Determining Non-visually The Pulsating Heat Pipe Working States And Investigating Its Thermal Transport Performance

Pulsating heat pipe(PHP)'performance test rig was established to investigate the relationship between the flow patterns and the characteristics of oscillating curves of temperature, and the operation state of PHP was analyzed and judged through non-visual method. By combining with the change of the flow pattern, the factors which affected the thermal transport properties of PHP, such as fill ration, inclination angle, the mass flow rate of heating/cooling fluid were studied in this paper. Furthermore, the heat transfer enhancement of PHP was studied by adding nano-particles into PHP working fluid.First, the force of PHP working fluid was preliminary analyzed. Then, through the proper arrangement of thermocouples, the method of determining PHP operating states of PHP by means of non-visualization was obtained: through the output of the temperature sample signal, the bubble flow, slug flow, pushing flow, annular flow was found, and the mechanism was analyzed, which are associated with the temperature measurement values. Further, a new way was used for the first time to determine the PHP's work states, which includes how to determinate both the start-up stage and the steady stage by the means of non-visualization that is relied on the temperature values of interface between the heating section and cooling section of PHP. This lays a foundation for PHPs'practical used in refrigeration, air conditioning, heat recovery equipment to determine the optimum operating state.The influence of some factors on the thermal transport performance of PHP has been researched. The factors include the working fluid within different fill ratio, inclination angle of PHP heat exchanger and the mass flow rate without heating medium in the heat section and cooling medium in the cooling section. The experimental results show that when the PHPs startup, the heat transfer quantity is increased with fill ratio of working fluid and inclination angles; PHP could startup at a lower heating temperature when the fill ratio and inclination angle at a lower value.Finally, in order to improve the heat transfer capacity of PHP, a kind of nano-particles A was added into a pure working fluid to form a miture.. Experiments with the mixed working fluid found that the heat resistance decreases and the heat transfer capacity increases. Moreover, the inlet temperature of heating medium is significantly reduced under a certain conditions. Therefore, adding nano-particles into the working fluid of PHP could enhance heat transfer and improve the thermal transport performance of PHP, and at the same time reduced the difference of heating and cooling medium temperature. It lays a foundation for the further research the performance of PHP used in low-temperature differential thermal transport, for example: air-conditioning heat recovery devices.