A Thermosyphon Device for Passive Cooling

Heat pipes are devices used to transfer heat from one place to another based on two-phase heat transfer. A Thermosyphon is a special heat pipe where the working fluid is returned back to the evaporator by gravity, not needing a wick for this purpose. Such a device is simple, has no moving parts and consumes no power. The goal of the work was to investigate the feasibility of the thermosyphon principle applied to passive cooling of buildings. Several laboratory-scale cooling devices were built and tested. The devices consisted of an evaporator, a vertical pipe section and a condenser. The evaporator was wicked to enhance fluid distribution along the evaporator-pipe section. The condenser was a spiral fin heat exchanger. Water was used as working fluid. During the measurements the evaporator was in a chamber where heat to the evaporator was transferred by natural convection. The chamber was heated up with electricity to create a sufficient temperature difference. The condenser was outside the chamber few metres above the evaporator. Some tests indicated instability in the two-phase heat transfer process. The stability was depending on the construction of the evaporator. In general, the cooling power of the device turned out to be at a satisfactory level from the viewpoint of the application.