Adsorption-based antifreeze system for loop heat pipes

The use of water in loop heat pipes (LHP) is known to be desirable: water is almost freely available; it exhibits high thermal performance and is non-toxic. Nevertheless, water has a major drawback which is its anomalous expansion when cooled down to a negative temperature. This is likely to damage the capillary wick of the LHP. To overcome this problem, a storage tank may be coupled to the loop heat pipe. It contains a strong adsorption capacity material designed to adsorb the fluid during shutdown phases of the system and to desorb it during the startup phases. A storage tank using the RD-type silica gel as adsorbent material was designed. It is a passive system, which does not require mechanical elements to circulate the fluid and does not degrade the thermal performance of the device. However, a secondary auxiliary heating system is required to desorb the fluid. Furthermore, it may be located away from the heat source and it is compact. The simulation results show that the storage tank volume is acceptable and requires moderate energy to desorb the fluid.