[TRNSYS-users] Temperature level control is not working

[David BRADLEY]

Michael,
   My apologies for the delay in looking at the problem. You have set up 
the temperature level control correctly (nicely done). There are two 
reasons why your zone is not holding temperature. First, the thermostat 
model is set to hold a cooling set point temperature in the kitchen of 
24C. However, your cooling device is set to provide a 25C supply 
temperature. I would recommend a supply temperature in the neighborhood 
of 10-12C. Second, the zone that you are controlling (the kitchen) has a 
LOT of internal gains and the capacity of the cooling device that you 
have selected (10,000 kJ/h - 2.8kW) is not enough to cool the space.

   As a side note, there are a few problems with the way you've done the 
cooling. First, the specific heat of the working fluid has to be set to 
1.007 kJ/kg.K as the device is cooling air, not water. Second, Type92 is 
really intended as a liquid cooling device. As such, it does not 
calculate the impact of humidity. You have started out correctly by 
passing a humidity variable around the cooling device and then 
reconnecting it at the outlet. However, you need to pass the absolute 
humidity ratio, not the relative humidity because relative humidity 
changes as soon as there is a change in dry bulb temperature, even if 
there is no change in moisture content. Pass the absolute humidity ratio 
from the fan to a Type33 psychrometrics routine. Pass the outlet 
temperature from the cooling device from the Type92 to the Type33. This 
isn't quite right either because in this case, you are assuming that 
there is no condensation of water out of the airstream as it is cooled. 
In almost all cases, there would be some condensation and as a result, 
some dehumidification of the air as it is cooled.

Best,
  David


On 10/30/2012 01:41, Michael Diekerhof wrote:
> Dear all,
>
> in my masterthesis I am trying to connect a heat pump (type401) to a 
> buffer storage and then to type 56. But the first step was to change 
> from energy rated control to temperature level control; so I followed 
> the TRNSYS tutorial. But somehow the indoor air temperature (kitchen) 
> is not controlled at all. I´ve checked it twice and as i can see i did 
> everything exactly like the tutorial explained. As long as I am not 
> able to control this temperature around 20°C I shouldn´t think about 
> implementing a heat pump and a storage.
>
> I attached the project and the bui.file and as you can see the heating 
> is on and especially in the cold months (e.g. january) the room 
> temperature is abnormaly high.
>
> I am very thankful for any suggestion how to control the T_Air_Kitchen 
> around 20°C ! I have no idea what could be wrong right now and at my 
> university there´s no one who has experiences with TRNSYS. So thanks 
> in advance!
>
> Best,
> Michael
>
>
> _______________________________________________
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> TRNSYS-users at 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 at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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