In another experiment, you place a layer of this cryoprotectant between one 10 cm × 10 cm cold plate maintained at −40°C and a second cold plate of the same size maintained at liquid nitrogen’s boiling temperature (77 K). Then you measure the rate of heat transfer. Another lab wants to repeat the experiment but uses cold plates that are 20 cm × 20 cm, with one at −40°C and the other at 77 K. How thick does the layer of cryoprotectant have to be so that the rate of heat transfer by conduction is the same as that when you use the smaller plates? (a) One-quarter the thickness; (b) half the thickness; (c) twice the thickness; (d) four times the thickness.
In another experiment, you place a layer of this cryoprotectant between one 10 cm × 10 cm cold plate maintained at −40°C and a second cold plate of the same size maintained at liquid nitrogen’s boiling temperature (77 K). Then you measure the rate of heat transfer. Another lab wants to repeat the experiment but uses cold plates that are 20 cm × 20 cm, with one at −40°C and the other at 77 K. How thick does the layer of cryoprotectant have to be so that the rate of heat transfer by conduction is the same as that when you use the smaller plates? (a) One-quarter the thickness; (b) half the thickness; (c) twice the thickness; (d) four times the thickness.
In another experiment, you place a layer of this cryoprotectant between one 10 cm × 10 cm cold plate maintained at −40°C and a second cold plate of the same size maintained at liquid nitrogen’s boiling temperature (77 K). Then you measure the rate of heat transfer. Another lab wants to repeat the experiment but uses cold plates that are 20 cm × 20 cm, with one at −40°C and the other at 77 K. How thick does the layer of cryoprotectant have to be so that the rate of heat transfer by conduction is the same as that when you use the smaller plates? (a) One-quarter the thickness; (b) half the thickness; (c) twice the thickness; (d) four times the thickness.
The average thermal conductivity of the walls (including windows) and roof of a house in the figure shown below is 4.8 x 104 kW/m - °C, and their average thickness is 20.8 cm. The house is heated with natural gas, with a heat of combustion (energy given off per cubic
meter of gas burned) of 9,300 kcal/m3. How many cubic meters of gas must be burned each day to maintain an inside temperature of 27.3°C if the outside temperature is 0.0°C? Disregard surface air layers, radiation, and energy loss by heat through the ground.
m3
37.0
5.00 m
8.00 m
10.0 m
The average thermal conductivity of the walls (including windows) and roof of a house in the figure shown below is 4.8 x 104 kW/m - °C, and their
average thickness is 21.4 cm. The house is heated with natural gas, with a heat of combustion (energy given off per cubic meter of gas burned) of
9,300 kcal/m3. How many cubic meters of gas must be burned each day to maintain an inside temperature of 24.0°C if the outside temperature is
0.0°C? Disregard surface air layers, radiation, and energy loss by heat through the ground.
34.68
Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all
intermediate results to at least four-digit accuracy to minimize roundoff error. m3
137.00
5.00 m
00
8.00 m
10.0 m
The average thermal conductivity of the walls (including windows) and roof of a house in the figure shown below is 4.8 10-4 kW/m · °C, and their average thickness is 20.8 cm. The house is heated with natural gas, with a heat of combustion (energy given off per cubic meter of gas burned) of 9,300 kcal/m3. How many cubic meters of gas must be burned each day to maintain an inside temperature of 25.9°C if the outside temperature is 0.0°C? Disregard surface air layers, radiation, and energy loss by heat through the ground. m3
A house has a rectangular base and a roof that peaks along a line above the center of the house and parallel to the length of the house. This roof slopes downward from the peak to each edge at an angle of 37.0° with the horizontal. The length of the front of the house is 10.0 meters. The width of the house is 8.00 meters. The height from the front of the house up to the edge of the roof is 5.00 meters.
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