Abstract
There are many types of thermosiphon, which can realize heat transfer without any external electric power. In this study, a top-heat-type thermosiphon utilizing vapor bubble pumping is focused on for the simple structure. Its application has some problems, although it has been extensively studied. One of these problems is the unstable heat transfer, that is, intermittent circulation flow rate of the working fluid. This occurs under the conditions of less solar radiation during the morning and evening, and has been investigated by conducting a field experiment using a model house. For overcoming this problem, it is necessary to clarify the driving mechanism of the working fluid caused by the buoyancy of vapor bubble. To investigate the pumping characteristics, the vapor bubble volume is estimated measuring the water level in the buffer chamber by a capacitance type sensor. The experimental results shows that the water level increases with the increasing input current of the heater, the flow rate of the working fluid increases with the increasing water level, therefore the flow rate increases with the increasing input current of the heater under the same pressure condition of the buffer chamber. Then, it is clarified that the buoyancy force of the vapor bubble drives the working fluid.
