bring in outside air with out the out side humidity

Because the rising air temperature drops below the dew point at that altitude.

Hmmm hmmm - the closest thing to what you want is the counter-current heat exchanger, where incoming cold air is warmed by outgoing. Or in summer, the reverse. It is theoreticlly possible to do this with moisture, but you'd need a barrier permeable to water, so that incoming air loses it's water to outgoing, dryer, air. You certainly could pass incoming air through a duct where the dehumidifier dries it.

Actually, there are a couple of schemes for this.

One uses cardboard, yes cardboard, for an air exchanger. Outside air is sucked in via one direction of the cardboard, while the inside air is exhausted along the other direction. Assuming your inside air is drier than the outside air, then some of the moisture in the air, as well as the temperature of the air, passes through the cardboard. It basically tries to moderate the temperature and humidity changes...

Charlie

O2: 16+16 = 32 N2: 14+14 = 28 H20: = 14+1+1 = 16

so when a molecule of H20 replace any of the main components of air, the air gets lighter "

WOW. Of course you are talking about the vapor at the same temp and pressur e as the "air". Good, I learned someting today. now ow to apply it is beyon d me. All I know ids I DO have a plan that can balance one central HVAC uni t for heating and cooling on two floors. That's the besy I can do and 90 % of the contractors out there have zero clue on how to do it.

But the dry air, heavier. you wouldn't say yhtat shit if it was bullshit sd o I am not looking it up right now, this is one of those facts that while i t doesn't prove anything, it also doesn't disprove anything. At least not r ight away.

Hotter air is less dense and could hold more water, and yet when it does ho ld more water it still tends to convect up. OK, I guess I think I got it.

Just never thouguht of it like that before.

sucked in via one direction of the cardboard, while the inside air is exhausted along the other direction. Assuming your inside air is drier than the outside air, then some of the moisture in the air, as well as the temperature of the air, passes through the cardboard. It basically tries to moderate the temperature and humidity changes... "

Sounds like a maintenence monster.

Yeah, constant is the right word. But no one cares what the due point is in a weather report. They care about the relative humidity because that is what you feel. Raise the temperature a bit while adding some water and the comfort level is about the same because the relative humidity is the same. Lower the temperature without changing the water content and you get a higher humidity so that the air will feel sticky and damp - people will complain about how uncomfortable it is.

I believe there is an index that takes both humidity and temperature into account, but I forget what it is called.

I would like to try some of what you are smoking... ;) I don't think you will find a difference in air pressure enough to make a noticeable change in the dew point or humidity.

Not true. Air is mostly N2 (molecular weight 28) with about 21% O2 (molecular weight (32). Water is H20 (molecular weight 18). The other significant component is 0.93% Argon (molecular weight 40).

Oops.

refrigerator to lower the air temperature, which causes the air temp to go below the dew point, which condenses that water. Commonly used in pneumatic tools.

Hilsch tubes do seem to be a bit mysterious, but they do work, if inefficiently.

te:

idity with it?

ut the temperature but I don't want to make my dehumidifier work over time !

in outside air?

me that would simply make the air very wet?

e water and when it got to a certain level it can drain off. At this point I am thinking that maybe the moisture would stay below the oil and collec t in the water?

t exchanger, where incoming cold air is warmed by outgoing. Or in summer, the reverse.

rrier permeable to water, so that incoming air loses it's water to outgoing , dryer, air.

er dries it.

A dehumidifier works by refrigerating the air, so that the water vapour mos tly condenses out. They are usually set up as counter-current devices, so t hat the incoming air warms - and is cooled by - the dehumidified air as bot h pass through a heat-exchanger in opposite directions.

Comfort factor ...Jim Thompson

ostly condenses out. They are usually set up as counter-current devices, so that the incoming air warms - and is cooled by - the dehumidified air as b oth pass through a heat-exchanger in opposite directions.

Minor nit. Most dehumidifiers cool the air and condense the moisture and t hen blow the cooled dry air over the condensing coils. That may be what yo u described, I just could not picture what you said.

Dan

Due point?

Accuweather calls it "Real Feel" (but adds wind).

Ground-level air pressure varies a few percent from 1 bar. A two-story house, heated in winter to 20 C, in freezing weather (0 C) must have different air pressure from the outside of maybe 50 microbar. So yes, the effect is very small on a house-size scale. One cannot ignore it, though, when prevailing winds push air up a mountain slope (and there's a rain forest a few hundred miles from here to illustrate the point).

I'm sorry, I don't follow. Why does the air pressure *have* to be different inside and outside a house?

It uses *very* high quality cardboard... ;)

But the point is right. They do make heat exchanging air intakes that bring the temperature of the incoming air close to room temperature while getting that heat from the inside air being exhausted. Of course this is an expensive gadget compared to the cost of heating and cooling the air. It takes many years to pay for itself, but they are cost effective in the long run. Just like in the long run we are all dead.

I'm not sure why you compare this to cold fusion. This seems to be based on reasonable science. No magic, just a membrane permeable to water molecules and not air, a sieve if you will. It still uses energy and doesn't violate any laws of thermodynamics. It is just more efficient than conventional AC. Notice they don't talk about heat though. Most houses around here use heat pumps rather than just AC. They would then need something else to produce heat if they used this membrane device.... possibly a heat pump or possibly a conventional fossil fuel furnace.