改进型回路脉动热管可视化及传热性能研究动力工程及工程热物理专业论文.docx

ABSTRACT Pulsating heat pipe (PHP) is a kind of new efficient heat transfer element, which is paid more attention for cooling technology requirement improving. It possesses simple structure. However, working fluid state in PHP is gas-liquid two-phase flow, which causes complex operation mechanism of PHP. Experiment and theory study need constant improvement, so practical engineering can be provided technical support. Visualization and heat transfer performances were investigated by experiment. Research targets were as follows: (1) Observation of flow pattern and flow mode of improved closed loop PHP. (2) Analysis of start and operation characteristic curve. (3) Analysis of heat transfer performances. (4) Analysis of nonlinear chaotic performance. Specific research contents were as follows. There were three visual specimens. Distilled water, ethanol and acetone were used as the working fluids. It was found that flow pattern of working fluid included bubbly flow, plug flow and mixed flow (plug flow and annular flow), but there was no annular flow distributed in the whole channel. Flow modes of working fluid were investigated with different stages (filling liquid stage, start, operation stage), inclination and filling ratios. Start and operation characteristic curve of improved closed loop flat plate PHP was studied with specimen NO.2. Start of PHP is of temperature progressive start, that is to say, temperature rows slowly to stable operation temperature and then steps into stable operation stage. Moreover, input power, inclination, filling ratio, thermal properties of working fluid and cooling water flow on start were investigated. Heat transfer performances of improved closed loop flat plate PHP were studied by specimen NO.2 and specimen NO.3. It was found that there was the optimal cooling water flow during operation. Heat transfer limit can be improved to some extant with cooling water flow increasing, which is more obvious with inclination. Heat transfer perform