Applying Of Pulsating Heat Pipe Heat Exchanger In Air-Conditioning System For Thermal Energy Recovery

Pulsating heat pipe(PHP),being a relative new member in the family of heat pipe with simple structure and excellent heat transfer performance,has found successful application in the cooling of micro-electronics.Another advantage of the PHP is that when it is well-designed,its heat transfer performance is little influenced by the gravitaty vector.Based on a comprehensive analysis of this issue,we extend the application of PHP to air-conditioning system for heat recover. Here are some research works and conclusions:1.According to the design method for the gravity heat pipe heat exchanger,we designed a preliminary PHP heat exchanger,on which some experiments were performed to invstigate the start-up characteristics and influence of heat transfer performance.It is found that as the wind velocity is in the range of 2.2-2.8m/s,the minimum start-up temperature difference between hot and cold air is 4℃and 9℃for the PHP heat exchanger in summer and winter conditions respectively. Referring to the impacts of heat exchanger efficiency,it is found that the temperature has greater effect than the wind speed. 2.we compared our experiments with that of Mostafa A on the gravity heat pipe heat exchanger.Results show that both types of heat exchangers showed the similar heat transfer characteristics generally, while the PHP need a smaller start-up temperature difference between hot and cold air,showing better heat transfer performance than the gravity heat pipe,when the air temperature in evaporation section is in the range of 30-35℃.In addition,the volume and the consumption of copper in our present PHP heat exchanger is about 89%and 54%in the compared gravity heat pipe heat exchanger respectively.Thus,the PHP heat exchanger shows a greater potential application in the air-conditioning and ventilation system for energy recovery.3.When the PHP heat exchanger was operated in the reversal situation with the lower heat loads,the gravity vector had greater effect on the thermal efficiency.As the increasing of heat loads and temperature differences between the hot and cold air,effect of gravity vector is smaller and smaller.4.An economic analysis was evaluated on the benefits of the PHP heat exchangers in a shopping mall of Shanghai.The results showed that, the air-conditioning system can save 363.1×10~3KW·h electricity and 224,000 Yuan every year after the installation of the PHP heat exchangers. The recovery period of the equipment investments is about 1.88 years, showing the significant economic and social benefits.