chart of shell sidew heat transfer coeff

8/3/2019 Chart of Shell Sidew Heat Transfer Coeff

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A new chart method for evaluating single-phase shell side

heat transfer coefficient in a single segmental shell and

tube heat exchanger

Zahid H. Ayub *

Isotherm, Inc., 7401 Commercial Blvd. East, Arlington, TX 76001, United States

Received 26 February 2004; accepted 14 December 2004

Available online 23 February 2005

Abstract

This paper presents a simple but accurate method to calculate shell side heat transfer coefficient in a sin-

gle segmental shell and tube heat exchanger. The method is based on a chart which is a product of actual

data taken over a span of several years. The calculation procedure is presented with a case study. Theresults are compared with known methods and commercial/proprietary computer codes prevalent in the

industry. The results from this method compare well with HTRI computer program. This method can

prove to be a helpful tool for design engineers in the field.

2005 Elsevier Ltd. All rights reserved.

Keywords: Shell and tube exchanger; Single phase; Heat transfer coefficient

1. Introduction

Shell side heat transfer analysis has been the subject of discussion since the late forties. It hasundergone through various phases with addition of intricate complexity. With the advent of the

1359-4311/$ - see front matter 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.applthermaleng.2004.12.015

* Tel.: +1 817 472 9922; fax: +1 817 472 5878.

E-mail address: [email protected]

URL: www.iso-therm.com

www.elsevier.com/locate/apthermeng

Applied Thermal Engineering 25 (2005) 24122420
mailto:[email protected]://www.iso-therm.com/http://www.iso-therm.com/mailto:[email protected]


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power of computer, the complex calculation procedures have been adequately addressed. How-ever, it is important to produce a simple but an accurate procedure that can be used by practicingengineers in the field with greater reliability.

In 1949 Donohue [1] presented a simple shell side heat transfer approach without consideringleakage and by-pass effects. A similar procedure was also presented by Kern [2]. Due to lack of

availability of statistical data, Donohue and Kern had proposed using de-rating factors forby-pass effects. Obviously, this approach was not considered accurate enough since in some cases

it resulted in unrealistic sizes. This observation was affirmed by Palen and Taborek [3] comparingresults from Donohue and Kern to experimental data developed by an industry sponsored orga-

nization, Heat Transfer Research Institute (HTRI).It is important to provide essential but reliable tools to practicing and design engineers. A

simple design tool that an engineer can use gives greater insight into the subject matter rather thanfeeding data into a computer code written by someone else. The designer can observe first hand

the effect of change in a variable due to a change in another variable. For example if a baffle cut ischanged with other parameters fixed, the effect on the size or the rating could be clearly observed.This paper is intended to address this issue. A new method is proposed to calculate single-phase

shell side heat transfer coefficient for a typical single segmental shell and tube heat exchanger. Inthis paper a calculation method based on a chart is presented. Numerous correlations are con-

densed in a chart form to make it more users friendly.

2. Background: shell side single-phase flow

In a typical shell and tube heat exchanger, two fluids exchange heat while being separated fromeach other. One fluid is on the shell side and another on the tube side. To understand the mechan-ical and construction details there is an unlimited supply of information in the form of books, arti-

cles, papers and more recently, the internet. Therefore, this aspect of the exchanger will not beaddressed in this paper. A typical shell and tube heat exchanger is shown in Fig. 1 with its majorcomponents.

Nomenclature

cp liquid specific heat (Btu/lb F)d tube outside diameter (in.)D shell inside diameter (in.)h heat transfer coefficient (Btu/h ft2 F)k liquid thermal conductivity (Btu/h ft F)Lc baffle cut (in.) (Fig. 4)V shell side velocity (ft/s)l dynamic viscosity (centipoises)l0 dynamic viscosity at exit temperature (centipoises)q fluid density (lb/ft3)

Z.H. Ayub / Applied Thermal Engineering 25 (2005) 24122420 2413


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There are essentially two models that address the flow on the shell side. The ideal flow and real

flow models. The calculation procedures provided by Donohue [1] and Kern [2] were based onideal flow model as shown in Fig. 2. This type of flow can only exist in a heat exchanger if it ismanufactured with the following mechanical features:

(a) Each baffle is welded to the shell inside diameter at the contact line so that there is no pos-sibility of leakage between the shell and the baffle.

(b) The annular space between the tube and the baffle hole is either mechanically closed or abushing is inserted to eliminate any fluid leak across the clearance between the baffle holeand the tube.

(c) The tube bundle layout is such that there are no lands and extra spaces for ribs and impinge-ment plates. The outer tube limit (OTL) almost touches the inner diameter of the shell.

Front

Head

Baffle

Shell

Tie-rod Tube

Rear

Head

Fig. 1. Shell and tube heat exchanger.

Fig. 2. Ideal shell side flow.

2414 Z.H. Ayub / Applied Thermal Engineering 25 (2005) 24122420


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It is obvious that the above features are cost prohibitive and therefore not practical. Because of

constructional constraints almost all practical heat exchangers have gaps between baffle to shelland tube to baffle. By-pass occurs through these gaps and a portion of the shell side fluid passes

across the bundle cross-section.Tinker [4] presented an elaborate model based on the concept of stream analysis in which the

flow through the bundle was assumed to be divided into various flow paths as shown in Fig. 3.

Tinker named these stream paths as A, B, C, and E. Later stream F was added to the group. Thisstream designation has become an industry standard.

Stream A is the leakage between the baffle holes and the tubes. Its effect is not too drastic since

this fraction of the total flow is still in contact with the tube surface. Stream B is the flow across thetube bundle between two adjacent baffles. The goal of a good design is to maximize this flow.Stream C is the leakage between the outer tube limit (OTL) and the shell inside diameter. Due

to partial contact with tube surface, this stream also contributes to the heat transfer. One simple

approach to reduce this leakage is to install longitudinal sealing strips between the OTL and shellat the plane of the baffle cut. Stream E is the leakage in the annular section formed between the shellinside diameter and the baffle diameter. This stream is undesirable due to lack of contribution to

the heat transfer between the two fluids. Stream F is the leakage within the bundle in the sectionswhere there are no tubes in order to accommodate tube side ribs or shell side impingement plates.Since a part of this stream is still in contact with a portion of tubes there is still some contribution to

the heat transfer. A simple way to avoid this is to install dummy tubes or rods in the tube bundle.Tinker [4] has provided a procedure to evaluate these individual flow fractions and hence cal-

culate the shell side heat transfer coefficient. The concept sounds good but due to lack of actual

data, it was merely a guess work and involved tedious calculations that could only be performedwith the computers. This probably prompted Tinker [5] to present a simplified method in 1958that became the foundation for further simplified methods presented by Devore [6] and Fraaz

and Ozisik [7].The results of extensive study by Palen and Taborek [3] with large data bank from exchangers

were utilized to develop a proprietary iterative stream analysis method more or less in line with the

basic concept of Tinker.

C C

C C

CC

B

B B

B

F

B

C

B

B

C

C A

A

E

E E

Fig. 3. Various shell side flow paths in a real exchanger.



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In view of the computational complexities of Tinker method, Bell [8] carried out a detailed shell

side experimental and analytical work at the University of Delaware. The fundamental principlewas the same as presented by Tinker, but the computational approach was simpler. This method

is also known as Delaware Method [9]. The flow fractions are presented as a function of fractionalflow areas available to individual streams. The ideal flow heat transfer coefficient is then adjusted

with several correction factors.

3. The new chart method for shell side coefficient

All the previous methods mentioned require elaborate and tedious calculation procedures. Theauthor has collected vast data in his 17 years of direct involvement in the design, fabrication and

installation of shell and tube heat exchangers. Also, having access to data collected over a period

of 20 years by a now defunct shell and tube manufacturing company, therefore, resulting in adatabase that spreads over a span of 37 years.

This data could be presented in the form of numerous correlations for specific Reynolds num-ber and baffle cut range. This would obviously result in too many correlations making the job

even more tedious for a field or design engineer. In fact it would go against the spirit of this paper.Therefore, to maintain the accuracy and still keep the calculation procedure simple, a chart hasbeen devised to calculate the shell side heat transfer correlation. The statistical error is less than5%. This chart could be used with greater accuracy for a straight or U-tube bundle with single

segmental baffles shell and tube heat exchangers. If need arises the detailed correlations could bepresented in a future paper.

This method is time tested and shows promising results when applied correctly. The reason forthis accuracy is that all the flow conditions assumed in the Tinker and Delaware method are incor-

porated into this particular method for the data is a product of actual heat exchangers on the teststands and/or in the field. Every exchanger was designed in a conventional manner with shell, seg-

mental baffles, tie-rods, spacers, tube sheets and tubes. They were all designed per standard pro-cedures with clearances between tube to baffle hole and baffle to shell inside diameter. The tubebundles were for full fixed tube sheet bundles with spread out OTL or floating tube sheet config-uration with smaller OTL. The bundles were also single pass or multiple passes on the tube side.

Hence, the correction for stream F is incorporated in the design procedure. The chart is shown inFig. 4.

The chart shows curves for different single segmental baffle cuts. The baffle cut ( Lc/D) varies 20

50%. This is a practical range and covers almost all exchangers manufactured in the industry. Inorder to use the chart the following factors and parameters have to be evaluated first.

(a) Parameter Fz. This is a dimensional number. The reason for its dimensional nature is thatthe individual parameters within the equation are presented in daily-use units, so that the engi-

neers do not have to convert units, but rather follow a straight plug-in procedure.

Fz qdV=l 1

where q is shell side fluid density in lb/ft3; d is tube outside diameter in in.; V is shell side velocityin ft/s; l is bulk viscosity in centipoises.



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(b) Factor Fs. This is the shell side geometry factor and incorporates baffle cut, baffle arrange-

ment, and flow intensity effects.(c) Factor Fp. Factor Fp is the pitch factor. The value ofFp depends upon the tube layout of thebundle.

Fp = 1.00 for triangular and diagonal square pitch (Fig. 5)

= 0.85 for in-line square pitch (Fig. 5).

(d) Factor FL. This is called the leakage factor. It incorporates all the stream leakages and is a

function of bundle configuration, i.e., straight tube, U-tube or floating bundle. Typical values fordifferent configurations are:

p

p

p

p

30 rotatedtriangle

60 triangle squarerotatedsquare

Fig. 5. Different tube pitch layouts.

BAFFLE CUT

BAFFLE CUT%

L

D

c

cL

Lc

D

15

20

30

40

50

60

70 80

90100

200

300

400

500

600700

800900

1000

2000

3000

4000

5000

60007000

Fz

sF

.02

.03

.04

.05

.06

.07

.08.

09 .

1.

2 .3

.4

.5

.6

.7

.8

.9

1

2 3 4

56

7

8

910

20

30

4 0 5

06

0

70

80

90

100

200

300

400 5

00

600

700

800

900

10

00

0.3

0.350.4

0.2

0.5

0.25

D

Fig. 4. Chart for calculating shell side heat transfer coefficient.



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FL = 0.90 for straight tube bundle

= 0.85 U-tube bundle= 0.80 for floating bundle

It is important to note that for exchangers with unusually high leakage or flow by-pass a lower

value of FL be used. This would be a matter of individual judgment and design decision.The shell side heat transfer coefficient is then given as:

h FsFpFLk2=3cpl

1=3l=l00:14=d 2

To find the bundle velocity in Eq. (1) it is recommended to follow the following procedure.

(a) Select the initial shell diameter (D), tube diameter (d), and tube pitch (p).(b) Select a baffle cut (Lc/D) and evaluate the window area available to fluid flow. Equate this

area to the area at the mid-section of the bundle and calculate the minimum space betweenthe two adjacent baffles. It is a good practice to keep the magnitude of the cross-flow and thewindow area the same.

(c) Based upon this area evaluate the velocity at the mid-section of the bundle (cross-flow) byusing continuity equation.

4. Comparison and results

To compare the results from this method to other available methods a rating calculation was

performed on an arbitrary liquid-to-liquid heat exchanger with 12.7500 outer diameter, schedule40 pipe and 9600 nominal tube length with water on both shell side and tube side. All other geo-metric parameters were kept the same for each calculation run as shown in Table 1. The other

three methods selected for the case study were (a) Delaware, (b) HTRI, and (c) B-JAC. The HTRIand B-JAC software are available to members only. Water was selected as a working medium to

keep least amount of discrepancy in the thermodynamic and transport properties. The results areshown in Table 2.

It is interesting to note that the cross-flow Reynolds number for the present method and HTRI

results are within 9% of each other and Delaware almost similar to HTRI. However, B-JACresults are 34% and 29% less than present method and HTRI, respectively. This lower value in

Reynolds number on part of B-JAC does not fit well when we compare the shell side velocities.The B-JAC velocity is only 6% less than HTRI whereas the Reynolds number is 29% less as shownabove. A possible explanation for this anomalous behavior could be attributed to the tube con-figuration especially at the mid-section of the bundle in the B-JAC program. The shell side heat

transfer coefficients for each of the methods is shown in Table 2. HTRI and present method re-sults are almost identical. B-JAC is 15% over and Delaware is 24% under this method and HTRI.

Moreover, B-JACs higher coefficient with lowest Reynolds number could be inherent to the pro-gram. One reason could be higher contribution of stream B (48%) versus 40.4% for HTRI. Table 2also shows the overall heat transfer coefficients for the clean, dirty, and service conditions. Since

this study is a case of rating and not design, it is important to look at the Uservice values for all four



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methods. It is obvious that this method, HTRI, and B-JAC results are similar, whereas, Delaware

shows 55% over-surface which not only results in extra cost, but also more space, too. The Ucleanvalues show that B-JAC and HTRI results are similar while this method is 5% and Delaware is 9%

less than B-JAC. This is obviously a function of tube side thermal resistance which in turn is afunction of the choice of correlation used to evaluate the internal heat transfer coefficient.

5. Conclusion

A new chart method is presented to calculate single-phase shell side heat transfer coefficient in

a typical TEMA style single segmental shell and tube heat exchanger. A case study of rating

Table 1

Input data for rating

Heat load (Btu/h) 2,000,000

Shell side inlet temperature (F) 150Shell side out temperature (F) 70

Tube side inlet temperature (F) 120

Tube side outlet temperature (F) 100

Shell side flow (lb/h) 100,000

Tube side flow (lb/h) 100,000

Shell side fouling factor (h ft2 F/Btu) 0.0005

Tube side fouling factor (h ft2 F/Btu) 0.0005

Shell inside diameter (in.) 12.09

Tube outside diameter (in.) 0.75

Tube wall (in.) 0.049

Tube pitch (in.) 0.9375

Tube pattern 30 triangular

No of tubes 100

Tube side passes 2

Baffle cut (%) 30 H

Baffle spacing (in.) 4.0

Baffle thickness (in.) 0.125

Material All carbon steel

Table 2

Output data

Present method Delaware HTRI (ST-5) B-JAC (HETRAN)

Shell side Reynolds no. 26024 24206 23912 17101

Shell side cross-flow area (in.2) 12.36 12.10

B Stream (%) 40.4 48

Shell side velocity (ft/s) 5.19 4.62 3.61 3.40

Shell side HTC (Btu/h ft2 F) 1314 1000 1321 1522

Uclean (Btu/h ft2F) 484 463 501 508

Udirty (Btu/h ft2F) 316 309 326 329

Uservice (Btu/h ft2F) 269 417 270 266



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water-to-water exchanger is shown to indicate the result from this method with the more estab-

lished procedures and softwares available in the market. The results show that this new methodis reliable and comparable to the most widely known HTRI software. However, it is easy to incor-

porate it as a simple but accurate design tool that can be beneficial for the design engineers in thefield.

References

[1] D.A. Donohue, Heat transfer and pressure drop in heat exchangers, Ind. Eng. Chem. 41 (11) (1949) 499511.

[2] D.Q. Kern, Process Heat Transfer, McGraw-Hill, 1950.

[3] J.W. Palen, J. Taborek, Solution of shell side flow pressure drop and heat transfer by stream analysis method,

Chem. Eng. Prog. Symp. Ser. 65 (92) (1969).

[4] T. Tinker, Shell side characteristics of shell and tube heat exchangers, parts I, II and III, general discussion of heat

transfer, in: Proc. Inst. Mech. Eng., London, 1951.[5] T. Tinker, Shell side characteristics of shell and tube heat exchangers: a simplified rating system for commercial heat

exchangers, J. Heat Transfer 80 (1958) 3652.

[6] A. Devore, Use nomograms to speed exchanger calculations, Hydrocarbon Process. Pet. Refiner 41 (12) (1962) 101

106.

[7] A.P. Fraaz, M.N. Ozisik, Heat Exchanger Design, Wiley & Sons, 1965.

[8] K.J. Bell, Final Report of the Cooperative Research Program on shell-and-tube heat exchangers, University of

Delaware Eng. Exp. Sta. Bulletin 5, 1963.

[9] Wolverine Company, Engineering Data Book II, 1984.


chart of shell sidew heat transfer coeff

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