Airflow Inside Research Articles

Comparative Study of Sensory and Physicochemical Characteristics of Green-Tea-Fortified Cupcakes upon Air Frying and Oven Baking.

The air fryer and the oven are common cooking methods in our daily lives. However, previous investigations of the air fryer were limited to its comparison with deep-fat frying. This study compared the differences between air frying and household oven baking (without a fan or other forced airflow inside) on food quality and physicochemical properties using a cupcake model. Results showed that the oven-baked cupcakes were softer in texture (87.15%), greener in color (6.07%), and lower in weight loss (7.78%) and toxic advanced glycation end products (AGEs, 21.40%) when the heating temperature and duration were the same as oven baking. To improve the sensory characteristics and health value, the cupcakes were fortified with green tea. The differences in texture, color, and level of toxicants between the two cooking methods were diminished after the addition of green tea. Moreover, the chemical profiles of green tea catechins in the green-tea-fortified cupcakes remained similar upon thermal cooking, except that the air-fried cupcakes were lower in gallic acid (GA) but higher in (-)-gallocatechin (GC). Collectively, based on the differences in heating mechanisms, our data indicated that oven baking is a better cooking method suitable to prepare cupcakes than air frying from the perspectives of sensory characteristics and food safety, while green tea additives effectively counter the drawbacks of the air fryer.

A modelling method for large-scale open spaces orientated toward coordinated control of multiple air-terminal units.

The temperature distribution is always assumed to be homogeneous in a traditional single-input-single-output (SISO) air conditioning control strategy. However, the airflow inside is more complicated and unpredictable. This study proposes a zonal temperature control strategy with a thermal coupling effect integrated for air-conditioned large-scale open spaces. The target space was split into several subzones based on the minimum controllable air terminal units in the proposed method, and each zone can be controlled to its own set-point while considering the thermal coupling effect from its adjacent zones. A numerical method resorting to computational fluid dynamics was presented to obtain the heat transfer coefficients (HTCs) under different air supply scenarios. The relationship between heat transfer coefficient and zonal temperature difference was linearized. Thus, currently available zonal models in popular software can be used to simulate the dynamic response of temperatures in large-scale indoor open spaces. Case studies showed that the introduction of HTCs across the adjacent zones was capable of enhancing the precision of temperature control of large-scale open spaces. It could satisfy the temperature requirements of different zones, improve thermal comfort and at least 11% of energy saving can be achieved by comparing with the conventional control strategy.Electronic Supplementary Material (ESM)the Appendix is available in the online version of this article at 10.1007/s12273-022-0942-8.

A hybrid domed roof and evaporative cooling system: thermal comfort and building energy evaluation

Domed roof and evaporative cooling channel as feasible passive cooling techniques have been investigated independently in numerous studies. In the present study, a novel system involving the two techniques simultaneously for meeting comfort conditions was proposed. To this end, 3D CFD simulations of airflow inside and around a 64-m2 test building with four domes were carried out. Subsequently, the thermal performance of the system was modeled with a computer code. Effects of both geometric and environmental parameters on the system performance were assessed. The obtained results indicated that the dome's diameter and the dimensions of the cooling channel affect the performance of the system significantly. Also, the proposed system in the present study could supply the required amount of air change per hour (ACH) when the wind velocity is between 0.8 to 3.2 m/s. Furthermore, considering ATCS (adaptive thermal comfort standard), the system provided thermal comfort under a maximum cooling demand of about 112 W/m2. Finally, the energy metric and environmental analyses were carried out to compare conventional cooling equipment with the introduced system and four different hybrid systems of domed/vaulted roofs proposed in the literature in terms of the energy consumption and the emission production.

Effect of heat exchanger base thickness and cooling fan on cooling performance of Air-To-Air thermoelectric refrigerator; experimental and numerical study

The available statistics reveal that a significant portion of the total electrical energy in different communities is used for various heating and cooling purposes and refrigeration in the domestic and industrial sectors, which includes cooling systems in critical areas such as the food and pharmaceutical industries. In this work, air-to-air thermoelectric cooling systems have been analyzed. Experimental and numerical attempts have been made to evaluate the influence of the base thickness size of external heat exchanger on cooling performance of refrigerator. In addition, the cooling system has been operated in different working conditions and the effect of cooling fan velocity on the Coefficient of Performance (COP) value was presented. It was found revealed that, the temperature of the cooling chamber for 4.5 mm thickness dropped to 11.57 °C, while this temperature was 9.93 °C for 1.5 mm thickness. Considering the final temperatures, there was a 14% difference by reducing the thickness from 4.5 mm to 1.5 mm for the case of Vair = 7.5 external fan speed. For the numerical approach, ANSYS Fluent 16.0 software was utilized to analyze the structure of airflow inside and outside of the refrigerator in detail. As a result of Computational Fluid Dynamics (CFD) simulation temperature distribution and air velocity contours have been obtained and achieved results were discussed.

Investigation of а stress-strained state of a screw-shape tubes of heat exchangers

Based on the results of the study of the parameters of the air flow inside of the brass screw-shape tube of the heat exchanger, the determination of their optimal geometric characteristics and further modeling of the stress-strain state was performed. Verification of simulation results is carried out on the basis of comparison with the test task.

К ТЕОРИИ ПРОСТРАНСТВЕННОЙ БРАХИСТОХРОНЫ

In this paper, a solution to the problem of the motion of a brachistochrone in the ndimensional Euclidean space is firstly presented. The very first formulation of the problem in a two-dimensional case was proposed by J. Bernoulli in 1696. It represented an analytical description of the trajectory for the fastest rolling down under gravitational force only. Thereafter, a number of problems devoted to a brachistochrone were considered with account for gravitational forces, dry and viscous drag forces, and a possible variation in the mass of a moving body. Analytical solution to the formulated problem is presented in details by an example of the body moving along a brachistochrone in three-dimensional Cartesian coordinates. The obtained parametric solution is confirmed by a graphical interpretation of the calculated result. The formulated problem is solved for an ideal case when drag forces are neglected. If dry and viscous friction forces are taken into account, the plane shape of the brachistochrone remains the same,while the analysis of the solution becomes more complicated. When, for example, a side air flow is taken into account, the plane curve is replaced by a three-dimensional brachistochrone.

ANALISA KEGAGALAN PLATEN TUBE SUPERHEATER PLTU TELUK SIRIH

Superheater is a main part of boiler that serves as one of steam temperature riser after water evaporated by heat inside a boiler. The steam comes out from boiler drum, by utilizing hot air flowinside boiler. Superheater tube is a very important part of process inside the plant, with a high operating temperature of 540°C (in PLTU Teluk Sirih). Because of this, the tube will be maintained by inspection on each scheduled shutdown. Leakages often occur in platen tube of superheater, exactly at its bend or elbow tube. To know causes of the leakages of the part, we conducted observation analysis i.e., visual observation (metallographic testing), spectrometry and hardness test. From the metallographic test analysis, pearlite and ferrite phases present. At the leakage part, it could be observed the tube has lost much of pearlite phase caused by heating. Pearlite micro structure indicates hardness of a material. In spectrometry test of the leaked tube sample using ASTM SA213 T22 standard, value of carbon rises very high by 0.148 from normal value, 0.15 at maximum. We also obtained from it average hardness of 178 HB (ASTM standard). From analysis of the superheater platen tube, damage caused by abrasion of bad materials hit the tube and decreasing pearlite phase caused by temperature changes. Tiny parts of the tube that hit by steam fell eroded and over time the tube broken. Another thing we can conclude is burst of fire in boiler may cause thinning and tube leakage.

Performance and economic analysis of natural convection based rubber smoking room for rubber cooperatives in Thailand

Abstract A modified rubber sheet smoking room was designed, constructed and tested, with uniform hot air flow inside in it, so that the temperature difference between any plane was less than 7 °C. This room can dry up to 1500 sheets in 72 h. Specific fuelwood consumption was 0.42 kg/kg of dried rubber. It consumed 67% less fuelwood and increased the fraction of good quality rubber sheets by 8.5% when compared to a conventional rubber smoking room. Thermal efficiency also increased from 6.9% to 15.7%. Moreover, the modified smoking room can save 1414 USD/year with payback period of 5.7 years. Therefore, the modified design can be recommended to rubber cooperatives for a better return.

Wind turbine designs for urban applications: A case study of shrouded diffuser casing for turbines

The increased demand for renewable energy and the development of energy independent building designs have motivated significant research into the improvement of wind power technologies that target urban environments. However, the implementation of wind turbines in urban environments is still very limited. There have been some studies analyzing different designs of urban wind turbines either using computational fluid dynamics (CFD), wind tunnel tests or field data for existing or new turbine designs. This paper reviews the state-of-the-art of urban wind energy by examining the various types of urban wind turbine designs, with a view to understand their performance and the synergy between the turbines and the urban environments. It also considers a flanged diffuser shroud mechanism - a fluid machine, mounted on rooftop of buildings used as casing for small wind turbines to improve turbine performance by using mainly CFD. The diffuser shroud mechanism can draw the airflow over buildings utilizing its special features such as, cycloidal curve geometry at the inlet and a vortex generating flange at the outlet, to guide and accelerate the airflow inside. The performance of the fluid machine is optimized parametrically. The mechanism is modeled on a building rooftop in a real test site in Montreal, Canada with real statistical wind data. The CFD result confirms the functionality of the fluid machine to take advantage of the airflow over buildings in complex built-environments for wind power generation.

Experimental study and numerical simulation of the interior flow in a telecommunications cabinet

The sector of information and communication technologies, especially telecommunications, has grown in a relentless way, leading to an increase in the number of necessary infrastructure to ensure the geographical coverage of the service, having the outdoor telecommunications cabinets (OTC) been an increasingly preferred choice of this type of infrastructure. These cabinets need cooling systems to maintain interior temperatures between desired values, but an effective cooling depends directly on the air flow inside. This paper includes the experimental results of the internal flow and heat transfer in a model a of real OTC, in order to characterize its thermal behavior. The internal air flow is visualized through experimental methods and compared with numerical predictions. The flow occurs mainly in turbulent regime, possessing greater magnitude on the back area of the OTC, where also exist some recirculation zones that can difficult an effective cooling. The results allow to conclude that forced ventilation is an effective method of OTC cooling, combined with low energy consumption.

Investigation of ventilation opening positions effect on the airflow inside and outside of a greenhouse

Investigation of ventilation opening positions effect on the airflow inside and outside of a greenhouse

Uniform Corrosion Behavior of AA7075 with Nanoclay

Ethanol in aircraft fuel has the ability to absorb the atmospheric air which enters the fuel tank and leads to corrosion. Currently, to avoid the airflow inside fuel tank, polysulphide sealants like Proseal are used to seal the fuel tank which helps in the prevention of corrosion. These sealants have disadvantages such as the process of curing will be slow which changes in consonance with the temperature and humidity and it requires a catalyst for the completion of the curing procedure. It is complex to handle and the life span is also very short. According to the various researches, it is proved that nano-composites have the proficiency to resist the corrosion and to improve the various mechanical properties such as strength, thermal stability, weight reduction, long life etc. In the present work, five specimens have been fabricated and tested. First specimen is an Aluminium alloy 7075 (AA 7075). The remaining four specimens are manufactured with AA 7075 as the matrix and nanoclay montmorillonite (MMT) K10 powder in the varying compositions (3%, 5%, 7%and 9%) as the reinforcement. The fabrication of the test pieces was done by stir casting method. Finally corrosion testing (ASTM – G31) was done by immersing the test specimen in hydrochloric acid by varying the time. Testing and comparison concludes that the composite materials have a better corrosion resistance property with an increase in the efficiency by 35% to 45%. In addition, the mechanical properties of the composite specimens also have increased by 7 % to 11 %. Thus it is concluded that nanoclay composites are best suited for the aircraft fuel tank construction.

Dynamic computer-aided approximation of airflow around and inside an agricultural structure

The present work studied, numerically, the airflow inside and outside an agricultural structure with openings. The governing Navier–Stokes and continuity equations were solved with finite element method. The numerical experiment was designed so that it simulates the airflow inside and outside of an agricultural structure model placed in a wind tunnel, like in the experiment used in this article for validation purposes. The length of the structure model occupied the entire width of the wind tunnel. The flow was incompressible, unsteady, and nominated to be two-dimensional. The Reynolds number studied in this work was Re = 2800 with respect to the structure height. The numerical results such as instantaneous streamlines, velocity values, and turbulent parameters are presented for the internal and external environment of the structure. The predicted time-mean averaged stream lines and turbulent kinetic energy values are compared with available experimental data in the literature. From the presentation and the statistical analysis of instantaneous velocities, intense fluctuations were observed in the flow configuration over time.

Two-phase SPH simulation of fluid–structure interactions

In this paper, a two-phase Smoothed Particle Hydrodynamics (SPH) method is used to simulate the fluid–structure interactions with violent deformation of the free surface. An improved solid boundary treatment is proposed based on the accurate pressure interpolations of the inner fluid particles. The model performance is validated by sloshing in a water tank and dam break flow impact on a vertical wall. In the practical model applications, a two-dimensional wedge entry into the static water is studied, for which the flow fields of water and air phases are computed simultaneously. It has been found that both the water flow around the wedge cavity and the air flow inside are reasonably predicted. Also the two-phase model has been found to accurately provide the flow features throughout the entire entry process, while the single-phase model can only predict the flows before the closure of the cavity due to the lack of air modeling. Besides, a laboratory experiment on the wedge entry has also been carried out for the validation purposes.

Assessment of porous media instead of slatted floor for modelling the airflow and ammonia emission in the pit headspace

In order to reduce the emission, proper understanding of the transportation behaviour of gaseous ammonia inside the slurry pit is required. Numerical simulation by the aid of computational fluid dynamics (CFD) technique can be used for this purpose. However, direct modelling of slatted floors is complicated and may be replaced by the porous media model (PMM) as shown in earlier studies. The objective of our study is to improve the quality of simulation results by PMM, and to assess the effects of air velocity above the slatted floor (as affected by wind), pit headspace height (as affected by amount of slurry in the pit) and sidewall height (as affected by the dairy house sidewall) on the airflow features inside the pit and ammonia emission from the pit. Three different CFD models of a slatted floor were developed to evaluate whether porous media is capable to represent a slatted floor for modelling the airflow inside and ammonia emission from the slurry pit, and to study the effect of turbulence treatment in the porous media on the modelling results: a slatted floor model (SFM) which models the slatted floor as it is, a turbulent porous media model (PMM-T) and a laminar porous media model (PMM-L). Both PMM-T and PMM-L represent the slatted floor by porous media, the PMM-T assumes turbulent airflow and the PMM-L assumes laminar airflow in the porous media. The SFM was verified for a dataset acquired from a 1:8 scale wind tunnel model of the slurry pit. Results showed that the PMM (PMM-T and PMM-L) were able to predict both the airflow features inside the slurry pit and the ammonia emission from the slurry pit if the resistance parameters and flow regime of the porous media were properly set. In comparison to the SFM, the PMM-T predicted the flow pattern better, but overestimated the turbulence intensity and the consequent emission rate. PMM-L performed better in predicting the ammonia emission rate because of the relatively accurate prediction of turbulence intensity. Simulation results also showed that the ammonia emission rate increased with a higher mean airflow velocity, a smaller headspace height and the presence of sidewalls.

Optimisation of the design parameters of a domestic refrigerator using CFD and artificial neural networks

This paper reports the use of computational fluid dynamics (CFD) and artificial neural networks (ANN) for optimising and improving the performance of a static type domestic refrigerator. The effects of the hydrodynamic and thermal fields on the air flow inside of the refrigerator compartment were considered by exact modelling of the fan. The interior volume of air of the refrigerator was modelled using a CFD method, and analyses were performed. The numerical results were validated by comparing experimental results with the calculated interior design parameters. An optimisation study of the obtained design parameters was performed using a parametric method. The optimum design case was predicted by the ANN. The performance of the refrigerator improved by approximately 7.7% based on the amount of heat taken from the evaporator surface assuming thermal uniformity of the interior volume of air and the ISO 15502 standards. As a result, the annual energy consumption will decrease by 17.52 kWh.

A Verification and Validation Study of CFD Simulation of Wind-Induced Ventilation on Building with Single-Sided Opening

Wind-induced ventilation is widely acknowledged as one of the best approaches for inducing natural ventilation. Computational fluid dynamics (CFD) technique is gaining popularity among researchers as an alternative for experimental methods to investigate the behavior of wind-driven ventilation in building. In this present paper, Reynolds averaged Navier-Stokes equation (RANS) k-ε model approach is considered to simulate the airflow on a simplified cubic building with an opening on a single façade. Preliminary simulation using models from previous experiment indicates the reliability of OpenFOAM, the open source software that will be used in this study. The results obtained in this study will better define options for our future study which aims to explore how different buildings arrays modify the airflow inside and around a naturally ventilated building.

Electrospun Polyacrylonitrile nanofiber yarn prepared by funnel-shape collector

The homemade electrospinning set-up was used to prepare Polyacrylonitrile nanofiber yarn. Compared with the traditional electrospinning set-up, the special difference in this method was that the funnel-shape collector with high-speed airflow inside was employed. The yarn forming process was investigated and the effect of spinneret-to-collector distance and LiCl (lithium chloride) additives on the yarn forming process was discussed. The results showed that the nanofiber yarn was fabricated successfully by using our electrospun set-up. The spinneret-to-collector distance 3cm was most appropriate for fabricating electrospun nanofiber yarn. When 0.6wt.% LiCl was added in polymer solution, fiber convergence was observed obviously and the fiber arranged along the yarn longitudinal direction.

D214 二次元燃焼流の密度境界におけるバロクリニックトルクおよび浮力渦度の生成機構(OS-12:次世代の燃焼技術(V)・一般講演)

The focus of this research is placed on spatio-temporal evolution of vorticity produced by baroclinic torque and buoyancy in a density boundary layer between burnt gas of two-dimensional premixed laminar flame and side air flow. PIV and discrete vortex simulation of Lagrangian transport element method are carried out. As a result, it is found that accumulated vorticity due to buoyancy in a density boundary layer leads to roll-up of large-scale vortical structure in downstream region. Then, it induces acceleration of a density boundary region through kinetic pressure, resulting in secondary generation of baroclinic torque.

Investigation of liquid droplets drift affected by side airflow

Investigation of liquid droplets drift affected by side airflow