THE INTERFACIAL THERMODYNAMICS OF MICRO HEAT PIPES

Successful analysis and modeling of micro heat pipes requires a comple te understanding of the vapor-liquid interface. A thermodynamic model of the vapor-liquid interface in micro heat pipes has been formulated that includes axial pressure and temperature differences, changes in l ocal interfacial curvature, Marangoni effects, and the disjoining pres sure. Relationships were developed for the interfacial mass flux in an extended meniscus, the heat transfer rate in the intrinsic meniscus, the ''themocapillary'' heat-pipe limitation, as well as the nonevapora ting superheated liquid film thickness that exists between adjacent me nisci and occurs during liquid dry out in the evaporator. These relati onships can be used to define quantitative restrictions and/or require ments necessary for proper operation of micro heat pipes. They also pr ovide fundamental insight into the critical mechanisms required for pr oper heat pipe operation.