A New Design of Mini Heat Exchanger for PEMFC Bipolar Plates

2006 ◽  
Author(s):  
Yahia Lasbet ◽  
Bruno Auvity ◽  
Cathy Castelain ◽  
Hassan Peerhossaini
Keyword(s):  
Heat Transfer ◽  
Fuel Cell ◽  
Electrochemical Reaction ◽  
Electric Energy ◽  
Transfer Efficiency ◽  
Specific Power ◽  
Bipolar Plates ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Heat Transfer Efficiency

Fuel cell is a power generator which directly converts chemical energy to electric energy through an electrochemical reaction instead of thermal combustion. The electrochemical reaction produces as much heat as electric energy. In transport applications where the specific power density of the fuel cell is relatively high a large amount of heat should be evacuated from the system. Therefore, heat exchangers integrated in the bipolar plates play an important role in the operation and life time of fuel cells. Conventional designs of the cooling system of the current bipolar plates consist of a net work of parallel straight channels of half of the bipolar plate’s thickness. These designs reach rapidly their limit of efficacy and new designs are needed. Reynolds number in the bipolar channel flow is around 200; therefore the flow regime is laminar which is known for its weak heat transfer efficiency. In this work we present a new geometry of the cooling channels of bipolar plates in which heat transfer efficiency in laminar regime is enhanced by generating chaotic trajectories. Here we characterize the heat transfer characteristics of a single channel. Firstly, hydrodynamic and heat transfer characteristics of several channel geometries are characterized by using the CFD code Fluent. Thermo-physical properties of the working fluid are those of water and the velocity profile at the channel entrance is that of a fully developed Poiseuile flow. Secondly, fluid mixing along the channels is evaluated using two different criteria. For these calculations, thermal boundary conditions on the channel walls are adiabatic and the entrance of the channel is divided in two (horizontal or vertical) parts. In one part water flows at 300K while in the other part water is at 320K. The first criteria is the ratio of (Tmin/Tmax-Ro)/(1-Ro) over cross-section surfaces calculated for Reynolds numbers 100 and 200 and for both horizontal and vertical positions of the dividing surface at the entrance.

scholarly journals Enhanced Heat Transfer Characteristics of Graphite Concrete and Its Application in Energy Piles

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Qingwen Li ◽  
Lu Chen ◽  
Haotian Ma ◽  
Chung-Ho Huang
Keyword(s):  
Heat Transfer ◽  
High Heat ◽  
Transfer Efficiency ◽  
Heat Transfer Characteristics ◽  
Enhanced Heat Transfer ◽  
Energy Pile ◽  
Transfer Characteristics ◽  
Heat Transfer Efficiency ◽  
High Heat Transfer ◽  
Energy Piles

The latest research on energy piles demonstrates that most scholars are focusing their attention on optimization by designing more efficient heat exchanger coils, analyzing the heat pump matching parameters, and so on. However, after more than 20 years of development, these traditional methods for improving the heat transfer efficiency of energy piles have reached a bottleneck, and a new approach for the continued enhancement of this technology must be investigated. In this study, powdered graphite with high heat transfer characteristics was included in a concrete mix to create graphite concrete piles with enhanced heat transfer characteristics. The results from theoretical analysis, laboratory testing, and numerical simulation indicate that using graphite to improve the heat transfer efficiency of a concrete material is an effective method for enhancing the thermal efficiency of an energy pile system. The research results also show that the heat transfer coefficient of the concrete exhibits greater improvement when the graphite content is greater than 15% under the same environmental temperature. After studying the performance of the proposed graphite concrete energy pile under different environmental temperatures (10°C, 20°C, 30°C, and 40°C), the results indicate that the working efficiency of the energy pile is better in the summer than in the winter. Finally, parameters such as the cast-in pipe configuration and pile spacing are optimized.

Study of Heat Transfer Characteristics for the Fuel Cell System of the Humidifier due to Analysis and the Hot Testing

2011 ◽  
Author(s):  
Seon-hwa Kim ◽  
Jae-jun Lee ◽  
Young-min Oh ◽  
Sang-hoon Lee ◽  
Jae-sik Kim
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Fuel Cell ◽  
Heat Exchangers ◽  
Thermal Characteristic ◽  
Cell System ◽  
Test Facility ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Operation Temperature

The MCFC system of BOP (Balance of Plant) is contained various mechanical equipments. One of the equipments of the heat exchangers is important component for efficiency and cost. In MCFC system, several heat exchangers are used according to the application. Most typical heat exchanger is the humidifier in BOP for MCFC, which is named for the humidifier because it is to preheat the fuel and water so that a reactor will convert some of the incoming fuel to hydrogen. Then, hot side fluid service is used the exhausted gas from the fuel cell and cold side fluid service is the fuel and water. The operation temperature range is about 25∼500 Celsius Degree.[1] This heat exchanger has the problems of multiphase fluid and phase change heat transfer. So it is necessary to analyze the heat transfer characteristics and to propose the reasonable design methodology for the humidifier. In this study, the thermal characteristic for the humidifier is estimated by using commercial tool of heat exchanger design, rating and simulation. Also this study presents the results for test facility of fabrication and for testing.

Characteristics of Micro-Liquid-Layer Behavior in a Mini-Channel Vaporizer for Water and Ethanol

2006 ◽  
Author(s):  
Yoshio Utaka ◽  
Yutaka Tasaki ◽  
Kousuke Ichii
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Fuel Cell ◽  
Pool Boiling ◽  
Fuel Cell Vehicle ◽  
Bulk Liquid ◽  
Growth Speed ◽  
Heat Transfer Characteristics ◽  
Simple Method ◽  
Transfer Characteristics

With growing demands for a cleaner global environment, there is a need for automotive powertrains that can provide higher efficiency and contribute to lower C02 emissions. From this perspective, fuel cell vehicles are expected to gain a share of the automotive market in the 21st century. The reformer type fuel cell vehicle requires a heat exchanger with high efficiency and a low heat capacity to meet powertrain requirements for quick response and compactness. The use of a mini-channel vaporizer for the reformer is one possible way of meeting these requirements. In a mini-channel, the bulk liquid, bubbles and thin film that form between the heating surface and the bubbles affect the heat transfer characteristics in complex ways, just as in the case of pool boiling. However, as reported in the literature, the characteristics of evaporation in a mini-channel are completely different from those of pool boiling, because of the important role played by the superheated thin film that forms in the process of bubble expansion. For example, although deterioration of heat transfer characteristics has been reported for an extremely small gap, the mechanism involved has not yet been analyzed. In order to research and develop a mini-channel vaporizer efficiently, it is necessary to elucidate the mechanism of these phenomena, and clarify measures for improving heat transfer characteristics. Then a simple method may be devised, based on the related findings, to predict the heat transfer characteristics of a mini-channel vaporizer with sufficient accuracy at the development stage. In this study, by using ethanol instead of water as used in past research, the thickness of the thin film that plays an important role in the heat transfer characteristics was measured by application of the laser extinction method for channel gap sizes of 0.3 and 0.15 mm. The process of bubble growth was simultaneously recorded with a high-speed camera. These results were then compared with those obtained for water. Similar trends as those obtained for water were observed for ethanol. That is, observations show that the thin film thickness is essentially influenced by the growth speed of the interface between the bubble and the bulk liquid and that it approaches a certain value above a certain speed. At the same time, the thickness of the thin film decreases with a decrease in gap size.

scholarly journals Study on Heat Transfer Characteristics of the Whole Plate Fin Tube Cooler

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
Y. Zhou ◽  
L. Zhang ◽  
S. Bu ◽  
C. Sun ◽  
W. Xu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Transfer Characteristics ◽  
Frictional Pressure Drop ◽  
Transfer Characteristics ◽  
Heat Transfer Efficiency ◽  
Fin Tube ◽  
Fin Tubes

In order to enhance the cooling efficiency of plate-fin motor cooler, two kinds of plate-fin-tubes were proposed, which named triangle-wing and convex fin-tube. The heat transfer characteristics of fin-tubes are investigated via numerical simulation and experiment. The result showed that the k-ε turbulence model is highly accurate in simulation of cooler, and the deviation of average heat transfer coefficient and frictional pressure drop between experiment and simulation is within 10% and 8%, respectively. Both of the triangle-wing and convex fin-tube can increase the heat transfer efficiency of plate-fin cooler. The frictional pressure drop also has an approximate variation trend. In addition, the pressure drop of convex-fin-tube is smaller than triangle-wing-fin-tube on the premise of the same heat transfer coefficient, so the heat transfer performance of convex-fin-tube is the best.

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