Thermocirculation characteristics of a Trombe wall passive test cell

Abstract Passive heating, using Trombe wall elements for solar energy collection, can be readily integrated into new building structures and can be retrofitted to existing buildings. Although the basic physical principles underlying the natural operation of such air thermosiphon devices have been well known for many years now, there is still insufficient design information available to allow sensible sizing and installation decisions to be undertaken by architects and thermal system designers. In this experimental investigation, flow visualisation studies have given a deeper insight into the fundamental flow mechanisms; whilst air velocity and temperature measurements have been used to explore the natural convection heat transfer processes involved in the thermocirculation flow. Particular attention has been paid to the effects on operational performance of the wall parameters such as wall/glazing distance and vent size. Adequate data correlation of the experimental results has been achieved by using expressions derived for natural (free) convection processes occuring between vertical paralled plates; in this case the vertical heated wall surface and the cooler vertical glazing panel. It is felt that this type of fundamental heat transfer information is vital so that the overall performance of Trombe wall systems can be adequately modelled using the large range of simulation techniques currently available for thermal network analysis.