Effect Of Air Velocity Research Articles

Effect of air velocity on deep body temperature and weight gain in the broiler chicken

Tunnel ventilation has been adopted as an effective approach to combatting heat stress in poultry. Setting tunnel air velocity to levels that ensure bird comfort, while optimizing performance is an important goal. In recent years, biotelemetry has provided a way to effectively evaluate the impact of management practices on poultry physiology. In this study, we present an approach for evaluating the effects of heat stress and tunnel ventilation on poultry deep body temperature (DBT) using biotelemetry. Three consecutive experiments were conducted using 6 broilers, each at the ages of 8.6, 9.0, and 9.4 wk. Experiments spanned approximately 12 h each and led to 18 data sets. DBT responses of birds under no ventilation rose by as much as 3°C as a result of step increases in ambient temperature. Birds exposed to tunnel ventilation maintained a lower DBT by as much as 0.9°C. During experiment days, birds exposed to tunnel ventilation consistently gained weight with a percentage weight gain ranging from 1% to 11%. Birds not exposed to tunnel ventilation behaved less consistently with some gaining as much as 14% while others lost as much as 9%. Although further studies are required to derive more comprehensive and more statistically significant results, this study provided preliminary data that is needed to warrant such studies, and a stepping stone for making optimal management and risk assessment decisions that are based on physiological needs of the birds.

Mixing and segregation of solid particles in a conical spouted bed: Effect of particle size and density

In this work, the mixing and segregation of binary mixtures of particles with different sizes and densities in a pseudo-2D spouted bed were studied experimentally. A binary mixture of solid particles including sand, gypsum, and polyurethane was used. To determine the particles mass fraction, and their mixing and segregation in the bed, an image-processing technique was developed and used. Important hydrodynamic parameters, such as the axial and radial segregation profiles of the solid particles, were measured. The effects of air velocity, particle size, and particle mass fraction were also evaluated. The flow regime in the spouted bed and the time required for reaching the equilibrium state of the solid particles were discussed. The results showed that the segregation of solid particles and the time to equilibrium both decreased when the air velocity increased to much larger than the minimum spouting velocity. The axial segregation increased with the diameter ratio of the particles. Upon completion of the test, coarse particles were concentrated mainly in the spout region, while fine particles were aggregated in the annulus region. Examination of the flow pattern in the spouted bed showed that the particles near the wall had longer flow paths, while those near the spout region had shorter flow paths.

Effects of air temperature and velocity on the drying kinetics and product particle size of starch from arrowroot (Maranta arundinacae)

This study utilized the 3k factorial design with k as the two varying factors namely, temperature and air velocity. The effects of temperature and air velocity on the drying rate curves and on the average particle diameter of the arrowroot starch were investigated. Extracted arrowroot starch samples were dried based on the designed parameters until constant weight was obtained. The resulting initial moisture content of the arrowroot starch was 49.4%. Higher temperatures correspond to higher drying rates and faster drying time while air velocity effects were approximately negligible or had little effect. Drying rate is a function of temperature and time. The constant rate period was not observed for the drying rate of arrowroot starch. The drying curves were fitted against five mathematical models: Lewis, Page, Henderson and Pabis, Logarithmic and Midili. The Midili Model was the best fit for the experimental data since it yielded the highest R2 and the lowest RSME values for all runs. Scanning electron microscopy (SEM) was used for qualitative analysis and for determination of average particle diameter of the starch granules. The starch granules average particle diameter had a range of 12.06 – 24.60 μm. The use of ANOVA proved that particle diameters for each run varied significantly with each other. And, the Taguchi Design proved that high temperatures yield lower average particle diameter, while high air velocities yield higher average particle diameter.

Performance Investigation of Air Velocity Effects on PV Modules under Controlled Conditions

Junction temperature of PV modules is one of the key parameters on which the performance of PV modules depends. In the present work, an experimental investigation was carried out to analyze the effects of air velocity on the performance of two PV modules, that is, monocrystalline silicon and polycrystalline silicon under the controlled conditions of a wind tunnel in the presence of an artificial solar simulator. The parameters investigated include the surface temperature variation, power output, and efficiency of PV modules under varying air velocity from near zero (indoor lab. conditions) to 15 m/s. Additionally, the results were also determined at two different module angular positions: at 0° angle, that is, parallel to air direction and at 10° angle with the direction of coming air to consider the effects of tilt angles. Afterwards, the thermal analysis of the modules was performed using Ansys-Fluent in which junction temperature and heat flux of modules were determined by applying appropriate boundary conditions, such as air velocity, heat flux, and solar radiation. Finally, the numerical results are compared with the experiment in terms of junction temperatures of modules and good agreement was found. Additionally, the results showed that the maximum module temperature drops by 17.2°C and the module efficiency and power output increased from 10 to 12% with increasing air velocity.

A theoretical investigation of the distribution of indoor radon concentrations

Inhalation of radon (222Rn) and its decay products are a major source of natural radiation exposure. It is known from recent surveys in many countries that radon and its progeny contribute significantly to total inhalation dose and it is fairly established that radon when inhaled in large quantity causes lung disorder. In recent times, numerical modelling has become the cost effective replacement of experimental methods for the prediction and visualization of indoor pollutant distribution. The aim of this study is to implement the Finite Volume Method (FVM) for studying the radon distribution indoor. The findings show that the radon concentration which is distributed in a non-homogeneous way in the room is due to the difference in the radon concentration of different sources (wall, floor and ceiling). Moreover, the radon concentration is much larger near walls, and decreases in the middle of the room because of the effect of air velocity. We notice that the simulation results of radon concentration are in agreement with the results of other experimental studies. The annual effective dose of radon in the model room has been also investigated.

Experimental study on factors that influence the diameter of dry granulated particles

The development of heat recovery methods for dry granulation processes from blast furnace slag in the iron and steel industry is limited because of the high consumption of granulation energy during these processes. To determine the factors that influence the diameter of granulated particles, a paraffin test platform for gas quenching granulation was established. The influences of air velocity, air flow rate, liquid mass flow rate, and liquid pipe diameter on the final particle size and mass distribution were studied. Experimental results showed that the final particle size decreased (from 1.07 mm to 0.81 mm) with increasing air velocity (from 28.3 m/s to 113.2 m/s). However, when air velocity was higher than 60 m/s, its influence on particle diameter decreased significantly. The experimental data were analyzed using SPSS Statistics software, which indicated that the effect of air velocity on particle diameter was the most significant, followed by those of air flow and liquid pipe diameter. The effect of liquid mass flow was the least significant.

The Effect of Air Velocity on the Prevention of Heat Stress in Iranian Veiled Females

Background: Some environmental factors such as the ambient temperature, radiant temperature, humidity and air velocity as well as clothing and activity level are effective to induce heat strain on the workers. Objectives: The current study aimed to evaluate the effect of air velocity on Iranian veiled females at various exercise intensities and climatic conditions. Methods: The current experimental study was conducted on 51 healthy veiled females with Islamic clothing (n = 30) in two hot-dry climatic chambers (wet-bulb globe temperature (WBGT) = 32 ± 0.1°C and WBGT = 30 ± 0.1°C, 40% relative humidity (RH) without air velocity and (n = 21) with air velocity 0.31 m/s in sitting and light workload conditions, respectively, for 60 minutes. The WBGT, oral temperature and heart rate were measured simultaneously every five minutes during the heat exposure and resting state. Data were analyzed using correlation and line regression by SPSS ver. 16. Results: In both groups, oral temperature and heart rate increased during heat exposure. The increase of oral temperature and heart rate were larger in the group with air velocity (sitting position, 37.05 ± 0.20°C, 98.30 ± 7.79 bpm, light workload, 37.34 ± 0.24°C, 124.08 ± 6.09 bpm) compared those of the group without air velocity (sitting position, 36.70 ± 0.36°C, 69.74 ± 0.98 bpm, light workload, 36.71 ± 0.27°C, 110.78 ± 17.9 bpm). The difference in physiological strain index (PSI) between resting and low workload were higher in with air velocity group than those of the group without air velocity. Conclusions: The results showed that the heat stress increased by increasing air velocity and humidity in both groups. The air velocity with high humidity can be considered as a positive factor in the occurrence of heat strain. Therefore, the incidence of heat stress decreases with the increase of humidity and reduction of air velocity or with increase of air velocity and reduction of humidity in Iranian veiled females.

Investigation on Effect of Air Velocity in Turbulent Non-Premixed Flames

Abstract In this study, the turbulent non-premixed methane-air flame is simulated to determine the effect of air velocity on the length of flame, temperature distribution and mole fraction of species. The computational fluid dynamics (CFD) technique is used to perform this simulation. To solve the turbulence flow, k-ε model is used. In contrast to the previous works, in this study, in each one of simulations the properties of materials are taken variable and then the results are compared. The results show that at a certain flow rate of fuel, by increasing the air velocity, similar to when the properties are constant, the width of the flame becomes thinner and the maximum temperature is higher; the penetration of oxygen into the fuel as well as fuel consumption is also increased. It is noteworthy that most of the pollutants produced are NOx, which are strongly temperature dependent. The amount of these pollutants rises when the temperature is increased. As a solution, decreasing the air velocity can decrease the amount of these pollutants. Finally, comparing the result of this study and the other work, which considers constant properties, shows that the variable properties assumption leads to obtaining more exact solution but the trends of both results are similar.

Effect of Air Velocity and Drying Temperature on Drying Characteristics of Soybean (Glycine max) Using Hot Air Drying

Effect of Air Velocity and Drying Temperature on Drying Characteristics of Soybean (Glycine max) Using Hot Air Drying

Drying kinetics and mathematical modeling of hot air drying of coconut coir pith.

Drying kinetics of coir pith was studied and the properties of compressed coir pith discs were analyzed. Coir pith particles were oven dried in the range of temperatures from 100 to 240 °C and the rehydration ability of compressed coir pith was evaluated by finding the volume expansion. The optimum drying temperature was found to be 140 °C. Hot air drying was carried out to examine the drying kinetics by allowing the coir pith particles to fluidize and circulate inside the drying chamber. Particle motion within the drying chamber closely resembled the particle motion in a flash dryer. The effective moisture diffusivity was found to increase from 1.18 × 10−8 to 1.37 × 10−8 m2/s with the increase of air velocity from 1.4 to 2.5 m/s respectively. Correlation analysis and residual plots were used to determine the adequacy of existing mathematical models for describing the drying behavior of coir pith. The empirical models, Wang and Singh model and Linear model, were found to be adequate for accurate prediction of drying behavior of coir pith. A new model was proposed by modifying the Wang and Singh model and considering the effect of air velocity. It gave the best correlation between observed and predicted moisture ratio with high value of coefficient of determination (R2) and lower values of root mean square error, reduced Chi square (χ2) and mean relative deviation (E%).

Convective Regimes on Porous Media within Sudden Changed Channel due to Tangential Gas Flow

Study of lateral heat distribution in porous media caused by tangentially heated air flow is presented. Purpose of present study is to investigate effect of air velocity streamed tangentially, through a sudden enlarged-contracted channel, over a porous media layer toward heat distribution inside the layer. Air with temperature 373 K, as a heat source, is streamed over upper-facing of the porous layer, while its intake velocities are varied respectively at 0.5 to 2.5 m/s. Lower-facing of the porous layer, temperature is held on 313 K constant, as a heat sink. The consolidated porous layer is made from aluminum with porosity 38%. Important informations are obtained. Sudden enlarged-contracted channel generates non-linear heat transfer inside the porous media, whereas the suddenly enlarged channel enhances the molecular conductance, and the sudden contracted one increases the convective conductance.Thislaminar tangential gas flow yields the heat transfer takes respectively on free-, forced-, and combined-convective regime. It is also known that the combined convection is due to air flow at average Reynolds number 231.26.

Modeling and parametric studies for convective heat transfer in large, long and rough circular cross-sectional underground tunnels

With the increasing scarcity of fossil fuel, developing hydropower becomes one of the most important energy strategies. Underground tunnel ventilating has been used in many hydropower stations to save energy by precooling air. This study describes a measurement of heat transfer characteristics in the tunnel model. Based on the test results, the air temperature variation from inlets to outlets and the cooling capacity of the underground tunnel are discussed. Experimental results show that the surface roughness and air velocity both have influence on the heat transfer of the underground tunnels. With the relative roughness increasing, the temperature drop and cooling efficiency increase gradually. And the temperature drop and cooling efficiency increase sharply with the air velocity decreasing. Meanwhile, the effect of air velocity on the temperature drop and cooling efficiency is more significant than that of the relative roughness. In addition, the air temperature decreased rapidly with the increase of length. After a certain length, the air temperature and cooling efficiency almost change no more. And cooling efficiency reaches a stable value at 90%–95%. Therefore, using underground tunnel as a giant natural “air conditioner” is an energy-saving ventilation method; it has significant economic and environmental benefits.

Pyrite enrichment in vibrated fluidized bed based on density segregation

ABSTRACTIt is of significance for the environmental protection, the shortage of water, and the economic benefits to recovering the pyrite from the gangue with high sulphur content (GHSC) by the vibrated fluidized bed. In this study, characteristics such as the sulphur form of pyrite, size distribution, and dissociation degree of sample were analysed. Based on the above analysis, a vibrated fluidized bed was first used for the pyrite enrichment from GHSC. The effect of air velocity, vibration intensity, and bed height on the separation performance was analysed by separation experiments. The results show that the separation efficiency increased firstly and then decreased with increasing gas velocity, vibration intensity, and bed height. The total sulphur contents (TSCs) of −6 + 3, −3 + 1, and −1 + 0.5 mm size fraction materials were up to 37.94%, 35.43%, and 30.61%, respectively, and the enrichment grades were 1.72, 1.90, and 2.29 times, respectively, under the optimal conditions, indicating that using a vibrated fluidized bed was efficient for the pyrite enrichment.

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.

Effect of air velocity in dehumidification drying environment on one-component waterborne wood top coating drying process

ABSTRACTIn this study, the effect of air velocity in dehumidification drying environment on one-component waterborne wood top coating drying process is analyzed by drying time and moisture content and surface temperature of coating, in which air temperature is 35°C and relative humidity is 50%, and the air velocity is the only change parameter, varying from 0.2 to 1.2 m/s. It is found that drying time of top coating shortens and moisture content of top coating decreases with increasing air velocity. Surface drying time is about 15 min, hard drying time 21 min, and sanded drying time 37 min. To accelerate the drying speed, the air velocity is increased to more than 0.4 m/s. Moisture content of top coating is 58.2% during surface drying, 31.4% during hard drying, and 21.9% during sanded drying time. An infrared thermometer is used to measure the surface temperature of coating. Surface temperature of top coating is 30.0°C when it is dried to the surface drying degree, 33.5°C when the top coating is dried to the hard drying degree, and 34.6°C when the top coating is dried to the sanded drying degree. The drying degree of coating can be judged from the drying time and surface temperature and moisture content of coating. The drying degree of top coating is better when surface temperature is higher and the moisture content is lower.

Parametric Analysis of Heat Exchanger Thermal Performance in Complex Geometries—Effect of Air Velocity and Water Flow Distributions

The thermal performance of automotive heat exchangers is greatly affected by the relationship that binds the nonuniformities in flow velocity and the distribution of upstream temperatures. Consequently, an in-house two-dimensional code is established to evaluate the thermal performance based on known parameters, namely, distribution of upstream velocity of an air–liquid heat exchanger, the flow rate of heat exchanger liquid, and the inlet air and liquid temperatures. A parametric research study is then performed to confirm the relation between the thermal performance of the heat exchanger and these different parameters. It was observed that nonuniformities in air velocity and water flow distributions decrease the thermal performance of a heat exchanger by up to 33 and 42%, respectively.

Experimental Comparative Study on Lithium Chloride and Calcium Chloride Desiccants

Desiccants liquid or solid can be used in conjunction with solar energy to provide a viable alternative to traditional air-conditioning technique. In order to select the best desiccant for using in the liquid desiccant cooling system an experimental comparative study has been carried out on dehumidification/ regeneration process using CaCl2 and LiCl under the same operating conditions. The effect of air velocity and relative humidity on these processes has been analyzed. It is found that these two desiccants are able to attract moisture from the air and can be regenerated at low temperature 40°C. LiCl and CaCl2 are able to undergo successive cycles during many days by obtaining nearly their concentration. The concentration gap between the regeneration phases is very small within an average of 0.003% for CaCl2 and 0.042% for LiCl. The amount of water absorbed is nearly equal to the amount of water desorbed, in equilibrium condition, for a complete cycle. The comparison shows that, in the dehumidification process, the mass transfer potential of LiCl solution is better than that of CaCl2 solution in the same desiccant mass. On the other hand, in the regeneration process, CaCl2 solution shows better mass transfer potential compared with LiCl solution. For using in (LDCS), CaCl2 is very cheap while has the poorest absorption ability, but the ability of LiCl to dehumidify is far better. Also, it is found that a higher Reynolds number gives a higher potential of mass transfer.

Experimental study on water-cooled thermoelectric cooler for CPU under severe environment

In this paper, water-cooled thermoelectric cooler (TEC) for central processing unit (CPU) is developed. Two temperature controls for TEC are proposed and compared to prevent condensation on CPU and save energy. Performances of TEC with the two temperature controls are experimentally investigated under different operating conditions and environmental temperatures. Effects of air velocity and water mass flow rate for the heat sink are investigated under severe environment. Dynamic performance comparisons of three cooling methods, including TEC with and without temperature control and passive water cooling, are investigated under variable operating conditions at severe environment. Experimental results show that temperature of CPU (Tcpu) for SC is lower than that for OC when Tcpu is lower than the set temperature. A higher COP can be kept when air velocity and water mass flow rate is 0.8 ms−1 and 0.042 kg s−1, respectively. The largest temperature variation of Tcpus is lower than 1.5 °C under variable operating conditions at severe environment.

Effect of air velocity on nanoparticles dispersion in the wake of a vehicle model: Wind tunnel experiments

Exposure to nanoparticles coming from road–traffic concerns a large part of urban population in both outdoor and indoor environments leading to the enhancement of short and long–term health problems. The dynamics of such small particles is very sensitive to the turbulent diffusion and Brownian motion. Hence their concentrations are dependent on the flow structure properties (length and time scales). In this paper, a wind tunnel study is conducted to assess the effect of the flow on the dispersion of nanoparticles coming out from tailpipe in the near–wake of a reduced–scale truck model. Particle number concentration (PNC) measurements are achieved at 66 positions downstream of the model. Our results point out that the interaction of the ultrafine particles (UFP) with the vortices appearing in the near-wake of a truck enhances their dispersion in both transversal and vertical directions. Increasing the inflow air velocity strengthens this spreading. Overall, we demonstrate that such wind tunnel measurements are fundamental to improve our knowledge on the existing interaction between road–traffic, turbulence and particle concentration to accurately evaluate human exposure rates to ultrafine particles and their potential consequences.

Effect of Air Velocity on Laying Hen Performance and Egg Quality

<abstract> <b><sc>Abstract.</sc></b> Increasing convective cooling can improve the performance and thermal comfort of commercial poultry when weather or system design limit cooling through other means such as evaporative cooling. Previous work in young hens showed increased egg production rate as feed intake was maintained under heat stress conditions. However, the effects of increased convective cooling on live performance or egg quality in older hens have not been evaluated. The objective of this study was to evaluate the effects of different air velocities on live performance of laying hens from 39 to 48 weeks of age and resultant egg quality. Air velocity treatments included still air, constant 0.76 m s^-1, and constant 1.52 m s^-1. The temperature and relative humidity in the experimental room were maintained at 27.8°C and 82%, respectively. Two 10-week trials were conducted, with two replicate treatment units per trial, for a total of four replicate treatment units. Hens were obtained from a commercial farm, placed in wind tunnels, and provided feed and water ad libitum. Lighting was provided per primary breeder guidelines. Eggs were collected daily, and feed intake was assessed weekly; egg quality attributes including egg weight, albumen quality (Haugh unit score), incidence of meat and blood spots, and egg shell strength were measured twice weekly. Hen-day egg production increased 6.3% and 6.7% over still air for 0.76 and 1.52 m s^-1, respectively (p < 0.0001). Feed intake was significantly depressed for still air when compared to air velocity treatments (p < 0.0001). Mean egg weight increased with increasing air velocity and was significantly different for all treatments (p < 0.0001). Albumen height and quality (Haugh unit) decreased with increasing air velocity and were significantly different between the still air and 1.52 m s^-1 treatments (p < 0.0038). Shell breaking strength significantly decreased for the still air treatment (p < 0.0001) when compared to the air velocity treatments; shell breaking strength was not different between the 0.76 and 1.52 m s^-1 treatments.