IBP / Software / WUFI-ORNL/IBP / Tour 2

Software / WUFI-ORNL/IBP / Tour 2

Calculation

After entry of a few remaining data like surface transfer coefficients *), initial conditions etc., the calculation can be started. WUFI-ORNL/IBP then computes the temporal evolution of the temperature and the moisture field in the component. For the present example, a calculation spanning one year in one-hour steps takes about 10 minutes on a Pentium-500.
*) WUFI-ORNL/IBP offers experimentally verified default values.

During the calculation, WUFI-ORNL/IBP optionally displays the newly computed temperature and moisture fields after each step, allowing you to watch the processes in the component as a 'film'. This film display is, of course, somewhat slower, so that you should perform lengthy calculations without the film; on the other hand, you can immediately see whether a test calculation or a parameter study conforms to your expectations and stop it if necessary.
The direction and magnitude of the heat and moisture flows across the interior and the exterior surface as well as across the inner material interfaces are indicated by corresponding arrows.

Calculation Results and Comparison with Experiment

Displaying the Results

After the calculation, the results - stored in a binary result file - are available for display and analysis.

WUFI-ORNL/IBP lets you display the curves of courses in time and cross-sectional profiles as graphics, compare them with measured data, edit and print them. You can also view graphics of the climate data.

You can watch the film after the calculation at your leisure; you can export it, together with an external viewer, to a diskette.

If you want to process the results on your own, you can export them to ASCII files.

Courses

For the entire simulated time span WUFI-ORNL/IBP produces courses which describe the temporal behaviour of the following quantities:

the heat flux densities through the interior and exterior surface, respectively,
the temperatures and relative humidities at an arbitrary number of freely selectable monitor positions,
the mean moisture content of each material and the total moisture content of the entire building component.

The diagram for the present example shows the resulting courses of the moisture content, averaged over the cross-section of the lime silica brick masonry, and compares them with the gravimetrically measured values. It takes the wall with mineral wool insulation somewhat over one year to reach the normal equilibrium moisture of 2.5 vol.% and the wall with EPS insulation two and a half years.

Profiles

In addition, for points in time selected by the user WUFI-ORNL/IBP provides profiles which show the distribution of the following quantities across the component:

the temperature,
the relative humidity,
the moisture content.

The diagram shows a comparison between the measured and the caculated moisture content profiles for four different points in time. Evidently, good agreement between measurement and calculation can be achieved for EPS insulation (top) as well as MW insulation (bottom).

The shape of the moisture profiles indicates that in the case of the EPS insulation most of the initial moisture dries out towards the room side (right), whereas the ETICS with the more permeable mineral wool also allows considerable drying to the outside which results in quicker overall drying.

Film

WUFI-ORNL/IBP also writes a film file during the calculation which contains all the computed profiles and which - displayed as a 'film' - conveys a dynamical impression of the thermal and hygric processes in the component.
This film is ideal for gaining insights into the hygrothermal processes and for developing a 'feel' for the situation in the component. The reactions of the different materials to the changing climatic conditions can be watched directly.

In the present example, a good correspondence between calculation and experiment is obtained, so that the calculation method in general as well as the material parameters used for this specific example can be considered valid. Therefore, it is now possible to perform a purely computational examination of variants and extrapolations of this experiment.

Please contact:

Dr. Achilles Karagiozis

Phone +1 (865) 576 3924

Fax +1 (865) 574 9354