COLLEGE PHYSICS
2nd Edition
ISBN: 9781464196393
Author: Freedman
Publisher: MAC HIGHER
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Chapter 15, Problem 96QAP
To determine
The consumption of electrical energy of the heat pump.
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the surface area of a picnic cooler is 2.10 m^2 and it has walls constructed of a material 1.50 cm thick that has a thermal conductivity of 2.00 X 10^-2 W/(m x degrees celsius). If the temperatures inside and outside are 0.0 degress celsius and 28.5 degrees celsius, determine the rate of heat flow into the freezer and the time required to melt 2.50 kg of ice inside the cooler at 0.0 degrees celsius
A wood stove is used to heat a single room. The stove is cylindrical in shape, with a diameter of 40.0 cm and a length of 49.0 cm, and operates at a temperature of 410°F. (σ = 5.6696 10-8 W/m2 · K4, 1 Btu = 1054 J.)
(a) If the temperature of the room is 70.0°F, determine the amount of radiant energy delivered to the room by the stove each second if the emissivity is 0.950. W (b) If the room is a square with walls that are 8.00 ft high and 30.0 ft wide, determine the R-value needed in the walls and ceiling to maintain the inside temperature at 70.0°F if the outside temperature is 32.0°F. Note that we are ignoring any heat conveyed by the stove via convection and any energy lost through the walls (and windows!) via convection or radiation. ft2 · °F · h/Btu
A wood stove is used to heat a single room. The stove is cylindrical in shape, with a diameter of 40.0 cm and a length of 49.0 cm, and operates at a temperature of 420°F. (σ = 5.6696 10-8 W/m2 · K4, 1 Btu = 1054 J.)
(a) If the temperature of the room is 70.0°F, determine the amount of radiant energy delivered to the room by the stove each second if the emissivity is 0.930. ________________ W(b) If the room is a square with walls that are 8.00 ft high and 30.0 ft wide, determine the R-value needed in the walls and ceiling to maintain the inside temperature at 70.0°F if the outside temperature is 32.0°F. Note that we are ignoring any heat conveyed by the stove via convection and any energy lost through the walls (and windows!) via convection or radiation. _________________ ft2 · °F · h/Btu
Chapter 15 Solutions
COLLEGE PHYSICS
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- A building science major is investigating energy loss through windows. The windowpane of interest is 0.950 cm thick, has dimensions of 0.88 m ✕ 2.30 m, and has a thermal conductivity of 0.8 W/(m · °C). On a given cold day, the outside temperature is 0°C and the temperature of the interior surface of the glass is 28.0°C. (a)Determine the rate (in W) at which heat energy is transferred through the window. Answer- W (b)Determine the amount of energy (in J) transferred through the window in one day, assuming the temperature on the surfaces remains constant. Answer- Jarrow_forwardThe north wall of an electrically heated home is 20 ft long, 10 ft high, and 1 ft thick, and is made of brick whose thermal conductivity is k = 0.42 Btu/h·ft·°F. On a certain winter night, the temperatures of the inner and the outer surfaces of the wall are measured to be at about 62°F and 25°F, respectively, for a period of 8 h. Determine (a) the rate of heat loss through the wall that night and (b) the cost of that heat loss to the home owner if the cost of electricity is $0.07/kWh.arrow_forwardThe 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.arrow_forward
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- A concerned mother is dressing her child for play in the snow. The child's skin temperature is 34.0°C, and the outside air temperature is 2.75°C. If the emissivity of the child's skin is 0.700 and he has 1.25 ✕ 10−2 m2 of exposed skin area, what is the amount of energy transferred from his body to the surroundings in 1.00 h?arrow_forwardA rectangular window in a home has a length of 1.5 m and a height of 0.80 m. If the window allows heat to escape from the home at a rate of 2,000 watts, how thick must the window be if the inside temperature of the home is 220 C and the outside temperature is 3.00C? (Assume that the coefficient of thermal conduction of glass is 0.80 W/mK.) a. 7.1 mm b. 124 mm c. 9.1 mm d. 8.1 mm e. 11 mmarrow_forwardA room has a pine ceiling (k = 0.12 WI(m-Cº) ] that measures 3.0 m x 4.0 m 2.0 cm. On a cold day, the temperature inside the room is 20°C, and the temperature in the attic above is 8°C. If 6.0 cm of glass wool insulation ( k = 0.042 WI(m.Cº) ] were put in above the ceiling, how much energy would be saved in one hour?arrow_forward
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