Experimental Study On The Influences Of Cold Air Infiltration On The Indoor Environment In A Heating Room By Warm Air

Mixing ventilation(MV) is typically used for summer cooling and winter heating with warm air, as a major heating air system, the MV is widely used in public buildings for many years, In the entrance to a building, however the outside doors’ frequent open will cause large amount of cold air enters the interior, so it is important to study the influence of cold air incursion to the heating room by warm air.In a phytotron, when the supply air volume keeps constant, experiments are carried out to explore the effects of mixing ventilation in heating mode with cold air incursion for some representative cases, the influences of amount of invading cold air and invading frequency on indoor thermal environment are analyzed. The results indicate that the invading frequency has weak effects on the temperature of the heating room, it only affects the amplitude of the indoor air temperature fluctuation, i.e. the amplitude of the indoor air temperature fluctuation increases with the decrease of cold air invading frequency. With the increase of the amount of the incursion air, the indoor temperature gradient becomes larger and the heating energy utilization rate is reduced. So under the situation with significant cold air infiltration, high supply velocity is an important way to reduce the negative effect of cold air incursion.In addition, the energy utilization factor η is commonly used to measure the heating energy utilization rate; PD(percentage dissatisfied) and the temperature contrast between the ankle and head levels measure the indoor thermal comfort when warm air is used for heating. In a climatic chamber, experiments are carried out to study the effects of mixing ventilation used in heating mode with different cold air incursion and same supply air volume, and the influences of amount of invading cold air and velocity on indoor velocity distribution, heating energy utilization rate and indoor thermal comfort are discussed. The results show that there is no obvious draft for all air velocities used; The amount of invading cold air has no effects on indoor velocity distribution when the air velocity keeps constant and all meet the requirements of indoor thermal comfort; By increasing the speed of the air achieve a direct service to near the ground for resisting invasion of cold air, this improves the heating energy utilization efficiency; Under the situation with significant cold air infiltration, lager air velocity can reduce the PD and cephalopods temperature difference with better indoor thermal comfort.