Temperature Uniformity Index Research Articles

Influential factors of horizontal aluminum plates on radio frequency heating behaviors in a rectangular polypropylene container of edible seeds: Thickness, surface area, air gaps, electrical and dielectric properties

In this study, the validated computer model was further applied to evaluate effects of aluminum (AL) plate thicknesses, electrical/dielectric properties, surface areas, or air gaps on RF heating behaviors in a rectangular polypropylene (PP) container. Simulated results showed that volumetric temperature uniformity index (TUI) and electric field intensity (EFI) of whole samples increased with increasing thickness of an AL plate. The lowest TUI (0.042) of the second layer was obtained when the plate area was changed to 190 × 130 mm2. A composite plate (210 × 150 × 2 mm3) composed of central part with AL plate and other part with PP plate was proposed to replace the single AL plate based on simulation results. The experimental TUI (0.063 ± 0.001) on second layer surface of watermelon seeds with inserting one composite and three AL plates was significantly lowest (P < 0.05) among those of samples with inserting four AL or composite plates.

Channel to rib width ratio effect on thermal performance of cooling plate in polymer electrolyte membrane fuel cell

AbstractEnsuring a homogeneous temperature distribution inside a polymer electrolyte membrane fuel cell stack is crucial to fuel cell performance and durability, and cooling channels are responsible for this. In this study, a three‐dimensional numerical investigation is performed on a channel to rib width ratio (CR) based on serpentine flow field design. The cooling performance of various designs having different CR values is considered and compared according to the temperature uniformity index, the temperature difference between the maximum and minimum temperature, average bottom temperature, and pressure drop between the inlet and outlet of the cooling channels. Results demonstrate that the average temperature, temperature uniformity index, temperature difference, and pressure drop decrease by about 5%, 40%, 37%, and 79%, respectively, when CR is increased from 0.33 to 3.00. More uniform temperature distribution and thus, better cooling performance is achieved for CR = 3.00, especially at low Reynolds numbers and high heat fluxes. Also, the lowest pressure drops are obtained when CR is 3.00 under all considered operating conditions.

Uniforming thermal distribution by air-convection aspirated in partially hollowed tetrahedral lattice porous cold plates for the drone battery

A pouch-type lithium-ion battery requires effective thermal management and a solution for temperature imbalances depending on its morphological characteristics. In this study, we present such a solution for rows of pouch-type lithium-ion battery cells controlled by aspirated air convection in a tetrahedral lattice porous cold plate, as well as by reducing the temperature imbalance in the lattice porous medium (LPM). The hollowness ratio (HR) was applied to the ligament, and its effect was investigated in the entrance region of the cold plate channel. A series of steady-state numerical simulations and experiments were conducted to demonstrate the effectiveness of the solution. As a result, the temperature deviation in the longitudinal direction of the LPM cold plate's lower substrate was 6.4°C under the 7 C-rate heat source condition. Owing to the inlet effect of forced convection due to the aspirated airflow, the lowest temperature was observed on the inlet side, and a higher temperature was observed on the outlet side. By applying the HR to the ligament of the LPM cold plate, it was confirmed that the temperature deviation decreased to 4.4°C, which was 2°C lower than that applied to the simple solid ligament. In addition, the temperature uniformity index (TUI) was 0.96, when the hollowness ratio was 0.64.

Technological and Engineering design of a megawatt proton exchange membrane fuel cell system

For the large-scale application of Proton Exchange Membrane Fuel Cell (PEMFC) in the generation, multi-stack PEMFCs are usually adopted to meet high-power needs. The connection method among stacks, layout parameters, and operating parameters can greatly influence the performance and uniformity of system. A megawatt (MW) class PEMFC system with 20 stacks is proposed and modeled with a flow network model, a thermal model, and a PEMFC model. The temperature and voltage uniformity index (TUF and VUF) are defined to evaluate the system uniformity among stacks. The effect of several operating parameters, such as current density and hydrogen inlet pressure, and layout parameters such as spacing distance and the diameter of the pipe, on the stack voltage, system electricity efficiency, VUF and TUF are quantitatively compared. The results show that as the current density increases, the consistency of the system output decreases. The stack with the shortest gas transmission distance shows the best performance and the frictional loss is the main factor influencing the pressure differences among the inlet pressure of stacks. Under the inlet pressure of 2.5 atm, the voltage difference among stacks is within 0.15 V. From the perspective of overall cost and system output, a pipe diameter of 25 mm is more suitable for the design of the intake pipe in this system.

Design and numerical investigation of multi-channel cooling plate for proton exchange membrane fuel cell

Proton exchange membrane fuel cells need cooling plates with strong heat exchange capacity to maintain temperature balance. In order to obtain better cooling performance, four new types of flow field distribution of cooling plate are designed, including local serpentine channel, local parallel channel and the flow field in which the four channels are symmetrically distributed along the diagonal and horizontal centerline of the cooling plate. The maximum temperature, temperature difference, temperature uniformity index and pressure drop of the multi-channel cooling plate under different working conditions are analyzed by numerical simulation. The results show that the multi-channel design can effectively enhance the heat transfer effect of the cooling plate and reduce the pressure drop. The local serpentine channel design can increase the fluidity of the coolant, avoid local reflux, make the temperature distribution more uniform and avoid local overheating. The maximum temperature of local serpentine channel flow field is 1.2 K lower than that of local parallel channel flow field. The pressure drop of internal parallel flow field design is 2.58 kPa, which is 62% lower than that the design of internal serpentine flow field. Increasing the inlet coolant flow can strengthen the heat transfer capacity of the cooling plate, when the flow rate increases from 2e-6 m3/s to 4e-6 m3/s, the maximum decrease is 8.53% of Model6. But it will increase the pressure drop of the channel with long cooling channel, the maximum pressure drop increase is 924 kPa when the inlet flow increases from 6e-6 m3/s to 8e-6 m3/s.

The study of heat-mass transfer characteristics and multi-objective optimization on electric arc furnace

It is crucial to reveal the energy conversion and heat and mass transfer characteristics in the electric arc furnaces (EAFs). In this paper, a transient mathematical model was built to adequately capture the distribution of multi-physical fields in EAF. The numerical modeling method was verified against brown corundum smelting experiment data. In addition, the influence on the brawn corundum smelting process of the typical operating parameters has been examined, and the major problems which limit the performance improvement of smelting were analyzed. Moreover, four indicators were proposed to comprehensively evaluate the EAF performance, consisting of liquid volume fraction β, energy efficiency η, temperature rise index ς, and temperature uniformity index ξ. Furthermore, the optimal combination of operating parameters was selected automatically based on the back propagation (BP) neural network predicting model and non-domestic sorting genetic algorithm II (NSGA-II). The results showed that the local overheating phenomenon is serious and that homogenizing the energy distribution in the furnace is the key to improving the melting performance. Increasing electrode immersion and voltage can significantly increase the rate of heat and mass transfer. In the case of ψ = 0.75, υ = 0.6, when χ is increased from 0.2 to 0.6, τmax is shortened by 13.3% and ηmax is increased by 12.0%. While with ψ = 0.75 and χ = 0.4, τmax is reduced by 36.0% when υ increases from 0.2 to 1.0, but ηmax is also decreased by 7.0%. It was found that decreasing the height diameter ratio will improve the overall EAF smelting performance, but it also increases the area of heat loss. In the case of χ = 0.4, υ = 0.6, ξave and ηmax improved by 3.1 and 14.5%, respectively, when ψ decreases from 1.0 to 0.5. The EAF performances are considerably enhanced in comparison to the operating basic parameters (ψ = 0.75, χ = 0.4 and υ = 0.6), subject to optimal operation parameters (ψ = 0.61, χ = 0.59 and υ = 0.59). In this case, τmax and ςmax reduced by 6.2 and 4.1%, respectively, while ηmax and ξave increased by 6.8 and 1.0%, respectively.

Modeling and optimization of turbulent flow through PEM fuel cell cooling channels filled with metal foam- a comparison of water and air cooling systems

One of the proposed methods to improve the performance of a proton exchange membrane fuel cell is using metal foam within the channels. Here, we performed a 3D numerical simulation and studied the effect of structural properties of metal foam on the system performance. Also, we used artificial neural network to predict three criteria, i.e., maximum temperature, temperature uniformity index, and pressure drop, together with Genetic Algorithm for system optimization. Obtained results indicate that using metal foam can improve the temperature uniformity in the cell, so that maximum temperature and temperature uniformity index are decreased about 1.785 K and 0.7 K, respectively, while resultant increase in overall pressure drop of the system is only about 4.4%. The same amount of maximum temperature reduction is possible by increasing the flow rate; however, this scheme puts 60% more pressure drop upon the system. Moreover, we compared the performance of air- and water-cooling systems and found that for a given pressure drop, the maximum temperature as well as temperature uniform index of an air-cooling system is lower than that of a water-cooling system, while for the same system parasitic power, a system with water coolant has more uniform temperature distribution with lower maximum temperature.

Hydrogen starvation mitigation strategies during the start-up of proton exchange membrane fuel cell stack

Hydrogen starvation during start-up loading and rapid load change is a severe threat to the life and durability of proton exchange membrane fuel cell. To mitigate and eliminate hydrogen starvation during start-up loading, a dual-path hydrogen supply strategy is proposed to improve hydrogen diffusion within the stack. Based on constant loading rate continuous loading, two optimized start-up strategies with variable loading rates are presented. Stack voltage, stack average temperature, and single-cell temperature uniformity under different start-up loading strategies are discussed in detail. Experimental results show that at the end of continuous loading with a loading rate of 0.67 A/s, the peak voltage uniformity rate of dual-path hydrogen supply mode is 12.67% lower than that of dead-ended anode mode. In start-up loading from open-circuit state (0 A) to nominal state (40 A), single-cell temperature uniformity index has a maximum reduction of 0.136 °C compared to dead-ended anode mode. Besides, the combination of dual-path hydrogen supply and gradual-decreasing loading rate eliminates voltage overshoot during start-up loading, and reduces the single-cell temperature uniformity index by a maximum of 15.8%. Results indicate that the proposed strategies can mitigate hydrogen starvation, and improve the stability of stack voltage and the temperature uniformity of single cells.

The study of heat-mass transfer characteristics and optimization on electric arc furnace with the novel fence electrode

In this paper, a fence electrode design was proposed to optimize energy allocation in the EAF. The fence electrode includes a cylindrical main electrode (M-electrode) and circular smaller cylindrical assisted electrodes (A-electrodes). Five working parameters affecting the smelting performance were determined afterward, which include the height diameter ratio ψ, electrode immersion ratio χ, main electrode voltage parameter υm, assisted electrode voltage parameter υa, and smelting time parameter τ. Furthermore, the orthogonal analysis method was used to investigate the synergetic mechanism of operating parameters on four indicators. The four indicators consisting of liquid volume fraction β, energy efficiency η, temperature rise index ς, and temperature uniformity index ξ. The optimal fence electrode electric arc furnace (F-EAF) operating parameters were then automatically given by the back propagation (BP) neural network predicting model and non-dominated sorting genetic algorithm II (NSGA-II), and compared with the optimal traditional single electrode electric arc furnace (S-EAF). The fence electrode design was finally verified by industrial experiments. The results show that the fence electrode can effectively homogenize the energy distribution and provide arc heat directly to the side zone in EAF. Increasing A-electrode voltage has a significant advantage in terms of increasing the smelting rate, but it also significantly raises the overall temperature, which is not conducive to smelting safety. In the case of ψ = 0.75 and χ = 0.4, υa increases from 0.1 to 0.3, τmax and ηmax decrease by 34.2 and 8.0%, respectively. By correlation analysis, it can be known that the A-electrode is an important factor for the F-EAF adjustment ability. Compared with the S-EAF, the F-EAF smelting performance is improved significantly. After multi-objective optimization, F-EAF τmax and ςmax reduce by 8.9 and 0.6%, respectively. At the same time, ηmax and ξave have increased by an average of 1.4 and 2.6%, respectively. The industrial experiments reveal that the fence electrode design can not only effectively homogenize the EAF energy supply, but also can overcome the shortcoming of arc deflection, making the smelting process more stable. In conclusion, F-EAF contributes to the EAF smelting performance evaluation, and this new proposal opens up novel ideas for the future development of EAF design.

Flow characteristics analysis for multi-path hydrogen supply within proton exchange membrane fuel cell stack

The flow rate distribution of hydrogen between single cells has a significant impact on the performance and durability of the entire proton exchange membrane fuel cell stack, especially for open-cathode stacks. However, few studies consider the effects of fuel distribution on output performance, pressure drop distribution, and temperature distribution simultaneously at the stack level. To investigate the effect of hydrogen distribution on the stack output characteristics, several different multi-path hydrogen supply modes are proposed and explored in this study through the combination of flow network models and experiments. Considering hydrogen reaction consumption in the calculation models. Parameters such as stack voltage, flow uniformity index, dimensionless pressure drop, and temperature uniformity index under different modes are quantitatively compared. The results show that Triple-path hydrogen supply mode has the highest stack voltage of 5.278 V at rated condition, 4% improvement over the lowest Z-shape mode. While Quad-path hydrogen supply mode has the best flow rate distribution and single-cell voltage uniformity, with a maximum voltage difference of only 0.073 V between single cells in the stack. Multi-path hydrogen supply modes provide more uniform pressure drop distribution over the conventional U and Z-shape (with a single path), but the relationship between output performance and the number of hydrogen supply paths is not simply linearly correlated. Furthermore, the whole stack temperature decreases with the increase of hydrogen supply path, but the temperature uniformity is not optimal with the maximum number of paths.

Numerical parametric study on the burner arrangement design for hydrogen production in a steam methane reformer

A numerical parametric study on the burner arrangement design for a steam methane reforming reactor was conducted under three burner configurations: a single co-axial inside burner (SCIB), a single top burner (STB), and multiple top burners (MTB). The burner combustion gas inlet angle was changed to 25°, 45°, and 90° with respect to the horizontal plane. Moreover, the number of reformer tubes inside the reactor was changed to four, six, and eight tubes arrangements. Furthermore, the models were numerically evaluated for temperature distribution inside the combustion space and hydrogen mole fraction in the reactor by incorporating the Xu and Forment model using a user-defined function (UDF). The results show that the STB configuration is preferable over the SCIB and MTB configuration due to the uniform temperature distribution inside the combustion space and efficient heating from the combustion gas. Furthermore, the standard deviation of the temperature inside the combustion space was found to be lower for the STB arrangement. Moreover, the STB configuration reported a maximum temperature uniformity index of 0.92 for the eight-tubes reformer arrangement. The value of the average wall heat transfer coefficient and wall heat flux at the reformer tube surface for STB configuration was 396.6 W/(m2K) and 21.7 W/m2, respectively. The velocity inlet angle of the burner combustion gas also plays an important role in the methane steam reforming reaction. A burner combustion gas inlet angle of 45° was observed to have better hydrogen conversion than the 25° and 90° inlet angles due to the proper mixing, leading to more effective heat transfer to the reformer tubes.

Concentrator photovoltaic thermal management using a new design of double-layer microchannel heat sink

The concentrator photovoltaic (CPV) systems commonly endure high cell temperatures, which affect their overall performance. Besides, the high cell temperature could lead to physical damages within the whole system due to the induced thermal stresses. Therefore, an efficient cooling is mandatory to achieve a higher net output power from the CPV and safe operation. The current work's main purpose is to investigate the integration of double-layered microchannel heat sink (DL-MCHS) with CPV cell as thermal management device. A three-dimensional (3D) model is presented to investigate the performance of a CPV cooled by the DL-MCHS to figure out the ability to handle the effective heat dissipation under different terrestrial conditions. The parallel flow (PF) and counter flow (CF) cooling orientations were studied. Ethanol coolant is used to cool the CPV under different concentration ratios (CR) of 5, 10, 15, and 20 suns. The results show that the temperatures remarkably decreases with the inlet flowrate is increased. The counter flow operation (CF) achieved the best temperature uniformity index (Tuni) when the coolant mass flowrate (V̇) ranged between 200 and 1200 ml/hr. Especially at CR 5 suns, the temperature uniformity index, Tuni, enhanced to 99.87% at 1200 ml/hr.

Experimental investigation on thermal management of a photovoltaic module using water-jet impingement cooling

Cooling of photovoltaic (PV) modules is investigated indoors using a multi-nozzle jet impingement cooling (JIC) system with water as the coolant. The focus is to develop extensive study on the effects of the number of nozzles, their sizes (diameter), and the dimensionless nozzle-to-PV spacing on the overall performance of the JIC system. Temperature uniformity index, a distinctive key parameter, is introduced to assess the effectiveness and desirability of the JIC system from the thermal point of view. Response Surface Methodology (RSM) is developed to determine the optimal operating conditions of the JIC system. The results reveal that the electrical efficiency of the PV module is improved by an increase in the liquid mass flow rate. The output power of the PV module is also enhanced with the number of nozzles; the reverse is true for the diameter of nozzle and the nozzle-to-PV spacing. Appropriate temperature uniformity can be achieved by an optimum design of the JIC system. The results of RSM demonstrate that the JIC system with optimum parameters not only enhances considerably the output electrical power, but also reduces the operating temperature of the PV module while keeps it uniform for each individual cell. Average surface temperature of the PV module decreases from 63.95°C to 33.68°C by using a set of optimal parameters. Maximum enhancement in the output power of the PV/JIC system is 47.67% in the optimum conditions. The best temperature uniformity is attained for the minimum nozzle-to-PV spacing 5mm, the minimum nozzle diameter 1mm and the maximum number of nozzles 24.

Computational investigation of the effect of orientation and rotation of shell egg on radio frequency heating rate and uniformity

Abstract The objective of this work was to computationally investigate radio frequency (RF) heating rate and uniformity of shell egg as affected by orientation and rotation. To do this, a multiphysics model was developed using COMSOL to simulate RF heating of a vertically oriented non-rotating shell egg. This model was experimentally validated against temperature measurements taken at three different internal locations within the egg. Simulations were then performed using the validated model with both non-rotating and rotating egg for different orientations (vertical and horizontal). Rotation of egg was incorporated into the model by rotating the RF system around the stationary egg instead of rotating the egg. Temperature-dependent material properties of the yolk, albumen and shell within a temperature range of 20 to 70 °C were used in the model. Simulated temperature uniformity index (STUI) values were calculated to evaluate the effect of orientation and rotation on heating uniformity. The results showed that heating was more uniform when shell egg was oriented horizontally rather than vertically. However, rotation did not further improve heating uniformity of the horizontally-oriented egg. Although heating uniformity was improved when the vertically-oriented egg was rotated, concentrated heating around the air cell could not be avoided.

Numerical analysis of sinusoidal and step pulse velocity effects on an impinging jet quenching process

In this paper, a numerical simulation of jet impingement quenching is provided. The VOF method in the basic solver of the OpenFOAM CFD package is developed to simulate boiling and condensation phenomena. In simulations, surface tension and mass transfer between two phases were modeled with continuous surface force (CSF) model and Lee mass transfer model, respectively, and energy equation was solved in the solid region. Numerical simulation of jet impingement quenching process is validated by experimental data and a good agreement is observed. The effects of pulsating jet velocity and step jet velocity on quenching process are studied, and parameters such as temporal and spatial variation of solid part temperature and standard temperature uniformity index (STUI) are investigated. The effects of frequency and amplitude of sinusoidal single jet and also the period of two jets with step pulse are investigated. The results revealed that using two jets with step velocity profile leads to the best performance or least uniformity index (best temperature distribution) among the considered cases. Studying the maximum temperature difference inside the solid region indicated that for pulse flows this parameter is considerably lower than the continuous flows. Also, at a constant flow rate, 43% reduction in STUI is achieved by sinusoidal pulsating jet compared to the single continuous jet, while 66% STUI reduction was reached for two-jet cases. These substantial reductions in uniformity index present these methods as promising approaches for the quenching process in various industrial applications.

Cell and stack‐level study of steady‐state and transient behaviour of temperature uniformity of open‐cathode proton exchange membrane fuel cells

The steady-state temperature uniformity and thermal transients of open-cathode proton exchange membrane fuel cell (PEMFC) at cell and stack level are researched experimentally in this study. The local temperatures are obtained by 30 thermocouples contacting the surfaces of cathode gas diffusion layers (GDL). The s temperature homogeneity under different load currents and air flow rates are investigated. The results reveal that the fluctuation of temperature distribution under different currents is small under the lowest air flow rate set in the experiments. Comparatively, the temperature is less uniform when the load current is higher under other air flow rates. The evaluation indicator, temperature uniformity index (TUI), varies nearly linearly with the current. And the maximum variation is 55.6% to 59.0%. This distinct behaviour is probably related to the existence of liquid water and its nonuniform distribution which can enlarge the temperature difference at high current. With respect to thermal transients, there is rapid deterioration in temperature uniformity when the load current is stepped up. It may arise from the uneven liquid water distribution which can lead to different temperature variation rates. Further, the research gives direction for optimization of cooling strategy and thermal management of open-cathode PEMFC stack in application.

Computer simulation modelling, evaluation and optimisation of radio frequency (RF) heating uniformity for peanut pasteurisation process

Non-uniform heating caused by uneven electromagnetic field distribution in a material is a major regulatory barrier for applying radio frequency (RF) heating in critical processes, such as pasteurisation of low moisture agricultural products. An earlier finite element model was adopted and validated to predict the temperature distribution in peanut kernels heated in a 6 kW, 27.12 MHz RF laboratory unit using 4.5 kg batches of peanut kernels. A temperature uniformity index (TUI) was used as a measure of the temperature distribution within the RF treated product load. The modelling results were used to demonstrate that the temperature distribution in RF heated peanuts could be improved by segregating samples into structured blocks with air gaps between them. The developed concept from this study can further be expanded to optimise industrial-scale RF treatment protocols for controlling microorganisms in agricultural products.

Heat transfer and uniformity enhancement in quenching process of multiple impinging jets with Newtonian and non-Newtonian quenchants

Boiling jet impingements (normally water) are being widely used in various industries such as cooling power electronic components, due to the high heat transfer rate and low cost. Also, oils and molten salts are used in single-phase quenching processes. Many studies have been carried out into this field, but most of them were experimental. A quenching jet impingement process is simulated numerically in this research. For a comprehensive solution, a solver code based on the Volume of Fluid (VOF) method was modified to analyze the effects of conjugation and mass transfer. To validate the solution, an experimental quenching process of an impinging jet was simulated in 3D, and the results showed a good agreement. In addition to the temperature uniformity of the block, the cooling rate is also important during the process. Thus, Optimized Cooling Factor (OCF) was defined to involve both features simultaneously. Subsequently, the quenching of a hot steel cubic block by four simultaneous liquid jets was simulated in 3D. Studies were conducted on the effects of parameters such as the sinusoidal inlet velocity, jets width and spaces between the jets on the Standard Temperature Uniformity Index (STUI) and OCF, for water, molten salt and non-Newtonian molten salt quenchants. Some remarkable results are achieved by the proposed configurations. The results indicated that in all cases with pulsative jets, improvements in STUI and OCF relative to constant-velocity ones were observed and optimal STUI and OCF factors were accessible in lower values of the jet-flow frequency. Furthermore, by changing the quenchant from molten salt to non-Newtonian molten salt, the STUI and OCF plot averages enhanced from 0.1 to 0.085 and 4.8 to 6.5, respectively. Comparing the water and non-Newtonian molten salt from required input energy and pumping power points of view revealed that the input heat for non-Newtonian molten salt in all cases changes in the range of 2600–8200 J, while the input heat for water jet equals to zero, and the power needed to pump the water is almost 40–45% less than the needed pumping power of the non-Newtonian molten salt, on average.

Metal foam as a turbulent flow distributor in the cooling channels of a PEM fuel cell—a numerical study

Operating temperature is one of the most important parameters affecting the performance of polymer electrolyte membrane (PEM) fuel cells. The cooling system of a PEM fuel cell maintains the temperature of the fuel cell stack at a specific value and removes the heat generated in the cell. This paper presents 3D numerical simulation of a water-cooled PEM fuel cell cooling system, with a metal foam insert instead of traditional cooling channels. We explore the possibility of using metal foams for thermal management of fuel cells. We consider the turbulent flow of the coolant through the porous medium and investigate the effect of metal foam properties, including porosity and pore size, on the performance of the cooling system. The Brinkman–Darcy–Forchheimer equation is employed to analyze the flow field in the porous medium and the k − ε model is utilized for turbulence studies. The numerical results indicate that, at a specific Reynolds number, by increasing the porosity and the pore size of the metal foam, the pressure drop decreases, while the maximum temperature difference occurs in the cooling plate. The temperature uniformity index also increases. The latter result indicates that the temperature distribution in the cooling plate becomes more uniform. The obtained results of present study are in good agreement with available experimental and analytical data, confirming that the presented computational fluid dynamics modeling using the selected turbulence model can accurately predict the flow field parameters in the cooling channels of PEM fuel cells.

Effects of Cooling Passages and Nanofluid Coolant on Thermal Performance of Polymer Electrolyte Membrane Fuel Cells

In this research, cooling of polymer membrane fuel cells by nanofluids is numerically studied. Single-phase homogeneous technique is used to evaluate thermophysical properties of the water/Al2O3 nanofluid as a function of temperature and nanoparticle concentration. Four cooling plates together with four various fluids (with different nanoparticle concentrations) are considered for cooling fuel cells. The impact of geometry, Reynolds number, and concentration is investigated on some imperative parameters such as surface temperature uniformity and pressure drop. The results reveal that, among different cooling plates, the multipass serpentine flow field has the best performance. It is also proved that the use of nanofluid, in general, enhances the cooling process and significantly improves those parameters directly affecting the fuel cell performance and efficiency. By increasing the nanoparticle concentration by 0.006, the temperature uniformity index will decrease about 13%, the minimum and maximum temperature difference at the cooling plate surface will decrease about 13%, and the pressure drop will increase about 35%. Nanofluids can improve thermal characteristics of cooling systems and consequently enhance the efficiency and durability of fuel cells.