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 m 2 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 conducted through the jacket and away from your body?
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 m 2 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 conducted through the jacket and away from your body?
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 conducted through the jacket and away from your body?
A cubical piece of heat-shield-tile from the space shuttle measures 0.13 m on a side and has a thermal conductivity of 0.065 J/(s·m·C°). The outer surface of the tile is heated to a temperature of 1070°C, while the inner surface is maintained at a temperature of 24°C. (a) How much heat flows from the outer to the inner surface of the tile in 4.0 minutes? (b) If this amount of heat were transferred to 2.6 liters (2.6 kg) of liquid water, by how many Celsius degrees would the temperature of the water rise?
A human body has a temperature of 30°C If its total surface area is 1.2 m2, what is the net rate of heat loss from the body by convection alone considering the surrounding temperature to be 24°C? Consider film coefficient to be h = 4.7 W/m2K.
The roof of a house consists of a 15-cm-thick concrete slab (k = 2 W/m·K) that is 15 m wide and 20 m long. The convection heat transfer coefficients on the inner and outer surfaces of the roof are 5 and 12 W/m2·K, respectively. On a clear winter night, the ambient air is reported to be at 10°C, while the night sky temperature is 100 K. The house and the interior surfaces of the wall are maintained at a constant temperature of 20°C. The emissivity of both surfaces of the concrete roof is 0.9. Considering both radiation and convection heat transfers, determine the rate of heat transfer through the roof, and the inner surface temperature of the roof. If the house is heated by a furnace burning natural gas with an efficiency of 80 percent, and the price of natural gas is $1.20/ therm (1 therm = 105,500 kJ of energy content), determine the money lost through the roof that night during a 14-h period.
Chapter 12 Solutions
Student Workbook for College Physics: A Strategic Approach
Physics for Scientists and Engineers: A Strategic Approach, Vol. 1 (Chs 1-21) (4th Edition)
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