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Chen, Type60 allows you to specify three of the four flows, in which case it will internally compute what the required fourth flow must be. The two inlet flows are defined as a positive value meaning flow into the tank. The two outlet flows are defined as a positive indicating a flow out of the tank. Flows may be zero but they cannot be negative (in other words you can't have fluid coming in through an outlet port nor out through an inlet port). In your simulation, inlet flow 1 comes from the load side of the heat exchanger, inlet flow 2 is set to the value zkmassflow, and outlet flow 2 is set to the value of zkmassflow+zkflow. If there is no flow from the heat exchanger into the tank and zkflow is positive then the mass balance can't work. In order for it to work, flow would have to enter the tank through outlet port 2. One other thing that I noticed: check the answer to the question about how many nodes there are in the tank on the Type60 "output" tab. The question is "besides the top and bottom nodes, how many nodes are there?" so the answer needs to be 8 whereas the other two tabs ask simply "how many nodes are there?" Best, David On 2/11/2013 11:34, Chen Luo 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 |