Investigation On Performance Of Miniature Steam Ejector Refrigeration System Driven By Capillary Force

The concept of "e-Navigation" and the blueprint of "Made in China 2025" accelerate the progress of the research of intelligent ships.With the development of intelligent ship,the heat flux of electronic chips in intelligent ship systems increases continuously.High heat flux,which reduces the reliability of the electronic chips,threats the intelligent systems seriously.Therefore,the heat generated by electronic chips of intelligent systems need to be dissipated effectively.A miniature ejector refrigeration system driven by capillary force which can provide active heat dissipation of electronic chips was studied in this paper.Porous wick and miniature ejector are the key components of the system.For key components,the main research tasks are represented below:Firstly,sintered nickel porous wicks were fabricated.Also,microstructure,physical parameters and the thermal performance of wicks were tested.This paper investigated the effects of pressing pressure,sintering temperature and powder diameter on the performance of porous wicks.It can be found that with the increase of pressing pressure and the sintering temperature,and the decrease of the average particle size of metal powder,permeability decreases and temperature of compensation chamber increases.Furthermore,the Ni porous wicks,which show the best comprehensive performance,can be fabricated by loose powder sintering process with 4.5pm nickel powder and sintering at 650 ℃.The temperature difference between the evaporation zone and the compensation chamber is 11 ℃approximately.Secondly,a one-dimensional constant pressure mixing model was used to design the miniature ejector and a CFD method was utilized to optimize the structure of the miniature ejector.Numerical simulation results show that optimal values of area ratio of constant-area mixing section to nozzle throat,constant-area mixing section length and nozzle exit position are 12.25,30mm and 8mm respectively.Finally,an experiment system was set up to investigate the influence of working conditions and structural parameters on the performance of the miniature ejector.Experimental research revealed that the miniature ejector using water as working fluid works well when Tg=55 ℃ to 70 ℃ and Pe=1300Pa to 2100Pa,the maximum COP is 0.66,the maximum critical back pressure is 2550Pa and the maximum cooling capacity is 119W.With the increase of NXP,the COP firstly drops rapidly and then decreases slowly,the critical back pressure of the miniature ejector increases initially and then decreases.As area ratio of constant-area mixing section to nozzle throat increases,COP increases and the critical back pressure of the miniature ejector decreases.