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Computational Fluid Mechanics and Heat Transfer
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Computational Fluid Mechanics and Heat Transfer

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Energy Science and Technology".

Deadline for manuscript submissions: closed (30 September 2021) | Viewed by 47094

Special Issue Editor

Prof. Dr. Seong Hyuk Lee

E-Mail Website
Guest Editor
Professor, School of Mechanical Engineering, Chung-Ang University, Seoul 06974, Korea
Interests: computational fluid dynamics; multiphysics simulation; turbulence; evaporation/condensation/frosting phenomena; interfacial dynamics

Special Issue Information

Dear Colleagues,

Until recently, it has been impractical or impossible to solve the complicated fluid mechanical problems with multiphysics phenomena without using computational fluid dynamics (CFD). Indeed, computational fluid dynamics (CFD) is a rapidly evolving science that solves the equations of flow motion, such as Navier–Stokes equations numerically, to get quantitative or qualitative predictions for fluid flows together with heat transfer, multi-phase flows, combustion, and so on. However, the drastic development of computer capabilities and numerical methods could lead to better solutions for parametric studies, optimization, and flow-physics investigations that would not be obtained by theoretical or experimental approaches.

We are inviting the the submission of manuscripts to this Special Issue on “computational fluid mechanics and heat transfer.” This Special Issue aims to cover computational fluid dynamics studies, including heat transfer, multiphase flows, combustion, and relevant multiphysics. In particular, we welcome research articles as well as review articles on the significant recent progress of computational methods and innovative CFD applications.

Prof. Dr. Seong Hyuk Lee
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Turbulence
  • Heat transfer
  • Two-phase flows
  • Free-surface flows
  • Fluid–solid interactions
  • Navier–Stokes solution for incompressible and compressible flows
  • Lattice Boltzmann method
  • Chemical reactions and combustion
  • Microfluidics
  • Porous media
  • Heat exchanger design and other applications
  • Other relevant topics.

Published Papers (18 papers)

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11 pages, 2603 KiB  
Article
Model for Cryogenic Flashing LNG Leak
by Boon How Lim and Eddie Yin Kwee Ng
Appl. Sci. 2021, 11(19), 9312; https://0-doi-org.brum.beds.ac.uk/10.3390/app11199312 - 08 Oct 2021
Cited by 4 | Viewed by 2627
Abstract
The growth of liquefied natural gas (LNG)’s importance for curbing greenhouse gas emissions has increased the interest in understanding LNG’s risks, particularly regarding small-diameter leaks (<25 mm). Recently, INERIS performed a series of pressurized LNG release experiments for orifice sizes of up to [...] Read more.
The growth of liquefied natural gas (LNG)’s importance for curbing greenhouse gas emissions has increased the interest in understanding LNG’s risks, particularly regarding small-diameter leaks (<25 mm). Recently, INERIS performed a series of pressurized LNG release experiments for orifice sizes of up to 9 mm. Based on INERIS findings and the Isenthalpic Homogeneous Equilibrium Model (HEM), this paper created a leak model for flashing LNG leak. The leak model consists of nine equations and quantifies leak parameters for risk assessment. One potential use of this leak model is providing an equivalent leak boundary condition for computational fluid dynamic (CFD) simulation to predict gas dispersion. Using the leak model as input, FLACS gas dispersion simulation was carried out for one INERIS experiment leak case. Compared to TR56, the Singapore safety guideline for LNG bunkering, the dispersion result does not contradict the expected plume reach. Further validation with risk analysis tools and actual experiments is needed to confirm that the leak model is fit for use. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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18 pages, 6617 KiB  
Article
Numerical Investigation of the Effect of Air Leaking into the Working Fluid on the Performance of a Steam Ejector
by He Li, Xiaodong Wang, Jiuxin Ning, Pengfei Zhang and Hailong Huang
Appl. Sci. 2021, 11(13), 6111; https://0-doi-org.brum.beds.ac.uk/10.3390/app11136111 - 30 Jun 2021
Cited by 1 | Viewed by 1558
Abstract
This paper investigated the effect of air leaking into the working fluid on the performance of a steam ejector. A simulation of the mixing of air into the primary and secondary fluids was performed using CFD. The effects of air with a 0, [...] Read more.
This paper investigated the effect of air leaking into the working fluid on the performance of a steam ejector. A simulation of the mixing of air into the primary and secondary fluids was performed using CFD. The effects of air with a 0, 0.1, 0.3 and 0.5 mass fraction on the entrainment ratio and internal flow structure of the steam ejector were studied, and the coefficient distortion rates for the entrainment ratios under these air mass fractions were calculated. The results demonstrated that the air modified the physical parameters of the working fluid, which is the main reason for changes in the entrainment ratio and internal flow structure. The calculation of the coefficient distortion rate of the entrainment ratio illustrated that the air in the primary fluid has a more significant impact on the change in the entrainment ratio than that in the secondary fluid under the same air mass fraction. Therefore, the air mass fraction in the working fluid must be minimized to acquire a precise entrainment ratio. Furthermore, this paper provided a method of inspecting air leakage in the experimental steam ejector refrigeration system. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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19 pages, 7454 KiB  
Article
Two-Phase Flow Simulations Using 1D Centerline-Based C- and U-Shaped Pipe Meshes
by Thinh Quy Duc Pham, Jichan Jeon, Daeseong Jo and Sanghun Choi
Appl. Sci. 2021, 11(5), 2020; https://0-doi-org.brum.beds.ac.uk/10.3390/app11052020 - 25 Feb 2021
Cited by 2 | Viewed by 2322
Abstract
This study aims to investigate the pressure changes, bubble dynamics, and flow physics inside the U- and C-shaped pipes with four different gravitational directions. The simulation is performed using a 1D centerline-based mesh generation technique along with a two-fluid model in the open-source [...] Read more.
This study aims to investigate the pressure changes, bubble dynamics, and flow physics inside the U- and C-shaped pipes with four different gravitational directions. The simulation is performed using a 1D centerline-based mesh generation technique along with a two-fluid model in the open-source software, OpenFOAM v.6. The continuity and momentum equations of the two-fluid model are discretized using the pressure-implicit method for the pressure-linked equation algorithm. The static and hydrostatic pressures in the two-phase flow were consistent with those of single-phase flow. The dynamic pressure in the two-phase flow was strongly influenced by the effect of the buoyancy force. In particular, if the direction of buoyancy force is the same as the flow direction, the dynamic pressure of the air phase increases, and that of the water phase decreases to satisfy the law of conservation of mass. Dean flows are observed on the transverse plane of the curve regions in both C-shaped and U-shaped pipes. The turbulent kinetic energy is stronger in a two-phase flow than in a single-phase flow. Using the 1D centerline-based mesh generation technique, we demonstrate the changes in pressure and the turbulent kinetic energy of the single- and two-phase flows, which could be observed in curve pipes. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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23 pages, 11859 KiB  
Article
The Transient Flow behind an Instantaneously Started Circular Cylinder with Two Symmetrical Strips
by Jialiang Zhou, Guoyong Jin, Tiangui Ye, Kai Wang and Kailang Sun
Appl. Sci. 2020, 10(7), 2308; https://0-doi-org.brum.beds.ac.uk/10.3390/app10072308 - 27 Mar 2020
Viewed by 2070
Abstract
The finite volume method, based on the dynamic mesh method, is used to investigate the transient viscous incompressible flow around an impulsively and translationally started cylinder with strips. The strips of different shapes are installed at different locations on the surface of the [...] Read more.
The finite volume method, based on the dynamic mesh method, is used to investigate the transient viscous incompressible flow around an impulsively and translationally started cylinder with strips. The strips of different shapes are installed at different locations on the surface of the cylinder. The main purpose of this paper is to investigate the influence of the locations and shapes of strips on the flow caused by boundary motion. The present solutions agree well with the experimental results reported in literature. Six placement angles of strips were selected: 0°, 20°, 60°, 90°, 120° and 150°. The development of wake shows some new phenomena with different strip locations, and the significant difference appears at α = 90°. The vortex intensity is much larger than that of other locations. On the other hand, four shapes of strips were selected: arc, triangle, rectangle and trapezoid. The rectangular strips had the greatest influence on the drag coefficient and the maximum of the drag coefficient increased from 0.4 to 2.8, compared with the smooth cylinder. The maximum of negative velocity had the most significant change when the shape of strip is arc, increasing by 34% compared with the smooth cylinder, at T = 3. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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10 pages, 2916 KiB  
Article
CFD-Based Metamodeling of the Propagation Distribution of Styrene Spilled from a Ship
by Chan Ho Jeong, Min Kyu Ko, Moonjin Lee and Seong Hyuk Lee
Appl. Sci. 2020, 10(6), 2109; https://0-doi-org.brum.beds.ac.uk/10.3390/app10062109 - 20 Mar 2020
Cited by 1 | Viewed by 1937
Abstract
The present study aimed to numerically establish a new metamodel for predicting the propagation distribution of styrene, which is one of the hazardous and noxious substances (HNSs) spilled from ships. Three-dimensional computational fluid dynamics (CFD) simulations were conducted for 80 different scenarios to [...] Read more.
The present study aimed to numerically establish a new metamodel for predicting the propagation distribution of styrene, which is one of the hazardous and noxious substances (HNSs) spilled from ships. Three-dimensional computational fluid dynamics (CFD) simulations were conducted for 80 different scenarios to gather large amounts of data on the spatial distribution of the change in concentration over time. We used the commercial code of ANSYS Fluent (V.17.2) to solve the Reynolds-averaged Navier–Stokes equations, together with the scalar transport equation. Based on the CFD results, we adopted the well-known kriging model to create a metamodel that estimated the propagation velocity and spatial distributions by considering the effect of the current surface velocity, deep current velocity, surface layer depth, and crack position. The results show that the metamodel accurately predicted the changes in the local distribution of styrene over time. This model was also evaluated using the hidden-point test. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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15 pages, 14292 KiB  
Article
Numerical Investigations on the Blade Tip Clearance Excitation Forces in an Unshrouded Turbine
by Yang Pan, Qi Yuan, Gongge Huang, Jiawei Gu, Pu Li and Guangyu Zhu
Appl. Sci. 2020, 10(4), 1532; https://0-doi-org.brum.beds.ac.uk/10.3390/app10041532 - 24 Feb 2020
Cited by 4 | Viewed by 2463
Abstract
The purpose of this study was to investigate the characteristics of the blade tip excitation forces represented as the rotordynamic coefficients (stiffness and damping coefficients) in an unshrouded turbine using the three-dimensional computational fluid dynamic (CFD) numerical method. The blade geometrical parameters were [...] Read more.
The purpose of this study was to investigate the characteristics of the blade tip excitation forces represented as the rotordynamic coefficients (stiffness and damping coefficients) in an unshrouded turbine using the three-dimensional computational fluid dynamic (CFD) numerical method. The blade geometrical parameters were based on a SNECMA transonic experimental rig. The simulations were performed by solving the compressible Reynolds-averaged Navier–Stokes (RANS) equations. The multi-frequency elliptical whirling orbit model and an improved mesh deformation method based on the transient analysis were utilized. The effects of operating conditions on the rotordynamic coefficients and the unsteady flow were also found. The results show that the positive direct stiffness, which confirmed the direct force contribution in the tip excitation forces and the cross-coupling stiffness, were dependent on the whirling frequencies. Damping effects were shown to be negligible. The rotational speed, inlet flow angle, eccentric ratio (ER), and mean tip clearance had impacts on the stiffness, and some effects of these variables on the rotordynamic coefficients were found to be frequency dependent. Additionally, increasing the rotor eccentricity and the mean tip clearance led to the nonuniformity of the circumferential pressure distributions. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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15 pages, 3219 KiB  
Article
Numerical Investigation of Mixing Characteristic for CH4/Air in Rotating Detonation Combustor
by Shan Jin, Qingyang Meng, Zhiming Li, Ningbo Zhao, Hongtao Zheng and Jialong Yang
Appl. Sci. 2020, 10(4), 1298; https://0-doi-org.brum.beds.ac.uk/10.3390/app10041298 - 14 Feb 2020
Viewed by 1903
Abstract
The mixing process of fuel and oxidizer is a very critical factor affecting the real operating performance of non-premixed rotating detonation combustor. In this paper, a two-dimensional numerical study is carried out to investigate the flow and mixing characteristics of CH4/air [...] Read more.
The mixing process of fuel and oxidizer is a very critical factor affecting the real operating performance of non-premixed rotating detonation combustor. In this paper, a two-dimensional numerical study is carried out to investigate the flow and mixing characteristics of CH4/air in combustor with different injection structures. On this basis, the effect of CH4/air mixing on the critical ignition energy for forming detonation is theoretically analyzed in detail. The numerical results indicate that injection strategies of CH4 and air can obviously affect the flow filed characteristic, pressure loss, mixing uniformity and local equivalence ratio in combustor, which further affect the critical ignition energy for forming detonation. In the study for three different mass flow rates (the mass flow rates of air are 12.01 kg/s,8.58 kg/s and 1.72 kg/s, respectively), when air is radially injected into combustor (fuel/air are injected perpendicular to each other), although the mixing quality of CH4 and air is improved, the total pressure loss is also increased. In addition, the comparative analysis also shows that the increase of mass flow rate of CH4/air can decrease the difference of the critical ignition energy for forming detonation at a constant total equivalence ratio. The ignition energy decreases with the decrease of the total flow rate and then increases gradually. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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33 pages, 16479 KiB  
Article
CFD-Rotordynamics Sequential Coupling Simulation Approach for the Flow-Induced Vibration of Rotor System in Centrifugal Pump
by Hehui Zhang, Haolin You, Haishan Lu, Kun Li, Zhiyong Zhang and Liangxing Jiang
Appl. Sci. 2020, 10(3), 1186; https://0-doi-org.brum.beds.ac.uk/10.3390/app10031186 - 10 Feb 2020
Cited by 6 | Viewed by 4182
Abstract
Vibration of the rotor system is closely related with the operation stability of centrifugal pump, and it is inevitably induced by the unsteady inner flow. An unsteady computational fluid dynamics model coupling with a rotordynamics model was presented, and the corresponding numerical calculation [...] Read more.
Vibration of the rotor system is closely related with the operation stability of centrifugal pump, and it is inevitably induced by the unsteady inner flow. An unsteady computational fluid dynamics model coupling with a rotordynamics model was presented, and the corresponding numerical calculation program, including a self-designed rotordynamics code, was developed on the commercial package ANSYS Workbench. The validity of the numerical calculation model was verified by a hydraulic performance and vibration test based on an industrial centrifugal pump. The hydraulic radial forces on impeller, pressure pulsation, deformation, and vibration of the main shaft under nine different flow rates were systematically investigated and explained preliminarily from the view of inner unstable flow. Results show that the blade passing frequency is the dominant frequency in the fluctuation of the above dynamical behaviors, which is closely related to the rotor–stator interaction between the impeller and volute casing. This study built the connection between internal fluid flow in the centrifugal pump and the vibration of its external rotor structure, and may provide theoretical references for the design of vibration-reducing and safety monitoring strategies design of centrifugal pumps. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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17 pages, 3266 KiB  
Article
Darcy–Boussinesq Model of Cilia-Assisted Transport of a Non-Newtonian Magneto-Biofluid with Chemical Reactions
by Ali Ahmad Farooq, Zahir Shah, Poom Kumam, Ebraheem O. Alzahrani, Meshal Shutaywi and Talha Anwar
Appl. Sci. 2020, 10(3), 1137; https://0-doi-org.brum.beds.ac.uk/10.3390/app10031137 - 07 Feb 2020
Cited by 17 | Viewed by 2494
Abstract
The model developed in this study presents a mathematical approach to the physiological transport of seminal liquid due to ciliary movements, which are attached with the lumen of the ductile efferent in the male reproductive system. The rheological properties of the seminal liquids [...] Read more.
The model developed in this study presents a mathematical approach to the physiological transport of seminal liquid due to ciliary movements, which are attached with the lumen of the ductile efferent in the male reproductive system. The rheological properties of the seminal liquids were described using the Jeffrey liquid model. The problem described an electromagnetic mixed convective flow of a Jeffrey liquid through a vertical channel with heat and mass transfers. The effects of chemical reactions and the external heat generation were included in the formulation. The flow took place through an active porous medium (due to thick cilia mat and other deposits) and was influenced by the Lorentz magnetic force. Four basic conservation laws of mass, momentum, energy, and concentration were utilized in the mathematical modeling. These are highly nonlinear equations, which were simplified due to a physiologically valid approach known as LAT (lubrication approximation theory). Analytical solutions for temperature, concentration, and velocity profiles were evaluated. The expressions describing the pressure–volume flow rate relationships were also obtained. Analysis of various physical and geometrical factors affecting the pressure–volume (pumping) characteristics was also presented. One of the main findings of our study is that the difference between our calculated values of the flow rate and the estimated values of the flow rate in the ductile efferent was negligibly small. Moreover, our results can be implemented in the artificial cilia pumping systems in microchannels. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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17 pages, 9547 KiB  
Article
A Study on Flow Characteristics and Flow Uniformity for the Efficient Design of a Flow Frame in a Redox Flow Battery
by Bo-Ra Kim, Deok-Young Sohn, Yun-Ho Choi and Yong-Hee Lee
Appl. Sci. 2020, 10(3), 929; https://0-doi-org.brum.beds.ac.uk/10.3390/app10030929 - 31 Jan 2020
Cited by 5 | Viewed by 3270
Abstract
As global environmental problems are worsening, the efficiency of storage systems for renewable energy are gaining importance. The redox flow battery (RFB), a promising energy storage system (ESS), is a device that generates or stores electricity through reduction–oxidation reactions between active materials constituting [...] Read more.
As global environmental problems are worsening, the efficiency of storage systems for renewable energy are gaining importance. The redox flow battery (RFB), a promising energy storage system (ESS), is a device that generates or stores electricity through reduction–oxidation reactions between active materials constituting electrolytes. Herein, we proposed a flow frame design that reduces flow resistance in the flow path and causes uniform flow distribution in the electrode to develop an efficient redox flow battery. Through computational fluid dynamics (CFD) and experimental verification, we investigated the flow characteristics and flow uniformity inside the conventional redox flow battery cell. An analysis of the flow characteristics of the conventional flow frame revealed a non-uniform distribution of the flow discharged to the electrodes, owing to the complex (branched) flow path geometry of the inlet channel. To address this problem, we proposed a new flow frame design that removed and integrated bifurcations in the flow path. This new design significantly improved flow uniformity parameters, such as the symmetry coefficient ( C s y m ), variability range coefficient ( R i ), and maximum flow rate deviation ( D m ). Ultimately, we decreased the pressure drop by 15.3% by reducing the number of flow path bifurcations and chevron repositioning. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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14 pages, 3070 KiB  
Article
On the Cattaneo–Christov Heat Flux Model and OHAM Analysis for Three Different Types of Nanofluids
by Umair Khan, Shafiq Ahmad, Arsalan Hayyat, Ilyas Khan, Kottakkaran Sooppy Nisar and Dumitru Baleanu
Appl. Sci. 2020, 10(3), 886; https://0-doi-org.brum.beds.ac.uk/10.3390/app10030886 - 29 Jan 2020
Cited by 42 | Viewed by 3122
Abstract
In this article, the boundary layer flow of a viscous nanofluid induced by an exponentially stretching surface embedded in a permeable medium with the Cattaneo–Christov heat flux model (CCHFM) is scrutinized. We took three distinct kinds of nanoparticles, such as alumina (Al2 [...] Read more.
In this article, the boundary layer flow of a viscous nanofluid induced by an exponentially stretching surface embedded in a permeable medium with the Cattaneo–Christov heat flux model (CCHFM) is scrutinized. We took three distinct kinds of nanoparticles, such as alumina (Al2O3), titania (TiO2) and copper (Cu) with pure water as the base fluid. The features of the heat transfer mechanism, as well as the influence of the relaxation parameter on the present viscous nanofluid flow are discussed here thoroughly. The thermal stratification is taken in this phenomenon. First of all, the problem is simplified mathematically by utilizing feasible similarity transformations and then solved analytically through the OHAM (optimal homotopy analysis method) to get accurate analytical solutions. The change in temperature distribution and axial velocity for the selected values of the specific parameters has been graphically portrayed in figures. An important fact is observed when the thermal relaxation parameter (TRP) is increased progressively. Graphically, it is found that an intensification in this parameter results in the exhaustion of the fluid temperature together with an enhancement in the heat transfer rate. A comparative discussion is also done over the Fourier’s law and Cattaneo–Christov model of heat. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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17 pages, 6471 KiB  
Article
3-D Modeling of Gas–Solid Two-Phase Flow in a π-Shaped Centripetal Radial Flow Adsorber
by Haoyu Wang, Xiong Yang, Ziyi Li, Yingshu Liu, Chuanzhao Zhang, Xiaojun Ma and Chunwang Li
Appl. Sci. 2020, 10(2), 614; https://0-doi-org.brum.beds.ac.uk/10.3390/app10020614 - 15 Jan 2020
Cited by 2 | Viewed by 3157
Abstract
Radial flow adsorber (RFA) is widely used in large-scale pressure swing adsorption (PSA) oxygen production system because of high air separation. In this study, a 3-D modeling of gas–solid two-phase flow was established for the π-shaped centripetal RFA (CP-π RFA). The pressure difference, [...] Read more.
Radial flow adsorber (RFA) is widely used in large-scale pressure swing adsorption (PSA) oxygen production system because of high air separation. In this study, a 3-D modeling of gas–solid two-phase flow was established for the π-shaped centripetal RFA (CP-π RFA). The pressure difference, temperature changes, velocity profiles and oxygen distributions were comparatively studied using this model. Part of the results have been compared with the experiments results, which shows this model can give an accurately prediction. The results show that the pressure and velocity in the adsorber change greatly near the outer hole and central hole, but the overall pressure and velocity changes in the bed are stable. The oxygen product purity in the adsorbent filling area performed better on oxygen enrichment after eight cycles. The oxygen product flow rate will affect the oxygen production performance. The laws of the pressure, velocity, temperature and oxygen distributions can provide an important technical reference for CP-π RFA in the PSA for oxygen production. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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14 pages, 2924 KiB  
Article
Thermally Stratified Darcy Forchheimer Flow on a Moving Thin Needle with Homogeneous Heterogeneous Reactions and Non-Uniform Heat Source/Sink
by Muhammad Ramzan, Naila Shaheen, Seifedine Kadry, Yeu Ratha and Yunyoung Nam
Appl. Sci. 2020, 10(2), 432; https://0-doi-org.brum.beds.ac.uk/10.3390/app10020432 - 07 Jan 2020
Cited by 22 | Viewed by 2408
Abstract
This study discusses the flow of viscous fluid past a moving thin needle in a Darcy–Forchheimer permeable media. The novelty of the envisioned mathematical model is enhanced by adding the effects of a non-uniform source/sink amalgamated with homogeneous–heterogeneous (hh) reactions. The MATLAB bvp4c [...] Read more.
This study discusses the flow of viscous fluid past a moving thin needle in a Darcy–Forchheimer permeable media. The novelty of the envisioned mathematical model is enhanced by adding the effects of a non-uniform source/sink amalgamated with homogeneous–heterogeneous (hh) reactions. The MATLAB bvp4c function is employed to solve the non-linear ordinary differential equations (ODEs), which are obtained via similarity transformations. The outcomes of numerous parameters are explicitly discussed graphically. The drag force coefficient and heat transfer rate are considered and discussed accordingly. It is comprehended that higher estimates of variable source/sink boost the temperature profile. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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17 pages, 9793 KiB  
Article
Numerical Investigation on Flow Characteristics and Aerodynamic Performance of a 1.5-Stage SCO2 Axial-Inflow Turbine with Labyrinth Seals
by Qiuwan Du and Di Zhang
Appl. Sci. 2020, 10(1), 373; https://0-doi-org.brum.beds.ac.uk/10.3390/app10010373 - 03 Jan 2020
Cited by 9 | Viewed by 3087
Abstract
The leakage problem of supercritical carbon dioxide (SCO2) axial-inflow turbine brings great challenges to the efficiency and security of the power system. Labyrinth seals are usually utilized to improve the leakage characteristics of the blade tip. In this paper, a 1.5-stage [...] Read more.
The leakage problem of supercritical carbon dioxide (SCO2) axial-inflow turbine brings great challenges to the efficiency and security of the power system. Labyrinth seals are usually utilized to improve the leakage characteristics of the blade tip. In this paper, a 1.5-stage SCO2 axial-inflow turbine is established and labyrinth seals are arranged on the top of the first stage stator and rotor blades. The effects of seal clearance, groove on seal cavity surface and circle groove shape on flow characteristics and aerodynamic performance under different pressure ratio are investigated. Increasing seal clearance can significantly weaken the turbine performance. Arranging rectangle, circle and V-shaped grooves on the seal cavity surface near the outlet of the seal gap can enhance the energy dissipation, reduce the relative leakage and improve the power and efficiency. Increasing the groove width can improve the aerodynamic performance while the effect of the groove depth is weak. The configuration where the circle groove width is 50% of the pitch of seal tooth achieves the best performance with the relative leakage of stator1 and rotor, power and efficiency of 6.04 × 10−3, 8.09 × 10−3, 3.467 MW and 86.86% respectively. With an increase in pressure ratio, the relative leakage increases firstly and then remains almost constant. The power increases while the efficiency increases firstly and then decreases, reaching the peak value under the design condition. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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17 pages, 3166 KiB  
Article
Analysis of Flow Characteristics and Pressure Drop for an Impinging Plate Fin Heat Sink with Elliptic Bottom Profiles
by Zhipeng Duan, Xianghui Lv, Hao Ma, Liangbin Su and Mengqiao Zhang
Appl. Sci. 2020, 10(1), 225; https://0-doi-org.brum.beds.ac.uk/10.3390/app10010225 - 27 Dec 2019
Cited by 9 | Viewed by 4056
Abstract
The performance of impingement air cooled plate fin heat sinks differs significantly from that of parallel flow plate fin heat sinks. The impinging flow situations at the entrance and the right-angled bends of the plate fin heat sink are quite involved. Flow characteristics [...] Read more.
The performance of impingement air cooled plate fin heat sinks differs significantly from that of parallel flow plate fin heat sinks. The impinging flow situations at the entrance and the right-angled bends of the plate fin heat sink are quite involved. Flow characteristics of a plate fin heat sink with elliptic bottom profiles cooled by a rectangular impinging jet with different inlet widths are studied by numerical simulations. The results of pressure drop of numerical simulations and experimental results match quite well. The numerical results show that at the same flow rate, the pressure drop decreases with the increase of the impingement inlet width, and the pressure drop increases significantly with the increase of the fin height. The larger the impingement inlet width of air-cooled plate fin heat sink, the milder the pressure drop changes with velocity. Pressure drop for an impinging plate fin heat sink without elliptic bottom profiles is larger than that with elliptic bottom profiles at the same inlet width and velocity. Based on the fundamental developing laminar continuum flow theory, an improved model which is very concise and nice for quick real world approximations is proposed. Furthermore, this paper verifies the effectiveness of this simple impinging pressure drop model. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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14 pages, 6995 KiB  
Article
Impact of Nonlinear Chemical Reaction and Melting Heat Transfer on an MHD Nanofluid Flow over a Thin Needle in Porous Media
by Muhammad Ramzan, Hina Gul, Seifedine Kadry, Chhayly Lim, Yunyoung Nam and Fares Howari
Appl. Sci. 2019, 9(24), 5492; https://0-doi-org.brum.beds.ac.uk/10.3390/app9245492 - 13 Dec 2019
Cited by 13 | Viewed by 1889
Abstract
A novel mathematical model is envisioned discussing the magnetohydrodynamics (MHD) steady incompressible nanofluid flow with uniform free stream velocity over a thin needle in a permeable media. The flow analysis is performed in attendance of melting heat transfer with nonlinear chemical reaction. The [...] Read more.
A novel mathematical model is envisioned discussing the magnetohydrodynamics (MHD) steady incompressible nanofluid flow with uniform free stream velocity over a thin needle in a permeable media. The flow analysis is performed in attendance of melting heat transfer with nonlinear chemical reaction. The novel model is examined at the surface with the slip boundary condition. The compatible transformations are affianced to attain the dimensionless equations system. Illustrations depicting the impact of distinct parameters versus all involved profiles are supported by requisite deliberations. It is perceived that the melting heat parameter has a declining effect on temperature profile while radial velocity enhances due to melting. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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13 pages, 2832 KiB  
Article
Artificial Radiation Frost Chamber for Frost Formation on Tea
by Yong-Zong Lu, Yong-Guang Hu, Jin-Tao Tian, Huan Song and Richard L. Snyder
Appl. Sci. 2019, 9(22), 4726; https://0-doi-org.brum.beds.ac.uk/10.3390/app9224726 - 06 Nov 2019
Cited by 6 | Viewed by 2155
Abstract
The Yangtze River region is the main production area for famous, high-quality tea in China. Radiation frost frequently occurs in this region, especially in the early spring during calm and clear nights, and it causes substantial damage to crops, which leads to huge [...] Read more.
The Yangtze River region is the main production area for famous, high-quality tea in China. Radiation frost frequently occurs in this region, especially in the early spring during calm and clear nights, and it causes substantial damage to crops, which leads to huge economic losses for tea growers. The formation of frost is difficult to experimentally control due to the complexity and variability of the agro-micrometeorological environment. The objective of this study was to evaluate an artificial radiation frost chamber based on the temperature difference between leaf and air dew point, which was designed for advanced frost-related research. Micro-meteorological data and the frost formation process were monitored in an experimental tea field during typical radiation frost nights to mimic declining temperatures that are consistent with nature. The radiation frost chamber model and main parameters were determined by theoretical calculations and computational fluid dynamics (CFD) simulation. A frost-forming experiment was conducted to evaluate the performance of the frost chamber. The observation results showed that the greatest temperature difference between leaf and air dew point (Tdiffer) was −2.3 °C. The simulation results showed that the desublimation cooling rate of the air vapor was greater than sublimation, and the Tdiffer should be greater than −3.2 °C, which could cause frost to easily form on the leaf. The performance testing results showed that leaf temperature slowly declined after a rapid decrease, which is similar to the natural condition, which results in noticeable frost formation on the leaf. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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1 pages, 141 KiB  
Erratum
Erratum: Kim, B.-R., et al. A Study on Flow Characteristics and Flow Uniformity for the Efficient Design of a Flow Frame in a Redox Flow Battery. Appl. Sci. 2020, 10, 929
by Applied Sciences Editorial Office
Appl. Sci. 2021, 11(3), 978; https://0-doi-org.brum.beds.ac.uk/10.3390/app11030978 - 22 Jan 2021
Viewed by 1113
Abstract
We wish to make the following corrections to the published paper [...] Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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