Study On Condensation And Evaporation In Pressure Oscillation Refrigeration

Gas wave refrigeration technology is an unsteady refrigeration technology by using wave motion in the pressure oscillation tube to realize energy transferring and the separation of heat and cooling capacity.It is often used in removing water and hydrocarbon in natural gas,the deep refrigeration and other occasions.When high pressure intaking gas contains condensable component,condensation and evaporation occur.These two phenomenons will afffect the flow field in pressure oscillation tube and influence the refrigeration efficiency of the machine.Researching on the liquidation performance,analyzing the droplet size and liquefaction ratio has guiding significance to gas-droplet separation.Therefore,combining the method of numerical simulation and experiment,we study the the condensation and evaporation process of condensable components in pressure oscillation tube.The gas wave refrigerator with static pressure oscillation tubes is built.The pressure fluctuation and the impact of condensation and evaporation on the efficiency of the refrigerator are verified.The conclusions are drawn as follows:?1?UDF has been used to describe the condensation and evaporation process.It can be found that due to the small sizes of droplet particles,droplets in pressure oscillation tubes have good following character.Particle slip effect on the distribution of liquid parameters is limited.Fluctuations of the flow field in pressure oscillation tube will lead to condensation,producing four obvious particle density peaks.Fluctuations of the flow field will also cause evaporation of the droplet.Before low temperature exhausting,mass of evaporation accounts for 24.11%of the total quality of condensation liquid.The mass of evaporation which is caused by mixing of hot and cold gas gas accounts for 86.3%of the total loss.?2?Numerical simulation has been used to study the influence of three key operating parameters on liquidation performance.With the increasing of air humidity of inlet gas,the number of particles in pressure oscillation tube increases first and then decreases before low temperature exhausting.Particle radius showes a trend of increasing,in fully liquefied area,the value of maximum peak of particle radius is 4 times of the minimum peak.When relative humidity is constant,with the decreasing of inlet temperature,liquefaction rate and particle density increases before low temperature exhausting,but particle radius decreases.When the moisture content is constant,with the reducing of the inlet temperature,the liquefaction rate increase,and in fully liquefied area,the biggest particle radius increases first and then decreases.When the relative humidity or moisture content of high pressure inlet is constant,with the increasing of compression ratio,particle density and liquefaction rate will increase,and particle radius will decrease.Although when?=2.0,the radius is bigger,but liquefied rate is very low,if y is constant,liquid total quality of which is only about one in ten thousand of?=5.0.?3?The condensation and evaporation models have been used to study the secondary evaporation caused by the reverse compression wave and the reverse shock wave.When the shock wave reaches the right end of the pressure oscillation tube,if the high temperature outlet is semi-open and semi-closed,the secondary evaporation effect caused by the reverse wave system is minimal,and the total number of particles in the tube is 5 and 3 orders of magnitude larger than when it is fully open and closed,respectively.The peak of the particle radius in the tube is 3.6 times and 2.1 times when it is fully open and closed,respectively.The wave attenuator can reduce the temperature of the low-temperature gas,and eliminate the high temperate zone,improving the refrigeration efficiency.It will reduce the particle concentration and increase the particle radius at the same time.?4?SRK equation defined by UDF is used to study the dehydrocarbon process of gas wave machine.Due to the large Gibbs free energy barrier that octane condensation needs to cross,the effect of homogenization condensation and liquefaction is not ideal.When considering the heterogeneous condensation of octane in the gas wave refrigerator,it was found that the greater the concentration of the intake condensation core,although the liquefaction rate increased,the particle radius decreased.After the concentration reached10¹⁷/kg,the increasing of the concentration liquefaction rate was not significant.?5?It can be observed from the experiment that pressure fluctuation of a point in a pressure oscillation tube is periodically oscillating and attenuating,which is in good agreement with the numerical simulation results.Condensation process will strengthen the shock wave and weaken the expansion wave.With the increase of the intake humidity,the temperature of the low-temperature gas rises and the isoentropic efficiency decreases.The smaller the pressure ratio,the greater the effect of condensation and evaporation on the refrigeration performance of the gas wave refrigerator.