CFD Online Discussion Forums - [swak4Foam] Temperature dependent heat transfer coefficient with groovybc

Hello,
I try to approximate heat loss in a rectangular bubble Column due to convection. In order to do so, I use the groovy boundary condition in OpenFOAM. The bubble column which consists of acrylic glass is insulated with styropor. At t=0 the bubble column contains water with a temperature of 46°C. As time progresses, the bubble column is fed with air which has a temperature of 18°C. The direct consequence is that the water temperature drops. In order to simulate this heat loss I used groovybc:

Code:

type                           groovyBC;

value                         uniform 319.15;

variables "k_1=0.597;htot=1/(0.03/0.035+0.01/0.19+1/0.021);Tinf=291.15;";        

valueExpression             "Tinf";

fractionExpression     "1.0/(1.0+k_1/mag(delta())*1/htot)";

The number 0.021 represents the external heat transfer coefficient due to natural convection. In order to describe the heat loss more precisely, I would like to update the external heat transfer coefficient after each timestep. Therefore I need to access the nodetemperatures which are closest to the inner wall. Has someone got an idea how this problem can be handled during the simulation?

Greetings

P_P