Thermal performance characteristics of a pulsating heat pipe at various nonuniform heating conditions

A pulsating heat pipe (PHP) is an excellent cooling device based on the phase change of a working fluid. However, the performance of the PHP can be degraded by nonuniform heating conditions in the evaporator section. The objective of this study is to investigate the thermal performance characteristics of a PHP at various nonuniform heating conditions. The thermal performance of the PHP is measured by varying the dimensionless heat difference from 0 to 0.3, heat input from 30 to 100 W, and filling ratio from 50% to 70%. As a result, the optimal filling ratios for the best PHP performance and reliability are determined to be 50%, 60%, and 70%, at the dimensionless heat differences of 0, 0.2, and 0.3, respectively. In addition, the thermal resistance and evaporator temperature difference of the PHP increase with an increase in the dimensionless heat difference owing to the decreased driving force. Finally, contour maps for the effective thermal conductivity are proposed to provide design guides of PHPs.