Published 4 issues per year
ISSN Print: 2151-7975
ISSN Online: 2151-7991
MULTI-PARAMETRIC INVESTIGATION ON THE THERMAL INSTABILITY OF A CLOSED LOOP PULSATING HEAT PIPE
ABSTRACT
In the present work a Closed Loop Pulsating Heat Pipe (CLPHP) made of copper (I.D. 1.1mm, O.D. 2mm) is filled with FC-72 as working fluid. Different parameters such as the heat input level, the tilting angle and the filling ratio are investigated in order to highlight their effects on the occurrence of unstable operation. The CLPHP with filling ratio = 0.5 shows the best performance, but also undergoes thermal instabilities directly related to the combined effect of orientation and the heat input level. The CLPHP in the horizontal position is less efficient, but no performance drop occurs until the maximum heat input level is reached. The CLPHP charged with 70% liquid is less efficient, even if it shows a more stable operation, with only one sudden performance drop during the vertical operation. In this case, contrary to stable operation, thermal instability is characterized by large amplitude temperature oscillations and an uneven temperature space distribution.