tower and coil space cooling

[mobile_bob]

digging around i found reference to interior cooling systems used prioer to about 1930 and came across
a reference and basic description of the operation of what was known as "tower and coil" cooling

the cooling tower was used to remove heat from the return water , the cooled water was pumped into
what at the time was typically truck radiators inside the space to be cooled and fan move the hot interior
air through these radiators.

the radiators took heat from the interior air thu cooling the space, the hot water coming off these radiators
was returned to the cooling tower where the circuit is completed and the process starts over.

in hot dry desert southwest these systems apparently worked amazingly well, keeping the interior temps
down to very bearable limits even while over 100F outside, the inside could be down well into the 70's F range.

if anyone has any info on these systems, or any book titles, links or anything let me know, as i am very interested
in cooling systems that use the cooling tower methods.

bob g

[Ronmar]

I would imagine the cooling tower had water sprayed on/in it.  I don't see 70F from 100F ambient without some evaporation.  Basically a swamp cooler without the added humidity...  Then you get the associated scale and corrosion associated with water chemistry/minerals.

[mobile_bob]

yes it was an evaporative process

and the water that made the loop form the radiators inside went into a loop in the bottom of the tower, to reject its heat
and then it would be pumped to the top of the tower and sprayed down into the tower over what was probably at the time
excelsior (wood fiber mats) much like a water cooler, but as you state without the added humidity in the house.

i would suspect that annually there would have to be some maintenance, the make up water would likely need to be demineralized
or use rain water, otherwise some sort of acid would have to be ran through the tower to clear the scale , followed by neutralize
and flush.

there is another system, that i came across that was really fascinating basically two units built into one housing
wherein one section was a water cooler, and the cooled water was then fed to the other section which had the heat
exchanger and air handling fan to duct in inside air where the heat was removed and cool water returned.

it used a single motor with double shafts and double squirrel cage fans, one for the cooler side, one for the air handler side.

that system looked as though it would do much the same as a cooling tower/coil unit, but do it in a smaller more compact unit.

my thinking is this, if such a unit could take a home from say 100F, down to even 85 degree's  economically,  then a standard airconditioner
system would have much less work to do taking the room down from 85 to 70 degree's.

from what i have read many of those systems were able to keep the space cooled down into the 70's, so even if it got it down to 79F
a relatively small A/C could then be used to knock down the last 7 or 8 degrees.

it is reported that these systems fell out of favor as electricity became more widely available and the new freon/compressor A/C came available
electricity was so cheap and the cost of a compressor unit although expensive was far less work to keep operational, they didn't need the tower
serviced or have connection to a good source of water.

since about 1985 the use of some of these old technologies have started to catch the eye on larger installations, most especially because that is where cooling towers are commonplace and fairly well understood.

for me i am interested in the design considerations and how they scale to smaller sq/ft buildings.

i know from experience a building with enough thermal mass that is cooled to around 65F overnight will manage to temper the interior temps through the heat of the next day, allowing interior temps to remain below 80F even though it can be over 100F outside.  therefore an understanding of how towers are designed, would allow a source of cooling for the thermal mass below that of the overnight average temperatures for the area of operation.  from what i gather it is not difficult to get a water temp 10 degrees below ambient having gone through
a tower, and that would assure the interior thermal mass could be even cooler to start the next day with.

i am very interested

bob g

[Crofter]

That type of cooling for human consumption has some problems. Do a search on "Legionnaire's disease" It relates to respiratory infections that led to a bunch of fatalities at a convention and the source was eventually traced to the air conditioning. There are also cautions on contamination growing in hot water tanks where the temperature is held low to save standing heat loss.

No doubt that some kind of bio lethal chemical could be maintained that could keep the ickies from breeding but I am not sure what it would be. I have seen some treatment injection systems on industrial cooling towers but that was just in passing. Seemed like an alcohol odor but that might have been as a wetting agent or off the breath of some of my buddies, Lol!

[lowspeedlife]

Legionare's disease was caused by the failure of the maintenance company in the affected building to properly maintain the air conditioning system. the drain pans in the a/c systems were not cleaned properly allowing condensate water to stand in the pans, with the air that blows into the air conditioned space, blowing across the contaminated water, picking up the microbes & blowing them into the air in the building. Having the drains cleared to allow the condensate water to drain would have eliminated the problem, but now days they also use a small tablet, enclosed in a plastic pack , that slowly dissolves & kills the microbes. Can't remember what the chamical is, likely a form of solid chlorine bleach. In Bob's scenario I don't see this as a problem since thier should be very little, if any condensate to collect. And if thier is, the little tablets are really cheap. The water in the cooling tower will need to be treated to keep corrosion down but with the right test kit & chemicals it's easy to do.


  Scott R.

[vdubnut62]

A little copper sulfate would kill the bugs wouldn't it?  I don't think it's terribly corrosive, could be wrong.
Ron

[LowGear]

RERead lowspeedlife's contribution. 

[Ronmar]

And that was the point of using the cooling tower is to keep the wet of the evap/cooling tower outside.  Any fancoil unit inside, that moist room air circulates thru for cooling, will condense moisture out of the air. Just like the evap in any A/C system does. This condensate must be dealt with, just like in any A/C system.. 

[Crofter]

I see from re reading Bobs post that the heat exchangers should isolate the air exposed to cooling water. The less you have to treat the water, the less problem there is with corrosion and the less you have to worry about electrolysis or scale . No question the air moving through a water fall is good heat sink but what is the cost / benefit compared to using the earth mass via under ground piping which can be used the other direction to supply heat in winter.

[LowGear]

It seems to me that the condensation would take place in the cooling area where there aren't people.  People are in the warming area where the heat is being transfer from.  Nope, that's wrong.  Obviously its a little fuzzy to me.  The part that isn't stated yet but jumps out at me is the impact of accelerated processes brought on by the introduction of compression in modern refrigeration units.

Here's my ignorant question for this thread.  Does the heat migrate or does the cool migrate?

Casey

[Crofter]

Here I think there is potentially condensation in two different sides of the system. The wet side where the heat is dissipated and also when the cooler water is circulated through the occupied space there may be condensation on the other side of that surface as the warmer humid air gets cooled. As has been pointed out that moisture is what really must be contamination controlled as in any air conditioner.

Maybe it could be made into a quiet enough and small enough and service free enough system for a residence. It would of course have to be able to be decommissioned for winter. The amount of refrigeration BTU has to be weighed against the energy cost of continuous water pumping and running fans. On a small scale it might not pay much dividend for what is involved.

Industry would prefer to just dump their waste heat into a river but I think they do the cooling tower thing because they are forced to. Any I have been around are noisy.

[Ronmar]

A well designed cooling tower dosn't need a fan, just a spray of water.  Used to drive by a monster of one at the Trojan power plant.  Cool hourglass shape and usually a large colum of steam escaping the top. 

[Crofter]

Would the good design of such a thing not depend on the relative temperatures of the working mediums whether or not the thermosiphon effect can be powerful enough to accomplish the heat transfer desired with an economically feasible amount of structure? Some things, like the fact that the less intense the temperature differential the greater the area necessary to accomplish a given heat transfer; same thing for velocity. Trade offs can be made here to some extent but none of the effects can be forgiven. Some things dont scale down well either as ratios of area and volume dont stay the same.

Perhaps the calculations could be done using the figures of energy available from the evaporative cooling effect and the available air temperature differentials to arrive at some areas, volumes, velocities, etc. The figures of the heat gain of the building should be fairly easy to arrive at also.

[sailawayrb]

http://www.thefarm.org/charities/i4at/lib2/aircool.htm

http://www.wbdg.org/resources/naturalventilation.php

Been considering designing one for our passive solar house.

Bob B

[deeiche]

rm /