The Experts below are selected from a list of 56445 Experts worldwide ranked by ideXlab platform
Pongjet Promvonge - One of the best experts on this subject based on the ideXlab platform.
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thermal characterization in a circular tube fitted with inclined horseshoe Baffles
Applied Thermal Engineering, 2015Co-Authors: Pongjet Promvonge, Sombat Tamna, Monsak Pimsarn, Chinaruk ThianpongAbstract:Abstract In the present study, the influence of inclined horseshoes Baffles placed repeatedly in a tubular heat exchanger on heat transfer rate, friction factor and thermal enhancement factor are experimentally determined. The horseshoe baffle elements with an inclination angle of 20° were inserted periodically into the test tube at three different baffle-pitch ratios ( P R = 0.5, 1.0 and 2) and -width or blockage ratios ( B R = 0.1, 0.15 and 0.2). The experiment was conducted in the test tube having a uniform heat-fluxed wall by varying turbulent airflow to obtain Reynolds number in a range of 5300–24,000. The experimental results revealed that the tube fitted with inclined horseshoes Baffles provides considerable improvement of the heat transfer rate over the plain tube around 92–208% while the friction factor is increased at about 1.76–6.37 times. To access the real benefits for the inclined horseshoes Baffles inserted in plain tube, thermal performance factor is examined and found to be in the range of 1.34–1.92 at which the maximum obtained at P R = 0.5 and B R = 0.1 is considerably higher than that for published inserted devices. Correlations for Nusselt number and friction factor for the oblique horseshoe-baffled tube are also proposed.
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experimental and numerical study on heat transfer enhancement in a channel with z shaped Baffles
International Communications in Heat and Mass Transfer, 2012Co-Authors: Parkpoom Sriromreun, Chinaruk Thianpong, Pongjet PromvongeAbstract:Abstract The influence of baffle turbulators on heat transfer augmentation in a rectangular channel has been investigated experimentally and numerically. In the experiment, the Baffles are placed in a zigzag shape (Z-shaped baffle) aligned in series on the isothermal-fluxed top wall, similar to the absorber plate of a solar air heater channel. The aim at using the Z-Baffles is to create co-rotating vortex flows having a significant influence on the flow turbulence intensity leading to higher heat transfer enhancement in the tested channel. Effects of the Z-baffle height and pitch spacing length are examined to find the optimum thermal performance for the Reynolds number from 4400 to 20,400. The Z-Baffles inclined to 45° relative to the main flow direction are characterized at three baffle- to channel-height ratios (e/H = 0.1, 0.2 and 0.3) and baffle pitch ratios (P/H = 1.5, 2 and 3). The experimental results show a significant effect of the presence of the Z-baffle on the heat transfer rate and friction loss over the smooth channel with no baffle. The Nusselt number, friction factor and thermal performance enhancement factor for the in-phase 45° Z-Baffles are found to be considerably higher than those for the out-phase 45° Z-baffle at a similar operating condition. The in-phase 45° Z-baffle with larger e/H provides higher heat transfer and friction loss than the one with smaller e/H while the shorter pitch length yields the higher Nu, f and TEF than the larger one. The numerical work is also conducted to investigate the flow friction and heat transfer behaviors in the channel mounted with the 45° Z-Baffles, and the numerical results are found in good agreement with experimental data.
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laminar periodic flow and heat transfer in square channel with 45 inline Baffles on two opposite walls
International Journal of Thermal Sciences, 2010Co-Authors: Pongjet Promvonge, Somchai Sripattanapipat, Sutapat KwankaomengAbstract:Abstract A numerical investigation has been carried out to examine laminar flow and heat transfer characteristics in a three-dimensional isothermal wall square channel with 45°-angled Baffles. The computations are based on the finite volume method, and the SIMPLE algorithm has been implemented. The fluid flow and heat transfer characteristics are presented for Reynolds numbers based on the hydraulic diameter of the channel ranging from 100 to 1000. To generate a pair of mainstreamwise vortex flows through the tested section, Baffles with an attack angle of 45° are mounted in tandem and inline arrangement on the lower and upper walls of the channel. Effects of different baffle heights on heat transfer and pressure loss in the channel are studied and the results of the 45° inline baffle are also compared with those of the 90° transverse baffle and the 45° staggered baffle. It is apparent that in each of the main vortex flows, a pair of streamwise twisted vortex (P-vortex) flows created by the 45° baffle exist and help to induce impinging flows on a sidewall and wall of the baffle cavity leading to drastic increase in heat transfer rate over the channel. In addition, the rise in the baffle height results in the increase in the Nusselt number and friction factor values. The computational results reveal that numerical results of both the 45° inline and staggered Baffles are nearly the same. The optimum thermal enhancement factor is at the 45° baffle height of 0.2 times of the channel height for both arrays. The maximum thermal enhancement factor of the 45° baffle in the Re range studied is found to be about 2.6 or twice higher than that of the 90° transverse baffle.
Joelle Aubin - One of the best experts on this subject based on the ideXlab platform.
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Optimization of methyl ester production from waste cooking oil in a batch tri-orifice oscillatory baffled reactor
Fuel Processing Technology, 2017Co-Authors: Masoud Dehghani Soufi, Barat Ghobadian, Gholamhassan Najafi, Seyyed Mohammad Mousavi, Joelle AubinAbstract:Transesterification of vegetable oils is a common route for the production of biodiesel. This reaction is a slow mass transfer limited reaction that has been shown to benefit from process intensification reactors such as the Oscillatory Baffled Reactor (OBR). The use of waste cooking oil as a resource is an attractive alternative to other virgin vegetable oils that will enable the capital costs of biodiesel production to be largely decreased, thereby making biodiesel an affordable and competitive fuel. In this study, optimization of biodiesel, or fatty acid methyl ester (FAME) production from waste cooking oil (WCO) was investigated using a batch OBR (diameter = 0.06 m, height = 0.55 m) with multi-orifice Baffles, which have been recommended for scale-up. Response Surface Methodology (RSM) was applied to study the effects and interaction of different operating parameters: oscillation frequency (in the range 2.4–4.9 Hz), inter-baffle spacing (in the range 0.05–0.09 m) and reaction temperature (in the range 40–60 °C). It was found that temperature is the main factor influencing reaction yield and the interaction between temperature and oscillation frequency is non-negligible. Inter-baffle spacing does not, however, have a significant effect on the reaction. This is different from the design recommendations of OBRs in the literature, which were originally developed for single orifice Baffles. An optimal reaction yield of 81.9% was obtained with an oscillation frequency of 4.1 Hz and an inter-baffle spacing of 5 cm (i.e. approximately 1.5de) at a temperature of 60 °C. However, similar reaction yields could be obtained for different values of inter-baffle spacing.
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hydrodynamics and mixing in continuous oscillatory flow reactors part i effect of baffle geometry
Chemical Engineering and Processing, 2016Co-Authors: Alex Mazubert, David F Fletcher, Martine Poux, Joelle AubinAbstract:Abstract Time-dependent laminar flow in a continuous oscillatory baffled reactor has been studied using Computational Fluid Dynamics. The effect of baffle geometry on pressure drop, energy dissipation as well as the instantaneous flow and shear strain rate fields has been investigated for five different geometries, namely single orifice Baffles, disc-and-donut Baffles and three novel variations of helical blades. All designs show complex flow behaviour and the formations of vortices due to both flow blockage and flow reversal with various amounts of pressure drop and energy dissipation. However, it is clearly difficult to conclude on the impact of baffle design on the performance of the reactor with velocity, shear strain rates and vorticity alone. Part II of the paper therefore presents and exploits alternative quantitative measures to better quantify reactor performance.
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Hydrodynamics and mixing in continuous oscillatory flow reactors—Part II: Characterisation methods
Chemical Engineering and Processing: Process Intensification, 2016Co-Authors: Alex Mazubert, Martine Poux, David Fletcher, Joelle AubinAbstract:This work presents and exploits quantitative measures to better quantify the performance of oscillatory baffled reactors, being complementary to simple vector plots and shear strain rate fields. Novel performance criteria, including radial and axial fluid stretching and mixing, as well as the shear strain rate history of fluid elements have been developed and used to compare the performance of five different baffle designs, namely single orifice Baffles, disc-and-donut Baffles and three novel variations of helical blades. Analysis of residence time distributions has also been used to evaluate the geometries. The performance measures highlight that the disc-and-donut Baffles can provide significant shear strain rates, which could be useful for multiphase applications, but also significant axial dispersion that is comparable with that for the single orifice Baffles. The results also suggest that helical blade designs could be promising for decreasing axial dispersion, whilst maintaining significant levels of shear strain rate.
Alvaro Ruizpardo - One of the best experts on this subject based on the ideXlab platform.
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numerical and experimental study of the heat transfer and hydraulic performance of solar air heaters with different baffle positions
Renewable Energy, 2020Co-Authors: Charafeddine Bensaci, Abdelhafid Moummi, Francisco Jose Sanchez De La Flor, Enrique Angel Rodriguez Jara, Alejandro Rinconcasado, Alvaro RuizpardoAbstract:Abstract This study presents the results of a numerical and experimental study of the position of the Baffles in a solar air heater in order to improve its thermal and hydraulic performance. The numerical study was performed on four cases corresponding to different placements of Baffles with Reynolds numbers ranging from 2370 to 8340. The experimental model of the solar air heater was designed, manufactured and used for the validation of the numerical model. The new baffle placements show that effective thermo-hydraulic performance is not just a function of the shape or changes in the geometric parameters of the Baffles. The correct placement of Baffles dramatically improves the thermo-hydraulic performance of solar air heaters. The effect of baffle positions on local convective heat transfer coefficients has been discussed. The optimum thermo-hydraulic performance factor is achieved in the case where the Baffles are located in the first part of air channel which occupies 50% of the solar air heater.
Yaping Chen - One of the best experts on this subject based on the ideXlab platform.
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Numerical study on performances of small incline angle helical baffle electric heaters with axial separation
Applied Thermal Engineering, 2017Co-Authors: Yaping Chen, Shifan YangAbstract:Abstract To minimize the abrasion of sharp-corners of holes of inclined Baffles manufactured by 2D laser beam cutting machine on the tubes, the application of axial separation with small inclined angle helical Baffles is a simple alternate, which creates greater helix pitch for suitable cross section area. Numerical simulation on the flow and thermal performances were conducted on three axial separation helical baffle electric heaters with equivalent angles 15°, 20° and 25° using 10° inclined Baffles, three normal helical baffle ones and two segment baffle ones spanned respectively 200 and 250 mm. Each electric heater comprises 27 U-tubes on equilateral triangle layout with nine one-plus-two units. The secondary flow imposed plug flow pattern and leakage flow were demonstrated for helical schemes. The axial separation helical baffle schemes have obvious merits in the heat transfer coefficient, comprehensive index and the temperature uniformity of the electric heating tubes over those of the segment baffle ones. The average heat transfer coefficient and the comprehensive index ( h ·Δ p −1/3 ) of the modified axial separation helical scheme with equivalent angle 20° using 10° Baffles are respectively 37.8% and 26.0% higher while its average tube wall temperature is 95.6 K lower than those of the segment scheme spanned 200 mm.
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An efficient and low resistant circumferential overlap trisection helical baffle heat exchanger with folded Baffles
Energy Conversion and Management, 2016Co-Authors: Cong Dong, Youqu Zheng, Yange Suo, Yaping ChenAbstract:Abstract An efficient and low resistant circumferential overlap trisection helical baffle shell-and-tube heat exchanger with folded Baffles (cothHXf) is presented. It is a modified trisection helical baffle heat exchanger with folded helical Baffles for setting rods-and-spanning sleeves. It not only inherits all the merits of circumferential overlap helical baffle scheme, but also adds many additional advantages, such as supporting the inclined Baffles with the least rods, simplifying the manufacturing process of spanning tubes and effectively inhibiting the reverse leakage at triangular areas between adjacent Baffles. The improved flow characteristic and heat transfer enhancement mechanism of this heat exchanger were numerically investigated in comparison with conventional segmental Baffles shell-and-tube heat exchanger (segHX). The flow fields within triangular area of adjacent Baffles and nearby regions were depicted. The impacts of the folded Baffles on shell-side helical flow, secondary vortex flow, and leakage pattern were analyzed. The distribution configurations of fields of velocity, pressure, temperature and local heat flow rate were revealed. The results show that the heat transfer performance and comprehensive performance evaluation indexes of the cothHXf are much better than those of the segHX while the pressure drop of the cothHXf is much lower than that of the segHX. The numerical simulation results of vivid distributions of flow and thermal fields of the cothHXf can provide theoretical basis for an engineering design and popularized industrial application of the new type heat exchangers.
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Performances of helical baffle heat exchangers with different baffle assembly configurations
The Canadian Journal of Chemical Engineering, 2015Co-Authors: Cong Dong, Yaping ChenAbstract: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.
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Comparison of heat transfer performances of helix baffled heat exchangers with different baffle configurations
Chinese Journal of Chemical Engineering, 2015Co-Authors: Cong Dong, Yaping ChenAbstract:Abstract Numerical simulations were performed on flow and heat transfer performances of heat exchangers having six helical Baffles of different baffle shapes and assembly configurations, i.e. , two trisection baffle schemes, two quadrant baffle schemes, and two continuous helical baffle schemes. The temperature contour or the pressure contour and velocity contour plots with superimposed velocity vectors on meridian, transverse and unfolded concentric hexagonal slices are presented to obtain a full angular view. For the six helix baffled heat exchangers, the different patterns of the single vortex secondary flow and the shortcut leakage flow were depicted as well as the heat transfer properties were compared. The results show that the optimum scheme among the six configurations is a circumferential overlap trisection helix baffled heat exchanger with a baffle incline angle of 20° (20°TCO) scheme with an anti-shortcut baffle structure, which exhibits the second highest pressure drop Δ p o , the highest overall heat transfer coefficient K , shell-side heat transfer coefficient h o and shell-side average comprehensive index h o /Δ p o .
Charafeddine Bensaci - One of the best experts on this subject based on the ideXlab platform.
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numerical and experimental study of the heat transfer and hydraulic performance of solar air heaters with different baffle positions
Renewable Energy, 2020Co-Authors: Charafeddine Bensaci, Abdelhafid Moummi, Francisco Jose Sanchez De La Flor, Enrique Angel Rodriguez Jara, Alejandro Rinconcasado, Alvaro RuizpardoAbstract:Abstract This study presents the results of a numerical and experimental study of the position of the Baffles in a solar air heater in order to improve its thermal and hydraulic performance. The numerical study was performed on four cases corresponding to different placements of Baffles with Reynolds numbers ranging from 2370 to 8340. The experimental model of the solar air heater was designed, manufactured and used for the validation of the numerical model. The new baffle placements show that effective thermo-hydraulic performance is not just a function of the shape or changes in the geometric parameters of the Baffles. The correct placement of Baffles dramatically improves the thermo-hydraulic performance of solar air heaters. The effect of baffle positions on local convective heat transfer coefficients has been discussed. The optimum thermo-hydraulic performance factor is achieved in the case where the Baffles are located in the first part of air channel which occupies 50% of the solar air heater.
