Comparing Active and Passive Ventilation
Rising energy prices, environmental consciousness and the associated demand to enhance efficiency are key topics in the design of single and multi-family houses. One of the trends for increased efficiency in housing is passive houses, which don’t require classical building heating due to their excellent thermal insulation. These houses, however, need a complex ventilation system which often times causes criticism because it doesn’t allow a natural fresh air supply.
A new approach to guarantee the fresh air supply and the heat distribution across all rooms is to use dual outer walls.
Through skillful planning, the air hull surrounding the building can be used to control temperature and air distribution without the installation of ventilators, only based on the stack effect.
Convective flow effects can help to achieve both cooling in summer and heating in winter.
IBEEE used the SimScale platform to investigate and quantify the performance of the fanless ventilation system used in its passive houses. For this purpose, two simulations for identical designs were carried out, one with the active system and the other with the passive one.
CFD Analysis to Compare the Designs
First, the CAD model of the ventilation system was uploaded and meshed on the SimScale platform.
Despite the complexity of the geometry, the full-automatic mesh operation for internal flows could be used.
Within a few minutes, a high-quality computational grid was generated. With the support of the SimScale team, a working simulation of the complex system was set up.
The comparative analysis of the passive system could be derived from the existing simulation within a few minutes.
Improved Flow Rate by 40% with Passive Ventilation
Due to the availability of on-demand high-performance computing power on the SimScale platform, the engineers from IBEEE were able to complete the simulation, which was ready for direct evaluation in the web browser.
The physical quantities within the flow field, i.e. temperature, pressure, and velocity, were visualized as desired with cuts and streamlines and subsequently saved as image file. In the end, an automatic project documentation was created.
The simulation showed that the fan could not only be replaced by the stack effect but that this is actually more powerful than the active solution. The flow rate with 205m3/h is almost 40% larger than the one of the active solution.
The reason for this is the mixing of the air at the entrance. This leads to a homogenization of the temperature and reduces the buoyancy effects.
The overall cost of this simulation performed with SimScale was 50€ and the simulation working time — 2 hours.