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A carpenter builds an exterior house wall with a layer of wood 3.0 cm thick on the outside and a layer of Styrofoam™ insulation 2.2 cm thick on the inside wall surface. The wood has a thermal
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- The surface area of an unclothed person is 1.50 m2, and his skin temperature is 33.0C. The person is located in a dark room with a temperature of 20.0C, and the emissivity of the skin is e = 0.95. (a) At what rate is energy radiated by the body? (b) What is the significance of the sign of your answer?arrow_forwardThe 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 sin face 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. (b) Find the rate of energy loss when the core temperature is 37C and the exterior temperature is 0C. Assume that both a protective layer of clothing and an insulating layer of unmoving air a absent, and a body area of 2.0 m2.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
- A glass windowpane in a home is 0.620 cm thick and has dimensions of 1.00 in 2.00 in. On a certain day, the temperature of the interior surface of the glass is 25.0C and the exterior surface temperature is 0C. (a) What is the rate at which energy is transferred by heat through the glass? (b) How much energy is transferred through the window in one day, assuming the temperatures on the surfaces remain constant?arrow_forwardThe surface area of an unclothed person is 1.50 m2, and his skin temperature is 33.0C. The person is located in a dark room with a temperature of 20.0C, and the emissivity of the skin is e = 0.95. (a) At what rate is energy radiated by the body? (b) What is the significance of the sign of your answer?arrow_forwardWhat is the rate of heat flow through a pane of glass that is 25.0 cm by 100.0 cm with a thickness of 5.00 mm when the outside temperature is - 15.0°C and the inside temperature is 25.0°C? The thermal conductivity of glass is 0.105 W/(m K) and the specific heat of glass is 0.180 cal/(g: °C) O 210 W O 21 W O 2100 W O 360 W O 3600 Warrow_forward
- A carpenter builds a solid wood door with dimensions 2.00 m ×0.95 m × 5.0 cm. Its thermal conductivity is k = 0.120 W/(m⋅K). The air films on the inner and outer surfaces of the door have the same combined thermal resistance as an additional 2.1 cm thickness of solid wood. The inside air temperature is 15.0 ∘C, and the outside air temperature is -8.0 ∘C. What is the rate of heat flow through the door? By what factor is the heat flow increased if a window 0.550 m on a side is inserted in the door? The glass is 0.500 cm, and the glass has a thermal conductivity of 0.80 W/(m⋅K). The air films on the two sides of the glass have a total thermal resistance that is the same as an additional 12.0 cm of glass.arrow_forwardThe exhaust duct from a heater has an inside diameter of 114.3 mm with ceramic walls 6.4 mm thick. The average k = 1.52 W/mK. Outside this wall, an insulation of rock wool 102 mm thick is installed. The thermal conductivity of the rock wool is k = 0.046+1.56*10-4T (°C) (W/mK). The inside surface temperature of the ceramic is T1= 588.7 K, and the outside surface temperature of the insulation is T3= 311 K. Calculate the heat loss for 1.5 m of duct and the interface temperature T2between the ceramic and the insulation.Assumesteady heat transfer.Hint: The correct value of km for insulation is that evaluated at the mean temperature of T2+T3/2. Hence, for the first trial assume a mean temperature of, say, 448 K. Then, calculate the heat loss and T2. Using this new T2, calculate a new mean temperature and proceed as before.arrow_forwardA 0,244 m thick furnace wall is made of material with a thermal conductivity of 1.30 W / m.K. In order for the heat loss from the furnace to be 1130 W / m2, the wall will be insulated from the outside with a material with an average thermal conductivity of k: 0,346 W / m.K. Internal surface temperature is 1588 K and external surface temperature is 219 K. Calculate the required insulation thicknessarrow_forward
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