Air Inlet Angle Research Articles

A Review on Heat Transfer Enhancement in a Heat Exchanger

Compact heat exchanger is commonly used in car radiators which is normally small with low flowrate. To produce a large surface area, thin plates or corrugated fins are attached closely separating the two fluids. Compact heat exchanger is normally used in applications where weight and volume are the significant factors for the enhancement of heat transfer. This paper reviews the research related to the characteristics, advantages and findings on various type of compact heat exchanger. It is found that the geometric parameters such as fin shape, tube shape, fin pitch, tube pitch, tube arrangement, tube angle and vortex generators affect the heat transfer performance in general. The air inlet angle of 45° and common flow upstream gives the optimum heat enhancement in most studies while the most suitable air flow is between 1.8 – 3.8 m/s.

The CPFD approach was used to investigate the particle flow characteristics and auxiliary air inlet in an ash transfer pipe

Numerical simulations for the air-solid two-phase flow in a horizontal pipe with a diameter of 125 mm and a length of 10 m were carried out using the Computational Particle Fluid Dynamics (CPFD) method. The deposition characteristics of particles in the pipe were investigated at various inlet flow rates and velocities, and the effect of the auxiliary inlet with different structural parameters on the evacuation of particles in the pipe after the auxiliary inlet was added to the horizontal pipe was compared. The results show that when the volume fraction of particles in the tube is less than 0.6, the flow of particles is relatively stable, and when the volume fraction of particles is greater than 0.8, the particles are seriously deposited and easily form a blockage; the auxiliary air inlet speed is proportional to the effect at the same tilt angle; when the air inlet speed is constant, the auxiliary air inlet angle increases from 35° to 55°, the effect of auxiliary air inlet increases and then decreases, and the effect of auxiliary air inlet reaches its peak at around 45°. The study's findings have implications for long-distance particle transport in horizontal pipelines.

Research on particle retention in continuous horizontal fluidized bed based on CFD-DEM method

Horizontal fluidized beds are widely used in continuous production lines due to their efficient heat and mass transfer mode. Continuous production goals require stabilized reaction systems, which can be achieved by controlling particle retention. But there is a lack of an effective means of controlling particle retention. In this paper, Computational Fluid Dynamics - Discrete Element Method (CFD-DEM) method is applied to investigate the particle retention in different air inlet angles, which is characterized by the particle back-mixing degree, spatial and residence time distribution. The results show that at low air inlet angles, the system is effective in controlling particle retention. This is achieved through stronger particle back-mixing and more concentrated residence times, which are essential for maintaining reaction system stability. These findings provide guidance for controlling particle retention and enhancing continuous fluidization equipment efficiency.

A study on optimization of the air supply system for the electric heating solid heat storage unit

An experimental and simulation study was carried out on the air supply system of the electric heating solid heat storage unit, aiming to improve the uniformity of the air supply system, thereby increasing the overall heating efficiency of the solid heat storage unit. The experiments show that non-uniform air distribution of the air system may cause non-uniform heat release of the heat accumulator, and the uniformity of the air supply system is greatly affected by the air supply structure and air inlet. By establishing a model of the heat storage device and conducting numerical simulation, the air distribution law of the air supply system was studied. According to the study results, the uniformity index of the air system was effectively improved by increasing the air cabin width and the air inlet angle, and adding a static pressure box at the air supply outlet, so that the flow velocity distribution of the air supply system was more uniform, which is of great significance to the overall optimization of the solid heat storage and heating system.

Design and Optimization of Pneumatic Separation Device for Plastic Evidence in Fire and Explosion Scene

To improve the efficiency of fire investigation, a horizontal pneumatic separator for separating plastic evidence from fire and explosion scenes is designed in this paper. Taking three kinds of material with different densities as separation objects, MATLAB was used to calculate the horizontal displacement of materials under different separation parameters based on the motion equation. A deviation coefficient was put forward to measure the separation effect. The effects of air inlet velocity and air inlet angle on the deviation coefficient of materials with different particle sizes were studied, and the optimal deviation coefficient was determined according to Taguchi methods.

Effects of the Air Inlet Angle on the Combustion and Ablation Environment of a Hybrid Powder-Solid Ramjet

A hybrid powder-solid ramjet (HPSR) that combined the advantages of a solid rocket ramjet (SRJ) and a powder ramjet engine was investigated in this research. To improve the combustion efficiency and optimize the inner wall thermal protection of the afterburner, the effects of the air inlet angle on the combustion and wall ablation environment were studied. The standard k - ε model, the eddy-dissipation model (EDM), and the boron particle ignition and combustion model were adopted to simulate the two-phase flow in the afterburners with different air inlet angles (45°, 60°, 75°, and 90°). The results showed that the global flow field and the distribution of the vortexes in the afterburner that had a significant influence on the ablation environment of the inner wall and the combustion efficiency were determined by the impact effect and the squeezing effect of the ram air on the primary fuel gas, which was affected by the air inlet angle. As the air inlet angle increased, the total combustion efficiency of the four cases first increased and then decreased, reaching 80.38%, 81.64%, 84.34%, and 83.26% for angles of 45°, 60°, 75°, and 90°, respectively. At the same time, the inner wall ablation became more severe because both the erosion effect of the condensed phase particles and the gas-flow scouring effect were enhanced, and a large temperature gradient was generated on the inner wall. The study results can provide a reference for designing the air inlet angle of an HPSR.

Optimization of the Heat Dissipation Structure for Lithium-Ion Battery Packs Based on Thermodynamic Analyses

The battery thermal management system plays an important role in electric vehicles, and determines the performance and the lifespan of electric vehicles. In this paper, optimization of the heat dissipation structure of lithium-ion battery pack is investigated based on thermodynamic analyses to optimize discharge performance and ensure lithium-ion battery pack safety. First, the heat generation and heat transfer model of the lithium-ion battery cell are derived based on thermodynamic theory. Then, the thermodynamic governing equations of battery are established based on Fluent, and the model is verified by comparing simulation data and experimental data. Afterwards, the simulation model of pure electric vehicles and the model of the heat generation rate are established using ADVISOR to analyze the dynamic performance of the battery pack. Finally, the air-cooling structure of the battery pack is designed according to the temperature field distribution obtained from the Fluent simulation, which is optimized using a back propagation neural network combined with genetic algorithms for the air flow rate, air flow channel spacing between cells, and air inlet angle. Based on the results of the optimized structure, the optimized structure effectively increases the heat dissipation performance and eliminates temperature inconsistency between the cells.

An Alternative Air Distribution System in Economy-Class Passenger Airplane for Infection Reduction

Airplane transportation has played a major role in the spread of the new corona virus COVID-19 all over the world. The current air distribution system used in airplanes circulation assists motion of contaminants and hence spreads airborne diseases. In this work, a new air distribution system is proposed. A combined Under Floor Air Distribution (UFAD) and a new Personalized Ventilation (PV) systems with a front-back design has been adopted such that it satisfies thermal comfort for the passengers, as well as providing an air shield between the passengers in order to prevent the spread of airborne contaminants. Two configurations have been made for the economy class in a passenger airplane. Both had the same UFAD system, and PV system with air inlet located at the back of the ahead seat, but with different air inlet angles, normal to the seat back and inclined by 45°. It has been found out that the second configuration provides better control for contaminant spreading, as well as better thermal comfort, with predictive mean vote of 0.6, and predicted percentage dissatisfied of 17.6%.

Discussion on the Application of New Thermal Insulation Materials for Power Batteries of New Energy Vehicles Based on Computer Analysis

With the widespread use of battery insulation systems, there are many optimizations for the size of the battery space in the box, the arrangement and combination methods, but there are few optimizations for the design of the battery inlet and outlet. This paper analyzes the battery insulation materials, builds a power battery heat generation analysis model, and analyzes the battery air outlet angle flow analysis, the air inlet angle material comparison analysis, and the FLUENT software is used for numerical simulation analysis to obtain the overall smooth characteristics and partial Flow rate and temperature distribution range. Finally, through the analysis of the experimental results, it can be known that for batteries with the same structure, the use of battery insulation materials can effectively improve the battery performance and extend the service life.

The influence of air inlet angle in swirl diffusers of UFAD system on distribution and deposition of indoor particles

The objective of the present study was to investigate the effect of swirl angle on the distribution and deposition of contaminant particles in a chamber with swirl diffuser in an under-floor air distribution (UFAD) system. In the desired model, the analysis of flow field and particle distribution for swirling diffusers at four angles 30°, 45°, 60°, and 90° has been conducted by OpenFOAM® with Eulerian-Lagrangian approach. The results show that under uniform initial distribution condition for particles, the percentage of inhalable particulate matter in the breathing zone decreases faster for the rotation angles of 45° and 60°. In other words, at the inlet angle of 45° and 60° after 600 s, the percentage of 2.5 μm particles removed is 79.2 and 79.5, respectively. While the same percentage for the inlet angle of 30° and 90° is 67.5 and 75.8, respectively. For the considered particles, the inlet angle of 45° and 60° can cause to increase the number of exited particles in comparison with the inlet angle of 30° and 90. Also, when the particles enter the chamber from inlet air diffusers, the concentration of 1, 2.5, and 5 μm particles in the breathing zone decreases by increasing the inlet air angle. But, for the 10, and 25 μm particles, the concentration of particles in the breathing zone increases by increasing the rotation angle of inlet swirl diffusers. The percentages of 2.5 μm particles exiting the outlet are 27.8, 46.9, 53.7, and 58 for the inlet angle of 30°, 45°, 60°, and 90°, respectively.

Experimental analysis and ANN prediction on performances of finned oval-tube heat exchanger under different air inlet angles with limited experimental data

Abstract A high accuracy of experimental correlations on the heat transfer and flow friction is always expected to calculate the unknown cases according to the limited experimental data from a heat exchanger experiment. However, certain errors will occur during the data processing by the traditional methods to obtain the experimental correlations for the heat transfer and friction. A dimensionless experimental correlation equation including angles is proposed to make the correlation have a wide range of applicability. Then, the artificial neural networks (ANNs) are used to predict the heat transfer and flow friction performances of a finned oval-tube heat exchanger under four different air inlet angles with limited experimental data. The comparison results of ANN prediction with experimental correlations show that the errors from the ANN prediction are smaller than those from the classical correlations. The data of the four air inlet angles fitted separately have higher precisions than those fitted together. It is demonstrated that the ANN approach is more useful than experimental correlations to predict the heat transfer and flow resistance characteristics for unknown cases of heat exchangers. The results can provide theoretical support for the application of the ANN used in the finned oval-tube heat exchanger performance prediction.

Air inlet angle influence on the air-side heat transfer and flow friction characteristics of a finned oval tube heat exchanger

In this study, the influence of various air inlet angles on the heat transfer and flow friction characteristics of a 2-row plain finned oval tube heat exchanger is analyzed by experimental and numerical methods. The experimental results show that an air inlet angle 45° provides the best heat transfer performance, and an air inlet angle 90° provides the smallest pressure drop, while an air inlet angle 30° provides the worst heat transfer performance associated with the largest pressure drop. The 3-D numerical simulation results indicate that with the decrease of the air inlet angle, the uniformity of the air velocity distribution in the z-direction of the heat exchanger becomes worse. The heat transfer characteristics at different air inlet angles are analyzed from the prospective of the field synergy principle and the effect of the air velocity distribution uniformity. The overall heat transfer performance is also evaluated by the JF factor under the same air mass flow rate. The results show that the air inlet angle 45° offers the best overall heat transfer performance, next is the air inlet angle 60°, while the air inlet angle 30° has the worst overall heat transfer performance.

Numerical simulation of airflow in animal occupied zones in a dairy cattle building

Air flow assessment in animal husbandry is an important issue in the context of welfare and emission. The aim of this study was to implement a porous medium approach for the numerical simulation of air flow in the animal occupied zone (AOZ) of a dairy building. Computational fluid dynamics (CFD) was used to determine the flow resistance properties, where cow geometry was simplified by a six-cylinder geometry. Three different AOZ were identified and parametric studies were performed to determine the pressure drop depending on the air inlet angle. Viscous and inertial loss terms were calculated by non-linear regression and added to the Navier-Stokes equations for each AOZ as a subdomain. Simulations of the air flow in a barn segment containing the three AOZ (standing, resting and resting in double line) indicated that in most configurations, inertial forces dominated and pressure drop was dependent on the air inlet angle. The viscous and inertial loss terms changed depending on the AOZ. The total pressure drop predicted using the porous medium approach taking into account the different AOZs was in good agreement with the results obtained by simulations using the fully resolved, simplified cow bodies.

Effect of tangential swirl air inlet angle on the combustion efficiency of a hybrid powder-solid ramjet

A new ramjet configuration using powder and solid fuel as propellant is investigated, namely, hybrid powder-solid ramjet (HPSR). Boron particles were used as the powder in this study. In order to improve combustion efficiency of boron and simplify the engine structure, a tangential swirl air inlet is adopted on the HPSR. Ignition model based on the multi-layer oxide structure and Global reaction combustion model of boron particles, the Lagrangian particle trajectory model and the realizable k-ε turbulence model were implemented to calculate three-dimensional two-phase flow and combustion in the HPSR with the different tangential air inlet angles (0°,5°, 10°, 15°, 20°, 25°). The effects of tangential air inlet angles on the ignition and combustion of boron were analyzed. The results show that when the tangential swirl air inlet angle is 10°, the combustion efficiency of boron particles and the total combustion efficiency of engine are the highest; the temperature distribution in the second combustion chamber is uniform, and the ignition distance of particles is small, for the HPSR configuration tested.

The Structure Optimization of Lithium-ion Battery Pack Based on Fluid-solid Conjugate Thermodynamic Analysis

To effectively improve the discharging efficiency and the cycle period, the thermodynamic analysis and the heat dissipation structure optimization are conducted on the lithium-iron battery pack. The internal resistance characteristics of the battery are experimented, and the change of internal resistance at different discharge rate and ambient temperature is measured. The three-dimensional thermal effect model of the battery is established, and the simulation analysis of thermoelectric coupling is carried out by using MSMD model in FLUENT. The simulation results are compared with the experimental results to verify the validity of the model. By the Ansys Workbench software, the three dimensional model are established based on the conjugate thermal transfer phenomenon. Based on the fluid-solid conjugate heat transfer mechanism, the influence of the airflow channel spacing and air inlet angle on the temperature distribution of the battery pack is analyzed, thus optimizing the heat dissipation structure. By studying the effect of the air flow rate and its temperature on the temperature distribution of the battery pack, the optimized heat dissipation structure can achieve the best performance.

Structural optimization of lithium-ion battery pack with forced air cooling system

The forced air cooling system is of great significance in the battery thermal management system because of its simple structure and low cost. The influences of three factors (the air-inlet angle, the air-outlet angle and the width of the air flow channel between battery cells) on the heat dissipation of a Lithium-ion battery pack are researched by experiments and computational fluid dynamics (CFD) simulations. Then the three structure parameters are optimized by using single factor analysis and orthogonal test method. It is shown that the layout of the air flow channels has great impacts on the maximum temperature and the temperature difference. The best cooling performance is obtained under the condition of 2.5° air-inlet angle, 2.5° air-outlet angle and equal channels width. With the optimization method, the maximum temperature and the temperature difference are decreased by 12.82% and 29.72% respectively. Therefore, the presented approach in this paper is able to optimize the battery thermal management system for electric vehicles.

Prediction of Transition and Losses in Compressor Cascades Using Large-Eddy Simulation

In the 1950s, NACA conducted a series of low-speed cascade experiments investigating the performance of NACA 65-series compressor cascades with tests covering multiple airfoils of varying camber and with variations in solidity and air inlet angle. Most of the configurations show transition via laminar separation—both on suction and pressure side—characterized by a relatively flat region in pressure distribution, while turbulent reattachment is characterized by a rapid pressure recovery just downstream of the separated region. In the current study, wall-resolved large-eddy simulation (LES) has been used to predict transition via laminar separation in such compressor configurations as well as the resulting airfoil losses. Six different cascades with local diffusion factor varying from 0.14 to 0.56 (NACA 65-010, 65-410, 65-(12)10, 65-(15)10, 65-(18)10, and 65-(21)10 cascades) were analyzed at design conditions. In addition, the loss bucket for various angles of attack off-design conditions has been computed for the NACA 65-(18)10 cascade. Chord-based Reynolds number for all the experiments considered here was held at 250,000. This allows sufficient grid resolution in these LES analyses at an acceptable computational cost, i.e., up to 20,000 CPU hours per case. Detailed comparisons to test data are presented in the form of surface pressure coefficient, drag coefficient, losses, and momentum thickness ratio. The results show that LES is capable of capturing transition via laminar separation relatively well for most of the cases, and consequently, may constitute a predictive tool for assessing losses of different compressor airfoils.

Numerical study of the air inlet angle influence on the air–side performance of plate-fin heat exchangers

Numerical work is performed to study the effect of air inlet angle on heat transfer coefficient and pressure drop of the plate-fin heat exchangers. Two special air inlet angles which are in the horizontal plane and in the longitudinal plane are simulated on 7 fin channel meshes with different fin parameters. The numerical results show that the different flow fields of the two special air inlet angles cause different effects on heat transfer coefficient and pressure drop. When the air inlet angle is in the horizontal plane, the air inlet angle effect is strongly related with the entrance region flow flied. When the air inlet angle is in the longitudinal plane, the air inlet angle effect is related with the whole fin channel flow field because the vortex size is much larger and comparable to the fin length. The effects of the two angles have different variation laws, which are greatly influenced by fin parameters. Finally, a prediction model is established to calculate the heat transfer coefficient and pressure drop of an arbitrary inlet angle. The comparison of prediction results and simulation results for 5 air inlet angles shows good agreement. The maximum prediction error is within 10%.

ANALYSIS OF FORCED DRAFT COOLING TOWER PERFORMANCE USING ANSYS FLUENT SOFTWARE

In this project the cooling tower performance has been analyzed by varying air inlet parameters with different air inlet angles and by attaching a nozzle in air inlet. The cooling tower analyzed here is used specifically for small scale industries, which is forced draft counter-flow cooling tower with single module capacities from 10 to 100 cooling tons. In this project 50 tons cooling capacity model has been taken as reference model. The analysis has been done using computational fluid dynamics (CFD) ANSYS 14.5 software. The cooling tower models have been modeled using SOLIDWORKS 2013 software and they have been meshed using ICEM CFD 14.5 software. The meshed models have been analyzed using FLUENT software. The air inlet angles varied in horizontal direction, vertical direction and by combining both horizontal and vertical inclination. A convergent nozzle has been modeled and assembled to the inlet pipe. The temperature contours of the cooling tower models have been taken from the analysis. Based on the outlet cold water temperature, the improved effectiveness of the cooling tower model has been obtained.

An experimental investigation on air-side performances of finned tube heat exchangers for indirect air-cooling tower

A tremendous quantity of water can be saved if the air cooling system is used, comparing with the ordinary water-cooling technology. In this study, two kinds of finned tube heat exchangers in an indirect air-cooling tower are experimentally studied, which are a plain finned oval-tube heat exchanger and a wavy-finned flat-tube heat exchanger in a cross flow of air. Four different air inlet angles (90?, 60 ?, 45?, and 30?) are tested separately to obtain the heat transfer and resistance performance. Then the air-side experimental correlations of the Nusselt number and friction factor are acquired. The comprehensive heat transfer performances for two finned tube heat exchangers under four air inlet angles are compared. For the plain finned oval-tube heat exchanger, the vertical angle (90?) has the worst performance while 45? and 30? has the best performance at small ReDc and at large ReDc, respectively. For the wavy-finned flat-tube heat exchanger, the worst performance occurred at 60?, while the best performance occurred at 45? and 90? at small ReDc and at large ReDc, respectively. From the comparative results, it can be found that the air inlet angle has completely different effects on the comprehensive heat transfer performance for the heat exchangers with different structures.