Thermal characteristics of a Hartmann-Sprenger tube

Abstract

This paper describes the thermal characteristics of a water-cooled Hartmann-Sprenger (HS) tube as an expansion device for refrigeration and cryogenic applications. In this arrangement, a jet issuing from a convergent nozzle and expanded to a pressure below the critical value is directed towards the HS tube closed at the opposite end and maintained at resonant conditions. The interaction of the steady jet entering this tube, the generation and the propagation of the acoustic waves within the tube and the resulting non-linear flow oscillations result in strong thermal effects and heating of the entrapped gases. Effective heat removal at the surface of the HS tube results in a pseudo-positive Joule-Thomson coefficient. The emerging gas from such a nozzle-HS tube arrangement under resonant conditions will be much cooler when compared to the throttling process. The intense heating experienced in this arrangement using primary and secondary smaller tubes may find other industrial applications such as the flameless ignition of rocket engines. This experimental work suggests further investigations coupled with analytical modelling and optimization resulting in a device having either maximum cooling of the emerging stream or a high temperature heat source.