The net radiant-heat exchange between a 20-by-20 ft rough plaster panel-heated ceiling and a 20-by-10-ft side wall, which has an emissivity of 0.80, is 2400 Btu/hr. If the surface temperature of the ceiling is 120 deg. F, determine the average surface temperature of the side wall.

The net radiant-heat exchange between a 20-by-20 ft rough plaster panel-heated ceiling and a 20-by-10-ft side wall, which has an emissivity of 0.80, is 2400 Btu/hr. If the surface temperature of the ceiling is 120 deg. F, determine the average surface temperature of the side 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

See similar textbooks

Similar questions

Consider a 150 W incandescent lamp in a room at 25 °C. The filament of the lamp is 5 cm long and has a diameter of 0.5 mm. The emissivity of the filament is 0.90. The diameter of the glass bulb of the lamp is 8 cm. The inside surface temperature of the glass bulb is 150 °C. Determine: (a) the heat flux, in W∙m-2, on the surface of the filament, (b) the heat flux, in W∙m-2, on the surface of the glass bulb, and (c) the surface temperature of the filament. The surface area of a sphere is ? = 4??2, and the volume of a sphere is ? = (4?/3)?3.
Consider a furnace (as a plane wall) which has a thickness of 15 cm and a surface area of 1 m?. The inside surface of the furnace wall (the hot left side of the wall) is at temperature T1. The furnace wall is made of brick with thermal conductivity of 1.198 W/m.K. The outside surface of the furnace wall (the right side of the wall) has a surface emissivity of 0.8 and is maintained at T2=101 °C and subject to air at 25 °C with convection heat transfer coefficient of 20 W/m?.K. The surroundings temperature at the outside of the furnace wall is at 25 °C. Required: Draw a clear and consistent schematic of the problem and label the operating conditions on the schematic. Perform systematic analysis, state your assumptions and justify the equation used and determine the following (circle your final answers): (i) The rate of heat transfer by convection (in W); (ii) The rate of heat radiation (in W); (iii) The surface temperature of the furnace wall T1 (in °C); (iv) The rate of conduction heat…
H.W1 Consider a person standing in a room. Determine the total rate of heat transfer from this person if the exposed surface area and temperature are 1.6m² and 29°C, respectively. Assume that the convection heat transfer coefficient is 6W/m².K and the emissivity of a person is 0.95. The air temperature in the room is maintained at 22°C at all times of the year. In summer, the wall and ceiling temperatures are observed to be 25°C, while in winter, they are 10°C. Ans: Qrotal =104.4 W In Summer Qrotal =231.3 W In Winter
An ice chest whose outer dimensions are 30 cm*40 cm*40 cm is made of 3 cm thick Styrofoam (k = 0.033 W/m°C). Initially, the chest is filled with 30 kg of ice at 0 °C, and the inner surface temperature of the ice chest can be taken to be 0 °C at all times. The heat of fusion of water at 0 °C is 333.7 kJ/kg, and the surrounding ambient air is at 20 °C. Disregarding any heat transfer from the 40 cm*40 cm base of the ice chest, determine how long it will take for the ice in the chest to melt completely if the ice chest is subjected to (a) calm air and (b) winds at 30 km/h (assume the heat transfer coefficient on the front, back and top surfaces to be the same as that on the side surfaces). Use the thermophysical properties of air as follows: k = 25.5×10-3 W/mK, ν = 15×10-6 m2/s, α = 21.1×10-6 m2/s, and β = 3.43×10-3 K-1.
Water is to be heated from 15°C to 65°C as it flows through a 3-cm-internaldiameter 5-m-long tube . The tube is equipped with an electric resistance heater that provides uniform heating throughout the surface of the tube. The outer surface of the heater is well insulated, so that in steady operation all the heat generated in the heater is transferred to the water in the tube. If the system is to provide hot water at a rate of 10 L/min, determine the power rating of the resistance heater. Also, estimate the inner surface temperature of the tube at the exit.
Consider a hot automotive engine, which can be ap- proximated as a 0.5-m-high, 0.40-m-wide, and 0.8-m-long rec- tangular block. The bottom surface of the block is at a temperature of 80°C and has an emissivity of 0.95. The ambi- ent air is at 20°C, and the road surface is at 25°C. Determine the rate of heat transfer from the bottom surface of the engine block by convection and radiation as the car travels at a veloc- ity of 80 km/h. Assume the flow to be turbulent over the entire surface because of the constant agitation of the engine block.
A pipe in a manufacturing plant is transporting superheated vapor at a mass flow rate of 0.3 kg/s. The pipe is 10 m long, has an inner diameter of 5 cm and pipe wall thickness of 6 mm. The pipe has a thermal conductivity of 17 W/m.K, and the inner pipe surface is at a uniform temperature of 120 °C. The temperature drop between the inlet and the exit of the pipe is 7 °C, and the constant pressure specific heat of vapor is 2190 J/kg.°C. If the air temperature in the manufacturing plant is 25°C, determine the heat transfer coefficient as a result if convection between the outer pipe surface and the surrounding air. T(r) = 120°C Superheated Air, 25°C r2 vapor r1 0.3 kg/s L = 10 m Tin-Tout = 7°C
A horizontal pipe with a diameter of 18 cm and a length of 10 m, which contains hot oil and has a surface temperature of 383.8 ° C, has an atmospheric pressure of 760 mm Hg. It is located in an environment (open air) where the temperature is 25 °C. Determine the rate of heat transfer from the pipe to the air (the heat transferred by radiation will be neglected).
Solar radiation is incident on the glass cover of a solar collector at a rate of 700W/m². The glass of collector absorbs 88 percent of the incident radiation on it and has an emissivity of 0.9. The entire hot water needs of a family can be provided by a single collector of 1.2m height and 2m width. The temperature of the glass cover of the collector is measured to be 35C° on a day when the surrounding air temperature is 25C° and the wind is blowing at 30km/h. The effective sky temperature for radiation exchange between the glass cover and the open sky is -40C°. Water enters the tubes which attached to the absorber plate at a rate of 1kg/min. Assuming the back surface of the absorber plate to be heavily insulated and the only heat loss to occur through the glass cover, determine (a) the total rate of heat loss from the collector, (b) the collector efficiency, which is the ratio of the amount of heat transferred to the water to the solar energy incident on the collector, and (c) the…
An electric device made of copper stands on an insulating carpet in a breezy room at 20°C. A fan is set in the room to ensure a continuous air circulation. Determine the total rate of heat transfer from the device if the average values of its exposed surface area and outer surface temperature are 2.5 m² and 30°C, respectively.