[TRNSYS-users] Energy losses on solar collector's heat exchanger before the loop starts

[Javier Vega via TRNSYS-users]

Hello TRNSYS community,

I'm using Type 538 and 539 to model ETC and Flat Plate collectors. I have
them connected to Type 695 (variable speed pump) and a HX in a solar water
tank modeled through Type 543 (Coiled). In the tank, there is also another
HX connected to a Heat Pump water loop.

I'm using Type 538 and Type 539 in Control Mode 4, meaning the solar
collector loop works only if the fluid can win energy. But, nevertheless,
everytime the solar collectors activate and start to supply energy, I get
negative power peaks. I've noticed the same occurs sometimes with the heat
pump's heat exchanger, but just a few times.

I haven't calculated the impact of this phenomenon in my whole simulation.
Anyway, should I really expect this results in my calculations? Maybe it's
the effect of the capacitance of the collectors array.

I will attach some images that may help. The units are in kW and the info
shown in the plot correspond to the energy transfer rate in the Heat
Exchangers.

[image: Imágenes integradas 1]

[image: Imágenes integradas 2]

Thanks in advance, greets from
Javier Vega Benavente
Mechanical Engineering Student, Universidad de Concepción, Chile
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