[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [TRNSYS-users] abnormal fluctuation of cooling

Yujun,
  I am not sure that there is anything wrong with the simulation; you have 18 airchanges per hour of ambient air that is somewhere between 16 and 21C going into the space and that is keeping the zone temperature below 26C when the cooling would turn on. If you switch off your natural ventilation by multiplying the equation by zero, you'll see that the space gets up to the cooling temperature every day.

 You should probably multiply the zone capacitance by 5 or 10. The value that you have for the zone accounts only for the thermal capacitance of the zone air (it ignores the capacitance of all the other things in the zone like shelving, products, furniture, etc.). You should also set the humidity capacitance multiplier to a value of about 5 to account for the furniture's capacity to absorb moisture. Lastly, I think that a 1 hour timestep might be too long. Bear in mind that the decision to activate or deactivate the natural ventilation system can only be made once per timestep. The fact that the natural ventilation is on for one time step, then off for one time step, then back on for a time step suggests to me that the system isn't very stable.

Best,
 David


Yujun TAO wrote:
Hello,
I simulated a cooling commercial with a natural ventilation, the natural ventilation is modeled in a equation.
I don't understand why there is abnormal fluctuation of Qcool curve and the temperature doesn't reach 26 degrees.
I feel it maybe concern the equation.
Could someone help me? 


_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@cae.wisc.edu
https://www-old.cae.wisc.edu/mailman/listinfo/trnsys-users
  

-- 
***********************************************************************
Thermal Energy System Specialists (TESS), LLC 
David BRADLEY                      22 N. Carroll Street - Suite 370 
Partner                            Madison, WI 53703 
                                   USA
P: +1.608.274.2577 
F: +1.608.278.1475
E-mail: bradley@tess-inc.com 
Web Pages:  http://www.tess-inc.com    and      http://www.trnsys.com

***********************************************************************