Effects Of Load Source On The Indoor Air Temperature Distribution Of A Large-height Space With A Warm Air Heating System

With the increasing requirements of indoor visual environment in buildings, flat skylights andfrench windows or low windows are more and more popular in current days. Due to the poor andlimited insulation performances of window glasses, the inner surface temperature is low, and thusthe cold air near the surface has a significant effect on the spatial distribution of the indoor airtemperature. Especially in a large-height space, a large area of low temperature glass has a coolingeffect to the air near the surface of the glasses, this will obviously affect the indoor air temperatureand air speed distributions.In the large-height spaces, the behaviors of the rising warm air lead to the higher airtemperature in the upper region of the space and the lower temperature in the bottom. Iflarge-height spaces are heated by stratified air supply, more heat would be delivered directly to theoccupants’ zone in the lower part of the spaces. In order to study the effects of the source of loadon large-height spaces’ indoor thermal environment with warm air heating systems, numericalsimulations have been carried out to explore the indoor air temperature and air distributions in thelarge-height spaces with large areas of flat roof or side windows, and the numerical scheme isvalidated by test data.The results show that when the load comes from the flat skylight, the air velocity in thenearby region of the skylight is obvious higher than the nearby regions without windows, air willbe cooled by the skylight and drops to the lower part of the space, this effect will lead to a uniformdistribution of the indoor temperature, and then the air is fully mixed in the whole space. Thus,different air return ways, different heights of the space, different heights of inlet and whether thereis heat source or not in the space have no effect on the indoor thermal environment in this kind oflarge space. When outdoor air conditions change, in order to ensure that the lower region of thespace (no more than2m above the floor) still meet the demand of thermal comfort, the use of theconstant air volume is better than the use of the variable air volume in thermal comfort for the occupants.When large windows are located on the sidewall, no matter french windows or low windows,the air velocity in the nearby area is also obvious higher than the nearby area without windows,the air cooled by the cold surfaces of the windows is sinking along the windows and continue toaccumulate gather, and eventually forms cold air layer in the zone near the floor, it not only causesa great gradient of the indoor temperature, but also prevents warm air into the occupant zone bythe buoyancy. In this kind of large space, the inlet height, the space height and whether there isheat source or not in the space have a significant effect on the indoor thermal environment. Theaverage temperatures in the whole space and the occupants’ zone can be effectively improved byreducing the height of the supply inlet, increasing the height of the space and putting heat sourceon the lower part of the space. When the load comes from ordinary windows, increasing the heightof the sill, the temperature in the lower region will be increased, but the temperature in the upperregion will not be changed obviously.