cylindrical shape body of length is 1.9 m and diameter is 400 mm is inside a room where the ambient temperature is equal to 300 K. The initial temperature of the body is equal to 350 K. If the heat convective coefficient is equal to 1.3 W/m^2.K. What is the thermal co

cylindrical shape body of length is 1.9 m and diameter is 400 mm is inside a room where the ambient temperature is equal to 300 K. The initial temperature of the body is equal to 350 K. If the heat convective coefficient is equal to 1.3 W/m^2.K. What is the thermal co

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter7: Forced Convection Inside Tubes And Ducts

Section: Chapter Questions

Problem 7.48P

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A square silicon chip 7mm7mm in size and 0.5-mm thick is mounted on a plastic substrate as shown in the sketch below. The top surface of the chip is cooled by a synthetic liquid flowing over it. Electronic circuits on the bottom of the chip generate heat at a rate of 5 W that must be transferred through the chip. Estimate the steady-state temperature difference between the front and back surfaces of the chip. The thermal conductivity of silicon is 150 W/m K. Problem 1.6
1.4 To measure thermal conductivity, two similar 1-cm-thick specimens are placed in the apparatus shown in the accompanying sketch. Electric current is supplied to the guard heater, and a wattmeter shows that the power dissipation is 10 W. Thermocouples attached to the warmer and to the cooler surfaces show temperatures of 322 and 300 K, respectively. Calculate the thermal conductivity of the material at the mean temperature in W/m K. Problem 1.4
1.63 Liquid oxygen (LOX) for the space shuttle is stored at 90 K prior to launch in a spherical container 4 m in diameter. To reduce the loss of oxygen, the sphere is insulated with superinsulation developed at the U.S. National Institute of Standards and Technology's Cryogenic Division; the superinsulation has an effective thermal conductivity of 0.00012 W/m K. If the outside temperature is on the average and the LOX has a heat of vaporization of 213 J/g, calculate the thickness of insulation required to keep the LOX evaporation rate below 200 g/h.
1.3 A furnace wall is to be constructed of brick having standard dimensions of Two kinds of material are available. One has a maximum usable temperature of 1040°C and a thermal conductivity of 1.7 W/(m K), and the other has a maximum temperature limit of 870°C and a thermal conductivity of 0.85 W/(m K). The bricks have the same cost and are laid in any manner, but we wish to design the most economical wall for a furnace with a temperature of 1040°C on the hot side and 200°C on the cold side. If the maximum amount of heat transfer permissible is 950 , determine the most economical arrangement using the available bricks.
A large 100-mm thick steel plate is initially at uniform temperature T = 180°C at time t = 0. Both sides of the plate are exposed to 30°C oil with convection coefficient h = 1500 W/m².K. The thermal conductivity, heat capacity, and density of the steel are k = 38 W/m-K, cp = 485 J/kg-K, and p = 7800 kg/m³. a) Find the temperature at the center of the slab when t = 125 s. b) Find the temperature at the surface of the slab when t=125 s.
A certain material has a thickness of 30 cm and a thermal conductivity of 0.04 W/m- °C. At a particular instant in time, the temperature distribution with x, the distance from the left face, is T = 150x ^ 2 - 30x , where x is in meters. Calculate the heat-flow rates atx x = 0 and x = 30 cm . Is the solid heating up or cooling down?
1. A beverage cooler is in the shape of a cube, 42 cm on each inside edge. Its 3.0-cm thick wall are made up of plastic (kr = 0.050 W/mK). When the outside temperature is 20°C, how much ice will melt each hour? Tice is 0°C. 2. One of the possible mechanisms of heat transfer in human body is conduction through body fat. Suppose that heat travels through 0.03 m of fat in reaching the skin, which has a total surface area of 1.7 m² and a temperature of 34°C. Find the amount of heat that reaches the skin in half an hour, if the temperature at the body, interior is maintained at the normal value 37°C ? Thermal conductivity of body fat is k = 0.2 J/sm°C. 3. The air in a room is at 25°C and outside temperature is 0°C. The window of the room has an area of 2m² and thickness 2mm. Calculate the rate of loss of heat by conduction through window ? Thermal conductivity for glass is 1 Wm¯'degree!.
Consider a singlecylindrical fin of a uniform cross-sectional area (D = 5 mm, L = 70 mm, k = 400 W/m.K) that is attached to a wall with a base temperature of Tb= 180 C. Ambient conditions are T∞= 50 °C and h = 210 W/m2.K. a.What is the heat transfer rate of a single fin? b.Plot the temperature distribution within the fin (Excel, MATLAB, ... etc.) c.What is the material of the fin?
Two walls of cold storage plant are composed of an insulating material (k = 0.25 kJ/hr-m-°C), 100mm thick at the outer layer and material (k = 3.5 kJ/hr-m-°C), 15mm thick at inner layer. If the surface temperature at the cold side is 30 °C and hot side is 250 °C, find the heat transmitted per square meter.
1.19 A square isothermal chip is of width w = front surface is exposed to the flow of a coolant at T = 15°C. From reliability considerations, the chip temperature must not exceed T = 85°C. 5 mm on a side and is mounted in a substrate such that its side and back surfaces are well insulated; the Coolant Chip If the coolant is air and the corresponding convection coefficient is h = 200 W/m² · K, what is the maximum allowable chip power? If the coolant is a dielectric liquid for which h = 3000 W/m² · K, what is the maximum allowable power?
4. Two aluminum blocks with different dimensions, but the same mass are shown in the figure. The dimensions of block 1 are 0.25 cm in thickness, 3 cm in width, and 36 cm in length. The dimensions of block 2 are 3 cm for each side of the cube. Aluminum has a density of 2700 kg/m³ and a specific heat capacity of 900 J/kg-°C. The value of the heat transfer coefficient to the surrounding air is 10 W/m²-°C. 0.25 cm 36 cm 3 cm 3 cm Block 1 3 cm Block 2 3 cm Complete the following. (a) Calculate thermal time constant (in min) for both blocks. (b) Each block is heated to an initial temperature 120 °C and then allowed to cool in the surrounding air which is at 20 °C. Write a script file in MATLAB® that plots the temperature as a function of time, T(t), for both blocks on the same graph. Plot the temperature of block 1 using a solid black line and the temperature of block 2 using a dotted black line. Plot for a duration equal to four of the longer time constant between blocks 1 and 2. The time…
S is 6. A spherical shaped vessel of 1.4 m outer diameter is 90 mm thick. Find the rate of heat leakage, if the temperature difference between the inner and outer surfaces is 220°C. Thermal conductivity of the material of the sphere is 0.083 W/mK. (a) 0.2 kW (c) 1.088 kW (b) 0.5 kW (d) 1.6 kW