If it is, it would probably help to some very small degree.
But since most towels that are on a rack are NOT within the main air stream.
Or do you wish to argue that point too?
Why would the towel have to be in the air stream? Water vapor (like basically everything in nature) moves from higher concentration to lower concentration. The increase may be small, but is there. Bison is trying to point out that there are many ways to add humidity, but not all methods are a smart way of doing it.
There are various configurations of humidifers...in-line and bypass are the two more common as I see it. Steam doesn't seem to be that common on residential units. An in-line one works best in the air duct after the heat exchanger. A bypass unit needs to have the inlet and outlets in different pressure regions of the ductwork so that air is moved across it. If you can put one end after the heat exchanger and the other side before the fan, it would be the most efficient, but as long as there is a pressure difference between the two sides, some air will cross through and pick up moisture. There are lots of places in a typical system where you can tap in to do a bypass, some are more efficient than others. Same is true with an in-line system, but the thing could even be put in the cold air return and still insert moisture...it would work better in the output because the heated air can hold more moisture. In this case, it may not need to run as long and be able to satisfy the demand quicker.
To help keep stratification down, I run my variable speed fan constantly, which also enables the humidifer to work. It's a Trane air handler, and when not calling for heat or a/c, the fan runs on speed 1 of 16, so you don't hear it and the power draw is minimized at the expense of increased wear. It'll die one of these days, but has been running for nearly 15-years now.
The Poster(McNauge) said he has no heat pump, just an normal furnace with a A/C coil installed in the plenum.I have been saying that as long as the Humidifiers moistened air is introduced into the main air stream that is going to give some humidification into the home via the supply ducts. Sure there are ideal plces on the plenums or main ducts that parts of this humidifier can be installed, and then there are not so ideal places that they can be installed.So what I have been saying is IF you cannot install it in the ideal location at least by installing it in an not so ideal location at least you will get some benefit out of it at the least.
Having installed many, many various types of humidifiers over my 48 years of being in the Hvac trade, if there was no room to mount it on the return pleum, then it would be mounted on the Supply plenum. If there was no room on either of the plenums then the MAIN supply and return duct trunk would have to do . Sure, the IDEAL installation for the drum is on the return with the supply air running INTO the drum, but either of the other not so ideal ways will do as long as humidified air is introduced into the system and then sent to the various rooms of the home it is going to help increase the humidity level in the home to some degree.Maybe not as good as the best way, but if the best way cannot be achieved, then something is still better than nothing at all.
Well i have got the humidifier fully installed and it works great, only took about 5 hours to bring the whole house humidity up to the requested range.
I installed the Flow through humidifier onto the narrow side of the return plenum and the flexible bypass line to below the AC Coil about 6" below the level of the intake on the humidifier (total flex line length only 12" or so). Installed a dampner on the connection to the Supply side and soldered on a new valve on the cold water line and plugged it all in.
Works like a charm.
Thanks for the help everyone, on to the next project.