Improving the performance of an air-cooled fuel cell stack by turbulence inducing grid

Pløger, Line Justesen ; Fallah, Rasheed

4. term

Energy Engineering, Master

2018

2018-06-01

99 pages

Protonudvekslingsmembranbrændselsceller (PEMFCs) vinder mere popularitet som en alternativ strømkilde for sin enkelhed og hurtig opstart. De kommercialiseres til et stort antal applikationer, der spænder fra bil til stationære, f.eks. Strømforsyningsenheder til telekommunikation. Et af problemerne vedrørende PEMFC er den termiske styring af den elektrokemiske reaktion, hvilket resulterer i en overophedning af den Ballard 1020 ACS luftkølet brændselscellestabel ved lave strømtætheder 0.4 A per kvadrat centimeter. Forskere i Energiavdelingen på Aalborg Universitet fandt ud af, at det største problem i termisk styring er varmeoverførslen i luften inden for katodekanalerne. Denne undersøgelse har til formål at løse problemet ved at placere firkantede og honeycomb turbulensgitter før katodeindgangen. Formålet med turbulensgitterne er at inducere turbulenser i katodekanalerne og derved øge blandeffekten for at forbedre varmeoverførslen inde i kanalerne. En computational fluid dynamic (CFD) model er bygget og assisteret af eksperimentelt arbejde. CFD-resultaterne viste en forbedring af blandeffekten i katodkanalerne, og der opnås en reduktion af kanalvægstemperaturen. Forsøgene har resulteret i en forøgelse af ydeevnen med henholdsvis 10,42 % og 2,75% for henholdsvis kvadratisk og honeycomb grid

Proton exchange membrane fuel cells (PEMFC’s) are gaining more popularity as an alternative power source for its simplicity and quick startup. They're commercialized for large number of applications ranging from automotive to stationary e.g powering telecom backup units. One of the problems regarding PEMFC's is the thermal management of the electrochemical reaction resulting in an overheat of the Ballard 1020 ACS air-cooled fuel cell stack at low current densities \SI{0.4}{A \per cm^2}. Researchers in Energy Department at Aalborg University found that the biggest problem in the thermal management is the heat transfer into the air inside the cathode channels. This study aims to solve the problem by placing square and honeycomb turbulence grids before the cathode inlet. The purpose of the turbulence grids is to induce turbulences in the cathode channels and thereby increase the mixing effect in order to improve heat transfer inside the channels. A computational fluid dynamic (CFD) model is build and assisted by experimental work. The CFD results showed an an improvement of the mixing effect in the cathode channels and a reduction of the channel wall temperature is obtained. The experiments have resulted in an increase of the performance by 10.42 %}and 2.75 %}for the square and honeycomb grid respectively.

Grid ; CFD ; Turbulence intensity ; Fuel cell

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