Computational investigation of different effects on the performance of the RanqueeHilsch vortex tube Hamdy A. Kandil a, 1 , Seif T. Abdelghany b, * a Mechanical Engineering Department, Faculty of Engineering, Alexandria University, Egypt b Mechatronics Engineering Department, German University in Cairo, Egypt article info Article history: Received 9 October 2014 Received in revised form 30 January 2015 Accepted 24 February 2015 Available online 23 March 2015 Keywords: RHVT (RanqueeHilsch vortex tube) Cold orifice Maxwell's Demon Refrigeration CFDcomputational fluid dynamics () ANSYS fluent abstract The RanqueeHilsch vortex tube is a simple device with no moving parts and no mechanical operations. This device separates the inlet air into two distinctive regions; an outward high temperature region and an inner low temperature one. A computational study of the tube is presented in this article using an axisymmetric model using the ANSYS Fluent ® software whose results showed good agreement with the experimental measurements. The effects of the tube length to diameter ratio and the cold orifice size on the performance of the tube were investigated. The results showed that length to tube diameter ratio (L/D) affects the performance of the tube, and that this effect changes when operating the tube at different cold mass fractions. The results showed also that the maximum cooling occurs at the lowest cold orifice to tube diameter ratio (d c /D) at the lowest cold mass fraction (m c ) possible while the maximum heating occurs at the highest d c /D at the highest m c possible. Secondary circulations were investigated when operating at low d c /D values. In order to enhance the cooling capabilities of the tube fins were added to the tube to enhance the natural convection on the wall of the tube. © 2015 Published by Elsevier Ltd. 1. Introduction The VT (vortex tube) is a device with a simple geometry without moving mechanical parts [1e4]. It enables the separation of hot and cold air vortices from the inlet air, as it is supplied with compressed air that flows tangentially through the inlet nozzles [5e7]. The Vortex tube was first discovered in 1933 by the French physicist Georges J. Ranque [8], and in 1947 the German engineer Rudolf Hilsch improved and modified the design performed by Ranque [9]. The vortex tube consists of many parts [10,11] including one or more inlet nozzles, a vortex chamber, a control valve or a plug that is located at the hot end, a cold end orifice and a working tube [12]. When compressed air is injected tangentially through the inlet nozzles into the vortex chamber a strong rotational flow field (vortex) is formed at the periphery of the tube wall [13]. The vortex propagates till the end of the tube where some of the air leaves the tube via the hot outlet. However, adjusting the control valve at the hot outlet causes the rest of the air to reverse its direction and exit from the cold outlet along the centerline of the tube. It is noted that two vortices occur inside the tube, one at the periphery of the tube which exits at the hot outlet at a temperature much higher than the inlet temperature and the other one at the core of the tube with opposite flow direction which exits at the cold orifice with a tem- perature much lower than the inlet temperature. The VT is used in many applications such as cooling of airborne electronic components such as control circuits, cooling of gas samples such as petrochemical gas, and cooling of soldered parts including spot welding and ultrasonic welding. It is also used in the separation of air into nitrogen and oxygen rich fluid stream [14,15] which makes the VT a possible candidate for the use in the in-flight ACES (air collection and enrichment system) of air breathing propulsion. The VT has many advantages [16e19] because of its low cost, light weight, reliability, compactness and * Corresponding author. Tel.: þ20 1008213044. E-mail addresses: hamdykandil@gmail.com (H.A. Kandil), seif.abdelghany@ gmail.com, seifeldin.tarek@guc.edu.eg (S.T. Abdelghany). 1 Tel.: þ20 1006559603 Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2015.02.089 0360-5442/© 2015 Published by Elsevier Ltd. Energy 84 (2015) 207e218