Widely known that, heat exchanger is a device that is being used to transfer thermal energy (enthalpy) between two or more fluids, between a solid surface and a fluid, or between solid particulates and a fluid, at different temperatures and in thermal contact. The most common heat transfer devices are concentric tube (double pipe), shell and tube and, plate heat exchanger. Nowadays, Shell and tube heat exchangers were used extensively in most industries as petrochemicals, oil and refineries. According to previous survey, almost 45% of heat exchangers utilized are shell and tube heat exchangers due to its highpressure application it is more suitable in the field of oil & petrochemical application. Thus, the following study presented shell and tube type only. Due to complexity of studying heat exchangers experimentally, Computational Fluid Dynamics (CFD) used to simulate the effect of local surface heat transfer coefficients on the surfaces by aid of computer numerical calculation and graphical display. In addition, analysis of the physical phenomena involved in fluid flow and heat conduction would be presented in the following research paper with Comparative designs for shell and tube heat exchangers. The paper considered a review for the design of a shell and tube heat exchanger. A variety of heat exchangers are used in industry and in their products. The objective of this paper is to describe most of these heat exchangers in some detail using classification schemes and the basic design methods for two fluid heat exchangers. The design techniques of recuperators and regenerators. Therein, popular analytical techniques such as log mean temperature difference (LMTD) and effectiveness-number of transfer units (ε-NTU) were considered in the analysis. In the case considered herein, both LMTD and ε-NTU techniques yield the same exact results. Keywords-Heat Exchanger; Shell and tube heat Exchanger; parallel flow; counter flow; single pass shell and tube.

A different models of Shell-and-tube heat exchangers were designed by Ansys geometry & Solidworks to evaluate the best model for heat transfer and to calculate the difference in heat transfer in each model by investigated with numerically modeling. Each model for heat exchanger has different assumptions for first model one tube & one pass with tube length 3 meter, was made with 2 different cases (each case have the same conditions such as same temperature, same velocity, changing the direction of the flow between parallel and counter flow). The flow and temperature fields inside the shell and tubes are resolved using a Ansys CFD 17.2. A set of CFD simulations is performed for a single shell and tube bundle and is compared with the experimental results. the Realizable K-ε model is known for predicting the flow separation better than Standard K-ε. The temperature of each model is examined in detail. Each design was studied separately on the basis of the findings, the designs need modifications to improve heat transfer.The main goal of designing these models is to obtain highest performance for shell and tube heat exchanger with givien conditions. These studies were carried out to find the most suitable conditions of operation in shell and tube heat exchanger so that in the future it can improve the performance of heat exchanger in industries through applying these conditions. For future researches, the shell and tube heat exchanger the best case in performance will be chosen, then try to develop the shell and tube heat exchanger and reach maximum performance and efficiency of shell and tube heat exchanger. so that, in industries, the heat exchanger will be easier to be chosen based on the function and conditions required.

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