A solid sphere of radius R= 8.0 cm uniformly generates 5 x 10 W/m' of heat within it. Surrounding the sphere is still air where h = 10 W/m²-K and T = 20°C. The sphere is surrounded by an enclosure at 0°C. If the emissivity of the sphere is ɛ = 0.85, calculate the surface temperature of the sphere.
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- A large steam pipe is covered with a 4.80 cm thick insulating material with a thermal conductivity of 0.17 W/(m°C). How much energy is lost every second when the temperature of the steam inside the pipe is at 265 °C and the temperature outside of the pipe is 13.0 °C? The pipe has a diameter of 3.70 m and a length of 185 m. Neglect losses through the ends of the pipe. 3863.3 JA large cylindrical coffee pot in a coffee shop filled with 10.0 kg of hot coffee at temperature T = 95.0 ° C rests on a wooden table. The steel pot has radius r = 8.00 cm and height h = 50.0 cm and an emissivity e = 0.600. See figure. Assume that all heat loss is radiative through the side and top of the pot, given that wood is a relatively poor thermal conductor. The coffee shop ambient temperature T = 20.0 ° C. a) Find the rate at which the coffee losses heat. b) Assuming constant heat loss rate, what is the coffee temperature after 10.0 minutes have elapsed? Cw = 4.19 x 103 J/kg °C, ρw = 1.00 x 103 kg/m3, σ = 5.67 x 10 -8 W/m2 K4Ice of mass 10.0 kg at 0.00° C is placed in an ice chest. The ice chest has 2.00 cm thick walls of thermal coductivity 1.00 x 10^-5 kcal/s-m-C° and a surface area of 1.30m^2. (a) How much heat must be absorbed by the ice before it melts? (b) If the outer surface of the ice chest is at 30.0° C, how long will it take for the ice to melt?
- The thermal conductivities of human tissues vary greatly. Fat and skin have conductivities of about 0.20 W/m · K and 0.020 W/m · K respectively, while other tissues inside the body have conductivities of about 0.50 W/m · K. Assume that between the core region of the body and the skin surface lies a skin layer of 1.0 mm, fat layer of 0.50 cm, and 3.2 cm of other tissues. (a) Find the R-factor for each of these layers, and the equivalent R-factor for all layers taken together, retaining two digits. Rskin m2 · K/W Rfat m2 · K/W Rtissue m2 · K/W R m2 · K/W (b) Find the rate of energy loss when the core temperature is 37°C and the exterior temperature is 0°C. Assume that both a protective layer of clothing and an insulating layer of unmoving air are absent, and a body area of 2.0 m2. WA rod made of glass has a circular cross section with a diameter of 0.1200 m at a temperature of 20 degrees celsius. An aluminum ring has a diameter of 0.1196 m at a temperature of 20 degrees celsius. The coefficients of thermal expansion for glass and aluminum are 9.0 x 10-6 1/K and 24.0 x 10-6 1/K, respectively. At what temperature will the aluminum ring be able to slip over the glass rod? Between 225 and 250 degrees celsius Between 175 and 200 degrees celsius Between 100 and 125 degrees celsius Higher than 300 degrees celsius Between 250 and 275 degrees celsius Between 125 and 150 degrees celsius Between 275 and 300 degrees celsius Between 150 and 200 degrees celsius O Between 200 and 225 degrees celsiusFor heat transfer purposes, a standing man can be modeled as a 30-cmdiameter, 170-cm-long vertical cylinder with both the top and bottom surfaces insulated and with the side surface at an average temperature of 34°C. For a convection heat transfer coefficient of 15 W/m2 · °C, determine the rate of heat loss from this man by convection in an environment at 0°C.