Question-and-Answer Resource for the Building Energy Modeling Community
Get s tarted with the Help page
Ask Your Question
1

drop in absolute humidity when using HVAC:Template:Zone:PTAC

asked 2017-11-15 10:22:33 -0600

hullaballoo gravatar image

updated 2017-11-15 13:39:36 -0600

Hi everyone! I am simulating an existing building with a cooling split unit, using HVAC:Template:Zone:PTAC with a SingleSpeedDX with no dehumidification unit added. However, when I look at the results, there is a huge drop in absolute humidity indoors compared to outdoors (about 10g/m3). Can anyone explain me why or how can I avoid that?

Thank you in advance!!

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted
2

answered 2017-11-15 10:29:18 -0600

A DX cooling coil removes both sensible (temperature) and latent (moisture) energy from the air stream. Water cooling coils also have this same property. When using a cooling coil in your simulation roughly 25% of the energy transfer will be moisture. So the result will be that the indoors are dryer than outdoors.

edit flag offensive delete link more

Comments

Thank you for your answer! Do you know if there is any way to simulate a cooling unit which removes only the sensible energy and not the latent?

hullaballoo gravatar image hullaballoo  ( 2017-11-18 12:02:51 -0600 )edit

Well, I've never tried this but you could make the SHR = 1. You must ensure that the total capacity and air flow inputs result in a supply air condition that is on the psychrometric chart (i.e., outlet air RH < 100%).

Coil:Cooling:DX:SingleSpeed,
  1.0,                !- Gross Rated Sensible Heat Ratio
rraustad gravatar image rraustad  ( 2017-11-20 07:46:09 -0600 )edit

Thank you now it works just fine!!

hullaballoo gravatar image hullaballoo  ( 2017-11-24 12:10:09 -0600 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

 

Question Tools

Stats

Asked: 2017-11-15 10:22:33 -0600

Seen: 72 times

Last updated: Nov 15 '17