Tube bundle replacement for segmental and helical shell and tube heat exchangers: Performance comparison and fouling investigation on the shell side Sirous Zeyninejad Movassag a, * , Farhad Nemati Taher a , Kazem Razmi a , Reza Tasouji Azar b a Department of Mechanical Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran b Research and Development Department, Tabriz Petrochemical Company, Tabriz, Iran highlights < Performance comparisons in the shell-side by tube bundle replacement with segmental and helical baffles have been conducted. < Helical baffles resulted in better performance compared to segmental baffles in running time. < Helical baffle arrangement provides smooth behavior of the fluid flow on the shell side which leads to lower pressure drop. < Flow separation phenomenon, mixing flow and back flow, abrupt changes of fluid flow direction at the baffles tips, higher velocity magnitude which all lead to higher pressure drop were observed for segmental baffles. < For the same pressure drop, helical baffles resulted in higher heat transfer. article info Article history: Received 30 May 2012 Accepted 16 October 2012 Available online 26 October 2012 Keywords: Shell and tube heat exchangers Tube bundle replacement Segmental and helical baffle arrangements Fouling Heat transfer and pressure drop abstract Conventional segmental baffles in shell and tube heat exchangers, while having an excellent record of acceptance and functionality, represent some limitations and shortcomings. In particular, shell-side flow path is wasteful which causes excessive pressure loss while recovering less heat transfer. This particular arrangement of baffles also limits maximum thermal effectiveness and encourages dead zones where fouling occurs. This paper describes the results of tube bundle replacement of a segmental shell and tube heat exchanger with a helical heat exchanger, which was conducted in Tabriz Petroleum Company. The aim of the project was to reduce fouling and pressure drop of the critical heat exchanger and; as a result, reduce operation and maintenance costs. Present paper consists of 3 phases. First, tube bundle replacement in industrial field and also the advantages of helical baffles over conventional segmental baffles are going to be discussed. Then, due to limits on the access to the heat exchangers in production lines, comparison of shell-side flow behavior in both cases is going to be presented by CFD means. Finally, computational code is going to be introduced to investigate on heat transfer and pressure drop for both segmental and helical shell and tube heat exchangers. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Shell and tube heat exchangers (STHXs) are the most common of the various types of unfired heat transfer equipment which are used in the industrial fields such as: process industries, conven- tional and nuclear power stations, petroleum refining and steam generation. Although they are not especially compact, they are robust and their rugged shapes make them well suited for high pressure operations. Moreover, they are versatile and can be designed to suit for almost any application. A variety of different internal constructions are used both in the shell and tube sides of STHXs to achieve the most desirable performance for vast ranges of operation conditions. Baffles, as important components, provide support for tubes, enable a desir- able velocity to be maintained for the shell-side fluid flow, and prevent the tubes from vibrating. Baffles also guide the shell-side flow to move forward across the tube bundle, increasing fluid velocity and heat transfer coefficient. Newly employed baffles, known as helical baffles, which were developed in Czech Republic for the first time by Lutcha and * Corresponding author. Tel.: þ98 9144105984. E-mail address: s.zeyninejad@gmail.com (S. Zeyninejad Movassag). Contents lists available at SciVerse ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng 1359-4311/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.applthermaleng.2012.10.025 Applied Thermal Engineering 51 (2013) 1162e1169