Date of Award

2004

Document Type

Master Thesis

Degree Name

Master of Engineering (Research)

Department

Mechanical Engineering

First Advisor

Mr. Chris Gibbons

Abstract

The aim of this research was to explore the effects of mature and developing technologies from aeronautical industries such as impingement and film cooling, and electronic cooling techniques, in the setting up of different laminar and turbulent flow regimes on PV cooling duct heat transfer rates, with air flow as that brought about with natural buoyancy effects in a vertical building facade. The problem of efficiency losses in PV panels, due to overheating, is one of the factors restricting the development and use of this renewable power source. PV panels can experience very high temperatures, due to the heat input by that part of the absorbed solar radiation that is not converted directly into electricity. The technology behind injecting air coolant through perforations onto a hot plate surface is currently employed in solar air heaters, and in gas turbine blade cooling in industry. The turbulation research was adapted from technology currently being employed and developed in the gas turbine blade cooling area for the internal cooling passages of the turbine blades.

The research was undertaken through mathematical and Finite Element CFD modeling, with extensive experimental testing and subsequent analysis. Significant heat transfer enhancement was demonstrated, in most cases with an accompanying increase in pressure drop penalty, but with some cooling techniques proving to have remarkably efficient cooling mechanisms, even for the relatively low flowrates involved. The expanded exit hole orientated at 35° to the streamwise flow direction was concluded to be far superior to all other injection mechanisms examined, with heat transfer enhancement of 26.9%, 46.3%, and relative pressure penalties of 10.9%, 18.8% at the buoyancy induced flow rates. Dimple turbulators, particularly the optimised one, of lower pitch to diameter ratio (s/d=1.3), offered notably enhanced cooling of 6.2% and 11.2% at the buoyancy induced flowrates, with very low relative flow friction penalties of 3.5%, 6.4% at the corresponding flowrates. From the viewpoint of practicality, the dimple turbulator has the highest manufacturability potential, with no extra installation or maintenance problems to consider.

This research showed that under suitable flow conditions, and for different PV configurations, an increase in heat transfer and thus cell cooling is currently feasible and viable, and will result in increased electrical efficiency.

Access Level

info:eu-repo/semantics/openAccess

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