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International Journal of Mathematical Sciences, Technology and Humanities 4 (2011) 37 52

STRUCTURAL AND THERMAL ANALYSIS OF CONDENSER

BY USING FINITE ELEMENT ANALYSIS

Sk. Abdul Mateen1

and N. Amar Nageswara Rao2

Mechanical Engineering Department,Nimra College of Engineering & Technology,

Ibrahimpatnam, Vijayawada.

ABSTRACT:

In any power plant apart from the turbine, boiler and pump, the condenser is a vital component.Steam condenser is a device or an appliance in which steam condenses and heat released by

steam is absorbed by water. The main considerations in the design of a condenser for aparticular application are Thermal design and analysis, Mechanical design, Design for

manufacture, physical size and cost.

The condenser is analyzed for static and thermal loading .The geometry of condenser is

created in CATIA software as per the drawing .This model is imported to HyperMesh through

IGES format and then for sheet metal components we will extract the mid surface, now for thatmid surface we will create shell elements, solid elements were created for remaining part, and aconverged mesh is developed in HyperMesh. The finite element model with various loading

conditions are design pressure, hydro test pressure ,full vaccum, thermal loads and operatingconditions (both mechanical and thermal loads) on the condenser .The supporting legs one is

arrested in all the directions and the other one is arrested only in Z- direction and all rotations.All these are created by using HyperMesh and it is exported to ANSYS for solution. The

deflections and stresses were obtained from analysis. Those values are correlated with materialallowable values as per the ASME Section VIII Division 2.

Keywords: Condenser Analysis, Structural and Thermal Analysis, Finite Element

Analysis

1. INTRODUCTION

A steam condenser is a device or an appliance in which steam condenses and heat released bysteam is absorbed by water. Condenser are important heat and mass exchange apparatus in oil

refining, chemical engineering, environmental protection, electric power generation, et al.Among different types of condenser, shell and tube condenser have been commonly used in


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Sk. Abdul Mateen and N. Amar Nageswara Rao


industries [1]. Master et al, [2] indicated that more than 3540% of heat exchangers areof the shell and tube type, and this is primarily due to the robust construction geometry

as well as easy maintenance and possible upgrades of shell and tube condenser. They arewidely used as evaporators and condensers. The heat transfer effectiveness of shell and tube

condenser can be improved by using baffles. Segmental baffles are most commonly used in

conventional shell and tube condenser to support tubes and change fluid flow direction.Segmental baffles cause the shell-side fluid to flow in a tortuous, zigzag manner across thetube bundles, which can enhance the heat transfer on the shell side[3-6].

2. DESCRIPTION

In this work static and thermal analysis of the condenser made of carbon steel was carriedout.

Table 1. Material properties of Carbon Steel- SA 516 Gr 70

Material

Properties

Magnitudes

Density, tons/mm3 1.3738e-8

Youngs Modulus,

N/mm2

1.9e5

Poissons Ratio 0.3

Thermal

Expansioncoefficient

7.1*e-6 /oc

3. MODELLING AND MESHING

With the dimensional parameters the structure is modeled in CATIA modeling software as

shown in Fig.1The model is meshed for further analysis using a

Fig.1: The geometric model of the Condenser using CATIA.

meshing package HYPERMESH with free and mapped mesh. Meshing of the componentplays an important role in analysis, as it is the basis for analyzing the component in any

software package, which supports finite element techniques. The model consists of 74798elements. Appropriate boundary conditions are incorporated in the analysis. Fig 2 shows

shell 63 element and Fig3 shows solid 45 element considered for meshing. FE model ofthe condenser is shown in Fig 4.


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Shell 63 Elastic Shell

It is defined by four nodes and six degrees of freedom i.e. UX, UY, UZ, ROTX, ROTY,

ROTZ at each node. The element has stress stiffening, large deflection, and birth and

death capabilities.

Fig.2: Shell63 Geometry

Solid45 3d-Structural Solid

It is defined by eight nodes and three degrees of freedom i.e. UX, UY, UZ at each node.The element has plasticity, elasticity, large deflection Capabilities.

Fig.3: Solid45 3d-Structural Solid

Fig.4: The Finite Element Model of the Condenser


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Table 2. Mesh is created in HyperMesh with the following quality parameters

4. CONDENSER

4.1 Structural Analysis

Static analysis was carried out to know the strength of the condenser, which includes theparameters such as the design pressure, full vaccum and hydro test pressure. The Analysis

has been carried out for these cases:

Case1). Design PressurePressure = 0.1078 MPa.

Case2). Full VaccumPressure = 0.10135 MPa

Case3). Hydro static PressurePressure =0.157 MPa

4.2 Thermal Analysis

Thermal analysis was carried out to know the thermal stresses of the condenser, which

includes the parameters such as thermal loading (stresses due to temperature) andCombined loading (both structural and thermal).The Analysis has been carried out for

these cases:

Case4). Thermal loading (stresses due to temperature).

T = 99o c

Case5).Combined loading (both structural and thermal) Pressure=0.09316MPa andTemperature=44.450c

Max warpage 23

Aspect Ratio 3.95

Skew 60

Minangleof quad 35

Max angle of quad 152

Jacobian 0.55

Min angle of trias 21

Max angle of trias 110


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RESULTS

Case 1. Design Pressure

Table 3. The induced displacements and stresses with Design Pressure of 0.1078 MPa

Name Results as per

Analysis

Allowable stress as per ASME SEC

VIII DIV.2 (MPa)

Reference figure

Displacement

in X-direction, mm

1.174 7 5

Displacementin Y-

direction, mm

0.7962 7 6

Displacement

in Z-direction, mm

1.267 7 7

Shear stress

in XY-plane,MPa

19.409 157.2 8

Shear stressin YZ-plane,MPa

36.53 157.2 9

Shear stress

in XZ-plane,MPa

94.738 157.2 10

StressIntensity ,

Mpa

261.689 524 11

From the table 3 it is observed that the maximum stress induced is less than allowable stresses.

Hence the design is safe as per the strength criteria. Fig 5 to Fig 7 shows the variation of maxdisplacement in X, Y and Z-directions respectively 1.174, 0.7962 and 1.267 mm. The max.

allowable displacement is 7mm. Hence the design is safe based on rigidity.

Fig.5: The Displacement in X-direction


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Fig.6:The Displacement in Y-direction

Fig.7: The Displacement in Z-direction

Fig.8: The variation of Shear Stress in XY-plane

Fig.9: The variation of Shear Stress in YZ-plane


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Fig.10: The variation of Shear Stress in XZ-plane

Fig.11:The variation of Stress Intensity

Fig 8 to Fig 11 shows the variations of normal and shear stresses. From the figure it is observedthat the maximum stresses induced is 261.689 Mpa, which is less than allowable stress.

Case 2. Full Vaccum

Table 4. The induced displacements and stresses with Full Vaccum pressure of 0.01035

MPa

Name Results as per

Analysis

Allowable stress as per

ASME SEC VIII DIV.2(MPa)

Reference figure

Displacement in X-direction, mm

1.104 7 12

Displacement in Y-

direction, mm

0.7485 7 13

Displacement in Z-

direction, mm

1.11 7 14

Shear stress in XY-

plane, MPa

18.248 157.2 15

Shear stress in YZ-

plane, MPa

89.07 157.2 16

Shear stress in XZ-plane, MPa

34.184 157.2 17

Stress Intensity ,

Mpa

245.94 524 18


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From the table 4 it is observed that the maximum stress induced is less than allowable stresses.Hence the design is safe as per the strength criteria. Fig 12 to Fig 14 shows the variation of max

displacement in X, Y and Z-directions respectively 1.104, 0.7485 and 1.11 mm. The max.allowable displacement is 7mm. Hence the design is safe based on rigidity.

Fig.12:The Displacement in X-direction.


Fig.14:The Displacement in Z-direction

Fig.15:The variation of Shear Stress in XY-plane

Fig.16:The variation of Shear Stress in YZ-plane


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Fig.17:The variation of Shear Stress in XZ-plane



Case3. Hydrotest Pressure

Table 5. The induced displacements and stresses with Hydrotest pressure of 0.157 Mpa

Name Results as per

Analysis



Reference

figure

Displacement in X-

direction, mm

1.71 7 19

Displacement in Y-direction, mm

1.158 7 20

Displacement in Z-direction, mm

1.72 7 21

Shear stress in XY-

plane, MPa

28.268 157.2 22

Shear stress in YZ-plane, MPa

52.955 157.2 23

Shear stress in XZ-

plane, MPa

137.977 157.2 24

Stress Intensity , Mpa 381.125 524 25


displacement in X, Y and Z-directions respectively 1.71, 1.158 and 1.72 mm. The max.allowabledisplacement is 7mm. Hence the design is safe based on rigidity.


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Fig.19: The Displacement in X-direction

Fig.20: The Displacement in Y-direction



Fig.23:The variation of Shear Stress in YZ-plane


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Fig.24:The variation of Shear Stress in XZ-plane



Case4. Thermal Loading

Table 6. The induced displacements and stresses with uniform Temperature loading of

990C

Name Results as

per Analysis



Reference

figure

Displacement in X-direction,mm

0.6241 7 26

Displacement in Y-direction,mm

3.004 7 27

Displacement in Z-direction,mm

1.461 7 28

Shear stress in XY-plane,MPa

32.88 157.2 29

Shear stress in YZ-plane,MPa

119.665 157.2 30

Shear stress in XZ-plane,

MPa

86.462 157.2 31



displacement in X, Y and Z-direction respectively 0.6241, 3.004 and 1.461 mm. The max.allowable displacement is 7mm. Hence the design is safe based on rigidity.


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Fig.26:The Displacement in X-direction




Fig30:The variation of Shear Stress in YZ-plane


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Fig31:The variation of Shear Stress in XZ-plane

Fig.32:The variation of Stress Intensity.

Fig 29 to Fig 32 shows the variations of normal and shear stresses. From the figure it is observed

that the maximum stresses induced is 361.782 Mpa, which is less than allowable stress.

Case 5.Combined Loading.

Table 7. The induced displacements and stresses with uniform Temperature loading of

44.450C and pressure 0.09316 MPa.

Name Results asper Analysis

Allowable stress as perASME SEC VIII DIV.2

(MPa)

Referencefigure

Displacement in X-direction,mm

1.194 7 33

Displacement in Y-direction,

mm

1.658 7 34

Displacement in Z-direction,

mm

0.8783 7 35

Shear stress in XY-plane,

MPa

16.771 157.2 36

Shear stress in YZ-plane,

MPa

81.874 157.2 37

Shear stress in XZ-plane,

MPa

39.734 157.2 38


From the table 7 it is observed that the maximum stress induced is less than allowable stresses.

Hence the design is safe as per the strength criteria. Fig 33 to Fig 35 shows the variation of maxdisplacement in X, Y and Z-direction respectively 1.194, 1.658 and 0.8783 mm. The max.

allowable displacement is 7mm. Hence the design is safe based on rigidity.


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Fig33:The Displacement in X-direction

Fig34:The Displacement in Y-direction

Fig35:The Displacement in Z-direction



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Fig37:The variation of Shear Stress in YZ-plane

Fig38:The variation of Shear Stress in XZ-plane

Fig39:The variation of Stress Intensity

Fig 36 to Fig 39 shows the variations of normal and shear stresses. From the figure it is observed

that the maximum stresses induced is 226.085 Mpa, which is less than allowable stress.

For the material SA 516 Gr 70

KSm= 157.2 MPa

Minimum yield stress = 262 MPa

Minimum tensile stress = 481 MPa


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CONCLUSIONS

The following conclusions are drawn from the present work.1. The maximum deflection induced 1.267 mm under 0.1078 MPa loads which is with in the

allowable limits i.e. < 7mm.

2.

The maximum stress induced is 263 MPa which is less than allowable limits of 524 MPa.Hence the factor of safety is 1.992.3. The maximum deflection induced 1.11 mm under 0.10135 MPa loads which is with in the

allowable limits i.e. < 7mm.4. The maximum stress induced is 245 MPa which is less than allowable limits of 524 MPa.

Hence the factor of safety is 2.138.5. The maximum deflection induced 1.72 mm under 0.157 MPa loads which is with in the

allowable limits i.e. < 7mm.6. The maximum stress induced is 381 MPa which is less than allowable limits of 524 MPa.

Hence the factor of safety is 1.375.7. The maximum deflection induced 3.004 mm under uniform temperature of 990C load

which is with in the allowable limits i.e. < 7mm.8. The maximum stress induced is 361.782 MPa which is less than allowable limits of 524MPa. Hence the factor of safety is 1.45.

9. The maximum deflection induced 1.658 mm under combined loading of 0.09316 MPaand uniform temperature of 99

0C load which is with in the allowable limits i.e. < 7mm.

10.The maximum stress induced is 226.085 MPa which is less than allowable limits of 524MPa. Hence the factor of safety is 2.318.

REFERENCES

1 Gulyani, B. B., 2000, Estimating Number of Shells in Shell and Tube Heat Exchangers: ANew Approach Based on Temperature Cross, ASME J. Heat Transfer, 122, pp. 566571.

2 Master, B. I., Chunangad,K. S., and Pushpanathan, V., 2003, Fouling Mitigation UsingHelixchanger Heat Exchangers, Proceedings of the ECI Conference on Heat ExchangerFouling and Cleaning: Fundamentals and Applica- tions, Santa Fe, NM, May 1822, pp.

317322.

3 Reppich, M., and Zagermann, S., 1995, A New Design Method for Segmentally BaffledHeat Exchangers, Compute. Chem. Eng., 19, pp. 137142.

4 Li, H. D., and Kottke, V., 1998, Effect of the Leakage on Pressure Drop and Local HeatTransfer in Shell-and Tube Heat Exchangers for Staggered Tube Arrangement, Int. J.Heat Mass Transfer, 41 2 , pp. 425433.

5 Naim, A., and Bar-Cohen, A., 1996, New Developments in Heat Exchangers, Gordon andBreach, Amsterdam, pp. 467499.

6 Van der Ploeg, H. J., and Master, B. I., 1997, A New Shell-and-Tube Option forRefineries, PTQ Autumn, pp. 9195.

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