scholarly journals Thermal Analysis of Heat Transfer Enhancement and Fluid Flow for Low Concentration of Al2O3 Water - Ethylene Glycol Mixture Nanofluid in a Single PEMFC Cooling Plate

2015 ◽  
Vol 79 ◽  
pp. 259-264 ◽  
Author(s):  
Irnie Zakaria ◽  
W.A.N.W. Mohamed ◽  
A.M.I Bin Mamat ◽  
R. Saidur ◽  
W.H. Azmi ◽  
...  
Author(s):  
Muhammad Syafiq Idris ◽  
Irnie Azlin Zakaria ◽  
Wan Azmi Wan Hamzah ◽  
Wan Ahmad Najmi Wan Mohamed

A Proton Electrolyte Membrane fuel cells (PEMFC) is considered to be a viable alternatives to Internal Combustion Engines (ICEs) in automotive applications due to the key advantages in thermal management system. The main duty of thermal management system is to maintain the desirable temperature, with a uniform temperature distribution across the stack and.its.individual membranes. In this paper, the thermal enhancement of a PEMFC cooling plate was analysed and presented. The hybrid Al₂O₃:SiO₂ was used as coolant in distributor cooling plate. The study focuses on water based 0.5% volume concentration of single Al₂O₃ , single SiO₂ nanofluids, hybrid Al₂O₃:SiO nanofluids with mixture ratio of 10:90, 20:80, 50:50, 60:40 and 90:10. The effect of different ratios of nanofluids to heat transfer enhancement and fluid flow in Reynold number range of 400 to 2000 was observed. A 3D computational fluid dynamic (CFD) was developed based on distributor cooling plates using Ansys 16.0. Positive heat transfer enhancement was obtained where the 10:90 Al₂O₃:SiO₂ nanofluids has the highest heat transfer coefficient as compared to other nanofluids used. However, all nanofluids experienced higher pressure drop. Therefore, the advantage ratio was used to analyze the effect of both heat transfer enhancements and pressure drop demerits for nanofluids adoption. The results concluded that 10:90 Al₂O₃:SiO₂ hybrid nanofluid is the most feasible candidate up to fluid flow of Re1000. The positive results implied that hybrid Al₂O₃:SiO₂ nanofluids do improve the single nanofluids behaviour and has a better potential for future applications in PEMFC thermal management.


Author(s):  
Gongnan Xie ◽  
Bengt Sunde´n

Gas turbine blade tips encounter large heat load as they are exposed to the high temperature gas. A common way to cool the blade and its tip is to design serpentine passages with 180-deg turns under the blade tip-cap inside the turbine blade. Improved internal convective cooling is therefore required to increase the blade tip life time. This paper presents numerical predictions of turbulent fluid flow and heat transfer through two-pass channels with and without guide vanes placed in the turn regions using RANS turbulence modeling. The effects of adding guide vanes on the tip-wall heat transfer enhancement and the channel pressure loss were analyzed. The guide vanes have a height identical to that of the channel. The inlet Reynolds numbers are ranging from 100,000 to 600,000. The detailed three-dimensional fluid flow and heat transfer over the tip-walls are presented. The overall performances of several two-pass channels are also evaluated and compared. It is found that the tip heat transfer coefficients of the channels with guide vanes are 10∼60% higher than that of a channel without guide vanes, while the pressure loss might be reduced when the guide vanes are properly designed and located, otherwise the pressure loss is expected to be increased severely. It is suggested that the usage of proper guide vanes is a suitable way to augment the blade tip heat transfer and improve the flow structure, but is not the most effective way compared to the augmentation by surface modifications imposed on the tip-wall directly.


2014 ◽  
Vol 1082 ◽  
pp. 327-331
Author(s):  
Thiago Antonini Alves ◽  
Murilo A. Barbur ◽  
Felipe Baptista Nishida

In this research, a study of the heat transfer enhancement in electronic components mounted in channels was conducted by using different materials in the conductive substrate. In this context, a numerical analysis was performed to investigate the cooling of 3D protruding heaters mounted on the bottom wall (substrate) of a horizontal rectangular channel using the ANSYS/FluentTM 15.0 software. Three different materials of the conductive substrate were analyzed, polymethyl methacrylate (PMMA), fiberglass reinforced epoxy laminate (FR4), and pure aluminum (Al). Uniform heat generation rate was considered for the protruding heaters and the cooling process happened through a steady laminar airflow, with constant properties. The fluid flow velocity and temperature profiles were uniform at the channel entrance. For the adiabatic substrate, the cooling process occurred exclusively by forced convection. For the conductive substrate, the cooling process was characterized by conjugate forced convection-conduction heat transfer through two mechanisms; one directly between the heaters surfaces and the flow by forced convection, and the other through conduction at the interfaces heater-substrate in addition to forced convection from the substrate to the fluid flow at the substrate surface. The governing equations and boundary conditions were numerically solved through a coupled procedure using the Control Volumes Method in a single domain comprising the solid and fluid regions. Commonly used properties in cooling of electronics components mounted in a PCB and typical geometry dimensions were utilized in the results acquisition. Some examples were presented, indicating the dependence of the substrate thermal conductivity related to the Reynolds number on the heat transfer enhancement. Thus, resulting in a lower work temperature at the electronic components.


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