EFFECT OF CONDENSER LOCATION AND TUBING LENGTH ON THE PERFORMANCE OF A COMPACT TWO-PHASE THERMOSYPHON

摘要

This study investigates the issues involved in the design of compact two-phase thermosyphon systems for high power chip cooling. In such systems, the locations of the evaporator and condenser need to be given a high degree of freedom. The key components used in the experiment are: an evaporator enclosure (20 mm x 20 mm x 20 mm internal volume), a simulated chip (20 mm x 20 mm) with an enhancement structure (10 mm x 10 mm x 6.8 mm) and a cartridge heater embedded in a copper rod (11.9 mm x 11.9 mm cross-section). A dielectric coolant (PF-5060, boiling point 56 ℃ @ 1 atm) is used as the working fluid. Also included in the loop are a natural convection cooled condenser of dimensions 58 mm x 60 mm x 432 mm and connecting tubing. The relative height between the evaporator and the condenser, the tubing length, and the heat input were systematically varied. In this study, the heat flux ranged from 0 to 40 W/cm~2; the pressure within the system ranged from -68.9 kPa to +34.5 kPa; and the relative height of the condenser over the evaporator ranged from 15 cm to 45 cm. These ranges represent actual conditions for electronics applications. Experimental studies show that these parameters affect the evaporator thermal resistance from the chip to the boiling pool, and the overall thermal resistance from the chip to the ambient air in a complex way. However, close examination of the data suggests that there could be an optimum point in the parametric domain.