Engineering, 04.10.2019 21:20, Arealbot
The roof of a house consists of a 15-cm-thick concrete slab (k 5 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 cen98187_ch03_p142-236.indd 212 14/02/14 4: 34 pm chapter 3 213 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 5 105,500 kj of energy content), determine the money lost through the roof that night during a 14-h period
Answers: 3
Engineering, 04.07.2019 18:10, johnthienann58
Thermal stresses are developed in a metal when its a) initial temperature is changed b) final temperature is changed c) density is changed d) thermal deformation is prevented e) expansion is prevented f) contraction is prevented
Answers: 2
Engineering, 04.07.2019 18:20, maustin5323
Athin walled concentric tube exchanger is used to cool engine oil from 160°c to 60°c with water that is available at 25°c acting as a coolant. the oil and water flow rates are each at 2 kg/s, and the diameter of the inner tube is 0.5 m and the corresponding value of the overall heat transfer coefficient is 250 w/m2. oc. how long must the heat exchanger be to accomplish the desired cooling? cpwater=4.187 kj/kg-candcpengine el=2.035 kj/kg·°c, oil . 120]
Answers: 1
Engineering, 04.07.2019 18:20, rhussein6452
Wiy doeres rere okhn a pump whon working betwon the same pressure range?
Answers: 2
The roof of a house consists of a 15-cm-thick concrete slab (k 5 2 w/m·k) that is 15 m wide and 20 m...
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