Study on Load in Upper and Lower Zones of Stratified Air Conditioning Technology of Terminal
|Course||Heating,Gas Supply, Ventilation and Air Conditioning Engineering|
|Keywords||Terminal Stratified air conditioning Load distribution Boundary conditions CFD calculating|
Stratified air conditioning only have the lower region of the large space was conditioned,and it was widely used in large space in order to maintain a certain temperature and humidity. Experience coefficient method often used to calculate the stratified air-conditioning load. Air conditioning load designed significantly influenced the effect of energy saving of stratified air conditioning technology.Air conditioning mode, load composition, development status and problems existed in the study of stratified air conditioning technology was analyzed through access, retrieve a large number of relevant literature. Analysis shows that available information of stratified air-conditioning load distribution for terminal are few,and Empirical coefficient was gave with value of 0.5 to 0.85 for proposal. The terminal building which has a different characteristics from general large space, and it has a need for further study. Indoor load reflected to boundary condition are over single in CFD calculating, and it’s not suitable for load study. Some papers not pay enough attention to the boundary conditions which affecting the accuracy of the results.In the above context, T1 terminal was choosed and physical and mathematical model was established according to the design information of the terminal.Full day air-conditioning load of testing day was calculated combined with the data measured, and then it was allocated in the upper and lower areas in different proportions. Load distributed in upper and lower areas of stratified air-conditioned terminal was determined by the best fit of calculated and measured vertical temperature distribution. This boundary conditions set method can provide reference for stratified air-conditioning in terminal when using a CFD methods in study.The testing results shows that relatively confined space of terminal is still in cooling condition in winter, and indoor temperature were too high. relative humidity only maintained at between 18.5% -27%. It proposed that typical characteristics of return air temperature should be modified to avoid the phenomenon that indoor temperature is generally high. Humidity distribution shows that high humidity areas such as Chengdu still need to take measures to meet the personnel requirements of comfort. In summer, the indoor vertical temperature rise after the first drop air temperature near the outlet±0.5m is most likely to accumulate,this is different from winter. indoor temperature gradient in summer is much larger than winter, the temperature between 4.0m ~ 8.0m increase more than 5.0℃. Affected by solar radiation, average temperature of the roof reached 41.8℃, much higher than the winter to 25.3℃, it is necessary to take measures to discharge the hot air to improve the indoor thermal comfort.The indoor and outdoor temperature, occupant density, the distribution of lighting and equipment subject to test day records,and Solar radiation data insteaded by the typical meteorological year’s data.The results show that the lower part of the region distributed about 2/3 of the total load is the best. The temperature can ensure 8.0m predictability height in winter and 6.0m predictability height in summer. Difference between calculated and measured values of temperature during the predictable height was basically controlled less than 0.5℃. As the influencing factors of air-conditioning load are too much, so the conclusion apply only to a similar stratified air-conditioning in terminal.Research methods used to set the boundary conditions can also be a reference for similar terminal stratified air conditioning research.