Heat transfer in eccentric annuli

(1995) Heat transfer in eccentric annuli. PhD thesis, King Fahd University of Petroleum and Minerals.


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Various modes of heat transfer through eccentric annuli have been studied either analytically or numerically. These include transient conduction with uniform internal heat generation in eccentrically hollow cylinders, the fully developed free convection in open-ended vertical annuli, the developing forced convection in eccentric annuli and the developing free convection in open-ended vertical eccentric annuli. Four pairs of thermal boundary conditions have been investigated in which one of the boundaries is heated isothermal at the ambient temperature. The case under study us called case I when the heated wall is the inner wall while it is called case O when the heated wall is the outer wall. The transient conduction has been solved numerically using a finite difference technique. The obtained steady-state numerical solutions have been compared with their corresponding available (if any)/derived analytical solutions. This comparison provided means of validation of the present finite-diffrence scheme and its method of solution. The obtained numerical temperature profiles were used to obtain useful engineering parameters such as the maximum temperature within the annulus material and the time needed to reach steady-state conditions. The eccentricity and the boundary conditions were found to affect the heat transfer parameters greatly. The internal heat generation was found to affect the steady-state time slightly. Fully developed free convection in vertical open-ended eccentric annuli has been solved numerically for boundary conditions of the first and fourth kind while an anlytical solution was provided for boundary conditions of the third kind. Results for the heat transfer parameters such as the temperature distribution, mean bulk temperature, average velocity, induced volumetric flow rate, heat absorbed, the local Nusselt number and the circumferentially-averaged Nusselt number have been presented in a series of figures covering a wide range of eccentricities. It was found that the heat transfer rate and the induced volumetric flow rate increase with eccentricity. A mathematical model based on the boundary layer theory has been developed to describe the flow and heat transfer in the entry region of eccentric annuli. This model has been derived and formulated in a general manner to describe both free and forced convection. A finite-difference algorithm has been developed to numerically solve the relevant equations. The developing laminar forced convection in eccentric annuli has been solved using this alogrithml and the results show good agreement with the work reported previously. Then the free convection problem has been solved for the four pairs of thermal boundary conditions.

Item Type: Thesis (PhD)
Subjects: Mechanical
Department: College of Engineering and Physics > Mechanical Engineering
Committee Advisor: El-Shaarawi, M. A. I.
Committee Members: Zaman, Fiazuddin and Yilbas, Bekir S. and Abualhamayel, Habib I.
Depositing User: Mr. Admin Admin
Date Deposited: 22 Jun 2008 13:58
Last Modified: 01 Nov 2019 13:58
URI: https://eprints.kfupm.edu.sa/id/eprint/10181