An industrial spherical oven has 2.8 m diameter. It is placed in a factory floor where the air temperature is 25°C and surrounding temperature is 30°C. When the oven is running under part-load condition the temperature of the outer surface of the oven is 60°C and under peak load conditions the surface temperature reaches to 250°C. The total heat loss from the oven under peak-load conditions was found to be 905 kW. The emissivity of the oven surface is 0.75. Find the convection coefficient of air around the oven in this condition. 150.76 W/m2K

An industrial spherical oven has 2.8 m diameter. It is placed in a factory floor where the air temperature is 25°C and surrounding temperature is 30°C. When the oven is running under part-load condition the temperature of the outer surface of the oven is 60°C and under peak load conditions the surface temperature reaches to 250°C. The total heat loss from the oven under peak-load conditions was found to be 905 kW. The emissivity of the oven surface is 0.75. Find the convection coefficient of air around the oven in this condition. 150.76 W/m2K

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.

Chapter11: Heat Transfer By Radiation

Section: Chapter Questions

Problem 11.42P: Three thin sheets of polished aluminum are placed parallel to each other so that the distance...

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Three thin sheets of polished aluminum are placed parallel to each other so that the distance between them is very small compared to the size of the sheets. If one of the outer sheets is at 280C and the other outer sheet is at 60C, calculate the temperature of the intermediate sheet and the net rate of heat flow by radiation. Convection can be ignored.
An electronic box that consumes 200 W of power is cooled by a fan blowing air into the box enclosure. The dimensions of the electronic box are 15 cm * 50 cm * 50 cm, and all surfaces of the box are exposed to the ambient except the base surface. Temperature measurements indicate that the box is at an average temperature of 32°C when the ambient temperature and the temperature of the surrounding walls are 25°C. If the emissivity of the outer surface of the box is 0.75, determine the fraction of the heat lost from the outer surfaces of the electronic box.
Consider a person who is trying to keep cool on a hot summer day by turning a fan on and exposing his body to air flow. The air temperature is 32°C, and the fan is blowing air at a velocity of 5 m/s. The surrounding surfaces are at 40°C, and the emissivity of the person can be taken to be 0.9. If the person is doing light work and generating sensible heat at a rate of 90 W, determine the average temperature of the outer surface (skin or clothing) of the person. The average human body can be treated as a 30-cmdiameter cylinder with an exposed surface area of 1.7 m2. Evaluate the air properties at film temperature of 35°C and 1 atm.
Determine the heat flow between the roof and floor of 4 x 3 m size of a furnace of 4 m x 4 m x 3 m size when the roof is at 1200 K and the floor is maintained at 600 K, with the other surfaces non absorbing and reradiating. The surface emissivity of the hotter surface is 0.8 and that of the cooler surface 0.6
Consider a thin 16-cm-long and 20-cm-wide horizontal plate suspended in air at 20°C. The plate is equipped with electric resistance heating elements with a rating of 20 W. Now the heater is turned on and the plate temperature rises. Determine the temperature of the plate when steady operating conditions are reached. The plate has an emissivity of 0.90 and the surrounding surfaces are at 17°C. As an initial guess, assume a surface temperature of 50°C. Is this a good assumption?
Two very large walls are at constant temperature of 658oF and 856oF. Assuming that the walls behave like black bodies, how much heat in Btu/hr-ft2 must be removed from the colder wall in order to maintain a constant pressure (σ=0.1714x10-8 Btu/hr-ft2-R)
Two concentric spheres of diameters D1 = 15 cm and D2 = 25 cm are separated by air at 1 atm pressure. The surface temperatures of the two spheres enclosing the air are T1 = 350 K and T2 = 275 K, respectively, and their emissivities are 0.75. Determine the rate of heat transfer from the inner sphere to the outer sphere by (a) natural convection and (b) radiation.
A hot liquid is filled in a spherical tank with an inner diameter of 3 m and a wall thickness of 3 cm. The tank wall is made of a material with a thermal conductivity of 0.15 W/m∙K.The hot liquid in the tank causes the inner surface temperature to be 100°C, while the tank outer surface is exposed to air at 20°C and has an emissivity of 0.35. Determine the outer surface temperature of the tank. Assume that the properties of air can be evaluated at 40°C and 1 atm pressure. Is this a good assumption?
An astronaut performing an extra-vehicular activity(space walk) shaded from the Sun is wearing a spacesuitthat can be approximated as perfectly white (e = 0) exceptfor a 5 cm × 8 cm patch in the form of the astronaut’snational flag. The patch has emissivity 0.300. The spacesuitunder the patch is 0.500 cm thick, with a thermalconductivity k = 0.0600 W/m °C , and its inner surface isat a temperature of 20.0 °C . What is the temperature of thepatch, and what is the rate of heat loss through it? Assumethe patch is so thin that its outer surface is at the sametemperature as the outer surface of the spacesuit under it.Also assume the temperature of outer space is 0 K. You willget an equation that is very hard to solve in closed form,so you can solve it numerically with a graphing calculator,with software, or even by trial and error with a calculator.