真空管热水器倾角的数值模拟分析

利用fluent软件中的太阳载荷模型对真空管家用太阳热水器进行了三维数值模拟计算,分析了30°、45°、60°倾角下真空管热水器内的流场和温度场随加热时间的变化及传热和流动过程。结果表明,真空管热水器在加热期间,在真空管管口的上壁面出现温度最大值,水箱内真空管管口以下水的温度相对于管口以上的温度分层很明显,水箱内真空管管口以上的热水温度几乎相同,说明水箱内管口以上的水进行了充分混合;对于30°和45°倾角的系统,随着加热时间的增加,水箱内管口以下的水温与管口以上的水温从10 K增加到30 K,以45°倾角为例,当考虑了水箱内管口以下的冷水区时,随着加热时间的增加,真空管与水箱内的温差从0.73 K增大到1.13 K,仅考虑水箱内均匀分布的三点时,随着加热时间的增加,真空管与水箱内的温差从0.15 K减小到了0.03 K;随着系统倾角从30°增加到60°,水箱内管口以下的冷水区域在逐渐减小。因此,为了减小水箱底部的冷水区,插入水箱内的真空管应尽可能短。

Numerical simulation analysis on the influence of tilt angle on the evacuated tube water heaters

The solar load model of fluent software was used to conduct three-dimensional direct numerical simulations on the domestic solar water heater,and the velocity field and the temperature field with the heat time at tilt angles of 30°,45°,60° were obtained. The flow dynamics and heat transfer process of evacuated tube water heater system were analyzed. The results showed that,during the evacuated tube was heated,the top of the evacuated tube wall emerge the maximum temperature,the water temperature of the evacuated tube in the tank under the opening relate to the water temperature above the opening stratification was more obvious,and above the opening of the tank was almost the same,which illustrated that the water above the opening inside the tank mix fully; For the system tilt angle of 30 ° and 45 °,the temperature difference was from 10 K to 30 K between under the opening and above the opening in the tank with the heat time. In the case of 45 ° tilt angle,when considering the cold water under the opening in the tank,the temperature difference between the evacuated tube and the tank was from 0. 73 K to 1. 13 K with the heat time,only account for evenly distributed three temperature points inside the central surface of the evacuated tube and the water tank,the temperature difference between the evacuated tube and the tank was from 0. 15 K to 0. 03 K with the heat time; with the increase of the tilt angle from 30° to 60°,the area under the opening in the tank beceme smaller gradually. In order to reduce the cold water area at the bottom of the tank,the evacuated tube inserted into the tank should be as short as possible.