Experimental investigation on the thermal resistance of straight heat pipes with double-ended cooling and middle-heating at different tilt angles

Heat pipes are one of the most attractive instruments for heat transfer processes. With the development of technology and reducing the dimensions of heat generating equipments, it is essential to provide solutions and innovations to increase the thermal performance of heat pipes. Thus, an experimental study has been investigated on straight heat pipes with double-ended cooling and middle heating. At first, heat pipes fabricated with sintered copper felt wick. Then, two cooling blocks installed on both end of heat pipes and a coil heater placed in the middle as the condenser and evaporator sections respectively. The experiments were conducted at inclinations 0° to 90° for heat inputs 20 to 80 W. The effects of heat input variation, cooling water flow rate and tilt angle on the thermal performance of heat pipes were studied. The obtained results for new structure of heat pipes compared with the conventional heat pipes which had one evaporator and one condenser. The results showed that by using the new cooling approach, the thermal resistance of heat pipes can be reduced significantly. Also, in low heat inputs, increasing the cooling water flow rate increases the thermal performance of heat pipes. The experimental results indicated that the tilt angle has a significant effect on the thermal performance of heat pipes. The minimum thermal resistance and the maximum effective thermal conductivity coefficient values are 0.2533 °C/W and 14072.65 W/m °C respectively, and they were observed at the tilt angle equal to 60° and for heat input of 60 W.