Experimental Investigation On Heat Transfer Performance Of Grooved Heat Pipe

The grooved heat pipe is a heat pipe that uses the grooved structure to provide capillary force to make the liquid working medium return so as to realize heat transmission.Its structure is simple,the reliability is high,the gas-liquid two-phase carrying effect and thermal resistance between the grooved and the heat pipe are small.It has very good secondary processing performance,and will not fall off the wick and tube wall during the flattening and bending process,so it has received extensive attention and research.In this paper,the effects of structural parameters of grooved heat pipe on heat transfer performance of heat pipe are studied and expressed through test approach,and the feedback of different working fluids on the operation features of grooved heat pipe are contrasted.Finally,the running situation of large length horizontal solar heat pipe is talked over.The main research contents are as follows:（1）A batch of grooved heat pipes and solar heat pipes with different grooved structures are designed and manufactured independently,a performance test platform is built,the design of the experimental scheme is completed,the experimental data processing method is determined,and the uncertainty of the experimental system is calculated.（2）The heat transfer performance of grooved heat pipe is collected by running test with using water as working medium,compared with conventional gravity heat pipe,and the impact of shape data on heat conductivity is discussed.It is found that the existence of grooved structure can strengthen the heat transfer of heat pipe;The wall thickness and grooved depth restrict each other.The influence of wall thickness is greater at low power,and the influence coefficient of grooved depth becomes larger at high power;The grooved depth and number are interdependent.The number influence coefficient is large at low power,and the grooved depth influence coefficient is large at high power.When the grooved depth surpasses a certain numerical value,the influence factor amount of the grooved becomes larger.（3）The heat transfer performance of different working medium grooved heat pipes at different horizontal angles is experimentally studied and compared with that of hydraulic medium heat pipes.It is found that 0.15wt%n-heptanol solution can strengthen the heat transfer of heat pipes;The heat transfer performance of 0.10wt%nheptanol solution is poor,and the phenomenon of drying occurs under small heating power;The results show that the solution consistence effects the heat transfer performance of self-wetting fluid heat pipe;The heat transfer coefficient of absolute ethanol heat pipe is similar to that of water,and the limit power increases more,which is related to its small contact angle;The heat transfer limit of the two glycol solution heat pipes is small,which is not suitable for high-power working conditions.（4）According to the working characteristics of solar heat pipe,three working fluids with good heat transfer performance under low and medium power are selected to study their operating characteristics in long-level solar heat pipe.It is found that the self-wetting liquid solar heat pipe has shortest start-up time,and the temperature and thermal resistance of evaporation section are much lower than the other two working fluids;Absolute ethanol and ethylene glycol heat pipes have similar heat transfer performance at low power,but absolute ethanol has better heat transfer performance at high power.