Dry-out characteristics of flat-plate pulsating heat pipe for proton exchange membrane fuel cell cooling

Abstract When flat-plate pulsating heat pipe is integrated for the cooling of proton exchange membrane fuel cell (PEMFC), excessively high temperatures at the evaporator section and insufficient liquid working fluid reflux can induce localized dry-out in partial channels. Aiming at the operating temperature range of the PEMFC, the dry-out characteristic of the flat-plate pulsating heat pipe was investigated. The results reveal that the flat‑plate CLPHP exhibits no thermal runaway with increasing heating power at the initial stage of dry-out. Under this condition, the maximum temperature difference of the PEMFC is only 3.77 ℃ with a temperature variance of 8.30 ℃2, indicating a favorable temperature uniformity. As the dry-out degree intensifies, the proportion of liquid working fluid in the evaporator section decreases, the liquid slugs and thick liquid film gradually vanish, and the flow pattern transitions from slug flow to semi-annular flow and annular flow, which degrades heat transfer efficiency.