MODELLING OF MASS TRANSFER IN A DIRECT METHANOL FUEL CELL

Abstract

In this dissertation work, a mathematical, one-dimensional, steady-state model accounting for mass transfer, along with the electrochemical reactions taking place in the direct methanol fuel cell (DMFC), is developed. The model is based on some assumptions. We are interested in mass transfer because poor mass transfer leads to significant fuel cell performance loss, therefore to understand the mass transfer phenomenon in the direct methanol fuel cell deeply we have done the modelling of mass transfer in a DMFC. Methanol concentration goes on decreasing as we move from anode flow channel to membrane. This is because diffusion takes place in diffusion layer while in catalyst layer concentration decreases due to consumption. In AF region there is no loss in methanol concentration we have assumed that the anode flow region is to be treated as continuous stirred tank reactor (CSTR). The methanol concentration is supposed to be zero in the membrane region but in actual some methanol crosses the membrane region and reaches then cathode side where it reacts with oxygen in the cathode catalyst region. This phenomenon is known as methanol crossover. The model input is the model governing equations and the model output is the methanol and water concentrations in the anode flow (AF), anode diffusion (AD) and in anode catalyst (AC) regions. The model determines the net water transfer coefficient (α), which is an important parameter to describe the water management through the membrane in the direct methanol fuel cell. It describes the behavior of the net water transfer coefficient (α) with the current density of the cell. The model is implemented rapidly and suitable for real-time system direct methanol fuel cell calculations.