Influences Of The Location And Aera Of Transparent Envelope On Thermal Performance Of Warm Air Heating In Large-height Spaces

Energy consumption is now an important issue in China,and building energy consumption accounts for about 23%,particularly,building heating and cooling energy consumption are the main components of building energy consumption.In a large-height space needing warm air heating in winter,hot air will float because of buoyancy so that heat will accumulate in the upper space,resulting in the relatively low temperature in staff room,so the energy consumption problem of warm air heating has been the major concern of HVAC.In recent years,the ratio of transparent envelope(glass window)is gradually increasing in urban buildings,which further aggravates the contradiction between the accumulation of hot air in the upper space and the heat demand of the personnel space in large-height space with warm air heating.When the building have a large proportion of transparent envelope on the side wall,due to the low temperature on internal surface,the air around is cooled,sinks to the lower part and accumulates there,leading to a larger temperature difference between the upper and lower room in large-height space.In this paper,the reliability and accuracy of the numerical simulation method are verified by exper iment,and then the numerical simulation method is applied to the large space that this paper needs to study..The impacts of area and location of transparent envelope on the effect of warm air heating in large-height space are investigated by numerical simulation method.The results show that when the air velocity and the tuyere area are constant,due to the interference of the sinking cold air near the inner surface of sunroof to the floating hot air,the increase of the sunroof area can effectively reduce the indoor vertical temperature gradient,and the temperature drop in staff room is not significantwith the glass area increasing.And then due to the acceleration of the sinking cold air near the inner surface of side window to the floating hot air,the indoor temperature stratificates obviously,and the increase in side window area will signif icantly increase the indoor vertical temperature gradient and obviously reduce the personnel space temperature.Therefore,although the total area of the glass is constant,the staff room temperature will decrease significantly and the vertical temperature gradient increases as the window moves from the roof to the side wall.The increase of the glass area on the roof and on the side window will both increase the energy consumption,but the energy consumption increase of the former is not obvious and the indoor vertical temperature gradient is reduced,while the latter will greatly enhance the indoor thermal stratification,and signif icantly increase the heating energy consumption.In order to improve the heating effect of large-height space with large transparent envelope,it is better to reduce the indoor vertical temperature gradient by increasing the air supply velocity than by increasing air supply temperature,and what's worse,the latter even increases the indoor vertical temperature gradient,meanwhile,the energy-using coefficient decreases.