Li Mei,Most of the pump models in TRNSYS set the outlet temperature to the inlet temperature when there is no flow. If you have a Type11 controlled diverter valve between the pump and the heat exchanger, this might not be the case. If that is the case, I'd recommend using Type6647 from the TESS Hydronics Library (if you are able). Normally the temperature of the liquid in the heat exchanger would tend towards the tank temperature when there is no flow. It may be that the UA being calculated between the heat exchanger and the tank liquid is too low. I'd recommend looking carefully at the heat exchanger parameters and also looking at the heat exchanger UA output of Type60 to make sure that they look reasonable.
Kind regards, david L.Mei@lboro.ac.uk wrote:
Dear trnsys users,I meet the problem with the heat exchange in the water tank (Type 60f) connected to the solar collector (Type 73) which is controlled by a pump (when the Tin>=Tout, the pump running). When the pump during the off period, the water of the heat exchange keeps the same temperature at the time step of the pump turned off. It is much higher (Around 10 degree) than the water temperature in the tank surrounding the heat exchange. That means there are no heat conducted to the tank from the heat exchange when no flow running in the solar collector. This caused the problem of reducing the running hours of the solar collector and so reducing the solar fraction.Any helps are available?Li Mei _______________________________________________ TRNSYS-users mailing list TRNSYS-users@cae.wisc.edu https://www-old.cae.wisc.edu/mailman/listinfo/trnsys-users
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