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Numerical Study on Muti-fields Coupling for Different Types of Heat Exchanger Tubes with Inside and Outside Fluid

Author: HuoXiJun
Tutor: LiuJuBao
School: Northeast University of Petroleum
Course: Solid Mechanics
Keywords: heat exchanger FEM coupled heat transfer surface coefficient of heat transfer thermal-stress analysis
CLC: TQ051.5
Type: Master's thesis
Year: 2011
Downloads: 177
Quote: 0
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Abstract

Heat exchanger is the most commonly used device in petrochemical industry. Making heat transfer efficiency and performance better is an important way to saving investment and energy and improving the productivity. So putting forward an analysis method of Multi-field heat exchanger with inside and outside fluid can provide the basis for the design of efficient and secure heat exchanger. This paper makes different tubes and fluid inside and outside the tubes as the research object. It also dose numerical calculation by using software of Hydromechanics and Solid Mechanics. Firstly, using ANSYS sequential coupling and direct coupling researches on stress and temperature field of a quarter of heat exchanger model. And we find that the direct coupling method is more accurate. Secondly, through numerical analysis of coupling inside and outside fluid of the heat exchanger by using CFX software, we can get that the the fluid temperature is lowest in center and highest on the tube wall. The fluid temperature ouside the tube is highest inside the tube wall in the exit and the temperature is lower layer by layer along the radial. Fluid temperature inside and outside the tube wall increases in gradient shape along the axial direction, and at the same axial position, the temperature inside is higher than the temperature outside. Through the numerical analysis we can also get that there si a fluid pressure deficit inside the tube in local areas, the fluid velocity inside the tube becomes smaller near the tube wall. With the increase of the flow inside and outside the tube, that the Inlet and outlet temperature difference, pressure difference of the fluid inside and outside the tube and the wall temperature, the heat flow rate, the surface coefficient of heat transfer inside and outside the tubes increase greatly comparing with the Smooth Tube, and the values have some fluctuation. So it can be said that it is an effective way to improve the heat exchange performance by changing the structure. Finally, Created by CFX discrete solid boundary temperature and pressure of the fluid boundary as the boundary condition coupling transfer to ANSYS structural analysis software for heat transfer tube in the thermal stress calculation model to obtain the directions of wall thickness stress gradient and stress concentration.Temperature load makes greater impact on tube stress by comparing the stress. With the increase of import fluid volume, the maximum stress of different kinds of heat exchange tubes increase gradually.

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