[EnergyPlus_Support] Adaptation to sensible load variation of the object Coil:Cooling:DX:singleSpeed

["aymericnovel" <aymericnovel@xxxxxxxxx>]

Hi,
I have simulated a 90m² apartment in HoChiMin, vietnam. This is my 
first study in such a humid climate so I apologize if my question is 
trivial. Here is my problem:

I use the SingleSpeed DX coil in each cooled zone to simulate a split 
system.
It recirculates only room air. The temperature setpoint for zone is 
26°C.
My study aimed to quantify benefits on cooling energy consumption of 
actions on the envelope (use of insulating concrete, low SµHGC 
windows) and reduction of lighting related internal loads. So far, 
very logical.

And logically, I found that my sensible loads are reduced (about 30%).

But, the DXCoil adapts to a lower sensible load by blowing less air 
at the same temperature. For an idea here are the 2 configuration at 
the air outlet of the coil:
High sensible load => 0.08kg/s at about 13.5°C
Low sensible load => 0.05kg/s at 13.5°C

Logically, in the second case, the sensible cooling rate delivered is 
smaller, according to the fact sensible load is indeed smaller.
BUT, the latent load increases accordingly. The SHR (Sensible Heat 
Ratio) decreases in the second case, making the latent part bigger:
High sensible load => SHR = 0.7
Low sensible load => SHR = 0.6

So, when looking at the result on the total cooling rate, it is not 
as fruitful as expected...I guess it is a known fact for engineers 
who are used to work with high outdoor humidity ratio

Is it because the coil is "single speed" that the regulation is 
automatically made by airflowrate? Is there a way to modify the blown 
air temperature instead? Indeed, that would create energy savings 
also on the latent part to blow the same airflow rate at a higher 
temperature if sensible load is increased? Isn't that the tenedency 
of current evaporator to increase SHR? Should I change the object I 
use? I guess it is all related to "how the object calculates the 
blown air temperature"...

If somebody could help me clear my mind on this topic, I would be 
grateful!

Tnaks a lot,
Aymeric







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