Effect of Drying Air Velocity on Drying Kinetics of Tomato Slices in a Forced-Convective Solar Tunnel Dryer

The objective of this work is to analyse the extent to which a change in the drying air velocity may affect the drying kinetics of tomato in a forced-convective solar tunnel dryer. 2 m?s?1 (V1) and 3 m?s?1 (V2) air speeds were applied in similar drying air temperature and humidity conditions. Main drying constants calculated included the drying rate, the drying time and the effective water diffusivity based on the derivative form of the Fick’s second law of diffusion. Henderson and Pabis Model and Page Model were used to describe the drying kinetics of tomato. We found that solar drying of tomato occurred in both constant and falling-rate phases. The Page Model appeared to give a better description of tomato drying in a forced-convective solar tunnel dryer. At t = 800 min, the drying rate was approximately 0.0023 kg of water/kg dry matter when drying air velocity was at 2 m/s. At the same moment, the drying rate was higher than 0.0032 kg of water/kg dry matter when the drying air velocity was 3 m/s. As per the effective water diffusivity, its values changed from 2.918E?09 m2?s?1 to 3.921E?09 m2?s?1 when drying air velocity was at 2 and 3 m?s?1 respectively, which is equivalent to a 25% increase. The experimentations were conducted in Niamey, on the 1st and 5th of January 2019 for V2 and V1 respectively. For both two experiments, the starting time was 9:30 local time.

Design and Characterization of an Aerosol Test Chamber for Emergency Response Patient Contamination Control Simulation and Research

Contaminated or infected patients present a risk of cross-contamination for emergency responders, attending medical personnel and medical facilities as they enter a treatment facility. The controlled conditions of an aerosol test chamber are required to examine factors of contamination, decontamination, and cross-contamination. This study presents the design, construction, and a method for characterizing an aerosol test chamber for a full-sized manikin on a standard North Atlantic Treaty Organization litter. The methodology combined air velocity measurements, aerosol particle counts and size distributions, and computational fluid dynamics modeling to describe the chamber’s performance in three dimensions. This detailed characterization facilitates future experimental design by predicting chamber performance for a variety of patient-focused research.

Retrofitting Sprinkler Systems for Suppressing Dust Generated by Moving Vehicles Inside Farms

Fugitive dust is one of the well known problems in agriculture and it affects both humans and machine producing quality. Dust problems can seriously cause harmful diseases to workers and ruin expensive equipments. In this study, a dust formation generated in open environment by vehicles was analyzed on unpaved roads. Formed dust was measured by calculating total forces on the PM10 （airborne particles smaller than 10 mm） of dust particles, such as air velocity, gravity forces and air turbulence generated by the moving vehicle. The water fogger nozzle discharge was measured to determine the approximate droplets quantity in the air. The foggers were used to suppress the generated dust in an open environment via installing a proposed automatic suppression system which opens automatically when vehicles pass under the system. The relationship between water droplet speed and ability of collecting fugitive dust showed that high air temperature above 40oC and wind speed above 10 m s-1 have negative effects on the system’s ability of collecting dust due to evaporation of small radius droplets and/or drifting water droplets away from the effective area. The overall system efficiency was found to be 85% and the proposed dust suppression system was found to be a satisfying solution for reducing fugitive dust hazards.

Thermal stability of nanostructured NiCrC coating prepared by HVAF spraying of cryomilled powders

Thermal stability of nanostructured NiCrC coating prepared by high velocity air-fuel （HVAF） spraying of cryomilled feedstock powders was investigated. Transmission electron microscopy （TEM）, differential scanning calorimetry （DSC）, and X-ray diffraction （XRD） were utilized for characteristic analysis. Recrystallization and normal grain growth occur when isothermal treatment is performed at 923 K （0.55 TM） for up to 100 h, and the average grain size increases from initial 41 nm for as-deposited state to around 100 nm for nearly equilibrium state. Isochronal treatment at 823 K and 1023 K was also conducted for comparison. Accordingly, for 0.49 to 0.61 T/TM, the time exponent n deduced from D^1/n - D0^1/n = kt increases from 0.15 to 0.30. The observed high thermal stability is attributed primarily to a Zener pinning mechanism arising from the fine Cr2O3 dispersions and the solute drag effect as well.

Air flow characteristics of an air-assisted sprayer through horizontal crop canopy

Artificially induced air currents or air-assistance to droplet spectrum produced by hydraulic nozzles not only facilitate in transporting and depositing the droplets in different parts of canopy but also reduce the application rate of chemicals.The air streams increase the velocity of smaller droplets so that extra momentum would increase impaction and improve penetration into the crop as well as mitigating the influence of wind on drift.It is necessary to quantify the airflow characteristics.But,control of climatic and other conditions in the field is very difficult.Thus,airflow characteristics study was done under controlled conditions on a horizontal simulated crop canopy.Based on this study,an airflow distribution model was developed and airflow characteristics for vegetable crops,namely,eggplant,chilli and bittergourd were predicted.The differences between predicted and actual field study values were not statistically significant.Kinetic energy of air stream dissipated with its movement from top to bottom of the canopy.The rate of kinetic energy dissipation was higher in denser canopies.Higher air velocity 15 m/s was the best as it produced maximum turbulence throughout the canopy.

Effects of air movement in a hot air dryer on the drying characteristics of colored potato (Solanum tuberosum L.) using computational fluid dynamics

The flow fields of hot air in the dryer for drying colored potatoes of which characteristics are highly sensitive to the temperature were simulated using computational fluid dynamics(CFD)simulation.The local air velocity decreased as the distance from the flow inlet increased.The mass and heat transfer coefficients increased from 0.666×10^(-2) m/s to 1.711×10^(-2) m/s,and 6.555 W/(m^(2)·K)to 16.834 W/(m^(2)·K),respectively,as the air velocity increased from 0.207 m/s to 1.567 m/s at 60°C.The drying simulation model using the heat and mass transfer model made accurate predictions.The thermal properties of colored potato,such as the thermal conductivity and specific heat,decreased significantly from 0.440 W/(m·K)to 0.034 W/(m·K)and 3906.45 J/(kg·K)to 2198.52 J/(kg·K),respectively,as the moisture content decreased from 78% to 5%.With the variable thermal and physical properties,the heat transfer simulation model made accurate predictions of the hot-air drying characteristics for the colored potatoes,and the RMSE values for all cases were(1.85±0.27)℃.

Characteristics of air flow driven by the free surface of the open channel

Spillway tunnels are a key structure in large-scale water conservancies. The high-head water inlet makes the water surface-velocity extremely high, and the air is driven by the free surface of the water to move downstream. This paper studies the air velocity distribution above the water surface through the model tests, under the assumption that the airflow is a turbulent boundary layer with a rough interface, and the influence of the water depth and the water velocity on the air velocity distribution is analyzed. It is shown that the air velocity is in an exponential distribution. As the measured position moves upward, the air velocity gradually decreases, and the gradient decreases. When the water depth increases, the air velocity increases but with the same distribution form. With the increase of the water surface-velocity, the air velocity at the same measuring point increases, the variation range near the water surface is large, the air boundary layer height increases slightly, and the index coefficient of the air velocity distribution function decreases. Through numerical fitting, the calculation formula of the air boundary layer thickness at different water surface velocities is obtained, along with the numerical value of the index coefficient.

New and innovative wind catcher designs to improve indoor air quality in buildings

Wind catchers used in various countries in Middle East and North Africa in order to improve indoor air environ-ment and to reduce reliance on cooling load.However,nowadays they are used across the globe with modern shapes and advanced techniques.The study focuses on investigating new and innovative shapes of wind catch-ers to improve air speed indoors which will elevate indoor comfort and air quality in buildings.The study used computer modeling CFD and a real model experiment to conduct the study.The study highlighted that curved shapes have highest pattern of wind speed driven,especially curved shape with double inlets.In addition,the study showed that octagon shape has the lowest pattern of wind speed driven because of its various sides which prevent air to flow easily inside the tunnel.

Experimental investigation into transient pressure pulses during pneumatic conveying of fine powders using Shannon entropy

This paper presents the results of an ongoing investigation into transient pressure pulses using Shan- non entropy. Pressure fluctuations （produced by gas-solid two-phase flow during fluidized dense-phase conveying） are recorded by pressure transducers installed at strategic locations along a pipeline. This work validates previous work on identifying the flow mode from pressure signals （Mittal, Mallick, ＆ Wypych, 2014）. Two different powders, namely fly ash （median particle diameter 45 μm, particle den- sity 1950 kg/m3. loosely poured bulk density 950 kg/m3） and cement （median particle diameter 15 p,m, particle density 3060 kg/m3, loosely poured bulk density 1070 kg/m3）, are conveyed through different pipelines （51 mm I.D. × 70 m length and 63 mm I.D. × 24 m length）. The transient nature of pressure fluc- tuations （instead of steady-state behavior） is considered in investigating flow characteristics. Shannon entropy is found to increase along straight pipe sections for both solids and both pipelines. However, Shannon entropy decreases after a bend. A comparison of Shannon entropy among different ranges of superficial air velocity reveals that high Shannon entropy corresponds to very low velocities （i.e. 3-5 m/s） and very high velocities （i.e. 11-14 m/s） while low Shannon entropy corresponds to mid-range velocities （i.e. 6-8 m/s）.

Experimental study on optimizing cheese drying and ripening process

The system proposed in this paper consists of humidity and temperature control during the food maturation process by using a dehumidifier equipped with a desiccant rotor containing silica gel.In this system the condensation/drainage stage is omitted since the humid room air is directed out of the cold store(process air)and the dried air is introduced via the dehumidifier inside the cold store.It allows separate control of the humidity and temperature inside the cold store.The experimental results are obtained in real conditions;the weight loss of the products was determined and it was,also,proved that dried products such as cheeses treated by this method retain their fresh color,texture and other organoleptic properties to ensure their final quality.

Flow, thermal, and vibration analysis using three dimensional finite element analysis for a flux reversal generator

This paper presents the simulation of major mechanical properties of a flux reversal generator （FRG） viz., computational fluid dynamic （CFD）, thermal, and vibration. A three-dimensional finite element analysis （FEA） based CFD technique for finding the spread of pressure and air velocity in air regions of the FRG is described. The results of CFD are mainly obtained to fine tune the thermal analysis. Thus, in this focus, a flow analysis assisted thermal analysis is presented to predict the steady state temperature distribution inside FRG. The heat transfer coefficient of all the heat producing inner walls of the machine are evaluated from CFD analysis, which forms the main factor for the prediction of accurate heat distribution. The vibration analysis is illustrated. Major vibration sources such as mechanical, magnetic and applied loads are covered elaborately which consists of a 3D modal analysis to find the natural frequency ofFRG, a 3D static stress analysis to predict the deformation of the stator, rotor and shaft for different speeds, and an unbalanced rotor harmonic analysis to find eccentricity of rotor to make sure that the vibration of the rotor is within the acceptable limits. Harmonic analysis such as sine sweep analysis to identify the range of speeds causing high vibrations and steady state vibration at a mode frequency of 1500 Hz is presented. The vibration analysis investi- gates the vibration of the FRG as a whole, which forms the contribution of this paper in the FRG literature.

Thermal performance of a lightweight building with phase change material under a humid subtropical climate

The use of phase change materials(PCMs)in building enclosures is an efficient way to reduce the heat gain and/or loss in summer and winter.It was evident that the thermal performance of buildings with PCMs was affected by the outdoor air temperature significantly.However,the influence of humidity,which was serious in the humid subtropical climate was unclear.To explore the effect of PCMs under a humid subtropical climate,the thermal performance of a lightweight building outfitted with PCMs with a melting temperature of 25°C was investigated.The actual outdoor air temperature with a humidity of 40-90 RH%and wind velocity of 2-6 m/s blowing from the east,west,south,and north was assumed for the performance assessment.A simulated model was developed using EnergyPlus and verified against experimental data.The energy savings by using PCMs was reduced from 3.9%to 2.6%when the outdoor humidity increased from 40 to 90 RH%in summer.However,the savings was not obvious in winter.Annual energy savings decreased from 1.64%to 1.32%with humidity increasing from 40 to 90 RH%.For annual condition,the average energy savings was reduced from 1.43%to 0.92%when the wind speed increased from 2 m/s to 6 m/s.From an economic point of view,the investment payback period was less than 10 years when the PCM price was lower than 18.0 Yuan/kg.

Effects of Annealing Below Glass Transition Temperature on the Wettability and Corrosion Performance of Fe-based Amorphous Coatings

This study investigated the effect of annealing below glass transition temperature(T_(g))on the microstructural characteristics,mechanical property,wettability,and electrochemical performance of activated combustion-high velocity air fuel(AC-HVAF)-sprayed Fe-Cr-Mo-W-C-B-Y amorphous coatings(ACs).Results showed that Fe-based ACs with a thickness of~300μm exhibited a fully amorphous structure with low oxidization.Originating from the reduced free volume,sub-T_(g) annealing increased the thermal stability,hardness,and surface hydrophobicity of Fe-based ACs.The enhanced corrosion resistance of sub-T_(g) annealed ACs in 3.5 wt%NaCl solution was attributed to the increased surface hydrophobicity and passivation capability.This finding elucidates the correlation between sub-T_(g) annealing and the properties of Fe-based ACs,which promotes ameliorating ACs with superior performance.