Temperature distrubution in a cooling fin (result interpretation)

[eveS]

I am analyzing the lengthwise temperature distribution in a cooling fin (length: 30mm, width: 10mm, the tip is assumed to be adiabatic, Biot number is smaller than 0.1).

When I try to calculate the dimensionless temperature distribution (see calculation below), I obtain a curve which has a minimum at about 2/3 of the fin length and increases again after that (see attachment).

I don't understand why the temperature should increase again towards the tip of the fin. Using Ansys to model the fin I obtained the other curve in the graph, which shows decreasing temperatures towards the tip of the fin (and makes more sense to me).
I don't know whether I am making a mistake in my calculations, or whether there is a simple explanation.
Any advice would be appreciated!

calculation:

distribution "theta" (x) = cosh(m*(1-x/L)) / cosh(m) ,

where m= sqrt [ ( P*L*h) / (A*k) ]

L=length
P=perimeter
A=area
h=heat transfer coefficient
k=thermal conductivity

 

[uart]

distribution "theta" (x) = cosh(m*(1-x/L)) / cosh(m)

Pretty sure you've made a mistake in evaluating the above. For "m" a constant that expression definitely achieves its minimum when x = L.

 

[eveS]

Thanks for the suggestion uart, I'm not sure why it wasn't working, but it does now:)