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Question: the air temperature in a room is maintained at 20c...

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The air temperature in a room is maintained at 20°C year-round, but the wall temperature is approximately 27°C in the summer and 14°C in the winter. Determine the rates of heat transfer from a person in this room in both winter and summer if the exposed surface area, emissivity, convection coefficient, and the average outer surface temperature of the person are 1.8 m2, 0.8, 4 W/m2-K, and 31 °C, respectively. 4. You carelessly leave a carton of milk outside of the refrigerator on the counter for 10 minutes. The temperature of the milk is the refrigerator is 3°C, and the room on a hot day is 5. at a temperature of 30°C. The carton has a total surface area of 0.10 m2, and the heat transfer coefficient on its surface is 12 W/m2-K. The emissivity of the carton is 0.9. Assume the surface temperature of the milk carton stays at 3°C over the entire 10 minutes (this will give the highest possible estimate of heat gain) (a) Calculate the total amount of heat transfer from the room to the carton. (b) Determine the cost to remove this heat from the milk once back in the refrigerator if the COP of the refrigerator is 2.5 and the electricity cost is $0.10/kWh.
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