A chaotic heat-exchanger for PEMFC cooling applications

High-efficiency cooling systems are key points in PEMFC transport applications, as the volume constraints force the reduction of the stack size while increasing the power density. Moreover, to ensure an optimal electrochemical reaction over the whole polymer membrane surface and hence a maximum efficiency, the temperature field in the cell must be uniform and stay in a narrow range, around 80-90 degrees C. This study focuses on improving the thermal performance of heat-exchangers integrated in the bipolar plates of PEMFCs. The current design of the heat-exchangers in these applications is quite simple; cooling liquid (water) flows in straight channels or serpentines in the rear of the plates. The flow regime is laminar with a Reynolds number around 200. In order to enhance convective heat transfer, we propose here to promote three-dimensional flow inside cooling channels using a novel channel geometry that generates chaotic advection flow. However, to limit the size and the electric resistance of the bipolar plates, the thickness must be severely limited. This work concentrates on developing and characterizing heat-exchangers that can be easily reduced in size while preserving high thermal performance. (c) 2005 Elsevier B.V. All rights reserved

Improvement of transfer phenomena rates in open chaotic flow of nanofluid under the effect of magnetic field: Application of a combined method

Numerical investigation is carried out in the present research in order to assess the effects of a combined technique on heat transfer and fluid motion. A linking between three promoting ways to enhance transfer phenomena presented in terms of regime flow (chaotic flow), the fluid type (nanofluid) along with a non-intrusive means (magnetic induction) is considered throughout the current study. In this project, magnetohydrodynamic MHD field is applied with two different manners; either on the full geometry or partially on selected portions of the channel. Moreover, evolutions of local and average Nusselt numbers, thermal and velocity fields, average wall shear rate in addition to the flow patterns are examined for Hartmann number, Reynolds number and different scenarios of the MHD field application and direction. Findings illustrate that Nusselt number and therefore heat transfer is an increasing function with Ha number in the case of partial mode and transversal orientation of the MHD field. While it is either a constant, decreasing or slightly augmented function with Ha in the other applications. An amelioration of about 13% in heat transfer is recorded for the optimum case compared to the standard situation (without magnetic field). Besides, it is shown that Re number grows heat exchanges with an existing critical value of Re for the transversal orientation case, where the effect of the MHD mode on the average Nu number is differently. © 2020 Elsevier Lt

Experimental investigation on the influence of a biodiesel (waste cooking oil) on the performance and exhaust emissions of a compression ignition engine

International audienc

Chaotic Transport in Three-Dimensional Reactors Operating in Open Flows for Continuous Biodiesel Production from Rapeseed Oil: Numerical and Experimental Comparative Study

International audienceThe present study aims to investigate a suitable biodiesel production process. Two reactors called serpentin-3D (S-3D) and New-Serpentin-3D (NS-3D), operating in continuous mode, are used to produce biodiesel. The thermal and dynamic characterizations of both reactors are numerically examined for several Reynolds number values. In addition, the conversion of the rapeseed oil to biodiesel is experimentally performed by the transesterification reaction. Numerical results showed a better quality of thermal mixing using NS-3D geometry where the degree of mixing is close to 1 for miscible and immiscible fluids. The experimental study illustrates that the conversion rate, using the reactor based on NS-3D geometry, is about 99%. Moreover, the properties of the biodiesel are in compliance with the required standard EN14214 (MG = 0.7 20 % m/m, DG = TG = 0.2 % m/m). Therefore, the NS-3D geometry could present a better alternative for the continuous production of biodiesel