Chemical Engineering and Processing 46 (2007) 941–954 Application of process decomposition in multi-stream plate fin heat exchangers design to use in heat recovery networks M. Khorrammanesh a , M. Amidpour a,∗ , M.R.J. Nasr b a Department of Energy System Engineering, Faculty of Mechanical Engineering, K. N. Toosi University of technology, Tehran, Iran b Research and Technology Company, National Petrochemical Company, Tehran, Iran Received 23 July 2006; received in revised form 20 June 2007; accepted 20 June 2007 Available online 7 July 2007 Abstract Application of multi-stream heat exchangers in heat recovery networks has a lot of advantages as low initial and operation costs, high thermal performance, low volume and weight. However, the main question arises encountering a real problem is: How many multi-stream plate fin heat exchangers are required for a specific process unit? Current work presents the financial drawbacks and thermal malfunction of the exchanger that may be appeared as a consequence of using a single heat exchanger in the process units consisted of several gaseous and liquid streams. Based on the design method, process limitations and physical properties, a new method of process decomposition will be introduced. In order to minimize the financial drawbacks due to increase of external utilities as a consequence of stream zoning, new stream zonal transfer will be presented. The applicability of the method is demonstrated on a case study. © 2007 Elsevier B.V. All rights reserved. Keywords: Multi-stream plate fin heat exchanger; Pinch technology; Heat recovery network; Problem decomposition 1. Introduction Multi-stream plate fin heat exchangers are used for simulta- neous transfer of heat between more than two streams in a single unit. They are used where high performance and low weight are required. They are used in cryogenic gas processing as main feed pre-coolers, condensers and liquid chillers, in aerospace industry as oil and fuel coolers, radiators and in HVAC industry as air to air exchangers, condensers and evaporators. The geometrical features of plate fin exchangers make them suitable for handling more than two hot and more than two cold streams in the same unit, however, the main concerns regarding the widespread use of heat exchangers of the plate fin type for multi-fluid applications are the limited range of temperature and pressure at which they operate and the restrictions regarding their application to relatively clean fluids. As a multi-stream heat exchanger may consists of a large number of passages or channels with several cold and hot ∗ Corresponding author. E-mail address: amidpour@kntu.ac.ir (M. Amidpour). streams, the heat transfer calculations of such systems performed on a channel by channel basis is complicated. So some simplifi- cations have been considered [1]. Simplification known as “the common wall temperature assumption” implies that at any posi- tion normal to the direction of the flow, all separating plates are at the same temperature. The assumption considerably reduces the heat transfer calculations with reasonably realistic answers compared with the common methods [1]. Based on the utilization of simplifications, the rating and sizing methods have been developed. To predict thermal per- formance of multi-stream heat exchangers, Prasad introduced a rating algorithm using half fin length idealization [2]. Math- ematical model and its analytical solution for the thermal performance of one-dimensional multi-stream heat exchangers were proposed by Kao [3], Haseler [4]. Furthermore, a general solution of predicting the steady state thermal performance of multi-stream exchangers was developed by Luo et al. [5]. For thermal sizing of plate fin heat exchangers, Kays and London successfully applied the –NTU method for the design of plate fin heat exchangers [6]. Some attempts have been made to extend the method to handle multi-stream heat exchangers [7]. 0255-2701/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.cep.2007.06.013