Design and Analysis of Heat Exchanger for Determined Heat Transfer Rate (Multi Model Optimization Procedure)

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Design and Analysis of Heat Exchanger for Determined Heat Transfer Rate (Multi Model Optimization Procedure)

Subham Sekhar Sahoo

1Master of Technology in Power Plant Engineering & Energy Management, Final Year Department of Mechanical Engineering.

O P Jindal University-496109.

Abstract – Heat exchanger as the name indicates it transfers heat from one fluid to another which are at changed temperatures. Heatexchangersaredevicesbuiltforefficient heat transfer from one fluid to another and are widely used in engineering processes. Some examples are intercoolers, pre-heaters, boilers and condensers in power plants. The heat transfer efficiency depends on both design of heat exchanger and property of working fluid. Some important design parameters such as the pitch ratio, tube length, and tube layer as well as baffle spacing. In this project, the heat transfer efficiency is improved by implementing the full baffle design and travel tube design and analyzing it through CFD flow simulation to find the approximate heat transfer rates.Fromthesimulationresultsthe optimumbaffledesign and travel tube design for maximum heat transfer rate is identified. Also this project deals with find the suitablefluid for maximum heat transfer rate.

Key words- CFD, Heat Exchanger,Baffle Angle.

  1. INTRODUCTIONA heat exchanger is a device used to transfer heat between oneormorefluids. Thefluidsmaybe separatedby a solid wall to prevent mixing or they may be in direct contact. Theyare widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, and sewage treatment. The classic example of a heatexchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. The order of reference in the running text should match with the list of references at the end of the paper.
      1. Shell and tube heat exchangerA Shell and tube heat exchanger Shell and tube heat exchangers consist of 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(with pressuresgreater than 30 bar and 3 temperatures greater than 260 °C). This isbecause 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: There can be many variations on the shell and tube design. Typically, the ends of each tube are connected to plenums (sometimes called water boxes) through holes in tube sheets. The tubes may be straight or bent in the shape of a U, called U- tubes.

        Fig -1: Shell and Tube heat exchanger

      2. Baffle Design

    Bafflesareused in shelland tubeheatexchangersto direct fluid across the tube bundle. They run perpendicularly to the shell and hold thebundle, preventing thetubesfromsagging over a long length. They can also prevent the tubes from vibrating. The most common type of baffle is the segmental baffle. The semicircular segmental baffles are oriented at 180 degrees to the adjacent baffles forcing the fluid to flow upward and downwards between the tube bundles.

    Baffle spacing is of large thermodynamic concern when designing shell and tube heat exchangers. Baffles must be spaced with consideration for the conversion of pressure drop and heat transfer. For thermo economic optimizationit is suggested that the baffles be spaced no closer than 20% of the shells inner diameter.

  2. METHODOLOGYSELECTION OF HEAT EXCHANGERIdentification of purpose, Parameters,

    Types, etc.

    Identification of purpose, Parameters,

    Types, etc.

    MODIFICATION

    Implementation of Fullbaffleintothe shell andtubeheat exchanger

    MODIFICATION

    Implementation of Fullbaffleintothe shell andtubeheat exchanger

    Creating3Dmodel ofheat exchanger with full baffleusing and travel tube Modeling software like SolidWorks.

    MODELLING CHANGES

    models with change the design of travel tube.

    MODELLING CHANGES

    models with change the design of travel tube.

    ANALYSIS

    CFD analysis on 3D model in SolidWorks

    ANALYSIS

    CFD analysis on 3D model in SolidWorks

    RESULTS

    Solutionforvariousinclined model areobtainedand tabulated for comparison.

    RESULTS

    Solutionforvariousinclined model areobtainedand tabulated for comparison.

    CONCLUSION

    for respective design of travel tube; optimum angle for maximum temperature drop is obtained

  3. DESIGN AND ANALYSISThe shell and tube heat exchanger is designed on the basis of Tube Exchanger Manufacturing Association (TEMA) 1999 procedure.
    S.NoParameterDimension
    1Type of heat exchanger1-1 pass shell and tube
    2Shell diameter0.088m
    3Shell length0.61m
    S.NoParameterDimension
    1Type of heat exchanger1-1 pass shell and tube
    2Shell diameter0.088m
    3Shell length0.61m

     

    Table -1: Design of Exchanger

    4Shell thickness0.003m
    5Tube diameter0.013m
    6Tube length0.61m
    7Tube thickness0.001m
    8Tube pitch0.023m
    9Tube pitch typeTriangular pitch
    10Tube clearance0.01m
    11Tube diameter ratio1.08
    12Pitch ratio1.76
    13Number of tube required13 tubes
    14Number of baffle required25 baffles
    15Baffle spacing0.022m

    Pitch type is taken as 60o triangular to utilize thebaffle space effectively.

    These design values and procedure are taken from the base paper Heat transfer enhancement of shell and tube heat exchanger.

    3.1 Model of Heat exchanger

    Fig -2: Full baffle for straight tube

    Fig -3: Straight travel tube

    Fig -4: Baffles with tubes & tube sheet

    Fig -5: Cut section of heat exchanger

  4. ANALYSIS PARAMETERS Fluid: WaterHeat Exchanger:- Material-Stainlesssteel321,Counter flowshell & tubeexchanger.

    Initial temperature: Hot fluid = 90oC Cold fluid = 26oC Flow rate: Hot & Cold fluid = 0.0027 m3/s Environmental Condition: 27oC, 1 atm&heatransfer coefficient 5 W/m2K

    Fig-6:Temperaturedistributionstraightbafflewith uniform tube

  5. VARIOUS DESIGN APPROACHES FOR TUBESFig -7: Angled TubeFig -8: Step Tube

    Fig -9: Combine of Angle and Step Tube

    5.1 ANALYSIS OF TUBES

    Heat exchanger parameters taken for analysis

    Fig -10: Analysis of Angled Tube min & max temp values

    Fig -11: Analysis of Step Tube min & max temp values

    Fig-12: Analysisof Angle+ Step Tubemin& maxtemp values

    Table -2: various tube analysis result table

    Type of tubeIn temp ocOut temp ocTemp different oc
    Normal straight tube9088.711.29
    Angle tube9085.534.47
    Step tube9085.044.96
    Combine of Angle and step tube9084.745.26
  6. ANALYSIS OF HEAT EXCHANGER BY ADJUSTING BAFFLE ARRANGEMENTSAnalysis carried out by adjusting the baffle arrangements in the heat exchanger which was done by making it inclined to surface. The angles of inclinations are 5o, 10o, 15o, 20o, 25o, 30o and 35o. it was limited to assembly convenient.
      1. Baffle Inclined to 5o :-Fig -13: Temperature distribution 5o inclined baffle
      2. Baffle Inclined to 15o :-Fig -14: Temperature distribution 15o inclined baffle
      3. Baffle Inclined to 25o :-Fig -15: Temperature distribution 25o inclined baffle
      4. Baffle Inclined to 35o :-Fig -16: Temperature distribution 35o inclined baffle
      5. Temperature drop in oC :-
  7. COOLANT FLUIDA coolant is a fluid which flows through a device in order to prevent its overheating, transferring the heat produced by the device to other devices that utilize or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, and is chemically inert, neither causing nor promoting corrosion of the cooling system. From various research journals here we selected CuO nano structures mixed with water as a coolant for max heat heat transfer rate.Table -2: Properties Cuo Nano structures
    Sl.NoPropertyCopper oxide
    1Thermal conductivity W/mK400
    2Density [p] kg/m36510
    3Specific heat [Cp] j/kg-K540
  8. FINAL DESIGN CONSIDERATION
    • Heat exchanger straight flow tube was replaced by Combine of Angle and step tube. It gives good thermal transfer capacity compared old straight tube and otherdesignsof tubes. It was obtained by computational flow analysis.
    • Baffle arrangement modifications also decides the heat transfer rate. The analysis carried out for making it inclined to the flow of hot fluid in theway of 5o,10 o,15 o,20 o,25 o, 30o and 35 o.
    • From the baffle arrangement flow analysis results the 35o inclinations of baffle gives good heat transfer rate comparing other inclination angles.Properties, and Potential Applications – International Scholarly Research Notices, Volume 2014, Article ID 856592 ) it was more efficient coolant compared other medium of coolant.
        1. Final DesignFig -17: Final effective model
        2. Final Analysis

      Fig -18: Final analysis

  9. RESULTS

Oxide Nanomaterials Prepared by Solution methods, Some

    • CuO nano particles was selected as a coolant fluid which was added with water and used as a coolant medium.
    • CuO nano particles was cheap and easily available Also from the latest research results ( Copper
    • The flow simulation analysis is carried out for various baffle arrangement heat exchangers and maximum heat transfer angle of the baffle arrange was found by result comparison .from the comparisons of the result 35o baffle arrangement gives better heat transferresults.
    • Formaximumheattransferratetheflowtubedesign was changed and best design was found by multi model optimization method. From the basic flow analysis results the angle and step tube combined design was gives maximum temperature drop results. So that type of flow tube was selected.
    • Fromthelatestjournalscoolantfluidwasselectedas a CuO + Water and their properties were given while making the final analysis of heat exchanger.
    • Finally the baffle was attached with our selected flow tube and placed inside the heat exchanger and analysis was carried out. From that analysis result temperature drop of the working fluid (water) is obtained and which was gives good results over previous results.9.1 Final Result discussion
    • Inlet temp of working fluid: 90oC
    • Outlet temp of the working fluid: 41.3621oCT= 48.638oC
    • Coolant inlet temperature: 26oC
    • Coolant outlet temperature: 68.321oC

REFERENCES

  1. Heat Transfer Enhancement of Shell and Tube Heat Exchanger- International Journal for Research in Applied Science and Engineering Technology, Vol. 2 Issue VIII, August 2014, ISSN: 2321-9653.
  2. CFD Analysis to study the effects of inclined baffles on Fluid Flow in a shell and tube Heat Exchanger International Journal of Research in Advent Technology, Vol.2, No.7, July 2014, E-ISSN: 2321-9637.
  3. Optimization of Shell & Tube Heat Exchanger by Baffle Inclination & Baffle Cut – International Journal of Innovative Research in Science, Engineering and Technology, Vol.4, Special Issue 12, September 2015.
  4. Comparison Of The Cooling Effects Of A Locally Formulated Car Radiator Coolant With Water And A Commercial Coolant- The International Journal Of Engineering And Science (IJES), Volume 2, Issue 01, January 2013.
  5. Standards of the tubular exchanger manufactures association – 9th edition.
  6. Classification of Heat Exchanger Pdf.
  7. Effectively Design Shell-and-Tube Heat Exchangers – Rajiv Mukherjee, Engineers India Ltd.
  8. Copper Oxide Nanomaterials Prepared by Solution methods, Some Properties, and Potential Applications – International Scholarly Research Notices, Volume 2014, Article ID 856592.

BIOGRAPHIES

Student Master of Technology in Power Plant Engineering & Energy Management, O.P Jindal University, Raigarh , Chhattisgarh.

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