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mah_h
02-10-2014, 09:09 PM
hi guys, i need your help in understanding this topic... I'm working on a hotel (in Dubai) where all AHUs are being supplied at a supply temperature of 13.9 degree celsius then i got a comment from the hotel operator says:
" cooling coils in all AHU's must be sized for full latent cooling for dehumidification and reheat coils are installed to raise the supply air temperature to the minimum design supply off coil temperature of 16 degrees celsius to ensure no cold drafts can be experienced anywhere in the hotel."

supplying the temperature at 16 degrees it will increase the humidity in the space am i right?? is there any sub cooling to be done?
thanks in advance

Magoo
03-10-2014, 12:36 AM
Lowering air in cooling coil will increase RH%, then re-heat ( sensible heating ) will increase dry bulb and lower the RH%

mah_h
03-10-2014, 08:39 PM
thanks.. in that case they need the supply temperature to be at 16 degrees where reheat coils are used when that pre function or ballroom isn't occupied(moisture content will be more) and then when that space is occupied we need to go to the sub cooling process back to provide a supply temperature of 13.9 am i correct?

Magoo
04-10-2014, 03:02 AM
Higher heat load from a function area ( humidity will be high ) so lowering off coil temperature will remove more saturation, adding sensible heat from re-heat coil will drop RH% even more and maintain a comfortable environment with a lot of people in function area. A higher percentage of fresh air is also required to maintain oxygen levels and stop the air becoming stuffy.

Magoo
04-10-2014, 03:10 AM
check site http://www.kwangu.com/work/psychometric.htm

change any input and see changes in conditions.
magoo

mah_h
04-10-2014, 09:05 AM
thanks a lot my friend)) that was helpful

Magoo
05-10-2014, 12:16 AM
Hi mah_h
you are welcome, function centres can be a pain to manage, high loads to low loads, along with shopping malls. Use of fresh air make up and spilling return air is important to consider, usually fresh air is mostly sensible heat, latent cooling is expensive to manage.