Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470917855
Author: Bergman, Theodore L./
Publisher: John Wiley & Sons Inc
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Chapter 4, Problem 4.16P
A tube of diameter 50 mm having a surface temperature of 85°C is embedded in the center plane of a concrete slab 0.1 m thick with upper and lower surfaces at 20°C. Using the appropriate tabulated relation for this configuration, find the shape factor. Determine the heat transfer rate per unit length of the tube.
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Air at 4 °C is being carried within a metal cylindrical pipe to astorage room at a bioprocessing facility, where a heat-sensitive protein product must be stored until it is transferred to another facility. The outer diameter of the pipe is 400 mm, and the thickness of the pipe is 2 mm. The pipe is installed within a larger room where the room temperature is kept at 20°C. There is a layer of insulating material around the metal pipe. Thermal conductivity of the metal pipe is 60 W/m*K, whereas the thermal conductivity of the insulating material is 0.04 W/m*K. Heat gain by the air being transported occurs at a steady rate of 40 W. A while later, it becomes necessary to reduce the temperature of the flowing air down to 0 °C for another protein product. By how much (in percentages) should the insulation material thickness should increase in order to maintain this air temperature within the pipe? Assume the inner surface temperature of the metal pipe is equal to the air temperature in the…
Thermal treatment of a steel cube, of 10 cm side length, L, requires a two
step cooling process. In the first step, the cube at the uniform temperature of 500°C is
placed in air where it is cooled to 250°C. In the second step, it is moved to large oil
bath of temperature 20°C where the heat transfer coefficient at all surfaces
is the same and equal to h = 50 W m-2 K-1.
%3D
Calculate the total amount of energy lost by the cube and show that the lumped
capacitance method can be used to calculate the temperature during the second step of
cooling. Calculate the time necessary to reduce the cube temperature to 50°C.
Thermal properties
Density = 8000 kg m-3
Cp= 480 J kg-1 K-1
k = 30 W m-1 K-1.
%3D
Chapter 4 Solutions
Fundamentals of Heat and Mass Transfer
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