Perforated Baffle Research Articles

Three-dimensional analysis of heat transfer in a channel provided with solid baffle, single and double perforation

PurposeThe purpose of this paper is to present a three-dimensional (3D) analysis of the laminar flow of air and the conjugate heat transfer in a pipe of rectangular cross-section with a solid or perforated deflector inserted on the lower wall.Design/methodology/approachTo this end, by using the finite volume method, the conservation equations for mass, momentum and energy are solved numerically. Two cases of “single and double” perforation were studied and compared with that of the solid case for a range of Reynolds numbers ranging from 140 to 840. The velocity and temperature profiles were plotted and interpreted on three different sections placed sequentially upstream, mid-stream and downstream of the deflector. Total heat exchange at the bottom wall, outlet fluid temperature, perforated PFE deflector performance and pressure loss is presented for different cases studied and for different Reynolds numbers.FindingsThe results show that although the perforated deflector improves the heat transfer, it also results in additional pressure losses; the study also showed the existence of a limiting velocity beyond which the perforation effect on the improvement of the heat exchange decreases until the same performance of the solid deflector is achieved.Originality/valueThe main originality of this work is to show a 3D analysis for a perforated baffle as heat exchanger application.

Thermal performance enhancement in perforated baffled annuli by nanoporous graphene non-Newtonian nanofluid

This study investigated the convective heat transfer and pressure drop of non-Newtonian nanoporous graphene nanofluids. The nanoporous graphene nanofluids were prepared using different concentrations of nanoparticles (i.e. 0.05, 0.1, and 0.2 wt%) in an aqueous solution of carboxymethyl cellulose, and the thermophysical and rheological properties were evaluated accordingly. Four types of circular perforated baffles with different hole numbers were designed and manufactured. The Nusselt number, friction factor, and thermal performance factor (TPF) were calculated for the nanofluid and the base fluid flows by installing the baffles and were compared to those of the plain annular tube. The measurements showed that adding 0.2 wt% nanoporous graphene to the base solution led to enhancements of 12.4 and 39.4% in the thermal conductivity and the average heat transfer coefficient, respectively. The results indicated that by simultaneously using non-Newtonian nanoporous graphene nanofluid and perforated circular baffles, the average TPF value could be enhanced by 29% in the studied turbulence regime. These significant conclusions can be exploited to design highly efficient thermal systems possessing much better thermal efficiency.

Experimental and numerical study of the effect of integrating plus-shaped perforated baffles to solar air collector in drying application

Solar thermal systems like solar water and solar air collectors (SCs) are generally used because of their simple structure and high thermal efficiency. Solar air collectors could be utilized in drying applications because they are easy applicable and economical. In this study, a novel parallel-pass SC with double baffles (PPSCDB), parallel-pass SC with baffles (PPSCB) and parallel-pass SC (PPSC) without baffle have been designed and tested for drying application. Baffles have been manufactured in plus-shaped and perforated to achieve high thermal performance. The performance of solar collectors has been analyzed numerically and experimentally. In addition, a drying chamber has been coupled with solar air collectors. Celery (Apium Graveolens L.) root has been dried as a product and dried samples’ quality has been analyzed experimentally. The experiments have been conducted at 0.009 kg/s and 0.011 kg/s air mass flow rates. According to the experimental findings, average thermal efficiencies of PPSC, PPSCB and PPSCDB are in the range of 62.10–66.32%, 65.72–69.62% and 71.12–75.11%, respectively. The highest instantaneous efficiency was obtained as 84.30% in higher mass flow rate in PPSCDB. Also, maximum deviation between experimental and numerical results was 9.5%.

Thermal performance investigation of a solar air heater having discrete V-shaped perforated baffles

In the present work, thermal performance of solar air heater (SAH) having discrete V-shaped perforated baffles as artificial roughness on absorber surface has been numerically investigated. The effect of relative blockage height (e/H) of proposed roughness on Nusselt number (Nu), friction factor (f) and thermo-hydraulic performance parameter (THPP) has been considered. Parametric investigation covers a range of roughness parameter viz. relative blockage height (e/H) from 0.3 to 0.6 and flow parameter, Reynolds number (Re) from 4000 to 18,000 at constant open area ratio of 23%, relative pitch ratio of 6 and angle of attack of 60○. Performance of SAH with proposed roughness has been compared with other roughness geometries investigated by other researchers. It is noticed that Nusselt number enhancement ratio (Nurat) and friction factor enhancement ratio (frat) are 4.24 and 14.73, respectively, and maximum values of THPP is found to be 2.24 at e/H = 0.4. Abbreviations: CFD: Computational fluid dynamics; LSCB: Least square cell based; RNG: Renormalisation group; SAH: Solar air heater; SIMPLE: Semi implicit method for pressure linked equation; THPP Thermo-hydraulic performance parameter

Performance Evaluation of Mesophilic Anaerobic Digestion System with Single and Double Perforated Plates

Biogasification of the Food-waste Leachate was carried out through the mesophilic anaerobic digesters with single and double perforated plates. The substrate which was Food-waste Leachate was slowly injected to the bottom of reactor for 30 minutes not to cause turbulence in the reactor during stagnation phase. The recirculation pumping rate to show plug flow within digester was determined by dye diffusion experiments. The anaerobic digesters and input substrate temperature were maintained at 39oC except for “Trial 2” which tried to have thermophilic digestion. The average methane productions were 0.28 Sm3 CH4/kg VS in digester with single perforated baffles (System A) and 0.31 Sm3 CH4/kg VS in digester with double perforated baffles (System B), respectively, which showed that double perforated baffles encouraged larger methane yield due to plug flow reaction by double perforated baffle.

Electrocoagulation as a green technology for phosphate removal from river water

Abstract The current study investigates the removal of phosphate from water using a new baffle plates aluminium-based electrochemical cell (PBPR) taking consideration the influence of key operating parameters. This new cell utilises perforated baffle plates as a water mixer rather than magnetic stirrers that require extra power to work. As this unit is new, a comprehensive study has been carried to assess it performance. This study also includes preliminary estimates of the reactor’s operating costs, the amount of H2 gas produced and the yieldable energy from it. SEM (scanning electron microscope) was used to investigate the influence of the electrocoagulation process on the morphology of the surface of aluminium electrodes, and an empirical model developed to reproduce the phosphate removal process. The results showed that 99% of phosphate was removed within 60 min of electrolysis at an initial pH (ipH) of 6, inter-electrode distance (ID) of 0.5 cm, current density (J) of 6 mA/cm2, initial concentration of phosphate (IC) of 100 mg/L, and minimum operating cost of 0.503 US $/m3. The electrochemical cell produced enough H2 gas to generate 4.34 kWh/m3 of power. Statistically, it was proved that the influence of the operating parameters on phosphate removal could be modelled with an R2 of 0.882, the influence of these operating parameters on phosphate removal following the order: t > J > I C > i p H > I D . Finally, SEM images showed that after several electrolysing runs, the Al anode became rough and nonuniform which could be related to the production of aluminium hydroxides.

Numerical study of a three-dimensional forced laminar flow in a channel equipped with a perforated baffle

The present work concerns a numerical study of a three-dimensional laminar flow in forced convection crossing a rectangular channel provided with a baffle attached on its lower wall. The conservation equations for mass, momentum, and energy are solved by the finite volume method based on the SIMPLE algorithm for pressure–velocity coupling scheme. The effect of the insertion of a perforated baffle at different perforation volumes was analyzed. The results presented show the temperature and velocity contours obtained for two different planes (XY and XZ) passing through the center of the baffle. The average friction coefficient, the average Nusselt number and the heat flux are presented for different perforation volumes of the baffle and for different Reynolds numbers. The study shows that although the solid baffle improves heat transfer, the use of a perforated baffle attached to the same position, further enhances heat transfer (from 0.03% to 14.52%), which provides, economically, a very good material reduction (from 5.18% to 82.96%) and mechanically, less flow resistance and therefore better performance.

Liquid Sloshing Suppression for Three-Phase Separators Installed on Floating Production Unit

In this study, a computational fluid dynamics model based on the volume of fluid (VOF) method is developed to simulate the dynamic sloshing response to external excitations. The modal analysis model based on the linear potential theory is established to predict natural sloshing frequencies and the corresponding mode shapes in three-phase separators. In addition, the effects of separator location, length-to-diameter ratio, oil/water level, porosity, and spacing of perforated baffles on the sloshing response are evaluated quantitatively. Furthermore, comprehensive approaches are proposed to mitigate the sloshing, like enhancing viscous damping effect, reducing the intensity of external excitation sources, and keeping away from the resonant frequencies. Finally, a practical application is carried out to display the optimal design of a three-phase separator. The results show that three-phase separators should be located as close as possible to the center of rotation (COR) of the floating production units (FPU). The length-to-diameter ratio is recommended to be no greater than three. Once the fluids can be separated to reach their respective interfaces, the liquid level should be increased as high as possible, whereas the water level should be lowered as far as possible. There is an almost inversely linear relationship between the antisloshing performance of a perforated baffle and its porosity. The antisloshing performance is attenuated rapidly when the spacing distance of a pair of baffles exceeds a specific range. This research extends the existing scope of sloshing suppression approaches and provides useful guidance in the design of FPU-based three-phase separators.

Effect of the perforation design on the fluid flow and heat transfer characteristics of a plate fin heat exchanger

Three dimensional numerical simulations are carried out to explore the performance of vortex generators in a plate fin heat exchanger. Rectangular and perforated wings are used as vortex generators to enhance the heat transfer rates. A comparison is made between the performances of a plate fin with and without baffles. When the heat exchanger is equipped with baffles, the efficiency of two configurations was compared: a baffle with and without perforation. Also, the effects of the perforation shape were studied. It concerns three cases: rectangular, triangular and circular. Validation of our numerical results with the available experimental data has revealed a satisfactory agreement. The obtained results show that the baffled cases perform better than the unbaffled one. The performance factor is found to be higher in the perforated baffle than the baffle without perforation. Compared to the unbaffled case, the maximum thermal performance factor (TPF) of 2.14 was obtained with the circular perforated baffle, followed by the rectangular perforated baffle (TPF = 1.57), triangular baffle (TPF = 1.46) and finally the baffle without perforation (TPF = 1.41). At the end of paper, new correlations for the prediction of friction factor and Nusselt number depending on Reynolds number and the shape of perforation in baffles are developed.

Removal of phosphate from River water using a new baffle plates electrochemical reactor

During the last 50 years, the human activities have significantly altered the natural cycle of phosphate in this planet, causing phosphate to accumulate in the freshwater ecosystems of some countries to at least 75% greater than preindustrial levels, which indicates an urgent need to develop efficient phosphate treatment methods. Therefore, the current study investigates the removal of phosphate from river water using a new electrochemical cell (PBPR). This new cell utilises perforated baffle plates as a water mixer rather than magnetic stirrers that require power to work. This study investigates the influence of key operational parameters such as initial pH (ipH), current density (?), inter-electrode distance (ID), detention time (t) and initial phosphate concentration (IC) on the removal efficiency, and influence of the electrocoagulation process on the morphology of the surface of electrodes.Overall, the results showed that the new reactor was efficient enough to reduce the concentration of phosphate to the permissible limits. Additionally, SEM images showed that the Al anode became rough and nonuniform due to the production of aluminium hydroxides. The main advantages of the electrocoagulation technique are:•The EC method does not produce secondary pollutants as it does not required chemical additives, while other traditional treatment methods required either chemical or biological additives [1–4].•It has a large treatment capacity and a relatively short treatment time in comparison with other treatment methods, such as the biological methods [1,5–7].•The EC method produces less sludge than traditional treatment traditional chemical and biological treatment methods [8,9].EC technology, like any other treatment method, has some drawbacks that could limit its performance. For instance, it still has a clear deficiency in the variety of reactor design, and the electrodes should be periodically replaced as they dissolve into the solution due to the oxidation process [2,10].

Fluid flow characteristics of a multi-scale fluidic network

This paper presents an original study on the fluid flow characteristics of a multi-scale fluidic network consisting of a number of elementary ladders. Computational Fluid Dynamics (CFD) simulations were performed to characterize local fluid flow patterns and flow distribution properties in such a complex geometry. In parallel, flow visualizations using fast camera and tracers were carried out in a transparent prototype. A special effort was made to improve the flow distribution uniformity among the 90 parallel mini-channels by inserting the geometrically optimized perforated baffles. The global pressure losses of the multi-scale network with or without baffles were also measured experimentally so as to be compared with the numerical results.For the multi-scale fluid network, non-uniform flow distribution was observed even under very low flow-rate conditions (e.g., mean Rech=10). For higher flow-rate conditions, significant flow non-uniformity seems inevitable. The insertion of optimized perforated baffles could provide a remarkable improvement on flow distribution uniformity, even under high flow-rate conditions (mean Rech up to 2000). Good agreements between numerical and experimental results are observed.

Experimental investigation on the thermal performance of a double pipe heat exchanger with segmental perforated baffles

This work experimentally investigates the characteristics of convective heat transfer and pressure drop of water flow in the annulus-side of horizontal double pipe heat exchangers. Twelve heat exchangers of counter-flow configurations are constructed with/without Single Segmental Perforated Baffles (SSPBs), which are fabricated with different holes spacing, void, cut, pitch ratios and inclination angle. The experiments are performed for annulus-side Reynolds number from 1380 to 5700, and for Prandtl number from 5.82 to 7.86. The results revealed that increasing SSPBs holes spacing and void ratios and inclination angle and decreasing SSPBs cut and pitch ratios increase the annulus average Nusselt number (Nu¯an) as well as friction factor (fan). The thermal performance index (TPI) is calculated to compare the thermal performance of perforated baffled double pipe heat exchangers with un-baffled one. It is observed that increasing SSPBs holes spacing ratio and inclination angle, and decreasing SSPBs void ratio, cut ratio and pitch ratio enhances the thermal performance index. Finally, correlations for Nu¯an in addition to fan for concentric tube heat exchangers with SSPBs as a function of the investigated parameters are obtained.

Evaluation of Double Perforated Baffles Installed in Rectangular Secondary Clarifiers

Double perforated baffles in rectangular secondary clarifiers were studied to determine whether they contribute to producing high-quality effluents. The Computational Fluid Dynamics (CFD) simulations indicated that bio-flocculation occurred at the front of the baffle and the longitudinal movement of the settled sludge was hampered whenever the clarifier had high inflow. Simulation results showed that the rectangular clarifier with the double perforated baffle produced an effluent with lower suspended solid (SS) concentrations than the effluent from the clarifier without the baffle. To verify the simulation results, a double perforated baffle was installed in two of the 48 rectangular clarifiers in a 300,000 m3/d-capacity wastewater treatment plant. To study the effect of the baffle on solid removal, the effluent turbidity of the clarifier with and without the double perforated baffle was measured simultaneously. Experimental data showed that the double perforated baffle played a significant role in reducing effluent turbidity. The effluent turbidity reduction ratio with the baffle decreased when the Sludge Volume Index (SVI) of the Mixed Liquor Suspended Solids (MLSS) was below 100 mL/g. The overall average reduction ratio was 24.3% for SVI < 100 mL/g and 45.1% for SVI > 100 mL/g. The results of this study suggest that double perforated baffles must be installed in secondary rectangular clarifiers to produce high-quality effluent regardless of the operational conditions.

Numerical study on performances of shell-side in trefoil-hole and quatrefoil-hole baffle heat exchangers

Shell-side performances of trefoil perforated plate baffle heat exchanger with equilateral triangle tube layout and quatrefoil-hole baffle heat exchangers with square tube arrangement have been studied numerically. Through establishment of periodic model of heat exchangers with three different trefoil and quatrefoil opening heights of 1.8mm, 2.3mm and 2.8mm, the influence of opening height on the shell-side performances has been studied. The experiment of a heat exchanger with trefoil-hole baffles has been conducted to verify the validation and accuracy of periodic model. The results indicate that the enlargement of opening height decreases pressure drop and heat transfer coefficient while the reduction of it causes dramatic pressure loss with a modest increase of heat transfer coefficient. The heat transfer coefficient per unit pressure drop of trefoil-hole baffle heat exchangers is higher than that of heat exchangers with quadrifoil-hole baffles.

Experimental study on vertical baffles of different configurations in suppressing sloshing pressure

The effectiveness of four types of the baffles in suppressing pressure is experimentally investigated under a wide range of forcing frequencies. The dynamic impact pressure variations alongside the central line of the tank wall and the baffle response to different excitation frequencies were measured for tanks without baffles and with immersed bottom-mounted vertical baffles, vertical baffles flushing with free surface, surface-piercing bottom-mounted vertical baffles and perforated vertical baffles, respectively. The maximum impact pressure on the tank wall generally increases with decreasing the distance of the pressure sensor away from the free surface. In the frequency range from 0.4ω1 to 1.4ω1, the vertical baffle flushing with free surface is an more effective tool on reducing impact pressure comparing with the immersed bottom-mounted vertical baffle, especially near the first-mode natural frequency, and effects of the perforated vertical baffle in suppressing sloshing pressure is more significant than that of the surface-piercing bottom-mounted vertical baffle, especially in high forcing frequency region. It is found that the first-mode natural frequency of liquid-tank is altered by the vertical baffles. The experimental results show that changing flow fields and altering natural frequency may effectively suppress the impact pressure on the tank walls.

Thermal Behavior in Dimple Square Duct with Inclined Perforated Baffles

This research presents a study of heat transfer enhancement and pressure drop in a dimple square duct fitted with∝ =30◦,60◦and 90◦ inclined perforated baffles(baffles open area ratio of 26.17 %). The baffle to duct height ratio (w/a) of 0.3 and the baffle pitch to duct height ratio, PR=1, 2 are introduced in the present work. The tested duct has a constant wall heat flux condition. The experiments are carried out by varying airflow rate in terms of Reynolds number ranging from 1147.8 to 15304. The experimental data of heat transfer and pressure drop of the duct fitted withthe inclined perforated baffles are compared with those of the dimple smooth duct under similar condition. The inclined baffles with PR=1 gives higher heat transfer rate than the one with PR=2 and the smooth ductrespectively ,andthe highest heat transfer and pressure drop is found by using baffle with 30◦.

Increasing the Use Efficiency of the Absorption Capacity of Adsorbent in Vertical Absorbers

A newly developed design of an absorber is described. In the new absorber, a horizontal annular perforated baffle with a directing conical bucket is situated on top of the upper layer of absorbent, which is covered by a layer of ceramic balls through a separating screen. Such a design assures a high degree of uniformity of the distribution of the input gas stream at the inlet to the absorption layer and produces an increase in the use efficiency of the absorption capacity of the adsorbent in vertical absorbers.

Experimental study of heat transfer enhancement in a rectangular duct distributed by multi V-perforated baffle of different relative baffle width

The current research deals with the experimental investigation of the heat transfer behavior and optimum relative width parameter of the multi V-down pattern perforated baffle rectangular duct. The 60° angled multi V-down perforated pattern baffle are attached on the lower duct wall having an aspect ratio (W D /H D ) of 10.0 and a Reynolds number (Re) ranging from 4000 to 9000. The experiment was conducted by varying the relative baffle width (W D /W B ) ranging from 1.0 to 6.0, relative baffle height (H B /H D ) was 0.5, relative baffle pitch (P B /H B ) was 10.0, relative hole position (O B /H B ) was 0.44, open area ratio (β O ) was 12 %. The experimental investigation shows that at a relative baffle width of 5.0 the thermal performance was maximized. Thermo-hydraulic performance (η p ) comparison shows that multi V-down pattern perforated baffle has better outcomes as compared to other baffles shaped rectangular duct.

Thermal Hydraulic Performance in a Solar Air Heater Channel with Multi V-Type Perforated Baffles

This article presents heat transfer and fluid flow characteristics in a solar air heater (SAH) channel with multi V-type perforated baffles. The flow passage has an aspect ratio of 10. The relative baffle height, relative pitch, relative baffle hole position, flow attack angle, and baffle open area ratio are 0.6, 8.0, 0.42, 60°, and 12%, respectively. The Reynolds numbers considered in the study was in the range of 3000–10,000. The re-normalization group (RNG) k-ε turbulence model has been used for numerical analysis, and the optimum relative baffle width has been investigated considering relative baffle widths of 1.0–7.0.The numerical results are in good agreement with the experimental data for the range considered in the study. Multi V-type perforated baffles are shown to have better thermal performance as compared to other baffle shapes in a rectangular passage. The overall thermal hydraulic performance shows the maximum value at the relative baffle width of 5.0.

Design and optimization of baffled fluid distributor for realizing target flow distribution in a tubular solar receiver

This paper presents an original study on the design and optimization of baffled fluid distributor for the realization of optimal fluid flow distribution in a tubular solar receiver. The basic idea is to install a perforated baffle in the inlet fluid distributor and to optimize the configuration of orifices on the baffle so as to approach the target flow distribution among downstream parallel tubes. A pressurized-air solar receiver comprising of 45 parallel tubes is used for study, with copper or Inconel 600 used as the filling material.Results show that the final fluid flow distributions realized by the geometrically optimized baffles are in good agreement with the target curves. The peak temperature of the receiver wall can be minimized accordingly with moderate increase in total pressure drop of the receiver system. It is shown that the insertion of a geometrically optimized baffle is generally a practical solution with various features: capable of realizing non-uniform target distribution; small pressure drop increase; compact geometry; flexible and adaptive; easy fabrication with a reasonable cost, etc.