Experimental investigation of the effects of filling ratio and inclination angle on the thermal performance of inner groove oscillating heat pipe

In this study, the thermal performance of inner groove oscillating heat pipes (IGOHP) with deionized water as a working fluid has been experimentally investigated. The results showed that in the filling ratio, 60% of the IGOHP has the lowest thermal resistance and the highest thermal conductivity. Then at the best filling ratio (60%) the IGOHP was investigated at different heating powers and also at different inclination angles. The achieved results indicated that in heating power of less than about 75 watts in 70° and 90°, thermal resistance is higher than angles of 5°, 15° and 30°, and among them, the angle of 15° had the lowest thermal resistance, but in heating power of more than 100 watts The performance of the IGOHP at 90° was better than the other angles, Also, the start-up of the IGOHP at an inclination angle of 15° occurred earlier than the vertical position. In this research more remarkable result is that at heating power above 200 watts, the thermal resistance of the IGOHP at an angle 15° is approximately equal to the angle of 90°, which in turn is a point for the IGOHP, which can promise to solve the problem of oscillating heat pipes at angles close to the horizon.