performance investigation on shell -and-tube heat ... · pdf fileperformance investigation on...

4th International Conference On Building Energy Environment

Performance investigation on shell-and-tube heat exchangers with different baffles based on fluid-structure interaction

J Xiao1 J Wang1 G Jian1 S Wang1 J Wen2

1School of Chemical Engineering and Technology Xirsquoan Jiaotong University Xirsquoan 710049 China

2School of Energy and Power Engineering Xirsquoan Jiaotong University Xirsquoan 710049 China

SUMMARY Thermo-hydraulic performance and mechanical properties were discussed using numerical simulation method for three kinds of shell-and-tube heat exchangers with segmental baffles plain helical baffles and fold helical baffles based on thermal fluid-structure interaction When the shell-side volume flow is 14m3h-1~30m3h-1 the shell-side pressure drop overall heat transfer coefficient Nu∙f -13 and equivalent stress all go from highest to lowest under same shell-side volume flow rate in the following order fold helical baffles plain helical baffles and segmental baffles In addition the results of stress linearization at danger location in elastic stage show that membrane stress and sum of primary stress and secondary stress are in range of corresponding stress intensity for all three kinds of STHXs Hence the comprehensive thermal-structural performance of shell-and-tube heat exchangers with fold helical baffles is best which provide the theoretical guidance for design and choice of shell-and-tube heat exchangers with different baffles

INTRODUCTION Heat exchangers play an important role to heat mass transfer in a lot of engineering applications for instance petrochemical progress electric power production food industry environmental protection waste heat recovery refrigeration and so on Whatrsquos more shell-and-tube heat exchangers (STHXs) hold the dominant position with more than 35~40 of heat exchangers in the world [Huminic 2012Master et al 2007Bhutta et al 2012] STHXs have many advantages simple manufacturing robust construction and adaptability operation conditions Baffles are used to support heat transfer tubes and control shell-side flow distribution which have a significant effect on heat transfer enhancement and thermal-hydraulic performance of heat exchangers

The shell-and-tube heat exchangers with segmental baffles (STHXsSB) are typical in conventional STHXs which has been standard production in designing institutes and industries STHXsSB are characterized by high pressure drop flow dead zone leakage flow in large quantities easy fouling and flow induced vibration under high velocity etc[Gawande et al 2011Maakoul et al 2016Movassag et al 2013] which have disadvantages on flow and thermal performance of heat exchangers Hence many researchers had put forward to improving measures based on segmental baffles [Wang et al 2004 Singh et al 2013] In addition a new type of shell-and-tube heat exchangers with helical baffles (STHEsHB) was proposed to overcome the shortcomings of STHXsSB

STHXsHB were proposed by Lutcha and Nemcansky (1990) and realized industrialization by ABB Lummus in 1994 At present STHXsHB are mainly discontinuous helical baffles with four fan-shaped plain baffles form one helical pitch due to the manufacture of continuous helical baffles is difficult STHXsHB have plenty of advantages such as enhancing shell-side heat transfer decreasing pressure drop reducing shell-side fouling prolonging the running time and avoiding flow-induced vibration [STEHLIacuteK et al 1994 Master et al 2004 Wang et al 2010] As a consequence STHXsHB are most possibly considered to replace STHXsSB hence researchers had investigated the influence factors of performance and compared with STHXsSB [Zhang et al 2013 Gao et al 2015 Taher et al 2012] However discontinuous STHXsHB have the triangle leakage zones between two adjacent baffles that decreases radial flow rate and reduces the flow and heat transfer performance

In order to solve the problem of triangle leakage zones there are many useful methods to block Wang et al (2014) proposed a new type of shell-and-tube heat exchangers with fold helical baffles and Wen et al (2015) proposed a novel type of shell-and-tube heat exchangers with ladder-type fold baffles However it is a pity that the flow and heat transfer performance is just concerned and mechanical properties are neglected when improving performance of heat exchangers Therefore it is not certain that mechanical properties satisfy the requirement of design and manufacture when thermal-hydraulic performance is best due to fluid-induced vibration and fatigue failure in shell-and-tube heat exchangers

Up to now researchers have rarely meanwhile studied the thermal-hydraulic performance and mechanical properties of shell-and-tube heat exchangers In this paper three kinds of heat exchangers of shell-and-tube heat exchangers with segmental baffles plain helical baffles and fold helical baffles will be compared in terms of thermal-structural performance combing computational fluid dynamic (CFD) and finite element method (FEM) based on fluid-structure interaction (FSI) theory Fluid-structure interaction is mainly applied to but not limited to sedimentation turbulence aerodynamic bio-fluid and bio-mechanics and the application of FSI in existing literatures can prove FSI meet the demand of actual engineering design [Hou et al 2012 Hu et al 2013 Simoneau et al 2011 Yan et al 2010] The shell-side pressure drop shell-side heat transfer coefficient and Nu∙f -

13 will be presented for thermal-hydraulic performance and the stress classification and equivalent stress linearization will be performed to discuss the result of stress distribution of tube bundle

ISBN 978-0-646-98213-7 COBEE2018-Paper137 page 379


METHODS The geometry construction of STHXs with plain helical baffles fold helical baffles and segmental baffles are shown in Figure 1The shell diameter of STHXs is 250 mm and tube bundle is 1250 mm in length There are 40 tubes with the diameter of 19 mm which are arranged squarely with the tube pitch of 25 mm Besides 12 spacer tubes are set to fix baffles and increase flow disturbance in the shell side The thickness helical angle and overlapped degree of shell-and-tube heat exchanger with helical baffles are respectively 6mm 18deg and 50

Figure 1 Tube bundle of STHEs with different baffles

Using indirect thermal stress calculation method based on thermal fluid-structure interaction it is convenient to import bundle temperature form fluid dynamics to solid dynamics for mechanical analysis Due to the temperature gradient external constraints or internal deformation compatibility requirements the additional stress namely thermal stresses is generated Solving the thermal stress according to thermoelastic theory it needs to satisfy basic hypothesis such as material uniformity continuity completely elasticity isotropy and small deformation Hence governing equations mainly include fluid dynamics equations and solid mechanics equations

As the physical model depicted before there are three domains in shell-and-tube heat exchanger two fluid domains (heat-conducting oil in shell side and water in tube side) and the solid domain (tube bundle) Hexahedral grids were used in the tube side while unstructured grids were used in the shell side and solid domain To improve the accuracy of the calculation adaptive grid technique was used and grid independence was verified Figure 2 presents the local grid of STHXs with fold helical baffle and Table 1 shows the detailed data of grids

The RNG k-ε model is adopted in the simulation The boundary conditions of tube-shell side inlet and outlet were set as velocity inlet and pressure outlet respectively The shell-inlet temperature was 33715 K The tube-inlet velocity was 118m∙s-1 and temperature was 30315 K Non-slip impermeable and adiabatic boundary conditions were adopted on the wall except fluid-solid interface with coupled wall Pressure-Velocity coupling algorithm was SIMPLE and second-order upwind scheme was adopted for solving the mass momentum energy and turbulent kinetic energy equation The convergence criterion was that the normalized residuals are less than 1times10-4 for all equations In the solid domain material was structural steel Density is 7854 kgm-3 heat conductivity is 605 Wm-1K-1 specific heat capacity is 434 Jkg-1K-1 and the allowable stress is 147 MPa when temperature is in the range of 30~70

Figure 2 Local grid of heat exchanger with fold baffle

Table 1 Mesh details and metrics

Baffles type

Elements Average skewness

Average element quality

Average orthogonal quality

Plain 25128983 023577 083009 085112

Fold 19895942 024684 082391 084575

Segmental 26227443 022724 083748 085654

The numerical results compared with the experimental data for the shell-and-tube heat exchangers with plain helical baffles where helical angle was 18deg and the overlap was 50 from the reference [Chen et al 2015] as shown in Figure 3 The figure shows that simulated and experimental values agreed well The maximum relative error of pressure drop in inlet and outlet was less than 15 with an average value of 147 Hence it can be concluded that the numerical method is reliable At the same time the numerical pressure drop was less than the experimental values The deviations may attribute to some simplification made in the physical model and some un-avoidable measurement error



12 14 16 18 20 22 24 26 28 30 325000

10000

15000

20000

25000

30000

35000

∆P

Pa

V m3sdoth-1

Simulation results Experiment data

Figure 3 Comparison between numerical results and

experimental data

RESULTS Flow performance Due to the different structural forms of baffles the shell side streamline differed apparently As shown in Figure 4 the streamlines of the three types of heat exchangers are plotted By comparison it is found that in STHXs with helical baffles fluid flows in an obvious spiral way And STHXs with fold helical baffles can make fluid flow spirally and more easily since that flowing is better in designed helical channel In addition in STHXs with fold helical baffles streamlines in the center along the axis of the shell are denser than that in STHEs with plain helical baffles as well as higher mass flow rate and velocity The reason is that fold helical baffles effectively plug the triangle leakage zone between baffles and shell However due to the zigzag flow pattern STHXs with segmental baffles have obvious dead zones which result in high pressure drop and low heat transfer efficiency Figure 5 shows the shell side pressure drop in three kinds of heat exchangers It is found that total pressure drop in STHXs with fold helical baffles is the maximum while shell-side pressure drop in STHXs with segmental baffles is the minimum

Figure 4 Streamline in shell-and-tube heat exchangers

12 14 16 18 20 22 24 26 28 30 32

5000

10000

15000

20000

25000

30000

35000

40000

45000

∆P

Pa

Vm3sdoth-1

Plain baffle Fold baffle Segmental baffle

Figure 5 Total pressure drop versus volume flow rate

Heat transfer performance Figure 6 shows the temperature distribution of tube bundle in the three types of heat exchangers when the shell-side volume rate is 14m3h-1 As can be seen in Figure 6 the temperature of baffle located at the entrance in the shell side is almost as high as the heat-conducting oil temperature The temperature of spacer tubes and tubes is distributed uniformly and the temperature of spacer tubes is higher because cooling water does not pass through spacer tubes However the conjunction of baffles and tubes has a large temperature gradient because the baffles located in the shell side on the one hand baffles have heat convection with shell-side flow and baffles have conduction with tubes on the other hand which causes the temperature of baffles is between temperature of heat-conducting oil and water Whatrsquos more the temperature near spacer tubes is higher than the temperature near the tubes In the shell-and-tube heat exchangers external constrain will cause thermal stress when temperature is uneven

Figure 6 Temperature contours of tube bundle

The effect of volume flow rate on the heat transfer coefficient is shown in Figure 7 As depicted in Figure 7 with the volume flow rate increasing the heat transfer is also enhanced When the volume flow rate is same the heat transfer coefficient of STHXs with fold helical baffles is higher than two other types of heat exchanger and heat transfer coefficient of STHXs with segmental baffles is the minimal When the volume flow rate increases from 14m3h-1 to 30m3h-1 the heat transfer of coefficient STHXs with fold helical baffles increases 147~173 compared to that of STHXs with plain helical baffles while compared to that of STHXs with segmental baffles the heat transfer coefficient of STHXs with fold helical baffles enhanced 203~278 In STHXs with helical baffles flowing is spiral and has no dead zones therefore the heat transfer coefficient is higher than



STHXs with segmental baffles and fold helical baffles effectively plug the leakage zone between baffles and shell so that the flow velocity in the center increases and the heat transfer is enhanced

12 14 16 18 20 22 24 26 28 30 32200

250

300

350

400

450

K W

sdotm-2

sdotK-1

V m3sdoth-1


Figure 7 Heat transfer coefficient versus volume flow rate

Comprehensive performance In fact there are many comprehensive performance evaluation indexes of heat transfer enhancement in heat exchangers Considering the heat transfer coefficient and resistance coefficient are not the same order of magnitude and the effect of pressure drop on economic losses and energy consumption is only small part therefore Nu∙f -13 is selected to evaluate comprehensive performance of three types of heat exchangers The effect of volume flow rate on the Nu∙f -13 is shown in Figure 8 At the same volume flow rate the PEC number of STHXs with fold helical baffles the maximal while that of STHXs with segmental baffle is the minimal When the volume flow rate increases from 14m3h-1 to 30m3h-1 the Nu∙f -13 of STHXs with fold helical baffles increases 97~102 compared to that of STHXs with plain helical baffles and it enhances 1072~1106 compared with STHXs with segmental baffles

12 14 16 18 20 22 24 26 28 30 32210

215

220

225

230

235

240

Nusdotf -

13

V m3sdoth-1

Plain baffle Fold baffle

1124

1126

1128

1130

1132

1134

1136

Segmental baffle

Nusdotf

-13


Mechanical properties Figure 9 shows the equivalent stress of three types of heat exchangers when the volume flow rate is 14m3h-1 As depicted the equivalent stress of spacer tubes is maximal and at the contact position of baffles and tubes the equivalent stress is larger than other parts of baffles since high temperature space tubes large temperature gradient and local stress concentration caused by discontinuous construction The maximum of equivalent stress of STHXs

with fold helical baffles is 10907 MPa that of STHXs with plain helical baffles is 10556 MPa and that of STHXs with segmental baffles is 10545 MPa Due to the STHXs with fold helical baffles has the best heat transfer performance large temperature difference resulted to large corresponding thermal stress The effect of volume flow rate on the equivalent stress is presented in Figure 10 It is noted that the maximum equivalent stress is smaller than the yield strength of the material that is 250 MPa which indicates the tube bundle are still in elastic range

Figure 9 Equivalent stress contours of tube bundle

12 14 16 18 20 22 24 26 28 30 32

106

108

110

112

114

116

σ e M

Pa

V m3sdoth-1


Figure 10 Maximum equivalent stress versus

Volume flow rate

Based on equivalent stress linearization theory stress classification and stress evaluation were conducted at contact position of baffles and spacer tubes and the stress evaluation path is presented in Figure 11 In consideration of construction and load character at stress evaluation path it can be seen the membrane stress is local membrane stress and the sum of membrane stress and bending stress is equal



to primary stress plus secondary stress Figure 12 shows the results of equivalent stress linearization at same stress evaluation path It noted that the membrane stress of STHXs with fold helical baffles is maximal while that of STHXs with plain helical baffles is minimal The sum of primary stress and secondary stress along the thickness direction from interior node1 to exterior node 2 decreases first and then increases Whatrsquo more the maximum is at exterior node 2 and the minimum is near the middle face The result of stress evaluation is represented in Table 2 As shown the design satisfies the strength requirement

Figure 11 Stress evaluation path

0 1 2 3 4 5 6

44

48

52

56

60

64

σ M

Pa

tmm

Plain baffle Membrane stress Primary stress and secondary stress

(a) Plain baffle

0 1 2 3 4 5 640

42

44

46

48

50

52

54

56

σ M

Pa

tmm

Fold baffle Membrane stress Primary stress and secondary stress

(b) Fold baffle

0 1 2 3 4 5 6

42

43

44

45

46

47

48

σ M

Pa

tmm

Segmental baffle Membrane stress Primary stress and secondary stress

(c) Segmental baffle

Figure 12 Results of stress linearization at same path

Table 2 Results of stress evaluation

Heat exchanger PLMpa Max PL+Pb+QMpa

Plain 44782 56862

Fold 41927 52134

Segmental 42128 45745

Criterions PLle15Sm=2205 PL+Pb+Qle3Sm=441

Conclusions Safe Safe

CONCLUSIONS Based on thermal fluid-structure interaction the thermal-hydraulic performance and mechanical properties were discussed among shell-and-tube heat exchangers with plain helical baffles fold helical baffles and segmental baffles The research results can provide theoretical guidance of design manufacture and processing

(1) Through the comparison of flow performance it can be found that flowing is zigzag in STHXs with segmental baffles while in STHXs with helical baffles fluid flows spirally And STHXs with fold helical baffles can conduct spiral flowing more easily When the volume flow rate is in the range of 14m3h-1~30m3h-1 pressure drop in STHXs with fold baffles is the maximal while pressure drop in the segmental baffle heat exchanger is the minimal

(2) Through the comparison of heat transfer performance it can be seen that when the volume flow rate increases from 14m3h-1 to 30m3h-1 the heat transfer coefficient of STHXs with fold helical baffles enhanced 147 ~173 and 203 to 278 respectively compared to that of STHXs with plain helical baffles and STHXs with segmental baffles In addition The PEC number of STHXs with fold helical baffles is increases 97 ~102 and 1072~1106 respectively compared to that of STHXs with plain helical baffles and STHXs with segmental baffles

(3) Using stress classification and equivalent stress linearization method equivalent stress is large at the contacting positing of baffles and spacer tubes and the maximum equivalent stress of STHXs with fold baffles is maximal at the same conditions but stress satisfies strength requirement Therefore the thermal-structural performance of STHXs with fold helical baffles is best



(4) Based on the thermal fluid-structure interaction theory heat transfer performance and mechanical properties can be efficiently compared which provide a guidance to select heat exchangers with superior thermal-structural performance

ACKNOWLEDGEMENT This work is supported by the National Natural Science Foundation of China (No 51676146)

REFERENCES Huminic G and Huminic A 2012 Application of nanofluids in

heat exchanger A review Renewable amp Sustainable Energy Reviews 16(8) 5625-5638

Master B Chunangad K Boxma A et al 2007 Most frequently used heat exchangers from pioneering research to worldwide applications Heat Transfer Engineering 27(6) 4-11

Bhutta M Hayat N Bashir M et al 2012 CFD application in various heat exchangers design A review Applied Thermal Engineering 32(1) 1-12

Gawande S Keste A Navale L et al 2011 Design optimization of shell and tube heat exchanger by vibration analysis Modern Mechanical Engineering 1(1) 6-11

Maakoul A Laknizi A Saadeddine S et al 2016 Numerical comparison of shell-side performance for shell and tube heat exchangers with trefoil-hole helical and segmental baffles Applied Thermal Engineering 109 175-185

Movassag S Taher F Razmi K et al 2013 Tube bundle replacement for segmental and helical shell and tube heat exchangers Performance comparison and fouling investigation on the shell side Applied Thermal Engineering 51(1-2) 1162-1169

Wang Y Deng X Chen Y et al 2004 Flow and heat transfer characteristics in shell side of shell-and ndashtube heat exchangers with separated baffles parallel to segmental baffles Journal of Chemical Industry amp Engineering 55(2) 275-279

Singh A and Sehgal S 2013 Thermohydraulic analysis of shell-and-tube heat exchanger with segmental baffles ISRN Chemical Engineering Vol4

Lutcha J and Nemcansky J 1990 Performance improvement of tubular heat exchangers by helical baffles Chemical Engineering Research amp Design 68(3) 263-270

STEHLIacuteK P NĚMČANSKYacute J Kral D et al 1994 Comparison of correction factors for shell-and-tube heat exchangers with segmental or helical baffles Heat Transfer Engineering 15(1) 55-65

Master B Chunangad K and Pushpanathan V 2004 Fouling mitigation using helixchanger heat exchangers Heat Exchanger Fouling and Cleaning Fundamentals and Applications

Wang Q Chen G Chen Q et al 2010 Review of improvements on shell-and-tube heat exchangers with helical baffles Heat Transfer Engineering 31(10) 836-853

Zhang J Guo S Li Z et al 2013 Experimental performance comparison of shell-and-tube oil coolers with overlapped helical baffles and segmental baffles Applied Thermal Engineering 58(1-2) 336-343

Gao B Bi Q Nie Z et al 2015 Experimental study of effects of baffle helix angle on shell-side performance of shell-and-tube heat exchangers with discontinuous helical baffles Experimental Thermal amp Fluid Science 68 48-57

Taher F Movassag S Razmi K et al 2012 Baffle space impact on the performance of helical baffle shell and tube heat exchangers Applied Thermal Engineering 44(44) 143-149

Wang S Wen J Yang H et al 2014 Experimental investigation on heat transfer enhancement of a heat exchanger with helical baffles through blockage of triangle leakage zones Applied Thermal Engineering 67(1-2) 122-130

Wen J Yang H Wang S et al 2015 Experimental investigation on performance comparison for shell-and-tube heat exchangers with different baffles International Journal of Heat amp Mass Transfer 84 990-997

Wen J Yang H Wang S et al 2015 Numerical investigation on baffle configuration improvement of the heat exchanger with helical baffles Energy Conversion amp Management 89 438-448

Hou G Wang J and Layton A 2012 Numerical methods for fluid-structure interaction-a review Communications in Computational Physics 12(2) 337-377

Hu F Chen T Wu D et al 2013 ldquoComputation of stress distribution in a mixed flow pump based on fluid-structure interaction analysisrdquo 6th International Conference on Pumps and Fans with Compressors and Wind turbines Beijing China Vol52

Simoneau J Sageaux T Moussallam N et al 2011 Fluid structure interaction between rods and a cross flow ndash Numerical approach Nuclear Engineering amp Design 241(11) 4515-4522

Yan K Ge P Bi W et al 2010 Vibration characteristics of fluid-structure interaction of conical spiral bundle Journal of Hydrodynamics 22(1) 121-128

Chen K Xie Y Ming Y et al 2015 Effects of different helix angles on performance of folded helical baffle heat exchanger Chemical Engineering 43(4) 26-28



METHODS The geometry construction of STHXs with plain helical baffles fold helical baffles and segmental baffles are shown in Figure 1The shell diameter of STHXs is 250 mm and tube bundle is 1250 mm in length There are 40 tubes with the diameter of 19 mm which are arranged squarely with the tube pitch of 25 mm Besides 12 spacer tubes are set to fix baffles and increase flow disturbance in the shell side The thickness helical angle and overlapped degree of shell-and-tube heat exchanger with helical baffles are respectively 6mm 18deg and 50

Figure 1 Tube bundle of STHEs with different baffles

Using indirect thermal stress calculation method based on thermal fluid-structure interaction it is convenient to import bundle temperature form fluid dynamics to solid dynamics for mechanical analysis Due to the temperature gradient external constraints or internal deformation compatibility requirements the additional stress namely thermal stresses is generated Solving the thermal stress according to thermoelastic theory it needs to satisfy basic hypothesis such as material uniformity continuity completely elasticity isotropy and small deformation Hence governing equations mainly include fluid dynamics equations and solid mechanics equations

As the physical model depicted before there are three domains in shell-and-tube heat exchanger two fluid domains (heat-conducting oil in shell side and water in tube side) and the solid domain (tube bundle) Hexahedral grids were used in the tube side while unstructured grids were used in the shell side and solid domain To improve the accuracy of the calculation adaptive grid technique was used and grid independence was verified Figure 2 presents the local grid of STHXs with fold helical baffle and Table 1 shows the detailed data of grids

The RNG k-ε model is adopted in the simulation The boundary conditions of tube-shell side inlet and outlet were set as velocity inlet and pressure outlet respectively The shell-inlet temperature was 33715 K The tube-inlet velocity was 118m∙s-1 and temperature was 30315 K Non-slip impermeable and adiabatic boundary conditions were adopted on the wall except fluid-solid interface with coupled wall Pressure-Velocity coupling algorithm was SIMPLE and second-order upwind scheme was adopted for solving the mass momentum energy and turbulent kinetic energy equation The convergence criterion was that the normalized residuals are less than 1times10-4 for all equations In the solid domain material was structural steel Density is 7854 kgm-3 heat conductivity is 605 Wm-1K-1 specific heat capacity is 434 Jkg-1K-1 and the allowable stress is 147 MPa when temperature is in the range of 30~70

Figure 2 Local grid of heat exchanger with fold baffle

Table 1 Mesh details and metrics

Baffles type

Elements Average skewness

Average element quality

Average orthogonal quality

Plain 25128983 023577 083009 085112

Fold 19895942 024684 082391 084575

Segmental 26227443 022724 083748 085654

The numerical results compared with the experimental data for the shell-and-tube heat exchangers with plain helical baffles where helical angle was 18deg and the overlap was 50 from the reference [Chen et al 2015] as shown in Figure 3 The figure shows that simulated and experimental values agreed well The maximum relative error of pressure drop in inlet and outlet was less than 15 with an average value of 147 Hence it can be concluded that the numerical method is reliable At the same time the numerical pressure drop was less than the experimental values The deviations may attribute to some simplification made in the physical model and some un-avoidable measurement error



12 14 16 18 20 22 24 26 28 30 325000

10000

15000

20000

25000

30000

35000

∆P

Pa

V m3sdoth-1



experimental data



12 14 16 18 20 22 24 26 28 30 32

5000

10000

15000

20000

25000

30000

35000

40000

45000

∆P

Pa

Vm3sdoth-1









12 14 16 18 20 22 24 26 28 30 32200

250

300

350

400

450

K W

sdotm-2

sdotK-1

V m3sdoth-1




12 14 16 18 20 22 24 26 28 30 32210

215

220

225

230

235

240

Nusdotf -

13

V m3sdoth-1


1124

1126

1128

1130

1132

1134

1136

Segmental baffle

Nusdotf

-13





12 14 16 18 20 22 24 26 28 30 32

106

108

110

112

114

116

σ e M

Pa

V m3sdoth-1



Volume flow rate






0 1 2 3 4 5 6

44

48

52

56

60

64

σ M

Pa

tmm


(a) Plain baffle

0 1 2 3 4 5 640

42

44

46

48

50

52

54

56

σ M

Pa

tmm


(b) Fold baffle

0 1 2 3 4 5 6

42

43

44

45

46

47

48

σ M

Pa

tmm






Plain 44782 56862

Fold 41927 52134






































12 14 16 18 20 22 24 26 28 30 325000

10000

15000

20000

25000

30000

35000

∆P

Pa

V m3sdoth-1



experimental data



12 14 16 18 20 22 24 26 28 30 32

5000

10000

15000

20000

25000

30000

35000

40000

45000

∆P

Pa

Vm3sdoth-1









12 14 16 18 20 22 24 26 28 30 32200

250

300

350

400

450

K W

sdotm-2

sdotK-1

V m3sdoth-1




12 14 16 18 20 22 24 26 28 30 32210

215

220

225

230

235

240

Nusdotf -

13

V m3sdoth-1


1124

1126

1128

1130

1132

1134

1136

Segmental baffle

Nusdotf

-13





12 14 16 18 20 22 24 26 28 30 32

106

108

110

112

114

116

σ e M

Pa

V m3sdoth-1



Volume flow rate






0 1 2 3 4 5 6

44

48

52

56

60

64

σ M

Pa

tmm


(a) Plain baffle

0 1 2 3 4 5 640

42

44

46

48

50

52

54

56

σ M

Pa

tmm


(b) Fold baffle

0 1 2 3 4 5 6

42

43

44

45

46

47

48

σ M

Pa

tmm






Plain 44782 56862

Fold 41927 52134







































12 14 16 18 20 22 24 26 28 30 32200

250

300

350

400

450

K W

sdotm-2

sdotK-1

V m3sdoth-1




12 14 16 18 20 22 24 26 28 30 32210

215

220

225

230

235

240

Nusdotf -

13

V m3sdoth-1


1124

1126

1128

1130

1132

1134

1136

Segmental baffle

Nusdotf

-13





12 14 16 18 20 22 24 26 28 30 32

106

108

110

112

114

116

σ e M

Pa

V m3sdoth-1



Volume flow rate






0 1 2 3 4 5 6

44

48

52

56

60

64

σ M

Pa

tmm


(a) Plain baffle

0 1 2 3 4 5 640

42

44

46

48

50

52

54

56

σ M

Pa

tmm


(b) Fold baffle

0 1 2 3 4 5 6

42

43

44

45

46

47

48

σ M

Pa

tmm






Plain 44782 56862

Fold 41927 52134








































0 1 2 3 4 5 6

44

48

52

56

60

64

σ M

Pa

tmm


(a) Plain baffle

0 1 2 3 4 5 640

42

44

46

48

50

52

54

56

σ M

Pa

tmm


(b) Fold baffle

0 1 2 3 4 5 6

42

43

44

45

46

47

48

σ M

Pa

tmm






Plain 44782 56862

Fold 41927 52134





































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