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5 The roof of a car in a parking lot absorbs a solar radiant flux of...
7. Consider a car in a parking lot. The wall temperature of the parking lot (Tsur) is 68 °C. The ...
7. Consider a car in a parking lot. The wall temperature of the parking lot (Tsur) is 68 °C. The car can be treated as a single surface and its heat loss through the ground is negligible. The temperature of the car (Ts) is 45 °C and the emissivity is 0.8. The convection coefficient between the car and ambient air is 10 Wm2K and the ambient air temperature is 30 °C. If the surface area of the car is 6...
The roof of a minivan can be approximated as a flat plate, 2-m wide and 3.5-...
The roof of a minivan can be approximated as a flat plate, 2-m wide and 3.5- m long. The sun beats down on the roof such that the net solar radiation absorbed is 350 W/m2. If the ambient air is 32 ºC, the car is moving at 100 km/hr, and the inside surface of the roof is heavily insulated, determine the steady-state temperature of the roof (in ºC). Ignore heat loss via radiation emitted from the roof to the surrounding.
A wall panel is insulated on the back and exposed to solar radiation on the front...
A wall panel is insulated on the back and exposed to solar radiation on the front surface. The exposed surface of the plate has an absorptivity α = 0.8 for radiation (i.e. 80% of radiant energy is absorbed). Solar radiation arrives to the panel at a rate of 1 kW⁄m2. The panel emissivity ϵ = 1 and the surrounding air temperature is 25°C. a. If we assume radiation is the only mechanism of heat transfer, in this scenario determine the...
An aluminum plate with a thickness of L=5 mm is mounted in a horizontal position, and...
An aluminum plate with a thickness of L=5 mm is mounted in a horizontal position, and its bottom surface is well insulated. A special, thin coating (with emissivity and solar absorptivity of 0.25) is applied to the top surface. The density ρ and specific heat c of aluminum are known to be 2700 kg/m3 and 900 J/kg · K, respectively. Consider conditions for which the plate is initially at a temperature of ??????=25 °C and its top surface is suddenly...
Aluminium plate painted flat black (solar absorptivity 0.98 and emissivity 0.97) Length of absorber plate is...
Aluminium plate painted flat black (solar absorptivity 0.98 and emissivity 0.97) Length of absorber plate is 1.2 m, width of absorber plate w = 0.8 m, Ambient air temperature = 25°C, effective sky temperature = 10°C, solar radiation rate = 600 w/m2. Calculate the temperature of the absorber plate?
The roof of a minivan can be approximated as a flat plate, 2-m wide and 3.5-m...
The roof of a minivan can be approximated as a flat plate, 2-m wide and 3.5-m long. The sun beats down on the roof such that the net solar radiation absorbed is 350 W/m2. If the ambient air is 32 °C. the car is moving at 100 km/hr, and the inside surface of the roof is heavily insulated, determine the steady-state temperature of the roof (in °C). Ignore radiation emitted from the roof. T32°C T 350w Assuming T, *45oC. Tlm-32+45)/2...
Problem4 A passive solar heating technique is to use a massive masonry wall to absorb solar energ...
Problem4 A passive solar heating technique is to use a massive masonry wall to absorb solar energy and then to release it slowly when the air temperature surrounding the wall is lower than that of the wall. Consider a long 3-m tall wall, well insulated on its backside, that has a net radiant solar energy flux into the wa of 150 W/m2. The air temperature is 21°C. Assuming that the temperature of the wall changes very slowly and the wall...
P2 (50 pts.) Assume the roof of a room in a typical house is 12 cm...
P2 (50 pts.) Assume the roof of a room in a typical house is 12 cm thick concrete slab with a thermal conductivity k = 1.50 W/m•°C. The roof of the room is 4 m wide and 4 m long. Assume convection heat transfer coefficients on the inner and outer surfaces of the roof are hi=6 and ho=10 W/m2°C, respectively. At noon, when the sun is "hotter" the solar irradiation is estimated to be color = 750 W/m- and the...
11 We often see frost on a windshield of car at a clear cold night. A...
11 We often see frost on a windshield of car at a clear cold night. A thin layer of water formed from moist ar dew point) on a windshield of a car in a parking lot is exposed to a clear sky at -17°C. The ambient air temperature and convection coefficient are 5°C and 10 W/m2.K. Assume that the emissivity of the thin layer of water is 0.9. Explain how frost can be formed even the ambient air temperature of...
A household oven door of 0.6-m height and 0.7-m width reaches an average surface temperature of...
A household oven door of 0.6-m height and 0.7-m width reaches an average surface temperature of 32°C during operation. The temperature of ambient air is 22°C. Assuming the door has an emissivity of 0.8 and the surroundings are also at 22°C, determine the heat transfer by free convection and the heat transfer by radiation. 1) What is the volumetric thermal expansion coefficient of air at the film temperature outside the oven door, in 1/K? 2) What is the Rayleigh number...
7. Consider a car in a parking lot. The wall temperature of the parking lot (Tsur) is 68 °C. The car can be treated as a single surface and its heat loss through the ground is negligible. The temperature of the car (Ts) is 45 °C and the emissivity is 0.8. The convection coefficient between the car and ambient air is 10 Wm2K and the ambient air temperature is 30 °C. If the surface area of the car is 6...
The roof of a minivan can be approximated as a flat plate, 2-m wide and 3.5-m long. The sun beats down on the roof such that the net solar radiation absorbed is 350 W/m2. If the ambient air is 32 °C. the car is moving at 100 km/hr, and the inside surface of the roof is heavily insulated, determine the steady-state temperature of the roof (in °C). Ignore radiation emitted from the roof. T32°C T 350w Assuming T, *45oC. Tlm-32+45)/2...
Problem4 A passive solar heating technique is to use a massive masonry wall to absorb solar energy and then to release it slowly when the air temperature surrounding the wall is lower than that of the wall. Consider a long 3-m tall wall, well insulated on its backside, that has a net radiant solar energy flux into the wa of 150 W/m2. The air temperature is 21°C. Assuming that the temperature of the wall changes very slowly and the wall...
P2 (50 pts.) Assume the roof of a room in a typical house is 12 cm thick concrete slab with a thermal conductivity k = 1.50 W/m•°C. The roof of the room is 4 m wide and 4 m long. Assume convection heat transfer coefficients on the inner and outer surfaces of the roof are hi=6 and ho=10 W/m2°C, respectively. At noon, when the sun is "hotter" the solar irradiation is estimated to be color = 750 W/m- and the...
11 We often see frost on a windshield of car at a clear cold night. A thin layer of water formed from moist ar dew point) on a windshield of a car in a parking lot is exposed to a clear sky at -17°C. The ambient air temperature and convection coefficient are 5°C and 10 W/m2.K. Assume that the emissivity of the thin layer of water is 0.9. Explain how frost can be formed even the ambient air temperature of...
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