WTS Table of contents. Layout

Transcription

1 Table of contents Thermal and hydraulic design of shell and tube heat exchangers... 2 Tube sheet data... 4 Properties of Water and Steam... 6 Properties of Water and Steam... 7 Heat transfer in pipe flow... 8 Heat transfer on the shell side in baffeled shell and tube heat exchangers... Corrected logarithmic mean temperature difference (CLMTD) and temperature distribution according to cell method... 3 Tube-side pressure drop in shell and tube heat exchangers... 4 Tube bundle vibration analysis... 6 Pressure drop in the outer shell of heat exchangers... 7 CAD program for shell and tube heat exchangers... 9 CAD sketch from WCAD... 2 MS Excel specification sheet... 2 Layout Input values:.234 or.234 Calculated values:.234 or.234 Critical values:.234 or.234 Estimated values:.234 or.234 Lauterbach Verfahrenstechnik GmbH 2..27

2 Thermal and hydraulic design of shell and tube heat exchangers Medium Water Mass flow Volume flow Inlet pressure (abs.) Inlet temperature Outlet temperature Mean temperature Actual Inlet temperature Outlet temperature m i V i P i ϑe i ϑa i ϑm i ϑe i ϑa i Tube-side Shell-side Water 2 kg/s m a 2.5 kg/s m³/h V a 44. m³/h 4 bar P a 3 bar 8 ϑe a 2 6 ϑa a 53 7 ϑm a ϑe a ϑa a 54.2 Heat duty Heat loss Q i Q a -675 kw 675 Qv a kw kw Fouling resistance f i m² K/W f a m² K/W Geometry From tubesheet library Installation position: Horizontal Bare tubes Straight tubes with fixed tubesheets Bare tubes Segmental baffles D a Shell outside diameter 46.4 Shell wall thickness s 6.3 Shell inside diameter D i Bundle-to-shell clearance 3.8 Min. bundle-to-shell clearance 2 Tube outside diameter Tube inside diameter Tube pitch (transverse) Pitch angle Tube lane width (horizontal) d a d i s Tube wall thickness Tube pitch (longitudinal) s i s Φ 6 32 b h Central baffle spacing Inlet baffle spacing Baffle borehole diameter Number of sealing strips pairs Number of baffles / pass Baffle diameter Baffle cut in % of shell ID 22 % Baffle thickness 4 Tube material Thermal conductivity of tube material λ Stainless steel 5 W/(m K) Number of tube-side passes Number of shell-side passes Number of serial heat exchangers 2 Evaluation Required Final Overdesign Heat transfer area A m² Aa m² 6.4 % Tube length between the l 289 la 3 tubesheets Lauterbach Verfahrenstechnik GmbH

3 Results Number of tubes Heat transfer coefficient (inside) Heat transfer coefficient (outside) Overall heat transfer coefficient Logarithmic mean temperature diff. LMTD FN Factor (Correction factor for LMTD) Log. mean temperature diff. (corrected) CLMTD Total fouling resistance N α i α a k ϑ FN ϑ c f W/(m² K) W/(m² K) W/(m² K) K K m² K/W Tube-side Shell-side Velocity (tube-side).356 m/s Velocity (shell-side) Velocity (window zone).2 m/s.9 m/s Reynolds number Re Reynolds number Re 388 Pressure drop p i 667 Pressure drop p a 2595 Mean tube wall temperature ϑw i 6.6 Mean tube wall ϑw a 49.6 temperature Inlet nozzle Nominal width Outside diameter Inside diameter Velocity Outlet nozzle Nominal width Outside diameter Inside diameter Velocity Inlet nozzle DN 25 Nominal width DN Outside diameter Inside diameter m/s Velocity ρ v² Outlet nozzle DN 25 Nominal width DN Outside diameter Inside diameter m/s Velocity.8975 m/s kg/(m s²) m/s Physical properties Tube-side Shell-side Density ρ i kg/m³ Density ρ a kg/m³ Specific heat capacity cp i 487 J/(kg K) Specific heat capacity cp a 478 J/(kg K) Thermal conductivity λ i.6598 W/(m K) Thermal conductivity λ a.6242 W/(m K) Dynamic viscosity.436 m s Dynamic viscosity.698 m s Equations Heat balance η i η a Overall heat transfer coefficient Lauterbach Verfahrenstechnik GmbH

4 Tube sheet data Description of type Baffle-type Segmental baffles Shell outside diameter Shell inside diameter Minimum bundle-to-shell clearance Bundle-to-shell clearance Bundle diameter at cross flow zone Bundle diameter (cross flow zone and window zone) D o D i D m D D B D BE Tube outside diameter Tube inside diameter Tube pitch (transverse) Tube pitch (longitudinal) Pitch angle Baffle diameter Height of baffle cut Height of the window in % of shell inside diameter Tube pattern Arrangement d a d i s s 2 Φ D l H staggered % around central tube No tubes in window? Number of tube-side passes Number of shell-side passes Tube lane width (horizontal) Tube lane width (vertical) Outside diameter of the head Bolt-circle diameter Number of bolts on the bolt-circle Rotation angle for bolt-hole pattern D a D t No Number of tubes Number of duy tubes Number of tie rods Total number of tubes, duy tubes and tie rods Number of tubes, duy tubes and tie rods in the upper and lower window Number of tubes, duy tubes and tie rods in the cross flow zone Number of tube rows in a window Number of tube rows in the cross flow zone Number of tube rows in the end zone Sum of the shortest connecting paths in the center Shortest connecting path between tube and tube Shortest connecting path between tube and shell Number of connections n n B n Z n G n F n S n R,F n W n W,E Le e e n V Mean distance boundary tubes - bundle centre r h Number of boundary tubes required/actual RR / Perimeter of the tube layout Total area enclosed by perimeter C p A p m² Lauterbach Verfahrenstechnik GmbH

5 Number of tubes, duy tubes and tie rods per pass ss-no Final bundle length Total area Number of baffles per shell-side path Central baffle spacing Distance between the tubesheet and the st baffle Baffle borehole diameter Number of pairs of sealing strips Number of exchangers in series l a A ges N S S 2 n D m² Nozzles Tube-side Shell-side Inside nozzle diameter (inlet) Inside nozzle diameter (outlet) Lauterbach Verfahrenstechnik GmbH

6 Properties of Water and Steam Calculation for saturation? Temperature Pressure State State 2 No No ϑ 36.5 ϑ p 3 bar p 2 3 bar Properties of liquid water or superheated steam State State 2 Liquid Liquid Density ρ kg/m³ ρ kg/m³ Spec. isob. heat capacity c p 478 J/(kg K) c p 479 J/(kg K) Thermal conductivity λ.6242 W/(m K) λ.6397 W/(m K) Dynamic viscosity η.698 m s η.5544 m s Kinematic viscosity ν 7.26e-7 m²/s ν 5.68e-7 m²/s Prandtl number Pr Pr Thermal diffusivity a.53e-7 m²/s a.548e-7 m²/s Specific volume v.6 m³/kg v.2 m³/kg Spec. isoc. heat capacity c v 488 J/(kg K) c v 428 J/(kg K) Specific enthalpy h 5377 J/kg h 2652 J/kg Spec. internal energy u J/kg u J/kg Specific entropy s J/(kg K) s J/(kg K) Compressibility factor Z.23 Z.24 Surface tension σ 7.6 mn/m σ 68.9 mn/m Coefficient of thermal expansion β 3.576e-4 /K β 4.56e-4 /K Isentropic exponent κ 775 κ 7862 Speed of sound w 525 m/s w 545 Dielectric constant ε ε 7.2 m/s Characteristics Validity Molar mass M 8.2 g/mol. ϑ 8 Gas constant R 46.5 J/(kg K).62 bar p bar Critical temperature Critical pressure Critical density T c p c ρ c e kg/m³. ϑ 2.62 bar p 5 bar Lauterbach Verfahrenstechnik GmbH

7 Properties of Water and Steam Calculation for saturation? Temperature Pressure State State 2 No No ϑ 7 ϑ p 4 bar p 2 4 bar Properties of liquid water or superheated steam State State 2 Liquid Liquid Density ρ kg/m³ ρ kg/m³ Spec. isob. heat capacity c p 487 J/(kg K) c p 482 J/(kg K) Thermal conductivity λ.6598 W/(m K) λ.65 W/(m K) Dynamic viscosity η.436 m s η.4657 m s Kinematic viscosity ν 4.28e-7 m²/s ν 4.736e-7 m²/s Prandtl number Pr Pr Thermal diffusivity a.6e-7 m²/s a.583e-7 m²/s Specific volume v.23 m³/kg v.7 m³/kg Spec. isoc. heat capacity c v 3922 J/(kg K) c v 3973 J/(kg K) Specific enthalpy h J/kg h 2577 J/kg Spec. internal energy u 2929 J/kg u 253 J/kg Specific entropy s J/(kg K) s 83.7 J/(kg K) Compressibility factor Z.2583 Z.2645 Surface tension σ mn/m σ mn/m Coefficient of thermal expansion β 5.838e-4 /K β 5.233e-4 /K Isentropic exponent κ 5935 κ 594 Speed of sound w 558 m/s w 554 Dielectric constant ε ε m/s Characteristics Validity Molar mass M 8.2 g/mol. ϑ 8 Gas constant R 46.5 J/(kg K).62 bar p bar Critical temperature Critical pressure Critical density T c p c ρ c e kg/m³. ϑ 2.62 bar p 5 bar Lauterbach Verfahrenstechnik GmbH

8 Heat transfer in pipe flow Constant wall temperature Process data Total mass flow Total volume flow Number of tubes with parallel flow Mass flow per tube Inlet temperature Outlet temperature Mean temperature Pressure (abs.) m tot V tot Z m ϑ e ϑ a ϑ m p kg/h m³/h kg/h bar Physical properties Fluid liquid / gaseous? liquid Density Specific heat capacity Thermal conductivity Dynamic viscosity Kinematic viscosity Prandtl number Prandtl number at wall temperature Wall temperature ρ cp λ η ν Pr Pr W ϑ W e kg/m³ J/(kg K) W/(m K) m s m²/s Geometry Tube circular / non-circular? Circular tubes Tube length Tube inside diameter Cross sectional area of the tube Perimeter of the tube Hydraulic diameter l d i f u d h e m² Heat transfer Flow velocity Reynolds number Nusselt number Heat transfer coefficient w Re Nu α m/s W/(m² K) Heat duty Q = m tot c p (ϑ a - ϑ e ) Q kw Lauterbach Verfahrenstechnik GmbH

9 Equations Constant wall temperature Turbulent flow (Re > ) Correction factor K (Effect of temperature dependent property variations) Liquids Lauterbach Verfahrenstechnik GmbH

10 Heat transfer on the shell side in baffeled shell and tube heat exchangers Geometrical data Tube arrangement staggered Shell inside diameter Bundle diameter at cross flow zone D i D B Tube outside diameter Tube pitch (transverse) Tube pitch (longitudinal) Baffle diameter Height of baffle cut Diameter of the bore holes in the baffles Baffle spacing Number of tubes including blanks and support tubes Number of tubes in the upper and lower windows Number of main resistances in a cross-flow zone Number of connections Distance between boundary tubes and shell Shortest connecting path between tube and tube Sum of the shortest connecting paths in the center Number of sealing strip pairs Number of shell-side passes Fluid Mass flow Volume flow d a s s 2 D l H d B S n n F n W n V e e L E n S N D m V kg/h m³/h Inlet temperature Outlet temperature Mean temperature ϑ e ϑ a ϑ m Fluid liquid /gaseous? Density Specific heat capacity Thermal conductivity Dynamic viscosity Kinematic viscosity Prandtl number Prandtl number at tube wall temperature Reynolds number Heat transfer coefficient ρ cp λ η ν Pr Pr W Re ψ, α liquid e kg/m³ J/(kg K) W/(m K) m s m²/s W/(m² K) Lauterbach Verfahrenstechnik GmbH 2..27

11 Results Calculation of Nu,Bundle Calculation of f G Lauterbach Verfahrenstechnik GmbH 2..27

12 Calculation of f L Calculation of f B for n S n W / 2 for e < (D i - D B ) Correction factor K (Effect of temperature dependent property variations) Heating of liquids Lauterbach Verfahrenstechnik GmbH

13 Corrected logarithmic mean temperature difference (CLMTD) and temperature distribution according to cell method Corrected logarithmic mean temperature difference (CLMTD) and distribution with cell method for shell and tube heat exchangers Tube-side inlet temperature Shell-side inlet temperature t i t a 8 2 Tube-side mass flow Shell-side mass flow Specific heat capacity tube-side Specific heat capacity shell-side m i m a c p,i c p,a kg/h kg/h J/(kg K) J/(kg K) Heat capacity flow tube-side; W w,i = m i c p,i Heat capacity flow shell-side; W w,a = m a c p,a W w,i W w,a W/K W/K Number of baffles Number of shell-side passes Number of tube-side passes Sheet plus shell type Number of tube rows per cell N U N s N t Actual overall heat transfer coefficient Actual heat transfer area k A W/(m² K) m² = unmixed;.5 = mixed Tube flow: countercurrent = ; cocurrent = 2 Flow pattern: countercurrent = ; cocurrent = 2 Tube-side outlet temperature Shell-side outlet temperature t i2 t a LMTD countercurrent flow FN factor CLMTD corrected log. mean temperature difference T Geg FN T m K K Number of cells Product k A Product k A per cell W/K W/K Tube-side efficiency Shell-side efficiency Tube-side cell efficiency Shell-side cell efficiency Maximum tube-side temperature Maximum shell-side temperature Minimum tube-side temperature Minimum shell-side temperature Max. temperature inversion in one cell t i,max t a,max t i,min t a,min t inv Lauterbach Verfahrenstechnik GmbH

14 Tube-side pressure drop in shell and tube heat exchangers Physical properties Mean temperature Wall temperature Fluid: liquid / gaseous? liquid Inlet temperature ϑ e 8 Outlet temperature ϑ a 6 Mean temperature ϑ m = (ϑ e +ϑ a ) / 2 Inlet pressure (abs.) Density ϑ m P e ρ 7 4 bar kg/m³ kg/m³ Specific heat capacity Thermal conductivity Dynamic viscosity cp λ η 487 J/(kg K).6598 W/(m K).436 m s.4657 m s Geometrical data Type: Straight tube / U-tube? Tube outside diameter Tube wall thickness Tube inside diameter Number of tube-side passes Number of tubes per pass Length of one tube Inside nozzle diameter (inlet) Inside nozzle diameter (outlet) Acceleration due to gravity Mass flow Volume flow Mean velocity in the tube Mean velocity in the inlet nozzle Mean velocity in the outlet nozzle Reynolds number Prandtl number Grashof number Friction factor (inlet, outlet and baffle) Fanning friction factor (tube, isothermal) Correction factor for the viscosity Correction factor for the convection Friction factor (tube) (ξ = ξ is Φ ψ) Pressure drop (inlet nozzle) Pressure drop (outlet nozzle) Pressure drop (inlet, outlet and baffle) Pressure drop (friction) Fouling factor Total pressure drop ( P = F t P t + P e + P N,e + P N,a ) d a s d i n P n R L d N,e d N,a g m V w w N,e w N,a Re Pr Gr Ke ξ is Φ ψ ξ P N,e P N,a P e P t F t P Straight tube m/s² kg/s m³/h m/s m/s m/s Lauterbach Verfahrenstechnik GmbH

15 Equations Straight tubes, multiple passes Lauterbach Verfahrenstechnik GmbH

16 Tube bundle vibration analysis General formulation Tube outside diameter Tube wall thickness Tube inside diameter d a s d i Tube pitch (transverse) Tube pitch (longitudinal) Transverse pitch ratio Longitudinal pitch ratio Cross-sectional area of the tubes Second moment of area of the tubes Modulus of elasticity Effective density s s 2 s /d a s 2 /d a A J E ρ ² ^4 N/² kg/m³ Support for the tubes Factor for the support Factor for additional forces Arrangement of the tubes Strouhal number of the bundle jointed - fixed C C f 3.93 Staggered bare tubes Sr.2292 Final span Velocity in the narrowest cross section L w e m/s.2 m/s Natural frequency of the tubes Safety factor Allowable excitation frequency Excitation frequency of the flow f z = f R /S f R S f z f err 438 /s 667. /s /s /s.29 /s.6 /s Vibration probable, if f err > f z Equations Lauterbach Verfahrenstechnik GmbH

17 Pressure drop in the outer shell of heat exchangers Shell-side pressure drop in shell-and-tube heat exchangers with segmental baffles Shell inside diameter D i Bundle diameter at cross flow zone D B Bundle diameter (cross flow zone and window zone) D BE Tube outside diameter Tube pitch (transverse) Tube pitch (longitudinal) Pitch angle d a s s Baffle diameter Number of baffles Height of baffle cut Diameter of the bore holes in the baffles D l n U H d B Central baffle spacing Distance between the tubesheet and the st baffle Number of tubes including duy tubes and tie rods Number of tubes in the upper and lower windows Number of tube rows in a window Number of main resistances in the crossflow zone Number of main resistances in the end zone Number of connection lines Distance between boundary tubes and shell Number of sealing strip pairs Number of shell-side passes Inside nozzle diameter (inlet) Inside nozzle diameter (outlet) Fluid Mass flow Volume flow S S E n n F n RF n W n WE n V e n S N D d Ni d No m V kg/h m³/h Inlet pressure Inlet temperature Outlet temperature Mean temperature P E ϑ E ϑ A ϑ Fluid liquid / gaseous? liquid Density Specific heat capacity Thermal conductivity Dynamic viscosity Prandtl number Mean wall temperature Dynamic viscosity at mean wall temperature ρ cp λ η Pr ϑ W η W kg/m³ J/(kg K) W/(m K) m s m s Total pressure drop p total 2595 Lauterbach Verfahrenstechnik GmbH

18 Shell-side pressure drop in shell-and-tube heat exchangers with segmental baffles Cross-flow zone (n U -) N D p Q = ( 24 - ) 3.7 = 6939 End zone 2 p Q,E = Window zone n U N D p F = = = 773 Shell nozzles p N,i + p N,o = = 37 Total pressure drop p total = 2595 Results a.3 b.26 c.3 e 6 Cross-flow zone L E 9.8 A E.28 m² w e.2 m/s f a,l,f 25. f a,t,f.698 f a,l,v 25. f a,t,v f z,l.9896 f z,t.9682 ξ l ξ t.72.4 ξ.44 A SRU.3333 m² A SMU.272 m² A SG.464 m² R M R L r.686 γ 2.4 Re 2888 β 3.7 R S R B.235 A B.284 f L.3892 f B.489 p Q, 85 m² p Q 3.7 End zone Re E 3485 A E,E.258 m² w e,e.4737 m/s f B,E.489 p QE, p QE Window zone A FG.236 m² A FR.6283 m² A F.47 m² w p.8687 m/s w z.9376 m/s n WF 3.78 d h U F p F,l p F,t 68 p F 75.5 Shell nozzles w N,i ξ N,i w N,o.8975 m/s.8975 ξ N,o m/s p N,i p N,o 56.3 p N 37 Lauterbach Verfahrenstechnik GmbH

19 CAD program for shell and tube heat exchangers TEMA type AEL TEMA Front head A Shell E Rear head L Medium Water Tube-side Water Shell-side Inlet pressure (abs.) p i 4 p a 3 Pressure stage PN 5 PN 5 Inlet temperature ϑ e,i 8 ϑ e,a 2 Outlet temperature ϑ a,i 6 ϑ a,a 53 Mean temperature ϑ m,i 7 ϑ m,a 36.5 Design temperature 7 Design pressure 5 4 Inlet nozzle Set-on Set-on Type of flange Integral flange (welding-neck) with hub Integral flange (welding-neck) with hub Flange connection nominal width DN 25 DN 25 Outside diameter Nozzle wall thickness 4 4 Inside diameter Outlet nozzle Set-on Set-on Type of flange Integral flange (welding-neck) with hub Integral flange (welding-neck) with hub Flange connection nominal width DN 25 DN 25 Outside diameter Nozzle wall thickness 4 4 Inside diameter CAD Data Diameter of bore in tube sheet CAD Tubesheet Configuration Front head a - tubesheet integral with shell and channel Rear head b - tubesheet extended as flange / integral with shell / gasketed with channel / narrow-face gasket Geometry Shell outside diameter D a 46.4 Shell wall thickness s a 6.3 Shell inside diameter Bundle-shell distance Tube outside diameter D I d a Tube inside diameter d I 6 Tube pitch (transverse) s 26 Tube pitch (longitudinal) s Pitch angle Φ 6 ss lane width b 32 Central baffle spacing Number of baffles/pass 24 Inlet baffle spacing 235 Baffle diameter 39.8 Baffle borehole diameter 2.8 Baffle cut 22 % Sealing strips pairs Number of tube-side passes Number of shell-side passes Final bundle length Final shell length Number of tubes Expansion joint diameter Plate thickness (fixed plate) Outside diameter of tube sheet Plate thickness (free plate) Outside diameter of tube sheet (floating head) n t n s l a l a R Lauterbach Verfahrenstechnik GmbH

20 CAD sketch from WCAD Lauterbach Verfahrenstechnik GmbH

21 MS Excel specification sheet Lauterbach Verfahrenstechnik GmbH