Year

2005

Degree Name

Doctor of Philosophy

Department

School of Mechanical, Materials and Mechatronics - Faculty of Engineering

Abstract

The rate of heat transfer in a cooling on a high temperature steel strip by an impinging water jet depends on various important factors, which mainly include the velocity of water jet impingement on the cooling surface, the initial temperature of steel strip, the temperature difference between cooling water and cooling surface, and the cooling surface conditions, etc. A good deal of experimental and computational work had been done to study the effects of these factors on the heat transfer rate in this current study. The objective of this study is to clarify the heat transfer characteristics during the cooling process by water jet impingement. Experimental study is mainly focused in this thesis. The selected test conditions are: 1) water jet impingement velocities, which were obtained by adjusting the water flow rate, water nozzle diameter and nozzle-to-surface space; 2) three water nozzles with different size in diameter; nozzle-to-surface spaces; 3) initial steel plate temperatures, which were obtained from heating the steel plate up in a furnace; and 4) flow visualization study by the digitized images of heat transfer, which were captured at 1000 frames per second by a high speed camera. The major findings and achievements of the presented work include the following: 1) measurements of transient temperature distribution on the surface of a hot steel plate during a cooling are successfully achieved by thermocouples. 2) flow visualization analysis is carried out to visually study the heat transfer characteristics by a high-speed camera; 3) programs are written to control the initial plate temperature and water flow rate, acquire the experimental data, and calculate and analyse the heat transfer results; 4) the current research presents the experimental results of the effects of jet velocity, initial temperature on the heat transfer rate.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.