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Re: [EnergyPlus_Support] DX cooling coil runtime fraction?
Because the performance of the DX coil is frequently non-linear, the air conditioner model must call the DX coil model several times (iterate) to determine the proper run time fraction to meet the zone load. The cooling convergence tolerance is the error tolerance used to terminate the iteration procedure when the following equation is satisfied:
(QZoneLoad- Q Window AC out )/(Qzone Load) < CoolingConvergenceTolerance
The maximum number of iterations is currently limited to 15, with a warning message generated if the above equation is not satisfied within the maximum number of iterations.
Also while iteration say the first guess value may be 1 then the next will be zero to get the bounds in which the answer exists then it reaches upper bound of say 0.8 then the next lower bound is 0.2 so the anwer is between 0.8 and 0.2. this continues till convergence is reached.
Thanks
Rahul Chillar
zhaicq98 <chaoqinz@xxxxxxxxxxxxxx> wrote:
Hi,
I have a question about the output object: DX cooling coil runtime
fraction. I output the data using detailed output mode. I specify the
timestep is 10 minutes in my simulation. When I look at the results,
sometimes the output is for each minute. To my understanding, this is
related to the convergence of the simulation. Am I right?
What surprises me is that during the short timestep (1 or 2 minutes),
the runtime fraction of the DX coil varies a lot. For example, for
the previous minute, it could be 0.9. Then next minute, it becomes 0.
Then next minute it is 0.5. I have no idea how to interpret these
data.
Thanks!
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Thanks
Rahul Chillar
Grad Student
Building Systems lab
Univ Of Illinois Urbana Champaign
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