Input Air Velocity Research Articles

Improving building energy efficiency through ventilated hollow core slab systems

The increasing desire for comfort and healthy indoor environment, as well as improvements in energy standards in recent years, have stressed the need to make an active use of the building mass to achieve the maximum energy saving This is why the application of ventilated hollow-core slab systems (VHCS) can be considered as one of the innovative approaches. These systems have precast concrete slabs with tubular voids directing ventilation air on its length. In the present study Solving this system numerically using the ANSYS fluent program to study the temperature distribution and air flow in the 3-D test model of the present study to determine the feasibility of applying this system in an arid climate especially in Iraq by checking the inlet velocity and temperature and to predict the impact of these operating parameters on human comfort and energy savings. The study aimed to provide a numerical analysis of a conditioned zone's temperature distribution using VHCS. The investigation was carried out on a scale model room of size (1 m × 1.2 m × 1 m) with a scale factor of ¼. Four distinct scenarios were examined: the first two cases occurred during a no-load time in the night when there were no internal or external loads and examined the effects of changes in inlet temperatures and air velocities. The remaining two scenarios were conducted during an occupied period with internal heat gain of 630 W/m2 and external heat gain of 800 W/m2 based on the SHGC for the summer season of Iraq. As previously demonstrated, setting the inlet velocity to 1 m/s resulted in an optimal temperature and velocity distribution in the main flow, irrespective of changes in the external and internal loads and temperatures of the supply core. The findings shown that input air velocity and temperature affect heat remove efficiency. In addition, numerical outcomes have also illustrated that the Thermal Active VHCS System, while used in combination with ventilation strategies, could indeed regulate the space conditions by cooling down the building's ceiling, thus eradicating stored heat. All investigations found VHCS systems suitable for air conditioning in dry and hot locations. The systems are known for their ease of use, simplicity, high performance, comfort, and energy savings. They can also reduce peak loads to boost structural energy efficiency.

Heat Convection in a Channel-Opened Cavity with Two Heated Sources and Baffle

This study employs COMSOL software v 5.6 to investigate a novel approach to heat transfer via mixed convection in an open hollow structure with an unheated 90° baffle elbow. Two 20 W heat sources are strategically positioned on the cavity’s bottom and right-angled wall for this research. Notably, the orientation of the baffle perpendicular to the airflow is used to direct external, unrestricted flow into the square cavity. The research investigates a range of air velocities (0.1, 0.5, 1.0, and 1.5 m/s) and the intricate interaction between input air velocity, dual heated sources, and the presence of a right-angle baffle on critical thermodynamic variables, such as temperature distribution, isotherms, pressure variation, velocity profile, air density, and both local and mean Nusselt numbers. Validation of the applicable computational method is achieved by comparing it to two previous studies. Significant findings from numerical simulations indicate that the highest velocity profile is in the centre of the channel (2.3–2.68 m/s at an inflow velocity of 1.5 m/s), while the lowest profile is observed along the channel wall, with a notable disruption near the inlet caused by increased shear forces. The cavity neck temperature ranges from 380 to 640 K, with inflow air velocities varying from 0.1 to 1.5 m/s (Re is 812 to 12,182), respectively. In addition, the pressure fluctuates at the channel-cavity junction, decreasing steadily along the channel length and reaching a maximum at the intake, where the cavity neck pressure varies from 0.01 to 2.5 Pa with inflow air velocities changing from 0.1 to 1.5 m/s, respectively. The mean Nusselt number exhibits an upward trend as air velocity upon entry increases. The mean Nusselt number reaches up to 1500 when the entry air velocity reaches 1.5 m/s. Due to recirculation patterns, the presence of the 90° unheated baffle produces a remarkable cooling effect. The study establishes a direct correlation between input air velocity and internal temperature distribution, indicating that as air velocity increases, heat dissipation improves. This research advances our understanding of convective heat transfer phenomena in complex geometries and provides insights for optimising thermal management strategies for a variety of engineering applications.

Parametric optimization and experimental verification of multi-fertilizer mixing by air blowing and blade stirring based on discrete element simulations

In proportional variable-rate fertilization, improving the uniformity of multi-fertilizer mixing helps to improve the overall utilization efficiency of fertilizers. In this paper, a multi-fertilizer mixing by air blowing and blade stirring was presented. Using fertilizer granules mixing uniformity as an indicator, the method optimized the structures and working parameters of single-blade group stirring, double-blade group stirring and air blowing & double-blade stirring. EDEM and Fluent software were used for the simulation and the results were verified by experiments. The simulation results showed that the appropriate speed range of single-blade group stirring was 600 ∼ 900 r⋅min−1 and the highest mixing uniformity was achieved with the blade mounting angle α of 20°. The best structure of double-blade group stirring was achieved with an upper blade mounting angle β of 20°, a lower blade mounting angle θ of −20° and a spacing h of 89 mm. For the air blowing & double-blade stirring method, the best results were achieved when the input air velocity va was 8.4 m⋅s−1 and the blade speed of agitator nb was 740 r⋅min−1. The mixing uniformity of nitrogen (N), phosphate (P) and potash (K) fertilizer granules reached 98.41%, 98.12% and 98.31%, respectively. The bench test results showed that the mixing uniformity by air blowing & double-blade stirring was better than that by double-blade group, and the mixing uniformity by double-blade group was better than that by single-bladed group, which were consistent with the simulation results. Meanwhile the differences between experimental values and simulation values were within 2%, which showed that the simulation models were reliable. Results from this study can be used as reference for the design of mixing devices of variable-rate fertilization.

Particle flow characteristics in the pipeline of a nonmetallic ore powder air classifier using a DPD-DEM coupled method

Understanding particle flow characteristics can help improve the efficiency of nonmetallic ore powder air classifiers. In this paper, dissipative particle dynamics (DPD) and the discrete element method (DEM) were adopted to study the interactions between the gas phase and solid particles. Gas and solid phases were coupled using the single-particle DPD model. Taking sepiolite particles as an example, at the optimal input air velocity in the pipeline, the gas particle velocity distribution, solid particle velocity distribution, solid particle concentration distribution, and solid particle position distribution were analyzed by numerical simulations. A comparison of numerical simulation and experimental results showed that when the input air velocity in the pipeline was 17 m/s, the velocity of particles and gas in the pipeline gradually increased from the wall to the center of the pipeline. The velocity near the pipeline wall changed rapidly, and the velocity in the main flow area remained basically unchanged. Particles left the pipeline in a uniform and dispersed state and were carried into the classification area. As the input air velocity increased, the pressure drop across the pipeline also increased. Therefore, the optimal input air velocity value could be reasonably selected to minimize energy consumption.

Ansys fluent; CFD; PCRD; simulation; sago starch

The mini-scale pneumatic conveying ring dryer (PCRD) type sago starch dryer with a capacity of 80 kg / day has been applied to the processing of sago starch to produce dry sago starch. To increase the production capacity of the PCRD dryer, a recirculation pipe was modified. The modified pipe section is the venturi pipe diameter and the upriser vertical pipe increased. The diameter of the vertical upriser pipe is 2.5 times larger than that of the ubend pipe and the downcomer vertical pipe so that a buffer is formed. In addition, the difference in the diameter of the recirculation pipe can increase the residence time of the material. The purpose of this study was to simulate using ansys fluent to determine the temperature profile, air flow velocity, and pressure in the pneumatic conveying ring dryer (PCRD) type sago starch dryer pipe with a capacity of 1 ton per day. Simulations were carried out using the Computational Fluid Dynamics (CFD) technique using ansys fluent software package. The simulation results show that the temperature along the pipe has decreased by about 2oC at various variations of the input air velocity and variations in the outlet at the boundary conditions. Likewise, the air velocity at the end of the outlet pipe (vertical downcomer pipe) increases due to the difference in diameter with the inlet pipe. The pressure on the vertical upriser pipe is higher than the pressure on the ubend pipe and downcomer vertical pipe. The simulation results show that the recirculation pipe design is very well used so that it can be continued for the manufacture of PCRD-type sago starch dryer on a scale of 1 ton per day.

The effect of air velocity on the performance of the direct evaporative cooling system

This experimental study aimed to determine the effect of airflow velocity on the performance of a direct evaporative cooling system. Rectangular-shaped honeycomb cooling pads with a length of 34 cm, a width of 25 cm, and a thickness of 3.5 cm are used as cooling media. The main parameters of the study are low air velocity (2.3 ms−1), medium (3.2 ms−1), and high velocity (3.7 ms−1). The data collected include dry bulb temperature, wet bulb temperature, output air temperature, input and output air velocity, input and output humidity, and solar radiation. These data are used to determine saturation efficiency, cooling capacity, temperature decreases, and feasibility index. The experimental results are presented in the form of tables and graphs and analysed based on existing theories. The results showed that the evaporative cooling system could produce output temperatures up to 27.5°C with input 31.4°C at low airspeed, 27.97°C with input 31.47oC at medium speed, and 27.7°C with input 31.30°C at high air speed. It was concluded that a low airflow rate would add to the cooling efficiency, and the higher the airflow rate, the lower the cooling efficiency. The results showed that evaporative cooling is achievable with a feasibility index of 19.89 ≤ F*≤ 20.67. The results also affirmed that cooling capability is higher where the feasibility indexes are comparatively low.

Investigation of Check Valve Aerodynamic Characteristics in Different Operating Modes

The paper presents a computational study of the NPP ventilation system check valve aerodynamics, namely, a numerical simulation of the air flowing through the open valve with the subsequent determination of the relationship between the reactive torque acting on the valve closure axles and the input air velocity.This numerical simulation of the air flowing through the check valve was performed using the ANSYS CFX program. In the computation, different operating modes of the check valve were considered when the air flow was passing through it. The valve operating modes were set depending on changes in the input air velocity. As a result of aerodynamic computation, the values of pressure and velocity components were obtained over the entire valve volume.Reactive forces were calculated in the ANSYS Mechanical program. The reactive forces acting on the valve body form a torque at the gate axles. When adjusting the check valve to the actual flow rate, it is necessary to know this torque value and compensate for it. As a result of a series of computations of reactive forces, a relationship was found between the torque value of the valve’s working element axles and the input air velocity.

전산유체역학을 이용한 목재펠릿보일러 연소모델 정립 및 검증

In this study, combustion behaviour were to analyze by comparing experimental data against predicted values. In developing pellet boiler performance, various factors such as combustion chamber shape, input air velocity, the amount of fuel, temperature, and fuel characteristics need to be analyzed. Analytical model using a numerical method is useful to overcome time and cost consuming by practical experiment. By controlling feeding rate of fuel, flue gas composition and temperature distribution obtained form experiment were compared with predicted values using FLUENT(ANSYS, Inc., Southpointe). Measurement were in good agreement with model predictions : with 0.60 % for CO 2 0.73% for O 2 when compared with independent data sets.

Meramal Aliran Udara dan Keselesaan di dalam Masjid Sultan Salahuddin Abdul Aziz Shah Menggunakan Simulasi Komputer

A study on ventilation system using a two dimensional turbulence k-e model with the assumption that the fluid is incompressible and non-isothermal is presented. The purpose of this study is to predict the distribution of air velocity and temperature in main hall Masjid Sultan Salahuddin Abdul Aziz Shah in Shah Alam. When the airflow and temperature distribution have been predicted by the computer software FLUENT, the comfort level can easily be determined. Nine cases have been conducted to examine the effects of input air velocity, air velocity from the fan heli and fan air flow direction to the percentage of consumer dissatisfaction. Mixing characteristics of comfort have been analyzed under different air supply velocities, temperatures and fan velocities. The fan velocity directions involved two conditions which are the upwards and downwards directions. The results from the research in the form of air velocity and temperature distributions are important in determining the comfort level which is unsuitable for the user. It was found that cases of 3,4, 5, 6 and 7 show the effect of a very good comfort with the percentage of PPD between 10% to 20%. The location of heli fans also affects the impression of comfort in the main hall. The comfort level of this area can be improved by modifying the position and increasing the number of fans in the hall.

Performance Analysis of Contact Baking of Flat Bread in an Indirect-Heating Oven

A significant portion of Iranian flat breads are produced in semi-industrial, indirect-heating ovens. Therefore, an efficient oven design and a proper selection of operating conditions are crucial to improve the product quality and reduce energy consumption. In the present study, a mathematical model is developed to simulate a semi-industrial, indirect-heating, continuous oven performance during contact baking of an Iranian flat bread, referred to as Taftoon. Individual modes of heat transfer are considered among various components of the baking system to estimate the system performance and the bread quality in terms of design and operating conditions. The predictions of this model are in good agreement with the experimental data. Numerical results indicate that conduction is the primary heat transfer mechanism. Furthermore, the effects of dough thickness, conveyer speed, and input air velocity on the quality of the bread are studied and appropriate ranges for the parameters are determined.

有机发光二极管的热分析与热设计

Computational fluid dynamic(CFD) based thermal simulation and transient thermal measurement are utilized to evaluate the thermal performance of OLED in this paper.The effects of input power,panel orientation and air velocity on the thermal characteristics of OLED are investigated and discussed.It is found that obvious thermal gradient exists between junction and substrate or glass cover,and the thermal gradient increases obviously with the input power.The thermal characteristic has a close relationship with the orientation of OLED panel and air velocity.

Cinética de produção de levedura seca em leito de jorro

Estudou-se neste trabalho, a cinética de produção durante a secagem em um secador de leito de jorro convencional com inertes, trabalhando-se com alimentação intermitente de levedura, com umidade inicial de 70% em base úmida. Fez-se um planejamento fatorial 22 mais configuração estrela com 3 experimentos no ponto central, totalizando 11 experimentos, objetivando-se o estudo da influência da concentração de levedura e velocidade do ar na entrada sobre a cinética de produção de levedura seca. A cinética se mostrou crescente e praticamente linear em todos os experimentos. Esta análise permitiu a identificação das condições ideais de operação do secador com relação à velocidade de operação e de quantidade de levedura a ser alimentada para obtenção de um produto de qualidade para utilização como complemento protéico na alimentação de animais.

Influence of Head Geometry on the Distributive Performance of Air-assisted Seed Drills

Systematic design of distributor heads for air-assisted drills has not been fully developed because of its inherent complexities. Apart from the aerodynamics of the distributor, the mechanics of seed flow in air is governed by quite a number of factors, such as the properties of the seeds, the quantity of seeds in the distributor at any instant of time, input air velocity and many other such parameters. In the absence of theoretical procedures for designing the distributor head, three heads with different aerodynamic configurations, namely parallel disc, closed funnel and streamlined flow were made and evaluated on a test rig exclusively developed for varying the seed feed rate and input air velocity. The distributive performance was studied for three types of seed namely sesame, pearl millet and sorghum. While distributing sesame, the velocity at the distributor outlet for a given input air velocity and seed rate, was 6–8% lower with the closed-funnel distributor than with the other types. Here, the lower air velocity was a manifestation of the clogging and turbulence as caused by its aerodynamic configuration. The clogging caused a lack of uniformity in the distributed air velocities between the outlet tubes, which ultimately lowered the uniformity of seed distribution. The ability of the distributor to output equal quantity of seeds to individual outlet tubes, termed as uniformity of distribution was correspondingly poor (33–40%) at input air velocities less than 4·5 m/s and seed feed rate less than 68 g/min with the closed-funnel distributor. Similarly, in the case of pearl millet and sorghum also, the closed-funnel distributor offered lower uniformity of seed distribution. The uniformity greatly depended on the seed feed rate rather than the input air velocities for pearl millet. On analysing the performances of the distributors, the head offering a streamlined flow was found to yield the best distributive performance for all the three types of seed. It offered 98·6% uniformity at 5·5 m/s input air velocity and 79 g/min seed feed rate for sesame. The uniformity obtained for pearl millet was 98·5% at 6·0 m/s input air velocity and 168 g/min seed feed rate and was 99·4% for sorghum at 8·0 m/s and 238 g/min. Hence, while developing a distributor for an air-assisted drill, procedures such as the finite element method can be adopted to iteratively model the head's shape towards streamlining the flow and thereby to improve the distribution efficiency.