|
Devin, The default value of the zone capacitance is 1.007*1.2*ZoneVolume. It accounts only for the capacitance of the air in the zone and does not account for any furnishings or zone contents. I typically modify the capacitance to be about 5 times the default value (up to 10 times for zones that have a LOT of stuff in them like a library, a warehouse, or (unfortunately) my basement). Whether you leave the default value or whether you increase it, there is still thermal lag from the concrete but that lag is heavily influenced by the heat transfer coefficient between the zone air and the concrete wall. Best, David On 6/26/2011 10:32, Devin Rohan wrote: I have a single zone office with a concrete slab and non-massive walls. I only seem to get good agreement between TRNSYS and a 1D finite difference model I built when I increase the Zone Air capacitance into the thousands (4000-6000 kJ/K). Other wise, TRNSYS's air temperature varies wildly and unrealistically with the ambient temperature and there's no thermal lag from the concrete. Is this high of value for the zone air capacitance ok? -- *************************** David BRADLEY Principal Thermal Energy Systems Specialists, LLC 22 North Carroll Street - suite 370 Madison, WI 53703 USA P:+1.608.274.2577 F:+1.608.278.1475 d.bradley@tess-inc.com http://www.tess-inc.com http://www.trnsys.com |