Consider a house that has a
If the house is electrically heated and the price of electricity is $0.08/kVh. determine the amount of money this household will save per heating season by converting the single-pane windows to double-pane windows.
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Heat and Mass Transfer: Fundamentals and Applications
- A house has a three meter deep basement (foundation) wall that is in a 10 meter by eight meter rectangular shape based on interior dimensions. On average, 2.5 meters of the wall is below grade. Assume the outside air temperature is 38°C and the inside temperature is 20°C; there is an average ground temperature of 27°C. Determine the rate of heat loss through the wall if it is insulated with an R-value of about 30°C.m^2/W.arrow_forwardThe temperature on the two surfaces of a 25mm thick steel plate (k=48w/m°c)arrow_forwardQ2 : A 2 kW resistance heater wire with thermal conductivity of k = 20 W/m °C, a diameter of D = 5 mm, and a length of L3D0.7 m is used to boil water. If the outer surface temperature of the resistance wire is Ts = 110°C, determine the temperature at the center of the wire. Ans : 121.4 °Carrow_forward
- The wall of a house, 7 m wide and 6 m high is made from 0.3 m thick brick withk=0.6 W/m.K. The surface temperature on the inside of the wall is 16C and that onthe outside 6C. Find the heat flux through the wall and the total heat loss through it.arrow_forwardH.W. Q: An aluminum pan whose thermal conductivity is 237 W/m-°C has a flat bottom with diameter 20 cm and thickness 0.4 cm. Heat is transferred steadily to boiling water in the pan through its bottom at a rate of 800 W. If the inner surface of the bottom of the pan is at 105°C, determine the temperature of the outer surface of the bottom of the pan. 105°C 0.4 cm Answer: T= 105.43 °C 800 W 7arrow_forwardThe outer wall consists of a 30 cm thick brick wall which is covered by a layer of styrofoam. How thick is the styrofoam layer if the temperature at the boundary between the brick and styrofoam is 0 °C. External the temperature is −15°C and the indoor temperature is 23°C.arrow_forward
- Q3: Consider a 20-cm-thick large concrete plane wall (k = 0.77 W/m C) subjected to convection on both sides with TI = 27°C and hi 5 W/m2 °C on the inside, and T2 = 8°C and h2 = 12 W/m2 °C on the outside. Assuming constant thermal conductivity with no heat generation and negligible radiation, (a) express the differential equations and the boundary conditions for steady one-dimensional heat conduction through the wall, (b) obtain a relation for the variation of temperature in the wall by solving the differential equation, and (c) evaluate the temperatures at the inner and outer surfaces of the wall. Ans : (a) dT (L) = h[T(L)-T,2] (b) T(x) = 20-45.44x (c) 10.9° -k dxarrow_forwardA rectangular wall of length "L" m and height "H" m is made from a thick bricklayer. The rectangular wall has a surface area as 11 m2 & Thermal conductivity as 0.53 W/mK. The wall is subjected to heat transfer due to the outside temperature 43 °C and inside temperature 24 °C. If the energy loss is 11219 kJ in 484 minutes. (HINT: 1 minute = 60 %3D seconds) Determine the following -- i) Heat transfer rate, ii) Thickness of the wall.arrow_forwardA 2m^2 wall of 1010steel is 8 mm thick. If the outside of the wall is100 °C, andyou measure aheat flux of 80 kW/m2coming off the wall, what is the temperature of the insideof thewall?arrow_forward
- Room 4 mx 6 mx6m Fan FIGURE P1-31 A student living in a 4-m × 6-m X 6-m dormitory room turns his 150-W fan on before she leaves her room on a summer day hoping that the room will be cooler when she comes back in the evening. Assuming all the doors and win- dows are tightly closed and disregarding any heat transfer through the walls and the windows, determine the temperature in the room when she comes back 10 hours later. Use specific heat values at room temperature and assume the room to be at 100 kPa and 15°C in the morning when she leaves.arrow_forwardA thermal window consisting of two panes of 0.25" glass (R-value 0.08 hr · ft2. °F/BTU each), separated by a layer of air 0.75" thick is now used as a horizontal window in the ceiling (a skylight) of an air conditioned room. Find its R-value in the summer, when the outside is warmer than the inside, and in the winter, when the inside is warmer than the outside (in hr . ft2. °F/BTU). (Assume that the air is moving outside the window.) R (summer) hr · ft2. °F/BTU R (winter) hr : ft2 . °F/BTUarrow_forwardQ2/ A 3-m internal diameter spherical tank made of 2-cm-thick stataless steel (k= 15 W/m 0°C. The tank is located in a room whose %3D C) is used to store iced water at Te temperature is T-22°C. The walls of the room are also at 22°C. The outer surface of the tank is black and heat transfer between the outer surface of the tank and the surroundings is by natural convection and radiation. The convection heat transfer coefficients at the inner and the outer surfaces of the tank are h-80 W/m2 C and h 10 W/m2 C, respectively. Determine (a) the rate of heat transfer to the iced water in the tank and (b) the amount of ice at 0°C that melts during a 24-h period.arrow_forward
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