In this paper, systematic experimental investigations were carried out for a wickless heat pipe with flat evaporator having dimensions (100x100x30) mm. Flat-square electrical element was used to simulate the heat source of electronic part with dimensions of (100x100) mm. The aim of this paper presents the effect of fill ratio and cooling water mass flow rate on thermal performance of a wickless heat pipe. Experiments were performed to evaluate performance of wickless heat pipe for range of input power from 10 W to 100 W. The fill ratios used in the present work were 15%, 25%50% and 85%. The cooling water mass flow rate was also changed from 0.0083 kg/s to 0.033 kg/s. Experimental results showed that the maximum value of wall evaporator temperature was 115°C at input power of 100 W and a fill ratio of 15%. Results also showed that the maximum value of the total resistance was 0.8°C/W.

This paper presents the effect of filling ratio on thermal performance;of a loop thermosyphon. The experimental setup consists of an evaporator, a condenser, a riser and a downcomer. The dimensions of the loop thermosyphon under consideration were chosen so that they are mostly suitable for use in the cooling of electronic components. Distilled water was used as a working fluid. Experiments were carried out to estimate the performance of the loop thermosyphon for a range of input power from 10 to 100 W. Four fill ratios were considered in the present work, namely; 15%, 25%, 50% and 85%. Results showed that the maximum value of wall temperature in evaporator was 95°C, at 100 W input power and 15% fill ratio. The fill ratio of 50% gave the minimum evaporator wall temperature which was 80°C. Increasing fill ratio tends to decrease the evaporator wall temperature for evaporator.