Natural convection heat transfer in V-trough solar concentrators

•Natural convection heat transfer in a V-trough is experimentally characterised.•A new correlation for V-trough solar concentrator heat loss is presented.•An existing correlation’s range of applicability is extended.

The use of V-trough concentrators offers a simple approach to increasing the radiation incident on a solar receiver; this is particularly useful for increasing the temperature in thermal systems. However in order to accurately predict the performance of thermal systems under concentrated radiation, there is a need to understand the heat loss from them. This study experimentally shows that, for a laterally and longitudinally inclined enclosed V-trough concentrator, the natural convection heat loss can be predicted using an equation of the form Nu = aRab for Rayleigh numbers between 2 × 103 and 1 × 108. It is suggested that the relationship is a good representation of heat transfer in enclosed V-trough concentrators under most practical orientations, and thus lends itself for implementation into design models for V-trough concentrators.