Optimising the performance of domestic wall mounted space comfort heater

Abstract

The performance of a wall Mounted space comfort heater has been studied with respect to the geometry of its mounting condition. Tests were conducted in a laboratory with the heater positioned at various heights from the floor and the channel that is created by the various gaps with the wall on which the heater was mounted. Tests were also performed with the heater mounted on the wall whose emissivity was adjusted to low, medium and high values as well as placing insulation material on the wall directly behind the heater. The outcome of the experiments revealed an acceptable geometry of the heater’s mounting at least 200 mm above the floor, and 50 mm off-set from the wall. The results of the heater mounted against the wall revealed a drop in performance as compared to the heater’s “benchmark” performance when it was freely standing on the floor of the laboratory; with an efficiency of about 41% (almost evenly shared by each face). This efficiency, which is based on the convective heat transfer generated by the heater’s warm/hot surfaces, is relative to the electrical energy input and it dropped when the heater was mounted against a grey wall to around 35%, of which only 26% was produced inside the channel. The heat transfer by radiation from the heater’s surface is treated as net loss to the walls of the room/enclosure.The performance of the heater when mounted against the wall improved almost to the benchmark value when the wall behind the heater was made refelective (low emissivity). It is recommended that further research should be undertaken to thoroughly investigate the “mode” of heat transfer, by the induced flow through the channel, in a more formal or scientific modelling approach.