Shell-side Heat Transfer Research Articles

Performance comparison for oil-water heat transfer of circumferential overlap trisection helical baffle heat exchanger

The performance tests were conducted on oil–water heat transfer in circumferential overlap trisection helical baffle heat exchangers with incline angles of 12°, 16°, 20°, 24° and 28°, and compared with a segmental baffle heat exchanger. The results sh ow that the shell side heat transfer coefficient h o and pressure drop Δpo both increase while the comprehensive index h o/Δpo decreases with the increase of the mass flow rate of all schemes. And the shell side heat transfer coefficient, pressure drop and the comprehensive index h o/Δpo decrease with the increase of the baffle incline angle at a certain mass flow rate. The average values of shell side heat transfer coefficient and the comprehensive index h o/Δpo of the 12° helical baffled scheme are above 50% higher than th ose of the segmental one correspondingly, while the pressure drop value is very close and the ratios of the average values are about 1.664 and 1.596, respectively. The shell-side Nusselt number Nu o and the comprehensive index Nu o·Eu zo -1 increase with the increase of Reynolds number of the shell side axial in all schemes, and the results also demonstrate that the small incline angled helical scheme has better comprehensive performance.

Modeling for Shell-Side Heat Transfer Coefficient and Pressure Drop of Helical Baffle Heat Exchangers

This study has suitably modified the existing heat transfer and pressure drop correction factors of the modified Bell–Delaware method used for heat exchangers with segmental baffles, taking into consideration the helical baffle geometry. These correction factors are presented in parametric formulas based on the Taborek presented procedure for segmental baffles. These formulas are functions of the geometrical and physical parameters of discontinuous helical baffles. In addition, the parametric formulas are presented graphically based on the Stehlik method. The correction design method proposed by Stehlik for the helical baffle is presented in detail and a theoretical model for shell-side heat transfer and pressure drop is developed. In general, the results show that the present model matches more closely with the graphically proposed correction factors of Stehlik. In order to calculate the shell-side heat transfer coefficient and pressure drop using the present method, a computational code has been developed by the authors. In addition, in order to examine the validity, the results of the code for a case study are compared with the results obtained from EXPRESS software and experimental formulas presented by Zhang. The results of comparison show that the proposed method is accurate and can be used by designers confidently.

Numerical investigation on synthetical performance of heat transfer of planar elastic tube bundle heat exchanger

This paper studied the synthetical performance of heat transfer in the shell-side of planar elastic tube bundle heat exchanger using numerical simulation. The temperature distribution in shell-side was studied. The relation of average heat transfer coefficient, pressure drop and comprehensive heat transfer performance were also discussed considering varying Reynolds number and geometry parameters. Results demonstrate that the temperature distribution provides a possibility to improve heat transfer by arranging the tube bundle layout to produce a fully heated fluid within full-scale shell-side. For the effect of geometry parameter, tube pitch has a greater effect on heat transfer compared to the tube-row spacing. However, Reynolds number dominates the heat transfer and fluid flow in shell-side. As a result, a prediction correlation of average Nusselt number is developed based on Reynolds number using the multiple-regression analysis of MATLAB software. A quite outstanding comprehensive heat transfer performance can be obtained in the case of tube pitch 20mm. However, the high Reynolds number is more acceptable in the industry to enhance the heat transfer rate without considering the heat transfer difference caused by geometry parameter.

Numerical analysis on shell-side flow-induced vibration and heat transfer characteristics of elastic tube bundle in heat exchanger

Based on the sequential solution of bi-direction fluid-structure coupling method, the shell-side flow-induced vibration responses and the heat transfer characteristics of the elastic tube bundles in heat exchanger have been investigated in this paper. Taking into account the meshing convenience and computing efficiency, appropriate meshing strategy and step calculation method have been proposed. Effects of shell-side water inlet velocity on the flow-induced vibration responses and heat transfer characteristics of the elastic tube bundle have been discussed. The results indicate that the mainly vibration of each tube bundle induced by the shell-side fluid is the out-plane vibration. The vibration amplitudes of the two stainless steel blocks are basically consistent when the shell-side fluid inlet velocity is lower, and the vibration amplitude of the stainless steel block III is more intense when the shell-side fluid inlet velocity is higher. In addition, the heat transfer coefficient of each elastic tube bundle has increased significantly at low flow rate (or low Reynolds number) when the shell-side flow-induced the elastic tube bundle vibration.

Investigation on combined multiple shell-pass shell-and-tube heat exchanger with continuous helical baffles

A combined serial two shell-pass shell-and-tube heat exchanger (CSTSP-STHX) with continuous helical baffles has been proposed to improve heat transfer performance. This CSTSP-STHX separates the shell side into two individual shell passes. The inner shell pass is conventional segmental baffled, and the outer shell pass is continuous helical baffled. The working fluid flows through the outer and inner shell passes in sequence. The thermo hydraulic performances of CSTSP-STHX are experimentally compared with the double shell-pass shell-and-tube heat exchanger with segmental baffles (SG-STHX). The results show that the CSTSP-STHX gets greater shell-side heat transfer coefficient and pressure drop, furthermore it also has better heat transfer coefficient under the same pressure drop than those of the SG-STHX. Finally it should be emphasized that the leakage on annulus separator has to be as possible as reduced. The present studies are beneficial for the design and practical operation of CSTSP-STHX.

Experimental studies of shell-side fluid flow and heat transfer characteristics in a submerged combustion vaporizer

In this paper, an experimental apparatus was set up to study the two-phase mixture flow and heat transfer over a horizontal tube bundle on the shell-side of the submerged combustion vaporizer (SCV). The influences of the static water height, superficial flue gas velocity and heat load on the heat transfer characteristics were systematically examined. The experimental results revealed some interesting observation of the SCV, such as the circulation flow of water bath accompanying a great deal of gas bubbles and the highly thermal efficiency due to the direct-contact heat transfer between the highly turbulent two-phase mixture and staggered tube bundles. Finally, based on the experimental data, a new dimensionless, semi-theoretical empirical correlation was developed for two-phase mixture convection heat transfer over the staggered tube bundle on the shell-side of SCV. The discussion and correlation provided a framework for designing the SCV.

Experimental Performance Comparison of Shell-Side Heat Transfer for Shell-and-Tube Heat Exchangers with Different Helical Baffles

In this study, experiments were carried out to study the effects of baffle overlap proportion on the shell-side flow resistance and heat transfer performance of the shell-and-tube heat exchangers with helical baffles (STHXsHB). Three STHXsHB with an overlap proportion of 10% and helix angles of 20°, 30°, and 40° were tested. Comparisons were made of the experimental data of the STHXsHB with the same helix angles but 50% overlap proportion. The theory of entransy dissipation was employed to evaluate the irreversible loss in STHXsHB with different helix angles and overlap proportions. The results indicated that both the baffle overlap proportion and the helix angle have a great effect on the shell-side flow resistance and heat transfer. For a given helix angle, the comprehensive performance of STHXsHB with small overlap proportion is always better than that with large overlap proportion at the same mass flow rate or Reynolds number on the shell side. However, for the same heat transfer area, working conditions, and helix angle, the STHXsHB with large baffle overlap proportion has less irreversibility in the heat exchange process, according to the theory of entransy dissipation. In addition, experimental results demonstrated that the configuration of the relatively large helix angle and baffle overlap proportion is the preferred alternative in STHXsHB.

Experimental investigation of a directionally enhanced DHX concept for high temperature Direct Reactor Auxiliary Cooling Systems

The use of Direct Reactor Auxiliary Cooling Systems (DRACSs) as a safety-related decay heat removal system for advanced reactors has developed historically through the Sodium Fast Reactor (SFR) community. Beginning with the EBR-II, DRACSs have been utilized in a large number of past and current SFR designs. More recently, the DRACS has been adopted for Fluoride Salt-Cooled High-Temperature Reactors (FHRs) for similar decay heat removal functions. In this paper we introduce a novel directionally enhanced DRACS Heat Exchanger (DHX) concept. We present design options for optimizing such a heat exchanger so that shell-side heat transfer is enhanced in one primary coolant flow direction and degraded in the opposite coolant flow direction. A reduced-scale experiment investigating the hydrodynamics of a directionally enhanced DHX was built and the data collected is presented. The concept of thermal diodicity is expanded to heat exchanger technologies and used as performance criteria for evaluating design options. A heat exchanger that can perform as such would be advantageous for use in advanced reactor concepts where primary coolant flow reversal is expected during Loss-of-Forced-Circulation (LOFC) accidents where the ability to circulate coolant is compromised. The design could also find potential use in certain advanced Sodium Fast Reactor (SFR) designs utilizing fluidic diode concepts.

Heat transfer and performance analysis of nanofluid flow in helically coiled tube heat exchangers

In the present paper, heat transfer characteristics of Al2O3 nanofluid flow inside shell and helical tube heat exchangers are numerically investigated. The numerical computations are performed by using SST turbulence model as well as by implementing conjugate heat transfer from hot fluid in the tube to cold fluid in the shell. The thermo-physical properties of the fluids were considered to be temperature dependent. The coil-side Reynolds number, the shell-side Reynolds number and the Prandtl number ranged between 9000 and 36,000, 600 and 2600 and 2.2 and 8.3, respectively. The effects of nanoparticle volume concentration on the temperature of coil- and shell-side flows, heat transfer rate and convective heat transfer coefficients are presented. The results indicate that the presence of 0.2% and 0.3% nanoparticle volume concentration increases the mean heat transfer rate by approximately 14% and 18%, respectively. The results also show that with the increase in particle volume concentration the coil-side, shell-side and overall heat transfer coefficients enhance. It is indicated that for the same mass flow rate, the heat transfer rate of nanofluid enhances noticeably compared to water and it increases marginally with the further increase in the nanoparticle volume concentration. The performance of the heat exchanger was evaluated and the results reveal that the effectiveness enhances by decreasing the mass flow rate and increasing the particle volume concentration, tube diameter and coil diameter. Moreover, the performance index enhances by increasing the tube diameter and reducing the coil diameter.

CFD simulations of shell-side flow in a shell-and-tube type heat exchanger with and without baffles

Shell-and-tube heat exchanger has been extensively used in industrial and research fronts for more than a century. However, most of its design procedures are based on empirical correlations extracted from experimental data of long length shell and tube heat exchanger. In this paper, an attempt has been made to investigate the complex flow and temperature pattern in such a short shell and tube type heat exchanger, with and without baffles in the shell side. Heat exchangers of length by hydraulic diameter ratio between 7<L/Dh<21(0.15m<DS<0.6m) for unbaffled and L/Dh<7(DS=0.09m) for baffled heat exchangers are analysed using CFD code OpenFOAM-2.2.0 for different mass flow rates. It was observed that the cross flow near the nozzle region has a significant contribution towards the heat transfer, hence the conventional heat transfer correlations do not apply to these short heat exchangers. Furthermore, a sensitivity study of turbulence models was performed and it was observed that the standard k–ε model gives best results for the velocity profile as well as heat transfer, provided average y+ of the first node adjacent to the heat transfer surface is maintained greater than 15. The commonly used boundary conditions at the exit are not realistic, as it tends to give either incorrect flow and temperature fields, or the solution was found to diverge. Through a sensitivity study of the exit length, it was found that exit length to shell side velocity ratio of 2.5 is required for proper convergence. Finally the effect of flow field on shell side heat transfer coefficient and a comparison with analytical methods are presented.

Numerical simulation on the performance of trisection helical baffle heat exchangers with small baffle incline angles

ABSTRACTNumerical simulation was conducted on oil–water heat transfer in five circumferential overlap trisection helical baffle shell–and–tube heat exchangers (cothSTHXs) with 16 tubes and incline angles of 12°, 16°, 20°, 24°, and 28° and a segmental baffle heat exchanger of the identical tube layout for comparison under laminar flow calculation conditions. The local images represent shell-side flow patterns, and heat transfer properties are presented showing the detailed “secondary vortex flow” and “shortcut leakage flow” patterns to explain the different characteristics of the six schemes. The simulation curves of the heat transfer coefficient and pressure drop are compared with those of the experimental ones, with satisfactory agreement. The average values of the shell-side heat transfer coefficient and the comprehensive index ho/Δpo of the 12° helical scheme are respectively 47% and 51% higher than those of the segmental baffle scheme with about the same pressure drop.

Investigations on the Condensation Heat Transfer Performance of Stainless Steel Edge-Shaped Finned Tubes

The third-generation enhanced heat transfer technologies, such as three-dimensional fin and dimple, are still important means of improving energy efficiency. This paper analyzes the condensation heat transfer performances of three edge-shaped finned tubes that were fabricated using the plowing–extruding process. Experimental results show that the shell-side heat transfer coefficient decreases with increases of heat flux and temperature difference between wall and vapor. The edge-shaped finned tubes exhibit better heat transfer performance than smooth tubes. At the identical temperature difference between the wall and the vapor, the shell-side heat transfer coefficient of the edge-shaped finned tubes is approximately 1.7–2.6 times larger than that of the smooth tubes. At the identical temperature difference between the wall and the vapor, the shell-side heat transfer coefficient of edge-shaped finned tubes is also higher than the reported value in the literature. The excellent performance of the edge-shaped finned tubes comes from the coordination of enhancement from the three-dimensional fins, dimples, and grooves. Finned tubes with grooves fabricated along the left direction have higher and thinner fins and therefore show better heat transfer performance. The shell-side heat transfer coefficients of edge-shaped finned tubes increase with plowing–extruding depth and feed increasing.

Effect of Coil Torsion on Heat Transfer and Pressure Drop Characteristics of Shell and Coil Heat Exchanger

The present work introduces an experimental study of horizontal shell and coil heat exchangers. Characteristics of the convective heat transfer in this type of heat exchangers and the friction factor for fully developed flow through their helically coiled tube (HCT) were investigated. The majority of previous studies were performed on HCTs with isothermal and isoflux boundary conditions or shell and coil heat exchangers with small ranges of HCT configurations and fluid-operating conditions. Here, five heat exchangers of counterflow configuration were constructed with different HCT torsions (λ) and tested at different mass flow rates and inlet temperatures of both sides of the heat exchangers. In total, 295 test runs were performed from which the HCT-side and shell-side heat transfer coefficients were calculated. Results showed that the average Nusselt numbers of both sides of the heat exchangers and the overall heat transfer coefficient increase by decreasing coil torsion. At lower and higher HCT-side Reynolds number (Ret), the average increase in the HCT-side average Nusselt number (Nu¯t) is of 108.7% and 58.6%, respectively, when λ decreases from 0.1348 to 0.0442. While, at lower and higher shell-side Reynolds number (Resh), the average increase in the shell-side average Nusselt number (Nu¯sh) is of 173.9% and 69.5%, respectively, when λ decreases from 0.1348 to 0.0442. In addition, a slight increase of 6.4% is obtained in the HCT Fanning friction factor (fc) at lower Ret when λ decreases from 0.1348 to 0.0442, and this effect vanishes with increasing Ret. Furthermore, correlations for Nu¯t, Nu¯sh, and fc are obtained.

Conjugate heat and mass transfer in a skewed flow hollow fiber membrane bank used for liquid desiccant air dehumidification

Hollow fiber membrane tube bank has been increasingly used in various industries. Fluid flow in shell side is often projected at an impinging angle to the fiber bank due to the complicate structure of heat mass exchangers. However most previous researches concerned only on two ideal flow conditions, pure parallel flow or pure cross flow. The effects of skewed flow were not mentioned. In this research, fluid flow and transport phenomena in a skewed flow hollow fiber membrane bank for liquid desiccant air dehumidification are investigated. The boundary conditions on the membrane surfaces are determined by coupled heat and moisture transfer from tube side, through the membranes, and to the shell side. The governing differential equations of continuity, momentum, energy and concentration are solved by a finite volume method to obtain the shell-side convective heat and mass transfer coefficients, which are then experimentally validated. The influences of skewed angles from 0° to 90° on the heat mass transfer and friction properties are investigated. Correlations are proposed for the prediction of convective transfer coefficients and friction factors at different skewed angles.

A Numerical Study on the Shell-Side Turbulent Heat Transfer Enhancement of Shell-and-Tube Heat Exchanger with Trefoil-Hole Baffles

Shell-and-tube heat exchangers with trefoil-hole baffles are new type heat transfer devices and widely used in nuclear power system due to their special advantages, with the fluid flowing longitudinally on the shell side. However, very few related academic literature are available. In order to obtain an understanding of the underlying mechanism of shell-side thermal augmentation, a CFD model including inlet and outlet nozzles is proposed in the present study. Based on the RNG k-ɛ model, numerical investigations on shell-side fluid flow and heat transfer are conducted by using commercial CFD software FLUENT14.0. The results show that the fluid is fully developed after the first trefoil-hole baffle. The heat transfer coefficient and pressure drop vary periodically along the axial direction. Fluid velocity increases gradually and the jet flow forms in the region near baffles. The secondary flow is also produced on the two sides of baffles when the fluid flows through trefoil-hole baffle. The jet flow and secondary flow can decrease the thickness of boundary layer and then enhance the heat transfer.

Improvisation of Shell Side Heat Transfer Coefficient in Shell and Tube Heat Exchangers using Different Configurations – A Mini Review

Improvisation of Shell Side Heat Transfer Coefficient in Shell and Tube Heat Exchangers using Different Configurations – A Mini Review

Experimental investigation on performances of trisection helical baffled heat exchangers for oil/water–water heat transfer

The trisection helical baffled shell-and-tube heat exchangers have structural features of more suitable to the equilateral triangular tube layouts and less baffle parts. In particular the circumferential overlap trisection helical baffled shell-and-tube heat exchangers are of anti-shortcut structure that accommodates one row tubes in each circumferential overlapped zone between adjacent baffles for dampening shortcut leakage. The performance tests were conducted on both oil–water and water–water heat transfer in heat exchangers with equilateral triangle tube layout of 16 tubes including five helical baffle schemes with incline angles of 12°, 16°, 20°, 24°, 28° and a segmental baffled one for comparison. The test results show that both the shell side heat transfer coefficient ho and pressure drop Δpo increase but the comprehensive index ho/Δpo decreases with the increase of the mass flow rate of all schemes; and that the shell side heat transfer coefficient, pressure drop and the comprehensive index ho/Δpo decrease with the increase of the baffle incline angle at certain mass flow rate, except that the curves of comprehensive index ho/Δpo of 12° and 16° helical baffle schemes are almost coincide. The average values of shell side heat transfer coefficient, the comprehensive index ho/Δpo of the 12° helical baffled scheme are about 50% higher than those of the segmental one with almost same pressure drop. The correlation equations for shell side Nusselt number and axial Euler number are presented varying with axial Reynolds number, Prandtl number and helical baffle incline angle.

Performances of helical baffle heat exchangers with different baffle assembly configurations

The flow and heat transfer characteristics of helical baffle heat exchangers with diverse inclined angles and baffles, but similar baffle pitch and tube layout, were numerically simulated, three using non‐continuous trisection baffles, two using non‐continuous quadrant baffles, and one using a continuous helical baffle. The results show that, under the same operating conditions, the 20°TCO (trisection circumferential overlap baffles with 20° inclined angle) structure can significantly enhance shell side heat transfer with strong Dean vortex “secondary flow“ and restrained V‐notch leakage, because the shapes of trisection baffles are very suitable to equilateral triangle tube layout and there is a row of tubes to dampen the leakage flow in each circumferential overlapped area of adjacent baffles. The shell side Nusselt Number Nuo and comprehensive index (Nuo/Euz,o1/3) of 20°TCO structure are 18.31 %, 25.82 %, 5.93 %, 6.36 %, and 15.04 %, and 15.43 %, 18.47 %, 5.30 %, 3.91 %, and 11.10 % higher than those of the 20°TEE (trisection end‐to‐end baffles with 20° inclined angle), 36.2°TMO (trisection middle overlap baffles with 36.2° inclined angle), 18°QCO (quadrant circumferential overlap baffles with 18° inclined angle), 18°QEE (quadrant end‐to‐end baffles with 18° inclined angle), and 18.4°CH (continuous helical baffle with 18.4° helical angle) structures, respectively.

Experimental study of effects of baffle helix angle on shell-side performance of shell-and-tube heat exchangers with discontinuous helical baffles

Flow resistance and heat transfer of several shell-and-tube heat exchangers with discontinuous helical baffles are experimentally studied and compared at the five helix angles of 8°, 12°, 20°, 30° and 40°. The second-law based thermodynamic analysis is employed to analyze the effects of baffle helix angle on the irreversible loss of heat exchangers. The results indicate that the shell-side pressure drop and heat transfer coefficient of the heat exchanger with smaller helix angle are higher than those with larger helix angle at a given shell-side volume flow rate. However, in the condition of the same shell-side Reynolds number, the flow resistance with larger helix angle is lower and the heat transfer performance is better. The heat exchanger with helical baffles at 40° helix angle presents the best comprehensive performance among the five testing heat exchangers. In the second-law thermodynamic comparisons, the irreversibility of heat exchanger is estimated by the theories of entropy generation and entransy dissipation. Experimental analysis shows that in the same heat transfer area and under the same working conditions, the shell-and-tube heat exchanger with smaller helix angle baffles produces less irreversibility in the heat exchange process. In addition, the heat exchangers with helical baffles are more effective under certain conditions of low shell-side Reynolds number.

Optimal nozzle spray cone angle for triangular-pitch shell-and-tube interior spray evaporator

The present study proposed a triangular-pitch shell-and-tube spray evaporator featuring an interior spray technique. In the proposed approach, the nozzle tubes are positioned within the tube bundle in such a way that the surface of each heater tube is sprayed simultaneously by two cooling sprays. As a result, the dry-out phenomenon is prevented, and thus the heat transfer performance is improved. An analytical expression is derived for the optimal spray cone angle for the proposed evaporator. It is shown that the optimal spray cone angle increases with an increasing diameter of the heater tubes, but decreases with an increasing distance between the heater tubes and nozzle tubes. The analytical expression for the optimal spray cone angle was validated by experimental spray tests using spray cone angles of 0°, 30°, 40°, 45° and 60°, respectively. It is shown that a good agreement exists between the experimental results for the optimal spray cone angle and the theoretical results. Furthermore, the experimental results confirm that the shell-side heat transfer coefficient obtained using the interior spray technique is significantly higher than that achieved in a conventional flooded-type evaporator over a wide range of surface heat fluxes.