Numerical and experimental investigations on

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International Journal of Advanced Research Trends in Engineering and Technology (IJARTET) Vol. 4, Issue 3, March 2017

Numerical and Experimental Investigations on the Performance of PEM Fuel Cell with Different Intake Models in Perforated Flow Fields Shanmugasundaram Subramaniam 1, Gukan Rajaram 2, Sugit Samaraj.C 3 Research Scholar, Department of Mechanical Engineering, PSG College of Technology, Coimbatore, India 1 Associate Professor, Department of Mechanical Engineering, PSG College of Technology, Coimbatore, India 2 M.E. Student, Department of Mechanical Engineering, PSG College of Technology, Coimbatore, India 3

Abstract: In proton exchange membrane fuel cell, the design of flow channel is one of the important factors that influence its performance. Here in this work, the performance of a single cell PEMFC with active area of 25cm2 has been evaluated both numerically and experimentally with respect to perforated and serpentine flow channel design. When considering the perforated flow field design, for the reactant gases to enter two different intake models are developed - one with front intake and the other with intake from the side. Using Flow Simulation module in the Solid Works 10.0, analysis has been carried out with respect to flow distribution and pressure distribution for the front and side intake model of the perforated flow field design and from the results obtained perforated design with side intake shows better performance. The results are also experimentally investigated and obtained similar performance results with perforated channel with side intake showing the maximum power density of 0.319 W/cm2 whereas perforated flow channel with front intake and serpentine channel gave 0.298 W/cm2 and 0.283 W/cm2 respectively. The performance increase in perforated design is due to the radial seepage of reactants through the gas diffusion layer (GDL) which indirectly increases the area of contact for the gases over the GDL. Keywords: Perforated flow field, Gas diffusion layer, Flow simulation module, Radial seepage.

I. INTRODUCTION A fuel cell is like a battery which generates electricity by converting chemical energy into electrical energy. In battery, energy is stored in it which is discharged when it is used and once the energy is completely depleted, the battery is thrown away or recharged with the help of an external electricity supply to promote the electrochemical reaction in the reverse direction.

A fuel cell, on the other hand, uses external supply of chemical energy and can run as long as it is supplied with a fuel source. The fuel depends on the type of fuel cell.

Whatever may be the case, the oxidation of hydrogen takes place electrochemically. Fuel cells can vary its size from tiny devices to large power plants producing few watts to megawatts of electricity production. All fuel cells are based on a universal design, using two electrodes separated by an electrolyte which may be solid or liquid that transports

electrically charged particles through them. A catalyst is used often to speed up the redox reaction at the electrodes.

The classification of the fuel cells is made according to the nature of the electrolyte used. The available types of fuel cell are direct methanol fuel cell, polymer electrolyte membrane fuel cell, alkaline fuel cell, phosphoric acid fuel cell, molten carbonate fuel cell and solid oxide fuel cell.

Each fuel cell has its uniqueness and is used in different applications based on the requirements.

For using the fuel cells at transport applications, the temperature should not go more than 100°C. For this case, the apt fuel cell is the polymer electrolyte membrane fuel cell. Internal Combustion (IC) engines are expected to provide 30% of useful energy conversion whereas 60 % energy conversion is possible with the help of fuel cells.

This is because of no moving parts in case of fuel cells. In addition to that, fuel cells are eco-friendly and are a boon to the society as they are completely green to the environment.

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International Journal of Advanced Research Trends in Engineering and Technology (IJARTET) Vol. 4, Issue 3, March 2017

In The PEMFC performance depends on various operating and geometric parameters like operating temperature, relative pressure, flow rate of the reactant gases, gas diffusion layer (GDL) porosity and thickness and flow channel design [1,2]. Of all these parameters, the design of flow channel has the greater impact on the performance [2,3]. In order to increase the performance of the PEM fuel cell, proper knowledge of the mechanism that lead to performance loss such as non-uniform concentration, high ionic resistance due to dry membrane, or high diffusive resistance due to the flooding on the cathode is necessary [4]. So far numerous studies have been carried out in the aspect of flow field designs like parallel, serpentine, interdigitated, perforated, spiral and pin type. Among all known designs serpentine flow channel is widely used due to its better water transporting characteristics and providing proper spread out of gases leading to effective utilization of MEA area [5]. In this work along with the serpentine channel design, the performance of the perforated flow field design is evaluated with some alterations in the intake path.

In the recent years, numerical modeling and experimentations are the effective tools in optimizing the design of fuel cell system. All these models compute the flow field along a single channel thereby studying the reaction species and current density distributions.

Shou-Shing Hsieh et al.[6] studied the effect of perforated and serpentine flow field designs on a micro scale PEM fuel cell with active area of 1cm x 1cm. They evaluated the performance of PEMFC, by trying out different configurations between serpentine and perforated channel designs on anode and cathode flow plates (serpentine/perforated, serpentine/serpentine and perforated/perforated) and concluded that perforated flow channel on anode side performs better with higher energy efficiencies. Serpentine flow channel has the advantage of good water removal capability and the disadvantage is that due to the too narrow passage design the reactant flow in them is not much easier to move around. Xuefeng Su et al.

[7] used perforated plate design on an open area to study the effect of gas holdup in rayon fibre suspensions. They concluded that on the perforated design by having holes of 1mm diameter the flow is found to be homogeneous under various flow conditions. This similar design of having 1mm perforation is followed in this work so as to have uniform pressure distribution.

Yi et al. [8] developed a novel design in PEMFC stack, by having perforated bipolar plates in place of conventional bipolar plates as it was found lighter in weight. It has been reported that, perforated plates have the tendency for

revamping manufacturability and reduction in cost [9].

Usually there exists contact resistance between the flow plate and the gas diffusion layer [10] and herein to reduce the impact of contact resistance on cell performance, the surface roughness of the graphite plate is made smooth.

Shahram Karimi et al. [11] have studied the behaviour of metallic flow plates for PEM fuel cells and concluded that the metallic plates offer higher strength, electrical conductivity, better formability and manufacturability, lower gas permeability, and better shock resistance than the graphite plates. Yue Hung [12] studied the effect of terminal design and flow plate material on PEM fuel cell performance. They suggested that the metallic plates undergo oxidation with the gases and result in membrane poisoning. To prevent this, gold plating or some other inert metal coating is provided to the metal plates. The current collector used here are gold plated so as to avoid this effect significantly.

Three dimensional flow field models aid in parametric study of a realistic flow field, current and concentration distributions. M. Zeroual [13] performed a numerical study to determine the effect of inlet pressure and height of gas channel on the distribution and consumption of gases for a PEM fuel cell. They have concluded that the channel with minimal height is expected to have more reagent consumption than that of the channel provided with more height.

II. EXPERIMENTAL SETUP To investigate the cell performance Biologic FCT - 50S test station is used as shown in Fig.1. High purity hydrogen (99.99%) and medical grade oxygen are used as fuel and oxidant respectively.

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Fig.1. Fuel cell Test Station

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International Journal of Advanced Research Trends in Engineering and Technology (IJARTET) Vol. 4, Issue 3, March 2017

For MEA preparation (Membrane Electrode Assembly), collector plates on either sides held tightly together Nafion 117 membrane is sandwiched between two gas providing no room for leakage of gases. It should be rigid diffusion electrodes (GDE) of size 5 cm x 5 cm loaded with enough to withstand the clamping force. The end plates used 0.5 mg/cm2 of 40% Pt/C as catalyst and hot pressed them at 130°C with a pressure of 60 kg/cm2 for 3 minutes is shown in Fig.2.

Fig. 2. Membrane Electrode Assembly

The membrane is conditioned to activate the majority of catalyst sites for achieving maximum performance. The H 2 and O2 flow rate are maintained at 500 ml/min and 250 ml/min respectively. The cell temperature is maintained at 40°C since the single cell performs better in between 35°C to 50°C [14]. The humidification temperatures are kept at 70°C and 60°C for H2 and O2 respectively. The test station is interfaced with a computer by means of FC-Lab V5.22 software. Various configurations of experiments are available to study the cell performance. Usually current scan and voltage pulse experiments are preferred to obtain the performance curve.

III. DESIGN OF PERFORATED FLOW FIELD PLATE, END PLATE AND CURRENT COLLECTOR PLATE Fig.3 (a) and (b) shows the channel designs serpentine and perforated being machined on individual graphite plates for the active area of 25cm2. In the fabrication of perforated design, holes of 2 mm diameter are drilled on the plate with 2 mm spacing between the holes. On the entire active area of 25 cm2 (5cm x 5cm), total of 169 holes are made consisting of 13 holes in each row and column. The reactant gas tends to flow through the perforated holes simultaneously to reach the reaction sites. The serpentine channel has a width of 2 mm, depth of 2 mm and land width of 2 mm.

The end plate is the one which will be placed at both the ends of the fuel cell and it will have a wide flange provided with bolt holes for clamping, so that the membrane electrode assembly is sandwiched between flow plates and current

Fig. 3. (a) Serpentine flow field (b) Perforated flow field

for both the designs are of the same size (11 cm x 11 cm x 1.5 cm) and material (aluminium). Fig. 4 (a) and (b) shows the end plates used for serpentine and perforated flow channel respectively. The end plate design of perforated flow channel plate differs from that of the one used in serpentine design. This end plate is designed in such a way that, the reactant gas first enters a spatial volume of 18 cm3 (6 cm x 6 cm x 0.5 cm).

Fig. 4. (a) End plates for serpentine flow field (b) End plates for perforated flow field

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International Journal of Advanced Research Trends in Engineering and Technology (IJARTET) Vol. 4, Issue 3, March 2017

Due to continuous flow of reactant gas from the source, the pressure in the constrained space gets increased and as a result the reactant gas will start to flow through the holes of the perforated flow plate and diffuses through the GDL to reach the catalyst site. End plate design for perforated flow field with front and side intake is shown in Fig. 5 (a) and (b).

Fig.6. Current collector plates for (a) serpentine flow field (b) perforated flow field

IV. RESULTS AND DISCUSSIONS A. Numerical analysis The front intake end plate and side intake end plate assembled with current collector, perforated flow field plate and MEA is shown in Fig.7 (a) and (b) respectively.

Fig.5 (a) End plate with front intake (b) End plate with side intake

The gaskets are provided between the end plate and current collector plate to avoid leakages of reactants and also functions as a separator to prevent the contact between the end plate and current collector plate. The end plate has a hole of 6 mm diameter with a depth of 75 mm on the side face for inserting the heating element to maintain the cell temperature. The locating pin holes of diameter 3 mm are drilled on the end plates to align and assemble the cell. The inner face of the end plate is completely laminated with an insulating sheet to prevent short circuit and also to avoid the surface from getting oxidized (since the reactant gas contains moisture). The current collector plates used for serpentine and perforated flow channel are shown in Fig. 6 (a) and (b) respectively.

Fig.7. Assembled view of (a) Front intake system (b) Side intake system

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International Journal of Advanced Research Trends in Engineering and Technology (IJARTET) Vol. 4, Issue 3, March 2017

The flow and pressure distribution analysis is carried out by having the following parameters: inlet mass flow rate of 500 ml/min, the hydrogen and oxygen outlet pressure at atmospheric pressure. In the front intake model, only the nearby holes are effective; the distant holes from the inlet showed reduced hydrogen consumption which can be observed in Fig.8 (a) and (b).

Whereas when tried with the inlet provided at the side, the flow of reactants and pressure distribution is better and found to be more circulating before it takes the outlet as shown in Fig. 9 (a) and (b).

B. Experimental analysis Fig.10 shows the V-I and P-I curves for the three different flow channel designs. The peak performance with maximum power density of 0.319 W/cm2 and maximum current density of 0.892 A/cm2 was obtained for perforated flow field with side intake. Similarly for the perforated flow field (front intake) and serpentine flow field, the maximum power densities and current densities obtained were 0.298 W/cm2, 0.855 A/cm2 and 0.283 W/cm2, 0.728 A/cm2 respectively.

The peak values of power and current densities for the above three flow field designs are compared in Table. 1. It is evident that, the perforated flow field with side intake shows 12.7 % and 7 % increase in peak power densities when compared with serpentine and perforated flow field with front inlet respectively.

Fig.8. Front intake model (a) Flow distribution (b) Pressure distribution

Fig. 10. V-I and P-I curve for Serpentine, Perforated (front intake) and Perforated (side intake) flow fields

The reason for side intake system performing well can be clearly viewed from Fig.9 (b) which shows the uniform flow and pressure distribution of reactants throughout the active area of the flow field. This in turn will increase the electrochemical reactions and power output of the PEMFC.

Fig.9. Side intake model (a) Flow distribution (b) Pressure distribution

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International Journal of Advanced Research Trends in Engineering and Technology (IJARTET) Vol. 4, Issue 3, March 2017 TABLE 1. Comparison of peak power and current densities for perforated flow field (side intake), perforated flow field (front intake) and serpentine flow field.

Type of field Serpentine flow field Perforated flow field with front intake Perforated flow field with side intake

Peak power density (W/cm2)

Peak current density (A/cm2)

0.283

0.728

0.298

0.855

0.319

0.892

Enhancement in PEMFC,” International Journal of Hydrogen Energy, vol. 40, pp. 4641-4648, 2015.

[4].

J. Nattawut and K. Yottana, “Effects of difference flow channel designs on proton exchange membrane fuel cell using 3-D model,” Energy Procedia, vol. 9, pp. 326-37, 2011.

[5].

Hong Liu, Peiwen Li, Daniel Juarez-Robles, Kai Wang and Abel Hernandez-Guerrero, “Experimental study and comparison of various designs of gas flow fields to PEM fuel cells and cell stack performance,” Frontiers in Energy Research, vol. 2, pp. 2296-598X, 2014.

[6].

Shou-Shing Hsieh and Yih-Wen Su, “Effects of anode and cathode perforated flow field plates on proton exchange membrane fuel cell performance,” International Journal of Energy Research, vol. 38, pp.

944-953, 2014.

[7].

Xuefeng Su and Theodore J. Heindel, “Effect of Perforated Plate Open Area on Gas Holdup in Rayon Fiber Suspensions,” Journal of Fluids Engineering, vol. 127, pp. 816-823, 2005.

[8].

Yi PY, Peng LF, Lai XM, Liu DA and Ni J, “A novel design of wave-like PEMFC stack with undulate MEAs and perforated bipolar plates,” Fuel Cells, vol. 10, pp. 111–117, 2010.

[9].

Virk MS, Mustafa MY and Holdo AE, “Numerical analyses of a PEM fuel cell’s performance having a perforated type gas flow distributor,” International Journal of Multiphysics, vol. 3, pp. 347– 360, 2009.

V. C

V. CONCLUSION The implementation of perforated flow plates for uniform flow distribution is adopted for a PEM fuel cell design. Two different intake models for the perforated flow channel design are developed and analyzed using Solid Works 10.0. The first model with front intake and second model with side intake is analyzed for flow and pressure distribution. The flow and pressure distribution is found to be better in the side intake model when compared with front intake model. The performance enhancement studies on 25 cm2 PEMFC with various flow field designs, namely serpentine, perforated with front inlet and perforated with side inlet were conducted. From the studies on serpentine, perforated (front intake) and perforated (side intake) flow fields, the perforated flow field with side intake showed better performance of 12.7 % and 7 % increase in peak power densities when compared with serpentine and perforated flow field with front inlet respectively. This is because of uniform spread of reactants and uniform reactions throughout the active area of the PEMFC.

[10]. Y. Zhou, G. Lin, A.J. Shih and S.J. Hu, “A micro-scale model for predicting contact resistance between bipolar plate and gas diffusion layer in PEM fuel cell,” Journal of Power Sources, vol. 163, pp. 77783, 2007.

[11]. Shahram Karimi, Norman Fraser, Bronwyn Roberts, and Frank R. Foulkes, “A Review of metallic bipolar plates for proton exchange membrane fuel cells: Materials and fabrication methods,” Advances in Materials Science and Engineering, article ID 828070, pp. 1-22, 2012.

[12]. Yue Hung, Hazem Tawfik and Devinder Mahajan, “Effect of Terminal Design and bipolar plate material on PEM fuel cell performance,” Smart Grid and Renewable Energy, vol. 4, pp. 43-47, 2013.

ACKNOWLEDGMENT [13]. M. Zeroual, S. Belkacem Bouzida , H. Benmoussa and H. Bouguettaia, “Numerical study of the effect of the inlet pressure and The authors would like to thank the management of PSG the height of gas channel on the distribution and consumption of College of Technology, Coimbatore, India for necessary reagents in a fuel cell (PEMFC),” Energy Procedia, vol. 18, pp. 205facilities extended to carry out this work.

214, 2012.

[14]. P. Karthikeyan, P. Velmurugan, Abby Joseph George, R. Ram Kumar and R.J. Vasanth, “Experimental investigation on scaling and Xiao-Zi Yuan, Haijiang Wang, PEM Fuel Cell Fundamentals, stacking up of proton exchange membrane fuel cells,” International Springer-London, 2008.

Journal of Hydrogen Energy, vol. 39, pp. 11186-11195, 2014.

REFERENCES

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[2].

[3].

S. Shanmugasundaram, Gukan Rajaram, P.Karthikeyan and R.J. Vasanth, “Comparison of perforated and serpentine flow channel plates on the performance of proton exchange membrane fuel cell,” Journal of the Energy Institute, in press.

P. Karthikeyan, R.J. Vasanth and M. Muthukumar, “Experimental Investigation on Uniform and Zigzag Positioned Porous Inserts on the Rib surface of Cathode Flow Channel for Performance

BIOGRAPHY S.Shanmugasundaram is a Ph.D research scholar in the Deparment of Mechanical Engineering, PSG College of Technology,

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Coimbatore, India. He received his B.E degree from Institute of Road and Transport Technology, Erode and M.Tech. degree from Anna University, Coimbatore. He has published one research paper in international journal. His current research includes development of flow fields, stack design and embedded system to control the stack voltage for Proton Exchange Membrane fuel cell to enhance its performance.

He is a life member in Instituions of Engineers (India).

Dr.Gukan Rajaram is an Associate Professor in the Deparment of Mechanical Engineering, PSG College of Technology, Coimbatore, India. He received his B.E. degree from Madurai Kamaraj University, India, in the year 1996. He completed his M.S. degree at Indian Institute of Technology Madras, India, in the year 2001. He also received his Ph.D. and PDF from North Carolina A & T State University. His research interest includes Solid oxide fuel cells, PEM fuel cells, Materials processing, Design of Experiments, Nano materials, Powder metallurgy. He has four International Journal publications, seventeen peer-reviewed International conference publications and thirteen conference proceeding and presentations He has fifteen years of research experience in fuel cell materials, materials processing, characterization and ten years of classroom teaching experience. He has organized three national level conferences and two workshops. He received three sponsored projects from DST for a worth of Rs. 84 lakhs.

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