Experimental evaluation of natural heat transfer in Façade Integrated Triangular Enclosures

Piratheepan, M
Anderson, T
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Australian PV Institute (APVI)

The use of building integrated solar concentrators is an area of developing interest within the field of energy-efficient building technology. One way of achieving such a device could be through the use of a flat static reflector used in conjunction with a photovoltaic/thermal absorber and glazing, thus forming a triangular enclosure similar to a single sided V-trough enclosure. Such systems may be well suited to adoption in façade applications. However, in order to precisely predict the performance of such building integrated façade collectors, it is crucial to understand the heat losses from the absorber. Unlike a flat plate collector, the glazing is not parallel to the absorber plate hence we need to develop a relationship that describes the thermal losses through the vertical glazed cover. As the air between the collector and the glass is isolated from the atmosphere, the thermal loss from the absorber to the glass cover will be due to natural convection and radiation. The radiation heat transfer can be readily determined using view factors, however there is no relationship in the literature to describe the natural convection heat transfer in triangular enclosures similar to the one illustrated. In this study, a relationship to describe the natural convection heat transfer in such triangular enclosures was experimentally determined. The relationship shows that the heat transfer, expressed in terms on the Nusselt number, is strongly dependent on the Rayleigh number and can be expressed by a relationship of the form of Nu=a〖Ra〗^b.

2014 Asia-Pacific Solar Research Conference held at University of New South Wales, Sydney, 2014-12-08 to 2014-12-10, published in: Proceedings of the 2014 Asia-Pacific Solar Research Conference
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