BOLTZMANN SOLUTION OF COUPLED NONLINEAR EQUATIONS FOR MOISTURE CONTENT w(s) AND TEMPERATURE T(s), s=x/root(4t). BENCHMARK TEST I, CEN (2002).

Rapport, 2012

There are many models for coupled moisture and heat flow in porous building materials. A question is how accurate the various models are. There is a need to compare the models with a solution with high and well documented accuracy. The model with its Mathcad files presented here tries to meet that need. It was originally presented in Dresden 2002 at a CEN meeting. The solution is now used in a provisional European standard: • European Provisional Standard prEN 15026, Hygrothermal Performance of Building Components and Building Elements – Assessment of Moisture Transfer by Numerical Simulation, 2005. The presented model may be summarized in the following way: • Highly non-linear coupled moisture and heat flow • Highly unbalanced time scales between moisture content w and temperature T • Any functional relations for flow coefficients and state functions are easily implemented • Directly verified accuracy from with errors in the equations below 0.03 %. • Implemented in Mathcad.