3-68 A 5-m-wide, 4-m-high, and 40-m-long kiln used to cure concrete pipes is made of 20-cm-thick concrete walls and ceiling (k = 0.9 W/m-K). The kiln is maintained at 40°C by injecting hot steam into it.The two ends of the kiln, 4 m x 5 m in size, are made of a 3-mm-thick sheet metal covered with 2-cm-thick Styrofoam (k = 0.033 W/m K). The convection heat transfer coefficients on the inner and the outersurfaces of the kiln are 3000 W/m2-K and 25 W/m2-K, respectively. Disregarding any heat loss through the floor, determine the rate of heat loss from the kiln when the ambient air is at -4°C.FIGURE P3-68Tout-4°C40 mTin=40°C4 m20 cm5 m

The following data have been given to us.The length of the kiln, L = 40 m.The breadth of the kiln, B…

Answered: 3-68 A 5-m-wide, 4-m-high, and…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

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A 5-m-wide, 4-m-high, and 40-m-long kiln used to cure concrete pipes is made of 20-cm-thick concrete walls and ceiling (k = 0.9 W/m• °C). The kiln is maintained at 40°C by injecting hot steam into it. The two ends of the kiln, 4 m x 5 m in size, are made of a 3-mm-thick sheet metal covered with 2-cm-thick Styrofoam (k = 0.033 W/m °C). The convection heat transfer coefficients on the inner and the outer surfaces of the kiln are 3000 W/m²-°C and 25 W/m2-°C, respectively. Disregarding any heat loss through the floor, determine the rate of heat loss from the kiln when the ambient air is at -4°C. ANSWER:________W
Example 9: A 2-kW resistance heater wire whose thermal conductivity is k = 15 W/m ·°C has a diameter of D = 4 mm and a length of L = 0.5 m, and is used to boil water. If the outer surface temperature of the resistance wire is Ts = 105°C, determine the temperature at the center of the wire.
Question -) Consider a stainless steel spoon (k = 15 W/m·K) partially immersed in boiling water at 95°C in a kitchen at 25°C. The handle of the spoon has a cross section of 0.2cm x 1.2 cm, and extends 18 cm in the air from the free surface of the water. If the heat transfer coefficient at the exposed surfaces of the spoon handle is 15 W/m2·°C, determine the temperature difference across the exposed surface of the spoon handle. State your assumptions.
The 8-mm-thick bottom of a 220-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. If heat is transferred from the stove to the pan at a rate of 600 W, what is the temperature of the surface in contact with the stove for each of the two materials?
The cylinders that come out of the heat treatment furnace are cooled in a stagnant air environment in a horizontal position. The cylinders have a diameter of 100 mm and a length of 0.1 m. The temperature of the cylinders is 440 ° C and the ambient temperature is 20 ° C. Calculate the heat transfer from 10 cylinders to the environment. a) 3125 W b) 2350 W C) 1848 W d) 1354 W e) 2750 W
Consider water (at a temperature of 276 K ) flowing inside a cylindrical pipe, having a diameter of 0.1 m and a thin wall. Under specific circumstances, temperature at the wall of the pipe reaches 258 K that helps form a layer of ice on the inner side of the wall of the pipe. Temperature and convection heat transfer coefficient at the inner surface of the ice layer are 273 K and 1500m2⋅Kw, respectively. Determine how thick the ice layer should be?
Consider hotdog being cooked in boiling water in a pan. Would the heat transfer be modeled as one-dimensional or two-dimensional? Would the heat transfer be steady or transient? Explain.
A 5-m-wide, 4-m-high, and 40-m-long kiln used to cure concrete pipes is made of 20-cm-thick concrete walls and ceiling (k = 0.9 W/m · °K). The kiln is maintained at a surface temperature of 40°C. Determine the rate of heat loss from the kiln when the outside surface temperature is -4°C
A cylindrical body having 10 cm diameter and lenth of 30 cm passes through a heat treatment furnace which is 6 m in length. The body must reach a temperature of 800°C before it comes out of the furnace. The furnace gas is at 1250°C and body initial temperature is 90°C. How much time it will take to attain the required temperature ? Take h = 100 W/m² °C. Take K(steel) = 40 W/m°C and a (thermal diffusivity of steel) = 1.16 x 10-5 m²/s.
During a picnic on a hot summer day, the only available drinks were those at the ambient temperature of 90°F. In an effort to cool a 12-fluid-oz drink in a can, which is 5 in high and has a diameter of 2.5 in, a person grabs the can and starts shaking it in the iced water of the chest at 32°F. The temperature of the drink can be assumed to be uniform at all times, and the heat transfer coefficient between the iced water and the aluminum can is 30 Btu/h·ft2·°F. Using the properties of water for the drink, estimate how long it will take for the canned drink to cool to 40°F.
/ Hot square plate (1 m ×1 m) is to be cooled by attaching aluminum circular pin fins (D=0.25 cm, L= 3 cm) distributed with distance 0.6 cm as illustrated in Figs.(1-a) & (1-b). If the fin base temperature is 100°C, cooling air temperature is 30°C and h= 35 W/m. °C. Determine the total rate of heat transfer from the finned plate and the effectiveness of the fins? Assume k= 237 W/m.°C and nr=tanh mL/ mL.
A 3 – m high and 5 – m wide wall consists of 16 – cm by 22 – cm cross section horizontalbricks (k = 0.72 W/m – K) separated by 3 – cm thick plaster layers (k = 0.22 W/m – K).There are also 2 – cm thick plaster layers on each side of the brick and a 3 – cm thickrigid foam (k = 0.026 W/m – K) on the inner side of the wall. The indoor and outdoortemperatures are 20 oC and -10 oC, respectively and the convection heat transfercoefficients on the inner and outer sides are h1 = 10 W/m2 – K and h2 = 25 W/m2 – K,respectively. Assuming one – dimensional heat transfer and disregarding radiation,determine the rate of heat transfer through the wall.

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