chevron - shell andtube exchanger design and selection

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400 Shell and Tube Exchanger Design and Selection

AbstractThis section contains information on TEMA nomenclature, selecting the most economic exchanger configuration for a defined service, allocating the streamsshell or tube side, specifying appropriate mechanical components, defining bafflayout, deciding if a small predesigned exchanger is appropriate, and estimatinsize and cost of shell and tube exchangers.

Contents Page

410 TEMA (Tubular Exchanger Manufacturers Assoc.) Nomenclature 400-2

420 General Design Considerations 400-2

430 Stream Placement 400-11

440 Pass Arrangements and Multiple Shells 400-12

450 Bundle and Tubesheet Arrangements 400-13

451 Front Head Design

452 Fixed Tubesheets

453 U-tubes Versus Floating Rear Heads

454 TEMA F Shell

460 Shell Side Baffle and End Spaces 400-14

470 Small Exchangers 400-15

480 Estimating Methods 400-16

481 Step by Step Procedure

482 Surface Area Calculations

483 Tube Count and Number of Tube Passes

484 Shell Diameter

485 Exchanger Investment Cost

Chevron Corporation 400-1 December 1989

400 Shell and Tube Exchanger Design and Selection Heat Exchanger and Cooling Tower Manual

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410 TEMA (Tubular Exchanger Manufacturers Assoc.) NomenclatureThe Tubular Exchanger Manufacturers Association (TEMA) has developed nomclature for describing shell and tube heat exchangers. It includes a simple codedesignating the size and type of the exchanger. In addition, standard terminologhas been set up to specify typical parts and connections.

TEMA size is the shell inside diameter in inches rounded to the nearest integerfollowed by the straight length of the tubes in inches rounded to the nearest inteThe two dimensions are separated by a hyphen (-).

For kettle reboilers, the port diameter in inches precedes the shell inside diameThe two dimensions are separated by a slash (/). Port diameter is the size of thopening the bundle slides through.

TEMA type consists of three letters describing the stationary or front end head,shell, and rear head, in that order. The letter designations are shown on Figure 400-1.

For example, a 20-foot straight length U-tube bundle, 3-foot shell diameter, withsingle shell pass and removable shell cover would be a TEMA SIZE 36-240 TYAEU. The same bundle installed in a 5-foot diameter kettle reboiler would be a TEMA SIZE 36/60-240 TYPE AKU.

Standard terminology to describe components and connections of shell and tubexchangers is provided in Figure 400-2.

TEMA sets mechanical standards for three classes of exchangers reflecting theseverity of the service. For most refinery services, the most restrictive class is used—TEMA Class R. For other services (chemical plants for example), TEMAClass C or B exchangers are used. In general, Class R exchangers have thickeshells, larger and thicker heads, thicker tubes, and larger miscellaneous parts. TEMA requirements are noted where appropriate throughout this manual.

420 General Design ConsiderationsSingle- and two-phase exchangers and most condensers have very similar contions. The typical layout is summarized in the following list and shown in Figure400-3 and 400-4. (Steam generators (2 types), reboilers, and condensers are described in Sections 340, 350, 360 and 370.)

The typical shell and tube exchanger geometry includes the following items:

• TEMA E shell style

• U-tubes for rear head type with full support plate at tangent

• TEMA A-type front head

• Single segmental baffles with cut of 18 to 25% of shell I.D. and with cut oriented vertically

• Baffle spacing of 20 to 100% of shell I.D

December 1989 400-2 Chevron Corporation

Heat Exchanger and Cooling Tower Manual 400 Shell and Tube Exchanger Design and Selection

Fig. 400-1 Heat Exchanger Nomenclature (TEMA, Figure N-1.2) (Courtesy of TEMA)



Fig. 400-2 Heat Exchanger Components (1 of 3) (TEMA, Table N-2 and Figure N-2) (Courtesy of TEMA)

1. Stationary Head—Channel

2. Stationary Head—Bonnet

3. Stationary Head Flange—Channel or Bonnet

4. Channel Cover

5. Stationary Head Nozzle

6. Stationary Tubesheet

7. Tubes

8. Shell

9. Shell Cover

10. Shell Flange—Stationary Head End

11. Shell Flange—Read Head End

12. Shell Nozzle

13. Shell Cover Flange

14. Expansion Joint

15. Floating Tubesheet

16. Floating Head Cover

17. Floating Head Flange

18. Floating Head Backing Device

19. Split Shear Ring

20. Slip-on Backing Flange

21. Floating Head Cover—External

22. Floating Tubesheet Skirt

23. Packing Box

24. Packing

25. Packing Gland

26. Lantern Ring

27. Tierods and Spacers

28. Transverse Baffles or Support Plates

29. Impingement Plate

30. Longitudinal Baffle

31. Pass Partition

32. Vent Connection

33. Drain Connection

34. Instrument Connection

35. Support Saddle

36. Lifting Lug

37. Support Bracket

38. Weir

39. Liquid Level Connection


Heat Exchanger and Cooling Tower M

anual400 Shell and Tube Exchanger Design and Selection

Chevron Corporation400-7

December 1989

F
ig. 400-3 Typical Longitudinal Section Shell and Tube Exchanger


Fig. 400-4 Typical Cross Section, Shell and Tube Exchanger



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• 3/4-inch O.D., 14 BWG (average) thickness (0.584 inch I.D.) carbon steel t

• Tube length variable with one or two tube passes depending on service

• 45 degree rotated square layout with tube pitch = 1.25 × tube O.D. for liquid and two-phase hydroprocessing shell side service

• 90 degree square layout with tube pitch = 1.25 × tube O.D. for boiling, condensing, and single-phase gas shell side service

• Two or more pairs of sealing strips (bars)

• Dummy tubes in pass partition lane when two tube passes

• Two rows of impingement rods at inlet nozzle when warranted

Overall Exchanger ConfigurationThe Company preference is a TEMA AEU exchanger for most services. U-tubeare the cheapest rear head type that allows for thermal expansion of the tubes.TEMA A type front head has a removable channel cover. This allows for inspecand cleaning of the tube side without pulling spool pieces in the piping.

Shell Side Nozzle PlacementSingle inlet and outlet shell side nozzles are normally located at opposite ends the exchanger with one on the top and one on the bottom of the shell. This arrament allows vents and drains to be located in piping.

Route two-phase flow based on the following rule: “Heat up and cool down.” Thmeans hot fluid being condensed should enter on the top and exit on the bottomthe exchanger. Likewise, cold fluid being boiled should enter on the bottom andexit on the top. The “Heat up and cool down” rule does not apply to single-phasflow.

Transverse and Support BafflesThe normal configuration for the tube side consists of U-tubes with a full suppoplate at the tangent. This is shown in Figure 400-3. The plate blocks flow over tU-bends. Otherwise, the bends must be supported to protect against vibration.

For baffles, use single segmental baffles with a cut of around 18 to 25% of the sI.D. for most efficient conversion of pressure drop to heat transfer. The baffle cushould be vertical for best drainage of the shell side at shutdown. Baffle thickneset by TEMA.

Baffle spacing should be 20 to 50% of the shell I.D. It is usually set to maintain good heat transfer (economic pressure gradient or shear controlled flow regimeGuidelines for economic exchanger velocity and pressure drop are provided in Section 220 of this manual. In some cases (particularly for gas and two-phase fshell side), additional supports may be required to prevent vibration. See Section 260 of this manual for more information.



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Tube SelectionTubes are normally 3/4-inch outside diameter, 14 BWG (minimum) thickness (0inch inside diameter), and made of carbon steel. Length is limited by the plot spfor pulling the bundle and standard bundle pulling equipment. TEMA has name10, 12, 16 and 20 feet as standard tube lengths. Other lengths are possible.

Alloy tubes are appropriate for some services. The cost of upgrading to alloy tushould always be weighed against possible process adjustments to permit carbsteel construction. Section 800 of this manual discusses materials selection fordifferent services.

Tubepass LayoutMost exchangers should be limited to one or two tube passes. Using U-tubes wtwo passes is best and cheapest, however some services dictate 1 pass with aexpensive rear head (vertical thermosiphon reboilers or crude/overhead condenfor example).

Tube PitchFor liquid and two-phase services, use 1-inch, 45 degree rotated square pitch. promotes mixing. Use 1-inch, 90 degree square pitch for boiling, condensing, asingle-phase gas on the shell side. For boiling, the vertically oriented lanes promcirculation. For condensing and single-phase gas, in-line tubes minimize pressudrop without sacrificing heat transfer. Both 45 and 90 degree pitch provide 0.25inch inspection and cleaning lanes through the bundle.

Preventing Shell Side Flow BypassingSingle- and two-phase exchangers with impingement protection typically includtwo pairs of sealing strips (bars). The bars block the leakage stream flowing arothe baffles between the bundle and shell (“C” stream shown in Figure 200-3 in Section 213). For vertical cut baffles, the bars straddle the nozzles (located at ttop and bottom of the bundle). Note that the bars on the bottom act as skid barsbundle removal.

For an exchanger with two tube passes, the single pass partition lane runs perpular to the baffle cuts. Dummy tubes are positioned in the pass partition lane toblock flow bypassing (“F” stream shown in Figure 200-3 in Section 213). Dummtubes are spaced four to six tube rows apart between baffle cuts and are the sadiameter as the tubes.

Impingement ProtectionWhen impingement protection is warranted, the preferred method is to install twrows of rods (typically tubes over solid rods) adjacent to the inlet nozzle. Section 524 contains design details and applications of impingement rods alongwith descriptions of other types of impingement protection.

Tolerances and ClearancesAll tolerances and clearances are TEMA.



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430 Stream PlacementAllocating the streams to the shell or tube side is determined by weighing factowhich sometimes conflict. These factors include stream temperature, pressure,tive flowrate, viscosity, corrosiveness, relative heat transfer film coefficient, and pressure drop limitations. Guidelines for allocating the streams to the shell or tuside are given in Figure 400-5.

Fig. 400-5 Allocating the Streams for Shell and Tube Heat Exchangers

In Order of Decreasing Priority:

Stream Property Compared to Other Stream

Preferred Side

Reasons for This ChoiceShell Tube

Match Coefficients and Pumping Power

— — Minimize cost

Lower Film Coefficient Expected (hshell / htube <0.3)

X Enhance outside surface to raise limiting side coefficient (single-phase gas only)

Condensing — — Determined by coolant

Treated Cooling Tower Water X Corrosion inhibitors effective tube-side; otherwise use alloy tubes

Viscosity above 2 cP X Staggered tube layout induces good heat transfer at low Reynold’s number

Alloy Required for Corrosion X Allows cheaper shellside compo-nents

Very Low System Pressure or ∆P Available

X Can use J or X shell style to shorten flow path and reduce pres-sure drop

High System Pressure X Reduces shell thickness; however, tube rupture design sometimes controls

High ∆T across one Bundle (Over 200°F)

X Excessive ∆T in stationary tubesheet if placed on tubeside

Normal Fouling — — Does not matter

Deposits Too Hard to Hydroblast (Rare)

X Use floating rear head for straight tubes

Complete Tube Plugging (Rare) X Use floating rear head for straight tubes



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440 Pass Arrangements and Multiple ShellsThe appropriate stream pass arrangements for a particular service are based o

• Providing economic pressure gradient on both sides of exchanger• Operating in shear controlled flow regime for two-phase flow• Limiting pressure drop• Controlling temperature efficiency

On the tube side, the pressure gradient is adjusted by changing the number of per pass. To get more area, increase the flow path length either by using longetubes, by adding more shells in series, or by increasing the number of tube pas

Note that two tube passes are typical because more passes dramatically increapressure drop. Not only does the pressure drop increase proportionally to the increase in flow path length, but to the square of velocity. For example, going frtwo to four passes increases the pressure drop by a factor of eight with the tubecount held constant.

On the shell side, the pressure gradient is adjusted by changing the baffle spacTo get more area, the exchanger (tube length) is made longer. When more areaneeded and the tube length is maximum, add another shell with the shell side fin series.

The shell style is changed from a TEMA E-type to a TEMA J- or X- type when tresulting pressure drop is too large at the target pressure gradient. This shortenflow path allowing the pressure gradient to be maintained.

Use parallel exchangers only when a single exchanger is too large, and the predrops can not be increased at the target pressure gradients. Exchanger size is limited by the manufacturer’s fabricating equipment and the user’s maintenanceequipment. Space availability may also limit size, especially when modifying anexisting unit.

Parallel units with isolation valves have been used to provide an installed sparewhen flow rates will vary more than 50% from normal. When the flow rate variethe number of units onstream is changed to maintain reasonable operating predrop.

Consider using a mixed parallel/series arrangement of shell and tube passes inmultiple units only when required to meet pressure drop restrictions. The overatemperature efficiency of the units is reduced. Note that the F-factor described Section 211 of this manual is the common measure of temperature efficiency.

Temperature efficiency will vary with service. Area is most effectively used wheshell and tube side stream routing approaches pure countercurrent flow (F-fact1.0). Going to multiple units in series increases the temperature efficiency. KeeF-factor above approximately 0.85.

When performance is limited by a temperature pinch between the streams (smalocal temperature difference reflected as low F-factor), multiple shells become c



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effective by reducing the total area requirement. Countercurrent flow of both fluthrough the shells maximizes efficiency.

For condensing services, significant subcooling loads are usually processed in separate exchanger following the condenser. This allows the geometry to be changed to accommodate the much lower volumetric rate of the liquid. As a resthe area needed for subcooling is reduced.

450 Bundle and Tubesheet ArrangementsThis section covers front head selection, fixed tubesheet applications, U-tubes versus floating rear heads, and TEMA F shells (two shell pass exchangers).

451 Front Head DesignThe TEMA Type A front stationary head is normally used. It has a removal chancover so the tube side can be inspected without disconnecting nozzles or remopipe spools. The bonnet channel (Type B) is cheaper and is appropriate for smexchangers with small easily removed pipe spools. For operating pressures abo1000 psig, a special front head is required. Options are discussed in Section 53

452 Fixed TubesheetsFixed tubesheets are the cheapest type of head. They are typically used when shell side service is nonfouling and noncorrosive, and the metal temperature ofshell and tubes operate within 50°F (including startup, shutdown and steam outconditions). The bundle is not removable.

The shell side is not accessible for inspection or mechanical cleaning since thetubesheets are seal welded to the shell. If the temperature difference is larger t50°F, an expansion joint may be required in the shell.

Steam generators with very high (1000°F and above) process side temperaturewater on the shell side must have fixed tubesheets. See Section 350 of this mafor more information.

453 U-tubes Versus Floating Rear HeadsU-tube and floating head bundles are removable. Both permit thermal expansiothe tubes. The various types of rear heads are shown on Figure 400-1.

U-tubes (TEMA Type U) are the cheapest of the two types and are preferred. Tbends can be mechanically cleaned by hydroblasting for typical fouling depositsas long as complete plugging does not occur.

One disadvantage of U-tube bundles is that corrosion is difficult to monitor. Speimen tubes can only be taken from the outside perimeter of the bundle.

TEMA Type S and T floating rear heads cost more than U-tubes. Maintenance complicated by the added bundle flange. Floating heads can be taken apart an



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straight tubes drilled out. Floating heads are recommended for services leavingdeposits too hard to hydroblast.

The differences between the S- and T-type heads are minor. The split ring (S) tallows for tight clearance between the shell and bundle. However, a shell body flange and the split ring flange must be taken apart before the bundle can be puThe pull through (T) type allows the bundle to be removed prior to taking apart floating head and does not require a shell body flange. However, the shell is ovsized to allow the floating head to pass through.

Floating heads (versus fixed tubesheets) are usually necessary for single tube exchangers to accommodate thermal expansion. Head design must account fostartup, shutdown, and steam out conditions. Single pass exchangers with a flohead are commonly used for atmospheric column overhead condensers in crudunits and vertical thermosiphon reboilers.

454 TEMA F ShellThe TEMA F shell has a longitudinal baffle running through the middle of the exchanger. This provides two shell passes within one shell. Both the inlet and oshell side nozzles are located adjacent to the tubesheet (channel end).

When coupled with two tube passes, the F shell provides pure countercurrent fF shells have been used instead of multiple shells in series to avoid temperaturpinches. F shells are cheaper than multiple shells in series. However, experiencshown the seal between the two shell passes to be very difficult to maintain. Increased maintenance time and performance loss due to leakage by the longidinal baffle is reported frequently.

As a result, TEMA F shells are currently recommended for noncorroding and nonfouling services only—where the tube bundle is rarely if ever pulled for mainnance.

If the bundle from a F shell is pulled, the seal (described in Section 523) is usuareplaced. The bundle must be handled carefully when reinstalled. The seal is eruined if the slings twist the seal or the bundle goes in crooked.

460 Shell Side Baffle and End SpacesThe number of crosspasses, the baffle spacing (central, inlet and outlet spacingand the straight tube length are related mathematically. For a TEMA E shell wittubes fully supported at the bend tangent, the following relationship applies.

F = C (cp - 2) + D + E + tbst(Eq. 400-1)

where:F = Straight (total) tube length in inches

C = Central baffle spacing in inches



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cp = Number of crosspasses per shellpass

D = Inlet baffle spacing in inches

E = Outlet baffle spacing in inches

tbst = Tubesheet thickness in inches

End (inlet and outlet) spaces are set to keep the transverse baffles clear of the and outlet nozzles. The spacing accounts for mechanical constraints which forcnozzle position. These include flange thickness, body and nozzle flange clearanozzle reinforcement and access. For a TEMA E shell with U-tubes, end spacebe estimated using the following equations.

End space at channel or tubesheet in inches:

1.1 (nozzle I.D., inches) + 0.1 (shell I.D., inches) + 8.0

End space at rear end or free end of bundle in inches:

1.1 (nozzle I.D., inches) + 2.0

The actual spacing can be wider, but should not be excessive. Heat transfer in end spaces is not as good as between transverse baffles.

470 Small ExchangersThere are two types of small exchangers: the double pipe and the multitube haBoth are predesigned in set configurations, and provided by vendors off the sheThey are designed to be stacked nozzle to nozzle as shown in Figure 400-6.

Figure 400-7 is diagram of a double pipe exchanger. It is simply a single pipe within a pipe. Fluid flow on the shell side simplifies to flow through an annulus.

Fig. 400-6 Typical Stack of Small Exchangers



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Figure 400-8 is a diagram of a multitube hairpin exchanger. It is a shell and tubexchanger with one U-shell and one U-tube pass. Figure 400-9 gives typical exchanger geometries.

The same economic considerations for setting pressure gradient or velocity appsmall exchangers as to conventional shell and tube exchangers. Small exchangare cost effective when the required surface area is less than about 250 ft2 for double pipes and less than 1000 ft2 for multitube hairpins.

Because the configuration is already fixed, you should confirm exchanger geomwith the vendor. The HTRI programs can be used to model double pipe and mutube hairpin exchangers. See the Heat Exchanger Design Program User’s Guiddetails.

480 Estimating MethodsThis section gives procedures for estimating the size and cost of a shell and tubexchanger. The procedures are recommended for:

• Preliminary sizing and layout of a new exchanger prior to rigorous computemodeling

• Developing project economics

• Comparing performance or configuration of an existing exchanger to a definstandard or baseline exchanger

Fig. 400-7 Double Pipe Exchanger Fig. 400-8 Multitube Hairpin Exchanger


Heat Exchanger and Cooling Tower M

anual400 Shell and Tube Exchanger Design and Selection

Chevron Corporation400-17

Decem

ber 1989

F
ig. 400-9 Multitube Hairpin Exchanger Information (1 of 2)

400 Shell and Tube Exchanger Design and SelectionHeat Exchanger and Cooling Tow

er Manual

Decem

ber 1989400-18

Chevron Corporation

Fig. 400-9 Multitube Hairpin Exchanger Information (2 of 2)


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481 Step by Step Procedure

482 Surface Area CalculationsArea (A) for heat transfer is calculated from the overall heat transfer expressionthe service.

(Eq. 400-2)

where:A = Surface area for heat transfer, ft2

Q = Heat duty for service, Btu/hr

MTD = Mean temperature difference for service, °F

U = Overall service heat transfer coefficient, Btu/hr⋅°F⋅ft2

Step 1. Estimate physical and thermal properties for streams. Calculate exchanger duty (MMBtu/hr). Allocate streams to shell and tube sides using the guidelines in Section 430.

Step 2. Plot heat release curve for stream(s) undergoing phase change. Estmating techniques must be carefully applied to streams with dramaticslope changes. More information and an example are provided in Section 211.

Step 3. Estimate the actual mean temperature difference (MTD). This depenon the service of the exchanger. See Section 211.

Step 4. Determine if multiple shells in series are required. See Section 440.

Step 5. Select appropriate film coefficients from Figure 400-10. Appropriate sections of this manual that contain more accurate methods are referenced in Figure 400-10.

Step 6. Calculate a overall service heat transfer coefficient U. See Section 2

Step 7. Calculate the required surface area for the service. See Section 482

Step 8. Determine the number of tubes per shell and pass configuration. SeSection 483.

Step 9. Estimate the shell diameter for given tube count. See Section 484.

Step 10. Estimate shell and tube side pressure drop, if needed. See Section 2

Step 11. Cost the exchanger, if needed. See Section 485.

AQ

U MTD⋅----------------------=



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483 Tube Count and Number of Tube PassesThe number and length of the tubes is determined through trial and error. The tare related by the necessary mechanical configuration of the exchanger to provthe surface area (A) calculated in Section 482.

(1) This table applies to well designed exchangers (fouling is controlled and flow regime is shear controlled or turbulent to promote heat transfer).

(2) The film coefficients are on a clean basis. Allowance for extra area is applied separately.(3) Cooling tower water film coefficient includes thermal resistance of corrosion inhibitor film.(4) Subcooling coefficient applies for condensate cooling in the condenser. Typically subcooling is accomplished in a separate conden-

sate cooler.(5) Tubes are finned.

A = (#tubes) (L) (π) (O.D.) / 12(Eq. 400-3)

where:#tubes = Number of tubes per pass, dimensionless

= Mt / [(ρt) (Vt) (3600) (At)]

At = Cross sectional area of single tube, ft2

Fig. 400-10 Approximate Heat Transfer Film Coefficients for a Well Designed Heat Exchanger(1) (2)

Service or Fluid

Shell or Tube Side Coefficient,Btu/hr⋅°F⋅ft2 [based on bare

outside area] Reference

SENSIBLE

Pure WaterC.T. Water(3)

HC, 0.5 cPHC, 2 cPHC, 10 cP

1400450400250150

Figure 200-4Section 213

GASES

Light HC, 150 psigAir, 10 psigAir, 300 psig

1001560

Appendix B

CONDENSING

SteamLight HCHeavy HC Subcooling(4)

100020010050

Section 370

BOILING

WaterLight HCHeavy HC

1000300150

Section 360

AIR COOLED (FIN FAN)

Air Side(5) 175 Section 600



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= (π) (I.D./12)2/4

L = Flow path length, ft (in heat transfer)

π = 3.142

O.D. = Tube outside diameter, inches

I.D. = Tube inside diameter, inches

Mt = Mass flow rate of tube side fluid, lb/hr

ρt = Fluid density of tube side fluid, lb/ft3

Vt = Velocity of tube side fluid, ft/sec

For single-phase, two-phase, and some condensing services, use the economisizing guidelines (Section 220) to select velocity (Vt), or a range of reasonable velocities. Use an initial flow path length of 40 feet. This assumes a 20-foot longtube exchanger with two tube passes and a full support plate at the bend tange

Through trial and error calculations, determine a tube count that meets the areavelocity requirements. The flow path length may change. Consider leaving the fpath at 40 feet, and ending up with more excess area. Be careful when specifyiexchangers with other than two tube passes. Be careful of a long flow path. Thepressure drop can be excessive.

Note that multiple tube pass exchangers have an even number of tube passes accommodate thermal expansion.

If tube side fluid is pure component condensing or boiling, velocity can generallbe ignored. Set tube length and calculate tube count for area. For vertical thermphons (VTSR) with tube side boiling, 8- to 12-foot tubes are typical with only ontube pass. The actual length depends on the service as well as velocity and exflow regime. Further definition is beyond the scope of this section.

484 Shell DiameterFor a typical U-tube exchanger with two tube passes, 0.75-inch tubes on a 1-inrotated square (45 degree) pitch and impingement rods, the shell diameter in inis given by:

Shell I.D. = 1.95 [#tubes]0.433 (for shell I.D. between 15 and 51 inches)(Eq. 400-4)

Shell diameter should be rounded to the nearest 1/16 inch. The correlation is bon shell side nozzle diameters between 20 to 30% of the shell inside diameter. Within the constraints, the correlation is good to plus or minus 2%. If nozzles arrelatively smaller, the tubes may fit into a smaller shell. And, if nozzles are largelarger shell may be required to accommodate all the tubes.



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485 Exchanger Investment CostExchanger investment cost is calculated using techniques from the Company CEstimating Books. For shell and tube heat exchangers with design pressure be600 psi for both sides, the installed cost is:

HEX = (EDMI/655) (I) (T) [ (MTL) (A) + CMP (F + m A) ](Eq. 400-5)

where:HEX = Installed cost of exchanger, $

EDMI = Chevron material index, dimensionless

I = Installation factor for heat exchanger, dimensionless

T = Multiplier for geographic location adjustment, sales and other taxes, dimensionless

MTL = Tube material adjustment, $/ft2 (at 655 EDMI)

A = Area for heat transfer, ft2 (Note that installed cost is directly proportional to area—exponent of 1.0.)

CMP = Configuration and component adjustment including componenmaterial multipliers, dimensionless (See Cost Estimating Book

F = Fixed cost add on which is a function of exchanger class (smaor large) and design pressure, $ (at 655 EDMI)

m = Multiplier reflecting linear cost change with area, $/ft2; the multi-plier is a function of exchanger class—small or large—and design pressure

For a typical exchanger configuration with all carbon steel construction and 300design pressure (both sides), the expression simplifies to:

HEX = (EDMI/655) 5.5 [13,100 + (8.8 A)](Eq. 400-6)

This equation assumes that the installation factor (I) is 5.5, area and tax adjustm(T) is 1.065, material add on (MTL) is 0, and configuration adjustment (CMP) is0.935. CMP is for 20 feet (straight length) U-tubes. F and m are for exchangerswith 1000 ft2 or more.

The cost expression is different for high pressure shell and tube heat exchange(design pressure well above 600 psi). Cost varies with the area to the 0.64 powSee the Cost Estimating Books for details.


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