Reducing temperature stratification using heated air recirculation for thermal energy saving

Using discrete heat sources such as a radiator or a gas heater, a large amount of heated air is accumulated under the ceiling surface where it is usually far enough from the occupancy zone. The idea of transferring this heated air into the occupancy zone has been the subject of the present study. A full length-scale model of a compartment was constructed and equipped with a radiator and an air circulating mechanism. Temperature distribution on the symmetry plane was specified for the two cases of usual heating and heating with air circulation. Heat loss from the surfaces of the enclosure was also determined using thermal maps of both the internal and the external surfaces of the enclosure. In order to examine the effect of circulating air on the thermal energy saving quantitatively, a numerical model was developed and validated using experimental results. The input heat rate of the enclosure was compared for the two cases of usual heating and heating with air circulation considering different heights for a typical heating space. Based on the results, having the same mean air temperature within the occupancy zone, the input heat rate of a compartment could be moderated using circulating air criterion.

• Energy saving is achieved by warm air recirculation in a space to be heated using discrete heat sources.
• Energy saving is increased as the height of the space is enlarged.
• Energy consumption of the equipments for air recirculation would be very negligible.