| The cascading pulse tube cooler(CPTC)is a new structure achieved by connecting pulse tube cooler(PTC)units in series through long tubes(namely transmission line in this study).This method not only inherits the superiority of conventional pulse tube cooler,no moving parts at cold end,but also makes up for the low efficiency of conventional pulse tube cooler.As a novel approach to achieve Carnot efficiency of refrigeration,the CPTC will be promisingly applied to areas where high cooling capacity(e.g.kilowatt refrigeration)and/or different temperatures refrigeration(e.g.space refrigerator with various cooling temperatures)is needed.Based on our previous work,the following studies focusing on heat exchangers(HXs)before and after the transmission line,in terms of reducing flow loss and heat transfer loss have been carried out.1.Theoretical basis for removing HX before the transmission line has been illustrated.Based on the linear thermoacoustic theory,a model for heat transfer loss analysis has been developed.Simulation results showed that the total acoustic power loss due to pressure drop and temperature difference in the HX before the first transmission line was twice more than that when the same HX was placed after the first transmission line.Similar results were obtained in the HXs before and after the second transmission line.Theoretical analysis suggested that the HXs before transmission lines were unnecessary.2.Simulation results mentioned above have been validated by experiments.Based on the existing three-stage CPTC,the total cooling capacity at 500 W input power and 55 Hz frequency is 273.2 W @ 233 K after the removal of the two HXs before the first and second transmission lines.Consequently,the cooling capacity increases by 23.6 W and the performance is improved by 9.46%compared with the original one.In conclusion,the theory is verified by the experiment that HXs before transmission lines are unnecessary components in the CPTC,herein it should be removed. |
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