SHF, First let me apologize in advance for the following attempt at humor, you didn't have to set me up so well.
SHF asked: Any ideas on hair-to-air heat exchangers?
No, not really but I've seen a lot of AIR-TO-HAIR heat exchangers. We have a couple, they are really convenient in the winter when you would regret going outside after a shower without drying your hair.
Sorry, couldn't resist... Now then, to business.. YUP, air to air heat exchangers are at the heart of the balanced heat recovery ventilator I refered to a few posts back. They come in essentially two flavors, one is a strictly heat recovery unit that deals with sensible heat and the other works on humidity as well (also working with latent heat). This later version is more expensive but if you have significant humidity in the summer where you live and run AC and or dehumidifier then it is something to look into. AC and dehumidification is expensive/energy intensive. HRV (Heat Recovery Ventilation) with humidity handling is a way to get fresh air without throwing away the expensive cool dry air that you have generated.
I like to think of myself as something of a pretty fair DIY kinda guy, having made my living for an extended period of time as a consultant in general scientific applications in areas as diverse as using reversable heat pumps for hot and cold therapy on human patients (prototype testing was done on the San Diego Chargers football team), vacuum deposited anti-reflection coatings on aircraft instruments, portable battery operated arc welders, moving message signs, ultraviolet blood analysis machines, aircraft anti-collision strobe detector systems, encrypted radio communications devices, and on and on B U T I have no idea how I would be able to build an acceptable balanced HRV for less than buying a mass produced commercial unit. In the olden days I built kits. Electronic stuff, radios, computers, instruments, amplifiers A N D scratch built some fairly sophisticated stuff but typically and in general I made something like $0.05 per hour while assembling a kit and sometimes less while scratch building something. If the "something" hadn't been done before then it is called an invention, prototype, or both and might have meaningfull commercial significance. Somehow I think we are a bit late to jump into HRV technology and would be better off to buy rather than build. If however you think that an "Earthship" in its most complete form with water resource recycling etc, is the finest expression of architectural and environmental perfection yet created by the hand of man, then bless you my son but read no further, it wouldn't help you.
You have to have fresh air to be healthy and comfortable. Remanufacturing it is very costly so it is usually pulled in from out of doors. You have to throw away as much stale air (stale but expensively cooled and dehumidified (filtered too in many cases) as you introduce new air. If the outside air is hot and humid the expense of cooling and dehumidifying a stream of fresh air is not small compared to the cost of maintaining a cool dehumidified interior with no air changes. The trick is to change the air as much as you need but not get totally carried away A N D to not throw the cooling and dehumidification away with the stale air. The heat exchanger in the HRV efficiently cools the incoming stream using the cool in the outgoing air. Similarly the drier outgoing air is used to dry the incoming humid air (with little or no mixing of the two streams).
If the cooling and dehumidification loads are not trivial and there is a significant fresh air exchange rate then it is probably cheaper to run the HRV with humidity (latent heat) control than to cool and dehumidify the incoming air stream. Look for models with automatic defrosting for the winter time and for multi-speed if not variable speed (prefered) operation. You don't need to run it full bore when there are only two people in the house and they are sleeping but with a party going on you might want to crank it up.
Car radiator with cold water in it and a fan blowing through it???? I suppose if it were a radiator with brass tanks that could be polished or from an antique car and so forth it could be an interesting conversation piece. In a prev post I mentioned a kick space mounted fan coil hydronic unit for an under cabinet mounted heater that the mfg would modify for cooling by the addition of different pait and a drain for the condesate. That is essentially a radiator (air/water heat exchanger) with a fan. They would of course leave out their temperature control junk as I would cotrol it differently. These units would be distributed around the living spaces, mounted high in the walls where they will naturally intake some of the warmest air available and blow out cooled and dehumidified ait. One little detail is that there has to be a condensate drain line from each fan coil unit. This is essentially distilled water and could be discharged out doors instead of into the septic system. Anything that can go wrong, will, and at the worst possible moment so I would install a connector in the condensate line at each unit to permit "blowing out" the line. Over time, I would expect dust, bugs, etc to clog the drain so this "self defense" posture with the drain cleaner blow out provision should save a lot of grief.
Evaporative air conditioner/cooler. You sure know how to hurt a guy. I have one on the roof of my camper in addition to the regular mechanical refrigeration unit. It uses about 5-6 amps at 12 volts. Since in good sun I get 12-14 amps at 12 volts from PV on roof, I prefer to run it on sunshine than to run the propane generator to power the regular unit. Unfortunately, I have yet to find conditions anywhere in the midwest where there is simultaneoulsy enough sun to power the unit with rel humidity low enough for it to work.
AKA "swamp boxes" or "swamp coolers" they are essentially a fan blowing outside air through a wet "filter" pad. As water evaporates it absorbs heat (gets cooler) . It humidifies the air as well as cools it. Not what we need, more humidity around here in summer. In drier climes, say for instance Arid-zona or New Mexico where the relative humidity can be quite low while the air is very hot, they work well, cooling and humidifying for a fracton of the cost of "regular" mechanical AC.
Last coment on the build-buy decision. Do you fly commercial? I do. I'm a pilot. When I fly a gen aviation plane on a long x-country it is for the flying fun, the trip, not getting there. To get there expeditiously and economically with a serious amount of bagage, I go commercial. Much of the HVAC stuff is like that. I may do a lot of the design and the installation labor but it is unlikely that I will build much of the equipment. I also don't usually build my own nuts, bolts, or screws.
Patrick
