An Educational Computer-Aided Tool for Heat Exchanger Design F. L. TAN,1 S. C. FOK2 1
School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 2
Department of Mechanical Engineering, The Petroleum Institute in Abu Dhabi, Abu Dhabi, United Arab Emirates
Received 5 November 2004; accepted 18 November 2005
ABSTRACT: This paper presents the development of an educational computer-aided design tool for the shell and tube heat exchanger. The software integrates the thermohydraulics analysis based on Kern method with the mechanical design based on Tubular Exchanger Manufacturing Association (TEMA) Class ‘‘C’’ standard. The software allows the user to experiment with different design specifications and visualize the solutions in the form of performance data and engineering drawings. Technical drawings on the parts of the heat exchanger, like the shell, tube, front and rear header, tube sheet and baffle plate, are produced by the software to assist the user in appreciating issues relating to practical fabrication and costing. Through the correlation of the thermo-hydraulic performance, configurations and dimensions with respect to the technical specifications, it is hoped that the user could better appreciate the fundamentals of heat exchanger design. ß 2006 Wiley Periodicals, Inc. Comput Appl Eng Educ 14: 7789, 2006; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20073
INTRODUCTION Heat exchangers are found in a wide variety of applications in the aeronautical, process, chemical, power, and electronics industries. They can be classified based on the flow arrangements and construction [1]. The parallel flow, center flow, and cross flow are the three basic flow arrangements. Figure 1 shows a shell and tube heat exchanger, one of
Correspondence to F. L. Tan (
[email protected]) ß 2006 Wiley Periodicals Inc.
the most commonly used heat exchangers. A shell and tube heat exchanger consists of two primary parts, the shell and tube, along with other secondary components including the inlet and outlet nozzles, the baffle plates, tube sheets, tie rods, guiding plates, and sealing strip. Due to the wide applications of heat exchangers in industries, courses in the thermal design and analysis of these systems can be found in many engineering schools. The main motivation of these courses is on the rating and sizing of the system components [2] to meet the design thermal specifications. Rating concerns the evaluation of the 77
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Figure 1 Shell and tube heat exchanger.
thermo-hydraulics performance given the geometrical dimensions of the heat exchanger. Sizing determines the exchanger configuration given the specifications including temperatures, fluid, flow rates, pressure drop, etc. This focus is critical as an oversized exchanger can lead to unnecessary and excessive power consumption, while an undersized system may not produce the thermal requirements. The conventional process of rating and sizing the components in a heat exchanger involves tedious and lengthy routine calculations that are not only time consuming but also highly prone to human error. Furthermore, an iterative procedure would often have to be adopted to investigate different possible configurations. To facilitate the development process and minimize the problems as a result of human errors, heat exchangers in industries are increasingly designed and analyzed using computer-aided design tools [35]. Many of these commercially available programs had included the heat exchanger design standards from American Society of Mechanical Engineers (ASME) and Tabular Exchangers Manufacturers Association (TEMA). The industrial trend of using computer-aided tools has compelled many universities to develop and introduce computer software in courses for the design and optimization of heat exchangers [6,7]. The objective of using software in the education of heat exchanger designs is not only to reinforce the student understanding of the underlying principles of exchanger design, but also to allow students to bridge the gap between theoretical consideration and engineering practice. For example, the heat exchanger simulator (HES) [6] is developed for the training of chemical engineers, the emphasis of which is in the analysis of the real industrial heat exchanger problems. HES allows students to concentrate on the analysis of the solutions with respect to the practical problem but this might not necessarily give students additional insight into the fundamental theories. On the other hand, the Shell and Tube Heat Exchanger Design Software (STHEDS) [7] is an educational tool that caters for the
thermo-hydraulic design and flow-induced vibration analysis of the shell and tube heat exchangers. STHEDS allows students to better understand the fundamentals in heat exchanger design but lacks the mechanical design capabilities to enable students to appreciate practical engineering considerations. In industries, the thermal and hydraulic analysis of heat exchangers cannot be viewed as a stand-alone process. The analysis must be integrated with other development activities, including manufacturing, costing, system life cycle support, etc. Otherwise, there is the danger that the design is difficult to manufacture, requires high-production cost, or contains flaws that production engineers have to correct or send back for redesign. This paper describes an educational computeraided design tool for heat exchanger that integrates thermo-hydraulics analysis with mechanical design. This software focuses on the shell and tube heat exchanger and aims to complement the theories behind the thermo-hydraulics design analysis with practical mechanical design details required for costing and production. Program Description and Development Consideration section gives an overall description of the development consideration. Program Implementation section covers the program implementation. The verification of the program is discussed in Validation With Benchmark Problem section. Conclusions and future work can be found in Conclusion section.
PROGRAM DESCRIPTION AND DEVELOPMENT CONSIDERATION The heat exchanger mechanical design software is developed to educate users in heat exchanger design. The aim is to allow users not only to better understand the fundamentals associated with heat exchanger designs through thermo-hydraulic analysis, but also to appreciate the fabrication, costing, and maintenance aspects through evaluation of the detailed
COMPUTER-AIDED TOOL FOR HEAT EXCHANGER DESIGN
mechanical drawings. The program is designed to cater for both students and novice engineer to heat exchanger design. The program is developed in Java [8], a programming language syntactically based on C and Cþþ. Java is not a procedural programming language. It adopted an object-orientated programming approach and the code can be reused through inheritance without sacrificing the functionality of already implemented systems. This feature would facilitate future expansion of the software. Figure 2 shows the flowchart of the logic behind the software development. As in practical situations, the thermohydraulics analysis should be initiated after the user has input and selected the key parameters of the heat exchanger requirements. Following the rating, the results of the analysis and the input requirements should be displayed for the user evaluation. The user can modify the parameters until a satisfactory design that meets the specifications (e.g., pressure drop) is obtained. This process will allow the users to reinforce their understanding of the fundamentals by relating
the outcomes with input parameters. Once a satisfactory design is obtained, the user can generate the detailed mechanical drawings for the shell, tube layout, headers, tube-sheets, and baffle plates. These details will allow the user to further investigate various issues associated with fabrication, costing and maintenance. As an educational tool, the program must be user friendly. GUI provides the key to making the program easy to learn and simple to use. Figure 3 shows the framework of the program structure. The program structure allows the user the free choice of access to whichever part of the program through menu bar, which currently contains five main menus: design, analysis, drawing, file and help. In the software development, human-computer interaction has been considered in the menu development. The number of keystrokes required for user input has been kept to a minimum. This will minimize the number of errors and mistakes. Figure 4 shows the Design Menu, which is automatically initiated at the start of program for the
SELECTION, INPUT DATA & REQUIREMENT OF HE DESIGN PARAMETER
MODIFICATION OF DESIGN PARAMETER
RATING OF THE DESIGN THRU’ THERMAL & HYDRULIC ANALYSIS
EVALUATE THE DESIGN BY THERMAL, HYDRAULIC & DIMENSION CONSTRAINT
ACCEPTABLE
UNACCEPTABLE
GENERATING HE COMPONENT DRAWINGS
PRINT OUT
Figure 2
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Design logic of heat exchanger design software.
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PROGRAM Main Menu
HELP
FILE
DESIGN
ANALYSIS
DRAWINGS
DATA ENTRIES
THERMAL DESIGN HYDRAULIC DESIGN
SHELL TUBE/TUBE SHEET BAFFLE PLATE FRONT HEADER REAR HEADER FULL ASSEMBLY
Figure 3 Program menu of heat exchanger design software.
user to input and select key design parameters. These include the type of exchanger, tube/shell profile, fluids used, and temperature requirements. Some parameters like mass flow rate and fluid inlet and outlet
Figure 4
temperature require user input. If this type of input field is accidentally left blank, an error message will be generated to prompt the user for input. Other parameters like exchanger type can be selected by the
Design menu.
COMPUTER-AIDED TOOL FOR HEAT EXCHANGER DESIGN
user. For these selections, default values will be used if these are not specified by the user. Some parameters like fluid density and fluid-specific heat are selfgenerated when the type of fluid used is selected. The Analysis menu contains two sub-menus: thermal design and hydraulic design. Figure 5 shows the results of a typical thermal design analysis. It gives both the shell and tube fluid properties as well as the tube profile. Figure 6 shows the results of a typical hydraulic design analysis. It gives the calculated result of fluid-related properties and vital information on the pressure drop for both the shell-side fluid and the tube-side fluid. A warning message is generated by the software to advise the user to resize the heat exchanger if the calculated pressure drop exceeded that of the specified allowable pressure drop. The Drawing Menu contains sub-menus to generate the drawings and dimension details for the shell, tube/tube sheet, baffle plate, front header, rear header, and the fully assemble heat exchanger. When a sub-menu is selected, the drawing of the selected component will be displayed together with a pop-up screen showing the dimensions (Fig. 7). Dimension pop-up can be hidden by clicking ‘‘X’’ and be recalled by clicking on the show button as shown in Figure 8.
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The File Menu contains sub-menus for New, Open, Save, and Exit: these are standard administration facilities in Widows based software. These allow designs to be saved in ‘‘.he’’ format for later recall using the ‘‘OPEN’’ sub-menu. The Help Menu contains standard tutorial facilities to guide the user not only on the use of the software but also on the design of the shell and tube heat exchanger. This facility will further aid the user understanding on the fundamentals and practice of heat exchanger design.
PROGRAM IMPLEMENTATION Many methods of designing heat exchanger have been developed in the past 50 years. The Kern method is used in this work for the thermo-hydraulic design analysis. The following sub-sections give the details of the thermal analysis, hydraulic analysis, and the fundamentals relationships in the mechanical design.
Thermal Analysis Heat exchangers enable exchanges of thermal energy among two or more fluids at different temperatures.
Figure 5 Thermal Analysis menu.
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Figure 6
Figure 7
Hydraulic Analysis menu.
Drawing with dimension pop-up screen.
COMPUTER-AIDED TOOL FOR HEAT EXCHANGER DESIGN
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Figure 8 Drawing without dimension pop-up screen.
Thermal analysis of a heat exchanger is based on the conservation of energy. Ideally, q the heat released by the hot fluid should equal the heat gain by the cold fluid: m_ c ðCpc ÞðTci Tco Þ ¼ UAFDTm
ð1Þ
m_ h ðCph ÞðThi Tho Þ ¼ UAFDTm
ð2Þ
where the subscripts ‘‘c’’ refers to cold, ‘‘h’’ refers to hot, ‘‘i’’ refers to inlet, and ‘‘o’’ refers to outlet conditions. Let DT1 be the temperature difference of the two fluids at one end of the heat exchanger and DT2 be the temperature difference of the two fluids at the other end of the heat exchanger. Using the log mean temperature difference (LMTD) approximation DTm ¼
DT1 DT2 lnðDT1 =DT2 Þ
ð3Þ
the average overall heat transfer coefficient and the heat transfer area that governs the size of the heat exchanger can be determined as 1 U¼ d o 1 do do lnðdo =di Þ 1 ð4Þ þ Rfi þ þ Rfo þ 2km ho di hi di
The LMTD correction factor F, which varies with the type of shell, the number of shell pass and the number of tube pass, can be obtained from charts in the TEMA standard handbook. The heat transfer coefficient for inside flow is given by
hi ¼
Nu k di
ð5Þ
The Nusselt number Nu is determined using empirical correlation based on the flow conditions governed by the Reynolds number. The heat transfer coefficient for outside flow, ho can be calculated using 0:14 0:36k ho ¼ ðRes Þ0:55 ðPrÞ1=3 b ð6Þ De w where Res ¼
Gs De
ð7Þ
Pr ¼
Cp k
ð8Þ
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The shell-side mass velocity Gs is given by Gs ¼
m_ As
ð9Þ
where As , the bundle cross flow area at the center of the shell, is given as Ds CB As ¼ PT
ð10Þ
and C, the clearance between adjacent tubes, is defined as C ¼ P T do
ð11Þ
The equivalent diameter of the shell, De, is dependent on the layout of the tube sheet. Generally for any pitch layout, De can be assumed to be four times the net flow area (as layout on the tube sheet) divided by the wetted area. The tube layout is characterized by the included angle between tubes, such as 308, 458, 608, and 908. For a square pitch layout, the equivalent diameter is given by ððP2T pdo2 4Þ De ¼ 4 ð12Þ pdo For a triangular pitch layout, the equivalent diameter is given by h pffiffiffi i 4 P2T 3=4 pðdo Þ2 =8 ð13Þ De ¼ ðpdo =2Þ
Hydraulic Analysis The hydraulic analysis consists of the determination of shell side and tube side pressure drop. The pressure drop on the shell side is calculated using the following expression: Dps ¼ f
Ds ðNB þ 1ÞG2s 2rs De Fs
ð14Þ
0:14 where Fs ¼ b =w . The number of baffles NB can be calculated by NB ¼ L=B. Note that (NB þ 1) is the number of times the shell fluid passes the tube bundle. The friction factor f can be determined from f ¼ expð0:576 0:19 ln Res Þ
ð15Þ
for 400 < Res ¼ Gs De 1 106. s The pressure drop Dpi at tube side can be calculated using LNp U2 ð16Þ Dpt ¼ 4f þ 4Np t m di 2
Equation (16) has taken into the account the sudden expansion and contraction the tube fluid experiences. For the laminar flow, Re ¼ Ummdi t < 4; 000 f ¼
16 Re
ð17Þ
For the turbulent flow, Re ¼ 4000 < Umdi t < 100; 000 f ¼ 0:079Re0:25
ð18Þ
Mechanical Design The design of mechanical components of shell and tube heat exchanger is based on TEMA standard [9]. The main components considered here are tubes, shells, the front and rear headers, the tube sheets and the baffle plates. The design and assembly of the heat exchanger involving all these components is important for cost and energy reasons. The shell basically houses the tubes and allows the fluids to flow over the tubes for heat exchanging. The shell types have been standardized by TEMA and types E, F, and X are considered in the software. The categorizing of shell type is very much dependent of the position of the inlet and outlet shell nozzle. In this development the shell length L is set up as a constraint for determining the number of tubes and the shell outer diameter Do, which is expressed as Do ¼ Ds þ 2Ts
ð19Þ
The value of Ts can be obtained from TEMA standards and Ds can be found using #1=2 rffiffiffiffiffiffiffiffiffi" CL Ao ðPRÞ2 do Ds ¼ 0:637 ð20Þ CTP L The tube layout constant CL changes accordingly to the tube pitch layout. For square pitch layout (458 and 908), CL ¼ 1.0 and for triangular pitch layout (308 and 608), CL ¼ 8.7. The tube count constant CTP depends on the number of tube passes. For one tube pass, CTP ¼ 0.93 and for two tube passes, CTP ¼ 0.9. The tube pitch ratio PR can be found from PR ¼ PT =do ð21Þ The shell side fluid is discharged into the tube bundle through a nozzle. If the flow velocity through the nozzle exceeds a certain limit, the tubes can vibrate. The minimum inside shell nozzle diameter Dns (mm) [10] to avoid this phenomenon is given by sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi m_ s Dns ¼ ð22Þ ðp=4Þs Vns
COMPUTER-AIDED TOOL FOR HEAT EXCHANGER DESIGN
where Vns max, the maximum nozzle shell velocity, is calculated by sffiffiffiffiffiffiffiffiffiffiffiffi 2; 250 Vns max ¼ ð23Þ s The assembly of the heat exchanger is made possible by bolting the shell flanges to the headers’ flanges. The flange width shown in Figure 9 is dependent on the size of bolting used. The flange width fw is approximately expressed as three times the bolting edge distance [9]: fw ¼ 3ð1:5dB Þ
normally welded to the shell as shown in Figure 10. The floating tube sheet is designed to cater for thermal expansion. Figure 10 shows the tube length definitions. Lto is the nominal tube length for all bundle types except the U tubes. Lti is the length of summation of all baffles spacing. To determine Lti the tube sheet thickness Lts must be known. Lts can be estimated as Lts ¼ 0:1 Ds
ð26Þ
Lti can be calculated as Lti ¼ Lto 2Lts
ð24Þ
ð27Þ
Figure 11 shows the tube sheet definition. The upper tube limit, Dot1 is defined as
The flange outer diameter can be calculated by DF ¼ Do þ 2fw þ 0:004
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ð25Þ
In Equation (25), a clearance of 4 mm (0.004 m) is added to allow for the flange to slip over the shell. The tube contains the tube fluid, which enters from the front header and exit via the rear header. The tubes are laid out according to TEMA standard as discussed in the thermal analysis. The software allows the user to choose between one-tube pass and twotube passes. This selection will not only affect the LMTD correction factor used in the calculation of heat transfer rate but also the physical construction of the heat exchanger. The physical construction of the heat exchanger also changes with different selection of tube passes, which can be described based on the location of inlet and outlet nozzle on the front and rear header. The tube sheets are used to hold the tubes at the ends. A tube sheet is generally a round plate which has grooves for gaskets; bolt holes for flanging to the shell and the channel; as well as holes for the desired tube layout pattern and tie rods. A fixed tube sheet is
Dot1 ¼ Ds Lbb
ð28Þ
where Lbb is the inside shell diameter-to-tube bundle bypass clearance (diametral), which is related to shell inner diameter Ds [11]. The lower limit Dct1 is defined as Dct1 ¼ Dot1 do
ð29Þ
Baffles are plates designed to support the tubes for structural rigidity, preventing tube vibration and sagging. It also helps to divert the flow across the bundle to obtain a higher heat transfer coefficient. They may be classified as transverse and longitudinal types. Figure 12 shows single segmental transverse type baffles. The number of baffle plate, NB can be calculated as NB ¼ IntegerðLti =Lbc 1Þ
ð30Þ
where NB must be an integer value. Front and rear headers are used respectively as the entrance and exit for the tube fluid. The front header is usually stationary while the rear header
Figure 9 Flanges.
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Tube sheet
Region of Central Baffle, Lbc Spacing, Lbc
Lbo
Shell
Lts
Lti=Lta
Lts
Lbmax
Lbi
Lto
A
Lbmax B2
B1
Figure 10 Shell and tube sheet.
Figure 12 Baffles.
could be either stationary or floating depending on the thermal stresses between the tube and shell. In some rear header a provision has been made to take care of the tube thermal expansion. In this development, front header can be of types A, B, and C; and rear header can be of types L, M, P, S, and W. The header outer diameter is similar to the shell outer diameter. Header wall thickness is taken to be similar to the shell thickness. The cover thickness, Tc, as recommended by TEMA is !4 " G Tc ¼ 5:7P 5:706 103 100 ð31Þ !#13 2hG 0:198 AB G pffiffiffiffiffi þ 103 100 dB where the gasket mean diameter G is given by G ¼ DF 4hG
ð32Þ
otl
ctl
s
do
Figure 11 Tube sheet definition.
VALIDATION WITH BENCHMARK PROBLEM Benchmark problems serve to ensure that the values obtained from the developed software are correct and accurate. The following is one such benchmark problem used to valid the software: Water enters the copper tubes at mass flow rate of 2.5 kg/s. The water inlet and outlet temperature is 158C and 858C, respectively. Water is used to cool shell side fluid ethylene glycol and its inlet temperature is 1608C. Ethylene glycol is delivered at a mass flow rate of 5.19 kg/s. The shell shall be limited to 2 m in length. The tube outer diameter is 0.012 7 m with tube thickness of 0.001651 m. The tubes layout pitch and angle are 0.024 m and 608C, respectively. This benchmark problem was obtained from the heat transfer textbook by Incropera and deWitt [1]. The thermal and hydraulic analyses of the benchmark problem together with the standard results are tabulated in Tables 1 and 2, respectively. The software has also been tested using other benchmark problems and the results obtained show good correlations with the benchmark solutions. The current version of the software is not able to automatically generate an optimized solution to the design of the shell-and-tube heat exchanger based on the given technical specifications of the heat exchanger. The user has to modify the input values to achieve a suitable design. That will require a sound understanding of the theory of heat exchanger. Thus, the software is more suitable for the educational use as a computer-aided tool to design the heat exchanger. The software provides suitable technical drawings for the practical understanding of the heat exchanger design. The software can be further expanded to handle TEMA Class ‘‘B’’ and Class ‘‘R’’ type heat exchangers, and other TEMA heat exchanger
COMPUTER-AIDED TOOL FOR HEAT EXCHANGER DESIGN
Table 1
Comparison of Computed Thermal Design Results With Benchmark Solution
Item
Symbol
1 2 3 4 5 6 7 Table 2
Tho q LMTD U At Ntt Lt
87
Description
Software solution
Benchmark solution
Error (%)
Thermal design Shell outlet temperature (8C) Heat transfer rate (W) Log mean temperature difference (8C) Overall heat transfer coefficient (W/m2K) Total tube surface area (m2) Total number of tubes Total length of tubes (m)
99.79 742,872.7 79.9 447.22 20.51 257 514
99.79 731,850 79.9 445.73 20.57 257 514
0 1.5 0 0.3 0 0 0
Software solution
Benchmark solution
Error (%)
129.9 0.00105 990 0.0373 0.42 3,728.95 0.37287 262.76
129.9 0.00105 990 0.0373 0.42 3,729.3 0.3728 257.0
0 0 0 0 0 0 0 2.2
50 0.000653 1,000 0.59997 0.0082 8,632.81 1,975.59
50 0.000653 1,000 0.59997 0.0082 8.634.8 1,974.7
0 0 0 0 0 0.03 0.05
Comparison of Computed Hydraulic Design Results With Benchmark Solution
Item
Symbol
1 2 3 4 5 6 7 8
Tmh De Ds Re f Dps
1 2 3 4 5 6 7
Tmc Um f Re Dpt
Description Shell side Shell fluid mean temperature (8C) Shell fluid absolute viscosity (Ns/m2) Shell fluid density (kg/m3) Equivalent shell diameter (m) Inner shell diameter (m) Reynolds number Friction factor Calculated pressure drop (N/m2) Tube side Tube fluid mean temperature (8C) Tube fluid absolute viscosity (Ns/m2) Tube fluid density (kg/m3) Mean velocity (m/s) Friction factor Reynolds number Calculated pressure drop (N/m2)
configuration. Cost estimation of the heat exchanger [12] and the generation of the bill of materials (BOM) will be included in future work.
CONCLUSION A software has been developed and validated for the thermo-hydraulic and mechanical design of the shell and tube heat exchangers. The development is based on the Kern method for the thermal and hydraulic design analyses. The mechanical design is based on the TEMA standards. The implementation has also taken basic human-computer interaction issues into consideration. The friendly GUI allows the user to input parameters and select exchanger configurations with ease. By allowing the user to experiment and correlate the solutions to different design requirements, the software could assist the user to better understand the fundamentals of the thermo-hydraulic design analysis. Furthermore, the program can automatically generate technical drawings showing the dimensions of the designed heat exchanger. The
student could use these mechanical drawings for costing and production planning. This would help the student to better appreciate the practical aspects of heat exchanger design and development. Future work would involve further development of the software to include costing of the heat exchanger.
ACKNOWLEDGMENTS The authors acknowledge the work of Nanyang Technological University undergraduate student, P. K. Lim, for his contribution in the software development.
NOMENCLATURE
A AB As Ao Bc
heat transfer surface area (m2) bolt cross-sectional area (m2) crossflow area at or near shell centerline, (m2) outside heat transfer surface area (m2) baffle cut (%)
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C Cpc Cph CL CTP Dc Dctl De DF Ds Dns Dotl Dts dB do di F f fw G Gs hG hi ho km ks kt L Lbmax Lbb Lbc Lbc,total Lbi Lbo Lta Lti Lto Lts c h
NB Np Nt Ntt Nu nB P
clearance tube side specific heat (J/kg K) shell side specific heat (J/kg K) tube layout constant tube count calculation constant cover diameter (m) diameter through center of tube (m) shell Equivalent diameter (m) flange diameter (m) inside diameter (m) nozzle diameter (m) outer tube limit (m) tubesheet outside diameter (m) bolt diameter (m) tube outside diameter (m) tube inside diameter (m) LMTD correction factor Fanning friction factor flange width (m) gasket mean diameter (m) shell side mass flow rate (kg/sm2) radial distance between mean gasket diameter and bolt circle (m) inside tube heat transfer coefficient (W/m2K) outside tube heat transfer coefficient (W/m2K) thermal conductivity of tube material (W/ mK) shell fluid thermal conductivity (W/mK) tube fluid thermal conductivity (W/mK) shell length or maximum tube length per pass (m) maximum unsupported tube span (m) diametral shell to tube bypass clearance (m) central baffle spacing (m) total unsupported tube span (m) inlet baffle spacing (m) outlet baffle spacing (m) effective tube length for heat transfer area (m2) baffled tube length (m) overall nominal tube length (m) tubesheet thickness (m) tube fluid mass flow rate (kg/s) shell fluid mass flow rate (kg/s) number of baffle number of tube pass number of tube per pass total number of tube Nusselt number number of bolt design pressure (Pa)
PR Pr PTtube q Re Res Rfi Rfo Tb Tc Tci Tco Thi Tho Ts U Um Vns Dps Dpt DTm DT1 DT2 mb
mw m rs rt
tube pitch ratio Prandtl number layout pitch heat transfer rate (W) Reynolds number shell fluid Reynolds number inside tube surface fouling resistance outside tube surface fouling resistance baffle plate thickness (m) cover thickness (m) tube fluid inlet temperature (8C) tube fluid outlet temperature (8C) shell fluid inlet temperature (8C) shell fluid outlet temperature (8C) shell thickness (m) overall heat transfer coefficient (W/m2K) mean velocity (m/s) nozzle velocity (m/s) shell side pressure drop (Pa) tube side pressure drop (Pa) log mean temperature difference (K) temperature difference of inflow fluid (K) temperature difference of inflow fluid (K) dynamic viscosity at bulk temperature (Ns/ m 2) dynamic viscosity at wall temperature (Ns/ m 2) dynamic viscosity (Ns/m2) shell fluid density (kg/m3) tube fluid density (kg/m3)
REFERENCES [1] F. P. Incropera and D. P. DeWitt, Fundamental of heat and mass transfer, 4th ed., Wiley, New York, 1996. [2] S. Kakac and H. Liu, Heat exchangers—Selection, rating, and thermal design, CRC Press, Boca Rato, FL, 1999. [3] D. N. Paliwal, A. Rakheja, A. Malik, and M. Chouhan, A program for the design of a heat exchanger as per TEMA standards, Int J Press Vessels Piping 57 (1994), 111129. [4] R. Mukherjee, Effectively design shell-and-tube heat exchangers, Chem Eng Prog 94 (1998), 2137. [5] T. A. Kara and O. Guraras, A computer program for designing of shell-and-tube heat exchangers, Appl Therm Eng 24 (2004), 17971805. [6] L. M. F. Lona, F. A. N. Fernandes, M. C. Roque, and S. Rodrigues, Developing an educational software for heat exchangers and heat exchanger networks projects, Comput Chem Eng 24 (2000), 12471251. [7] K. C. Leong and K. C. Koh, Shell and tube heat exchanger design software for education applications, Int J Eng Educ 14 (1998), 217224.
COMPUTER-AIDED TOOL FOR HEAT EXCHANGER DESIGN
[8] R. Cadenhead, SAMS teach yourself Java 2 in 24 hours, 2nd ed., Sams Publishing, USA, 2001. [9] V. J. Stachura, Standards of the tubular exchanger manufacturers association, 7th ed., Tubular Exchanger Manufacturers Association, USA, 1988. [10] E. A. D. Saunders, Shell and tube heat exchangers: Elements of construction, hemisphere handbook of heat exchanger design, Vol. 4, Hemisphere New York, 1990.
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[11] J. Taborek, Shell and tube heat exchangers: Single-phase flow, hemisphere handbook of heat exchanger design, Vol. 3, Hemisphere, New York, 1990. [12] M. C. Roque and L. M. F. Lona, The economics of the detailed design of heat exchanger networks using the Bell Delaware method, Comput Chem Eng 24 (2000), 13491353.
BIOGRAPHIES Fock-Lai Tan was born in Singapore in 1959. He received his BEng degree in mechanical engineering from the National University of Singapore in 1984 and his MSME degree in mechanical engineering from Rensselaer Polytechnic Institute, Troy, New York, in 1992. He is currently an associate professor at the School of Mechanical and Aerospace Engineering in Nanyang Technological University, Singapore. His primary research interest is in the area of thermal management using phase change material. He has been actively involved in the development of multimedia courseware for university teaching and mobile learning.
Sai-Cheong Fok received the BASc degree in engineering from University of Ottawa, Canada, in 1985 and his PhD in mechanical engineering from Monash University, Australia, in 1990. He has worked as an engineer in the aircraft industry. He is currently an associate professor in the Department of Mechanical Engineering at The Petroleum Institute in Abu Dhabi. His current research interests are in virtual prototyping, machine learning, and computer-aided learning.
