Start-up characteristics of super-long gravity heat pipe
As a novel single-well heat exchange technology,the super-long gravity heat pipe has broad application prospects in the development and utilization of geothermal resources.The rapid start-up of heat pipe is the basis for efficient and stable operation.However,the current research on the start-up characteristics of super-long gravity heat pipes is still in its infancy.This paper uses a visual experimental platform for super-long gravity heat pipes with a length of 40 m,an inner diameter of 7 mm,and an aspect ratio of 5714 to study the start-up process of the super-long gravity heat pipe and analyze its influencing factors.The results show that the start-up modes of the heat pipe vary with changes in the heating power and fill height,primarily categorized into gradual temperature variation,steady transition,and abrupt temperature change types.As the heating power increases from 100 W to 500 W,the rate of vapor-liquid phase change within the tube accelerates,and the start-up temperature rises from approximately 43.5℃ to 81.4℃.Consequently,the overall start-up time of the heat pipe is reduced by about 51％.When the power increases from 200 W to 300 W,distinct geyser boiling phenomenon begin to occur within the tube,leading to an increase in the resistance to the reverse flow of vapor and liquid.Consequently,the start-up time of the heat pipe does not decrease but instead increases.As the heating power continues to increase,the start-up time decreases.Under a fixed heating power condition(300 W),as the liquid fill height increases from 6 m to 15 m,the start-up time of the heat pipe initially decreases from 6455 s to 3354 s and then increases to 4575 s.Moreover,the shortest start-up time of the heat pipe occurs at the fill height of 9 m(3354 s).When the fill height is set at 3 m and the heating power is increased to 300 W,a significant amount of condensate is carried up to the adiabatic section and into the condenser section.This leads to localized dry-out in the evaporator section,making it difficult for the heat pipe to operate stably and ultimately resulting in start-up failure.Further experimentation revealed that under the same heating power and fill height conditions,shortening the length of the heat pipe's evaporator section can effectively reduce the start-up time(by approximately 56％),increase the start-up temperature,and result in a more stable temperature variation in the evaporator section.
万方数据
维普
