameter of 10-cm and taking its properties as p = 750 kg/m³, p = 2850 J/kg°c, and k = 0.450 W/m°C, determine; (a) the center temperature of the apple in 45 minutes, (b) the actual amount of heat transfer from the apple, and (c) the final equilibrium temperature of the apple. Hint: consider the temperature is a function of location and time.
A pipe carrying hot gasses is insulated with a material having a thermal conductivity of 0.15 W/mK. The average local heat transfer coefficient by convection to the ambient air is 3 W/m K. The critical diameter of the pipe under 35. these conditions is (a) 100 mm (c) 160 mm (b) 130 mm (d) 200 mm
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The 10-mm-thick bottom of a 200-mm-diameter pan may be made from aluminum (k = 240 W/m-K) or copper (k = 390 W/m-K). When used to boil water, the surface of the bottom exposed to the water is nominally at 110°C and heat is transferred from the stove to the pan at a rate of 1200 W. What is the temperature of the surface in contact with the stove for each of the two materials? Aluminum: T = i °C Copper: T = °C Physical Properties Mathematical Functions
The thermal conductivity of a solid material can be determined using asetup similar to the one shown in the accompanying figure. The thermocouples are placed at 2.5 cm intervals in the known material (copper alloy, k - 52 w/m.k) and the unknown sample, as shown. The known material is heated on the top by a heating element, and the bottom surface of the sample is cooled by running water through the heat sink shown. Determine the thermal conductivity of the unknown sample for the set of data given in the accompanying table. Assume no heat loss to the surroundings and perfect thermal contact at the common interface of the sample and the copper.
A furnace wall comprises three layers of thickness 250 mm, 100 mm, and 150 mm with thermal conductivities of 1.65, k and 9. W/m K respectively. The inside is exposed to gases at 1250 ˚C with convection of 25 W/m2K, and the inside surface is at 1100 ˚C, the outside surface air at 25 ˚C with convection of 12 W/m2K. Determine the temperatures of the mid-inner surface in 0C to 1 d.p.?