INFLUENCE OF CHANNEL DIAMETER ON BOILING HEAT TRANSFER IN A CLOSED ADVANCED TWO-PHASE THERMOSYPHON LOOP

摘要

As heat generation from electronic components increase and the limit of air-cooling is reached, the interest for using liquid cooling for high heat flux applications has risen. Thermosyphon cooling is an alternative liquid cooling technique, in which heat is transferred as heat of vaporization from evaporator to condenser with a relatively small temperature difference. The effect of fluid properties, the structure of wall surfaces, and the effect of system pressure were investigated and reported previously by the authors. In this paper, experiments on an advanced thermosyphon loop consisting of an evaporator, a condenser and connecting tubing are presented. The influence of the diameter of the evaporator channels on the heat transfer coefficients is reported. The tested evaporators were made from small blocks of copper in which 7, 5, 4, 3, 2, 1 vertical channels with the diameters of 1.1, 1.5, 1.9, 2.5, 3.5 and 6 mm respectively and the length of 15 mm were drilled. Tests were done with Isobutane at heat fluxes ranging between 22.4-303 kW/m~2. Experimental results in terms of heat transfer coefficients at different tubing length between evaporator and condenser are presented.