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# ps4 - assumed perfectly insulated(1 The emissivity of all...

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ME 322 PS #4 14/15 May 2008 1. A disk of 50 cm in diameter is attached to the side of a spaceship in such a way that it is perfectly insulated from the inside of the spaceship. One side of the plate is exposed to the radiant heat flux of 1400 W/m 2 and the other side is insulated. The emissivity of the plate is 0.6 and the gray-body behavior can be assumed. Assuming that outer space is a blackbody at 0 K, determine the equilibrium temperature for the plate. 2. Two large parallel planes having emissivities of 0.3 and 0.5 are maintained at temperatures of 800 K and 400 K, respectively. A radiation shield having an emissivity of 0.05 on both sides is placed between the two planes. (1) Calculate the heat-transfer rate per unit area if the shield were not present. (2) Calculate the heat-transfer rate per unit area with the shield present. (3) Calculate the temperature of the shield. 3. A cubic room of 3 3 3 × × m has a floor heated to 300 K, a ceiling at 290 K and sidewalls that are
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Unformatted text preview: assumed perfectly insulated. (1) The emissivity of all surfaces is 0.8. Find the sidewall temperature. (2) If all surfaces are of blackbody, what will be the sidewall temperature? 4. A “focusing” radiation heater is constructed as shown with the hot surface at 1000ºC having an emissivity of 0.55 and a diameter of 0.5 m. The walls surrounding the heater surface are insulated and have the emissivity of 0.4. The depth of the wall is 0.5 m. The arrangement is open to a large room at 20ºC. Calculate the heat transfer to the room. Room at 20ºC 0.5 m in depth D = 0.5 m insulated Heater at 1000ºC 5. A horizontal metal thermocouple with a diameter of 3 mm and an emissivity of 0.6 is inserted in a duct to measure the temperature of an airstream flowing at 7 m/s. The walls of the duct are 400ºC, and the thermocouple indicates a temperature of 100ºC. (1) Calculate the convection heat transfer coefficient. (2) Find the true gas temperature....
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