Experimental Study On Pulsating Heat Pipe For Cold And Heat Recovery In Air-conditioning

Pulsating heat pipe (PHP), which is a new type of highly efficient heat transfer original with advantages of simple structure and excellent heat transfer performance. 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 this good point and previous studies of this topica, the paper improve the design of PHP heat exchanger, using it in air-conditioning exhaust energy recovery systems. The test setup was Designed and built to further study their heat transfer performance in the air-conditioning exhaust heat recovery systems, also the minimum start-up temperature difference was measured. The relationships between the factors (wind velocity, temperature difference between the fresh air and the exhausted air, inelination angle) and the Performance of PHP heat exchanger were analyzed. Here are some research works and conclusions:Firstly, improving the design of PHP heat exchanger. The PHP increases to 40 by the 8 roots, corresponding to five-fold increase in the number elbow. We compared it with the PHP heat exchanger of previous studies of this topica on their heat transfer performence. Results show that, the PHP heat exchanger has more heat transfer and its heat performance is greatly improved in the same conditionsSecondly, it has minimum activated temperature difference for the PHP heat exchanger. It is found that the wind velocity is in the range of 2.0-3.0m/s, the minimum start-up temperature difference between hot and cold air is 2℃for the PHP heat exchanger in summer condition.Thirdly, there has some influencea factors for heat transfer Performance of PHP heat exchanger, such as wind velocity, the evaporator air temperature and inelination angle. The effectiveness become smaller at first and after it reaches the smallest point it became bigger with increasing of the rate ratio between return and fresh air, and the smallest point was at the 1 rate ratio. With the evaporator air temperature increasing, the efficiency is increasing. Its effectiveness become bigger at first and after it reaches the biggest point it became smaller with increasing of inelination angle (from 0°,30°,60°to 90°), and the biggest point was at the 60°inelination angle. We compared PHP heat exchanger with the thermosyphon heat exchanger on their heat transfer performence. Results show that both types of heat exchangers showed the similar heat transfer characteristics generally. With the evaporator air temperature increasing, air temperature difference between imports and exports and the efficiency also increases, both for evaporation section and condensation section. The evaporation section air temperature between 30-35℃usually in summer conditions, data shows that the PHP minimum start temperature is smaller in this range. Therefore, the PHP heat exchangers in air-conditioning exhaust heat recovery system exist a lot of potential applications.