Pub Date : 2023-09-01DOI: 10.47176/jafm.16.09.1755
A. Nikkhoo, A. Esmaeili
In order to upsurge the maneuverability of micro aerial vehicles, a tubercle leading edge inspired by the whale flipper was applied as a passive stall control method. Although this method could be useful to control stall phenomena, the effect of geometrical properties on the flow physic should be investigated to reach the root of them. According to preceding research, the effect of some parameters on the tubercle leading edge wing is a hot topic among researchers. The aim of this research is to explore the effects of sectional wing geometries like amplitude, wavelength, thickness, maximum thickness location, and camber on the aerodynamic feature of full-span tubercle leading edge wing, particularly at 22 degree in post-stall circumstances. The results present that by reducing the amplitude about 2.5%c, the lift coefficient upsurges by about 3.5%; instead, the drag coefficient reduces about 6%. On the other hand, by decreasing the wavelength from 46.2%c to 11.7%c, the drag coefficient and the lift coefficient decrease by about 15% and 19%, respectively. Furthermore, as the thickness rises from 10.55%c to 18.14%c, the lift and drag coefficient goes down about 9.4% and 2.9%, respectively. Furthermore, by increasing the camber from 2.56%c to 3.34%c, the lift to drag ratio goes down by about 1.06%. Finally, by raising the last design variable (maximum thickness location) from 0.26c to 0.51c, the lift to drag ratio increases about 13.7%.
{"title":"Numerical Study of Geometrical Properties of Full-Span Tubercle Leading Edge Wing at Post-Stall Condition","authors":"A. Nikkhoo, A. Esmaeili","doi":"10.47176/jafm.16.09.1755","DOIUrl":"https://doi.org/10.47176/jafm.16.09.1755","url":null,"abstract":"In order to upsurge the maneuverability of micro aerial vehicles, a tubercle leading edge inspired by the whale flipper was applied as a passive stall control method. Although this method could be useful to control stall phenomena, the effect of geometrical properties on the flow physic should be investigated to reach the root of them. According to preceding research, the effect of some parameters on the tubercle leading edge wing is a hot topic among researchers. The aim of this research is to explore the effects of sectional wing geometries like amplitude, wavelength, thickness, maximum thickness location, and camber on the aerodynamic feature of full-span tubercle leading edge wing, particularly at 22 degree in post-stall circumstances. The results present that by reducing the amplitude about 2.5%c, the lift coefficient upsurges by about 3.5%; instead, the drag coefficient reduces about 6%. On the other hand, by decreasing the wavelength from 46.2%c to 11.7%c, the drag coefficient and the lift coefficient decrease by about 15% and 19%, respectively. Furthermore, as the thickness rises from 10.55%c to 18.14%c, the lift and drag coefficient goes down about 9.4% and 2.9%, respectively. Furthermore, by increasing the camber from 2.56%c to 3.34%c, the lift to drag ratio goes down by about 1.06%. Finally, by raising the last design variable (maximum thickness location) from 0.26c to 0.51c, the lift to drag ratio increases about 13.7%.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45941851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.47176/jafm.16.09.1805
A. Bennia, A. Reffas, M. A. Khan, H. E. Mohamadi, M. Lateb, H. Fellouah
When reducing the energy prerequisites of buildings, the correct distribution of fresh air flows injected into the living rooms poses a problem. If the problem of mixing the injected air in the ambient air is not effectively solved, there will be a strong deterioration in air quality and comfort. In this research, a new design of swirling diffuser is investigated experimentally and numerically using large eddy simulations. The influence of fins is studied for the improvement of air diffusion and jet mixing with ambient air. The study was carried out for a fins angle of 30° with the jet's axis and 60° with the blowing orifice's plane with the condition of uniform heat flux of the air. The working fluid used is air. It has been validated that using fins leads to a greater spreading of the jet and good air mixing compared to those obtained from smooth tubes (circular nozzle). To enhance the accuracy of the turbulence models' predictions, three turbulence models are tested: the wall-adapting local eddy-viscosity turbulence model (LES/WALEVM), Smagorinski-Lilly (LES/S-LM) model and the kinetic-energy transport model (LES/K-ETM). It is worth highlighting that the LES/K-ETM model is well established in the prediction of swirling flows, which have been successfully compared with experimental results.
{"title":"Experimental and Numerical Dynamic Investigation of a Swirling Jet: Application to Improve the Efficiency of Air Diffusion in an Occupied Zone","authors":"A. Bennia, A. Reffas, M. A. Khan, H. E. Mohamadi, M. Lateb, H. Fellouah","doi":"10.47176/jafm.16.09.1805","DOIUrl":"https://doi.org/10.47176/jafm.16.09.1805","url":null,"abstract":"When reducing the energy prerequisites of buildings, the correct distribution of fresh air flows injected into the living rooms poses a problem. If the problem of mixing the injected air in the ambient air is not effectively solved, there will be a strong deterioration in air quality and comfort. In this research, a new design of swirling diffuser is investigated experimentally and numerically using large eddy simulations. The influence of fins is studied for the improvement of air diffusion and jet mixing with ambient air. The study was carried out for a fins angle of 30° with the jet's axis and 60° with the blowing orifice's plane with the condition of uniform heat flux of the air. The working fluid used is air. It has been validated that using fins leads to a greater spreading of the jet and good air mixing compared to those obtained from smooth tubes (circular nozzle). To enhance the accuracy of the turbulence models' predictions, three turbulence models are tested: the wall-adapting local eddy-viscosity turbulence model (LES/WALEVM), Smagorinski-Lilly (LES/S-LM) model and the kinetic-energy transport model (LES/K-ETM). It is worth highlighting that the LES/K-ETM model is well established in the prediction of swirling flows, which have been successfully compared with experimental results.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46269262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.47176/jafm.16.09.1742
S. Aboudaoud, S. Touzani, S. Abderafi, A. Cheddadi
The hydrodynamic behaviour of air-glass beads bubbling fluidized bed reactor containing spherical glass beads is numerically studied, using OpenFoam v7 CFD software. Both Gidaspow and Syamlal-O'Brien drag models are used to calculate momentum exchange coefficients. Simulation predictions of pressure loss, bed expansion rate, and air volume fraction parameters were compared and validated using data, existing in the literature obtained experimentally and performed by other numerical softwares. Pressure loss and rate of bed expansion were calculated with relative root mean square error (RMSE) equal to 0.65 and 0.095 respectively; Syamlal-O'Brien model is considered more accurate than Gidaspow model. Hence, numerical model reliability developed on OpenFoam was also proved. The hydrodynamic aspect study of the fluidized bed reactor was then performed, to analyse the impact of inlet air velocity (U) on particles motion. It was revealed that with U increment, air and glass beads axial velocities increase in the reactor centre and decrease in the sidewalls. Thus, a greater particle bed expansion is induced and the solid particles accumulated highly on the reactor sidewalls. In general, with the increase of U, the solid volume fraction decreases from 0.63 to 0.58 observed at 0.065 m/s and 0.51 m/s, respectively.
{"title":"CFD Simulation of Air-Glass Beads Fluidized Bed Hydrodynamics","authors":"S. Aboudaoud, S. Touzani, S. Abderafi, A. Cheddadi","doi":"10.47176/jafm.16.09.1742","DOIUrl":"https://doi.org/10.47176/jafm.16.09.1742","url":null,"abstract":"The hydrodynamic behaviour of air-glass beads bubbling fluidized bed reactor containing spherical glass beads is numerically studied, using OpenFoam v7 CFD software. Both Gidaspow and Syamlal-O'Brien drag models are used to calculate momentum exchange coefficients. Simulation predictions of pressure loss, bed expansion rate, and air volume fraction parameters were compared and validated using data, existing in the literature obtained experimentally and performed by other numerical softwares. Pressure loss and rate of bed expansion were calculated with relative root mean square error (RMSE) equal to 0.65 and 0.095 respectively; Syamlal-O'Brien model is considered more accurate than Gidaspow model. Hence, numerical model reliability developed on OpenFoam was also proved. The hydrodynamic aspect study of the fluidized bed reactor was then performed, to analyse the impact of inlet air velocity (U) on particles motion. It was revealed that with U increment, air and glass beads axial velocities increase in the reactor centre and decrease in the sidewalls. Thus, a greater particle bed expansion is induced and the solid particles accumulated highly on the reactor sidewalls. In general, with the increase of U, the solid volume fraction decreases from 0.63 to 0.58 observed at 0.065 m/s and 0.51 m/s, respectively.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49658658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.47176/jafm.16.09.1735
D. Perdana, M. Hanifudin, M. K. Rosidin, W. A. Winarko
This study examines the effects of temperatures and directions of the magnetic fields in the combustion chambers on flame characteristics for boiler combustion in power generation systems by burning olive oil droplets. The variations in the temperature of the combustion chamber are 40°C, 50°C, and 60°C. Meanwhile, the directions of the magnetic fields are the repulsive magnetic field (north-north) and the attractive magnetic field (north-south). In the experiment, a droplet of olive oil was placed at a type K thermocouple junction between the two bar magnets. A 250 fps high-speed camera recorded the flame from its ignition to its extinction. The results of this study found that temperature and direction of the magnetic fields in the combustion chamber have an effect on the characteristics of the flame, where the attractive magnetic field (north-south) resulted in increased burning of droplets, round flame, low altitude, increased temperature, and shorter ignition delay time, compared to the repulsive magnetic field (north-north) and without a magnetic field. Furthermore, the combustion chamber temperatures of 40°C, 50°C, and 60°C produced flame temperatures of 799.94°C, 829.25°C, and 879.50°C, and flame heights of 5.97 mm, 5.35 mm, and 4.23 mm, respectively. The strong magnetic fields increased the concentration of oxygen and fuel molecules around the combustion reaction zone, causing shorter droplet combustion and releasing a large amount of energy. These findings are beneficial for designing efficient industrial heat generators with a magnetic field. The results of this study are therefore crucial as a basis for considering the substitution of fossil fuels with environmentally friendly vegetable oils.
{"title":"Characteristics of Olive Oil Droplet Combustion with Various Temperatures and Directions of Magnetic Fields in the Combustion Chamber","authors":"D. Perdana, M. Hanifudin, M. K. Rosidin, W. A. Winarko","doi":"10.47176/jafm.16.09.1735","DOIUrl":"https://doi.org/10.47176/jafm.16.09.1735","url":null,"abstract":"This study examines the effects of temperatures and directions of the magnetic fields in the combustion chambers on flame characteristics for boiler combustion in power generation systems by burning olive oil droplets. The variations in the temperature of the combustion chamber are 40°C, 50°C, and 60°C. Meanwhile, the directions of the magnetic fields are the repulsive magnetic field (north-north) and the attractive magnetic field (north-south). In the experiment, a droplet of olive oil was placed at a type K thermocouple junction between the two bar magnets. A 250 fps high-speed camera recorded the flame from its ignition to its extinction. The results of this study found that temperature and direction of the magnetic fields in the combustion chamber have an effect on the characteristics of the flame, where the attractive magnetic field (north-south) resulted in increased burning of droplets, round flame, low altitude, increased temperature, and shorter ignition delay time, compared to the repulsive magnetic field (north-north) and without a magnetic field. Furthermore, the combustion chamber temperatures of 40°C, 50°C, and 60°C produced flame temperatures of 799.94°C, 829.25°C, and 879.50°C, and flame heights of 5.97 mm, 5.35 mm, and 4.23 mm, respectively. The strong magnetic fields increased the concentration of oxygen and fuel molecules around the combustion reaction zone, causing shorter droplet combustion and releasing a large amount of energy. These findings are beneficial for designing efficient industrial heat generators with a magnetic field. The results of this study are therefore crucial as a basis for considering the substitution of fossil fuels with environmentally friendly vegetable oils.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49308731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.47176/jafm.16.09.1792
S. Ghodbane, A. Beniaiche, A. Belkallouche, B. Janssens
This paper proposes a novel design for a hybrid engine air-particle separator filter (HEAPS) that combines the vortex tube separator (VTS) with the inertial particle separator (IPS) to enhance separation efficiency. Helicopters often operate in harsh environments, such as deserts, and landing on unprepared runways poses a severe risk to turboshaft engines due to the ingestion of dust and sand. This can result in significant damage to the engine's rotating components, impacting its life, reliability, and performance. To protect the engine from erosion and damage, an engine air particle separator system (EAPS) is installed in the engine inlet. In this study, a comparative numerical simulation was conducted between the hybrid filter and the VTS using the commercial software ANSYS Fluent. The Reynolds-averaged Navier–Stokes equations (RANS) were used to simulate incompressible turbulent flow, and the trajectory of particles was tracked using the Discrete Phase Model (DPM). Particle trajectories and separation efficiency were analyzed for different particle sizes, inlet velocities, and bypass mass flow ratios between the scavenge channel and the core engine channel. The results show that the hybrid design provides excellent separation efficiency, with a recovery efficiency of over 97%.
{"title":"Numerical Investigation on Separation Efficiency of a Novel Hybrid Engine Air-Particle Separator","authors":"S. Ghodbane, A. Beniaiche, A. Belkallouche, B. Janssens","doi":"10.47176/jafm.16.09.1792","DOIUrl":"https://doi.org/10.47176/jafm.16.09.1792","url":null,"abstract":"This paper proposes a novel design for a hybrid engine air-particle separator filter (HEAPS) that combines the vortex tube separator (VTS) with the inertial particle separator (IPS) to enhance separation efficiency. Helicopters often operate in harsh environments, such as deserts, and landing on unprepared runways poses a severe risk to turboshaft engines due to the ingestion of dust and sand. This can result in significant damage to the engine's rotating components, impacting its life, reliability, and performance. To protect the engine from erosion and damage, an engine air particle separator system (EAPS) is installed in the engine inlet. In this study, a comparative numerical simulation was conducted between the hybrid filter and the VTS using the commercial software ANSYS Fluent. The Reynolds-averaged Navier–Stokes equations (RANS) were used to simulate incompressible turbulent flow, and the trajectory of particles was tracked using the Discrete Phase Model (DPM). Particle trajectories and separation efficiency were analyzed for different particle sizes, inlet velocities, and bypass mass flow ratios between the scavenge channel and the core engine channel. The results show that the hybrid design provides excellent separation efficiency, with a recovery efficiency of over 97%.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48012035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.47176/jafm.16.09.1626
N. Davandeh, †. M.J.Maghrebi
Numerous studies have been conducted to investigate effect of blade geometry of vertical axis wind turbine performance. Most of the evaluations have focused on the airfoil series and airfoil geometry parameters such as thickness and camber of the airfoil. Few studies have examined the effect of other blade geometry parameters on the vertical axis wind turbine performance. In the present study, the effect of geometric change in leading-edge radius (LER) of a vertical axis wind turbine performance has been numerically studied. Hence, modified NACA 0021 airfoil profiles were created using the geometric method (CST). Then, the flow behavior around a Darrieus vertical axis wind turbine was simulated under the influence of the reduction and set-up coefficients of the leading-edge radius at a constant wind speed of 9 m/s and a tip speed ratio of 1.5 to 3.5 using the computational fluid dynamics. Additionally, the effects of the examined parameter (leading-edge radius) on fluid flow and aerodynamic performance coefficients, including the coefficients of power and torque, were investigated. The results indicated that the leading-edge radius affected the near wake flow of the turbine, and the optimization of leading-edge radius parameter controls the dynamic stall and reduces the formation of a vortex. Finally, the optimization of LER revealed that at 20% reduction in the LER the performance of the turbine at tip speed ratio of 1.5 was increased by more than 50%. This reinforces the self-starting capability of a Darrieus wind turbine.
{"title":"Leading Edge Radius Effects on VAWT Performance","authors":"N. Davandeh, †. M.J.Maghrebi","doi":"10.47176/jafm.16.09.1626","DOIUrl":"https://doi.org/10.47176/jafm.16.09.1626","url":null,"abstract":"Numerous studies have been conducted to investigate effect of blade geometry of vertical axis wind turbine performance. Most of the evaluations have focused on the airfoil series and airfoil geometry parameters such as thickness and camber of the airfoil. Few studies have examined the effect of other blade geometry parameters on the vertical axis wind turbine performance. In the present study, the effect of geometric change in leading-edge radius (LER) of a vertical axis wind turbine performance has been numerically studied. Hence, modified NACA 0021 airfoil profiles were created using the geometric method (CST). Then, the flow behavior around a Darrieus vertical axis wind turbine was simulated under the influence of the reduction and set-up coefficients of the leading-edge radius at a constant wind speed of 9 m/s and a tip speed ratio of 1.5 to 3.5 using the computational fluid dynamics. Additionally, the effects of the examined parameter (leading-edge radius) on fluid flow and aerodynamic performance coefficients, including the coefficients of power and torque, were investigated. The results indicated that the leading-edge radius affected the near wake flow of the turbine, and the optimization of leading-edge radius parameter controls the dynamic stall and reduces the formation of a vortex. Finally, the optimization of LER revealed that at 20% reduction in the LER the performance of the turbine at tip speed ratio of 1.5 was increased by more than 50%. This reinforces the self-starting capability of a Darrieus wind turbine.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43726574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.47176/jafm.16.09.1752
Y. W. Zheng, J. Wang, J. Sun, C. Wang
In this study, a dynamic mixer was designed to mix polymer melts online during extrusion, and the flow of a polymer melt in a mixer was simulated using Polyflow software. The Orthogonal experiment was conducted to analyze the effects of three geometrical parameters (i.e. the length of entrance zone (Li), the gap between the rotor and wall (g), and the diameter of cone-shaped rotor (d2)) on mixing properties of a dynamic mixer. The Li, g, and d2 were optimized for the minimum product of segregation scale (S) and power consumption (P). Finally, the mixing properties of the dynamic mixer were compared with those of SK and SX static mixers. The results indicated that among the above-mentioned three parameters, the g was the most important parameter influencing S, and S∙P. The minimum S∙P of 1059 µm·W was obtained when the Li was 16 mm, the g was 1 mm, and the d2 was 24 mm. The S decreased with the increase of the rotation speed from 120 to 360 r/min, and increased with the increase of the flow rate from 15 to 45 mL/min. However, the P increased with the increase of both the rotation speed and flow rate. The maximum shear rate of the melt in the dynamic mixer was observed in the mixing zone, which was mainly affected by the rotation speed rather than the flow rate. To achieve the S of the same size, the length of the dynamic mixer was the shortest, and that of the SK static mixer was the longest. Moreover, to acquire the S of the same size, the dynamic mixer required the largest P, the SX static mixer needed a smaller P, and the SK static mixer required the minimum P.
{"title":"Design and Optimization of Online Dynamic Mixer and Its Performance Analysis","authors":"Y. W. Zheng, J. Wang, J. Sun, C. Wang","doi":"10.47176/jafm.16.09.1752","DOIUrl":"https://doi.org/10.47176/jafm.16.09.1752","url":null,"abstract":"In this study, a dynamic mixer was designed to mix polymer melts online during extrusion, and the flow of a polymer melt in a mixer was simulated using Polyflow software. The Orthogonal experiment was conducted to analyze the effects of three geometrical parameters (i.e. the length of entrance zone (Li), the gap between the rotor and wall (g), and the diameter of cone-shaped rotor (d2)) on mixing properties of a dynamic mixer. The Li, g, and d2 were optimized for the minimum product of segregation scale (S) and power consumption (P). Finally, the mixing properties of the dynamic mixer were compared with those of SK and SX static mixers. The results indicated that among the above-mentioned three parameters, the g was the most important parameter influencing S, and S∙P. The minimum S∙P of 1059 µm·W was obtained when the Li was 16 mm, the g was 1 mm, and the d2 was 24 mm. The S decreased with the increase of the rotation speed from 120 to 360 r/min, and increased with the increase of the flow rate from 15 to 45 mL/min. However, the P increased with the increase of both the rotation speed and flow rate. The maximum shear rate of the melt in the dynamic mixer was observed in the mixing zone, which was mainly affected by the rotation speed rather than the flow rate. To achieve the S of the same size, the length of the dynamic mixer was the shortest, and that of the SK static mixer was the longest. Moreover, to acquire the S of the same size, the dynamic mixer required the largest P, the SX static mixer needed a smaller P, and the SK static mixer required the minimum P.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48509162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.47176/jafm.16.09.1840
L. L. Feng, C. Cao, K. Zhong, H. Jia
In this study, the flow boiling heat transfer and pressure drop characteristics of refrigerant R134a in micro-channels were experimentally investigated. The tests were performed in circular horizontal micro-channels with inner diameters of 0.5 mm and 1 mm and a heating length of 300 mm. The mass velocities varied from 500 kg/m2s to 2500 kg/m2s, and the heat fluxes varied from 15 kW/m2 to 147 kW/m2. The heat transfer coefficient (HTC) and frictional pressure drop (FPD) were measured and discussed in detail. According to the results, HTC was significantly affected by heat flux, whereas it was independent of mass velocity. Nucleate boiling was the dominant heat transfer mechanism for R134a flow boiling in the micro-channels. In comparison to the 1 mm channel, the 0.5 mm channel shows better performance in heat transfer, with a maximum increase of approximately 22 %. In addition, FPD increased with increasing mass velocity and decreasing channel diameter. Finally, several existing correlations for HTC and FPD were evaluated by comparing them with the experimental values. Tran’s correlation (1996) presented a better agreement in terms of the average HTC, while for the FPD, the model of Kim and Mudawar (2013b) showed good prediction accuracy.
{"title":"Investigation of Flow Boiling in Micro-Channels: Heat Transfer, Pressure Drop and Evaluation of Existing Correlations","authors":"L. L. Feng, C. Cao, K. Zhong, H. Jia","doi":"10.47176/jafm.16.09.1840","DOIUrl":"https://doi.org/10.47176/jafm.16.09.1840","url":null,"abstract":"In this study, the flow boiling heat transfer and pressure drop characteristics of refrigerant R134a in micro-channels were experimentally investigated. The tests were performed in circular horizontal micro-channels with inner diameters of 0.5 mm and 1 mm and a heating length of 300 mm. The mass velocities varied from 500 kg/m2s to 2500 kg/m2s, and the heat fluxes varied from 15 kW/m2 to 147 kW/m2. The heat transfer coefficient (HTC) and frictional pressure drop (FPD) were measured and discussed in detail. According to the results, HTC was significantly affected by heat flux, whereas it was independent of mass velocity. Nucleate boiling was the dominant heat transfer mechanism for R134a flow boiling in the micro-channels. In comparison to the 1 mm channel, the 0.5 mm channel shows better performance in heat transfer, with a maximum increase of approximately 22 %. In addition, FPD increased with increasing mass velocity and decreasing channel diameter. Finally, several existing correlations for HTC and FPD were evaluated by comparing them with the experimental values. Tran’s correlation (1996) presented a better agreement in terms of the average HTC, while for the FPD, the model of Kim and Mudawar (2013b) showed good prediction accuracy.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43307845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-01DOI: 10.47176/jafm.16.08.1736
Z. Zhu, Y. Lv, X. Su, J. Zhang, R. Wang, W. Lu, J. Sun
Slurry transport pumps, the central equipment of deep-sea mining (DSM) systems, provide the lifting power required for lifting mineral ores from the seafloor to the surface. The current technical challenges are associated with transport security and the economic aspects of coarse ore particles in pumps and pipelines. This paper focuses on the transportation characteristics of slurry pumps and uses theoretical methods, numerical calculations, and experimental methods to identify a feasible working mode. The geometric parameters of impeller channels in pump hydraulics significantly influence the migration properties of particles which in turn affects the overall security and economy of the system. The ratio of the impeller cross-sectional area F2/F1 (F1: cross-sectional area of the impeller outlet; F2: cross-sectional area of the impeller inlet) affects the particle passing capacity but negatively impacts pump efficiency. The percent of particles in the excellent passage interval of 0.2 s to 0.25 s increases from 25 to 43% when the number increases from 1.57 to 2.51. The pump behavior increases of the head by 5–10 m, and the efficiency decreases by 5–10%. So, the recommended span of F2/F1 is 1.57–2.00, and satisfying particle passing ability and efficiency can be achieved in this range. This study can provide a reference for the commercial transportation of slurry ores for deep-sea mining systems.
{"title":"Balance of Efficiency and Security-influence on Slurry Transport from the Diffusion of Flow Passages of a Deep-sea Mining Pump","authors":"Z. Zhu, Y. Lv, X. Su, J. Zhang, R. Wang, W. Lu, J. Sun","doi":"10.47176/jafm.16.08.1736","DOIUrl":"https://doi.org/10.47176/jafm.16.08.1736","url":null,"abstract":"Slurry transport pumps, the central equipment of deep-sea mining (DSM) systems, provide the lifting power required for lifting mineral ores from the seafloor to the surface. The current technical challenges are associated with transport security and the economic aspects of coarse ore particles in pumps and pipelines. This paper focuses on the transportation characteristics of slurry pumps and uses theoretical methods, numerical calculations, and experimental methods to identify a feasible working mode. The geometric parameters of impeller channels in pump hydraulics significantly influence the migration properties of particles which in turn affects the overall security and economy of the system. The ratio of the impeller cross-sectional area F2/F1 (F1: cross-sectional area of the impeller outlet; F2: cross-sectional area of the impeller inlet) affects the particle passing capacity but negatively impacts pump efficiency. The percent of particles in the excellent passage interval of 0.2 s to 0.25 s increases from 25 to 43% when the number increases from 1.57 to 2.51. The pump behavior increases of the head by 5–10 m, and the efficiency decreases by 5–10%. So, the recommended span of F2/F1 is 1.57–2.00, and satisfying particle passing ability and efficiency can be achieved in this range. This study can provide a reference for the commercial transportation of slurry ores for deep-sea mining systems.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48410237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-01DOI: 10.47176/jafm.16.08.1741
Q. Li, R. Zhang, H. Xu
A double-volute molten salt pump with two outlet pipes is proposed based on the original pump model. A numerical approach coupling finite element analysis and computational fluid dynamics (CFD) is implemented to investigate the operational stability and energy performance of two molten salt centrifugal pumps for high-temperature molten salt. The entropy production of the single-volute and double-volute molten salt pumps is investigated. The effects of the volute structures on the mechanical behavior of the impeller and shaft are considered. According to the findings, the local entropy production in the molten salt pump is dominated by the local pulsating entropy production (Spro-T), with the double-volute scheme achieving reduced energy loss. A visualization of the flow field and the local entropy production rate (LEPR) distributions indicate that the LEPR is positively correlated with the complexity of the flow, and higher levels of turbulence intensity lead to greater LEPR. The double-volute scheme enhances the complexity of the flow in the impeller, resulting in an increase in the LEPR compared with the single-volute design. However, the LEPR in the whole double-volute molten salt pump is reduced compared with the single-volute design. It is discovered that the double-volute molten salt pump experiences a less radial hydraulic force. Although the double-volute design has a slightly higher maximum equivalent stress on the impeller than the single-volute scheme, the rotor deformation is significantly less. In general, the double-volute scheme reduces energy loss and ensures better structural stability.
{"title":"Effects of Volute Structure on Energy Performance and Rotor Operational Stability of Molten Salt Pumps","authors":"Q. Li, R. Zhang, H. Xu","doi":"10.47176/jafm.16.08.1741","DOIUrl":"https://doi.org/10.47176/jafm.16.08.1741","url":null,"abstract":"A double-volute molten salt pump with two outlet pipes is proposed based on the original pump model. A numerical approach coupling finite element analysis and computational fluid dynamics (CFD) is implemented to investigate the operational stability and energy performance of two molten salt centrifugal pumps for high-temperature molten salt. The entropy production of the single-volute and double-volute molten salt pumps is investigated. The effects of the volute structures on the mechanical behavior of the impeller and shaft are considered. According to the findings, the local entropy production in the molten salt pump is dominated by the local pulsating entropy production (Spro-T), with the double-volute scheme achieving reduced energy loss. A visualization of the flow field and the local entropy production rate (LEPR) distributions indicate that the LEPR is positively correlated with the complexity of the flow, and higher levels of turbulence intensity lead to greater LEPR. The double-volute scheme enhances the complexity of the flow in the impeller, resulting in an increase in the LEPR compared with the single-volute design. However, the LEPR in the whole double-volute molten salt pump is reduced compared with the single-volute design. It is discovered that the double-volute molten salt pump experiences a less radial hydraulic force. Although the double-volute design has a slightly higher maximum equivalent stress on the impeller than the single-volute scheme, the rotor deformation is significantly less. In general, the double-volute scheme reduces energy loss and ensures better structural stability.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41368221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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