Numerical Simulation Research On Start-up And Stable Operation Of Pulsating Heat Pipe

Pulsating heat pipe has been regarded as an effective heat transfer component to undertake the field of electronic components cooling due to its advantages of simple structure,good heat transfer performance,strong adaptability,etc.Until now,the gas-liquid two-phase flow and heat and mass transfer phenomenon has not yet been fully revealed in the working process of the pulsating heat pipe,considering gas-liquid two phase flow,heat and mass transfer,the interface motion and the change of two phase flow,a unsteady model of vapor-liquid two-phase flow,heat and mass transfer in PHP is developed and numerically analyzed.Numerical simulation the gas-liquid two-phase flow and heat mass transfer process of the different medium(water,ethanol and methanol)under different filling ratio(20%~80%)and heat inputs(10 W~60 W).Analyzed the change of initial flow pattern,taking into consideration of coupled condensation and evaporation phase change as well as evolutions of vapor-liquid two-phase flow patterns and stable circulation flow;According the temperature fluctuation curve to analysis the impact factors of pulsating heat pipe start-up time and heat resistance.The results indicate that: In the process of the pulsating heat pipe operation can form stable circulation flow in one direction;the start-up time of pulsating heat pipe gradually decreased with the heat inputs increased and decrease slower,the start-up time of Water first increased and then decreased with the filling ratio increased,the best filling ratio between 40% and 60%.The start time of water is the longest and methanol is the shortest in the same filling ratio and the heat inputs;the thermal resistance of water gradually decreased with the heat inputs increased under various filling ratio,the pulsating heat pipe have the maximum thermal resistance in the condition of 20% filling ratio and 10 W heat inputs,which have the minimum thermal resistance in the condition of 50% filling ratio and 60 W heat inputs.the thermal resistance of ethanol and methanol have the same trend with water.The research results can provide an effective theoretical support for the design of PHP in its practical applications,this paper designed two kinds of pulsating heat pipe application solutions according to the characteristics of pulsating heat pipe.