Performance characteristics of variable conductance loop thermosyphon for energy-efficient building thermal control

Variable conductance loop thermosyphon (VCLT) manipulates natural phase-change cycle to regulate the heat transfer. Its primary advantages include high sustainability, simple design and low cost. One of the potential applications of variable conductance loop thermosyphon is thermal control in buildings for achieving high energy efficiency. In this study, a distributed steady-state model was implemented to determine the heat transfer control characteristics of variable conductance loop thermosyphon for the first time and evaluate its effectiveness on precise air-conditioning for buildings. The internal flow resistance rises from 0.002 K/W to 0.305 K/W and the heat transfer rate decreases from 468.5 W to 71.9 W when the relative opening degree of the regulating valve reduces from 1.00 to 0.17 under normal boundary conditions. The thermodynamic analyses show that the regulating valve of the variable conductance loop thermosyphon can enable effective thermal control over a wide range of heat transfer rate to accomplish indoor thermal comfort. The study also reveals that variable conductance loop thermosyphon can be effectively adopted with various working fluids and over wide ranges of heat source and heat sink temperatures.