Abstract
This paper deals with a numerical study of mixed convection heat transfer in horizontal eccentric annulus. The inner cylinder is supposed hot and rotating, however the outer one is kept cold and motionless. The numerical problem was solved using COMSOL Multiphysics® which is based on finite element method. The resolution of the partial differential equations was conducted through an implicit scheme with the use of the damped Newton’s method. The present numerical analysis concerns the effect of eccentricity, rotation speed and Rayleigh number on the flow patterns, heat transfer rate, and energy efficiency of the process. It was found that the heat transfer rate increases with the increase of Rayleigh number. In addition, the heat transfer rate drops with the increase of rotation speed. Finally, we have demonstrated that maximum energy efficiency is achieved not only with higher Rayleigh number but also it is maximum with small eccentricity.
Highlights
The flow pattern in the form of streamlines and isotherms was explored for different Rayleigh numbers, rotational speeds and eccentricity positions
It was found that the heat transfer rate improves with the increase of both Rayleigh number Ra and eccentricity e
We have demonstrated that when the inner cylinder is motionless (W = 0), the heat transfer is mainly conducted by natural convection
Summary
The analysis of heat transfer in cylindrical annulus has been the subject of several old research works.[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15] Many configurations were considered in both experimental and numerical studies: concentric motionless annulus,[1,2,3,4] concentric annulus with rotating inner cylinder,[5,6,7,8,9,10,11] eccentric motionless annulus,[12,13,14] and eccentric annulus with rotating inner cylinder.[15,16]The problem of mixed convection heat transfer in cylindrical annulus is still attracting the attention of recent researchers thanks to its importance in many engineering applications such as heat exchangers, centrifugal pumps, wastewater purification systems, etc. The analysis of heat transfer in cylindrical annulus has been the subject of several old research works.[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15] Many configurations were considered in both experimental and numerical studies: concentric motionless annulus,[1,2,3,4] concentric annulus with rotating inner cylinder,[5,6,7,8,9,10,11] eccentric motionless annulus,[12,13,14] and eccentric annulus with rotating inner cylinder.[15,16]. Lee[16] studied numerically the case of heat transfer in eccentric annulus.
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