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LiaoGang, This is quite a common issue and the behavior you are seeing is
normal. The short answer to your question is: stick to using a
small time step. Remember that TRNSYS iterates at each timestep to find a converged solution if there are any control decisions to be made then TRNSYS can make one control decision (such as turning on or off a piece of equipment) per time step. The equipment must then stay on (or off) for the entire duration of the next timestep. If your time step is big then the system will be driven a long way from where it started before the end of the time step. Imagine if the thermostat in your home could decide to turn on heating only once per hour. If the heating had to stay on for the entire hour then chances are that the home would be uncomfortably hot by the time the thermostat was allowed to make a new decision. TRNSYS forsees this (in a way) and can't decide whether it is better to leave the heat on or off. If you shorten the time step then the on/off decision becomes quite a lot simpler and overheating and undercooling become less of a problem. kind regards, David
On 04/19/2018 04:11, 廖刚 via
TRNSYS-users wrote:
-- *************************** 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 |