CFD ANALYSIS OF DOUBLE PIPE PARALLEL FLOW HEAT EXCHANGER

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1 CFD ANALYSIS OF DOUBLE PIPE PARALLEL FLOW HEAT EXCHANGER 1 DIVI VENKATA PRASHANTH, 2 GOROGINAM SANTHI 1 Pg Scholar, Department of MECH, BRILLIANT GRAMMER SCHOOL EDUCATIONAL SOCIETY S (BRIG),JNTUH,Hyderabad.Abdullapurmet (V), Hayathnagar (M), Hyderabad, Telangana, India. 2 Assistant Professor, Department of MECH, BRILLIANT GRAMMER SCHOOL EDUCATIONAL SOCIETY S (BRIG),JNTUH,Hyderabad.Abdullapurmet (V), Hayathnagar (M), Hyderabad, Telangana, India. Abstract: A heat exchanger is a device that is 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 distinctive temperatures and in thermal contact. Heat exchangers are important engineering devices in many process industries since the efficiency and economy of the process largely depend on the performance of the heat exchangers.the present work is directed towards the modeling of shell and tube parallel flow heat exchanger in solidworks 2014 and setting up of flow simulation in solidworks by inserting boundary conditions, running the calculations, inserting surface parameters, using cut plots and flow trajectories to visualize the resulting flow field.finally compared the flow simulation results with effectiveness-ntu method.there is a difference of 7.3% of flow simulation results with effectiveness NTU method. Introduction To Heat Exchangers : A heat exchanger is a device that is used to transfer thermal energy (enthalpy) between two alternately more fluids, between a strong or solid surface and a fluid at distinctive temperatures and in thermal contact. In hotness or heat exchangers, there are normally no external heat and work collaborations. Commonplace applications include warming(heating) or cooling of a fluid stream of concern and dissipation or buildup of single-or multi segment fluid streams. In different applications, the destination may be to recover or reject heat, or sterilize, distill, fractionate, concentrate, pasteurize, crystallize, or control a process fluid. In a couple of heat exchangers, the fluids trading or exchanging hotness or temperator are in immediate contact. In mostly heat exchangers, high temperature exchange or heat tranfer between fluids happens through a dividing divider(wall) or into and out of a divider(wall) in a transient way. In numerous heat exchangers, the fluids are differentiated by a heat transfer surface, and in a perfect world they don't blend or break. Such exchangers are named as direct exchanger, or essentially recuperate. In contrast, exchangers in which there is intermittent heat exchange between the hot and cold fluids via thermal energy storage and release through the exchanger surface or matrix are referred to as indirect transfer type, or fundamentally regenerators. Such exchangers usually have fluid leakage from one fluid stream to the other, due to pressure divergences and matrix rotation/valve switching. Common examples of heat exchangers are automobile radiators, condensers, shell-and-tube exchangers, evaporators, cooling towers, and air pre

2 heaters. On the off chance that no stage change happens in any of the fluids in the exchanger, it is here and there alluded to as a sensible heat exchanger. There could be internal thermal energy sources in the exchangers, such as in electric heaters and nuclear fuel elements. Combustion and chemical reaction may take place within the exchanger, such as in boilers, fired heaters, and fluidized-bed exchangers. Mechanical devices may be used in some exchangers such as in scraped surface exchangers, agitated vessels, and stirred tank reactors. Heat transfer in the separating wall of a recuperator generally takes place by conduction. Classification Of Heat Exchangers According To The Flow Direction: a) parallel flow b) Cross flow c) Counter flow TYPES OF HEAT EXCHANGERS : 1.SHELL AND TUBE HEAT EXCHANGER : Shell and tube heat exchangers consist of a series of tubes. One set of these tubes contains the fluid that must be either heated or cooled. The second fluid runs over the tubes that are being heated or cooled so that it can either provide the heat or absorb the heat required. A set of tubes is called the tube bundle and can be made up of several types of tubes: plain, longitudinally finned, etc. Shell and tube heat exchangers are typically used for high-pressure applications. This is because the shell and tube heat exchangers are robust due to their shape. Several thermal design features must be considered when designing the tubes in the shell and tube heat exchangers: Tube diameter: Using a small tube diameter makes the heat exchanger both economical and compact. However, it is more likely for the heat exchanger to foul up faster and the small size makes mechanical cleaning of the fouling difficult. To prevail over the fouling and cleaning problems, larger tube diameters can be used. Thus to determine the tube diameter, the available space, cost and the fouling nature of the fluids must be considered.

3 b). Plate and fin heat exchanger : This type of heat exchanger uses "sandwiched" passages containing fins to increase the effectiveness of the unit. The designs include crossflow and counterflow coupled with various fin configurations such as straight fins, offset fins and wavy fins. c). Spiral heat exchanger: 2.COMPACT HEAT EXCHANGER: Compact heat exchangers are a class of heat exchangers that incorporate a large amount of heat transfer surface area per unit volume. The compact heat exchangers are : a). Plate heat exchanger : the plate heat exchanger is composed of multiple, thin, slightly separated plates that have very large surface areas and fluid flow passages for heat transfer. This stacked-plate arrangement can be more effective, in a given space, than the shell and tube heat exchanger A spiral heat exchanger (SHE), may refer to a helical (coiled) tube configuration, more generally, the term refers to a pair of flat surfaces that are coiled to form the two channels in a counter-flow arrangement. Each of the two channels has one long curved path. A pair of fluid ports are connected tangentially to the outer arms of the spiral, and axial ports are common, but optional. Applications Of Heat Exchangers: Heat exchangers are used in a wide variety of applications such as home heating,

4 refrigeration, air conditioning, petrochemical plants, refineries as well as in natural gas processing. In many industrial processes a heat exchanger helps in using the wasted heat from one process to be utilized in another process which saves a lot of money while being efficient at the same time. Cooling of hydraulic fluid and oil in engines, transmissions and hydraulic power packs. Heat exchangers are used in many industries, including: -Waste water treatment -Refrigeration -Wine and beer making -Petroleum refining Introduction To Solidworks : Solidworks mechanical design automation software is a feature-based,parametric solid modeling design tool which advantage of the easy to learn windows TM graphical user interface. We can create fully associate 3-D solid models with or without while utilizing automatic or user defined relations to capture design intent. Parameters refer to constraints whose values determine the shape or geometry of the model or assembly. Parameters can be either numeric parameters, such as line lengths or circle diameters, or geometric parameters, such as tangent, parallel, concentric, horizontal or vertical, etc. Numeric parameters can be associated with each other through the use of relations, which allow them to capture design intent Modelling Of Shell And Tube Heat Exchanger Modelling of shell and tube heat exchanger is as follows : In commercial aircraft heat exchangers are used to take heat from the engine's oil system to heat cold fuel. Solidworks Solid Works is mechanical design automation software that takes advantage of the familiar Microsoft Windows graphical user interface. It is an easy-to-learn tool which makes it possible for mechanical designers to quickly sketch ideas, experiment with features and dimensions, and produce models and detailed drawings.

5 Figure :setting of inlet massflow rate and temperature for hot water tube inlet For shell inlet: Solidworks Flow Simulation Setting of inlet mass flow rate of 0.8kg/sec and temperature of 283.2k for shell inlet by selecting inner face lid as boundary condition as shown : Introduction : SolidWorks Flow Simulation 2010 is a fluid flow analysis add-in package that is available forsolidworks in order to obtain solutions to the full Navier-Stokes equations that govem the motion of fluids. Other packages that can be added to SolidWorks include SolidWorks Motion and SolidWorks Simulation. Insertion Of Boundary Conditions: Figure:setting of inlet massflow rate and temperature for cold water shell inlet For tube outlet: For tube inlet: Selecting inlet mass flow rate of 0.2kg/sec with temperature of 343.2k to the inner face of lid of tube as boundary condition as shown below : Figure : environment pressure at tube outlet

6 For shell outlet: Flow Trajetories Of Shell And Tube Heat Exchanger: Figure : Environment pressure at shell outlet Results: Goal plots Temperature distribution along the tube Graphs: For tube: Minimum temperature Temperature distribution along the shell Average temperature

7 Maximum temperature: For shell: Minimum temperature: Effectiveness-Ntu Method : For a given heat exchanger and two fluids if only the inlet temperatures and flow rates are specified and the exit temperatures of the two fluids are to be calculated,effectiveness-ntu method can be used. The effectiveness -NTU method for comparison of outlet ternperatures with Flow Simulation results for the shell and tube heat exchanger. First, we determine the heat capacity rates of the shell and the tube fluids, respectively. The heat capacity rate of the shell C s, and tube C t, fluids. Using results from Flow Simulation, we get the following effectiveness Average temperature Maximum temperature ϵ = ( ) / ( ) = This is a difference of 7.3% as compared with the effectiveness - NTU method. Results And Discussion: By following the above steps the modeling of Shell and Tube heat exchanger has been done using solid works software and also using solid work flow simulation the flow analysis is done to calculate the effectiveness of the shell and tube heat exchanger. The mass flow rate of water in the shell is 0.8kg/s with an inlet temperature of 283.2k and the mass flow rate of water in tube is0.2 kg/s at an inlet temperature of 343.2k. Then after setting up these boundary conditions we can observe the temperature difference of about 2-3 degrees. By using the flow simulation software we can get the effectiveness of the heat exchanger as

8 By using NTU method we can get the effectiveness as so we nearly get 7.3 % difference between the NTU method and the flow simulation method. This difference is mainly due to the reason that the calculation is done for unit length and there were so many assumptions like the mass flow rate is constant and the radiation and convectional losses are neglected. Conclusion And Futurescope Discussion: The design and CFD analysis on shell and tube heat exchanger has been done and the results were compared with the effectiveness NTU method. We had observed a considerable amount of deviation from the actual value to the value that is obtained in the simulation. This project has further developments like considering different types of flows like cross, parallel and counter flow. And also here we have considered that the radiation and convection losses as zero where as in practical situations they will exist so this project can be further extended in that path. Since the significance of various design soft wares is increasing day by day this project can be executed in any kind of design soft wares like PRO-E and CATIA. But Since the SOLID WORKS platform is user friendly we opted for this software. References: 1. cengel, Y. A., Heat Transfer: A Practical Approach, 2"d Edition, McGraw- Hill, Solid Works Flow Simulation DIVI VENKATA PRASHANTH Completed B.TECH. in Mechanical in 2010 from Dr.Paul Raj Engineering College, Bhadrachalm Affiliated to JNTUH, Hyderabad. M.Tech in Thermal Engineering in from Brilliant Grammer School Educational Society s (BRIG) Affiliated To JNTUH, Hyderabad. Abdullapurmet (V), Hayathnagar (M), Hyderabad, Telangana, India. id: prashanthvenkatadivi@gmail.com 2. GOROGINAM SANTHI Completed B.Tech in MechanicalEngineering in 2013 from Panineeya Institute Of Technology And Science Engineeringcollege,Chaitnyapuri Affiliated to JNTUH, Hyderabad and M.Tech in Thermal Engineering in 2015from Brilliant Grammer School Educational Society s (BRIG) Engineering College Affiliated to JNTUH,Hyderabad. Working as Assistant Professor at Brilliant Grammer School Educational Society s (BRIG), Abdullapurmet (V),Hayathnagar Mandal, Hyderabad, Telangana, India. id: santhigoroginam@gmail.com