In important facilities related to lifeline such as energy supply equipment, information and telecommunication equipment, and traffic facilities, many electronic apparatuses have been used in recent years. These electronic apparatuses need to be stably and surely operated, and heat generated by an electronic apparatus is required to be radiated. As heat radiation means, there are a wide variety of modes; and there is a cooling apparatus (for example, see Patent Document 1.) as one of the heat radiation means having high reliability suited to high efficiency, energy saving, and environmental conservation. The cooling apparatus is configured such that a heat exchange circulating solution is circulated in the apparatus by using a density difference (buoyancy caused by density difference) in a circulating solution transport pipe, caused by phase change of the heat exchange circulating solution. That is, the heat exchange circulating solution is made to circulate by using the density difference between an apparent density of a gas-liquid two-phase fluid in a gas-liquid two-phase fluid inlet pipe between a heating heat exchanger and a two-phase fluid inlet and a density of the heat exchange circulating solution in the circulating solution transport pipe in the same longitudinal length as that between the heating heat exchanger and the two-phase fluid inlet. Furthermore, by repeating this circulation, high-temperature heat transferred from the heating heat exchanger is transported to a sensible-heat-emitting heat exchanger and a heat radiator, and the heat is transported to other apparatus or a low heat source which requires the heat from the sensible-heat-emitting heat exchanger and the heat radiator.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2005-195226 (pp. 4 to 6, FIG. 1)