Clothing made of several thin layers of fabric with trapped air in between, often called ski clothing, is commonly used in cold climates because it is light, fashionable, and a very effective thermal insulator. So, it is no surprise that such clothing has largely replaced thick and heavy old-fashioned coats. Consider a jacket made of five layers of 0.15-mm-thick synthetic fabric (k = 0.13 W/m-K) with 1.5-mm-thick airspace (k= 0.026 W/m.K) between the layers. Assuming the inner surface temperatuře of the jacket to be 25*C and the surface area to be 1.25 m², determine the rate of heat loss through the jacket when the temperature of the outdoors is 1°C and the heat transfer coefficient at the outer surface is 25 W/m2.K. What would your response be if the jacket is made of a single layer of 0.75-mm-thick synthetic fabric? What should be the thickness of a wool fabric (k= 0.035 W/m-K) if the person is to achieve the same level of thermal comfort wearing a thick wool coat instead of a five-layer ski jacket? The rate of heat loss through the jacket is [ w. The rate of heat transfer, if the jacket is made of a single layer, is [ The thickness of the wool fabric is mm. W

Clothing made of several thin layers of fabric with trapped air in between, often called ski clothing, is commonly used in cold climates because it is light, fashionable, and a very effective thermal insulator. So, it is no surprise that such clothing has largely replaced thick and heavy old-fashioned coats. Consider a jacket made of five layers of 0.15-mm-thick synthetic fabric (k = 0.13 W/m-K) with 1.5-mm-thick airspace (k= 0.026 W/m.K) between the layers. Assuming the inner surface temperatuře of the jacket to be 25*C and the surface area to be 1.25 m², determine the rate of heat loss through the jacket when the temperature of the outdoors is 1°C and the heat transfer coefficient at the outer surface is 25 W/m2.K. What would your response be if the jacket is made of a single layer of 0.75-mm-thick synthetic fabric? What should be the thickness of a wool fabric (k= 0.035 W/m-K) if the person is to achieve the same level of thermal comfort wearing a thick wool coat instead of a five-layer ski jacket? The rate of heat loss through the jacket is [ w. The rate of heat transfer, if the jacket is made of a single layer, is [ The thickness of the wool fabric is mm. W

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

See similar textbooks

Similar questions

Clothing made of several thin layers of fabric with trapped air in between, often called ski clothing, is commonly used in cold climates because it is light, fashionable, and a very effective thermal insulator. So it is no surprise that such clothing has largely replaced thick and heavy old-fashioned coats. Consider a jacket made of five layers of 0.1-mm-thick synthetic fabric (k = 0.13 W/m·K) with 1.5-mm-thick air space (k = 0.026 W/m·K) between the layers. Assuming the inner surface temperature of the jacket to be 28°C and the surface area to be 1.25 m2, determine the rate of heat loss through the jacket when the temperature of the outdoors is 0°C and the heat transfer coefficient at the outer surface is 25 W/m2·K. What would your response be if the jacket is made of a single layer of 0.5-mm-thick synthetic fabric? What should be the thickness of a wool fabric (k = 0.035 W/m·K) if the person is to achieve the same level of thermal comfort wearing a thick wool coat instead of a…
One end of a 0.3 m long steel rod is connected to a wall at 204°C. The other end is connected to a wall which is maintained at 93°C. Air is blown across the rod so that a heat transfer coefficient of 17 W/(m2 K) is maintained over the entire surface. If the diameter of the rod is 5 cm and the temperature of the air is 38°C, what is the net rate of heat loss to the air?
A flat isothermal computer chip has square cross-section of 1 cm x 1 cm, and is mounted on a board that insulates the chip on its sides and bottom. The top surface is exposed to a flowing coolant at 10°C, and corresponding convection coefficient h = 1000 W/m2·K. In order for the computer chip to safely operate, its temperature cannot exceed 65°C. What is the maximum allowable chip power?
A vertical furnace wall is made up of an inner wall of firebrick 20 cm thick followed by insulating brick 15 cm thick and an outer wall of steel 1 cm thick. The surface temperature of the wall adjacent to the combustion chamber is 1200°C while that of the outer surface of steel is 50°C. The thermal conductivities of the wall material in W/m-K are: firebrick, 10; insulating brick, 0.26; and steel, 45. Neglecting the film resistances and contact resistance of joints, determine the heat loss per sq. m. of wall area. Badly needed asap. I will rate helpful. Thank you in advance.
(b) A transistor with a height of 0.4 cm and a diameter of 0.6 cm is mounted on a circuit board as shown in Figure 3. The transistor is cooled by air flowing over it with an average heat transfer coefficient of 30 W/m².K. If the air temperature is 55°C and the transistor case temperature is not to exceed 70°C, determine the amount of power this transistor can dissipate safely. Disregard any heat transfer from the transistor base. Air 55°C Power transistor 0.6 cm T, ≤ 70°C -0.4 c 0.4 cm- Figure 3
A 3-layered composite wall is consists of different materials. Inside is wall 1: 300 mm thick, k = 1.5 W/m-K, then wall 2: 200 mm thick, k = 3.5 W/m-K, and wall 3: 100 mm thick. The inside surface is exposed to gases at 2192°F with surface film coefficient of 5.3 BTU/hr-ft2-R. The temperature of air in the other side of the wall is 30°C with film coefficient of 10 W/m²-K. If the minimum temperature of wall 3 is 356°F, find the overall heat transfer coefficient (W/m²-K) and the temperature drop (°C) at wall 2.
The concrete slab of a basement is 11 m long, 8 m wide, and 0.5 m thick. During the winter, temperatures are nominally 17°C and 10°C at the top and bottom surfaces, respectively. If the concrete has a thermal conductivity of 1.4 W/m-K, what is the rate of heat loss through the slab, in W? If the basement is heated by a gas furnace operating at an efficiency of 7, = 0.90 and natural gas is priced at = $0.02/MJ, what is the daily cost of the heat loss, in dollars per day? W q = Ca = i $/d
A 10-in-thick, 40-ft-long, and 20-ft-high wall is to be constructed using 9-in-long solid bricks (k = 0.50 Btu/h·ft-°F) of cross section 7 in x 7 in, or identical size bricks with nine square air holes (k = 0.02 Btu/h-ft-°F) that are 9 in long and have a cross section of 1.5 in x 1.5 in. There is a 0.5-in-thick plaster layer (k = 0.15 Btu/h-ft-°F) between two adjacent bricks on all four sides and on both sides of the wall. The house is maintained at 80°F and the ambient temperature outside is 35°F. Taking the heat transfer coefficients at the inner and outer surfaces of the wall to be 2.0 and 4.0 Btu/h-ft². °F, respectively, determine the rate of heat loss transferred through the wall constructed of (a) solid bricks and, (b) bricks with air holes. Air channels 1.5 in x 1.5 in x 9 in 0.5 in 7 in 0.5 in Plaster Brick 0.5 in-9 in→ 0.5 in
A steam pipe 50 mm diameter and 2.5 m long has been placed horizontally and exposed to still air at 25 degree Celsius. If the pipe wall temperature is 295 degree Celsius, determine the rate of heat loss. At the mean temperature difference of 160 degree Celsius, the thermo-physical properties of air are k =3.64 * 10 -2 W/m v =30.09 * 10 -6 m2/ P r =0.68 Β =1/160 + 273 = 2.31 * 10^-3/K
A transparent film will be glued onto an upper surface of a solid plate within a heated chamber. For common gluing, the temperature between the glue, a film and the solid board must be kept at 70 °C. The transparent film has a thickness of 1 mm and thermal conductivity 0.05 W/mK, while the solid board is 13 mm thick. thickness and thermal conductivity of 1.2 W / mK. Inside the climate chamber, the convection heat transfer coefficient is 70 W/m²K. The bottom surface of the solid plate is kept at 52 °C, determines the temperature inside the heated chamber and the temperature of the surface of the transparent film. Assume negligible thermal contact resistance.
The rear window of an automobile is defogged by passing warm air over its inner surface. If the warm air is at T∞,i=40°C and the corresponding convection coefficient is hi=30 W/m2·K, what are the inner and outer surface temperatures, in °C, of 4-mm-thick window glass, if the outside ambient air temperature is T∞,o= -27.5°C and the associated convection coefficient is ho=65 W/m2·K? Evaluate the properties of the glass at 300 K. a. what is Ts, i in °C? b. what is Ts, o in °C?
A 10-in-thick, 30-ft-long, and 10-ft-high wall is to be constructed using 9-in-long solid bricks (k = 0.40 Btu/ h·ft·°F) of cross section 7 in * 7 in, or identical size bricks with nine square air holes (k = 0.015 Btu/h·ft·°F) that are 9 in long and have a cross section of 1.5 in * 1.5 in. There is a 0.5-in-thick plaster layer (k = 0.10 Btu/h·ft·°F) between two adjacent bricks on all four sides and on both sides of the wall. The house is maintained at 80°F and the ambient temperature outside is 30°F. Taking the heat transfer coefficients at the inner and outer surfaces of the wall to be 1.5 and 4 Btu/h·ft2·°F, respectively, determine the rate of heat transfer through the wall constructed of (a) solid bricks and (b) bricks with air holes.