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Raffaele, I am afraid that we are no longer actively supporting TRNSYS 16. However, I looked at your project quickly. The data file for your chiller shows that at low part load ratios, it has some cooling capacity but does not require any input energy. The first line of performance data in the file is: 0.7237 0.0000 which indicates that at the following conditions: fraction of design load = 0. chilled water setpoint = 5.5C entering cooling water temperature = 24C inlet hot water temperature = 75C the device can produce 72.4% of its rated capacity and requires no input energy to do so. I would imagine that the reason the chiller is giving you a zero COP is that it is operating at low load conditions and the model is showing that it needs no input power in order to do so. Probably the machine cannot operate at part load less than about 20%, in which case the capacity ratio as well as the fraction of design energy input ratio should be zero. As for the auxiliary heater problem, I am less sure as to the cause of the problem. However, I did notice that the tank in that loop is 7000L, that the pump has a flow rate of 26000L/h and that your time step is 1 hour. That would mean that the pump (which is always on according to your controls) turns over the entire volume of the tank almost 4 times per timestep. Actually I am a bit surprised that the simulation runs at all! In order for systems to be numerically stable, there must be at least enough volume in flow loops to store at least 1 time step of flow. Also keep in mind that a system can only make one control decision per timestep; a one hour timestep is very long. I would recommend something on the order of 1 or 5 minutes. Best, David On 10/16/2012 16:56, Ralph Lanegan
wrote:
Dear TRNSYS users, -- *************************** 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 |