PURPOSE: To enlarge a working temperature range of the titled device, by using an alcoholic aqueous solution as the working medium of heat pipe, in a heat pipe type vacuum glass tube-shaped solar energy collector.
CONSTITUTION: An aqueous solution B of 85wt% of propylene glycol or an aqueous solution C of 70wt% of ethanol is used as a working medium to be filled into a heat pipe. Because the aqueous solution B has a high boiling point, i.e., about 150°C under an atmospheric pressure, the solution B is filled into the heat pipe after the reduction of its pressure to lower than 0.1kg/cm2. The aqueous solution C of ethanol is used only after the reduction of its pressure to lower than 0.1kg/cm2. The freezing point of propylene glycol aqueous solution B is about -40°C at the concentration of 85wt%. Similary, the ethanol aqueous solution has the freezing point of about -50°C at a 70wt% concentration. In this manner, the alcoholic aqueous solution can lower a freezing temperature range, prevent the decomposition and metamorphosis at elevated temperature, and thereby allowing an application in an extended temperature range from -40°C to 200°C.
AZUMA IZUMI
TSUJI SADAO
FUJI ELECTRIC CO LTD