Article
Engineering, Chemical
M. Sheikholeslami, Seyyed Ali Farshad
Summary: This study proposes the use of hybrid nanomaterials, including fin and helical turbulator, to enhance the efficiency of the absorber unit. The results of numerical simulations show that increasing the diameter of circular gaps facilitates fluid movement, reduces pressure loss, and improves the mixing of hot and cold fluids. As the pitch factor decreases, the rotation of helical tapes increases, leading to an increase in the number of circular gaps. The temperature of the absorber plate decreases with increasing Reynolds number, while it increases with the augmentation of the diameter of circular gaps and the pitch factor.
ADVANCED POWDER TECHNOLOGY
(2022)
Article
Environmental Sciences
Nguyen Van Hap, Phan Thanh Nhan, Huynh Phuoc Hien, Nguyen Minh Phu
Summary: Hybrid turbulators with perforated circular segment as vortex generator were used to enhance the heat transfer rate in an air collector duct. The effects of key parameters, including Reynolds numbers, angles of attack, and segment arrangements, on heat transfer and pressure loss were investigated. The results showed that an attack angle of 30 degrees provided the best thermohydraulic performance, while an angle of 60 degrees caused significant turbulence and pressure loss.
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
(2023)
Article
Environmental Sciences
Nguyen Van Hap, Phan Thanh Nhan, Huynh Phuoc Hien, Nguyen Minh Phu
Summary: Hybrid turbulators have been studied as a solution for enhancing heat transfer in fluid channels. This study focused on using a perforated circular segment as a vortex generator in an air collector duct and investigated the effects of different parameters on heat transfer and thermohydraulic performance. The results showed that an attack angle of 30 degrees provided the best performance.
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
(2023)
Article
Thermodynamics
G. Bois
Summary: This article addresses the issue of reduced models to describe turbulent two-phase flows in industrial applications and derives a spatially-averaged mixture or drift-flux model. The final model describes the evolution of mixture variables, including effects of turbulence, velocity, pressure, and enthalpy local non-equilibrium. The study also introduces a new path to calibrate closure laws or propose new models.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Thermodynamics
Ahmad Shafee, M. Sheikholeslami, M. Jafaryar, Fatih Selimefendigil, M. M. Bhatti, Houman Babazadeh
Summary: The study found that with the increase of pitch ratio, the decrement trend for secondary flow strengthens, leading to a decrease in convective flow and a greater exergy drop.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2021)
Article
Thermodynamics
Hongliang Wang, Azher M. Abed, A. Al-Zubaidi, Ahmed Deifalla, Ahmed M. Galal, Yanan Zhou, S. P. Ghoushchi
Summary: In this research, a numerical study was conducted to investigate the effects of a new form of aerodynamically designed turbulators, which are concentrically perforated, on the hydro-thermal parameters. The results showed that the hole area and geometry have a significant effect on the thermal performance.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2023)
Article
Mathematics
Saliha Nouri, Zouhaier Hafsia, Salah Mahmoud Boulaaras, Ali Allahem, Salem Alkhalaf, Baowei Feng
Summary: This study numerically investigated the three-dimensional turbulent core annular flow (CAF) regime and compared two different inlet configurations, showing that the T-junction (3D-T) configuration gave more appropriate results.
JOURNAL OF MATHEMATICS
(2021)
Article
Mathematics, Applied
Amos Natido, Tomasz J. Kozubowski
Summary: We present a new stochastic model that combines uniform and Laplace distributions. Theoretical properties and computational issues of parameter estimation using expectation-maximization schemes are discussed. Performance of the estimation algorithm is tested on synthetic data and a data example is provided to demonstrate the modeling potential of this methodology. A related model involving a mixture of uniform and exponential distributions is also studied.
JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS
(2023)
Article
Thermodynamics
Reza Beigzadeh, Smith Eiamsa-ard
Summary: This research applied a fuzzy logic approach to approximate the airflow thermal characteristic and flow friction in a heat exchanger equipped with diamond-shaped turbulators arranged in tandem. Increasing or decreasing the cone angle and tail length ratio was found to increase heat transfer and pressure loss. The fuzzy model showed good accuracy in predicting the Nusselt number and friction factor.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2021)
Article
Engineering, Multidisciplinary
A. Farajollahi, A. Mokhtari, M. Rostami, K. Imani, M. Salimi
Summary: This study investigates the turbulent flow of a nanofluid inside a heat exchanger tube equipped with conical turbulators. The effects of the number of turbulators, number of holes, and volume fraction of nanoparticles on flow field and heat transfer are numerically analyzed. The results show that the proposed turbulators have a significant effect on heat transfer, and the presence of holes reduces pressure drop. The use of perforated conical turbulators improves the performance evaluation criterion by creating controlled turbulent flows.
Article
Economics
Mika Meitz, Pentti Saikkonen
Summary: This paper considers testing for regime switching when the regime switching probabilities are time-varying and depend on observed data, specifically in mixture autoregressive models. The study finds that the likelihood ratio test has a nonstandard asymptotic distribution that can be simulated easily, and Monte Carlo studies demonstrate its good performance in terms of sample size and power properties.
JOURNAL OF ECONOMETRICS
(2021)
Article
Engineering, Mechanical
Tingyun Yin, Giorgio Pavesi
Summary: In this study, the flow characteristics of a pitching hydrofoil were numerically investigated. The results showed that reducing the empirical coefficient in the turbulence model improved the prediction of hydraulic performance at high angles of attack. The dynamic behavior of the laminar separation bubble was strongly influenced by the pitching method and velocity.
JOURNAL OF FLUIDS AND STRUCTURES
(2022)
Article
Thermodynamics
Roohollah Babaei Mahani, Amir Ahmadi, Hossein Mahdavi Hezaveh, Mohammad Sepehrirad, Pouyan Talebizadehsardari
Summary: This study investigated the impact of factors such as turbulators, hybrid nanofluid, and Reynolds number on heat transfer. The results showed significant enhancements in heat transfer rates, ranging from 79.49% to 97.5%, by changing the parameters under study.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2021)
Article
Thermodynamics
Kai Sun, Dong Liu, S. P. Ghoushchi, Tuo Zhao, Xijie Chen, Bashir Salah, Wenqi Zhao
Summary: The utilization of magnetic turbulators is a novel method to enhance heat transfer in heat exchangers. This research introduces both simple and perforated magnetic turbulators to optimize the thermal enhancement factor. The perforated magnetic turbulator, consisting of a magnet and a perforated oscillator, acts as a flow disruptor by inducing an alternating magnetic field around the tube.
APPLIED THERMAL ENGINEERING
(2023)
Article
Chemistry, Multidisciplinary
Wenqian Lin, Ruifang Shi, Jianzhong Lin
Summary: The study investigates the distribution and deposition of cylindrical nanoparticles in a turbulent pipe flow, showing that the particle concentration becomes non-uniform along the flow direction. The particles tend to align with their major axis near the flow direction, especially with increasing particle aspect ratio. Additionally, particles near the wall have a more obvious alignment with the flow direction compared to those in the center of the pipe.
APPLIED SCIENCES-BASEL
(2021)
Article
Engineering, Mechanical
Rico H. T. Hooijschuur, Niranjan Saikumar, S. Hassan HosseinNia, Ron A. J. van Ostayen
Summary: This paper presents the development and dynamic evaluation of a contactless sensing system for an air-bearing based precision wafer positioning system. The system utilizes a thin film of air to float the substrate and avoid damage and contamination. A cascaded control design is implemented to optimize the performance and handle vibration disturbances. The contactless sensor is analyzed for its performance.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Kh. Hosseinzadeh, M. A. Erfani Moghaddam, SeyedKeivan Nateghi, Mohammad Behshad Shafii, D. D. Ganji
Summary: This study aimed to maximize thermal performance by simulating a curved porous star-shaped enclosure with a rounded cavity. The temperature difference between the inner cavity and outer surface stirred the heat flux. By investigating factors such as porosity, radiation intensity, magnetic field, and natural convection, optimal values were determined.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2023)
Article
Chemistry, Physical
M. Habibnia, M. Sheikholeslami, S. M. Tabarhoseini, Ali Taheri, M. Sheykhi
Summary: This study focuses on the evaluation of cutting fluids in the turning process. The results show that employing nanofluid minimum quantity lubrication strategy can lead to an average temperature reduction of about 60% in the cutting tool during Mo40 steel turning. Furthermore, increasing the concentration of the nanofluid can further decrease the temperature.
JOURNAL OF MOLECULAR LIQUIDS
(2023)
Article
Physics, Applied
Payam Jalili, Hossein Narimisa, Bahram Jalili, D. D. Ganji
Summary: This study investigated a rotating system of micro-polar nanofluid between two parallel plates under the influence of magnetic and electric fields. The impacts of Nusselt number, skin friction, and Sherwood number on temperature, velocity, and concentration distribution were discussed. The results demonstrated the effects of rotation, Brownian motion, thermophoresis analysis, and Hall current on the micro-polar nanofluid.
MODERN PHYSICS LETTERS B
(2023)
Article
Energy & Fuels
Hossein Nabi, Mosayeb Gholinia, Mehdi Khiadani, Abdellah Shafieian
Summary: This paper investigates the impact of red wine-rGO/H2O nanofluid and paraffin wax on the thermohydraulic properties of a photovoltaic/thermal system. Numerical simulations demonstrate that innovative serpentine tube designs significantly enhance the system's performance. The use of environmentally friendly materials such as red wine-rGO/H2O nanofluid and paraffin wax further improves the electrical and thermal efficiency of the system.
Article
Mathematics, Interdisciplinary Applications
Hossein Jafari, Roghayeh Moallem Ganji, Davood Domiri Ganji, Zakia Hammouch, Yusif S. S. Gasimov
Summary: In this paper, the study of fuzzy differential equations (FDEs) in fuzzy calculus is discussed, which provides a proper model to address real problems with uncertainties. Specifically, a class of fuzzy differential equations (FFDEs) with non-integer or variable order (VO) is considered. The main problem is converted to a new problem by utilizing the r-cut representation and is solved using operational matrices (OMs) based on shifted Legendre polynomials (SLPs), leading to a system of nonlinear algebraic equations. The accuracy of the proposed technique is confirmed with an example.
FRACTALS-COMPLEX GEOMETRY PATTERNS AND SCALING IN NATURE AND SOCIETY
(2023)
Article
Multidisciplinary Sciences
M. Jafaryar, M. Sheikholeslami
Summary: In this paper, the application of new structure and loading Graphene nanoparticles to enhance thermal storage systems has been studied. Aluminum layers were used in the paraffin zone, which has a melting temperature of 319.55 K. The paraffin zone was located in the middle section of a triplex tube, with uniform hot temperatures (335 K) applied to both walls of the annulus. Three container geometries were tested by changing the angle of fins (alpha = 7.5 degrees, 15 degrees, and 30 degrees). A homogeneous model with uniform concentration of additives was assumed for property prediction. The results show that loading Graphene nanoparticles decreases the melting time by about 4.98% when alpha = 7.5 degrees, and the impact of phi improves by about 5.2% when the angle is reduced from 30 degrees to 7.5 degrees. Furthermore, as the angle decreases, the melting period decreases by approximately 76.47%, which is associated with an increase in driving force (conduction) in geometries with lower alpha.
SCIENTIFIC REPORTS
(2023)
Article
Construction & Building Technology
Z. Khalili, M. Sheikholeslami
Summary: The lack of an enhanced cooling system for Photovoltaic (PV) cells is addressed by offering a new system configuration utilizing numerical approach. A new layer for thermoelectric has been added to increase electrical output. The cooling system contains cooling ducts and confined jets, with hybrid nanofluid as the working fluid. The numerical method simulation confirms the effectiveness of the proposed system.
SUSTAINABLE CITIES AND SOCIETY
(2023)
Article
Energy & Fuels
M. Sheikholeslami
Summary: The influence of porous media on the solidification of water with hybrid nanoparticles has been simulated in this study. A tree-shaped fin and the impact of radiation were utilized to expedite the process. The hybrid nanomaterial consisted of a mixture of Al2O3 and CuO with a volume fraction of 0.01 for each powder type, making the homogeneous mixture approximation logical. A wiremesh packed approach was used to model the porous foam, and the impact of porosity on the freezing process was analyzed. The temperature equation, including two source terms for radiation and phase changing, was considered, and the Galerkin method was implemented for solving the equations.
JOURNAL OF ENERGY STORAGE
(2023)
Article
Thermodynamics
Bahram Jalili, Hassan Roshani, Payam Jalili, Mohammad Jalili, Pooya Pasha, Davood Domiri Ganji
Summary: This paper investigates the behavior of a 2D steady, laminar, and incompressible viscous fluid between two porous disks under an external magnetic field. The study is divided into two interconnected parts. In the first part, the dimensionless equations of the nanofluid flow between the disks are analyzed using the Akbari-Ganji Method (AGM) and compared with numerical results. The second part focuses on using the Finite Element Method (FEM) in CFD software to study the fluid parameters of two different types of nanotubes.
CASE STUDIES IN THERMAL ENGINEERING
(2023)
Article
Mathematics, Interdisciplinary Applications
Marcin B. Kaczmarek, Hassan HosseinNia
Summary: In this paper, a fractional-order extension of a negative position feedback (NPF) controller for active damping is proposed. The controller design is motivated by frequency-domain loop shaping analysis and maintains the high-pass characteristics of an integer-order NPF. Experimental results demonstrate the efficiency and feasibility of the proposed fractional-order controller.
FRACTAL AND FRACTIONAL
(2023)
Article
Thermodynamics
Mehran Ghasemian, M. Sheikholeslami, Maziar Dehghan
Summary: This study applies numerical techniques to assess the integration of twisted tapes in different cross-sectional tubes of Photovoltaic/Thermal (PV/T) collector units, and the impact on system performance. Computational fluid dynamics is used to evaluate PV/T systems with cylindrical, rectangular, and triangular cross-sectional tubes, with and without twisted tapes. Various pitch-to-width ratios (YD) of twisted tapes and total inlet mass flow rates are considered. The analysis of energy and exergy is carried out to evaluate system performance. The results show that the triangular cross-sectional tube is optimal without twisted tapes, but the cylindrical tube with twisted tapes outperforms other designs in terms of electrical and thermal aspects. The addition of a twisted tape in the cylindrical tube increases electrical efficiency by 7.2% and 9%, respectively. Furthermore, integrating twisted tapes with the lowest pitch-to-width ratio reduces surface temperature by 3.2℃ and 17.55℃ compared to systems with cylindrical tubes and PV alone.
Article
Energy & Fuels
M. Jafaryar, M. Sheikholeslami
Summary: Regarding the thermal management of the storage unit, one possible solution is to use an extended surface made of highly conductive metallic materials. This study suggests four different arrangements of the system by changing the number and thickness of plates, and solid matrix made of Silicon Carbide, Aluminum, and Stainless Steel. Additionally, loading alumina nanoparticles improves the heat absorption of the phase change material. Increasing the number of radial plates and reducing their thickness enhances heating penetration. The best case in terms of melting speed is achieved when using 40 plates with a thickness of 0.5 mm made of SiC material, resulting in a 87.84% reduction in melting time compared to the worst case.
JOURNAL OF ENERGY STORAGE
(2023)
Article
Construction & Building Technology
M. Sheikholeslami, Z. Khalili
Summary: A new configuration of photovoltaic-thermal unit with a thermoelectric layer has been proposed to enhance electrical performance. The system includes a circular duct with a turbulator and a mini channel with jet impingement for hybrid nanofluid flow. By selecting the turbulator with the highest revolution, the electrical efficiency improves by about 1.41% and useful heat increases by about 5.72%. The best case equipped with confined jets achieves an electrical performance of 15.50% and a thermal performance of 85.30%, with a temperature uniformity improvement of about 46.89%.
JOURNAL OF BUILDING ENGINEERING
(2023)
Article
Construction & Building Technology
M. Sheikholeslami, Hazim R. A. Al-Hussein
Summary: This study combines Trombe wall with paraffin layer and fins for solar energy saving and ventilation purposes. Alumina nanoparticles are loaded into pure paraffin to enhance the performance. Two heat generation terms are added to consider solar irradiation, and temperature equations with heat sources are applied for modeling different layers. The impacts of fins' thickness, length, and paraffin layer's position are investigated. The system with Y-shaped fins shows higher liquid fraction and lower heat loss, leading to a 28.41% increase in heat capacity at 17:00 with the best configuration.
JOURNAL OF BUILDING ENGINEERING
(2023)
