Research On Startup And Operating Characteristics Of Pulsating Heat Pipe With Different Heating Methods

Pulsating heat pipe (PHP), as a new style heat pipe, has some advantages of simpleconstruction, excellent heat transfer performance and low cost of making. There iscomplex vapor-liquid flow and heat transfer phenomena inside the pipe, the pressureunbalance is the cause of the working fluid pulse. Filling ratio, inclination angle andpipe diameter et al could influence the startup process, flow of working fluid and heattransfer performance.On the basis of the existing study, this paper researched different heat methods whichare differ from uniform heating method，and then combined those heating methods tostudy the effect on the startup process and stable operating of PHP. The results can beused as the reference in optimization design of PHP.In the present study, a two-dimensional model of PHP has been established which hasten turns. The working fluid is water, pipe diameter is2mm, took the influence ofgravity into consider and the direction is straight vertically. Use the volume of fluid(VOF) model and C language programming technology to simulate the phase changein the PHP.At the same heating method, increase the heat input cloud shorten the startup processand reduce the thermal resistance of PHP. Increase the heat input will also lead tomore intense fluctuation of temperature in the evaporator. When comes to the one turnheating method, if the heat input is too large, the PHP cloud not startup and the heattransfer will be destroyed. In this condition, we should choose the PHP which has alarger filling ratio. Heating the middle turns could shorten the startup process andthermal resistance, but this influence will get week when heating more and more turns.When the heating turns are less, the higher the filling ratio, the larger the startupprocess, but the results will be opposite if the heating turns are larger. No matter theheating method is, the thermal resistance is smaller at filling ratio of50%, and thePHP had the best performance at the filling ratio of50%. The PHP had a betteradaptability to the variation of heating input at a high filling ratio, so from the point ofstable heat transfer, the PHP should choose higher filling ratio in high heat input.Heating less turns cloud shorten the startup process and heating larger turns cloud geta better heat transfer ability, and then the combined heating method cloud play these two advantages. In order to quantitative control, we should focus on the type ofconversion and time of conversion.