Date of Award

2018

Degree Type

Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

First Advisor

Ting, David

Second Advisor

Ray, Steve

Keywords

heat transfer; hot wire anemometer; tripwire

Rights

CC-BY-NC-ND

Abstract

The current study focuses on the cooling of photovoltaic panels by utilizing a two-dimensional bluff body. A bluff body placed on the surface of a flat plate acts as a vortex generator in the near-wake, and a turbulence generator in the far-wake. As a result, the boundary layer over the flat plate becomes turbulent and conducive to heat transfer from the plate. As an exploratory experiment, a circular tripwire was used to augment the fluid turbulence over a flat plate. The measured flow parameters showed good potential for heat transfer augmentation. The second experiment measured heat transfer and flow with circular, square and diamond-shaped tripwires placed on a smooth plate. The experiments were performed at two Reynolds numbers (Red) based on the freestream velocity and diameter (d) of the tripwire. The heat transfer rate of the square and diamond-shaped tripwires was improved over a large downstream region. The peak normalized Nusselt number (Nu/Nuo) of the diamond-shaped tripwire was observed to be around 1.4, and that of the square tripwire was around 1.2. The third experiment investigated the effect of introducing a gap (G) between the top of the smooth plate and the bottom of a diamond-shaped tripwire. Heat transfer and flow parameters for six G/d ratios were measured. When the tripwire was placed on a smooth surface, the flow structure of a smooth plate downstream of the tripwire (i.e., flow separation and reattachment) had a significant impact on heat transfer. When a gap was introduced between the smooth plate and tripwire, the von Kármán vortices shed by the tripwire interacted with the smooth plate, improving heat transfer. The turbulence produced by the tripwires, especially near the plate surface, significantly improved the Nusselt number in the far-wake. Wall-normal velocity is also an important factor in improving the heat transfer rate.

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