VOL. 11, NO. 20, OCTOBER 2016 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences © 2006-2016 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 12159 FLOW DYNAMICS BEHAVIOUR OF A NOVEL LIQUID-LIQUID HYDROCYCLONE WITH VARYING UPPER CYLINDRICAL LENGTHS AND NUMBER OF INLETS H. Osei, H. H. Al-Kayiem and A. B. Osman Mechanical Engineering Department, Universiti Teknologi Petronas, Bandar Seri Iskandar, Perak, Malaysia E-Mail: hussain_kayiem@petronas.com.my ABSTRACT The use of a liquid-liquid hydrocyclone in the downhole is one the few environmentally friendly ways by which water production can be limited, while at the same time ensure maximum recovery. The understanding of the fluid flow behaviours that bring about better separation and performance is therefore important and should not be underestimated. This work, through numerical simulation, studied the effects that the tangential inlet(s) and the height of the upper cylindrical section of a liquid-liquid hydrocyclone have on its hydrodynamics. The results showed that the single inlet hydrocyclones unlike the twin inlet types are more prone to producing asymmetrical reversal flow which meanders along the axis of the hydrocyclone. This can affect the efficiency of separation if the particles are not well segregated. The single inlet 30 mm upper cylindrical length (UCL) hydrocyclone produced the highest velocity fields that could ensure better fluid swirling and rotation, and the greatest upward core flowing pressure that could ensure better transportation of the lighter fraction concentrated at the core. Therefore, the single inlet hydrocyclone with 30 mm UCL is the best among the studied cyclonic separator types and its use for downhole oil/water separation can enhance the problem of excessive water production. Keywords: hydrocyclone, axial velocity, tangential velocity, reversal flow. INTRODUCTION Hydrocyclone is a centrifugal separator which has been used as an industrial classification/separation device in industry since the 1940s. It finds wide application in the petroleum, chemical, mineral/mining, pharmaceutical, environment and food industries, etc. [1-2]. In the nineteenth century, Bretney [3], patented the first hydrocyclone and it was composed of a cylindrical section, a cone, overflow outlet and underflow outlet. The function of the cylindrical section is to stabilize the fluid flow when the fluid enters the cyclone; the cone, to enhance the centrifugal force which helps in separating the fluid particles within the hydrocyclone; the overflow outlet, to provide a way through which the lighter fraction of the fluid will leave the system and the underflow outlet to carry the heavier fraction of the fluid [1]. The simplicity of the hydrocyclone in terms of design, low in production and maintenance costs, and easy operation [4] have boosted its role in the separation of liquid-liquid products, gas-liquid products and liquid-solid products [1, 5-6]. Liquid–liquid hydrocyclones are the types used in separating one liquid from another by utilizing the advantage of the difference in their densities. Its working principle is the same as any other hydrocyclone. The use of liquid-liquid hydrocyclone to separate oil and water was first proposed by Simkin and Olney [7] and became widely accepted and popular in the 1980s [8-9]. The feed enters the hydrocyclone through the inlet(s) tangentially positioned so as to produce a vortex inside its unmoving body. The feed spirals under the centrifugal force generated within the hydrocyclone and by taking advantage of differential density between the fluid particles, separation occurs in the radial direction. Thus the particles are arranged with the lightest at the core of the hydrocyclone to the densest at the wall of the hydrocyclone [4]. A reversal flow is created at the core of the cyclone which flows counter currently to the main flow and this occurs when the underflow outlet is maintained at higher pressure than that at the overflow [6]. For separation to occur, each fluid particle within the injected fluid stream has to undergo some flow mechanisms before it is finally separated as either underflow or overflow. This flow physics is very important as the dearth of knowledge about it can lead to ineffective cyclone performance and wasted resources. This study is to showcase what happens inside a novel liquid-liquid hydrocyclone to bring to light the flow and velocity patterns that contribute to bringing about separation. The effects of the length of the upper cylindrical column and the number of inlets of the cyclone will also be known. NUMERICAL METHOD AND CONDITIONS Numerical simulation has become an important tool in recent times and finds application in many areas of research, industry and development. With the advent of vast computer resources, numerical simulation has become a faster and cheaper way to get promising results to problems. In this work, numerical studies were carried out using ANSYS–CFX software to study the flow fields in liquid-liquid hydrocyclone with different upper cylindrical lengths and number of inlets. Figure-1 shows the schematics of the liquid-liquid hydrocyclone employed in this paper which is a modification after Colman and Thew’s type [10-11]. Two upper cylindrical lengths (UCLs) specifically, L1 = 30 mm and 60 mm were