HVAC cooling tip & Question

I don't see anyone responding so I'll take a stab at it.

How about a proportion.

35 ton gets you a 15 degree drop in temp. With the misters X ton gets 20 (for example) degree drop. therefore X = 20*35/15 = 46 ton

use psychometric chart....return air to the unit...then exit air from the unit..u'll get an accurate answer

If your unit is rated 35 ton, the problem is that the condenser coils could not provide enough naturat cooling of the freon to even allow the unit to perform as a 35 ton unit, perhaps far, far less. Then when you add misting, you have increased the cooling of the hot condenser coils and the thermal efficiency increased, perhaps approaching the desing goal 35 tons. Basicly you are merely ADDING an evaporative cooler as a "precooler" to your overall air conditioning system and making it work less hard, because it is the differential in temperature between the input-to and output-from the condenser coils that determines this efficiency. You could measure this by attaching a thermometer to the input-line and output-line of the condenser. The bigger the difference in temperature drop, the better the system is working.

A parallel to this is if you are driving your car in hot weather and the heat guage goes to its high-end, then you hit a rain-storm and the radiator is misted with the rain you will note that the heat-guage goes-down.

Why?..what is the point of retrospective calculation? You've found out it works!

If some one says 'it's only a 5% increase ' are you going to remove it ? ! ?

Double:

I wouldn't question the effectiveness of the technique, but you might want to consider the mineral and sediment content of the misting water. You could be pumping a long-term mess into your condensers.

DickL

Good point DickL !!

Maybe the water should be distilled water....?

Also, are there condensers lying directly in the Sun, or are they shaded? Some extra shading may help further if the Sun is on them....a sun sail over the whole unit?

Double:

You do have one cheap source of distilled water on site, if it isn't already being used. The water dripping from the heat exchanger is distilled and could be pumped to your misters from a sump. Not exactly a new idea, but it might help.

DickL

I like that Idea hadn't really thought about it that way, but not sure if it can make it as fast as I am using it. I'll have to work that one out.

With the humidity as low as it is here right now i"m not sure that there is enough water coming off of it.

The water does not need to be distilled but merely treated with chemicals to stop scale buildup or corrosion of the coils. This could either be pumped from a storage/mixing tank as a premixed solution or mixed through an injector directly into the misters feed lines. Either way they should be monitored for correct chemical and conductivity. If the water in the storage tank becomes unusable it should be discharged.

Charsley:

That's interesting. How does it work? If mineral laden water enters a system and evaporates, how does an additive keep the mineral content from being deposited on the condenser surface?

DickL

This is equivalent to evaporative cooling and only works in an environment where the relative humidity is relatively low. Examples are the American southwest such as Nevada or Arizona. The addition of moisture in the ambient air will increse the human discomfort level in the room(s), as the relative himidity will increase. The addition of moisture in the (relatively dry) air absorbs heat (the earlier comment related to the use of a psychrometric chart is right on the money).

As others have pointed out, be very careful with scale. This trick is used in 3rd world countries to spray water on radiators of generator sets. Within a short time they overheat from scale deposits. No worries, they then spray down the entire engine. Pretty soon I need a chipping hammer to change the oil filter.

A few hundred microns of scale will insulate VERY efficiently (transfer goes way down now) and eventually will build up to a few mm and totally block air flow (no transfer).

I live in the desert where water is expensive so be careful of the 'total life cycle cost' including water bill, chemicals, maintenance, environmental (are chemicals compatible with roof material, birds, Del the Cat taking a sip from a puddle, etc.).

Before doing high fives with your boss put a 10 year vision on this.

I forgot to mention fan issues of corrosion from water (if aluminum), deposits (balance), and other nasty things.

Hopefully since I will only have to run it for about the next month or so it won't be as bad.

I am using city water currently and considering using the softened water as stated below. of possibly a filter of sorts.

Great observations one and all though.

As far as I am aware, there is not a filter that removes lime (hardness) you have to have an ion exchange water softener, that recharges with common salt.

Sorry for all the delay in responding to all these fantastic comments. But today I have my first grandson and have been tied up with that.

I understand the need for protection from scale so let me add an additional question.

Can I use the softened water that is supplying my boiler for these misters or possibly put in an in-line filter to remove deposits from the water?

Congrats on new grandson. I had my first last Sept. Fun stuff.

OK. Protection from scale on the grandson or scale on your condenser ??!!?? Dip his bottom in Lime Away every 6 months . . . . wait . . . don't do that. He'll scream like heck.

Just call your boiler chemical dude and he will recommend something. We use Diaperene and then A-D ointment on our condensers. Wait . . . I'm getting mixed up again.

Call 'Culligan' type companies and ask them the same. Those big water softener companies ALWAYS have some 85 YO guy there who likes to chat. You can't typically physically 'filter out' chemicals, but you can chemically filter them (ion exchange which is how a water softener works).

That goes right along with what Andy had to say above. I do use a water softening system for my boiler but I'm not sure if it is what your guys are refering to.

If thats the case then I will see about tapping into it to run my misters from.

It is a system that we have maintained by culligan. So if you guys think its a good idea then I will give it a go.

I am quite sure the system is not working to hard right now so I should have plenty of capacity for the additional misters.

I'm begging you to call the water experts first and 'chat'. You will learn something . . . . . I always do and I've been in the 'game' for 35 years. You will get at least one "If it were me, I'd . . . bla bla bla "

I will give the water guys a call.

Thanks!

My understanding is that the usual minerals, calcium, magnesium, etc. are replaced by sodium in those systems. Sodium is VERY reactive with water so it probably wouldn't remain in its elemental state. That still leaves you with solids on your heat exchanger surfaces.

DickL

Misters are going to wreck your condensor. You will be able to optimise the effect by installing a evaporative cooling panel as used in evaporative air-conditioners. Munters who make the cooling filters actualy market a product for this purpose. I have made and installed similar ones in both high and low humidity areas in Southern Africa. Even high humidity areas do not have full time 90% R/H so they work. Of course the lower the R/H the more efficient. One building showed a 27% cut in power useage. You will have to "run off" a lot of water to prevent sludge and salinity build up. We run it into resevoirs to use in grey water applications like toilet flushing and gardening. Your HVAC engineer should be real mad with you at the reduction of maintenance costs as well. This is a GREEN solution. Go for it. Bush Driver - South Africa

Cool idea. Hey . . . . I made a HVAC funny !

I . .. . I . . . I crack myself up.

Where I live and water is BLOODY expensive I'll need to compare my water costs to electricity saved but suppose it is a payoff.

Ok everyone here is the deal as per the water chemestry company that takes care of my boiler.

The chemist I spoke with had this to say:

1. The evaporation of the water is wat causes the mineral deposits on the coils as several have stated.

2. The only way to keep the deposits from being in the water is through RO (reverse osmosis).

3. The deposits will be significantly reduced if the coils ar able to stay wet That is to say you can supply them with enough water keep them from going dry.

4. There is no chemical means for treating the water to remove the disolved particles from the water.

5 Filtration will not remove anything but the largest particulate matter disolved particles will still be present.

6. If i am only using them during the very hot part of the summer and keeping them wet then the buildup will be minimal.

So in conclusion by keeping the coils wet and having them cleaned when all is done we should be in good shape.

Thanks for all the information guys and all the help.

A couple of thoughts on this. First, if you live in the desert get a swamp cooler. I live in the southeast US and could easily catch and store rainwater for the misters, (why not let god do the distilling and just filter out particulates). Finally, why not use the misters far enough away from the coils that it cools the air around them without actually wetting them, maybe not quite as effective, but it would eliminate hassles.