In the present paper

the reflected shock wave absorbing effect and its influence on the performance of thermal separator are investigated by means of a single-tube set-up.In the experiments

the shock wave absorber is a short tube whose relative diameter D/d is 5.7 and relative length l/d is 9.0

the relative length of the oscillatory L/d is from 107 to 730. The expansion ratio is from 2.0 to 6.0 and the exciting frequency is from 30 to 200 Hz. The experimental results show that the reflected shock wave is eliminated effectively as L/d＜400 while the absorber is mounted at the closed end of the tube

but when L/d＞400

it makes no difference to mount the absorber anywhere because the energy of the reflected shock wave is exhausted by the viscosity and friction of the gas inside the tube. Absorbing the reflected shock wave has great effect on the performance of thermal separator

e.g. the refrigeration efficiency is increased significantly

the optimal exciting frequency is decreased

the tube length can be shortened

the varying operating mode of the thermal separator can be improved

etc. When the tube is relatively short

the refrigeration efficiency is increased with the tube length

but when the tube length is increased to some value

the result is just the contrary. The recommended optimal tube length L/d is 200—350 for the tube without absorber and 150—250 for the tube with absorber. There exists a number of peak values of refrigeration efficiency when the exciting frequency is increased and the optimal exciting frequency is equal to the first

the second

and the third peak oscillatory frequency respectively when the tube length is L/d≤267， 267＜L/d≤502

L/d＞502. An optimal parameter matching relationship

which can be used to predict the value of the optimal exciting frequency

is derived in this paper.