Wetting hysteresis as the mechanism of heat pipe post-dryout thermal hysteresis and recovery

Heat pipes and vapor chambers are passive thermal management devices used for efficient heat transport by phase change. Their operation is enabled capillary pumping of the working fluid in a porous wick, which operationally limited maximum pressure head it can provide. This limit marks input at generated overcome drop wick; operating above steady state leads to dryout. increasingly being electronics systems where end-user activity dictates transient power therefore be highly variable time-dependent. It was recently shown that withstand pulse exceeding brief time intervals. Under such conditions, pipe will experience dryout only if duration load longer than certain characteristic interval. The pulse-load-induced may result an increased resistance when reduced back down pre-dryout levels, thus exhibiting hysteresis performance. In this work, we experimentally characterize recovery from pulsed-load-induced We further propose observed change steady-state performance before after results contact angle three-phase line wick-liquid interface. A model developed based on proposed mechanism predict nature dryout-induced hysteresis, as well identify given has possible hysteresis. experiments illustrate trends inferred process confirm existence “maximum line,” identifies worst-case scenario Based these mechanistic learnings, new testing protocol characterizing post-dryout signature pipe.