Estimation of swirl velocity of gas in Ranque-Hilsch vortex tube using a combined thermal and species separation model

Abstract

ABSTRACT A Ranque-Hilsch Vortex Tube (RHVT) is a device that can cause simultaneous thermal and species separation in a compressible fluid mixture. The binary mixture is compressed and tangentially introduced into the vortex chamber of the RHVT, and two streams are withdrawn at opposite ends of the device. The RHVT acts as a centrifugal separator that separates the mixture into two streams, one enriched and the other depleted of the component with higher molecular weight. The extent of separation depends on the magnitude of swirl velocity of gas mixture inside the RHVT. Now a new combined heat and mass transfer model using heat and mass transfer analogy has been proposed by the authors to predict the species separation in a RHVT. The aim of this paper is to use this model to estimate the magnitude of swirl velocity of gas mixture inside the RHVT. The estimated values have been compared with range of experimentally as well as numerically obtained values reported in the literature. For a given configuration in published literature and values of cold mass fraction the average swirl velocity inside the RHVT was found to vary between 90 m/s and 130 m/s. It is found that for a fixed value of inlet pressure, average swirl velocity is a function of cold mass fraction. The value of average swirl velocity minimizes near cold mass fraction = 0.3 and maximizes near cold mass fraction = 0.8. Parametric studies have been carried out to understand the effect of important RHVT parameters on swirl velocity. Also relation between swirl velocity and species separation has been explored.