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Jesper, For the most part, TRNSYS liquid storage tank models define entry ports and exit ports. Liquid can't go into the tank through an "exit" or out of the tank through an "entry." Entry and exit port pairs are also matched (again, usually) so that any liquid that comes in through an entry goes out through the corresponding exit. The most flexible tank model in terms of the number and configuration of entry/exit ports is 534 so I think it is a good idea if you stay with that. If you have bi-directional flow in your system, you need to model two flow paths in your simulation. There is a bi-directional flow pipe model in the TESS Hydronics Library but since you are already limited by defining tank ports as either entry or exit, you might as well use Type31 (there are some other advantages to the bidirectional pipe model as well). I am reasonably sure that once you solve the mass balance problems, the results will make more sense. Kind regards, David On 8/21/2011 13:27, Cheong Chu Siang Jesper wrote: I'm trying to model a PVT system which consists of clusters of different PVT modules that cogenerates electricity and hot water for showering. Hot water storage is achieved using a mains pressured 3 tank system. However I have not been able to model the 3 tank system using the available storage tank subroutines(type 4, 60, 534). Tank temperatures obtained are very low when compared to results from a mathlab simulation. Mass balance failures are reported in the list file, which i attribute to the incorrect connections between tanks. I believe the problem lies in the 2 way flow between tanks that is not corrected modelled in the simulation. Is there any way to correct this? I've attached a simple diagram of the system i'm trying to model. Does anyone have prior experience with multi tank setups and can provide some guidance? Thanks, Jesper_______________________________________________ TRNSYS-users mailing list TRNSYS-users@cae.wisc.edu https://mailman.cae.wisc.edu/listinfo/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 |