The paper presents the estimate of hydrodynamic parameters of the gas phase motion at low-temperature fractionation of boron trifluoride in a packed column. The following parameters are detected: density and viscosity...
详细信息
The paper presents the estimate of hydrodynamic parameters of the gas phase motion at low-temperature fractionation of boron trifluoride in a packed column. The following parameters are detected: density and viscosity for reacting phases in the operational temperature range, gas velocity at the phase inversion point, Reynolds number, and retention capacity for the investigated types of packed beds. Using the Logos software, numerical simulation of gas velocity and pressure distribution in the packed bed is performed for fractionation of boron trifluoride.
Membrane-based gas separation (GS) has emerged as a competitive separation technology for industrial gas separation applications due to its simpler operation and cost-effective approach. This paper reviews the computa...
详细信息
Membrane-based gas separation (GS) has emerged as a competitive separation technology for industrial gas separation applications due to its simpler operation and cost-effective approach. This paper reviews the computational parameters and boundary conditions involved in model simulations, including the general assumptions made for the gas separation process. The transport mechanisms used for dense and porous gas separation membranes are discussed, followed by verification studies of CFD models. The impacts of different operation parameters, such as the temperature, pressure ratio, variation in hydrodynamics, and membrane se-lectivity, on membrane performance are evaluated in terms of gas permeation flux and con-centration polarisation (CP). This review also describes the effect of obstacles (feed spacers) and various unsteady flow approaches for improving performance. Finally, challenges and future perspectives in CFD simulation involving membrane gas separation are provided. (c) 2023 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
Purpose The purpose of this paper is to experimentally and numerically investigate the cooling performance of the air-to-water thermoelectric cooling system under different working conditions. Design/methodology/appro...
详细信息
Purpose The purpose of this paper is to experimentally and numerically investigate the cooling performance of the air-to-water thermoelectric cooling system under different working conditions. Design/methodology/approach An air-to-water thermoelectric cooling system was designed and manufactured according to the principle of discrete binary thermoelectric Peltier modules, and the thermal performance, heat transfer rate and average COP values were examined at different cooling water temperatures and voltages applied. Additionally, numerical simulations were performed by computational fluid dynamics approach to investigate the temperature distribution and airflow structure inside the cooling chamber. Findings Analyses were performed using experimental tests and numerical methods. It was concluded that, by decreasing the cooling water temperature from 20 to 5 degrees C, the average COP increases about 36%. The voltage analysis showed that the efficiency of the system does not always increase as the voltage rises;more importantly, the optimum voltage is different and depends on whether it is desired to increase COP or increase the cooling rate. Originality/value In the studies published in the field of thermoelectric cooling systems, little attention has been paid to the voltage applied and its relationship to other operating conditions. In most cases, the tests are performed at a constant voltage. In this study, several options, including applied voltage and cooling water temperature, were considered simultaneously and their effects on performance have been tested. It was found that under such studies, optimization work should be done to evaluate maximum performance in different working conditions.
We performed computational fluid dynamics (CFD) simulations of the contaminant transport with adsorption filtration inside a planar-shaped air-purifying respirator (APR) canister and predicted the breakthrough times o...
详细信息
We performed computational fluid dynamics (CFD) simulations of the contaminant transport with adsorption filtration inside a planar-shaped air-purifying respirator (APR) canister and predicted the breakthrough times of the canisters with various internal shapes. The numerical modeling of the adsorption process based on the backward dif-ferentiation formulas, which comprise the implicit method implemented in COMSOL Multiphysics, demonstrated the validity through the simulations of the fixed-bed column breakthrough test. Model parameters were estimated by applying Bayesian inference to the breakthrough test and pressure drop measurement data. Previous CFD studies as-sessed the filtering efficiency based on the local flow speed and mean air age;this ap-proach replaced adsorption modeling, which is computationally expensive. We tested six planar-shaped APR canisters and observed that the dead zone near the walls in the air age field does not appear in the contaminant transport simulation with adsorption modeling. We identified that the velocity fields inside the filter determined the breakthrough dis-tributions. Further, we confirmed that the breakthrough time was more related to the maximum flow speed inside the filter and less with local mean air age. We demonstrated the importance of simulating contaminant transport with adsorption modeling for the APR canister and reliability of the alternative indices.& COPY;2023 Published by Elsevier Ltd on behalf of Institution of Chemical Engineers.
A channel box installation in the IEA-R1 research reactor core was numerically investigated to increase fluid flow in fuel assemblies (FAs) and side water channels (SWCs) between FAs by minimizing bypasses in specific...
详细信息
A channel box installation in the IEA-R1 research reactor core was numerically investigated to increase fluid flow in fuel assemblies (FAs) and side water channels (SWCs) between FAs by minimizing bypasses in specific regions of the reactor core, which is expected to reduce temperatures and oxidation effects in lateral fuel plates (LFPs). To achieve this objective, an isothermal three-dimensional computational fluid dynamics model was created using Ansys CFX to analyze fluid flow distribution in the Brazilian IEA-R1 research reactor core. All regions of the core and realistic boundary conditions were considered, and a detailed mesh convergence study is presented. Results comparing both scenarios are presented in the percentage of use of the primary circuit pump. It is indicated that 21.4% of fluid bypass to unnecessary regions can be avoided with the channel box installation, which leads to the total mass flow from the primary circuit for all FAs increasing from 68.9% (without a channel box) to 77.6% (with a channel box). For the SWCs, responsible for cooling LFPs, an increment from 9.7% to 22.4%, avoiding all nondesired cross three-dimensional effects, was observed, resulting in a more homogeneous fluid flow and vertical velocities. It was concluded that the installation of a channel box numerically indicates an expressive mass flow increase and homogeneous fluid flow distribution for flow dynamics in relevant regions. This gives greater confidence to believe that lower temperatures, and consequently oxidation effects in LFPs, can be expected with a channel box installation.
Braking distance, particularly the emergency braking distance at high speed, is essential to ensuring safety. Aerodynamic drag and negative lift can be effectively increased by setting up a plate at the rear of the ca...
详细信息
Braking distance, particularly the emergency braking distance at high speed, is essential to ensuring safety. Aerodynamic drag and negative lift can be effectively increased by setting up a plate at the rear of the car, thus improving the grip of the tires and reducing the braking distance. The Ahmed car model was selected for the numerical simulation. The aerodynamic behavior of the car with different configurations of plates at different opening angles was simulated using an improved delayed detached eddy simulation based on the shear stress transfer k-omega turbulence model, and the numerical method used in this study was verified using wind tunnel tests. Results showed that the upstream plate is optimal for increasing the car aerodynamic braking performance and noticeably reduces the fluctuation in aerodynamic forces. The aerodynamic drag is more sensitive to the installation position of the plate than aerodynamic lift. The aerodynamic forces on the car body and plate increase as the opening angle and size increase (except for the aerodynamic lift of a car body with a downstream plate), and the greatest effect is on the car body. Aerodynamic braking distance decreases as the opening angle and size of the plate increase, especially for the upstream plate. The optimal opening angle of the downstream plate is approximately 70 degrees, and the braking effect is not significantly because of the small downstream plate.
A 3D computational fluid dynamics (CFD) framework is presented to model and explain critical aerodynamic interactions occurring in the printhead during aerosol jet printing (AJP) with multi-stage flow focusing lenses....
详细信息
A 3D computational fluid dynamics (CFD) framework is presented to model and explain critical aerodynamic interactions occurring in the printhead during aerosol jet printing (AJP) with multi-stage flow focusing lenses. AJP has demonstrated great potential to fabricate complex circuits and conductive devices for numerous applications, including flexible electronics, medical diagnostic devices, and fuel cells. However, the devices manufactured by AJP are currently relegated to prototype roles due to poor repeatability of the deposited structures. The lack of process consistency in AJP arises from an incomplete understanding of causal aerodynamic interactions that influence the structure and repeatability of the printed features. Herein, a comprehensive CFD framework is presented to analyze the effects of gas flow rates, nozzle geometry, stand-off distance, printhead design, and aerosol droplet size on the resolution and morphology of printed features. Compressible NavierStokes equations with a k-epsilon turbulence model are solved to simulate flow conditions in the aerosol jet printhead. Additionally, a Lagrangian discrete phase model is used to simulate the transport of aerosolized ink droplets through the turbulent shear flow. The results highlight the crucial role of the design of the mist tube and the first aerodynamic lens, the density of the sheath gas, and the size of the droplets in the aerosol stream in determining print resolution and quality. A favorable comparison was found between numerically calculated results and experimental data obtained using the NanoJetTM system. CFD models presented in this work are expected to aid in identifying optimal process windows a priori, to improve process consistency.
Immobilized metal affinity chromatography (IMAC) ensures the specific purification of proteins contain-ing histidine tags through high affinity with transition metal chelators, which has various applications in biolog...
详细信息
Immobilized metal affinity chromatography (IMAC) ensures the specific purification of proteins contain-ing histidine tags through high affinity with transition metal chelators, which has various applications in biological protein separation. Most chromatographic separations currently use a fixed bed. In this form, internal flow pressure drops very sharply, accompanied by uneven solution flow, pore blockages, etc., all of which greatly reduce separation efficiency. Therefore, this study uses hollow fiber membranes (HFMs) with micron-scale inner diameters as a base, thus reducing operating pressure and significantly enhanc-ing mass transmission. Batch adsorption experiments were performed using flat plate membranes to ob-tain the reaction's thermodynamic and kinetic model parameters for use in a dynamic column break-through simulation. The numerical simulation was based on a single HFM model and established a math-ematical model for computational fluid dynamics (CFD) in ANSYS Fluent software. Model accuracy was validated by combining the simulation with experiments. The effects of different module and process pa-rameters on the breakthrough curve were investigated by varying parameters such as flow rate, initial feed concentration, and HFM inner diameter. Design parameters and operating conditions contributing to module utilization were subsequently obtained.(c) 2022 Published by Elsevier B.V.
computational fluid dynamics and fuzzy logic (FL) modeling methods were used to estimate heat transfer and fluid flow characteristics in conical spiral tubes. The effects of coil pitch p and cone angle theta at Reynol...
详细信息
computational fluid dynamics and fuzzy logic (FL) modeling methods were used to estimate heat transfer and fluid flow characteristics in conical spiral tubes. The effects of coil pitch p and cone angle theta at Reynolds numbers Re of 1500-5500 on flow and heat transfer were investigated. Water with an inlet temperature of 298 K was considered as the working fluid, and a constant wall temperature of 398 K was used in the study. FL was used to predict the Nusselt number and friction factor in conical spiral tubes as functions of Re, theta, and p. FL is an efficient method for predicting complex systems and is a valuable complement to classical hard computing techniques. The purpose of the study was to find a relationship between heat exchanger parameters and performance characteristics. It was also investigated how the FL expert system plays an important role in predicting heat transfer performance.
The aim of the study is to numerically analyze the active rear wing and select the optimum combination of an airfoil(s) to improve the cornering speed of a Mustang GT 2017 high-performance car. Rear wings are used in ...
详细信息
暂无评论