Experimental Study On The Start-up And Heat Transfer Limit Of Oscillating Heat Pipe

In this paper, combined with the existing research results, the start-up and heat transfer limit property of Oscillating Heat Pipe (OHP) was studied on the basis of experimental data processing and analysis in multi-operating conditions.In terms of the start-up, the concept of the true start point and the false one were presented in this paper, the true one was a symbol of authentic stable operation, three different types of start-up like as the temperature mutant, the temperature gradient and the temperature smooth transition could be concluded. The study found that, heating power could affect the types of start-up, When the power was low, the temperature mutant was common, and the temperature gradient was based on middle power, while in the case of higher power, the temperature smooth transition was easily occurred; There was an optimal angle, the starting time was the shortest at the angle position, and the optimal one was 45°in this experiment; With the increased of filling rate, the minimum starting power became larger, but the rate of increase was low; OHP with acetone was easier to start.In terms of the heat transfer limit, two types of limitation like as the whole drying and the local drying were exhibited in this paper. Two different limit phenomena were occurred in the whole drying:①The temperature of the heating section increased sharply and persistently, while the temperature of the adiabatic and cooling sections was fluctuated slowly;②The temperature of the heating section rose up suddenly, but it fluctuated soon, the frequency was reduced and the amplitude was increased. Two different limit phenomena were also occurred in the local drying:①One pipe's temperature was increased sharply, while adjacent one was fluctuated substantially;②The pipe's temperature was fluctuated alternately and substantially between adjacent ones, so the position of limit was shifted constantly. The study found that, with the increased of angle and filling rate, the heat transfer limit increased; and the limitation of OHP with water was lower than that with acetone on horizontal, while on the other angle, the former was higher than the latter.OHP could self-repair when heat transfer was deteriorated, and the operating temperature continued to rise with the increased heating power during the operation.This study would contribute to not only the rapid and steady start-up but also the safe and effective operating; moreover, it could lay foundations for the fundamental investigation of OHP.