How To Use HTRI For Shell & Tube Exchanger DesignFrank Shan May 18, 2005 Contents What Can HTRI Do General Procedures Example: Liquid-Liquid Exchanger Design Result Evaluation What Can HTRI Do? Air Cooler HTRI - Heat Transfer Research Inc. Fire Heater Hairpin Exchange r S&T Exchanger HTRI Xchanger Suite Jacket Pipe Plate-Frame Exchanger Exchanger Tube Layout Vibration Analysis Simulation.General Procedure Data Sheet Case Mode Rating. Design Shell & Tube Geometry Process Inlet/Outlet Fluid (Cold/Hot) Properties Result Analysis End Other Input . Example: Liquid-Liquid S&T Exchanger Standard Data Sheet . 1. Create an empty case: select File > New Shell and Tube Exchanger . 1.1 Xist Main Window Click for help Required Input is highlighted in red Navigation Tree Click + to expand . Setting Unit: select Edit > Data Units.2. or click button . Design You define most exchanger geometry and enough process conditions for Xist to calculate the required heat duty. . Simulation You define exchanger geometry and fewer process conditions for Xist to calculate the required heat duty.3. Select Case Mode Rating (Default) You define exchanger geometry and enough process conditions for Xist to calculate the required heat duty. Input Shell Side Geometry HTRI allows shell diameter up to 1000 in .4. the E-type is the least expensive shell.Shell and Tube Exchanger Selection Shell Selection depends on available ∆P. (Courtesy of TEMA) . Shell and Tube Exchanger Selection (Courtesy of GPSA) . Input Tube Side Geometry .5. Tube Geometry Tube Dia.25. the more economical the exchanger. Tube Length: In general. 1. 1 inch tube are normally used when fouling is expected. Tube Pitch Ratio: 1.: 3/4 ~ 1 in are more compact and more economical. 16 ft or 20 ft facilitate reasonable plot space and maintenance for horizontal exchanger.5 pitch ratio has been proved effective . 1.333 are most common For kettle reboiler operating at low pressure. or low ∆P is required. Practically. the greater the ratio of tube length to shell diameter. Tube layout A 30-degree layout (default) is most common. Triangular tube-layouts result in better shellside coefficients and provide more surface area in a given shell diameter. whereas square pitch or rotated-square pitch layout are used when mechanical cleaning of tube outside is required . 6. Input Baffles Geometry . Baffle Type Cut range: 1 – 49% Cut range: 5 – 30% For TEMA E Shell. as start point) .Crosspass = No. No.Baffle+1 Double-segmental Baffle Cut range: 5 – 30% Baffle cut (100*h/D): 17% to 35% of shell diameter A 22% cut is the optimum (HTRI) Baffle spacing: 20% to 100% of shell diameter (HTRI recommends 40% of shell dia. Input Shellside Nozzle Location .7. Input Optional Data DT: only for printout DP: to calculate tubesheet thickness & bundle-to-shell clearance for pull-through floating head bundle .8. Input Process Data .9. 1 Select Physical Property Input Method The component-by-component option is recommended for single-phase-only fluids for which the variation in fluid properties is not large. .10. 10. Input Hot Fluid Properties. 2 Use User Define Properties .10. 10.3 Input Liquid Properties . (Same Procedure as Hot Fluid) . Input Cold Fluid Properties.11. developed by Hyprotech to transfer data from simulation HYSYS extension – allow you to develop and run the process simulator while using the HTRI proprietary methods.. . Hot/Cold Fluid Properties>Property Generator>select Property package – HYSYS >simulation file>select exchanger>select fluid>generate properties HTRIFileGen ..Alternate Input Methods (Process condition & properties) Import Case: (need simulator installed) File>Import Case>change file type >select simulation file>select exchanger> generate properties Property Generator. 12. Run Case Click or File>Run Case or Ctrl+F5 Indicate incomplete input . Result Drawing . 13. Program message Overdesign factor Main design dimensions ∆P Velocities Heat transfer coefficients Distribution of thermal resistances Flow regime distribution Terminal process conditions Baffle design EMTD and temp profile Vibration analysis . and think of the possibility of a better design. Analyze Final Results Consider the following. 13.1 Program Messages Fatal: Problems lead to incorrect results Warning: Unusual. limiting need your attention Informative: Unusual data . and/or vibration. Shellside velocities are more difficult but anything less than 3 fps will definitely foul when in heavy oil service. (Advised by Tom Kemp) .000 (English units).13. consider 4 feet per second on the tubeside as the “design” number.2 Velocity: High enough to suppress fouling Low enough to prevent erosion higher velocity gives better heat transfer and suppresses fouling. Faster is better until you reach 10-12 fps for water or (density) x velocity^2 of 10. But too high a velocity will cause tube erosion.000 to 12. thus provides a longer run length. For heavy oil services. 3 Thermal Resistances Check thermal resistances for shellside. Check dominant value. and heat transfer coefficient Design requirement Reduce tube pitch Increase shellside velocity Bypassing and leaking Decrease tube dia. MDMT. Shellside Heat Transfer Limited Action Result Watch For Change shell type (F.13.G) Increase shellside velocity. tubeside. Slight increase in heat transfer coefficient Tubeside ∆P increase Consider finned tubes Smaller exchanger Use sealing strips Reduce E stream with decreased baffle-to-shell clearance . and tube metal. fouling. Tubeside Heat Transfer Limited Action Result Change tube length Improve tubeside performance Decrease tube dia.4 Overdesign Factor Overdesign = (Qcalc – Qreq’d) / Qreq’d x 100 = (Ucalc – Ureq’d) / Ureq’d x 100 . velocity at given shell size Switch tube/shell side More efficient design Increase tube pitch Increase tubeside velocity at given shell size because of fewer tubes Watch For Increased tubeside ∆P 13. Increase tubeside h. 13.5 Shellside Flow Distribution B stream: C and F stream: normally at least 60% of total flow for turbulent flow and 40% for laminar flow Normally should not exceed 10% . . 13. try to meet the required ∆P. Shellside ∆P Limited Action Result Watch For Change shell type ∆P reduced greatly (TEMA E to J decrease by up to factor of 8) Investigate multisegmental bundles Double-segmental baffle ∆P reduced to about 1/3 of that for segmental baffle with same central spacing Tube vibration is possible Investigate NTIW bundles ∆P reduced to 1/4 if window area large enough Extreme caution: inefficient heat transfer may result Increase baffle cut ∆P reduced by large cut Increase nozzle sizes ∆P reduced . reboiler). For critical exchangers (condenser. “no fouling” is the first concern over ∆P. For heavy streams. exchangers are larger than necessary to accommodate allowable ∆P rather than to satisfy heat transfer demands.6 Pressure Drop It is highly undesirable if the exchanger is limited by ∆P. ∆P~f(d^5) Decrease tube pitch Larger tubeside flow area (more tubes fit into shell) Check singletubepass design ∆P is 1/8 of that of 2tubepass design Decrease tube length ∆P reduced sharply Increase nozzle sizes ∆P reduced Watch For Reduces heat transfer surface and shellside flow area. ∆P reduced sharply.Tubeside ∆P Limited Action Result Increase tube dia. . Finishing Re-adjust the parameters if necessary Re-run the case Not satisfied Evaluation Satisfied Finish .14. Thanks ! .
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