Baffle Plate Research Articles

A computational fluid dynamics‐based method to investigate and optimize novel liquid distributor

AbstractLiquid distributors have an important influence on packed towers' hydrodynamics and mass transfer performances. This work has designed a narrow‐trough liquid distributor with stepped baffle plates to regulate liquid flow. The liquid mainstream is diverted layer by stepped baffles to realize the uniform distribution of liquid. The relationship between liquid flow and the baffle plates arrangement is studied by computational fluid dynamics (CFD) simulation. Furthermore, we put forward a CFD‐based structural optimization scheme to arrange baffle plates in an arc shape, which leads to a uniform and stable flow of each distribution orifice in the range of liquid spray density of 5–120 m3·(m2·h)−1. The simulation results agree with experiments, which proved that the novel liquid distributor has excellent performance. Compared with the traditional trough liquid distributor, the novel liquid distributor can provide more liquid drip points, more gas‐phase channels, higher operating flexibility, and take up less space.

Effective configuration of perforated baffle plate for efficient slosh damping in liquid retaining tanks under lateral excitation

Perforated baffle plates are used as an anti-slosh mechanism in various fields owing to the need for slosh suppression and weight reduction. However, there is an uncertainty in the selection of configuration of perforated baffle plate due to the several influencing parameters for slosh damping efficiency. Therefore, the present study focuses on the development of an efficient slosh damping configuration for the perforated baffle plate. For this, nonlinear dynamic analysis under seismic ground motions with different PGA/PGV ratios has been carried out in the time domain using the concepts of Computational Fluid Dynamics (CFD) in the numerical models of liquid tanks with perforated baffle plates of different configurations. The response of the system under impulsive and convective modes is analysed by observing the free surface elevation, hydrodynamic pressure, turbulence kinetic energy and turbulence eddy dissipation as the response parameters. The study developed an effective baffle configuration for efficient slosh damping, considering the various response parameters.

A novel design for muffler chambers by incorporating baffle plate

In many technical applications in the present era, acoustics noise is the most difficult issue for humans. Although reactive and absorptive types of mufflers are currently available for noise reduction, their performance is limited for a variety of reasons. This study involves measuring transmission loss in an automotive exhaust muffler and then adopting new design parameters to reduce transmission loss, which is important for a greener environment. The automotive mufflers chosen for this study are investigated and employed in a numerical study to compare with an experimental investigation of passive noise control for transmission loss in automobiles. The transmission losses are compared to the original muffler chamber specifications to find the change in transmission losses, and the muffler chambers are modified by integrating a baffle plate to minimise the automotive exhaust noise. The transmission loss in a muffler is experimentally controlled by a passive noise, and a numerical analysis is performed for comparison using commercial software MATLAB. The installation of the baffle plate reduces the transmission loss, both in the narrow band and octave band region, according to the experimental, numerical and theoretical data, with more reduction happening in the narrow band region than the octave band region in this passive noise control experimental work.

Mitigation of jet cross-flow induced vibrations using an innovative biomimetic nozzle design inspired by shark gill geometry

Shark gill slits enable sharks to eject the water after the oxygen has been removed in ram ventilation. The reduced effect of jet flow from the gill slits gives sharks smooth maneuverability. A biomimetic “shark nozzle” is proposed to improve mixing between the jet flow and surrounding fluid. Jet flow systems are an essential component of many industrial applications. The key characteristic of jet flow is the mixing process that occurs between two fluid streams to allow heat and/or mass transfer between them. Many industrial and propulsion devices that use jet flows need rapid mixing for effective and environmentally friendly operation. Fuel-injection systems, chemical reactors, and heating and air conditioning systems are examples of devices where a mixing process takes place. Recently, jet flow plays an important role in design and operation of specialized nuclear pressurized water reactors (PWRs). The loss-of-coolant accident (LOCA) holes and slots machined in the core periphery baffle plates are designed to mitigate the effects of a severe LOCA event. However, in normal operation, the holes are a source of a jet flow that can induced vibrations in the fuel assemblies near the baffle before being mixed with the surrounding fluid. This may cause wear and fretting in fuel rods with their supports. The ultimate solution to prevent the fuel assembly vibrations from LOCA hole jetting in a reactor is enhancing mixing of a jet flow with ambient flow in order to rapidly reduce jet momentum. This work proposes a new shark-inspired nozzle design that exploits the observed high efficiency capacity of shark gill slits. Tests are conducted to evaluate the performance of the new design. The obtained results show that the shark-inspired biomimetic nozzle has a greater effect on the rod bundle vibration, and the critical velocity at which the unstable vibration occurs in the rod bundle is delayed by 20% using the biomimetic nozzle. In addition to delaying instability, a vibration amplitude reduction of 85% was obtained by using the proposed shark-inspired nozzle instead of the circular nozzle.

NPP Krško Post-UFC Transient Response during MSLB

UpFlow Conversion (UFC) was implemented in NPP Krško during the last outage in order to reduce the pressure differential across baffle plates and the possibility of the fuel damage caused by flow induced vibration. The paper describes the coupled code calculation (RELAP5 and PARCS) of MSLB accident at power for pre and post-UFC configuration of reactor vessel. In the calculation, the split model of the reactor vessel was used to better describe asymmetric conditions in loops. It has been demonstrated that the basic parameters (pressure, temperatures) stayed unchanged and there was little change in the flow rates except in baffle-barrel region of the vessel where both flow direction and amount of flow were changed.

Performance Assessment of an Air-Type BIPVT Collector with Perforated Baffles through Indoor and Outdoor Experiments

The performance of air-type PVT and BIPVT collectors has been extensively studied. As a system that generates heat and power, PVT collector testing has some particularities especially when using air as a heat recovery fluid and a building-integrated design (BIPVT). The electrical and thermal experimental performance of such collectors are currently being evaluated using in-house methods or PV and/or solar thermal collector standards. The use of a wide range of methods, testing conditions and experimental setups makes it difficult not only to compare the performance of different designs, but also to have confidence in the results obtained. This study evaluates the performance of an air-type BIPVT collector with in-channel perforated baffle plates for heat transfer enhancement designed for a building-integrated façade. As part of a joint research project between Korea and Canada, the proposed collector’s performance was evaluated through indoor (Canada) and outdoor experiments (Korea). Limited comparison of the results obtained with the two testing methods could be performed due to differences in environmental testing conditions, BIPVT collector area and experimental setup. Nevertheless, the limited measurement points under comparable testing conditions indicate that the results from the indoor and outdoor experiments have a similar trend. A comparison between the studied collector having a full PV absorber and a BIPVT collector with a hybrid PV/solar thermal collector absorber using a similar indoor experimental setup and testing conditions was performed. It showed that under still air conditions, for an irradiance level of approximately 820 W/m2 and with a low flow rate, the BIPVT collector with a hybrid PV/solar thermal absorber has a thermal and electrical efficiency of 25.1% and 5.9%, respectively. Under similar conditions, the BIPVT collector with a full PV absorber has a thermal efficiency of 23.9% and an electrical efficiency of 13.5%. At higher flowrates, both units have similar thermal efficiencies, however, the BIPVT collector with a PV absorber remains with an electrical efficiency that is more than double that of the unit with a hybrid PV/solar thermal absorber.

Effects of number of air holes on flame and heat transfer characteristics in a multihole baffled combustor combined with micro-thermophotovoltaic and micro-thermoelectric systems

• A multihole baffled micro combustor combined with micro-thermoelectric generators is proposed as a micro power generator. • The optimal number of air holes related to the combustion efficiency and the preheating effect is obtained. • The good features for micro-thermophotovoltaic(TPV) and micro-thermoelectric(TEG) systems is linked to wavy and lobed flames. • The emitter efficiency for TPV applications is comparable to the swirling flow combustor. • A high conversion efficiency of 3.58% is obtained for the multihole baffled micro combustor. Currently, micro power generators have been widely drawing attention for various applications. In this study, the H 2 –air micro combustor (MC) with a multihole baffle plate was combined with two power generators based on micro-thermophotovoltaic and micro-thermoelectric systems. The reacting flow and conjugate heat transfer including the MC wall were analyzed by the detailed reaction mechanism and the outer wall condition of convection and radiation. From the resulting thermal fields, the characteristics of heat emission and electrical potential were examined. Eight baffles with different numbers of air holes (N a ) and three global equivalence ratios were selected, and a baffle with N a = ∞ was adopted to compare the multihole and annular air flows. The combustion characteristics depending on N a were explored by analyzing the changes in the reaction zone, the flammable range, reaction rate, and wall heat transfer rate. The N a effect on wall and center recirculation zones was comparable to the variation due to other geometrical variables of the baffle plate. As N a increased, the combustion efficiency increased to 20% of the N a = ∞ case. The combustion efficiency equivalent to the swirl MC was obtained for N a = 5–8, having enhanced preheating effects and large center recirculation zones. Compared to N a = ∞, the mean temperature of the multihole baffled MC increased by 6.4%–19.2% depending on N a . The emitter efficiency related a TPV system was comparable to the swirling flow MC. For a thermoelectric generator, the conversion efficiency of N a = ∞ was similar to that of a Swiss-roll MC, and the multihole baffled MC showed a high conversion efficiency of 1.55%–3.58% depending on N a and the global equivalence ratio.

Modified on Shell and Tube Heat Exchanger

Abstract: Heat transfer is one of the most important processes in many industries. For this a heat exchanger is used. There are many different types of heat exchanger available that are double tube heat exchanger, Shell and Tube heat exchanger, tube in tube heat exchanger, Plate heat exchanger, Finned heat exchanger etc. In heat exchanger a fluid is used to cool another fluid which is a higher temperature, this is done either with direct contact between the fluids or indirect contact between the fluids with a surface in between. Most common type of heat exchanger used in industries is Shell and Tube heat exchanger due to its dimension flexibility which is it dose not have any dimension limit to it. As most of the Shell and Tube heat exchanger in the industries are of long lengths and also they are equipped with only single pass of the tube and with either parallel flow or counter flow. They are also equipped with different types of baffle plate at different angles and placing. In this project we have done construction and performance on Shell and Tube heat exchanger which is made in compact size and which is also equipped with parallel flow and counter flow. We have given multiple passing of the tube throughout the shell which results in better cooling of water. The cooling medium used in this project is water at normal room temperature. Because of the compact size of this heat exchanger it can be used in small spaces with availability of water like in small scale industries. Keywords: Shell and tube heat exchanger, heat transfer, multiple pass, compact size, rotameter, valves

Solar ponds-a mini review.

A solar pond is a simple system that collects and stores heat for thermal and electrical applications. Heat storage and heat extraction are the key factors in the solar pond. Salt is added to the pond with fresh water to form a salinity gradient solar pond (SGSP). The solar pond comprises of three zones, namely, the upper convective zone (UCZ), the non-convective zone (NCZ) and the lower convective zone (LCZ). The LCZ is also called the storage zone. Generally, the LCZ stores the heat energy of the incoming solar radiation, and this heat may be used for various applications. In this paper, a review is done on the study of solar ponds with various designs and modifications, heating methods, use of floating devices, use of baffle plates, use of heat exchangers, use of flat plate collectors, use of different types of insulation, etc.

Evaluation of a Paraffin/Nitrous Oxide Hybrid Rocket Motor with a Passive Mixing Device

Hybrid rockets offer numerous advantages over other types of rockets but tend to suffer from low combustion efficiency. Higher efficiency can be achieved by using passive devices in the combustion chamber that promote additional mixing of unreacted propellants. The current work examines a paraffin and nitrous oxide hybrid motor that uses a mixing device located downstream of the fuel grain to enhance combustion efficiency. The mixing device used in this work is a six-port baffle plate. Combustion efficiency, as measured by characteristic velocity, was found to increase by over 40% with the use of the passive mixing device. It was identified that certain high-mass-flux motor configurations resulted in unstable motor operation when the mixing device was present. Experimental results indicate that stable combustion occurs for oxidizer mass flux levels below . Exceeding this limit results in combustion oscillations in excess of 20% of the mean chamber pressure.

Effects of inlet-outlet positioning, muffler geometry, and baffle design on vehicle muffler performance for desired sound transmission loss

A systematic comparative examination of different single-chamber and double-chamber muffler geometries, comprised of various baffle geometry and size, number of chambers, and inlet-outlet positioning was conducted to determine the most suitable geometry for size-efficient mufflers which can meet size-limitations of automotive applications, confirming enhanced transmission loss (TL). First, we considered a reference model for validation of the simulation method. Then, we objectively studied the effects of circular and rectangular baffles of different sizes on the TL of single-chamber mufflers. Next, double- and single-chamber models were compared. Consequently, to better analyze the performance of the representative benchmark double-chamber muffler, the effects of different layouts of the outlet were studied and the corresponding TL was derived, while the inlet and baffle type and size were fixed. Finally, the effect of inlet layout, considering given outlet position, baffle type, and size, was studied on the noise control performance of the muffler. Results indicate that the 75% circular baffle has a wide frequency range and high TL of 58 dB, where the 75% rectangular plate baffle has a transmission loss of 67 dB. The double-chamber muffler has a wider frequency range and a higher TL of 78 dB compared to the single-chamber muffler. Moreover, changes in the inlet-outlet of the silencer significantly affect TL. As the inlet-outlet positioning of the silencer greatly contributes to the space constraints and packaging of the vehicle components, therefore, the variations of the inlet-outlet position of the silencer in the limited space available in vehicles need to be considered as an important design parameter, considering packaging limitations and noise control performance, which can significantly affect tailpipe radiated noise.

Some Practical Acoustic Design and Typical Control Strategies for Multichannel Active Noise Control

Active noise control (ANC) systems usually involve a large number of loudspeakers and error microphones in order to achieve noise reduction over an extended region of space. Although fundamentals of ANC theory and principles of ANC methods have been well-established over the past 40 years, applications of this technology are facing new challenges. A larger quiet zone with better noise reduction performance is always desirable in a variety of real-life scenarios. This paper presents several important factors that affect the performance of multichannel ANC systems in some popular applications such as windows with natural ventilation and quiet-zone around heads. The factors affecting acoustic design include the reflection of a baffle plate, arrangement of error sensors in open areas, and so on. In addition, different control strategies are compared and analyzed, including centralized, decentralized, and distributed strategies. All these strategies are discussed from the signal processing side, which should be considered after a proper acoustic design. One of the important aims of this paper is to provide practical guidance for acoustic design and discuss several typical control strategies for multichannel ANC systems.

CFD analysis and comparison of conventional type and perforated plate type shell tube heat exchangers

Abstract The baffle plate is the most important elements affecting not only the thermal efficiency but also the hydraulic performance of shell-tube heat exchangers that can be designed in different types today and can be put into the production phase. Different designs of baffle plates are closely related to thermal performance with pressure drop as well. In this investigation, the design geometry of the shell-tube type was carried out by means of the ANSYS Fluent program. In the analyses, it is purposed to examine the consequences on the heat transfer rate per drop of pressure and not only the pressure’s drop but also the coefficient parameter of heat transfer of the exchangers in which traditional one-piece type baffle plate and perforated type baffle plate are used where the shell side. Here, water is used as the working fluid; it was examined as 1.2, 1.5, 1.8 and 2.1 kg/h at four varied mass flow rates (m). As a result, the values compared to the traditional one-piece baffle plate and the perforated type baffle plate. It has been monitored that the heat transfer rates per drop of pressure vary.

Structural Optimization of Self-Supporting Rectangular Converging-Diverging Tube Heat Exchanger

A three-dimensional numerical investigation of turbulent heat transfer and fluid flow characteristics of the new heat exchanger and self-support of a rectangular converging-diverging (SS-RCD) tube bundle heat exchanger with different inserts was performed. The values of the Reynolds number varied from 27,900 to 41,900. The baseline case (without an insert) was compared with two enhanced configurations: one circular hole in the baffle plate (one-circle case) and a rectangular hole in the baffle plate (one-rectangle case). Compared with the baseline case, the airside Nusselt number (Nu) of the enhanced cases improved by 39.6~48.0% and 36.2~40.2% and had an associated friction factor (f) penalty increase of 53.9–66.7% and 60.7–77.8%, respectively. The baseline case was compared with three enhanced configurations: one-circle case, two-circle case, and three-circle case baffle plate. Compared with the baseline case, Nu of the enhanced cases improved by 39.6–48.0%, 36.2–45.4%, and 35.0–44.2%, with f penalty increases of 53.9–66.7%, 44.9–60.0%, and 43.8–60.0%, respectively. The overall performance was conducted by heat transfer enhancement factor (η). It was found that the one circle case obtained the best overall performance. The numerical results were analyzed from the viewpoint of the field synergy principle. It was found that the reduction in the average intersection angle between the velocity vector and the temperature gradient (θ) was one of the essential factors influencing heat transfer performance.

The concave-wall jet characteristics in vertical cylinder separator with inlet baffle component

The concave-wall jet was formed in the vertical cylinder separator with inlet baffle component. The effect of curvature of radial baffle on the jet flow in the separator was investigated by the experiment of concentration and the numerical simulation of species transport. The results show that the concave-wall jet was confined within the narrow region near the concave-wall and the flow disturbance in the center of separator was weakened. The distribution of concentration and the flow region of wall jet depended on the curvature of radial baffle ( K ). Compared with the turbulent intensity of the plate baffle ( K = 0), that of concave baffle ( K = 2) reduced by 6.1% and the turbulent intensity of convex baffle ( K = −2) increased by 13.5%. The best flow stability was obtained by the concave baffle because the baffle outlet was similar to convergent nozzle. The outlet convergent angle was between 0° and 19.5° when 0 ≤ K ≤ 2. The secondary vortices were caused by the tangential velocity irregularity on the cross-section of two axial baffles in the separator with convex baffle. The baffle with K ≥ 0 was more suitable in separator inlet than that with K < 0.

Flow Characteristics and Structure Optimization of a Baffle Plate Heat Exchanger

In this study, a theoretical model of the hot and cold fluid flow, heat transfer, and thermal stress coupling in a baffle plate heat exchanger is established, and numerical simulation is carried out. The flow field in the heat exchanger and the deformation of the heat exchange tube bundles in the baffle plate heat exchanger are studied. The optimization effect of the diversion grid on the flow field at the inlet of the variable section is emphasized. The influence of grid arrangement on the flow field and the performance of the tube bundles are analyzed and discussed. The results show that the backflow situation can be effectively improved and the vortex intensity in the straight section of the cold fluid inlet can be greatly reduced by adding the grid. The deformation of the heat exchange tube bundles illustrates the maximum deformation with 1.39 mm at the position of the strongest backflow. The deformation can be reduced by 26% due to the arrangement of the diversion grid, which is helpful to improve the safety of the device.

Towards idealized thermal stratification in a novel phase change emulsion storage tank

Energy storage density and charging/discharging speed are crucial performance indices for an energy storage unit. Phase change materials (PCMs) have been perceived to improve the energy storage density in thermal energy storage, but the relatively low charging/discharging speeds have been a bottleneck to their application. In building cooling storage applications using ice, the energy efficiency is compromised as the working temperature of ice storage is far below that required for air dehumidification and building cooling, which ranges between 7 and 17 °C. In this study, both experimental and numerical studies were carried out to demonstrate a novel stratified storage tank of PCM-in-water nano-emulsion for cold storage in building radiant cooling applications. A 20 wt% PCM-in-water nano-emulsion was utilized as both the storage medium and heat transfer fluid. The experimental results showed that the cooling capacity of a cooling panel was increased by 60% with phase change emulsion circulating in the loop. The effective energy storage capacity of the stratified storage tank was 1.6–1.7 times that of water in a wide range of discharging flow rates/speeds. Validated with the experimental data, the numerical simulation showed that installing baffle plates in the storage tank could effectively reduce the fluid mixing and significantly increase the effective energy storage capacity, especially at high discharging flow rates/speeds. In comparison with other PCM thermal energy storage designs, the stratified storage tank of PCM-in-water nano-emulsion has the advantage of a lower temperature difference between the cooling source and the demand, and thus raising the overall system energy efficiency.

LABORATORY STUDY OF ELECTROCOAGULATION FOR COD REMOVAL FROM WASTEWATER

The current work investigates the ability of the new aluminium-based electrocoagulation (EC) cell to remediate chemical oxygen demand (COD) from synthetic wastewater. The experimental work was carried out using a rectangular EC cell (10 cm in length, 9.5 cm in width, and 7 cm in depth). The EC cell was supplied with six perforated aluminium electrodes; four of these electrodes were used in the treatment methods (connected to DC electrical current), while the first and the last electrodes were used as baffle plates (to mix water). This lab-scale unit was used to treat synthetic wastewater having 300 mg/l of COD, considering the effect of the treatment time and initial pH. After 40 minutes of treatment at a pH of 7 and a current density of 10 A/m2, 51% of COD was removed by the new EC unit. The results also revealed that the removal of the COD is positively influenced by the increase of the applied current density and/or treatment time.

Investigating the single pass baffled solar air heater (SAH) with an organic PCM (OPCM)

The current work shows the results of an experimental assessment into the performance of a baffled solar based air heater (SAH-BP) with the organic phase changing material (OPCM) back-up. The experiments were conducted in two modes of operation during two identical solar days in the month of February 2021 at 11.0168° North, 76.9558° East. They were SAH having baffled absorber without any PCM (SAH-BP), and baffled SAH with OPCM (SAH-BP-OPCM). The baffle plates were attached over the absorber surface in alternative sequential way and OPCM was stored beneath the absorber. The normal commercial grade paraffin was employed as OPCM and the experimentations were carried-out at the constant flow rate of 0.18 kg/s. The results substantiated that the amalgamation of OPCM within the baffled SAH enhanced its performance in terms of energy efficiency. The OPCM improved the energy efficiency of the SAH-BP by 11.25%.

Design Optimization of a Helical Coil Gas Cooler Based on the Results of CFD Modeling of Erosion Wear

Simulation of erosion wear and design optimization have been performed for a convective gas cooler with a helical coil. Based on the results of simulation of the standard gas cooler design with a flat baffle used in Shell gasification-based combined cycle unit, it is concluded that the particle impact angle is the main factor determining the erosion maximum. To reduce erosion, it is necessary to install a structural element instead of the flat baffle to align the flow path of ash particles at the inlet to the gas cooler. The results of simulation for various baffle shapes show that a hemispherical baffle is optimal. The use of a hemispherical baffle plate made it possible to align the ash particle flow path at the inlet to the gas cooler channels and reduce the maximum level of erosion by a factor of almost 4 compared to the standard geometry of the baffle plate.