Updated Perforated Tile Models

[jvangilder]

We just updated the Perforated Floor and Ceiling Tile models. These changes do not affect user settings but rather the physics. We had previously added "straightening" so that the airflow exiting the tile is purely vertical. ('Straightening is an optional user setting for Porous Plates.) In today's update, we added a "momentum kick" to better model the physics associated with airflow squeezing through small holes (in, say, a perforated plate) and exiting with local airflow speeds that are higher than the average. We also, changed the empirical relationship between the % open area and the loss coefficient.

These changes are made to reflect the state of the art in tile-modeling practices and have been guided by an ongoing ASHRAE research project (RP-1675, Guidelines for CFD Modeling of Data Centers). And, like the IT Rack model, the Perforated Tile model is a "compact model" which aims to provide accurate simulations while being geometrically simple and computationally efficient.

How will this affect results? Well, both of today's changes will affect results to some degree for models that contain Perforated Floor and/or Ceiling Tiles. Generally, IT Rack Cooling Check assessments may improve a little. This is mainly due to the fact that the additional vertical momentum pushes the airflow a little higher in the vertical direction. In any case, the new model has been tested against detailed CFD and experimental data to provide higher accuracy.