TRANSIENT BEHAVIOR OF NON-UNIFORM PULSATING HEAT PIPES UNDER DIFFERENT HEAT LOADS

Pulsating heat pipes (PHPs) are among the up-to-date solutions for thermal management problems. In this study, under increasing and decreasing heat loads with irregular steps, a flat-plate type closed loop pulsating heat pipe (FP-CLPHP) having non-uniform channel design and charged by binary mixtures is experimentally examined at transient conditions. The results are presented in a comparative approach with the uniform-channeled FP-CLPHP. Operational range covers different filling ratio (FR = 25% and 45%), inclination angles (IA = 0 degrees and 90 degrees), and variable heat loads (respectively: 10 W, 35 W, 25 W, 40 W, 30 W, 20 W). Each heat load is applied for five minutes. Flow images are taken to present flow mechanism and to exactly discuss the measurements. It is concluded that thermal resistance can be reduced up to nearly 43% by using the FP-CLPHP having non-uniform channel design. Non-uniform channeled FP-CLPHP can successfully operate even at horizontal position meaning the lack of gravity support, and it maintains operation independent from variations in applied heat load except 10W. However, uniform-channeled FP-CLPHP does not operate with the lack of gravity support, or in other words, at horizontal orientation.