Animals in cold climates often depend on two layers of insulation: a layer of body fat...
Animals in cold climates often depend on two layers of insulation: a layer of body fat (of thermal conductivity 0.200 W/(m⋅K) ) surrounded by a layer of air trapped inside fur or down. We can model a black bear as a sphere 1.50 m in diameter having a layer of fat 4.00×10−2 m thick, as shown in the figure.(Figure 1) In studies of bear hibernation, it was found that the outer surface layer of the fur is at TC = 2.70 ∘C during hibernation, while the inner surface of the fat layer is at TH = 31.0 ∘C. How thick should the air layer (contained within the fur) be so that the bear loses heat at a rate of 50.0 W ? Thermal conductivity of air is kair = 2.40×10−2 W/(m⋅K) . Part C How many inches thick should the bear's fur layer (Lfur) be to hold a layer of air Lair so that adequate insulation is provided?
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Animals in cold climates often depend on two layers of
insulation: a layer of body fat...
Ch 17 HW Problem 17.104 Constants Animals in cold climates often depend on two layers of...
Ch 17 HW Problem 17.104 Constants Animals in cold climates often depend on two layers of insulation a layer of body fat jof thermal conductivity 0 200 W/(m K)I surrounded by a layer of air trapped inside fur or down We can model a black bear (Ursus americanus) as a sphere 1.40 m in diameter having a layer of fat 4 10 cm thick (Actually the thickness varies with the season, but we are interested in hibernation, when the fat...
FIGURE P17-56E e develop imensional be used 7Clothing made of several thin la hat kindtrapped air in between, often called ski c layers of fahr clothing, is ly used in cold climates because it is...
FIGURE P17-56E e develop imensional be used 7Clothing made of several thin la hat kindtrapped air in between, often called ski c layers of fahr clothing, is ly used in cold climates because it is light and a very effective thermal insulator. So it is n esistance monly used in cold climates because iti k asso such clothing has largely replaced thick a resist- ioned coats. hick and heavy old Consider a jacket made of five layers of o synthetic...
Al m diameter sphere is exposed to an en covered with a layer of insulation 2.5...
Al m diameter sphere is exposed to an en covered with a layer of insulation 2.5 cm thick whose thermal conductivity temperature of the sphere on the inside of the insulation is 315ºC. Assuming emissivity of 0.9, compute the value of the conve 's compute the value of the convection heat transfer coefficient that must be maintained on the outer surface of the insulation to ensure that the outer surface not exceed 41°C. exposed to an environmental temperature of 28°C....
Questions 6-9 The walls of a refrigerator are typically constructed by sandwiching a layer of insulation...
Questions 6-9 The walls of a refrigerator are typically constructed by sandwiching a layer of insulation between sheet metal panels. Consider a wall made from fiberglass insulation of thermal conductivity ki = 0.046 W/mK and thickness Li 50 mm and steel panels, each of thermal conductivity kp = 60 W/m. K and thickness Lp = 3 mm. If the wall separates refrigerated air at Too,i = 4°C from ambient air at T0o,0 = 25°C, what is the heat gain per...
During a cold winter, the surface of a river develops a layer of ice of unknown...
During a cold winter, the surface of a river develops a layer of ice of unknown thickness L. Known are the water temperature Ty=4°C, the atmospheric air temperature T=-30°C, and the temperature of the underside of the ice layer To= 0°C. The thermal conductivity of ice is k = 1.88 W/m-K. The convective heat transfer coefficients on the water and air sides of the ice layer are hw = 100 W/m²-K and ha= 50 W/m2-K, respectively. Calculate the temperature of...
For such aircraft application (Figure 3), a wall is made from insulation material (k-0.030 W/m.K) and...
For such aircraft application (Figure 3), a wall is made from insulation material (k-0.030 W/m.K) and the insulation material is mounted between four layers of carbon steel (2 mm thickness), the carbon layers are separated by a 2 mm air gap (kair-0.025 W/mK). Figure 3, the thermal conductivity of the carbon steel is (k-15.5 W/m.K). The temperature inside the wall is maintained at 6 °C. The environmental temperature is 24°C. The engineer would like to avoid condensation occurring at outer...
The core is at 37C , skin-fat layer thermal conductivity k_s = 0.3 W/m-K, skin emissivity...
The core is at 37C , skin-fat layer thermal conductivity k_s =
0.3 W/m-K, skin emissivity E_s = 0.95, skin-fat thickness l_s = 3
mm, and convection coefficient ℎ_air = 2 W/m2 -K. The jacket has
thermal conductivity of k_j = 0.5 W/m-K, jacket emissivity E_j =
0.02, and jacket thickness l_j = 2 cm.
a) Write two energy balances, one at the skin-jacket interface
and another at the jacket-air interface. Can any of the terms in
your energy balances...
IF YOU CANNOT SOLVE THEM ALL THEN PLEASE DONT SOLVE ANY. A hollow aluminum sphere, with...
IF YOU CANNOT SOLVE THEM ALL THEN PLEASE DONT SOLVE ANY.
A hollow aluminum sphere, with an electrical heater in the center, is used in tests to determine the thermal conductivity of insulating materials. The inner and outer radii of the sphere are 0.15 and 0.18 m, respectively, and testing is done under steady-state conditions with the inner surface of the aluminum maintained at 250°C. In a particular test, a spherical shell of insulation is cast on the outer surface...
1. one wall is formed by two materials, the first one is 15cm thick and has...
1. one wall is formed by two materials, the first one is 15cm thick and has a thermal conductivity of 1W/mk and the second one is cork with an unknown thick. If the temperature of the inner wall is 22°C and the temperature of the outer surface is -10°C find: a) the necessary thick of the cork to maintain a heat loss of 8W. Consider an area of 1m2! b) the interface temperature. Note: use a scheme that represents the...
Heat Loss Through Thermopane Double Window. A double window called thermopane is one in which two...
Heat Loss Through Thermopane Double Window. A double window called thermopane is one in which two layers of glass dry stagnant air. In a given window, each of the glass layers is 6.35 mm thick separated by a 6.35 mm space of stagnant air. The thermal conductivity of the glass is 0.869 W/m K and that of air is 0.026 over the temperature range used For a temperature drop of 27.8 K over the system, calculate the heat loss for...
Ch 17 HW Problem 17.104 Constants Animals in cold climates often depend on two layers of insulation a layer of body fat jof thermal conductivity 0 200 W/(m K)I surrounded by a layer of air trapped inside fur or down We can model a black bear (Ursus americanus) as a sphere 1.40 m in diameter having a layer of fat 4 10 cm thick (Actually the thickness varies with the season, but we are interested in hibernation, when the fat...
FIGURE P17-56E e develop imensional be used 7Clothing made of several thin la hat kindtrapped air in between, often called ski c layers of fahr clothing, is ly used in cold climates because it is light and a very effective thermal insulator. So it is n esistance monly used in cold climates because iti k asso such clothing has largely replaced thick a resist- ioned coats. hick and heavy old Consider a jacket made of five layers of o synthetic...
Al m diameter sphere is exposed to an en covered with a layer of insulation 2.5 cm thick whose thermal conductivity temperature of the sphere on the inside of the insulation is 315ºC. Assuming emissivity of 0.9, compute the value of the conve 's compute the value of the convection heat transfer coefficient that must be maintained on the outer surface of the insulation to ensure that the outer surface not exceed 41°C. exposed to an environmental temperature of 28°C....
Questions 6-9 The walls of a refrigerator are typically constructed by sandwiching a layer of insulation between sheet metal panels. Consider a wall made from fiberglass insulation of thermal conductivity ki = 0.046 W/mK and thickness Li 50 mm and steel panels, each of thermal conductivity kp = 60 W/m. K and thickness Lp = 3 mm. If the wall separates refrigerated air at Too,i = 4°C from ambient air at T0o,0 = 25°C, what is the heat gain per...
During a cold winter, the surface of a river develops a layer of ice of unknown thickness L. Known are the water temperature Ty=4°C, the atmospheric air temperature T=-30°C, and the temperature of the underside of the ice layer To= 0°C. The thermal conductivity of ice is k = 1.88 W/m-K. The convective heat transfer coefficients on the water and air sides of the ice layer are hw = 100 W/m²-K and ha= 50 W/m2-K, respectively. Calculate the temperature of...
For such aircraft application (Figure 3), a wall is made from insulation material (k-0.030 W/m.K) and the insulation material is mounted between four layers of carbon steel (2 mm thickness), the carbon layers are separated by a 2 mm air gap (kair-0.025 W/mK). Figure 3, the thermal conductivity of the carbon steel is (k-15.5 W/m.K). The temperature inside the wall is maintained at 6 °C. The environmental temperature is 24°C. The engineer would like to avoid condensation occurring at outer...
The core is at 37C , skin-fat layer thermal conductivity k_s =
0.3 W/m-K, skin emissivity E_s = 0.95, skin-fat thickness l_s = 3
mm, and convection coefficient ℎ_air = 2 W/m2 -K. The jacket has
thermal conductivity of k_j = 0.5 W/m-K, jacket emissivity E_j =
0.02, and jacket thickness l_j = 2 cm.
a) Write two energy balances, one at the skin-jacket interface
and another at the jacket-air interface. Can any of the terms in
your energy balances...
IF YOU CANNOT SOLVE THEM ALL THEN PLEASE DONT SOLVE ANY.
A hollow aluminum sphere, with an electrical heater in the center, is used in tests to determine the thermal conductivity of insulating materials. The inner and outer radii of the sphere are 0.15 and 0.18 m, respectively, and testing is done under steady-state conditions with the inner surface of the aluminum maintained at 250°C. In a particular test, a spherical shell of insulation is cast on the outer surface...
1. one wall is formed by two materials, the first one is 15cm thick and has a thermal conductivity of 1W/mk and the second one is cork with an unknown thick. If the temperature of the inner wall is 22°C and the temperature of the outer surface is -10°C find: a) the necessary thick of the cork to maintain a heat loss of 8W. Consider an area of 1m2! b) the interface temperature. Note: use a scheme that represents the...
Heat Loss Through Thermopane Double Window. A double window called thermopane is one in which two layers of glass dry stagnant air. In a given window, each of the glass layers is 6.35 mm thick separated by a 6.35 mm space of stagnant air. The thermal conductivity of the glass is 0.869 W/m K and that of air is 0.026 over the temperature range used For a temperature drop of 27.8 K over the system, calculate the heat loss for...
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