Typhaine Coquard | Searcharxiv

arXiv2026

Studies of PHP with CASCO code and its experimental validation

We discuss here two major issues related to the steady functioning of the pulsating (oscillating) heat pipe (PHP): the effect of the surface properties and stopovers. They are studied with the CASCO simulation software (Code Avanc{é} de Simulation du Caloduc Oscillant: Advanced PHP Simulation Code in French) version 4. Its experimental validation against two different prototypes is presented. The first is used also to study the effect of the nucleation barrier (the wall superheating necessary for the bubble nucleation) that reflects the wall wettability and roughness. An optimal value of the nucleation barrier is found where the thermal resistance achieves a minimum for a given evaporator power. The functioning regime is continuous showing pressure waves propagating along all the PHP channel. The stopover regime is observed both for small and large barriers. The second experimental setup (PHP Smart Loop) is used to study the stopover regime. It is found that it is characterized by a chaotically repeating sequence of fast pressure growth (corresponding to oscillations) followed by a slower pressure decay during a stopover. The decrease of the thermal resistance with heating load is explained by a decrease of the stopover time caused by a faster liquid film shrinking.

physics.flu-dyn↗

arXiv2023

Heat and Mass Transfer in the Porous Wick of a Capillary Evaporator

Heat and mass transfer inside the porous wick of a capillary evaporator is studied using a mixed pore-network model. The impact of the thermal conductivity of the wick on the overheating limit (defined as the difference between the maximum temperature at the top of the metallic casing and the saturated temperature), breakthrough (which occurs when the vapor reaches the wick inlet) and the parasitic heat flux lost by conduction at the entrance of the wick (which decreases the efficiency of the evaporator) is investigated. The study suggests a bilayer wick as a possible better design to optimize the performance of the evaporator. With this design, the inlet layer is of low thermal conductivity with small pore size so as to reduce the parasitic heat flux. The inlet layer also plays a role of capillary lock limiting the risk of breakthrough. The second layer, right under the metallic casing, is more conductive with a high thermal conductivity and larger pores so as to limit the risk of overheating. It is shown that this design increases the range of heat loads which can be applied to the evaporator.

physics.flu-dyn↗