Processes, models and the influencing factors for enhanced boiling heat transfer in porous structures

Abstract

In order to understand the effect of porous structures on boiling heat transfer, this review investigates and evaluates the preparation methods, critical heat fluxes and heat transfer coefficients of porous structures in the field of pool boiling heat transfer over the last decade. The types of porous structures formed can be divided into particle stacking structures and monolithic hollow structures. Typical particle stacking structures are sintered particle structures, or dendritic porous structures formed by electrodeposition, which have an abundance of nucleation sites. Monolithic hollow structures are represented by metal foams, which have a relatively large volume of pores. Furthermore, there are many factors that influence the heat transfer effectiveness of these porous structures, such as nucleation sites, pore space, thickness, and others. Nanoscale porous structures also have some unusual heat transfer phenomena during boiling, such as weakening of initial heat transfer, wall temperature reduction at high heat fluxes, and boiling hysteresis. In this paper, the above anomalies are explained. However, several important challenges related to porous structures need to be addressed. For example, how to maximize the advantages of pore characteristics and to propose accurate models for predicting heat flux. Nevertheless, this paper presents some suggestions to develop micro-nano composite structures for optimizing the heat dissipation effect of the structure and to develop predictive models using pore characteristics as parameters. The development of porous structures responds to the needs of thermal management policies, helps to solve heat dissipation problems and can play a key role in sustainable development.