# A Numerical solution in matlab

1. Sep 26, 2016

### Meaningless

Hi Guys,

I'm trying to do a simple first-order, 1d (x-direction) simulation of mass transfer with the finite element toolbox in matlab for the following closed set of equations:

(Please note: "X" is not to be confused with the lowercase spatial dimension "x")

However, every time I cannot define the temperature (at least with exponential and erfc) without an error. Does anyone know if there is a proper syntax for this?

2. Sep 26, 2016

### Staff: Mentor

3. Sep 26, 2016

### Meaningless

This is the syntax I directly entered into the toolbox (I have also directly replaced "P" with the T-dependent expression). I also set x = X for the calculation. I am pretty sure one or two of my variables is not coded properly, particularly the temperature, T.

X' = (K/TX_t)*((10^(A-(B/TX_t + C)))^2)/X_t

TX_t = T0 + C*(t*exp(-X^2/t) + (X/2)*erfc(X/t))

4. Sep 26, 2016

### Staff: Mentor

Okay, I'd start with building up the expression until it fails so then you have an even simpler failure to show us.

Perhaps:
Code (Matlab M):

t=(1:0.1:11)           // create t array of (1,1.1,1.2,1.3 .... 10)
x=(0:0.1:10)         // create X array of (0,0.1,0.2,0.3 ... 10)      same number of elements as t

y = erfc(x./t)          // notice the use of ./ because here you want to do an element by element /