Experimental Investigation Of Ultrasonic Effect On The Oscillating Heat Pipe

The Oscillating Heat Pipe (OHP) is widely used in many fields due to its high heat transfer capacity, therefore, the research on the mechanism of the flowing of the working fluid in the OHP and its heat transfer capacity has important theoretical significance and application value. With the rapid development of science and technology, the devices are gradually miniaturized while the heat load is greatly increased, which leads to the increasingly high demand on the enhancement techniques of heat transfer. At present, many researches on the enhancement of the heat transfer capacity of the OHP have been conducted by research institutions and scholars from both the domestic and foreign countries, while the investigations were mainly focused on the passive heat transfer enhancement, however, the research on the active heat transfer enhancement was relatively less. In this paper, based on the basis of the acoustics and heat transfer, the experimental investigation was developed to study the active heat transfer enhancement of the OHP under the ultrasonic effect.First of all, the experimental investigation on the heat transfer performance of the acetone-copper OHP was achieved and the results are as follows:with the increasing of the heat load, the thermal resistance of the OHP becomes lower; the Gravity facilitates the operation of the OHP, so the heat transfer performance of OHP is best when the OHP is placed vertically with the evaporating section at the bottom; at the same filling ratio, with the increasing of the water bath temperature, the thermal resistance of the OHP becomes lower; at lower filling ratio, there are more vapor plugs than liquid slugs which can provide enough driving force and decrease the flowing frictional resistance, so that the oscillating heat transfer is improved and the thermal resistance is reduced; when the heating power is less than30W, the thermal resistance of the acetone-copper OHP is lower than that of the water-copper OHP, however, when the heating power is larger than30W, the thermal resistance of acetone-copper OHP is higher than that of the water-copper OHP.Secondly, the comparison experiments of the acetone-copper OHP with and without the ultrasonic effect were accomplished. Ultrasonic effect on the heat transfer capacity enhancement of the OHP under different heating load, filling ratio, water bath temperature, inclination angle, and working fluids were investigated. The results indicate: when the filling ratio is higher, the heat transfer enhanced by the ultrasonic effection the OHP is stronger; when the water bath temperature is increased from20°to40°, the heat transfer enhancement due to the ultrasonic effect becomes bigger gradually, however, when the water bath temperature is increased from40°to60°, the enhancement becomes smaller gradually; when the heating power is less than50W, the ultrasonic effect has a significant enhancement on the heat transfer capacity of the OHP, while, when heating power is greater than50W, there is almost no enhancement due to the ultrasonic effect; when the inclination increased from0°to90°, the heat transfer enhancement under ultrasonic effect is gradually improved.Finally, in order to investigate the working fluids effect, the same OHP was charged with water and the comparison experiment was conducted under the effect of the ultrasound. The results show that the physical property of the working fluid do affect the heat transfer enhancement due to the ultrasonic effect.