Date: Mon, 15 Dec 1997 16:12:33 +0000 From: Lance Jerale <ljerale@valders.k12.wi.us> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg4727$foo@default> Subject: Re:Xerophytic Nepenthes?
Perry Malouf writes:
> By the way, ambient relative humidity is not necessarily what the
> plant is exposed to, depending on how sheltered it is from
> drafts and whether it's kept over a pan of water (or other source
> of moisture).
This may be true. I hang my cheap hygrometers right IN the plant itself. I
believe that this is as near as an amateur can come to getting an accurate
RH reading for a particular plant. What the instrument hanging on the
wall tells you may be another story, however.
>
> Further on the subject of humidity, I've noticed some people referring
> to the outdoor relative humidity but they keep their plants inside.
> The outdoor relative humidity is often reported during news
> broadcasts for the area.
>
> There can be a big difference between the relative humidity outside, and
> the relative humidity inside a house. Say it's 30 F outside and the relative
> humidity is 50%. If the HVAC system in your home has a furnace with no
> humidifier, then it'll heat the air without adding moisture. Air at 30 F
> and 50% RH, when heated to 70 F with no moisture added, has a very low
> relative humidity. I haven't done the calculation--I estimate it's
> around 10% RH. Of course, any moisture in the house (adsorbed to the
> walls, etc) will come out into the air and modify the RH somewhat.
Right! Warm up a body of air without adding moisture to it, and the RH
drops. Outside and inside RH will only rarely be the same.
>
> Air conditioning, on the other hand, condenses moisture out of the air.
> If it's 90 F outside with RH of 70%, the air conditioner might cool
> the air inside to 70 F. If that's all it did, your house would be a
> swamp because the RH would jump to 100%. But since water condenses
> out of the cooled air, the RH doesn't skyrocket.
Not necessarily correct, I think. Some systems, if I understand such
things correctly, neither add nor subtract moisture from the air. They
only cool the body of air as it is. With this type of system, as the air is
cooled, the RH rises. In these systems, a cool room can feel very muggy, as
RH MAY approach 100%. In another type of system, the kind most of us
know and appreciate, moisture is actually removed from the air that is
being cooled, just like in a dehumidifier. In this system, water does indeed
condense out of the air-- onto cool parts of the air conditioner, where it's
then removed. In this second, obviously more desireable type of air
conditioning, air is not only cooled, but also dried-- by the machine itself.
This avoids the muggies. This is probably what most of us understand by
"Air Conditioning".
I ran into a problem with the first type at the University of Ontario at
London a few years back. I was giving a presentation about my
electrostatic generators to the Electrostatics Society of America. I tested
them in the lecture hall before the "air conditioning" was on, and in hot,
uncomfortable weather I was able to make big sparks, and everything
worked fine. I figured that once the AC was on, DRYING the air, my
machines would REALLY perform. All they did was cool the air without
removing any moisture. No drying effect. Unknown to me, RH was steadily
climbing. When it got to be my turn, all my spark machines did was make
noise. NOT one of my shining moments. Imagine a cool muggy room! :-(
This type of system may be of use by Nepenthephiles growing highlanders!
(And some of you thought I was off topic! tsk, tsk!)
Have Fun,
Lance
-- ---------------------------------------------------- ---------------------- Lance F. Jerale 414-775-9520 voice 414-775-9509 fax ljerale@valders.k12.wi.us Valders Middle School Valders WI 54245
This archive was generated by hypermail 2b30 : Tue Jan 02 2001 - 17:31:16 PST