A spherical vessel has an inner radius r1 and an outer radius r2. The inner surface
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HEAT+MASS TRANSFER:FUND.+APPL.
- 1.60 Two electric resistance heaters with a 20 cm length and a 2 cm diameter are inserted into a well-insulated 40-L tank of water that is initially at 300 K. If each heater dissipates 500 W, what is the time required for bringing the water temperature in the tank to 340 K? State your assumption for your analysis.arrow_forward2.34 Show that the temperature distribution in a sphere of radius . made of a homogeneous material in which energy is released at a uniform rate per unit volume , isarrow_forward3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on one side is and on the other side is . If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it takes for the copper plate to reach a temperature of 82°C.arrow_forward
- A cooling system is to be designed for a food storage warehouse for keeping perishable foods cool prior to transportation to grocery stores. The warehouse has an effective surface area of 1860 m2 exposed to an ambient air temperature of 32C. The warehouse wall insulation (k=0.17W/(mK)) is 7.5 cm thick. Determine the rate at which heat must be removed (W) from the warehouse to maintain the food at 4C.arrow_forwardHeat is transferred at a rate of 0.1 kW through glass wool insulation (density=100kg/m3) with a 5-cm thickness and 2-m2 area. If the hot surface is at 70C, determine the temperature of the cooler surface.arrow_forwardan unsisulated 100 mm diameter steam pipe runs for 25 meters inside a room whose walls and air are at a temperature of 25 C. the superheated steam inside the pipe maintains the temperature at the pipe surface at 150 C. if the natural convection heat transfer coefficient of the air outside the pipe is 10 w/m^2 k and the surface emissivity is 0.8, compute for the total rate of heat transfer from the surface of the pipe in k/Warrow_forward
- The heat generated in the circuitry on the surface of a silicon chip (k =130 W/m.C) is conducted to the ceramic substrate to which it is attached. The chip is 6 mm X 6 mm in size and 0.5 mm thick and dissipates 3 W of power for 24 hours. Disregarding any heat transfer through the 0.5 mm high side surfaces, determine the amount of heat dissipates during the 24-hour period. Silicon chip 0.5 mm 3 W CeramicC substrate Select one a. None of the above b. 0.072KWh c. 0.72KWh d. 0.027KWharrow_forwardIn an orbiting space station, an electronic package is housed in a compartment having a surface area 1 m² which is exposed to space. The surface emissivity is 1.0. Under normal operating conditions, the electronics generate 500 W of heat which must be dissipated from the exposed surface to space. If the surface is exposed to a solar flux of 750 W/m² and its absorptivity to solar radiation is 0.25, please find the steady-state temperature of the surface.arrow_forwardThe rate of heat flow through a hallow sphere of inner radius 0.25 m and outer radius 0.35m, whose thermal conductivity is 5 W/mK, maintained at temperatures of 400°C and 300°C respectively equal toarrow_forward
- Consider the rate of heat conduction through a double-paned window that has a 1.6-m2 area and is made of two panes of 0.76-cm-thick glass separated by a 0.75-cm air gap. You can ignore the increased heat transfer in the air gap due to convection. a. Calculate the rate of heat conduction through this window, in watts, given that the inside surface temperature is 15.0°C, while the outside temperature is -10.0°C. Make the assumption that the temperature differences across the two glass planes are equal. First find these and then the temperature drop across the air gap. b. For comparison, calculate the rate of heat conduction, in watts, through a single 1.67-cm-thick window of the same area and with the same temperatures as in part (a).arrow_forwardEnergy transfer by conduction is primarily restricted to liquids fluids gases solids Which is correct?arrow_forwardA large steel plate having a thickness of L = 4 in, thermal conductivity of k= 7.2 Btu/h·ft. °F, and an emissivity of ε = 0.7 is lying on the ground. The exposed surface of the plate at x = L is known to exchange heat by convection with the ambient air at T∞ = 90°F with an average heat transfer coefficient of h = 12 Btu/h·ft².°F as well as by radiation with the open sky with an equivalent sky temperature of Tsky =480 R. Also, the temperature of the upper surface of the plate is measured to be 80°F. Assuming steady one-dimensional heat transfer, (a) express the differential equation and the boundary conditions for heat conduction through the plate, (b) obtain a relation for the variation of temperature in the plate by solving the differential equation, and (c) determine the value of the lower surface temperature of the plate at x = 0. Tsky h, To Convection Radiation XA 80°F L E Plate 0 Groundarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning