[TRNSYS-users] Load calculation for radiant floor system

Eleftherios Bourdakis ebourdakis at gmail.com
Tue Jun 3 02:17:29 PDT 2014


Dear All,

I'm trying to simulate a radiant cooling floor for an office room. Firstly
I simulated the model I made in TRNBuild by using the 'heating' and
'cooling' options of it in order to find the maximum cooling demand of my
room.
Then I implemented the active layer in the floor and altered my model in
Simulation Studio in the following way:
1. I entered in an excel file the cooling demand I got from the first
simulation.
2. I'm calling this excel file in order to define the hourly flow rate by
this formula
'Hourly_flow_rate=Max_flow_rate*(Hourly_cooling_demand/Max_cooling_demand)
and I use this value as an input in the Type941 Air-Water Heat Pump.
3. I use a Type2 AquastatC for the cooling control signal of the Heat Pump.
The 'Temperature to watch' of the Type2 is the Operative temperature output
from my Type56 model and the setpoint for the Type2 is 27oC, while the
deadband is ±0.5oC.
4. In the Heat Pump I use as 'Inlet liquid temperature' a constant value of
15oC and I defined the 'Rated cooling power' as the maximum cooling demand
I got from the 1st simulation (Is this correct?)
5. Since in my heat gains I also have occupants, I included a ventilation
system consisting of a Type112b fan, a Type92, a Type 121b and Type108 as
it was described in the 'Temperature Level Control Tutorial' in order
mainly to remove the latent load.

My problem is that in my annual simulation while the 'Inlet liquid
temperature' is 15oC suddenly it is reduced to values such as -50oC or
-100oC and then back at 15oC! Instead of using an equation for defining
the 'Inlet liquid temperature' I used the output of the Type56 'fluid
outlet temperature of active layer' but I got similar results.

Do you know why this is happening? Should I use a component to define the
'Inlet liquid temperature'?
Thank you in advance for answering my question.

Best regards,
Eleftherios
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