两种管外传热型式对振荡管性能的影响

对管外换热状况对振荡管性能的影响进行了实验研究及理论分析 .实验中采用自然对流及强制对流 (轴向水冷却 )两种典型的管外换热型式 .结果表明 :改善振荡管外的传热状况 ,可使振荡管的冷效应显著增强 ,在膨胀比ε=2 0～ 6 0的范围内可使制冷效率提高 4 6%～ 5 4% ,同时可使最佳射流激励频率 fopt降低且膨胀比对fopt值不再有明显影响 对导致上述结果的内在机制进行了探讨

OF HEAT TRANSFER CONDITIONS ON PERFORMANCE OF OSCILLATORY TUBE

The oscillatory tube respresents a simple arrangement for gas cooling by its decompression,and has many applications in chemical processes and energy transformation. The mechanism of the cooling effect of oscillatory tube is the conversion of the pressure energy of gas to heat through the movement of pressure waves,which are moving shock wave and unsteady expansion wave. The radial heat transfer through the tube wall will influence the performance of the oscillatory tube significantly. In the present paper, the effects of heat transfer conditions outside of an oscillatory tube on the performance of the tube are investigated experimentally. In the experiments,two kinds of typical heat transfer conditions,natural convection and forced convection(axially water cooled),are studied. The oscillatory tube is a red copper tube,14 mm in diameter and 4 2 m in length. The pressure ratio is in the range of 2 0—6 0. The ambient temperature is 15 ℃. The inlet temperature of the cooling water is 17 7 ℃ at a flow rate of 0 81 kg·s -1 . The experimental results show that the refrigerating efficiency of the tube is increased by 4 6%—5 4% when the heat transfer condition outside the tube wall is improved by axial water cooling. Also,the optimum pulsing frequency ( f opt ) of the driving jet flow is reduced significantly and the value of f opt is no longer affected greatly by the pressure ratio when the heat transfer outside of the tube is intensified. The theoretical analyses of the experimental results are also presented.