scholarly journals Experimental results on air permeability of agricultural nets

2016 ◽  
Vol 47 (3) ◽  
pp. 134 ◽  
Author(s):  
Sergio Castellano ◽  
Giuseppe Starace ◽  
Lorenzo De Pascalis ◽  
Marco Lippolis ◽  
Giacomo Scarascia-Mugnozza
Keyword(s):  
Pressure Drop ◽  
Wind Tunnel ◽  
Air Flow ◽  
Loss Coefficient ◽  
Experimental Results ◽  
Equivalent Diameter ◽  
Air Velocity ◽  
Low Wind Speed ◽  
Technical Textiles ◽  
Set Up

In order to evaluate the influence of the texture characteristics of agricultural nets on the air flow passing through them, a micro wind tunnel was designed and built in the testing and engineering laboratory of Sachim s.r.l., an Italian high-density polyethylene (HDPE) technical textiles manufacturer. The micro wind tunnel (0.1345 m diameter) allowed the simultaneous measurement of the air flowrate and the pressure drop through a net sample. The equipment was designed to set up the inclination of the net samples with respect of the airflow at fixed angles (90°, 60°, 45°, 30°). The variation of the pressure drop with the air velocity on four different flat woven round monofilament HDPE nets perpendicular to the air flow are here reported. In all cases the air velocity measured into the micro wind tunnel was above 4 m s–1 hence reported results do not consider low wind speed. Preliminarily, the loss coefficient was assumed as a function of porosity and Reynolds number, calculated with reference to the equivalent diameter of the pores, FS(Rel,ε) and showed percent deviations form experimental results in the range 14.6%÷25.3%. Hence a simplified expression of the loss coefficient, depending only on the porosity was proposed, FS(ε) which highlighted differences with experimental results in the range 3.5%÷20.3%. Finally, results were compared with those based on the Bernoulli’s principle found in the literature.

Temperature Distribution of Hot Air Flow in Heating Zone for Drying Application

2014 ◽  
Vol 627 ◽  
pp. 153-157
Author(s):  
Nawadee Srisiriwat ◽  
Chananchai Wutthithanyawat
Keyword(s):  
Temperature Distribution ◽  
Air Temperature ◽  
Power Supply ◽  
Air Flow ◽  
Heating Zone ◽  
Velocity Control ◽  
Rectangular Duct ◽  
Air Velocity ◽  
Hot Air ◽  
Set Up

The temperature distribution of hot air flow in heating zone of a rectangular duct has been investigated for drying application. The experimental set-up consists of a heater and a fan to generate the hot air flow in the range of temperature from 40 to 100°C and the range of air velocity between 1.20 and 1.57 m/s. An increase of the heater power supply increases the hot air temperature in the heating zone while an increase of air velocity forced by fan decreases the initial temperature at the same power supply provided to generate the hot air flow. The temperature distribution shows that the hot air temperature after transferring through air duct decreases with an increase of the length of the rectangular duct. These results are very important for the air flow temperature and velocity control strategy to apply for heating zone design in the drying process.

Air Flow Analysis in Square Duct Bend

2014 ◽  
Vol 695 ◽  
pp. 622-626 ◽  
Author(s):  
Mohamad Nor Musa ◽  
Mohd Nurul Hafiz Mukhtar
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Cross Section ◽  
Air Flow ◽  
Flow Analysis ◽  
Maximum Velocity ◽  
Maximum Pressure ◽  
Air Velocity ◽  
Square Duct ◽  
Inlet Velocity

This paper present new result for experimental analysis of air flow velocity and pressure distributions between two ducts bend: (1) 90° duct bend with a single turning vane having 0.03m radius and (2) 90° duct bend with double turning vane, in 0.06 × 0.06 m duct cross section. The experiment used five different Reynolds numbers chosen between the ranges 1 ×104 and 6×104. Each experiment has four point measurements: (1) point 1 and point 2 at cross section A-A and (2) point 3 and point 4 at cross section B-B. The first experimental study used single turning vane radius 0.03m with inlet air velocity from 2.5m/s to 12.2m/s. And for the second experiment that used square turning vane with 0.03m radius. In experiment 2, the inlet air velocity also start from 2.5m/s to 12.2m/s. From analysis results, the pressure drop in experiment 1 is higher than experiment 2. As example the maximum pressure drop at 7.5m/s inlet air velocity between point 1 and 3 was found to be 71.6203 Pa in experiment 1 as compared to 61.8093 Pa in experiment 2. The velocity after duct bend is greater when using double turning vane compare used single turning vane as maximum velocity at point 3 in experiment 2 compare to velocity at point 3 in experiment 1 that is 55.677× 10-4 m/s and 54.221× 10-4 m/s. The velocity at duct wall is equal to zero. When increase the value of Reynolds number or inlet velocity, the maximum velocity and total pressure also increase. For example in experiment 1 at point 1, the velocity is 48.785 × 10-4 m/s at Reynolds number 1 ×104 and velocity 65.115×10-4 m/s at Reynolds number 12.2 ×104 . Velocity flow in duct section are lower than inlet velocity. In experiment 1, the inlet velocity is 2.5m/s meanwhile the maximum velocity in the duct section at point 2 is 73.075×10-4 m/s that is much more lower than inlet velocity.

scholarly journals Experimental and CFD Investigation on Flow Behaviors of a NPP Pump under Natural Circulation Condition

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Weitong Li ◽  
Lei Yu ◽  
Jianli Hao ◽  
Mingrui Li
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Flow Field ◽  
Natural Circulation ◽  
Internal Flow ◽  
Loss Coefficient ◽  
Experimental Results ◽  
Passive Safety ◽  
Passive Safety System ◽  
Circulation Condition

Passive safety system is the core feature of advanced nuclear power plant (NPP). It is a research hotspot to fulfill the function of passive safety system by improving the NPP natural circulation capacity. Considering that the flow behaviors of stopped pump pose a significant effect on natural circulation, both experimental and computational fluid dynamics (CFD) methods were performed to investigate the flow behaviors of a NPP centrifugal pump under natural circulation condition with a low flow rate. Since the pump structure may lead to different flows depending on the flow direction, an experimental loop was set up to measure the pressure drop and loss coefficient of the stopped pump for different flow directions. The experimental results show that the pressure drop of reverse direction is significantly greater than that of forward direction in same Reynolds number. In addition, the loss coefficient changes slightly while the Reynolds number is greater than 8 × 104; however, the coefficients show rapid increase with the decrease in Reynolds number under lower Reynolds number condition. According to the experimental data, an empirical correlation of the pump loss coefficient is obtained. A CFD analysis was also performed to simulate the experiment. The simulation provides a good accuracy with the experimental results. Furthermore, the internal flow field distributions are obtained. It is observed that the interface regions of main components in pump contribute to the most pressure losses. Significant differences are also observed in the flow field between forward and reverse condition. It is noted that the local flows vary with different Reynolds numbers. The study shows that the experimental and CFD methods are beneficial to enhance the understanding of pump internal flow behaviors.

scholarly journals GUIDELINES FOR THE DESIGN OF AIR BUBBLE SYSTEMS

1976 ◽  
Vol 1 (15) ◽  
pp. 170
Author(s):  
Nabil Ismail
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Air Flow ◽  
Water Systems ◽  
Experimental Results ◽  
Air Flow Rate ◽  
Air Bubble ◽  
Proper Design ◽  
Comprehensive Study ◽  
The Ideal

Based on a literature review of theoretical and experimental work on air-bubble systems, guidelines for the ideal design of submerged distributors discharging air into water are presented. A comprehensive study of gas-liquid dispersions was carried out to find out the effect of physical properties, distributor arrangement, and the air flow rate, on the flow pattern within the jet. This review revealed that the distributor arrangement largely influences the characteristics of the dispersion within the zone of flow establishment. Also, upon analyzing the experimental results of air-water systems, it was found that the zone of flow establishment extends to greater distances of the water depth than that in the case of one-phase turbulent plumes. Furthermore, the experimental results showed that the efficiency of air bubble plumes can be increased by the proper design of the distributor. Recommendations for the distributor design are given, which include, diameter of orifices and their spacings, pressure drop across orifices, number of manifolds, and the maximum air flow rate.

scholarly journals Experimental Study on the Atomization of Plain Orifice Injector Under Uniform and Non-Uniform Cross Flowing Air Stream

1987 ◽  
Author(s):  
Yan Zhang ◽  
Jun Yong Zhu ◽  
Li Xin Wang ◽  
Ju Shan Chin
Keyword(s):  
Pressure Drop ◽  
Flow Velocity ◽  
Air Flow ◽  
Cross Flow ◽  
Orifice Diameter ◽  
Air Velocity ◽  
Air Stream ◽  
Nozzle Pressure ◽  
Large Orifice ◽  
Air Flow Velocity

The effects of three parameters: air velocity, nozzle pressure drop and injector orifice diameter, on the spray characteristics of a plain orifice injector under uniform and non-uniform cross flowing air stream have been studied experimentally. For uniform cross flowing air stream, the results show that the effects of these parameters are interrelated. The exponents of these terms in a correlation are not constants. Based on a very large amount of experimental data, the following correlation has been derived for Sauter Mean Diameter. SMD = 8.28 • 10 4 V ¯ a A • Δ P ¯ f B • d ¯ C where: A = −1.59 −0.0044ΔP̄f −0.01 d̄ B = −0.13 −0.025 d̄ +0.34 Ma C = 0.36 −0.55 Ma −0.0032ΔP̄f (Va ≤ 140 M/s ; ΔPf ≤ 11 Kg·f/cm2 ; d ≤ 2.5 mm) For small orifice diameters, the drop size distribution parameter, N (Rosin-Rammler distribution ), decreases until a minimum then increases with air velocity. For large orifice diameters, it decreases with air velocity. N always decreases with the increases of nozzle pressure drop or orifice diameter. For non-uniform cross flowing air stream, atomizations under four velocity profiles with same averaged velocity and with a velocity recess of same shape but at different radial positions have been tested. The atomization data were compared with that of uniform cross flowing air stream. Two types of comparison were made based on: a) the undisturbed velocity, b) the averaged velocity, equals to the velocity of uniform cross flowing air stream. For former situation the atomization for non-uniform cross flowing air stream tested is always poorer. The influence from the velocity recess will be maximum at certain nozzle pressure drop. The experimental evidence obtained has shown that cross flow atomization is a combination of pressure atomization (at low air flow velocity) and airblast atomization (at high air flow velocity).

Modification of MnS inclusion by tellurium in 38MnVS6 micro-alloyed steel

2020 ◽  
Vol 117 (6) ◽  
pp. 615
Author(s):  
Ping Shen ◽  
Lei Zhou ◽  
Qiankun Yang ◽  
Zhiqi Zeng ◽  
Kenan Ai ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Aspect Ratio ◽  
Strong Influence ◽  
Experimental Results ◽  
Alloyed Steel ◽  
Equivalent Diameter ◽  
Small Aspect Ratio ◽  
Steel Quality ◽  
Eds Analysis ◽  
Micro Alloyed Steel

In 38MnVS6 steel, the morphology of sulfide inclusion has a strong influence on the fatigue life and machinability of the steel. In most cases, the MnS inclusions show strip morphology after rolling, which significantly affects the steel quality. Usually, the MnS inclusion with a spherical morphology is the best morphology for the steel quality. In the present work, tellurium was applied to 38MnVS6 micro-alloyed steel to control the MnS inclusion. Trace tellurium was added into 38MnVS6 steel and the effect of Te on the morphology, composition, size and distribution of MnS inclusions were investigated. Experimental results show that with the increase of Te content, the equivalent diameter and the aspect ratio of inclusion decrease strikingly, and the number of inclusions with small aspect ratio increases. The inclusions are dissociated and spherized. The SEM-EDS analysis indicates that the trace Te mainly dissolves in MnS inclusion. Once the MnS is saturated with Te, MnTe starts to generate and wraps MnS. The critical Te/S value for the formation of MnTe in the 38MnV6 steel is determined to be approximately 0.075. With the increase of Te/S ratio, the aspect ratio of MnS inclusion decreases and gradually reaches a constant level. The Te/S value in the 38MnVS6 steel corresponding to the change of aspect ratio from decreasing to constant ranges from 0.096 to 0.255. This is most likely to be caused by the saturation of Te in the MnS inclusion. After adding Te in the steel, rod-like MnS inclusion is modified to small inclusion and the smaller the MnS inclusion, the lower the aspect ratio.

Air flow quality analysis of an open-circuit boundary layer wind tunnel and comparison with a closed-circuit wind tunnel

2020 ◽  
Vol 32 (12) ◽  
pp. 125120
Author(s):  
María Jiménez-Portaz ◽  
Luca Chiapponi ◽  
María Clavero ◽  
Miguel A. Losada
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Air Flow ◽  
Open Circuit ◽  
Closed Circuit ◽  
Quality Analysis ◽  
Flow Quality

scholarly journals Galloping Stability and Wind Tunnel Test of Iced Quad Bundled Conductors considering Wake Effect

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Xiaohui Liu ◽  
Ming Zou ◽  
Chuan Wu ◽  
Mengqi Cai ◽  
Guangyun Min ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Transmission Lines ◽  
Degrees Of Freedom ◽  
Wind Tunnel Test ◽  
Aerodynamic Coefficients ◽  
Wake Effect ◽  
Aerodynamic Coefficient ◽  
Set Up ◽  
The Stability ◽  
Three Degrees Of Freedom

A new quad bundle conductor galloping model considering wake effect is proposed to solve the problem of different aerodynamic coefficients of each subconductor of iced quad bundle conductor. Based on the quasistatic theory, a new 3-DOF (three degrees of freedom) galloping model of iced quad bundle conductors is established, which can accurately reflect the energy transfer and galloping of quad bundle conductor in three directions. After a series of formula derivations, the conductor stability judgment formula is obtained. In the wind tunnel test, according to the actual engineering situation, different variables are set up to accurately simulate the galloping of iced quad bundle conductor under the wind, and the aerodynamic coefficient is obtained. Finally, according to the stability judgment formula of this paper, calculate the critical wind speed of conductor galloping through programming. The dates of wind tunnel test and calculation in this paper can be used in the antigalloping design of transmission lines.

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