Heat-pipe-based tunable multimode horizontal thermal rectifier

A heat-pipe-based multimode thermal rectifier, easily scalable for advanced thermal energy management in industrial applications (e.g., waste heat recovery, solar energy application and building energy management), is proposed for horizontal heat transport. The thermal rectifier is composed of a copper tube loop having a superhydrophilic section and a superhydrophobic section. The thermal rectification effect is achieved by the differences of the superhydrophilic and superhydrophobic sections in surface evaporation/condensation and wicking characteristics, when they are exposed to heating or cooling. Meanwhile, a valve is incorporated in the vapor channel to control the switch status of the hot vapor flow. Experiments with such a thermal rectifier showed that a maximum thermal rectification ratio of 4.18 could be reached at the heat flux of 3222 W/m², whereas a higher rectification ratio (up to 5.78) could even be achieved when forward and reversed heat transfer are at different heating temperatures in real applications. Besides, the forward thermal conductivity could reach 623 W/(m⋅K) for efficient waste heat harvest. In addition, the thermal rectification ratio, as well as the heating mode, can be tuned by the status of the valve in the tube loop to satisfy the complex requirement in practical applications.