How do I simulate chilled slabs?
The simplest way to do chilled slabs is to set a suitable radiant fraction for cooling in ApacheSim. The radiant fraction will depend on the position (floor or ceiling) and shape (chilled beams/chilled ceilings) of the cooling elements.
Other approaches requiring a bit more effort (and data) are:
1. Use 'Direct acting heaters' in ApacheHVAC, setting a negative value for the output of the 'heaters'. This allows the 'idealised' approach to cooling control (much as in ApacheSim) to be combined with other system features such as controlled mechanical ventilation.
2. Model the cooling slabs as separate rooms in ApacheSim. They can be controlled either using ApacheHVAC controllers or formula profiles. You might use this approach if you judged it important to model the dynamics of heat transfer through the floor slab to adjacent rooms/ground masses above and below.
3. Use the 'Chilled ceilings' component in ApacheHVAC. This models the flow of water through the chilled ceiling by a method analogous to the way ApacheHVAC treats radiators, and takes account of the dynamics associated with the thermal capacity of the ceiling and the water.
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