| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1989: ¥100,000 (Direct Cost: ¥100,000)
Fiscal Year 1988: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1987: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
An investigation of flow and heat transfer characteristics in two-phase loop thermosyphons was performed both experimentally and theoretically. There are three types of the loop thermosyphon; open, closed, and double tube. Heat transfer coefficients in an evaporator and a condenser, and circulation flow rates were measured experimentally using water, ethanol, and Freon 113 as the working liquids. The heat transfer coefficients in the evaporator and the condenser were correlated by the expressions for pool boiling and film condensation respectively. As a result, the heat transfer coefficients in the evaporator were well correlated by the Stephan-Abdelsalam equations, and heat transfer coefficients in the condenser were smaller than the film condensation expression when liquid fill charge was large. This is because the liquid lifted up to the condenser by bubble pumping action makes a liquid pool at the bottom of the horizontal condenser pipe, so that the condensing area becomes small. The circulation flow rates were theoretically predicted by calculating pressure, temperature, quality and void fraction along the loop. And, the comparatively good agreement between the predicted and experimental circulation flow rates was shown.
The theoretical calculation method was applied to a double tube thermosyphon, and the feasibility of its application to the extraction of geothermal energy was examined. In addition, the heat transfer coefficients and the critical heat fluxes in the double tube thermosyphon were also investigated. And, the effect of the inlet geometry of inner tubes on the heat transfer characteristics was clarified.
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