Air supply in zigzag-type DMFC with internal air flow channel

2013 ◽  
Author(s):  
Toshiyuki Ishikake ◽  
Toshiaki Yachi
Keyword(s):  
Air Flow ◽  
Flow Channel ◽  
Air Supply ◽  
Zigzag Type

scholarly journals Particle reentrainment from powder bed of fine particles in a rectangular air-flow channel.

1985 ◽  
Vol 11 (1) ◽  
pp. 48-54 ◽  
Author(s):  
Hiroaki Masuda ◽  
Shuji Matsusaka ◽  
Shunya Ikumi
Keyword(s):  
Fine Particles ◽  
Air Flow ◽  
Flow Channel ◽  
Powder Bed

Modeling of Flooding Phenomena in Hydrophobic Gas Diffusion Layer of PEFC

2007 ◽  
Author(s):  
Kazuhiko Kudo ◽  
Akiyoshi Kuroda ◽  
Shougo Takeoka ◽  
Yosuke Shimazu
Keyword(s):  
Diffusion Layer ◽  
Liquid Water ◽  
Air Flow ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
Flow Channel ◽  
Cathode Side ◽  
Model Following ◽  
Condensed Water ◽  
Different Diameters

The mechanism of liquid water removal, water vapor diffusion and oxygen diffusion in cathode side gas diffusion layer (GDL) of PEFC is studied by modeling the GDL as a hydrophobic flat plate with many straight holes with different diameters. As the results of the consideration using the model, following results are obtained. The spots where liquid water condensation is taken place between GDL-MEA gap are limited to the inlets of holes with larger diameters, and the condensed water is drained to air flow channel only through the larger holes. Other holes with smaller diameters are free of liquid water, and oxygen diffuses from the air flow channel to the catalyst surface through such holes. The reduction of output voltage of fuel cell due to the increase in the current density may be caused by the reduction of the oxygen concentration in GDL-MEA gap. The condensate tends to penetrate into larger holes instead of filling the gap of GDL and MEA.

Enhanced Liquid Water Removal From PEM Fuel Cell Flow Channels by Superimposing Acoustic Pressure Wave on Air Flow

2019 ◽  
Author(s):  
Mehdi Mortazavi ◽  
Anthony D. Santamaria ◽  
Jingru Benner ◽  
Vedang Chauhan
Keyword(s):  
Acoustic Pressure ◽  
Air Flow ◽  
Acoustic Vibration ◽  
Flow Channel ◽  
Water Removal ◽  
Two Phase ◽  
Pressure Drops ◽  
Acoustic Pressure Wave ◽  
Water Accumulation ◽  
Flow Pressure

Abstract Enhanced water removal from the flow channel of an ex-situ PEM fuel cell test section is obtained by superimposing acoustic pressure wave on air flow prior to entering into the flow channel. Water accumulation within the flow channel was visualized with a CCD camera and liquid-gas two-phase flow pressure drop was measured along the flow channel. Acoustic pressure waves were superimposed in sine waves at different frequencies between 20 and 120 Hz with a 20-Hz interval. Results indicated that water accumulation in the flow channel was lowest when acoustic pressure waves were superimposed at 80 Hz on air flow. For experiments with no acoustic vibration, the average water slug cumulative area for three runs was obtained at 288.6 mm2 while this average was as low as 43.9 mm2 for experiments conducted at 80 Hz. For other frequencies tested (20, 40, 60, 100, and 120 Hz), water accumulation within the flow channel was less than that for experiments with no vibration but the accumulation of water was still greater than experiments conducted at 80 Hz. The two-phase flow pressure drops were also lowest for experiments conducted at 80 Hz while the highest pressure drops were obtained in experiments with no acoustic vibration. Droplets were also visualized from a side-view angle in a goniometer in order to obtain contact angles. Images showed droplet oscillation under the influence of acoustic vibration. For the three superficial air velocities tested in this study (1.30, 1.82, and 2.30 m/s) the contact angle hysteresis were almost identical with an average value around 40°.

Effect of Gravity on Droplet Growth and Detachment Inside a Simulated PEM Fuel Cell Air Flow Channel With Hydrophobic Walls

2013 ◽  
Author(s):  
Andres Munoz ◽  
Abhijit Mukherjee
Keyword(s):  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Air Flow ◽  
Pem Fuel Cell ◽  
Proton Exchange ◽  
Droplet Growth ◽  
Flow Rates ◽  
Air Supply ◽  
Supply Channel ◽  
Exchange Membrane

Water management still remains a challenge for proton exchange membrane fuel cells. Byproduct water formed in the cathode side of the membrane is wicked to the air supply channel through the gas diffusion layer. Water emerges into the air supply channel as droplets, which are then removed by the air stream. When the rate of water production is higher than the rate of water removal, droplets start to accumulate and coalesce with each other forming slugs consequently clogging the channels and causing poor fuel cell performance. It has been shown in previous experiments that rendering the channels hydrophobic or super-hydrophobic cause water droplets to be removed faster, not allowing time to coalesce, and therefore making channels less prone to flooding. In this numerical study we analyze water droplet growth and detachment from a simulated hydrophobic air supply channel inside a proton exchange membrane (PEM) fuel cell. In these numerical simulations the Navier-Stokes equations are solved using the SIMPLER method coupled with the level set technique in order to track the liquid-vapor interface. The effect of the gravity field acting in the −y, −x, and +x directions was examined for an array of water flow rates and air flow rates. Detachment times and diameters were computed. The results showed no significant effect of the gravity field acting in the three different directions as expected since the Bond and Capillary numbers are relatively small. The maximum variations in detachment time and diameter were found to be 8.8 and 4.2 percent, respectively, between the horizontal channel and the vertical channel with gravity acting in the negative x direction, against the air flow. Droplet detachment was more significantly affected by the air and water flow rates.

Turbulent Pressure-Velocity Measurements in a Fully Developed Concentric Annular Air Flow

1983 ◽  
Vol 105 (3) ◽  
pp. 345-354 ◽  
Author(s):  
R. J. Wilson ◽  
B. G. Jones
Keyword(s):  
Velocity Field ◽  
Pressure Field ◽  
Air Flow ◽  
Pressure Fluctuations ◽  
Core Region ◽  
Flow Channel ◽  
Wall Pressure ◽  
Analysis Method ◽  
Local Pressure ◽  
Wall Pressure Fluctuations

An experimental study of the fluctuating velocity field and the fluctuating static wall pressure in an annular turbulent air flow system with a radius ratio of 4.314 has been conducted. The study included direct measurements of the mean velocity profile, turbulent velocity field and fluctuating static wall pressure from which the statistical values of the turbulent intensity levels, power spectral densities of the turbulent quantities, and the cross-correlation between the fluctuating static wall pressure and the fluctuating velocity field in the core region of the flow were obtained. The effect of the turbulent core region of the flow on the wall pressure fluctuations was studied by cross-correlating the axial and radial velocity components with the wall pressure fluctuations. A three-sensor, signal subtraction data analysis method using coherence techniques was developed to separate the superimposed local pressure fluctuations and acoustically transmitted noise. This analysis method is shown to adequately isolate the local pressure fluctuation information at each wall of the flow channel. The results of the experimental measurements are compared with existing experimental and numerical information on turbulent annular flow fields and wall pressure statistics. The pressure-velocity correlation indicates that a substantial contribution to the pressure field on the wall of the flow channel is from the turbulent core region outside of the boundary layer. The wall pressure field is shown to be significantly different on the two dissimilar walls. The pressure-velocity correlations show that this difference is due to the geometric difference between the dissimilar volumetric sources which contribute to the wall pressure field. The results of this study show that vibration modeling must incorporate the effects of the flow geometry on the wall pressure statistics, which are used as the driving force for flow-induced vibrations.

Improved air supply method to increase power density of a zigzag-type DMFC

Intelec 2012 ◽  
2012 ◽  
Author(s):  
Toshiyuki Ishikake ◽  
Masanori Aihara ◽  
Toshiaki Yachi
Keyword(s):  
Power Density ◽  
Air Supply ◽  
Zigzag Type

scholarly journals 544 PB 084 AIR SUPPLY FOR LETTUCE TIPBURN PREVENTION AND ITS EFFECTS ON TRANSPIRATION AND PHOTOSYNTHESIS

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 509d-509
Author(s):  
Jan M. Kossowski ◽  
Darlene A. Wilcox ◽  
Robert Langhans
Keyword(s):  
Air Flow ◽  
Optimal Growth ◽  
Lower Percentage ◽  
Limiting Factor ◽  
Diurnal Changes ◽  
Air Supply ◽  
Nutrient Film Technique ◽  
Plastic Sleeve ◽  
Rate Of Photosynthesis ◽  
Flow Treatment

Tipburn is considered a major limiting factor to lettuce production in greenhouses and controlled environment agriculture facilities. Conditions which promote optimal growth also result in high levels of tipburn incidence. It has been reported that air flow directed at inner leaves of rapidly growing lettuce can prevent tipburn without a concurrent reduction of growth, assumedly due to increased transpiration with increased air movement over leaf surfaces. Lettuce was grown in the greenhouse in nutrient film technique, with additional lighting providing total of 17 to 19 mol m-2 d-1 of PAR. Control plants developed tipburn 20 to 25 days after seeding. Plants with air supplied to inner leaves by a perforated plastic sleeve did not develop tipburn up to 35 days after seeding. Diurnal changes in physiological parameters were measured starting one week prior to harvest. Leaves of control plants had significantly higher stomatal conductance and transpiration than did those of air-supplied plants, although diurnal patterns of control and air-treated plants were similar. Air flow treatment had no significant effect on the rate of photosynthesis. However, air-supplied plants had a slightly lower percentage of dry matter than control plants. The apparent growth reduction resulting from the air flow treatment evidently reduced the demand for calcium.

scholarly journals Air distribution in convex wall jets for ventilation with a constant air flow

2021 ◽  
Vol 36 ◽  
pp. 37-50
Author(s):  
V. Korbut ◽  
Viktor Mileikovskyi
Keyword(s):  
Air Flow ◽  
Capital Investments ◽  
Outdoor Air ◽  
Wall Jets ◽  
Air Conditioners ◽  
Working Zone ◽  
Cooling Period ◽  
Air Supply ◽  
Convex Wall ◽  
Air Exchange

The scheme of air exchange organization using air supply above a working zone by convex wall jets that interact with each other has been substantiated. This scheme is advisable in cases where it is impossible to supply air directly to the working zone. It provides optimal microclimate parameters with minimal recirculation of polluted air from the upper zone. Simulation of the air exchange organization in an exhibition hall in International Exhibition Centre in Kyiv with ventilation at a constant air volume (CAV) has been performed. The floor area is 5258 m2, the height is 19 m, the minimum outdoor air flow is 21.667 m3/s (78000 m3/h). The current design scheme of air exchange organization is zonal. General air exchange is 43.3333 m3/s (156000 m3/h). Recirculation is accepted 50 %. The air flow supplied in the upper and middle zones is, respectively, 22.5 m3/s (81000 m3/h) and 20.833 m3/s (75000 m3/h). Inlet air has temperature 291.65 K (18.5 °C). It is supplied downward by twisted jets. There are 65 Trox VDL-AHLD-E3/800/0/0/0/RAL 9010 air diffusers with a diameter of 800 mm. The proposed scheme is single-zonal using 24 diffusers PES-D-8-10/15-0,9 4 m above the floor and air removal from the upper zone. This scheme allows halving the air exchange to the minimum outdoor air without recirculation. The air temperature should be decreased by 3.3 K to 288.35 K (15.2 °С). The number of air-conditioners is decreased twice. The calculated consumption of cold decreased by 65.58 W/m2 or 29 %, the calculated consumption of heat for the second heating – by 7.17 W/m2 or 18 %. Saving of capital investments in prices of February 2020 is 792.16 UAH/m2 or 55 %, and decrease of operating costs for the cooling period is 6.61 UAH/m2 or 15 %. Thus, the system is economically beneficial from the beginning of its installation. In the future, its operation will be simulated in a mode with a variable flow rate.

Theoretical Study on Thermal Performance of Trombe Wall Combined with Solar Air Collector

2012 ◽  
Vol 512-515 ◽  
pp. 208-213
Author(s):  
Yu Bie ◽  
Fang Zhou ◽  
Ming Fu Hu ◽  
Qian Peng ◽  
Wen Yuan Mao ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Thermal Performance ◽  
Air Flow ◽  
Flow Channel ◽  
C Programming ◽  
Solar Air Collector ◽  
Trombe Wall ◽  
Collecting Efficiency ◽  
Solar Wall ◽  
The Mathematical Model

A thermal performance mathematical model of Trombe wall combined with solar air collector was established on the base of thermodynamics and fluid dynamics analysis. Then we solved the mathematical model by means of calculating program based on C programming language. The calculating results show the influence law of the area ratio of air opening to air flow channel (Ao/Af ) and the thickness of air flow channel affected on the heat collecting efficiency of solar wall. With the increasing of Ao/Af , the efficiency increases firstly, then increases more slowly, and finally comes to steady. The thickness also affects the efficiency in the same way. Though the results still need a further validation by experiments, they are initially proved correct by the qualitative analysis. The theoretical model can be a tool for the structural optimization of the Trombe wall combined with solar air collector.

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