Experimental study of natural convection in PV roof solar collector

An experimental study was carried out to investigate the intensification of the efficiency of a flat solar collector. To achieve this aim, we investigated the effect of the thickness of the air gap between the glazing cover and the plate absorber and the effect of presence of transparent partitions in the air gap. Indeed, when the thickness of the air gap is increased, the natural convection is intensified, which induces high thermal losses on the front part of the collector. The result of this study highlights that thicknesses larger than the reference one, given by the manufacturer, decrease the efficiency, while thicknesses smaller than the reference one increase the efficiency. The presence of transparent partitions in the air gap leads to the weakening of the natural convection and thus to the enhancement of the solar collector efficiency. Two situations were studied. In the first one, only transverse partitions were placed in the air gap; in the second one, longitudinal partitions were added to the transverse ones to form a crossed structure of partitions. The obtained results showed that in both situations the enhancement of the efficiency is significant and that the crossed structure induces the better efficiency.

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Experimental Investigation of Natural Convection in Partially Divided Enclosures

Journal of Heat Transfer ◽

10.1115/1.3246970 ◽

1986 ◽

Vol 108 (3) ◽

pp. 554-559 ◽

Cited By ~ 3

Author(s):

J. G. Symons

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Experimental Investigation ◽

Natural Convection ◽

Convective Heat Transfer ◽

Convective Heat ◽

Solar Collector ◽

Heat Transfer Characteristics ◽

Transfer Rates ◽

Slope Direction

An experimental study has been performed on natural convective heat transfer in inclined enclosures heated from below, and with partitions running in the up-slope direction (see Fig. 1). The influence of a clearance between the partitions and the lower heated isothermal surface is considered. This problem is of particular importance in solar collector design. Heat transfer rates have been measured for Ra < 107, enclosure inclination of 0, 30, 60, and 90 deg from the horizontal, and partition end clearances ranging from zero up to half the enclosure height. A flow visualization study which covers the same range of inclinations and end clearances is also reported. It is shown that introducing a small partition end clearance has no significant effect on the flow or heat transfer rates. However, a large end clearance allows up-slope rolls to be established in the unpartitioned region of the enclosure, resulting in an increase in the heat transfer rates. The natural convective heat transfer rates are found to be independent of both partition end clearance and enclosure inclination over certain ranges of these parameters. The convective heat transfer characteristics are also shown to be related to the flow.

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