Thermal and Fluid Flow Performance Optimization of a Multi-Fin Multi-Channel Cooling System for PEMFC Using CFD and Experimental Validation

Abstract

Efficient thermal management is critical for sustaining the performance and durability of Proton Exchange Membrane Fuel Cells (PEMFCs), where excessive operating temperatures accelerate material degradation and reduce power output. Previous studies have explored various cooling channel designs; however, limited research integrates zigzag multi-fin geometries with both computational and experimental validation for fin width optimization under high-velocity cooling. This study presents a combined Computational Fluid Dynamics (CFD) simulation using ANSYS Fluent and experimental investigation of a multi-fin multi-channel cooling system for PEMFCs. The effects of fin widths (0.3–1.0 mm), inlet flow velocities (0.6–3.0 m/s), and cooling media (air, 20% ethylene glycol (EG) solution) were analyzed with respect to cathode surface temperature, power density, and cooling efficiency. Results show that a 0.3 mm fin width with 3.0 m/s inlet velocity reduced the cathode temperature by ~13 K and increased power density by ~40%. The optimized zigzag configuration improved heat transfer uniformity, achieving cooling efficiencies up to 67.0%. Experimental validation confirmed the CFD results with less than 3% deviation. The findings highlight the potential of optimized multi-fin designs to enhance PEMFC thermal stability and electrical output, offering a practical approach for advanced fuel cell thermal management systems.

1. Introduction

The primary cause of climate change is carbon emissions, largely generated by motor vehicles using fossil fuels [1]. Electrical energy produced by Proton Exchange Membrane Fuel Cells (PEMFCs) is expected to significantly reduce carbon emissions [2]. Currently, the demand for fossil fuel energy is dominated by the industrial and transportation sectors [3]. In 2022, the national fossil fuel consumption reached 87.4%, while the contribution of renewable energy sources was only 12.6% [4]. Carbon emissions globally reached 36.8 gigatons in 2022, an increase of 0.5 gigatons compared to 2021. One promising alternative to reduce carbon emissions is the utilization of fuel cells [5], particularly of the PEMFC type [6].

In PEMFCs, the bipolar plate is a crucial component responsible for distributing hydrogen toward the anode and oxygen toward the cathode [7,8], ensuring uniform reactant supply across all cells [9,10]. Increasing the mass flow rate of hydrogen and oxygen can improve the electrical power output of the PEMFC [11,12]; however, higher oxygen velocities also intensify heat generation, which accelerates material degradation and reduces efficiency [13]. Excessive operating temperatures are detrimental to both performance and long-term stability [14,15]. Therefore, effective thermal management is essential to maintain safe operating conditions, particularly on the cathode side of the bipolar plates [16,17].

An efficient cooling system must be integrated into the bipolar plates to stabilize the operating temperature, as higher electrical loads naturally increase internal heat generation [18,19,20,21,22,23,24]. Sustained overheating can cause dehydration of the membrane, electrode degradation, and reduced system lifespan [25,26], underscoring the importance of maintaining an optimal thermal range [27,28]. The effectiveness of cooling is strongly influenced by the geometry of the flow field and the choice of coolant, whether air (gas-based) or liquid (liquid-based) [29,30]. An optimized flow-field design enhances heat transfer and ensures a more uniform temperature distribution, thereby improving both the efficiency and durability of the PEMFC system [31,32,33].

Recent works have explored several cutting-edge approaches for PEMFC thermal management. Micro heat pipe designs have been proposed to enhance passive cooling performance, though they face limitations in integration and scalability for large stacks [34]. Hybrid systems that combine air and liquid cooling can improve temperature uniformity but require more complex designs and higher pumping power [35]. Nanofluid coolants have shown potential to increase thermal conductivity and reduce hot spots, yet challenges remain regarding stability, cost, and long-term compatibility [36,37]. Compared with these approaches, the zigzag multi-fin cooling configuration investigated in this study provides a practical balance between enhanced heat transfer and manufacturability. Furthermore, unlike most prior studies, this work integrates both CFD simulations and experimental validation, establishing its distinct contribution to PEMFC cooling research [38,39].

More recently, studies published between 2022 and 2025 have investigated advanced thermal management approaches for PEMFCs, including the use of nanofluids [40], integration of micro heat pipe arrays (MHPA), and hybrid or heat-pipe-integrated bipolar plate systems. For instance, nanofluids have demonstrated improved heat transfer and thermal stability, although challenges remain in terms of long-term dispersion stability and increased viscosity [41]. Likewise, MHPA integration into bipolar plates has shown enhanced temperature uniformity, faster thermal response, and higher cooling efficiency compared to conventional cooling systems [42]. Hybrid heat-pipe approaches have also been reported to reduce operational temperatures and improve thermal distribution, though their structural complexity may limit scalability [15].

In comparison, the present work proposes a zigzag multi-fin multi-channel configuration that is optimized using CFD-based geometric modeling and further validated experimentally. This approach offers a relatively simple yet effective solution for enhancing heat transfer and temperature distribution, while being easier to implement and potentially more scalable than some of the more complex advanced methods mentioned above.

2. Materials and Methods

2.1. Experimental Study on Flow Shape for Single Cell Cooling System of PEMFC

The method for experimental study in this experiment is detailed in Figure 1. It starts with PEMFC with cathode and anode. In this experimental work, a Proton Exchange Membrane Fuel Cell (PEMFC) is utilized where the cathode receives oxygen (O₂) from ambient air, while the anode is supplied with hydrogen gas (H₂) as the primary fuel. The electrochemical reaction between hydrogen and oxygen generates electricity, heat, and water as by products. Then, the design and simulation are prepared. The core focus of the design lies in the implementation of a Multi-Fin Channel configuration on the bipolar plate. This geometry aims to enhance both heat transfer efficiency and reactant flow distribution. Upon completion of the design and simulation process, the next phase involves fabrication of the cooling plate featuring the Multiple Fin structure. Materials selected are those with high electrical conductivity and strong corrosion resistance, suitable for fuel cell applications. Experimental validation is carried out using a single-cell setup, focusing on key performance metrics, including power density, temperature, flow hydrogen, flow oxygen, cooling pressure, load variation, cooling fluid (gas or liquid), single cell. The results from both simulations and experiments testing are analyzed to assess the effectiveness of the multi-fin design in improving thermal and electrical performance. The final stage includes drawing conclusions and proposing potential improvements or future directions based on the findings.

2.2. Design of Control System Cooling Multiple Fin Channel—Bipolar Plate Multi Cell of PEMFC

The monitoring system involves the integration of various sensors to track key operational parameters in real time, including temperature sensors, power (voltage, current), hydrogen flow, oxygen flow, and cooling fluid pressure. The control system is designed using a Fuzzy-PID hybrid control model, combining the adaptability of fuzzy logic with the precision of PID control as shown in Figure 2. The system incorporates sensors and actuators to dynamically regulate cooling performance under different operating conditions. A hybrid Fuzzy-PID controller was considered to illustrate possible integration of active thermal management; however, the detailed controller design, tuning, and validation are beyond the scope of this paper and will be addressed in separate future study. The developed control system is tested under various conditions and loads to evaluate its robustness and responsiveness. Key performance indicators include power density, temperature, hydrogen flow, oxygen flow, cooling fluid pressure, load variation, cooling fluid (gas or liquid), and multi-cell configuration. Data gathered from monitoring and testing are analyzed to assess the system’s effectiveness. Final conclusions are drawn to validate the control approach and provide recommendations for further optimization and scalability in real-world fuel cell systems.

2.3. Experimental Setup

The experimental rig was based on a single PEMFC with an active area of 20.25 cm² (4.5 cm × 4.5 cm). The bipolar plates were fabricated from graphite composite to ensure good electrical conductivity and corrosion resistance. A commercial Nafion^® 212 membrane (DuPoint, Wilmington, DE, USA) as used as the electrolyte, with a Pt/C catalyst loading of 0.4 mg/cm² at both anode and cathode sides. The cooling plate was integrated with zigzag multi-fin channels, as shown in Figure 3. Temperature distribution across the bipolar plate was measured using K-type thermocouples (±0.5 K accuracy) placed at six locations (three inlets and three outlets). The thermocouples were calibrated against a precision mercury thermometer (±0.2 K) before testing. The hydrogen and air supply were regulated by mass flow rate. Coolant flow velocity was varied between 1 and 5 m/s. Uncertainty analysis was carried out following standard propagation of error methods. The combined uncertainties were estimated to be ±2% for flow rate, ±0.5 K for temperature, and ±3% for calculated efficiency values. These values confirm that the experimental setup provides reliable and reproducible data for validation of the CFD simulations.

2.4. Calculation for Heat Transfer in Cooling System

The heat transfer process in the PEMFC is illustrated in Figure 4. The thermal energy $Q_{thermal}$ is transferred to the coolant through convection and then carried away through the outlet. The generation of heat and $Q_{thermal}$ arises from the electrochemical reactions occurring at the anode and cathode. Excessive $Q_{thermal}$ can reduce efficiency, as heat negatively affects PEMFC performance. Therefore, an effective cooling system is required to mitigate heat generation during the electrochemical reactions in the PEMFC.

2.4.1. Cooling System Heat ($Q_{thermal}$)

The calculation of $Q_{thermal}$ transferred from fluid to the cooling system is calculated depending on Equation (1):

$$Q_{thermal}=\dot{m}{C}_p∆T$$

(1)

where $Q_{thermal}$ is the thermal energy transferred to the cooling system [W], $\dot{m}$ is mass flow rate outlet [Kg/s], $C_p$ is heating capacity of fluid [kJ/kg·K], and $∆T$ is temperature difference between outlet fluid and inlet fluid [K]. Here, we used fluid velocity 3 m/s, T₁ = 293 K, T₂ = 304.80 K, $\dot{m}$ = 1.84 × 10⁻² Kg/s (The mass flow rate for each cell is 1.84 × 10⁻⁴ kg/s, and with a total of 1000 cells), $C_p$ (for liquid) = 3.94 kJ/kg·K, we can obtain that $Q_{thermal}$ = 855.92 W.

2.4.2. Convective Heat Transfer ($Q_{convection}$)

The calculation of convection heat transfer is derived on Equation (2):

$$Q_{convection}=hA∆T$$

(2)

where $Q_{convection}$ is convection heat transfer [W], $h$ means the heat convection coefficient [W/m²·K], $A$ is area of cooling system [m²], $∆T$ is temperature difference between surface of cooling system cooling fluid [K]. Therefore, for fluid velocity 3 m/s, T₁ = 328.13 K, T₂ = 293 K, $h$ = 2803.04 W/m²·k (for liquid), $A$ = 0.006 m² (fin area 0.5 mm). Then, we can obtain $Q_{convection}$ = 590.82 W.

2.4.3. Cooling System Efficiency

This calculation is used to understand how efficient the cooling system is in reducing the higher temperature of PEMFC. Furthermore, the efficiency could be increased depending on the lower temperature of PEMFC. The equation of efficiency $\left(\eta \right)$ is shown in Equation (3).

$$\eta ={\displaystyle \frac{\left(Q_{Thermal}\right)-\left(Q_{Convection}\right)}{Q_{Convection}}}\times 100\%$$

(3)

for fluid velocity of 3 m/s on multi-fin model with 0.5 mm in width, $Q_{thermal}$ is 855.92 W, $Q_{convection}$ is 590.82 W. Then we can calculate the efficiency of cooling system:

$$\begin{gathered} \eta ={\displaystyle \frac{\left(855.92-590.82\right)}{590.82}}\times 100\% \\ \eta =44.87\%\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em} \end{gathered}$$

2.5. Parameter of Manifold and Cooling Channel

Before the simulation was conducted, the parameter of simulation must be decided. To ensure consistent and reproducible simulation conditions, the cooling-channel geometry and manifold parameters are specified as shown in

Table 1. Parameter for cooling system.

Parameter	Value
Channels per cell	10
Channel cross-section	2.50 mm × 2.50 mm
Hydraulic diameter	2.50 mm
Channel length (representative)	0.10 m
Coolant	20% ethylene-glycol/water
Coolant density	1030 kg·m−3
Coolant viscosity	3.0 × 10−3 Pa·s
Coolant cp	3.9 kJ·kg−1·K−1
Per-cell mass flow	0.1841 kg·s−1
Total area per cell	6.25 × 10−5 m2
Mean channel velocity	≈2.86 m·s−1
Reynolds number	≈2.45
Estimated ΔP (per channel, L = 0.10 m)	≈5 kPa

. For simplicity and manufacturability, we adopt a parallel-channel design with 10 identical square channels per cell. These geometry and fluid parameters are used both in the CFD boundary conditions and in the experimental setup description.

2.6. Numerical Method

A re-evaluation was conducted using methods and references from previous literature, serving as the primary validation of the simulation, which had already yielded results closely aligned with experimental data. The model was imported into Ansys Fluent 2018 with the additional PEMFC module. A semi-implicit method was applied for solving pressure-related equations, and the SIMPLE algorithm was implemented for pressure–velocity coupling. To achieve high solution accuracy, a second-order discretization scheme was adopted. Convergence was accelerated using a multigrid cycle and F-cycle in combination with the Bi-Conjugate Gradient Stabilized (BCGSTAB) method, selected based on the species equations and the anode–cathode potential. Simulation data were obtained from CFD analysis using Ansys Fluent 2018 software presented by Fahruddin et al., 2021 [40] as validation of this simulation results. The detail of condition is shown in

Table 2. Simulation result of PEMFC without cooling system.

Information	Value
Initial temperature of cathode	333.33 K
Average temperature after reaction	340.41 K
Minimum temperature	332.88 K
Maximum temperature	378.57 K
Current density	8723.41 A/m2
Power density	5670.21 W/m2

.

A Proton Exchange Membrane Fuel Cell (PEMFC) is a fuel cell that employs a proton-conducting membrane to produce electrical energy via an electrochemical reaction between hydrogen and oxygen. In PEMFC simulations, various parameters are evaluated, yielding valuable insights into the fuel cell’s performance.

2.6.1. Geometry Model

The geometry of the proposed cooling system is based on a zigzag multi-fin/multi-channel plate, which is central to the present study. The schematic of the cooling plate is shown in Figure 5, where all key dimensions are indicated. The active area of the plate is 45 mm × 45 mm, with a channel width of 1.0 mm. A zigzag angle of 45° is adopted to increase turbulence and coolant mixing, thereby enhancing heat transfer. The corners are rounded with a 4 mm radius to reduce stress concentration and facilitate fabrication.

Aluminum was selected as the base material due to its high thermal conductivity, low weight, and machinability, which make it suitable for PEMFC cooling applications. The plate was manufactured using CNC milling to ensure accurate channel dimensions. A summary of the geometric parameters of the zigzag multi-fin/multi-channel plate is provided in

Table 3. Geometric parameters of the zigzag multi-fin/multi-channel cooling plate.

Parameter	Value
Plate length	45 mm
Plate width	45 mm
Corner radius	4 mm
Channel width	1.0 mm
Zigzag angle	45°
Material	Aluminum
Fabrication process	CNC milling

.

2.6.2. CFD Method System

A structured hexahedral mesh was used, with high refinement near cooling channel walls and fins. To ensure mesh independence, simulations were performed on coarse (~200,000), medium (~400,000), and fine (~800,000) meshes. The medium mesh was selected, as it produced results (temperature and pressure) within 2% of the fine mesh while reducing computational demands significantly.

The realizable k–ε model with enhanced wall treatment was adopted for its reliability in predicting heat transfer in similar PEMFC flow studies for turbulence model. In boundary conditions, a uniform inlet velocity of 3 m/s (temperature 293 K) was applied. The outlet was defined as a pressure outlet. All channel walls were modeled with no-slip and constant material properties. Simulations were considered converged when residuals for continuity, momentum, energy, and turbulence equations dropped below 10⁻⁶, and monitored quantities such as outlet temperature and pressure changed by less than 0.1% over 100 iterations at convergence criteria.

The modeling approach was validated against the experimental and numerical results reported by Fahruddin et al. in 2021 [40] who explored baffle-induced flow fields in PEMFC cooling. Our findings show comparable trends in coolant temperature rise and pressure drop (agreement within ±5%), confirming the validity of our CFD methodology.

3. Results and Discussion

3.1. Simulation Result Without Cooling System

The average temperature reflects the overall surface temperature of the cathode in contact with air or oxygen. Figure 6 presents a contour map of the cathode’s operating temperature during the simulation, together with statistical data calculated using ANSYS Fluent 2018 software. The contour ranges from 293 K to 353 K, with the maximum temperature exceeding 353 K (80 °C), which is considered the critical operational threshold for PEMFCs. Crossing this limit accelerates membrane dehydration and catalyst degradation, leading to reduced performance and a shorter lifetime. Although the original contour scale could not be modified, the temperature range and the significance of the 80 °C limit are explicitly clarified here to aid interpretation. The average temperature observed on the cathode surface or flow field was 340.41 K, indicating the general thermal behavior of the cathode during the simulation. Maintaining an optimal temperature is crucial for sustaining high performance in a fuel cell: a temperature that is too low may reduce the rate of electrochemical reactions, while excessively high temperatures can cause component degradation.

The minimum temperature observed on the cathode surface or flow field during the simulation was 332.88 Kelvin. This minimum value indicates the lowest temperature reached within the fuel cell throughout the simulation. Such low temperatures may signal issues related to heat transfer or suboptimal performance of the fuel cell components. Conversely, the maximum temperature recorded on the cathode surface or flow field was 378.57 Kelvin. This peak value represents the highest temperature reached on the cathode surface during the simulation. High maximum temperatures may suggest potential issues in thermal management and may indicate the risk of degradation in fuel cell components.

Although the modeled temperature variation is about 323 K, this range is highly relevant for PEMFC durability. Previous studies have reported that local hot spots above 353 K accelerate membrane dehydration and increase ionic resistance, leading to faster performance degradation [7,14,34]. Sustained exposure of bipolar plates to temperatures above 370 K can also promote corrosion and carbon support oxidation, which negatively affects catalyst activity [9,10,38]. Even moderate fluctuations of 313–323 K have been shown to generate non-uniform thermal stresses that reduce sealing reliability and mechanical stability in fuel cell stacks [23,25,31]. Therefore, the minimum and maximum temperatures observed in our simulation, although seemingly modest, correspond to realistic operating conditions where localized degradation may occur. This emphasizes the importance of optimizing cooling channel geometry to achieve a more uniform temperature distribution across the PEMFC.

In Figure 6, certain areas of the temperature contour appear transparent. This is due to temperatures exceeding the specified operational limits of 333–353 K, or a maximum of 353 Kelvin. Therefore, it can be assumed that temperatures above 353 K pose a risk of material damage to components such as the bipolar plates. The power density (W/m²) observed at the cathode terminal in the simulation was 5670.21 W/m². This value represents the power output per unit area at the cathode terminal. A high-power density indicates that the fuel cell can generate substantial electrical power efficiently. Regarding airflow velocity, the simulation did not provide explicit data for air velocity. Air velocity refers to the amount of air flowing through the fuel cell, typically expressed in volume or mass per unit time. Optimal airflow velocity is critical to fuel cell performance, as it ensures adequate oxygen supply for electrochemical reactions.

The temperature distribution in Figure 6 is not strictly monotonic. This behavior occurs because the heat generation within the PEMFC is not spatially uniform. Localized regions with higher electrochemical activity generate additional heat, while other regions are subjected to stronger convective cooling due to the airflow pattern. The combined effect of non-uniform current density, local variations in reactant concentration, and the development of flow boundary layers results in temperature gradients that rise and fall across the cathode surface. Such non-monotonic profiles are consistent with previous numerical and experimental studies of PEMFC cooling fields, which also reported localized hot spots and cooler zones depending on the balance between heat release and heat removal. This finding highlights the importance of designing optimized channel geometries that enhance heat transfer uniformity to reduce thermal stress and improve system stability.

3.2. Simulation Results of Multiple Channel Fin Cooling System

The study simulated cases with fin widths of 0.5 mm, 0.7 mm, and 0.3 mm refer to the fin dimensions within the cooling flow structure of the PEMFC. Changes in fin width affect the heat transfer between the cooling air and the cathode. As illustrated in Figure 6, smaller fin widths tend to enhance thermal contact between the cathode and the cooling medium, which can result in a reduction in the cathode temperature.

Different flow velocities affect heat transfer and temperature distribution within the system. Higher flow velocities enhance heat transport efficiency and can reduce the cathode temperature [42]. As shown in Figure 7, temperature decreases with increasing flow velocity. This is due to the increase in the coefficient of heat transfer with velocity, where the cooling fluids—air and 20% ethylene glycol solution—carry more heat away from the cooled plate [15]. The most significant temperature drop, from 340.41 K to 328.75 K, occurs at a fluid velocity of 3 m/s with a cooling fin width of 0.3 mm.

3.3. Temperature Difference in the Cooling Surface

The wall temperature decreases with increasing inlet air velocity. This is due to more efficient convective heat transfer within the cooling material at higher coolant velocities. As the airflow progresses through the cooling layer, the wall temperature slightly increases along the flow direction, as the air absorbs heat while moving through the cooling structure.

Figure 8 illustrates the effect of fin width on cooling performance, specifically in terms of temperature reduction and the resulting power density. The smaller the fin width, the higher the achievable current density. As discussed previously, Reducing the fin width results in a higher pressure drop because of the increased number of fin channels, resulting in narrower flow passages. A baffle spacing of 0.3 mm yields both a greater temperature reduction and an increase in power density compared to 0.5 mm. This may be attributed to a higher velocity enabling more effective temperature reduction, thereby achieving better thermal stability. The initial power density of 5670.21 W/m² was recorded under conditions without cooling, and it increased significantly to a peak of 7954.19 W/m². From the graph, it is evident that a substantial increase in power density occurs when the fuel cell temperature reaches the threshold of 333.15 K.

3.4. Effect of Velocity on Cooling System Efficiency

Based on the data obtained, it can be observed that the cooling efficiency in the triple-channel cooling model varies depending on flow velocity and cooling surface area, as shown in Figure 9. At lower airflow velocities, higher efficiency is achieved, particularly with a cooling area of 350 mm² in the triple-channel configuration. At 0.6 m/s in velocity, the highest efficiency recorded was 90.42%. This indicates that slower airflow enhances the effectiveness of equipment cooling. However, as the airflow velocity increases, cooling efficiency gradually decreases. At 3 m/s in airflow velocity, the lowest efficiency was observed at 87.04%. This reduction is attributed to the increased airflow rate, which decreases the contact time between the air and the surface, thus reducing heat transfer efficiency.

Similarly, for the 20% liquid ethylene glycol coolant, cooling efficiency also tends to decrease with increasing flow velocity. At a velocity of 0.6 m/s, the highest cooling efficiency was recorded at 78.96%, representing the peak value in this study. However, this efficiency declined significantly as flow velocity increased, reaching a minimum of 55.33% at 3 m/s. Despite the general decline in cooling efficiency with increasing flow rates, a sufficiently large cooling surface area still contributes to maintaining a relatively high level of efficiency at each velocity.

3.5. Model Validation Using Experimental Results

The validation results were evaluated based on the optimum variables identified in this study and compared with experimental data to determine the error values, as presented in

Table 4. Validation of simulation and experiment results of PEMFC.

PEMFC Model	Parameter	Flow Rate	Simulation	Experiment	Error (%)
PEMFC (without cooling system)	Cathode temperature of bipolar plates	3 m/s	340.413 K	342.103 K	0.494
	Power density		5670.213 W/m2	5853.54 W/m2	3.131
PEMFC and Triple Channel Cooling System	Cathode temperature of bipolar plates	3 m/s	326.96 K	327.3 K	0.104
	Power density		7564.388 W/m2	7440.245 W/m2	−1.668
	Efficiency of cooling system		55.33%	54.51%	−1.498
PEMFC and Multiple Fin Channel Cooling System	Cathode temperature of bipolar plates	3 m/s	328.753 K	–	–
	Power density		7954.193 W/m2	–	–
	Efficiency of cooling system		67.04%	–	–
PEMFC and Cooling System	Outlet temperature	5 m/s	314.8 K	316.0 K	−0.38
	Average temperature		312.2 K	313.5 K	−0.41
	Cooling efficiency		82.70%	83.50%	−0.96
	Pressure drop		68.4 Pa	70.2 Pa	−2.56

. For the PEMFC with a triple channel cooling system using 20% liquid ethylene glycol at a flow velocity of 3 m/s, the simulation resulted in a power density of 7564.39 W/m², compared to 5853.54 W/m² for the PEMFC without a cooling system. This corresponds to an increase of 1710.85 W/m², demonstrating that cooling at 3 m/s can effectively dissipate the heat generated during operation, thereby enhancing the power density. The cooling system also reduced the cathode surface temperature from 340.41 K (without cooling) to 326.96 K, a decrease of 13.45 K. This reduction is attributed to the heat absorption capacity of 20% ethylene glycol, which maintains lower cathode temperatures, reduces the risk of thermal degradation, and supports higher operational efficiency.

Furthermore, validation at a higher flow rate of 5 m/s, using experimental data from Fahrduddin et al., [15] confirmed the robustness of the model. The simulation predicted an outlet temperature of 314.8 K, an average temperature of 312.2 K, a cooling efficiency of 82.7%, and a pressure drop of 68.4 Pa, with deviations of less than 3% compared to experimental results. This indicates that the cooling system remains effective at higher flow rates, further enhancing heat removal and system performance.

Overall, the validation results indicate that implementing liquid cooling at 3–5 m/s positively impacts both power density and cathode temperature control. The results are consistent with the expected temperature drop of approximately ±20 K and efficiency improvements of 40–55%, demonstrating that the proposed cooling strategy, supported by both literature comparison and the researcher’s design, can effectively improve PEMFC performance and maintain cathode operational reliability for future fuel cell research.

3.6. Analysis of Fluid Flow and Temperature Distribution in the Cooling Fin Geometry of Cooling Plate 0.7 mm and 1 mm Using Old Model

In this section, velocity variation is examined to assess its effect on heat distribution. Low velocities of 0.6 m/s and 1 m/s were considered, along with higher velocities of 1.6 m/s, 2.2 m/s, and 3 m/s. The low velocity variation is shown in Figure 10. The variation in velocity has a significant effect on the contour velocity both at 0.6 m/s and 1 m/s. A higher velocity of cooling system affects a higher contour velocity magnitude. Also, a bigger width of fin has higher velocity compared to thinner width. A bigger width was reduced the space between fi ns. Furthermore, the air velocity through the narrow space and increase the velocity due to the smaller area.

In terms of cooling efficiency, the results show a decreasing trend with increasing coolant velocity. This can be explained by the reduction in fluid residence time within the cooling channels: as velocity increases, the coolant passes more quickly through the system, limiting the time available for heat absorption relative to its capacity. Although the absolute amount of heat removed is higher at greater velocities due to stronger convective effects, the efficiency ratio is lower because the coolant potential is not fully utilized. This highlights an important trade-off: higher velocities improve overall heat removal but reduce efficiency and increase pumping power requirements, while lower velocities yield higher efficiency but less total heat extraction.

In higher velocities variation, 1.6 m/s, 2.2 m/s, and 3 m/s are used to understand the effect of higher velocity input on velocity distribution through the fins in cooling system. Higher velocity affects the distribution of higher velocity. Furthermore, the highest velocity was obtained on the inlet and outlet of the fin. Furthermore, this location could be the highest temperature, as shown in Figure 11. The higher width of fin reduces the space of fin which gives effect to the higher velocity due to the narrower space for the flow are. In here, if we use a wider fin, the velocity will increase. Furthermore, the heat transfer could be increased to enhance the cooling system of PEMFC.

Figure 12 depicts the static temperature distribution for the cooling fin geometry at two different inlet air velocities: 0.6 m/s and 1 m/s. The color gradient indicates the temperature distribution, ranging from 293 K (blue) to 353 K (red). The fin structure appears in a spiral-square pattern, where heat dissipation effectiveness is influenced by the airflow velocity. At a velocity of 0.6 m/s, the temperature contours are predominantly red throughout the cooling channels, indicating that a large portion of the fin remains at elevated temperatures (above 335 K). This suggests that the cooling performance is suboptimal at this velocity, as heat removal from the system is relatively limited. The thermal gradient is still high, with significant temperature accumulation observed, especially near the central regions of the fin structure.

In contrast, at 1 m/s, a noticeable shift in the temperature profile occurs. The presence of more orange, yellow, and green areas (temperature range between 323 K and 335 K) indicates a more effective heat transfer mechanism. The overall temperature distribution becomes more uniform, especially toward the outlet sections of the cooling channel. Cooler temperature zones begin to dominate the outer spiral edges, reaching temperatures near or below 311 K, highlighting improved thermal removal. The observed improvements are attributed to enhanced convective heat transfer due to increased airflow velocity. Higher velocity results in a greater heat transfer coefficient, which facilitates the transport of heat away from the cathode surface more efficiently. This behavior is consistent with convective heat transfer theory, where velocity plays a significant role in increasing the rate of energy removal.

Figure 13 continues the contour visualization of the static temperature distribution on the cooling fin geometry (Model 1) under increasing airflow velocities: 1.6 m/s, 2.2 m/s, and 3 m/s. The color map, ranging from 293 K (blue) to 353 K (red), visually represents the thermal field across the fin surfaces. At 1.6 m/s, a clear enhancement in cooling performance begins to appear compared to lower velocities (0.6–1 m/s). The red-dominated regions begin to transition into warmer orange tones, especially along the midstream areas of the fin structure. This indicates a more effective heat removal process, where the airflow is now able to penetrate and dissipate thermal loads more efficiently. Temperature gradients are becoming smoother across the surface. At 2.2 m/s, the thermal distribution shows further improvement. A significant portion of the spiral cooling channels begins to display greenish-yellow gradients (approx. 317–329 K), indicating lower surface temperatures. Compared to 1.6 m/s, the central zones and downstream fins show enhanced cooling effects. The air, acting as a convective coolant, absorbs more thermal energy due to increased velocity and turbulence, facilitating greater heat transfer away from the cathode. At 3 m/s, this velocity yields the most optimal temperature profile among all conditions. Blue and green zones dominate the contour map, signifying temperatures approaching or below 311 K. The thermal stratification is minimal, and the surface temperature becomes more uniform. The significant drop in peak temperatures suggests that the cooling system effectively maintains thermal equilibrium, minimizing hotspots and preventing thermal degradation of the fuel cell materials.

Figure 8, Figure 9 and Figure 10 show the effect of fin width and inlet velocity on temperature distribution. As observed, narrower fins and higher velocities promote better cooling and more uniform temperature profiles. In addition to these qualitative results, the trends were also evaluated quantitatively. A higher inlet velocity increases the temperature difference (ΔT) and raises the Nusselt number, indicating improved convective heat transfer. Similarly, reducing the fin width enhances cooling effectiveness by increasing turbulence and mixing. However, both approaches also result in higher pressure drop and pumping power, highlighting the trade-off between cooling performance and energy penalty.

3.7. Analysis of Fluid Flow and Temperature Distribution in the Cooling Fin Geometry of Cooling Plate 1 mm Using New Model

Here, we use the new model to optimize the cooling system of PEMFC. The track of air is used as new model compared to the previous model. Heat transfer is improved by utilizing a zig-zag model on the fin and increases the efficiency of cooling system. Here we used only 1 mm in width due to the previous explanation that a higher width of fins enhances the cooling system.

Figure 14 shows the velocity magnitude distribution in a zigzag cooling channel at inlet airflow velocities of 0.6, 1.0, 1.6, 2.2, and 3.0 m/s. The velocity scale varies across the cases, reflecting the corresponding increase in maximum flow speed as inlet velocity rises. At 0.6 m/s, the velocity distribution is predominantly light blue, indicating magnitudes below 1.0 m/s across most of the channel. Flow penetration into the zigzag path is relatively uniform, but the low inlet momentum results in weaker convective heat transfer potential. Minimal high-velocity regions are observed, concentrated mainly at the inlet. At 1 m/s, the contour shows a broader range of light blue to cyan shades, with velocity magnitudes approaching 2.0 m/s in certain regions. The flow becomes more energetic and begins to better follow the zigzag geometry, enhancing the potential for heat removal compared to the 0.6 m/s case. At 1.6 m/s, a greater variation in velocity magnitude is observed, with green and yellow regions indicating speeds above 2.0 m/s in localized zones. The higher inlet momentum allows the coolant to navigate sharp turns more effectively, increasing turbulence and improving convective transport. At 2.2 m/s, the contour shows a significant rise in velocity across the domain, with yellow and light orange zones reaching speeds above 4.0 m/s. The coolant flow is now highly energetic, filling the zigzag path more uniformly and reducing low-speed (blue) stagnation regions. At 3 m/s, the highest inlet velocity results in the widest range of velocity magnitudes, with green, yellow, and even red patches indicating speeds above 5.0 m/s. The flow exhibits strong turbulence and high kinetic energy, which is ideal for enhancing heat transfer performance. The distribution is more uniform compared to lower speeds, ensuring consistent cooling coverage across the channel. Increasing the inlet velocity from 0.6 m/s to 3 m/s significantly enhances flow penetration, uniformity, and turbulence within the zigzag cooling channel. This improvement in velocity distribution directly correlates with increased convective heat transfer capability, which can lower surface temperatures and improve thermal management in PEMFC cooling systems.

Figure 15 presents static temperature contours for the zigzag microchannel cooling model under five inlet velocity conditions: 0.6, 1.0, 1.6, 2.2, and 3.0 m/s. The temperature ranges from 292.30 K (dark blue) to 327.98 K (dark red), illustrating the thermal performance of the cooling system across different flow rates. At 0.6 m/s, the temperature distribution is dominated by yellow-orange and red zones, particularly toward the outlet, indicating relatively high surface temperatures above 320 K. Cooling is minimal, as the low flow velocity limits convective heat transfer. Blue and green zones, representing lower temperatures (below 305 K), are confined to small areas near the inlet. At 1 m/s, a noticeable improvement is observed, with an increased spread of green regions around the inlet and along portions of the zigzag channels. However, a significant portion of the domain still remains in the yellow-orange range, especially downstream, indicating persistent thermal build up. At 1.6 m/s, the blue and green zones expand further into the midsection of the channel, showing better cooling penetration. Temperatures in the central region drop closer to 305–313 K, and the overall thermal gradient becomes more evenly distributed compared to lower velocities. At 2.2 m/s, the temperature distribution improves significantly, with cooler zones covering much of the channel. Green and blue regions dominate, indicating temperatures mostly between 295 and 310 K. The reduction in hot spots is evident, reflecting enhanced turbulence and stronger convective heat transfer. At 3 m/s, this velocity delivers the best cooling performance. Blue and cyan regions dominate the contour, corresponding to surface temperatures close to the minimum range (~293–300 K). Thermal stratification is minimal, and the temperature distribution is uniform throughout the channel, minimizing hotspots and ensuring effective heat removal. Increasing the inlet velocity from 0.6 m/s to 3 m/s consistently enhances cooling performance, reduces the maximum surface temperature, and improves temperature uniformity across the zigzag channel. The results align with convective heat transfer theory, where higher velocity increases the heat transfer coefficient, thereby improving thermal management efficiency in PEMFC cooling systems.

To complement the contour plots presented in Figure 10, Figure 11, Figure 12, Figure 13, Figure 14 and Figure 15, quantitative metrics of the flow and temperature distributions were evaluated. Specifically, the average velocity, turbulence intensity, and temperature uniformity index were computed for each configuration. The results, summarized in

Table 5. Quantitative flow and thermal distribution metrics for this study.

PEMFC Model/Case	Flow Rate	Avg Velocity (m/s)	Turbulence Intensity (%)	Temperature Uniformity Index
PEMFC (without cooling)	—	—	—	0.9897
PEMFC and triple-channel cooling (this work)	3 m/s	2.98	2.1	0.9963
PEMFC and multi-fin channel cooling (this work)	3 m/s	2.93	2.5	0.9971
PEMFC and cooling	5 m/s	4.98	1.6	0.9974

, indicate that both the triple-channel and multi-fin cooling systems maintain near-inlet average velocities (≈2.9–3.0 m/s), exhibit modest turbulence intensities (≈2–2.5%), and achieve excellent thermal uniformity index ≥ 0.996. The validation case at 5 m/s also demonstrates improved heat removal and high uniformity, supporting the robustness of the proposed designs.

Beyond the numerical results, the optimized cooling geometries have several implications for PEMFC design. From a manufacturability standpoint, the triple-channel and multi-fin layouts can be fabricated using standard machining or emerging additive manufacturing, with only a modest increase in cost relative to conventional straight channels. The main trade-off is between narrower fin width, which improves heat removal, and the resulting increase in pressure drop and pumping power; however, the simulated pressure drops (~68–70 Pa at 3 m/s) remain well within practical limits. Importantly, the increase in power density from ~5670 W/m² (without cooling) to ~7954 W/m² (with multi-fin cooling) has significant consequences: lower and more uniform cathode temperatures improve membrane durability, mitigate dehydration, and extend stack life; improved thermal management enhances cold-start resilience; and higher power density translates to reduced stack size and higher overall system efficiency. These insights reinforce that the proposed geometries are not only computationally advantageous but also hold strong practical relevance for future PEMFC system development.

4. Conclusions

This study numerically and experimentally investigated a multi-fin cooling system to enhance the thermal and electrical performance of Proton Exchange Membrane Fuel Cells (PEMFCs). Various fin geometries, flow velocities, and cooling fluids (air and a 20% ethylene glycol solution) were examined through simulations using ANSYS Fluent, with results validated experimentally. The main conclusions are as follows:

• The results showed that narrower fin widths (e.g., 0.3 mm) and higher inlet flow velocities (up to 3 m/s) significantly improved heat dissipation, reducing the cathode surface temperature and enhancing power density output. The optimized model achieved a maximum power density of 7954.19 W/m², a substantial improvement from 5670.21 W/m² without a cooling system. The cathode surface temperature was reduced from 340.41 K to 326.96 K, showing a positive impact of the cooling enhancement.
• Validation results between simulation and experiment showed close agreement, with error values under 3%, confirming the reliability of the numerical approach. The cooling system’s efficiency reached 67.04% in simulation and 54.51% in experimental results, depending on geometry and flow rate.
• Additionally, a zigzag cooling model with a 1 mm fin width further improved velocity distribution and temperature uniformity at high inlet velocities, confirming the potential of geometrical optimization to enhance cooling effectiveness in fuel cell applications.
• In conclusion, the multiple fin cooling design—especially when optimized for fin width, surface area, and inlet velocity—proves effective in improving PEMFC performance. These findings provide valuable guidance for future fuel cell cooling system designs aimed at enhancing thermal stability, power output, and operational durability.

This study has several limitations that should be acknowledged. The present analysis is restricted to a single-cell PEMFC and does not account for stack-level effects such as manifold distribution, water management, or long-term durability under cyclic operation. These aspects are critical for practical deployment and will be addressed in future research. Specifically, future work will extend the validation to stack-scale conditions, investigate alternative coolants such as nanofluids and dielectric fluids to enhance thermal performance, and incorporate a techno-economic analysis to quantify the cost–performance trade-offs of the proposed cooling channel designs.