Influence Of Supply Air Parameters On Indoor Thermal Performances Of Warm Air Heating Rooms

In hot-summer and cold-winter climatic zone of China, warm air heating are usually adopted to maintain indoor thermal comfort of office buildings in winter. Compared with that in the northern regions of China, the set values of the supply air parameters in design of an air-conditioning system mainly meet the requirements of summer indoor thermal environment in this climatic zone. It may result in the waste of energy for heating while the situation that the indoor temperature can not match the requirements of human thermal comfort in winter. Consequently, it’s important to choose proper supply air parameters for getting a comfortable indoor thermal environment. In the present study, field experiments were conducted to study the indoor thermal environment and the influence of supply air parameters on indoor thermal performances of warm air heating rooms.The measurements were conducted in an office room with oversized glass windows, which was located in hot-summer and cold-winter climatic zone. During the heating period in winter,.18experiment conditions were conducted with different supply air velocities and initial indoor temperatures. The analysis focused on indoor thermal environmental features, such as average indoor temperature and the temperature difference between head and feet of human bodies. In addition, the energy consumption was compared with different conditions.The results show that due to large window-to-wall ratio and improper ventilation parameters, it is difficult for the warm air to reach the occupied space. This leads large temperature difference between the upper space and lower space and energy waste during the heating process. Meantime, as the window is weak at thermal insulation, thermal bridge effect and non-uniformly temperature distribution can be caused. The temperature near the window is obviously lower than the average temperature in a heating room. In the present air-conditioning systems, raising supply air velocity can reduce the non-uniform of temperature distribution, as well as the amount of heat load increasement caused by the non-uniformly indoor temperature distribution. The thermal comfort and energy-saving can be achieved by decreasing supply air temperature difference and increasing supply air flow rate. However, winter heating demands have to be taken into consideration in the initial design of ventilation system. Another effective method to improve thermal comfort is to open the ceiling fans, so that roof-attached warm air can be driven downward. As a consequence, the temperature in occupied space increases obviously and temperature gradient reduces. It means that coefficient of utilization is greatly promoted and energy-saving effect is significant, but the draught sensation may be caused at the same time.