Local heat transfer measurement and thermo-fluid characterization of a pulsating heat pipe
Local heat transfer measurement and thermo-fluid characterization of a pulsating heat pipe
复制标题
DOI：
10.1016/j.ijthermalsci.2013.07.025
复制
发表时间：
2014
影响因子：
4.5
通讯作者：
M. Mameli;M. Marengo;S. Khandekar
中科院分区：
文献类型：
--
作者：
M. Mameli;M. Marengo;S. Khandekar
设计了一种紧凑型闭环脉动热管（CLPHP），以乙醇（65%v/v）为工质，由四根透明玻璃管组成绝热段，蒸发段和冷凝段分别用铜U形弯管连接，以进行全面的热工水力性能研究。局部传热系数是通过测量蒸发段管壁温度和内部流体温度来估算的。同时，流体压力振荡与相应的流动模式一起被记录。热性能测量不同的热输入水平和全球定位的设备相对于重力。还用乙醇和水的共沸混合物进行了一项探索性试验。结果表明，只有在局部脉动流的基础上建立循环流模式，才能实现稳定的装置运行（即蒸发器壁温达到准稳态）。传热性能强烈地依赖于热输入水平和倾斜角度，这反过来又影响随后的流型。的压力信号的频谱分析表明，即使在稳定的性能制度，特征流体振荡频率不是唯一可识别的。获得的等效热导率为纯铜的10-15倍。由于匝数少，水平模式操作不可行。初步结果表明，与纯乙醇相比，填充乙醇和水的共沸混合物作为工作流体不会改变热性能。
A compact Closed Loop Pulsating Heat Pipe (CLPHP), filled with ethanol (65% v/v), made of four transparent glass tubes forming the adiabatic section and connected with copper U-turns in the evaporator and condenser sections respectively, is designed in order to perform comprehensive thermal-hydraulic performance investigation. Local heat transfer coefficient is estimated by measurement of tube wall and internal fluid temperatures in the evaporator section. Simultaneously, fluid pressure oscillations are recorded together with the corresponding flow patterns. The thermal performances are measured for different heat input levels and global orientation of the device with respect to gravity. One exploratory test is also done with azeotropic mixture of ethanol and water. Results show that a stable device operation is achieved (i.e. evaporator wall temperatures can reach a pseudo-steady-state) only when a circulating flow mode is established superimposed on local pulsating flow. The heat transfer performance strongly depends on the heat input level and the inclination angle, which, in turn, also affect the ensuing flow pattern. The spectral analysis of the pressure signal reveals that even during the stable performance regimes, characteristic fluid oscillation frequencies are not uniquely recognizable. Equivalent thermal conductivities of the order of 10–15 times that of pure copper are achieved. Due to small number of turns horizontal mode operation is not feasible. Preliminary results indicate that filling azeotropic mixture of ethanol and water as working fluid does not alter the thermal performance as compared to pure ethanol case.