Experimental Investigation On Heat Transfer Performance Of Closed-loop Pulsating Heat Pipe With Different Inner Diameter And Chan Channel Shape

Pulsating heat pipe is a new type of heat exchange device with high efficiency, and it has some obvious advantages:simple construction, low cost, high heat transfer efficiency and strong adaptability. The PHP is made of capillary pipes, in which the working fluid can form the distribution of the vapor plug and liquid slug due to the effect of surface tension. When the PHP operate, the heat was transferred through the oscillation motions of the vapor plug and liquid slug. Therefore, it is considered as one of the most promising methods to meet the challenges of electronic heat dissipation in the current and future, and it also has a very good application prospect in the field of space.At present, a lot of researches have been done on both the theory and experimental investigations. Based on a series of theoretical assumptions, the mass equation, energy equation and momentum equation were used to establish an analysis model of pulsating heat pipe with both circular channels and rectangle channels. The simulation was carried out and the conclusions showed that the thermal resistance of pulsating heat pipe decreased with increasing of heat flux under the working conditions. The decreasing slowed down with the heat flux. At the same time, there existed different best charge ratios for circular channel pulsating heat pipe with different inner diameters. Besides, the ratio of latent heat to sensible heat during the heat transfer process increased with the increasing of the heat flux, and decreased with the increasing of the charge ratio.In this thesis, four pulsating heat pipe experimental setups with circular channel (inner diameter is 1 mm,2mm,3mm,4mm, respectively) and one pulsating heat pipe experimental setup with rectangle channel, which equivalent diameter is 4 mm were built. The experimental results were analyzed to figure out the influence of inner diameter and channel cross-shape on the start-up characteristics, the minimum start-up power, the optimum charge ratio, the thermal resistance and the dry out characteristics of the PHP. The following were the results:1)When the input heating power exceeded the minimum start-up heating power, the start-up time of pulsating heat pipe got shorter with the increasing of heat flux,2) the start-up pattern of pulsating heat pipe changed from temperature sharp changed pattern to temperature stable changed pattern.3) When the diameter became larger, minimum start-up power of pulsating heat pipe with circular channel increased, and the optimum charge ratio and the thermal resistance decreased. Local dry-out phenomenon might occur at the low charge ratio. Under the same operating conditions, the pulsating heat pipe with rectangle channel had lower thermal resistance and optimum charge ratio than that with circular channel. However, pulsating heat pipe with rectangle channel was much more difficult to start up, so that the minimum start-up power was larger.