Thesis (M.S.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references (leaves 63-68). Also available via the World Wide Web.

Thesis (Ed. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 107-117).

Thesis (Ph.D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xvi, 147 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Joseph A. Krzycki, Dept. of Microbiology. Includes bibliographical references (p. 122-147).

Thesis--M. Phil., University of Hong Kong, 1974.

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published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Not available / text

Not available / text

In this work, we have numerically studied the effect of the vorticity on the enhancement of heat transfer in a channel flow. In the first part of the work, we focus on the investigation of a channel flow with a vortex street as the incoming flow. We propose a model to simulate the fluid dynamics. We find that the flow exhibits different properties depending on the value of four dimensionless parameters. In particularly, we can classify the flows into two types, active and passive vibration, based on the sign of the incoming vortices. In the second part of the work, we discuss the heat transfer process due to the flows just described and investigate how the vorticity in the flow improves the efficiency of the heat transfer. The temperature shows different characteristics corresponding to the active and passive vibration cases. In active vibration cases, the vortex blob improves the heat transfer by disrupting the thermal boundary layer and preventing the decay of the wall temperature gradient throughout the channel, and by enhancing the forced convection to cool down the wall temperature. The heat transxfer performance is directly related to the strength of the vortex blobs and the background flow. In passive vibration cases, the corresponding heat transfer process is complicated and varies dramatically as the flow changes its properties. We also studied the effect of thermal parameters on heat transfer performance. Finally, we propose a more realistic optimization problem which is to minimize the maximum temperature of the solids with a given input energy. We find that the best heat transfer performance is obtained in the active vibration case with zero background flow.

Laminar and turbulent natural convection heat transfer and fluid flow processes in asymmetrically heated vertical parallel flat plate channels have been investigated both experimentally and numerically. The experimental part of the investigation was carried out using a fibre optic Laser-Doppler Anemometer (LDA) together with a temperature probe and data acquisition system. The numerical analysis was done using the computational fluid dynamics (CFD) code PHOENICS. The laminar natural convection flow case was examined for a uniform heat flux (UHF) heating mode while the turbulent flow case was examined considering both UHF and uniform wall temperature (UWT) heating modes. Small and large scale channels were constructed to perform laminar and turbulent flow experiments respectively. The channels were formed by a heated wall, an opposing unheated perspex or glass wall and side walls. Velocity profile and time history data along the channel and temperature profiles at channel exit were recorded for the laminar flow case. In the turbulent flow case of UWT heating mode mean and turbulent velocity data and mean temperature data at the channel exit were collected. For the UHF heating mode turbulent flow case, however, both mean and turbulent velocity and temperature data were recorded. The main objective of the experiments was to obtain data by which the numerical analysis could be supported since not enough experimental data is available, especially for the turbulent flow case. The numerical analysis of the laminar flow situation was performed with the standard features of PHOENICS. The turbulent flow case was examined by building into PHOENICS the codes for four different Low Reynolds Number k-Ɛ turbulence models. The grid pattern was optimised for a test case and employed for final computations. Due to the lack of experimental data regarding the location of transition to turbulent flow, computations were done by introducing a level of turbulence at the inlet and solving the governing equations for turbulent flow throughout the channel. The results of measurements justified this approach. The results of numerical and experimental analysis of laminar flow showed good agreement confirming that the numerical method was capable of predicting the flow with good accuracy. Turbulent flow experiments exhibited the characteristics of a developing turbulent channel flow. Low amplitude, high frequency velocity fluctuations were observed close to the channel inlet with higher amplitudes downstream and almost similar fluctuation patterns in the uppermost region of the channel suggesting fully developed turbulence. The temperature data indicated intermittent bursts of high frequency temperature fluctuations near the inlet and continuous high frequency temperature fluctuations of increasing, amplitude downstream. Numerical results of the turbulent flow case have produced good agreement with experiments. The solutions were most sensitive to the level of turbulence introduced at the channel inlet. Reasonable grid independent solutions were obtained for grids greater than 60x60 for most of the turbulence models considered. Velocity and temperature profiles obtained from experiments and numerical analysis are presented for both flow cases. Typical time histories of velocity and temperature at different channel heights and cross-stream locations are presented. From the numerical and experimental results correlations were produced for Nusselt number, and Reynolds number as functions of Rayleigh number, for the UWT heating mode of turbulent flow.