Comparative Evaluation of Gas Side Heat Transfer Coefficient Across Finned Tubes Using Different Empirical Correlation

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Comparative Evaluation of Gas Side Heat Transfer Coefficient Across Finned Tubes Using Different Empirical Correlation

P. Aravind1, Y. Kevin2, M. Prithvilakshaya3, P. Sankar4, G. Singaravelan5

1,2,3,4UG Scholar, Department of Mechanical Engineering,Parisutham Institute of Technology and science, Thanjavur, India.

5Assistent Professor, Department of Mechanical Engineering,Parisutham Institute of Technology and science, Thanjavur, India.

AbstractThis paper presents the work undertaken in a boiler manufacturing company which produce boilers for combined power generation with Gas turbine. Heat Recovery steam Generators are widely used in cogeneration and combined cycle plants generating steam utilizing energy from gas turbine exhaust.This gas side heat transfer can be calculated in terms of heat transfer coefficient.Some local effects may be indicated in the course of the investigation.(i.e) the boundary layer thickness at the finned surface decreases with an increasing Reynolds number.In the course of parameter study heat transfer coefficient is calculated for fins, tube arrangements, type of flow.These studies, especially comparisons between measurement, results at global performance and numerical investigations of local heat transfer behaviour in a finned tubes rows, will provide further knowledge of the local thermal field and convective transport phenomena and will give a more complete understanding of the performance behaviour.

Keywords Gas turbine, Heat recovery steam generator, heat transfer coefficient, fin arrangement and flow.

  1. INTRODUCTION

    Todays modern fast growing world is talking about an important word i.e., Energy conservation due to depleting energy sources. The two options available for the above purpose are either to use non-conventional energy sources or to improve effectiveness of conventional system. Though the former has vast amount of resources , it lacks due to economics and reliability. In most of the industries, large amount of heat is wasted. These losses are significant in the Gas turbine and Diesel engine exhaust, Process industries, Fertilizers industries, cement manufacturing units, sulfuric acid manufacturing units etc. HRSG is a steam-generating unit operated by recovering the sensible heat of flue gases from sources like Gas turbine exhaust and process industries. It is essentially a cross flow heat exchanger, which capable of generating steam at required pressures and temperatures conditions.

    Increasing industrial activity world over and particularly in India in the recent years has emphasized the importance of power plants for meeting their electrical as well as heat energy needs and fast depletion of coal reserves and ever-increasing oil prices have forced Utilities/Designers to look for new

    energy sources. Energy from waste gases can be seen as an effective means of energy conservation, resulting in improved efficiency. Heat Recovery Steam Generator (HRSG) is one of the major equipments which contributes towards meeting the modern day demand of energy conservation by recovering the potential heat from the waste gases and also improves overall cycle efficiency of the plant. The sources of these waste gases are in plenty such as open cycle gas turbine power plant, diesel engine exhaust, process industries etc.

  2. LITERATURE SURVEY

    G. Caruso, A. Naviglio[1]EXPERIMENTAL INVESTIGATIONTHE PERFORMANCE OF A FINNED TUBE is given asSeveral experiments on heat transfer phenomena are carried out at the University of Rome "La Sapienza" DINCE. Theseresearches were undertaken mainly to support the development and qualification of passive cooling systems like that foreseenin the MARS nuclear reactor or in other process plants where heat has to be safely removed (as in chemical reactors whererunaway reactions could occur). This paper presents the results of an experimental analysis on the air-side heat transfercoefficient using finned tubes.A campaign of tests has been carried out to evaluate the air-side heat transfer coefficient using water in turbulent conditionsas heating medium flowing at different temperatures inside the tube. Petukhovs correlation has been selected to calculatewater heat transfer coefficient in the tube. The experimental data obtained have been compared with the Briggs & Youngscorrelation, obtaining a very good agreement in the same range of validity. The thermal contact resistance of the wrapped finson the tube has been considered in the evaluations.Thermofluidodynamic analyses of the experimental apparatus using the FLUENT code have been also performed.

    Meeta Sharma, Onkar Singh[2]Thermodynamic Evaluation of WHRB for its Optimum performance in Combined Cycle Power PlantsCombined cycle power plants are being extensively used in view of their capability of offering high specific power output and thermal efficiency for same fuel consumption compared to other thermal power plants. Therefore, the studies for optimization of different

    systems in combined cycle power plant are of great significance. Waste heat recovery boiler (WHRB) being the interface between the topping cycle and bottoming cycle becomes one of the critical components. Present study is undertaken for thermodynamic analysis of waste heat recovery boiler for design change from spiral fin type to segmented fin type in 663 MW capacity gas/steam combined cycle power plant. Results obtained for combined cycle power plant with segmented fin type WHRB have been compared with the actual plant data of combined cycle power plant with spiral fin type WHRB. The conclusions presented in the study are useful for power plant designers.

    M. R. Jafari Nasr and A. T. Zoghi[3] FULL ANALYSIS OF LOW FINNED TUBE HEAT EXCHANGERS. In this paper, first the governing parameters characterizing low-finned tubes are reviewed. Second, the more important of the available performance correlations are compared with the available experimental

    INLINE

    Fig 1. Serrated and solid fin

    SERRATED

    STAGGERED

    data. The most reliable one can be employed to develop a pressure drop relationship, which has already been used in an

    PARALLEL FLOW

    CROSS FLOW

    COUNTER FLOW

    PARALLEL FLOW

    CROSS FLOW

    COUNTER FLOW

    algorithm for exchanger sizing. Also a means for the identification of advantages of low-finned tube heat exchangers over plain tube units has been developed. It has been recognized that for low-finned tube units there are some potential benefits to place certain liquids, particularly with high viscosities, in the shell side of heat exchangers rather than the tube side. These benefits can be obtained in both reduction of surface area and the number of shells required for a given duty. They result in heat exchangers, which are more compact and are also easier to construct. The performance evaluation of low-finned units, in terms of area benefits is not discussed in this paper. However, the results of this study will complete the authors investigation for low-finned tubes heat exchangers.

    Fig 2: Flow chart of flow of flue gas

    B. Arrangements:

    There are two types of arrangements are made in the boiler used serrated tubes. They are inline and staggered.

  3. CASE STUDY

    The selected boiler manufacturing company is the leading manufacturer of boilerin India and one of largest manufacturer of boiler in Asia. The company was established in 1964 at Trichy. It is an ISO 9001: 2000 certified company and also holds a BS OHSAS 18001:2007 certification. Here the tubes used in the boiler may be of following types:

    PLAIN SERRATED SLID

    A. Serrated

    Serrated fins are mostly used in the boiler tubes because the heat transfer coefficient of the serrated fins are more than the other type of tubes.

    C. Flow types:

    PARRALEL FLOW CROSS FLOW COUNTER FLOW

    Based on the data obtained from the process, it was found that the mostly the boiler is designed for the serrated finned tubes in both inline and staggered arrangements using flue gas in cross flow.

    =

    For finding the h value we used different empirical correlations because the other parameters can easily find but heat transfer coefficient cannot find until the values are known So the calculations were done on the system to find the values based on the collaborated correlation given for the company to design the boiler.

    These correlations are based on the function of Nusselt number

    Fig 3. Combined cycle power plant.

    =

    Here Nusselt number is a function of Reynoldss number and

    prandtl number.

  4. NOMENCLATURE. Table 1: Nomenclature

    1. SOFTWARE USED

      The HRSGs Vogt Power International provides are designed applying proven standards and also specializes in the design, manufacturing and supply of Heat Recovery Steam Generators (HRSG)and aftermarket related services.

      Fin height

      hf

      M

      Fin spacing

      Sf

      M

      Fin thickness

      Tf

      M

      Tube outside diameter

      Do

      M

      Transverse tube pitch

      Xt

      M

      Longitudinal tube pitch

      Xl

      M

      Number of rows

      n

      Fin diameter

      Df

      M

      Air velocity

      v

      m/s

      Density

      kg/m3

      Viscosity

      µ

      kg/ms

      Thermal conductivity

      k

      W/Mk

      Specific heat

      cp

      J/kg-K

      Inlet temperature

      Ti

      C

      Outlet temperature

      To

      C

      Mass flow rate

      m

      kg/s

      Number of tubes

      N

      Fin pitch

      fp

      M

      Reynolds number

      Re

      Prandtl number

      Pr

      Viscosity at inlet temperature

      µTi

      Ns/m2

      Viscosity at outlet temperature

      µTo

      Ns/m2

      Overall heat transfer area

      A

      m2

      Outside tube area

      At

      m2

      Fin height

      hf

      M

      Fin spacing

      Sf

      M

      Fin thickness

      Tf

      M

      Tube outside diameter

      Do

      M

      Transverse tube pitch

      Xt

      M

      Longitudinal tube pitch

      Xl

      M

      Number of rows

      n

      Fin diameter

      Df

      M

      Air velocity

      v

      m/s

      Density

      kg/m3

      Viscosity

      µ

      kg/ms

      Thermal conductivity

      k

      W/Mk

      Specific heat

      cp

      J/kg-K

      Inlet temperature

      Ti

      C

      Outlet temperature

      To

      C

      Mass flow rate

      m

      kg/s

      Number of tubes

      N

      Fin pitch

      fp

      M

      Reynolds number

      Re

      Prandtl number

      Pr

      Viscosity at inlet temperature

      µTi

      Ns/m2

      Viscosity at outlet temperature

      µTo

      Ns/m2

      Overall heat transfer area

      A

      m2

      Outside tube area

      At

      m2

      To meet customer performance requirements they utilizes design software that incorporates the experience of more than 100 previously built units. Then, on a continuous bases, performance test measurements are compare to projected values generated by our softwares to ensure that outcomes meet expectations, long before construction begins.

      Vogt developed one of the first thermal rating and designed programs for heat recover steam generators over 30 years ago. Program was originally written in Fortran, then migrated to Wang Basic, Turbo Pascal and Microsoft DOS. Program is still in use today. Currently they have written new Microsoft Windows, Visual Basic 5 version of HRSG rating and design program.

    2. METHODOLOGY Approach to the problem:

      In order to find a suitable procedure for the analysis of the available heat transfer coefficient, a literature study was done searching for the methods other authors had used. The following are the different empirical correlations for calculating heat transfer coefficient over finned tubes bundles. Most of the heat transfer coefficient results are presented in dimensionless terms via Nu number defined by equation.

  5. PROCESS

This project implies that the need of finding the heat transfer coefficient across finned tubes using different empirical correlations because the convective heat transfer coefficient can be find using the following formula:

=

S.No

Author

Correlation

1.

BRIGGS AND YOUNG'S

1

Nud=jRedPrd 3

-0.319 gf 0.2 gf 0.11

j=0.134Red L

f f

2.

E.MARTI NEZ

Nu=0.023Re0.85 k 0.06 Pr0.33

Do

3.

RABAS ET AL

0.36 0.06 0.11

Nu=0.183Re0.73 Pr0.36

4.

HEWITT

a 0.2 s 0.18 h -0.14

Nu=0.19 Re0.62Pr0.33 b d d

5.

ZUKAUS KAS

ST 0.2 s 0.18 h -0.14

Nu=0.044 Re0.82 SL d d

6.

STASIUL EVI CIUS

a 0.2 s 0.18 h -0.14 .

Nu=0.19 Re Pr0.33 b d d

Table 2: Correlations for inline flow.

Table 3: Correlations for staggered flow.

  1. INPUTS.

    Based on the site data, inputs are given to the correlations which are countered here. Because it is essential to check the site data until it reaches the nearby value to the values taken from the software analysis.

    100.3201

    CORRELATION

    INLINE

    STAGGERED

    A.BRIGGS AND YOUNG'S

    88.49551

    107.5077

    B.E.MARTINEZ

    90.99926

    88.41932

    C.RABAS ET AL

    114.8948

    113.1444

    D.HEWITT

    99.59458

    E.ZUKAUSKAS

    106.6822

    110.2202

    F.STASIULEVICIUS

    93.33075

    102.1554

    G.RYAN'S

    99.56939

    83.80048

    H.CHATO's

    78.78613

    103.2429

    I.PETUKHOV- KIRLLOV'S

    92.7295

    100.9589

    J.WARMEATLA'S

    83.36779

    84.45049

    K.HOFMANN'S

    89.80425

    101.132

    L.PERRY'S

    112.6822

    106.7962

    M.WARMEATLA'S 2

    83.61492

    79.49252

    N.ESCOA'S

    82.02404

    O.HOLMAN'S

    46.21591

    59.56682

    P.SCHMIDT

    74.47351

    80.62627

    CORRELATION

    INLINE

    STAGGERED

    A.BRIGGS AND YOUNG'S

    88.49551

    107.5077

    B.E.MARTINEZ

    90.99926

    88.41932

    C.RABAS ET AL

    114.8948

    113.1444

    D.HEWITT

    99.59458

    100.3201

    E.ZUKAUSKAS

    106.6822

    110.2202

    F.STASIULEVICIUS

    93.33075

    102.1554

    G.RYAN'S

    99.56939

    83.80048

    H.CHATO's

    78.78613

    103.2429

    I.PETUKHOV- KIRLLOV'S

    92.7295

    100.9589

    J.WARMEATLA'S

    83.36779

    84.45049

    K.HOFMANN'S

    89.80425

    101.132

    L.PERRY'S

    112.6822

    106.7962

    M.WARMEATLA'S 2

    83.61492

    79.49252

    N.ESCOA'S

    82.02404

    O.HOLMAN'S

    46.21591

    59.56682

    P.SCHMIDT

    74.47351

    80.62627

    Table 5:Outputs

    Table 4: Inputs

  2. RESULTS AND DISCUSSION

    In this project steps were taken to improve the efficiency of the Gas Turbine using HRSG. The inputs are feed inside the Vogt software given by the collaborator and the outputs were seen. Now the heat transfer coefficient value calculated from the countered correlationsare compared with the softwares output. So the value of heat transfer coefficient across finned

    Inline :

    140

    120

    100

    80

    60

    40

    20

    0

    A B C D E F G H I J K L M N O P

    INLINE OUTPUT

    tubes taken from the software output is compared and some related values are matched. Due to this, the value which is nearly equal to the correlations are been taken and used for the company, to create a new software by their own and they develop their own boiler with the proper correlation.

    Here for the given inputs the Vogt Software has given the value forinline and staggered (i.e.)

    Table.6: correlation values vs software values

    Staggered:

    120

    100

    80

    For inline hcvalue is 62.234w/m2k.

    For staggered hcvalue is 79.3216w/m2k.

    60

    40

    20

    0

    A C E G I K M O

    STAGGERED OUTPUT

    Table 7: correlation value vs software value

  3. CONCLUSION.

The heat transfer coefficient evaluation on the gas side of serrated fin finned tube heat exchanger has been determined numerically. Using the present numerical investigation and with the given mechanical data, improved heat transfer coefficient correlations for the HRSG has been studied and provided for reference. The tubes in all bundles are of staggered arrangement or inline arrangement. The results of gas side heat transfer coefficient calculated by various correlations are graphed with software results. If the gas side heat transfer coefficient across HRSG experienced during operation is higher than the limit considered during design, it may attract penalty. Hence, for a typical HRSG designed by BHEL, the gas side heat transfer coefficient values have been predicted for HRSG using different empirical correlations as part of the project work will be useful for refining the gas side heat transfer coefficient calculations based on the site feedback. Therefore, this exercise of taking all these correlations into consideration and comparing it with the field data will be helpful for formulating suitable design strategy towards accurate prediction of gas side heat transfer coefficient across HRSG and optimized overall cost and plant performance.

REFERENCE

[1]. G. Caruso, A. Naviglio, EXPERIMENTAL INVESTIGATION ON THE PERFORMANCE OF A FINNED TUBE XXII

CongressoNazionalesullaTrasmissione del Calore, Genova 2004; pg.2- 6.

[2]. Meetasharma,Onkarsingh IOSR Journal of Engineering (IOSRJEN)www.iosrjen.org ISSN : 2250-3021.Thermodynamic Evaluation of WHRB for its Optimum performance in Combined Cycle Power Plants

[3].S. P. Kearney and A. M. Jacobi fromLocal and Average Heat Transfer and Pressure Drop Characteristics of Annularly Finned Tube Heat Exchangers.

[4].NaserSahiti(Erlangen, 2006) Thermal and Fluid Dynamic Performance of Pin Fin Heat Transfer Surfaces.

  1. MiSandar Mon from Numerical Investigation of Air-Side Heat Transfer and Pressure Drop in Circular Finned-Tube Heat Exchangers

  2. Dr. Ali HussainTarrad Journal of Engineering and Development, Vol. 12, No. 3, September (2008) from A Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation; Pg 15-20.

  3. M. R. Jafari Nasr and A. T. Zoghi (August 11, 2003) from FULL ANALYSIS OF LOW FINNED TUBE HEAT EXCHANGERS,Pg.no:5-10.

  4. PiotrWaisfrom Fin-Tube Heat Exchanger Optimization pg.no:18-25. [9]Bert de LEEUW1, Harry HAGENS2, Steven BRAND3, Mart

GROOTEN4, Frank GANZEVLES5, Cees van der GELD6, Erik van KEMENADE7 from GENERATOR COOLING USING HEAT

PIPES onConference on Modelling Fluid Flow (CMFF06) The 13th International Conference on Fluid Flow Technologies Budapest, Hungary, September 6-9, 2006.

[10]N. Sahiti, F. Durst *, A. Dewan from Heat transfer enhancement by pin elements inLSTM-Erlangen, Institute of Fluid Mechanics, Friedrich- Alexander-Universita¨ t Erlangen-Nu¨ rnberg, Cauerstrasse 4, D-91058 Erlangen, Germany

  1. Marie-Noëlle Dumont, Georges Heyen from Mathematical modelling and design of an advanced once-through heat recovery steam generator in LASSC, University of Liège, SartTilman B6A, B-4000 Liège, Belgium.

  2. Hamid Nabati from OPTIMAL PIN FIN HEAT EXCHANGER SURFACE in 2008.

  3. T. H. Lee LG Electronics Comparison Of Air-Side Heat Transfer Coefficients Of Several Types of Evaporators Of Household Freezer/Refrigerators

  4. Creed Taylor from MEASUREMENT OF FINNED-TUBE HEAT EXCHANGER PERFORMANCE inGeorgia Institute of Technology December 2004.

  5. Abdullah H. AlEssa and Mohammed Q. Al-Odat* from

    ENHANCEMENT OF NATURAL CONVECTION HEAT TRANSFER FROM A FIN BY TRIANGULAR PERFORATIONS OF BASES PARALLEL AND TOWARD ITS BASE in Al-Balqa Applied

    University, Al-Huson University College Al-Huson, Irbid, Jordan,

  6. RYAN JEFFREY AVENALL from USE OF METALLIC FOAMS FOR HEAT TRANSFER ENHANCEMENT IN THE COOLING JACKET OF A ROCKET PROPULSION ELEMENT in A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY O FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2004.

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