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A one-dimensional plane wall of thickness
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Fundamentals of Heat and Mass Transfer
- A plane wall, 7.5 cm thick, generates heat internally at the rate of 105 W/m3. One side of the wall is insulated, and the other side is exposed to an environment at 90C. The convection heat transfer coefficient between the wall and the environment is 500 W/m2 K. If the thermal conductivity of the wall is 12 W/m K, calculate the maximum temperature in the wall.arrow_forwardA plane wall 15 cm thick has a thermal conductivity given by the relation k=2.0+0.0005T[W/mK] where T is in kelvin. If one surface of this wall is maintained at 150C and the other at 50C, determine the rate of heat transfer per square meter. Sketch the temperature distribution through the wall.arrow_forwardExample 2: Double-pane window, each window have: Height = 0.8 m Width 1.5 m Thickness = 4 mm k (glass) = 0.78 W/m.K separation between two glasses (air) = 10 mm k (air) = 0.026 W/m.K Temperature of inner surface = 20°C Temperature of outer surface = -10°C Convection heat transfer coefficient on the inner surface h1= 10 W/m2·°C Convection heat transfer coefficient on the outer surface h2= 40 W/m2·°C Determine the heat transfer through the window?arrow_forward
- A very long copper rod 20 mm in diameter extends horizontally from a plane-heated wall maintained at 100 degree Celsius. The surface of the rod is exposed to an air environment at 20 degree Celsius with convective heat transfer coefficient of 8.5 W/m2 degree. Workout the heat loss if the thermal conductivity of copper is 400 W/m degreea) 10.71 Wb) 20.71 Wc) 30.71 Wd) 40.71 Warrow_forwardExample 1: Single-pane window, the window have: Height = 0.8 m Width 1.5 m Thickness = 4 mm k (glass) = 0.78 W/m.K Temperature of air at inner surface = 20°C Temperature of air at outer surface = -10°C Convection heat transfer coefficient on the inner surface h1= 10 W/m2·°C Convection heat transfer coefficient on the outer surface h2= 40 W/m2·°C Determine the heat transfer through the window?arrow_forwardA steam pipe 50 mm diameter and 2.5 m long has been placed horizontally and exposed to still air at 25 degree Celsius. If the pipe wall temperature is 295 degree Celsius, determine the rate of heat loss. At the mean temperature difference of 160 degree Celsius, the thermo-physical properties of air are k =3.64 * 10 -2 W/m v =30.09 * 10 -6 m2/ P r =0.68 Β =1/160 + 273 = 2.31 * 10^-3/Karrow_forward
- A domestic refrigerator with inner dimensions of 0.7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 ˚C. The bodies consist of two 10-mm-thick layers of Aluminium (k = 225 W/mK) separated by a 30 mm polyurethane insulation (k=0.028 W/mK). If the average convection heat transfer coefficient at the inner and outer surfaces are 11.6 W/m2K and 14.5 W/m2K respectively, calculate: Data: Hgt = , W = , L1 = L3 = = m, k1= k3 = , L2 = = , k2 = , T∞1 = , T∞2 = , ho= , hi = .arrow_forwardThe thermal conductivities of human tissues vary greatly. “Fat” and “skin” have conductivities of approximately 0.200 W /m 0K and 0.0200 W /m 0K, respectively, while other “tissues” inside the body have conductivities of approximately 0.500 W /m 0 Assume that between the core region of the body and the skin surface lies a “skin” layer of 1.00mm, a “fat” layer of 0.500 cm., and 3.20 cm. layer of other “tissues”. Find the rate of energy loss when the core temperature is 37.00C and the exterior temperature is 0.000 Assume a body area of 2.00 m2. (Both a protective layer of clothing and an insulating layer of unmoving air are absent).arrow_forwardA steel pipe (outside diameter 100 mm) is covered with two layers of insulation. The inside layer, 40 mm thick, has a thermal conductivity of 0.07 W/(m K). The outside layer, 20 mm thick, has a thermal conductivity of 0.15 W/(m K). The pipe is used to convey steam at a pressure of 600 kPa. The outside temperature of insulation is 24°C. If the pipe is 10 m long, determine the following, assuming the resistance to conductive heat transfer in steel pipe and convective resistance on the steam side are negligible: a. The heat loss per hour. b. The interface temperature of insulation.arrow_forward
- Question 1: The exterior wall of a building consists of 100 mm thick face brick (k = 0.9 W/m∙K), 40 mm thick polystyrene insulating board (k = 0.036 W/m∙K), 125 mm thick concrete block (k = 1.8 W/m∙K) and 15 mm thick interior gypsum board (k = 0.18 W/m∙K). The inside and outside convective heat transfer coefficients are 6.5 W/m2∙K and 22.5 W/m2∙K, respectively. The outside air temperature is -5°C and the inside air temperature is 20°C. The wall is 3 m high and 15 m long. Calculate the rate of heat loss (in W) through the wall. Follow-up question to Question 1, calculate the temperature (in °C) of the interior surface of the wall. Follow-up question to Question 1, calculate the temperature (in °C) of the exterior surface of the wall. Note: Round the answers to 2 decimal places.arrow_forwardA steel tube with a thermal conductivity of 55 W/m.K carries a fluid at 175°C, with a convection heat transfer coefficient of 190 W/m²./K. The tube has an external diameter of 5 cm, a wall thickness of 1 cm and a length of 1.5 m. The ambient air and surroundings are at 27°C, with a convection heat transfer coefficient of 20 W/m².K. Neglecting the effects of radiation, determine: (ANSWER LETTERS E, F and G) a) the resistance by conduction through the tube wall b) the convection resistance inside the tube c) The total rate of heat transferd) The temperature of the outer surface of the tube e) The total resistance considering the effects of radiation only on the outside, with the coefficient hr = 2W/m².Kf) The new heat transfer rate, considering the effects of radiation, if an additional layer of 15 mm thick foam with a conductivity of 0.03 W/m.K is added to the system.g) The critical insulation radius of the system after the addition of this insulating layer.arrow_forwardA heat pack can be modeled as a plane wall of thickness L=2cm. Assume that the pack has a constant thermal conductivity (4.0 W/(m*K)) and constant heat generation (800 W/m3 ) with one side (x=0) maintained at a constant temperature T1 = 80°C and the other side (x=L) cooled by moving air at T∞ = 25°C with a heat transfer coefficient of h = 20 W/(m2K).a. Reduce the heat equation with clearly stated assumptionsb. Find the steady-state temperature distribution T(x) in the pack.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning