DIFFUSERS FOR COLD AIR DISTRIBUTION 4

[VEEKRISH]

Could some one please advise me on the type of Diffusers / Grilles to be used for an air-conditioning project involving Cold Air Distribution.

Just to clarify, we would be using Supply Air at 45 Deg F leaving from the Coil. Room Temperature will be 75 deg F. We are looking at temp deiff of 30 Deg F.

Also we are proposing this in India. Outside Ambient can be in the range of 95 Deg F DB with Coincident WB of 83 to 85 Deg F. This is just for info.

Also please advise if there is any need for insulating the Terminal (Diffusers).

Any advise / Suggestions will be appreciated.

VEEKRISH

 

[walkes]

See the following website:

http://www.price-hvac.com/html/index.asp

See the online catalog in section E, there you will find a description of various low temperature diffusers. They come with foil face insulation. There is also some engineering information available for designing low temperature applications.

 

[HVAC68]

http://www.acutherm.com/download/Fm80-35.pdf

http://www.barcol-air.co.uk/variable_air.htm

HVAC68

 

[ChasBean1]

Supply at 45°F is too cold for your ambient weather conditions. Dew/mold problems are likely in spots.

Diffuser and grille types are secondary to many other concerns (overall building pressure, control scheme, presence of reheat, etc.). Much more information is needed to get valauble assistance.

 

[SAK9]

I second CB's view point.Your diffuser will be an ideal candidate for condenstion to develop.Air conditioning loads are seldom accurate.Further design loads are seldom reached.This would result in high RH scenarios leading to condensation at the diffusers.

Further such a large temp differential would result in very small air exchange rates in the room leading to cold drafts and discomfort.

I would strongly recommend a detailed study before attempting this.Is this idea driven by energy conservation?

 

[quark]

I share the same ideas as that of CB and SAK9. Is the idea to go for low supply temperature to offset the cost? Even with a very comfortable 75F and 50%RH, the DP will be 55F and there will be condensation during low loads. There may be frosting on the coils and subsequent inefficiency during low loads.

Your trade off, for low volume flowrates, can be stratification.

 

[cme]

AFAIK, for low temp systems, series fan powered boxes are usually used.

 

[friartuck]

I've measured the leaving air temp of some air con cassette units. They can be as low as 8 or 9 C (45F).

If the air is distributed properly you can get reasonable room conditions. I wouldn't normally put air through a ducted system as low as this though. The only grille I would try it with is a plastic swirl diffuser (Try Schako)



Friar Tuck of Sherwood

 

[lilliput1]

Check with Tuttle & Bailey their Agitair RC ceiling diffuser & Agitair DQM (Dependable Quick Mixing) wall register line. Also their G Series registers.

Don't forget to add fan heat gain and duct heat gain to the cooling coil leaving air temperature to determine the net supply air temperature to the room & corresponding supply air CFM.

You may also consider using normal typical AHU leaving air temperature but using the colder chilled water at higher temperature rise, without having to replace the cooling coil. You save on pumping energy & pipe sizes but not on air distribution.