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A 10-cm-thick vall is to be constructed with 2.5-rn-long wood studs
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Heat and Mass Transfer: Fundamentals and Applications
- A cylindrical cold storage facility with an inner diameter of 4m and height of 2m is constructed. For the wall, the first layer is 6 cm of glass wool (0.1 W/m-C), followed by 30 cm of concrete. The temperature inside is maintained at -10C (hin = 55 W/m^2-C) while the outside temperature is 10°C (hout = 22 w/m^2-C). If the steady rate of heat transfer is at 60W, (a) what is the thermal conductivity of concrete? (b) At what radius is the temperature at 0°C? To prevent water condensation inside the concrete wall (which damages the structure), A 5 cm layer of insulation (k = 0.15 W/m-C) is added to the exterior of the facility. (c) What is the new rate of heat transfer? (d) What is the temperature at the interface of the concrete wall and new insulation? (e) is condensation within the core of the wall prevented?arrow_forwardA 4-m-high and 6-m-wide wall consists of a long 18-cm x 30-cm cross section of horizontal bricks (k = 0.72 W/mK) separated by 3-cm-thick plaster layers (k=0.22 W/mK). There are also 2-cm-thick plaster layers on each side of the wall, and a 2-cm-thick rigid foam (k=0.026 W/mK) on the inner side of the wall. The indoor and outdoor temperatures are 22°C and -4°C, and the convection heat transfer coefficients on the inner and the outer sides are h1= 10 W/m2K and h2= 20 W/m2K, respectively.Assuming one-dimensional heat transfer and disregarding radiation, determine the rate of heat transfer through the wall.arrow_forwardA cylindrical cold storage facility with an inner diameter of 4m and height of 2m is constructed. For the wall, the first layer is 6 cm of glass wool (0.1 W/m-C), followed by 30 cm of concrete. The temperature inside is maintained at -10C (hin = 55 W/m^2-C) while the outside temperature is 10°C (hout = 22 w/m^2-C). If the steady rate of heat transfer is at 60W, (a) what is the thermal conductivity of concrete? (b) At what radius is the temperature at 0°C? To prevent water condensation inside the concrete wall (which damages the structure), A 5 cm layer of insulation (k = 0.15 W/m-C) is added to the exterior of the facility. (c) What is the new rate of heat transfer?arrow_forward
- A road consisting of two cylindrical portions AB and BC is restrained at both ends. Portion AB is made of steel ( Es=200 GPa, as= 11.7x10-6/ oC) and portion BC is made of brass (Eb= 105 GPa, ab=20.9x10-6/ oC). If the rod is free at A, determine the total thermal expansion in millimeter (4 decimal) when there is a temperature rise of deltaT = 37oC.arrow_forwardLine AB was measured to be 2465.75 m when using a 100 m steel tape supported only at the ends under a pull of 9 kg and a mean temperature of 40°C. The tape is of standard length at 35 °C at a pullof 10 kg. The cross sectional area of the tape is 0.035 cm.?. Determine the correct length AB.arrow_forwardA small storage room has the dimensions of 20 m X 20m X 3m high. The walls of the storage consist of three layers; Drywall (thickness = 0.5 inch, K = 0.5 W/mK), Fiberglass (thickness = 2 cm, K = 0.1 W/mK), and Brick (thickness = 8 cm, K = 0.5 W/mK). On one of the walls, there is one small wooden door with the dimensions of 0.9 m X 2 m and thickness of 3 cm. The thermal conductivity of wood is 0.4 W/mK. The inside temperature of the storage room is to be maintained at 20°C, while the temperature outside is 0°C. The rate of heat lost through the roof is 30 kW. Heat loss through the floor can be ignored. a) Calculate the total heat loss from the storage room (kW). b) Determine the temperature at the inner wall of the brick (°C). c) If cost of heating is $0.166/kWh, calculate the heating cost per month. Note that 1 kWh = 3600 kJ.arrow_forward
- The wall of a 5 m high cylinderical steel tank (ks= 20 W/mK) of inner diameter 1.5 m and 200 mm thick contains hot oil at 100 C. On the outside of the tank 12 mm of spray urethane insulation is added to stop the oil from cooling. If the worst outside temperature is -6 , (hi = 16 W/m^2 K) and (ho = 5 W/m^2 K) how much heat needs to be added to keep the tank at 100 C for pumping reasons and what are the overall heat transfer coefficients Uo and Ui?arrow_forwardH.W: 10-02-2021: The exterior wall of a building consists of 100 mm thick face brick (k = 0.9 Wm¯'K'), 40 mm thick polystyrene insulating board (k 0.036 Wm'K¯), 125 mm thick concrete block (k = 1.8 Wm¯'K') and 15 mm thick interior gypsum board (k = 0.18 Wm K). The inside and outside convective heat transfer coefficients are 6.5 Wm K and 22.5 Wm 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 (i) the rate of heat loss through the wall,arrow_forwardA 4-m-high and 6-m-wide wall consists of a long 18-cm x 30-cm cross section of horizontal bricks (k = 0.72 W/m-K) separated by 3-cm-thick plaster layers (k = 0.22 W/m-K). There are also 2-cm-thick plaster layers on each side of the wall, and a 2-cm thick rigid foam (k = 0.026 W/m-K) on the inner side of the wall. The indoor and the outdoor temperatures are 38°C and -4°C, respectively, and the convection heat transfer coefficients on the inner and the outer sides are hy = 10 W/m2-K and h2 = 20 W/m2K, respectively. Assuming one-dimensional heat %3D transfer and disregarding radiation, determine the rate of heat transfer through the wall (in W). Foam Plaster Brickarrow_forward
- A steel rod is heated from 25 to 250. Its coefficient of thermal expansion is 10-5/°C and E = 100 GN/m2. If the rod is free to expand, the thermal stress developed in it is..arrow_forwardA thin brass pipe, 3 cm in outside diameter, carries hot water at 85°C. It is proposed to place 0.8 mm thick straight circular fins on the pipe to cool it. The fins are 8 cm in diameter and are spaced 2 cm apart. It is determined that h will equal 20 W/m².°C on the pipe and 15 W/m².°C on the fins, when they have been added. If T = 22°C, compute the heat loss per meter of pipe before and after the fins are added.arrow_forwardDetermine the resistance of an aluminium coil of 129 cm as diameter consists of 15400 turns and the mean length per turn is 4130 cm. Take the electrical conductivity of the aluminium coil as 0.31 MS/m. Solution: Area of Cross-section of the Coil (in m?) Total Length (in m) The Resistance of the Coil (in 2)arrow_forward
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