CFD Study Research Articles

Improving the performance of a PCM integrated solar air collector by adding porous fins over the bottom side of the absorber: A transient CFD study

In this study, it is aimed to improve the utilization time period of a solar air collector by integrating a PCM unit. In this context, a PCM unit was integrated to a single-pass solar air collector. Additionally, porous fins were added into the PCM unit in order to shorten PCM melting time. Thus, six different solar collectors were designed and numerically analyzed by adding a storage unit and fins to the collector. A collector without storage and five PCM added collectors with different number of porous fins were studied. In other words, the effect of integrating PCM container and adding porous fins inside the PCM container on various parameters such as utilization time period of the collector, outlet temperature, thermal efficiency and exergy efficiency were investigated. The ANSYS Fluent program was used in numerical analyses. As a result, integrating the PCM unit to the analyzed air collector caused to extend utilization time period of the collector. Adding porous fins into the PCM unit has resulted in a significant increase in the overall performance of the system. In addition, increasing the number of porous fins accelerated the melting process of paraffin. Increasing the number of porous fins was significantly improved average energy efficiency. Average thermal efficiency of the tested collectors was obtained between 38.66 and 41.73 %. In general, as a result of numerical analysis of six different systems, the utilization time was increased by adding the PCM unit to the solar air collector. Moreover, placing porous fins inside the PCM unit increased the performance of the system by accelerating the melting of the paraffin.

Effect of particle size distribution variability on the permeability of hydrate-bearing sediments: A CFD study

Natural gas hydrates (NGH) are considered as a future clean energy in the era of carbon neutrality. The seepage behaviour of hydrate-bearing sediment (HBS) and its controlling factors are significant for developing effective production strategies. In this study, we aim to elucidate how the heterogeneous spatial distribution of clayey-silty sediment particles, particularly the non-uniform particle size distribution (PSD) affects the permeability of HBS. An algorithm was developed to generate the heterogeneous spatial distribution of sediment particles based on the PSD of hydrate-bearing cores extracted from Japan Nankai Trough (D50 = 122 μm). A series simulation of fluid flow in porous media based on CFD was conducted for the HBS with varying hydrate saturations (SH). The watershed segmentation algorithm was employed for the identification of pore structure, including pore space and pore throat with a detailed analysis on the pore structure evolution with SH. Host sediments with higher uniformity result in initial high permeability but the permeability reduction with increasing SH is more significant compared with that of lower uniformity. Pore throat width reduced to less than 5 μm with SH above 50% compared with its original width of ∼30 μm. Tortuosity exhibits a linear increase with SH, while permeability decreases exponentially with increasing tortuosity. We propose an improved permeability model (KCpro) based on the classical Kozeny-Carman model accounting for the change in specific surface area for non-uniform PSD in HBS with good agreement. This study confirmed the applicability of CFD modelling as a promising tool to study the seepage behaviour of HBS complementary to classical permeability experimental tests. Results of this study provide fundamental understanding on how permeability evolves in HBS with significant PSD variations in natural gas hydrate reservoirs in nature.

A 3-dimenional CFD study of boiling in jet impingement

A 3-dimenional CFD study of boiling in jet impingement

A CFD Study of Particulate Deposition on Dimple-Type Flue Walls of Coal-Fired Power Plants

The study of particle deposition in bends is always a continuous challenge in various engineering and industrial applications. New types of channels with special microstructures on the surfaces can be effective in modifying the flow field structure as well as particle deposition in channels. In this study, a 90° circular bend with a convex dimple structure was used, and the flow field and the deposition of particles in the channel were analyzed; the Stokes numbers (St) used were 0.016, 0.355 and 1.397. The reliability of the model was ensured by mesh-independence validation as well as speed validation. In a 90° bend channel with convex dimples, the temperature distribution, particle deposition distribution, flow structure and secondary flow were examined. The effects of the number of convex dimples and St in the bend on the flow field structure and particle deposition characteristics were analyzed. The results show that the main factors affecting the deposition characteristics of particles in bends are St, gravitational deposition, thermophoretic force, turbulent vortex clusters and secondary flow distribution. The effect of St is more pronounced, with the deposition rate increasing as the St increases, and the deposition location of the particles is mainly clustered on the outside of the bend structure of the elbow.

Flow Characteristic Analysis of the Impeller Inlet Diameter in a Double-Suction Pump

Pumps are considered crucial mechanical devices in any industry. Especially, double-suction pumps, due to their high-flow design and high head, are utilized in diverse industrial sectors. However, despite these advantages, double-suction pumps are vulnerable to issues like losses, vibrations, and cavitation. Pump vibration is mainly caused by suction recirculation occurring at the impeller inlet. Therefore, this study investigates the impact of the impeller inlet design on enhancing the stability of double-suction pumps while expanding the operating flow range. Through a validated CFD study, the influence of the impeller inlet passage size on the head and efficiency was analyzed. Furthermore, research was conducted on the phenomenon of suction recirculation occurring at the impeller inlet, proposing design guidelines to minimize it, especially for operation at low flow rates. The results demonstrate that the ratio of the hub diameter to the shroud diameter at the impeller inlet significantly impacts the avoidance of recirculation at low flow rates. These findings are expected to contribute to improving the stability and efficiency of high-flow pumps.

Effect of pulsating flow induced by a percussive drilling tool on cuttings transport in horizontal directional drilling—A CFD study

Cuttings deposition and removal has always been a key issue in horizontal directional drilling due to its correlation with numerous problems such as rate of penetration, reduction and stuck pipe.In this paper, the relationship between the impulse flow generated by a fluidic jet hammer and cuttings removal was discussed. A Eulerian-Eulerian two-fluid model was used to simulate the cuttings transport in horizontal wells on a sliding grid basis. Results show that the flow pulsation induced by a fluidic hammer contributes to easier cuttings transport. Compared to constant flow, impulse flow showed a 22.03% improvement in more optimal borehole cleaning with the same system inlet flow rate. In addition, the asymmetric flow pulsation was more sensitive to amplitude than the sinusoidal waveform pulsation flow, and as amplitude increased, the average exit flow rate of cuttings increased by 30.95%. Cuttings transport in annular is sensitive to rate of penetration, average velocity of pulsation, pulsation amplitude and cuttings size. The effect of pulsation frequency seems to be not much significant, probably because the frequency or other parameters used in this work did in the range of optimal particle-carrying frequency. These findings can provide references for the utilization of downhole pulsating fluids by drilling tools.

CFD Study on Improvement of Non-uniform Stirring in a Large Bottom-Blown Copper Smelting Furnace

CFD Study on Improvement of Non-uniform Stirring in a Large Bottom-Blown Copper Smelting Furnace

A CFD study on the hydrodynamic response of a small-scale ice floe induced by a passing ship

A CFD study on the hydrodynamic response of a small-scale ice floe induced by a passing ship

Flow Analyses of Integrated Liquid Fuel RAMJET Propulsion System

A CFD study is performed to check the seamless flow behaviour of the Liquid Fuel Ramjet Propulsion system which includes, air intakes, combustor and nozzle. Resolving both supersonic and subsonic flow scales in the same domain makes the simulations complex. Addition of combustion with stiff chemistry makes the simulations more difficult. CFD simulations are carried out using commercially available CFD software. Liquid fuel is injected as discrete phase and the flow turbulence is modelled using Realizable k-ε turbulence model. Jet-A + air combustion has been simulated using combined finite rate / eddy dissipation model. Finite rate chemistry was modelled using three step chemistry which was obtained from the published literature. Flow structures such as oblique shocks, normal shocks and combustion are observed.

Development of Correlations Based on CFD Study for Microchannel Condensation Flow of Environmentally Friendly Hydrocarbon Refrigerants

A CFD simulation of the condensation flow of R600a and R290 within microchannels was conducted to explore the effect of mass flux, hydraulic diameter, and vapour quality on heat transfer rate and pressure drop. Data obtained from CFD simulations were used to develop new heat transfer and pressure drop correlations for the condensation flows of R600a and R290, which are climate-friendly refrigerants. Steady-state numerical simulations of condensation flow of refrigerants were carried out inside a single circular microchannel with diameters varying between 0.2 and 0.6 mm. The volume of fluid approach was used in the proposed model, calculating the interface phase change using the Lee model. The CFD simulation model was validated via a comparison of the simulation results with the experimental data available in the literature. It is found that the newly developed Nu number correlation shows a deviation, with an Ave-MAE of 11.16%, compared to those obtained by CFD simulation. Similarly, the deviation between friction factors obtained by the newly proposed correlation and those obtained by CFD simulation is 20.81% Ave-MAE. Widely recognized correlations that are applicable to the condensation of refrigerants within small-scale channels were also evaluated by comparing newly developed correlations. It is concluded that the newly proposed correlation has a higher accuracy in predicting the heat transfer coefficient and pressure drop. This situation can contribute to the creation of a sustainable system via the use of microchannels and climate-friendly refrigerants, like R600a and R290.

Performance evaluation of novel plate-type condenser for an absorption/adsorption refrigeration system: Experimental and CFD study

Plate heat exchangers are widely used in many industries, such as refrigeration and air conditioning. Traditionally, the condenser in an absorption system comprises a shell and tube heat exchanger. However, we have innovatively replaced the conventional tubes with chevron plates in this system. The following variables were measured: condensation pressure (5.75–7.00 kPa), wall subcooling (0.2–1.8 °C), and channel Reynolds number (350–1400). In alignment with experimental results, the CFD simulation shows a higher condensation rate and large droplet size at the higher subcooling, and lower heat flux as the saturation pressure is decreased. Moreover, the overall heat transfer coefficient and the pressure drop of the chevron-type plate heat exchanger are increased by 1.60–5.00 times and 1.30–3.00 times, respectively, compared to the shell and tube condenser.

Detachment of a Soluble Particle at the Slag-Argon Interface: CFD Study and Experimental Observations

The behavior of non-metallic inclusions at interfaces of high-temperature melt and molten slag affects the removal of inclusions and the consequent melt cleanness. This study presents real-time in situ observations on the behavior of an oxide particle in the vicinity of the slag-argon interface by means of high-temperature confocal scanning laser microscopy (HT-CSLM). On top of that, CFD simulations are conducted to investigate the underlying mechanisms of particle-interface interactions. In addition to revealing the particle motion process from the argon phase toward the slag, a significant particle morphology alteration associated with its dissolution in the slag is experimentally observed. Particularly, upon detachment from the slag-argon interface, the particle exhibits more dissolution at the near-interface area. By combining with numerical simulations, this study indicates that particle separation at the interface can be characterized as two stages. First, a short-term capillary force-driven motion stage happens until the particle initially settles at the interface. The settling position estimated by simulation shows good consistency with experimental measurement. Second, the particle takes a relatively long time to eventually detach from the interface, and this period is accompanied by particle dissolution. Investigations suggest that the concentration variation near the interface arising from particle dissolution triggers a Marangoni flow. This flow, in turn, enhances the local dissolution rate, consequently causing a significant particle morphology change that influences the detachment. This study provides new insight into the mechanism of inclusion removal through slag absorption in metallurgical processes. Both particle dynamics and dissolution kinetics, especially the effect of solutal Marangoni convection, are highlighted in detaching a small-scale particle from the fluid-fluid interface.

Improving Natural Ventilation Multi-Story Buildings within Hot and Dry Climates: A CFD Study of Windcatcher Performance

Improving Natural Ventilation Multi-Story Buildings within Hot and Dry Climates: A CFD Study of Windcatcher Performance

Performance Analysis of Different Firearm Suppressor Structures

A powerful soundwave from shooting a firearm can travel great distances harming the shooter as well as anyone or anything standing nearby. To address this a firearm suppressor is used. A suppressor muffles the soundwave to a level that is usually safe for the shooter and its environment. A suppressor usually has 3-4 main parts that highly influence its effectiveness. The study aims to investigate how baffle design and placement selection influences the suppressor's effectiveness. The study consists of 162 different baffle design configurations. Suppressors with 3 to 9 baffles, angled from 30 to 60 degrees are simulated in a CFD environment. Slightly rounded baffles as well as different chamber volumes are tested as well. Suppressors with the best designs were then produced and tested on a firing range. At the firing range, a result of 32,24 dB delta was achieved and was only 4,67 % different than the result presented in the CFD study which was 30,8 dB respectively. The 9 straight geometry baffle angled at 30 degrees suppressor with an average chamber volume proved to be the most efficient and combined with a large initial chamber was the most efficient design in this study.

CFD Study and RSM Optimization of Acetylene Production in Partial Oxidation Process

CFD Study and RSM Optimization of Acetylene Production in Partial Oxidation Process

A CFD study on the start-up hydrodynamics of fluid catalytic cracking regenerator integrated with chemical looping combustion

ABSTRACT The integration of chemical looping combustion with fluid catalytic cracking (CLC-FCC) is an innovative concept that serves as a cost-effective method for CO2 capture in refineries. This approach has the potential to reduce refinery CO2 emissions by 25–35%, offering a promising solution. As in the conventional FCC unit, it is common for CLC-FCC regenerators to be exposed to an on-off process while they are being maintained and cleaned. The novelty of this research lies in its specific focus on a less-explored phase (start-up) of CLC-FCC regenerators, the application of advanced CFD modeling, and the comprehensive analysis of operational parameters that influence the system’s performance. To validate the CFD simulations of the different drag models for solid-gas granular, bed density profiles under steady-state conditions, collected from industrial processes, were used. For the flow period based on the start-up process of the drag models, the fluidization gas inlet geometry of the regenerator, flow regime (laminar and turbulent), and superficial gas velocity were comprehensively investigated to reveal their effects on hydrodynamic characteristics. The results show that Gidaspow and Syamlal-O’Brien drag models of the solid-gas multiphase granular flow exhibited a better fit with industrial data. The Syamlal-O’Brien and Gidaspow models closely align with industrial data under steady-state conditions, displaying similar bed densities in the dense phase region (230–310 kg/m3 for Syamlal-O’Brien and 235–300 kg/m3 for Gidaspow). During the initial stage (less than 0.2 seconds), both laminar and turbulent models yield comparable bed density profiles, approximately 510 kg/m3 in the dense phase. However, as the process progresses, the dense phase density decreases to about 250–350 kg/m3 at around 0.5 seconds, with laminar flow models showing a slightly better fit with industrial data. Notably, at 0.5 seconds of fluidization time, inlet geometries having better gas distribution achieve a highly diluted phase with bed densities of 10–20 kg/m3. Reaching a steady state, the bed density decreases from around 400 kg/m3 to 260–300 kg/m3, expanding into a higher section of the regenerator where it aligns well with industrial data. The increase in superficial gas velocity would result in the clarification of the difference and well mixing of the solid-gas multiphase flow.

CFD study of rib-enhanced printed circuit heat exchangers for precoolers in solar power plants' supercritical CO2 cycle

The modification of printed circuit heat exchangers through extended surface areas is a relatively underexplored topic, especially when considering their application in conjunction with precoolers in supercritical CO2 cycles. This study evaluates the response of a precooler by incorporating various configurations of integral and interrupted ribs, with the primary objective of identifying an optimized ribs combination under different operating conditions. The results demonstrate that ribs enhance secondary swirl flows, contributing to an increase in heat transfer levels in the supercritical CO2 flow. However, ribs do increase flow resistance, necessitating the careful selection of the optimal rib combination. The use of non-uniform patterns of interrupted ribs has been identified as the most feasible approach. By reducing the rib length and the distance between ribs at the upstream of supercritical CO2 and water flows, the performance of the precooler is notably enhanced. No matter the operating condition, cases with shorter rib lengths or smaller rib-to-rib distances at the beginning of both fluid paths consistently yield the best performance. Implementing these configurations in the precooler, the comprehensive performance index can reach approximately 1.2. This study contributes to enhancing efficiency and improving the compactness of large-scale solar power plants utilizing the supercritical CO2 cycle.

CFD study of nail penetration induced thermal runaway propagation in Lithium-Ion battery cell pack

Li-ion batteries have gained massive momentum due to their potential to hold the greatest energy density, but they suffer serious safety problems related to thermal runaway and flammability of the electrolyte components. A three-dimensional numerical modeling of Li-ion pouch cell-based battery pack is proposed in this study. The proposed three-dimensional integrated multiphysics model was validated with the experimental data, and used to investigate the impact of nail penetration depths (20 mm, 15 mm and 12.5 mm) and defect location effects on battery pack thermal runaway. The locations of the envisaged defects are at the upper, middle, lower sides of battery’s lateral edge, and middle of the bottom edge. The study showed that battery pack temperature evolution due to thermal runaway is substantially affected by both internal short circuit (ISC) size and defect locations. The thermal runaway with ISCs induced at upper, middle and lower sides of battery’s lateral edge have been found faster than that of ISC induced in the middle of the bottom edge. The thermal runaway inception for ISCs induced in the middle of the bottom edge lags behind 10 s when compared to thermal runaway inceptions for ISC induced at the upper, middle and lower sides of battery’s lateral edge. The study also investigated the effect of convective heat transfer coefficient on suppressing the thermal runaway propagation, and a convective heat transfer coefficient of 500W/m2.K effectively suppressed thermal runaway and minimize its respective effects. The study provides insights on vulnerable sides of battery in the pack and the corresponding failure behaviors, such insights are valuable for Li-ion cell design and thermal management system design.

CFD study on the effect of particle properties on the performance of annular jet pump

Abstract The annular jet pump is a type of fluid mechanical pump that operates by exchanging momentum with the fluid. Annular jet pumps possess distinctive advantages in the transportation of solid particles. However, the efficiency of these pumps is significantly impacted by both the physical properties of the particles and their initial concentration, thereby limiting their practical applications. In this paper, by combining other scholars’ designs of annular jet pumps, the effects of different physical densities and different initial concentrations of particles on the flow field, pressure and efficiency of an annular jet pump were analysed based on the RNG k-ε turbulence model and the Mixture multiphase flow model. The efficiency of the annular jet pump decreases with a higher particle bulk density. Specifically, at an initial concentration of 20% and a flow ratio (M) of 0.5, the efficiency of the annular jet pump fluctuates as follows: it changes from 28.736% under single-phase flow conditions to 25.011%, 24.369%, 23.637%, 22.950%, and 21.733% as the density of particulate matter increases. The findings of this study offer valuable theoretical insights for the implementation of annular jet pumps in engineering discharge applications.

A Three-dimensional CFD Study on Multiphase Flow in an FCC Regenerator Integrated with Oxy-combustion

A Three-dimensional CFD Study on Multiphase Flow in an FCC Regenerator Integrated with Oxy-combustion