PERFORMANCE OF WATER FILLED THERMOSYPHONS BETWEEN 30-150OC

The thermal performances of three water-filled thermosyphons subjected to evaporator wall temperatures between 30-150 o C were investigated. The effect of condenser cooling rates together with various fill ratios from 0.25-1.00, thermosyphon inclination angles from 23 o -90 o and aspect ratios from 5.0-10.0 were investigated. Power inputs from 5-405 W resulted in evaporator wall temperatures up to 185 o C. Water coolant flow rates from 0.003-0.05 kg/s were employed. Axial temperature distribution was found to be uniform at power input < 18 W and non-uniform at high power input. Evaporator wall temperatures based on bulk and mean values show differences of at least 14 o C at the high power values. The performance of the thermosyphons based on heat transferred varied linearly with mean or bulk temperature difference and was dependent upon fill ratio and inclination. The best performing thermosyphon was found to be at a fill ratio of 1.00 in the vertical position. Also, a high length/diameter aspect ratio thermosyphon performed better than one with a low aspect ratio.