[TRNSYS-users] Psychometrics problem

[David BRADLEY]

Michael,
   Fans (and pumps) in TRNSYS set the downstream flow rate based on the 
input control signal and the rated flow rate parameter. They use the 
input flow rate only to check the fan mass balance. If you have 0 kg/h 
of air entering a fan because of the connections that you've made and 
the fan's control signal is set to 1 and its rated flow rate is 1000 
kg/h then the fan will put out 1000 kg/h of air and log the time step as 
having a mass imbalance. Sometimes this is not a problem; for example if 
you have a fan that is blowing air from ambient into an air handler or 
into a building. You don't really care how much air is going into the 
fan and you can either ignore the warning or connect the fan's output 
flow rate to its input to suppress the message. If you have a supply / 
return system then it is probably more important to make sure that flow 
is balancing around the loop. Use a type65 and plot the flow rate out of 
each device in the loop. Make sure it all sums to the fan's outlet flow 
rate.
Best,
  David


On 12/4/2012 01:21, Michael Diekerhof wrote:
> David,
> thanks for this fast reply. Since I connected the pressure as well 
> (don´t know how i could miss this) there are no more warnings due to 
> psychometrics. Just at the end there´s one warning left, which doesn´t 
> sound good:
>
> /*** Warning at time       :      8760.000000//
> //    Generated by Unit     :     6//
> //    Generated by Type     :   112//
> //    Message               : Fan mass balance failed during 35040 
> timesteps. Please check the connections./
>
> Do you have any idea what in detail could be wrong ? I made the 
> connections for dry bulb, humidity and pressure.
>
> Thanks in advance!
> Best,
> Michael
>
>
>
>
> Am 12/3/2012 6:39 PM, schrieb David BRADLEY:
>> Michael,
>>   You need to connect the pressure as well. It is surprising that you 
>> always get the warning. I would understand if you get that warning 
>> for some timesteps (maybe even enough timesteps to go over the 
>> allowable number of warnings in a simulation. However, if you get 
>> that warning at every single timestep, there might be something else 
>> wrong.
>> Regards,
>>  David
>>
>>
>> On 12/3/2012 05:39, Michael Diekerhof wrote:
>>> Dear all,
>>>
>>> I´m using type 112 as a fan for an air-Source heat pump (type401).
>>>
>>> Between Type 15(weather) and type 112 i made the following connections:
>>>
>>> Dry bulb temperature => Inlet temperature
>>> Humity ratio => Inlet air humidity ratio
>>>
>>> But unfortunetaly I do always receive the following warning which 
>>> results in an Error:
>>>
>>> /"The referenced UNIT has called the PSYCHROMETRICS routine witha 
>>> humidity ratio above the saturation humidity ratio for the given dry 
>>> bulb temperature.
>>> /
>>> /The air was assumed saturated at the given dry bulb temperature and 
>>> the humidity ratio set for this condition/"
>>>
>>> Does anyone has a suggestion to solve this problem ?? I appreciate 
>>> any idea :)
>>>
>>> Best,
>>> Michael
>>>
>>>
>>> _______________________________________________
>>> TRNSYS-users mailing list
>>> 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
>

-- 
***************************
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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