# Question: Fuel Cell Thermodynamic Equations

1. Jan 26, 2009

### Scorael

I'm an undergrad working on fuel cells for a project and I have been using a book to aid me. There are several equations in the book that were not explained properly so I was hoping someone on this forum could help identify how they were derived.

The first 2 is related to the pressure within the system of the fuel cell. Hydrogen is pumped in 1 end and air in the other and their partial pressure is found using these formulas:

$$p_{H2}=0.5*\frac{P_{H2}}{exp(1.653*i/T^{1.334})}-P_{H2O}$$

$$p_{O2}=\frac{P_{air}}{exp(4.192*i/T^{1.334})}-P_{H2O}$$

From what I gather, this appears to be Dalton's Law but I am not sure how did the numbers 1.653, 4.192 and 1.334 pop out from.

The next one is water diffusivity which the author defined as:
$$D_{\lambda}=10^{-6}exp(2416(\frac{1}{303}-\frac{1}{353}))*2.563-0.33*10+0.0264*10^{2}-0.000671*10^{3}$$

For this one I am not sure what is the significance of 10 in this equation such that is appears 3 times in the equation without being simplified into a constant.

I'm studying electrical engineering so when it comes to thermodynamics this is way pass me. I hope someone on this forum will be able to help out.