CFD Analysis and Performance Evaluation of Concentric Tube in Tube Heat Exchanger - A Review Paper

IJIRST 窶的nternational Journal for Innovative Research in Science & Technology| Volume 1 | Issue 6 | November 2014 ISSN (online): 2349-6010

CFD Analysis and Performance Evaluation Of Concentric Tube in Tube Heat Exchanger- A Review Paper Jayesh .B Khunt Assistant Professor Mechanical Engineering Department Narnarayan shastri Institute of Technology, Jetalpur

Jalay .R Soni ME Student Mechanical Engineering Department Narnarayan shastri Institute of Technology, Jetalpur

Abstract An objective of the present dissertation work is to design and develop a CAD model of Tube in tube type counter flow Heat exchanger. The Dissertation is about preparing the CAD model as well modifying an experimental setup of tube in tube heat exchanger and use of different type of inner tube configuration for the estimation of heat transfer, pressure drop and change in velocity gradient. The experimental results are compared with the CFD results using CFD package, ANSYS CFX 14.0 A design has been made taking into consideration all the above mentioned Parameters and other real life circumstances which is also a part of this report.

Keywords: Helical coil, shell and mandrel, coil pitch, Reynolds number, heat transfer, mass flow rate, CFD simulation. _______________________________________________________________________________________________________

I. INTRODUCTION In chemical industries, heat exchangers are commonplace and allow the exchange or transfer of heat between two fluid streams that are at different temperatures. Usually, the two fluid streams are separated by a metal wall, which is also serves as the heat exchanger surface. Heat exchangers are commonly classified according to flow arrangements and type of construction (Incropera and DeWitt, 2002). Here, the discussion is restricted to the simplest type of heat exchanger - a concentric tube heat exchanger.1.1.1 Concentric Tube Heat Exchangers (CTHX)The concentric tube heat exchanger consists of two tubes that are concentrically arranged. One of the fluid (either hot or cold fluid) flows through the tube and the other through the annulus. For a CTHX, two types of flow arrangements are possible - co-current and counter-current flow. In the parallel or co-current arrangement, the flow direction of the hot fluid will be the same as that of the cold fluid. In the counter-current arrangement, the flow directions of the hot and the cold fluids are opposite to each other.

(a)Co-current or parallel flow (b) Counter-current flow Fig. 1: Flow arrangements in concentric tube heat exchangers (CTHX)

In Figure 1, the cold fluid stream is shown to flow in the inside tube and the hot fluid stream in the annulus, although reverse arrangement is also possible.

Prior to discussing the heat transfer in a CTHX, some basic concepts of heat transfer are presented.

(5) One of the key challenges in heat exchanger design and heat transfer calculations is the determination of the thermal resistance or the heat transfer coefficient (h).

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CFD Analysis and Performance Evaluation Of Concentric Tube in Tube Heat Exchanger- A Review Paper (IJIRST/ Volume 1 / Issue 6 / 039)

The current project focuses on experimental determination of the heat transfer coefficients. However, prior to discussing the methods for determination of heat transfer coefficients, it is important that we understand the mode(s) of heat transfer occurring so that appropriate equations are applied. Therefore, we will now take a close look at how the heat transfer between two fluids in a CTHX takes place.

The thin film represents a convective heat transfer resistance and is often interpreted in terms of a thermal boundary layer (Perry et al., 1963; Incropera and Dewitt, 2002). It must be emphasized that the assumption of the thermal resistance (and consequently the temperature drop) is present in a thin film of fluid adjacent to the tube wall is valid only for fully turbulent flow.

A simplified representation of heat transfer between two fluids through the walls of a CTHX is shown below in Figure 2.

Fig. 2: Simplified diagram to show heat transfer through walls of a CTHX

In the Figure above, the fluid flow on both the annulus (outside of the inner tube) and the inner tube is considered to be in the fully turbulent region. This is represented as a turbulent core wherein the fluid is completely mixed and no temperature gradients are present. However, there is a thin film adjacent to the surface of the walls both on the outside and inside of the inner tube. These thin films are considered to be convective resistance films where any and all temperature gradient on the fluid side exists. The flow of heat through the tubes takes place by conduction. Thus, the tube wall offers a conductive thermal resistance to the heat transfer from the hot fluid to the cold fluid.

II. LITERATURE REVIEW Rahul Kharat, Nitin Bhardwaj, R.S. Jha [1] “Development of heat transfer coefficient correlation for concentric helical coil heat exchanger” Found a Correlation for heat transfer coefficient for flow between concentric helical coils. Existing Correlation is found to result in large discrepancies with the increase in gap between the concentric coils when compared with the experimental results. In the present study experimental data and CFD simulations using Fluent 6.3.26 are used to develop improved heat transfer coefficient correlation for the flue gas side of heat exchanger. Mathematical model is developed to analyze the data obtained from CFD and experimental results to account for the effects of different functional dependent variables such as gap between the concentric coil, tube diameter and coil diameter which affects the heat transfer. Optimization is done using Numerical Technique and it is found that the new correlation for heat transfer coefficient developed in this investigation provides an accurate fit to the experimental results within an error band of 3–4%.

H. S. Patel ** R. N. Makadia [2] “A Review on Performance Evaluation and CFD Analysis of Double Pipe Heat Exchanger” Double pipe heat exchanger is one of simplest type of heat exchanger, generally used for the purpose of sensible heating or cooling. In this paper it describes the different techniques which may help to enhance the heat transfer rate. Heat exchangers are modified in space of annular, also using Nano particle in water and compared with the conventional heat exchanger. Double pipe heat exchanger is practically investigated and results are validated with Ansys CFX software. Results shows that heat transfer rate of modified heat exchanger are higher than the conventional heat exchanger. As Nano particles dispersed in water cansignificantly enhance heat transfer rate and also heat transfer rate increase with increase of mass flow rate.From the above literature survey it may conclude that heat transfer augmentation techniques is successful to increase heat transfer performance of double pipe heat exchanger. Heat exchanger with the modification of extended surfaces, twisted tape, and louvered strips are resulted greater heat transfer rate as compared to heat exchanger without modification. As Nanoparticles

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CFD Analysis and Performance Evaluation Of Concentric Tube in Tube Heat Exchanger- A Review Paper (IJIRST/ Volume 1 / Issue 6 / 039)

dispersed in water can significantly enhance the convective heat transfer and heat transfer rate increases with the increase of mass flow rate.

Antony luki.A , Ganesan.M [3] “Flow Analysis and Characteristics Comparison of Double Pipe Heat Exchanger Using Enhanced Tubes” In this investigation, augmented surface has been achieved with dimples strategically located in a pattern along the tube of a concentric tube heat exchanger with the increased area on the tube side. Augmented surfaces to increasing the heat transfer coefficient with a consequent increase in the friction factor. In this analysis to modify the inner tube of double pipe heat exchanger using dimpled tube. The concentric tube heat exchanger is design from Juin Chen a.et.al. Correlation. In this design the inner tubes consider as the hot flue gas and outer tube is nano fluid. Here In this study the properties of nano fluid from the alumina as the nano fluid with ethyl glycol as the base fluid. a. From this design calculation the heat transfer co efficient is increased compared to plain concentric tube heat exchanger. Similarly the effectiveness is 8% increased compared to plain concentric tube heat exchanger. The theoretical results show that the using dimpled tube in concentric tube heat exchanger gives better performance. The modeling and analysis is carried out to vary the dimple tube cross sections, ellipsoidal and spherical shapes using CFD. Finally the enhanced dimple tube is compare with the theoretical, analytical and analysis the results.From the above literature survey it may conclude that Augmented surfaces to increasing the heat transfer coefficient with a consequent increase in the friction factor. Here investigation dimpled tube is used. From theoretical calculation the overall heat transfer coefficient is increased and also effectiveness of the dimpled tube with concentric tube heat exchanger is increased 8% compare to plain tube concentric tube heat exchanger.

III. CONCLUSION A CFD model has been established and the associated numerical simulations have successfully been studied and obtained for a concentric high temperature heat exchanger with a simplification of staggered arrays of fins which simulate and simplify the internal structures of the flow channels. An optimal configuration of the high temperature heat exchanger is derived using Taguchi method.

The conclusions are listed as follows: (1) A CFD model has successfully been established to investigate the behavior of heat transfer and flow phenomena occurred in a concentric high temperature heat exchanger.

(2) The staggered arrays of flat plates which support the concentric pipes can also serve as thermal fins which are shown to significantly enhance the heat transfer capability of the high temperature heat exchanger due to a large increase of heat transfer area and the occurrence of flow turbulence from impingement effect.

REFERENCES [1] [2] [3] [4] [5]

Rahul Kharat, Nitin Bhardwaj*, R.S. Jha, “Development of heat transfer coefficient correlation for concentric helical coil heat exchanger, International Journal of Thermal Sciences 48 (2009) 2300–2308.

H. S. Patel ** R. N. Makadia, “A Review on Performance Evaluation and CFDAnalysis of Double Pipe Heat Exchanger, Indian journal of research- ISSN 2250-1991 Volume : 2- Issue : 4 - April 2013.

Antony luki.A, Ganesan.M, “Flow Analysis and Characteristics Comparison of Double Pipe Heat Exchanger Using Enhanced Tubes”, IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN: 2278-1684, p-ISSN: 2320-334X PP 16-21.

Mostafa Shojaeian, Mehmet Yildiz, Ali Kosar “Heat transfer characteristics of plug flows with temperature-jump boundary conditions in parallel-plate channels and concentric annuli”- International Journal of Thermal Sciences 84 (2014) 252e259.

Virendra Singh Yadav, Rohit Rajbaidya, Pankaj Dubey “Experimental Analysis of Heat Transfer Enhancement in Horizontal Circular Double Tube Heat Exchanger Using Snail”, global research analysis- Volume : 2 | Issue : 1 | Jan 2013 • ISSN No 2277 - 8160

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