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A black wood stove with surface area 4.6 nr is made from cast iron 4.0 mm thick. Its interior wall is at 650°C, while the exterior is at 647°C. (a) What’s the rate of heat
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- An aluminum rod 0.500 m in length and with a cross-sectional area of 2.50 cm2 is inserted into a thermally insulated vessel containing liquid helium at 4.20 K. The rod is initially at 300 K. (a) If one-half of the rod is inserted into the helium, how many liters of helium boil off by the time the inserted half cools to 4.20 K? Assume the upper half does not yet cool. (b) If the circular surface of the upper end of the rod is maintained at 300 K, what is the approximate boil-off rate of liquid helium in liters per second after the lower half has reached 4.20 K? (Aluminum has thermal conductivity of 3 100 W/m K at 4.20 K; ignore its temperature variation. The density of liquid helium is 125 kg/m3.)arrow_forwardFor the human body, what is the rate of heat transfer by conduction through the body's tissue with the following conditions: the tissue thickness is 3.00 cm, the difference in temperature is 2.00 , and the skin area is 1.50 m2. How does this compare with the average heat transfer rate to the body resulting from an energy intake of about 2400 kcal per day? (No exercise is included.)arrow_forward(a) What is the rate of heat conduction through the 3.00-cm-thick fur of a large animal having a I .40-m surface area? Assume that the animal's skin temperature is 32.0 , that the air temperature is 5.00 , and that has the same thermal conductivity as air. (b) What food intake will the animal need in one day to replace this heat transfer?arrow_forward
- During the winter, the inside of an average house is maintained at 20 °C, while the outside temperature is 0 °C. Assuming that the only mechanism of heat transfer is conduction, the walls are 10 cm thick and the heatconductivity of the walls is 0.5 W/(Km). a) Calculate the heat flux from the room to the surroundings in W/m2. b) To reduce the heat loss through the walls, the material should be changed to an insulator material. Thenew overall conductivity will be 0.1 W/(Km); the thickness of the walls is maintained. Calculate the reductionof the heat flux through the walls compared to the initial case.arrow_forwardA Thermopane window of area 5 m² is con- structed of two layers of glass, each 4.4 mm thick separated by an air space of 3 mm. If the inside is at 11°C and the outside is at -24°C, what is the heat loss through the window? The thermal conductivity of glass is 0.8 W/m .° C and of air is 0.0234 W/m .° C. Answer in units of kW.arrow_forwardA homeowner is unhappy with her heating costs. One wall of her house is 4 meters tall and 8 meters wide and has no windows, and it is made of brick and mortar with a thermal conductivity of 1.0 W m K . It is 40 cm thick. The house is heated to a temperature of 20 ◦C inside. (a) What is the rate of heat loss through the wall on a day when it is 0◦C outside? (b) A layer of rock mineral wool, which has a thermal conductivity of 0.032 W m K is to be installed on the interior surface of the brick wall. How thick should the layer be to lower the rate of heat transfer through this wall to half its original value? (c) If the rock mineral wool is instead installed on the outer surface, is the thickness required the same?arrow_forward
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