The coupled effects of working fluid and solid wall on thermal performance of micro heat pipes

By incorporating the solid wall conduction, together with the continuity, momentum, and energy equations of the liquid and vapor phases, a mathematical model is developed based on the conservation laws and is solved to yield the heat and fluid flow characteristics of micro heat pipes. This work provides a comprehensive and insightful analysis on the effects of working fluid and solid wall on the thermal performance of micro heat pipes. The characteristics and performance of different types of working fluid and solid wall are elucidated. A well-defined exposition of the circulation effectiveness of the working fluid is proposed and the operation regime map for different types of working fluid is conceived for the identification of the optimal operating conditions. The coupled role of working fluid and solid wall is quantified by deriving a new non-dimensional group, which can be used to characterize the contribution of working fluid and the solid wall to the heat transport rate. The present study serves as a useful analytical tool in the micro heat pipe design and performance analysis, associated with the selection of both working fluid and solid wall material for specific operating conditions.