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Suppose you go outside in your fiber-filled jacket on a windless but very cold day. The thickness of the jacket is 2.5 cm, and it covers 1.1 m2 of your body. The purpose of fiber- or down-filled jackets is to trap a layer of air, and it’s really the air layer that provides the insulation. If your skin temperature is 34°C while the air temperature is –20°C, at what rate is heat being
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- An electric kitchen range has a total wall area of 1.40 m2 and is insulated with a layer of fiberglass 4.0 cm thick. The inside surface of the fiberglass has a temperature of 175 degrees C and its outside surface is at 35 degrees C. The fiberglass has a thermal conductivity of 0.040 W/(m*K). What is the heat current through the insulation, assuming it may be treated as a flat slab with an area of 1.40 m2? What electric-power input to the heating element is required to maintain this temperature?arrow_forwardGeologists measure conductive heat flow out of the earth by drilling holes (a few hundred meters deep) and measuring the temperature as a function of depth. Suppose that in a certain location the temperature increases by 20°C per kilometer of depth and the thermal conductivity of the rock is 2.5 W/m·K. What is the rate of heat conduction per square meter in this location? Assuming that this value is typical of other locations over all of earth's surface, at approximately what rate is the earth losing heat via conduction? (The radius of the earth is 6400 km.)arrow_forwardConsider a person standing in a room at 20°C with an exposed surface area of 1.7 m2. The deep body temperature of the human body is 37°C, and the thermal conductivity of the human tissue near the skin is about 0.3 W/m K. The body is losing heat at a rate of 150 W by natural convection and radiation to the surroundings. Taking the body temperature 0,5 cm beneath the skin to be 37°C, determine the skin temperature of the person.arrow_forward
- Q8: Consider a large plane wall of thickness L = 0.3 m, thermal conductivity k = 2.5 W/m - C, and surface area A = 12 m2. The left side of the wall at x =0 is subjected to a net heat flux of qo= 700 W/m2 while the temperature at that surface is measured to be T1 = 80°C. Assuming constant thermal conductivity and no heat generation in the wall, (a) express the differential equation and the boundary conditions for steady one-dimensional heat conduction through the wall, (b) obtain a relation for the variation of temperature in the wall by solving the differential equation, and (c) evaluate the temperature of the right surface of the wall at x = L. Answer: (c) -4°Carrow_forwardThe tube in a heat exchanger has a 2-in inner diameter and a 3-in outer diameter. The thermal conductivity of the tube material is 0.5 Btu/h·ft·°F, while the inner surface heat transfer coefficient is 50 Btu/h·ft2·°F and the outer surface heat transfer coefficient is 10 Btu/h·ft2·°F. Determine the overall heat transfer coefficients based on the outer and inner surfaces.arrow_forwardA ceiling area of 100 square meters consisting of four materials. The thermal insulation value of these materials from top to bottom is (0.6, 50, 0.7 and 0.45) square meters per watt per degree, respectively. If the external temperature is 5 degrees and the internal temperature is 20 degrees, what What is the speed of heat transfer through the wall?arrow_forward
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