heat transfer analysis of a helical coil heat exchanger by

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International Journal of Computational Science, Mathematics and Engineering Volume. 3, Issue. 5, 2016 ISSN-2349-8439 Heat Transfer Analysis of a Helical Coil Heat Exchanger by using CFD Analysis Dr. B.Jayachandraiah 1 *, H.S.S.K.Praveen 2 Abstract Helical Coil Heat Exchangers (HCHE) are widely used in industrial applications because they can accommodate a large heat transfer area in a small space, with high heat transfer coefficients. An attempt is made in this paper to evaluate the thermal performance of HCHE through CFD analysis. The modeling is done by using CATIA V5 software. The model contains the Coiled tube and Shell having an inner diameter of 8.41 mm and 260 mm respectively. The height of the shell is 250 mm. The material of the Shell and Coil is made up of Steel and Copper respectively. Computational Fluid Dynamics (CFD) Analysis is performed for different flow rates of 40, 60, 80, 100, 140 LPH at Coil side and constant flow rate of 200 LPH at Shell side in both laminar and turbulent flow regime under steady state conditions. It was found that the heat transfer characteristics were found better at the flow rate of 80 LPH and it is well desired to be maintained in the coil. . Keywords Helical Coil Heat Exchanger, CATIA V5 software, Computational Fluid Dynamics (CFD) Analysis, Heat transfer. 1 Prof of M.E and Vice-Principal, Dept. of Mechanical Engineering, SriKalahasteeswara Institute of Technology (SKIT), Srikalahasti, Chittoor Dt. A.P., India . 2 B. Tech Student, Dept. of Mechanical Engineering, SriKalahasteeswara Institute of Technology (SKIT), Srikalahasti, Chittoor Dt. A.P., India. Corresponding author:[email protected], [email protected] Contents 1 Introduction 5 2 Literature Review 6 2.1 Introduction ........................... 6 2.2 Objective Of The Paper .................. 6 3 Modeling 6 4 Meshing 6 5 CFD Analysis 7 5.1 Introduction ........................... 7 5.2 Turbulence Model ...................... 7 5.3 Mathematical Analysis ................... 7 6 Results 8 7 Conclusions 9 8 Future Work 10 References 10 1. Introduction Heat Exchangers are the most widely used equipment in power stations and petro-chemical industries. A Heat Exchanger is a contrivance designed to transfer thermal energy between two or more fluids over solid surface at different temperatures and when they are in thermal con- tact. The wall temperature also gets changed along the length of Heat Exchanger as temperature of each fluid changes during the passage through the Exchangers. A Shell and tube heat exchanger consists of series of tubes. They are typically used for high-pressure applica- tions (with pressures greater than 30 bar and tempera- tures greater than 260 °C). There can be many variations on the shell and tube design. Although Double-Pipe Heat Exchangers are the simplest to design, the better choice would be the Helical Coil Heat Exchanger (HCHE). The Helical coils of circular cross section have been used in wide variety of applications due to easy to man- ufacture. Flow in curved tube is different from the flow in straight tube because of the presence of the centrifugal forces. These centrifugal forces generate a secondary flow, normal to the primary direction of flow with circulatory effects that increases both the friction factor and rate of heat transfer coefficients.

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Page 1: Heat Transfer Analysis of a Helical Coil Heat Exchanger by

International Journal of Computational Science, Mathematics and EngineeringVolume. 3, Issue. 5, 2016

ISSN-2349-8439

Heat Transfer Analysis of a Helical Coil HeatExchanger by using CFD AnalysisDr. B.Jayachandraiah1*, H.S.S.K.Praveen2

AbstractHelical Coil Heat Exchangers (HCHE) are widely used in industrial applications because they can accommodatea large heat transfer area in a small space, with high heat transfer coefficients. An attempt is made in this paperto evaluate the thermal performance of HCHE through CFD analysis. The modeling is done by using CATIAV5 software. The model contains the Coiled tube and Shell having an inner diameter of 8.41 mm and 260 mmrespectively. The height of the shell is 250 mm. The material of the Shell and Coil is made up of Steel andCopper respectively. Computational Fluid Dynamics (CFD) Analysis is performed for different flow rates of 40,60, 80, 100, 140 LPH at Coil side and constant flow rate of 200 LPH at Shell side in both laminar and turbulentflow regime under steady state conditions. It was found that the heat transfer characteristics were found better atthe flow rate of 80 LPH and it is well desired to be maintained in the coil. .

KeywordsHelical Coil Heat Exchanger, CATIA V5 software, Computational Fluid Dynamics (CFD) Analysis, Heat transfer.

1Prof of M.E and Vice-Principal,Dept. of Mechanical Engineering,SriKalahasteeswara Institute of Technology (SKIT),Srikalahasti, Chittoor Dt. A.P., India .2B. Tech Student,Dept. of Mechanical Engineering,SriKalahasteeswara Institute of Technology (SKIT),Srikalahasti, Chittoor Dt. A.P., India.Corresponding author:[email protected], [email protected]

Contents

1 Introduction 5

2 Literature Review 62.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.2 Objective Of The Paper . . . . . . . . . . . . . . . . . . 6

3 Modeling 6

4 Meshing 6

5 CFD Analysis 75.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 75.2 Turbulence Model . . . . . . . . . . . . . . . . . . . . . . 75.3 Mathematical Analysis . . . . . . . . . . . . . . . . . . . 7

6 Results 8

7 Conclusions 9

8 Future Work 10

References 10

1. IntroductionHeat Exchangers are the most widely used equipmentin power stations and petro-chemical industries. A Heat

Exchanger is a contrivance designed to transfer thermalenergy between two or more fluids over solid surface atdifferent temperatures and when they are in thermal con-tact. The wall temperature also gets changed along thelength of Heat Exchanger as temperature of each fluidchanges during the passage through the Exchangers.

A Shell and tube heat exchanger consists of series oftubes. They are typically used for high-pressure applica-tions (with pressures greater than 30 bar and tempera-tures greater than 260 °C). There can be many variationson the shell and tube design. Although Double-Pipe HeatExchangers are the simplest to design, the better choicewould be the Helical Coil Heat Exchanger (HCHE).

The Helical coils of circular cross section have beenused in wide variety of applications due to easy to man-ufacture. Flow in curved tube is different from the flowin straight tube because of the presence of the centrifugalforces. These centrifugal forces generate a secondary flow,normal to the primary direction of flow with circulatoryeffects that increases both the friction factor and rate ofheat transfer coefficients.

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2. Literature Review

2.1 IntroductionLiterature survey of past research effort such as jour-nals or articles related to Shell and Helical Coil HeatExchanger and Computational Fluid Dynamics (CFD)analysis. Moreover, review of other relevant researchstudies are made to provide more information in orderto understand more on this research. Timothy John Ren-nie [1] has studied the heat transfer characteristics of adouble pipe helical heat exchanger for both counter andparallel flow. The results showed that the overall heattransfer coefficients varied directly with the inner deannumber ranging from 38 to 350 but the fluid flow condi-tions in the outer pipe had a major contribution on theoverall heat transfer coefficient. J. S. Jayakumar et al [2]have studied the constant thermal and transport proper-ties of the heat transfer medium and their effect on theprediction of heat transfer coefficients. An experimentalsetup was made for studying the heat transfer coefficientsand also compared with the CFD simulation results andthe correlation was established for the inner heat transfercoefficient. Nasser Ghorbani et al [3] have experimentallyconducted for mixed convection heat transfer in a Coil-in-Shell Heat Exchanger for various Reynolds numbers,Rayleigh numbers, tube-to-coil diameter ratios and dimen-sionless coil pitch. The calculations have been performedfor the steady-state. Results observed that the mass flowrate of tube-side to shell-side ratio was effective on theaxial temperature profiles of heat exchanger. Jundika C.Kurnia et al [4] have completed the Evaluation of the heattransfer performance of helical coils of non-circular tubes.They have performed for the three configurations-Conical,Helical, and Spiral. It was found that even though coiledducts give higher heat transfer rates, they also imposea higher pressure drop penalty. Shinde Digvijay D andDange H. M [5] have conducted the experimental researchon Helical Coil Heat Exchangers considering the counterflow. The conditions of hot water and cold water massflow rates were taken. For the flow rates ranging from 60LPH and 280 LPH characteristics were determined. Itwas observed that the Coil side flow rate has significantimpact on the performance of Heat Exchanger.

2.2 Objective Of The PaperAn attempt is made in this paper to design and analysisof Helical Coil Heat Exchanger. The modeling is done byusing CATIA V5 and meshed using Autodesk meshingsoftware. By applying the boundary conditions, CFDanalysis is carried-out in Autodesk CFD 2015.

Table 1. Geometrical dimensions for HCHE

Table 2. Fluid and Material Properties

3. Modeling

The Modeling of Helical Coil Heat Exchanger is createdby using CATIA V5 software which is a parametric solidmodeling system with many extended design and man-ufacturing applications. CATIA represents the leadingedge of CAD/CAE/CAM technology. This paper explainsabout the effective performance of Cone shaped HCHEover Simple HCHE.

4. Meshing

The meshing of Shell and Helical Coil Heat Exchanger isdone using Steady state Solution mode and TurbulenceModel Equation.Number of elements- 28,77,318

Figure 1. Design of Shell

Dr. B.Jayachandraiah1*, H.S.S.K.Praveen2 — 6/10

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Figure 2. Design of Helical Coil

Figure 3. Meshed HCHE

Number of Nodes-7,14,606

5. CFD Analysis

5.1 IntroductionA continuity equation is a differential equation that de-scribes the conservative transport of some kind of quan-tity. In Fluid dynamics, the continuity equation is a math-ematical statement that, in any steady state process, therate at which mass enters a system is equal to the rateat which mass leaves the system. The differential form ofthe continuity equation is:

(1)

Figure 4. Mass Flow in and Out of Fluid Element

5.2 Turbulence ModelThe model is one of the most common turbulence mod-els. It is a two equation model, which includes two extratransport equations to represent the turbulent propertiesof the flow. The first transported variable is turbulentkinetic energy, k. The second transported variable in thiscase is the turbulent dissipation. model has been usefulfor free-shear layer flows with relatively small Pressuregradients.

For Flow rates of 40, 60, 80, 100 and 140 LPH, ReynoldsNumber for HCHE are observed as 1421, 2082, 2844, 3470and 4859.5 At the flow rate of 40 LPH, Laminar flow isobserved while for the remaining flow rates, TurbulenceCondition is observed during the flow of fluid. A sampleanalytical calculation at the flow rate of 80 LPH is givenbelow based on the results obtained from CFD analysis.

5.3 Mathematical AnalysisAt Flow Rate of 80 LPH:

1. Heat Transfer Rate (QAvg)

(2)

2. Overall Heat Transfer Coefficient (U)

(3)

3. Dean Number (De)

(4)

4.Effectiveness

(5)

Dr. B.Jayachandraiah1*, H.S.S.K.Praveen2 — 7/10

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Table 3. Temperature Results of HCHE consideringVelocity

Table 4. HCHE result

The Critical Reynolds number, Recr for laminar to turbu-lent flow transition is calculated by the below equationconsidering curvature ratio for the coil:

(6)

6. ResultsThe below table shows the CFD temperature results inCoil and Shell sides for various flow rates. The belowtable shows the results of Heat transfer Rate, Overallheat transfer coefficient, Dean Number and Effectivenessat various flow rates of hot water in HCHE.

Velocity ContoursThe Velocity profile at hot water inlet is 500.35 mm/s.

Maximum Velocity obtained inside the Shell is 1208.39

Figure 5. Temperature distribution in the coil of HCHEat 60 LPH

Figure 6. Temperature distribution in the coil of HCHEat 100 LPH

Figure 7. Temperature distribution in the coil of HCHEat 140 LPH

Figure 8. Velocity Contour at 60 LPH

Dr. B.Jayachandraiah1*, H.S.S.K.Praveen2 — 8/10

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Figure 9. Velocity Contour at 100 LPH

Figure 10. Velocity Contour at 140 LPH

mm/s and turbulence occurs in the shell region. The Ve-locity profile at hot water inlet is 700.628 m/s. MaximumVelocity obtained inside the Shell is 1200.02 mm/s andturbulence occurs in the shell region. From the above fig-ure, it is observed that the temperature profile is gettingvaried to a greater extent at the flow rate of 140 LPH.

7. Conclusions1. From the analysis, it gives us a clear idea that hotfluid temperature is reduced to a great extent at the flowrate of 40 LPH and 80 LPH compared to other flow rates.Hence these are suggested as better flow rates to be main-tained in the Coil.2. The Heat transfer rate increases with increase in Flowrate at Coil side.3. The Overall Heat transfer Coefficient increases withincrease in Flow rate at Coil side. At 80 LPH, the devia-tion occurred which indicates the optimal flow rate in thecoil.4. Dean Number increases with increase in Coil side flowrate.5. The Heat Exchanger Effectiveness is decreased consid-

Figure 11. Iterations Vs Temperature distribution in theHCHE

Figure 12. Heat Transfer rate Vs Hot Water Flow rate

Figure 13. Overall Heat Transfer Coefficient Vs HotWater Flow rate

Figure 14. Dean number Vs Hot Water Flow rate

Figure 15. Effectiveness Vs Hot Water Flow rate

Dr. B.Jayachandraiah1*, H.S.S.K.Praveen2 — 9/10

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erably with increase in Coil side flow rate. The greaterEffectiveness of 0.80 was obtained at 40 LPH.

8. Future WorkIn the present paper, the CFD analysis is carried- outin order to evaluate the thermal performance of HelicalCoil Heat Exchanger considering the Volume Flow rateboundary conditions. The extension of this work can bedone considering other boundary conditions like Pressureand Wall heat flux etc.

References[1] Timothy John Rennie, “Numerical And Experimen-

tal Studies of a Double pipe Helical Heat Exchanger,”Dept. of Bio-resource Engg. McGill University, Mon-treal August, (2004)

[2] J.S. Jayakumar, S.M. Mahajani, J.C. Mandal, P.K. Vi-jayan, and Rohidas Bhoi, “Experimental and CFDestimation of heat transfer in helically coiled heat ex-changers,” Chemical Engg Research and Design pp.221-232 (2008)

[3] Nasser Ghorbani , Hessam Taherian, Mofid Gorji, Hes-sam Mirgolbabaei, “An experimental study of thermalperformance of Shell-And-Coil heat exchangers,” Inter-national Communications in Heat and Mass Transfer37 ,pp.775–781 (2010)

[4] Jundika C. Kurnia, Agus P. Sasmito, Arun S. Mujum-dar, “Evaluation of the heat transfer performance ofhelical coils of non circular tubes,” Journal of ZhejiangUniversity-SCIENCE A (Applied Physics and Engi-neering), 12(1):pp. 63-70. (2011)

[5] Shinde Digvijay D and Dange H. M, “Heat Trans-fer Analysis of a Cone Shaped Helical Coil Heat Ex-changer,” (IJET), Vol. 3 Issue 1 October (2013)

IJCSME OPEN ACCESSDr. B. Jayachandraiah Pro-

fessor at Sri Kalahasteeswara Insti-tute of Technology, Srikalahasti. Hecompleted his Masters in Mechani-cal Engineering from BITS, Pilaniwith specialization in IC Engines.He completed his PhD from JNTUH,Hyderabad in the area of IC EnginesCFD. The author has more than 25years experience in Teaching andResearch in various subjects of Me-chanical Engineering and he hasguided about 15 Masters Thesis and

number of B.Tech projects. He has credit to 50 publica-tions in various National and International journals andConferences. He is the Member in Institution of Engi-neers (India). Email Id:[email protected]

H.S.S.K.Praveen Final YearB.Tech Student at SriKalahas-teeswara Institute of Technology,Srikalahasti. He has completedB.Tech in Mechanical Engineeringwith distinction. He is the studentmember in Institution of Mechani-cal Engineers (IMechE).Email Id: [email protected]

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