I have a portable air conditioner similar to the one in the picture below. I want to direct the output flow through a small duct system to the feet of people sitting on a large table. Can I just tape a large fabric funnel on around the blades of the unit and into my duct system?
The manufacturer would clearly say no! His blower is designed to deliver air into an unobstructed space. The squirrel cage blower wheel in the standard furnace is designed altogether differently. It is designed to push against back pressure. The blower in this type of unit is not designed to do that.
Additionally, you will knock all of the design parameters out of wack. You could dramatically shorten the life of the compressor. You will definitely loose all of your warrantee coverage.
An accepted solution would be a through-the-wall fan to move the cooling to another room, preferably placed lower on the wall. Or use a breeze box set in the discharge path of this unit, not too close, to augment air flow to the immediate area.
The machine is designed to be ducted in the exhaust side. Extend that duct and place the machine closer to the area you want cooled.
Makeing a duct would work to channel the air to a specific location however there will be some efficiency lost but the underside of the table would be directly cooled.