Water misters to improve condenser performance?
Water misters to improve condenser performance?
(OP)
I am considering making my own distilled water misting system ahead of my condenser/compress unit to get more cooling power out of it. I am planning on triggering it by using a two-stage thermostat inside the living space. The condenser/compressor unit is a high quality, 12 SEER, scroll-type Carrier unit. It is only 2.5 tons for 3300/sq-ft which is why I am trying to get more output on hot days. Has anyone had experience with this?
Thanks!
Thanks!





RE: Water misters to improve condenser performance?
RE: Water misters to improve condenser performance?
RE: Water misters to improve condenser performance?
RE: Water misters to improve condenser performance?
RE: Water misters to improve condenser performance?
RE: Water misters to improve condenser performance?
"Check your head pressure on the coolest day you would use the unit."
Let's say that it would be 85 degF and dry. So I'll check the head (outlet) pressure. Then:
"Then wait for a day that is just hot enough for you to want to use the water (90*?) and extremely dry. Play with your water flowrate (Needle valve) and see how it affects the head pressure. If it does not drop below your cool day pressure, you should be OK."
So you are saying that adding water mist will drop the head pressure? I think I understand that too much cooling on the condenser will actually turn the return gas to liquid and damage the pump. My trick is, therefore, to cool the gas right to this point but not beyond. So, to continue, I set the amount of misting so that on this day, the pressure doesn't drop below the previous test day (85 deg F). Then, any day hotter than that, I am safe.
I am now beginning to understand the trick (I think). So here is what I propose. I will use the two stage thermostat and put the water activation signal (the higher temp thermostat setpoint) in series with (contingent upon) a compressor head pressure switch such that as long as the head pressure stays above a certain point, the misting system can activate. Once the pressure drops below the allowable point the pressure switch cuts out the misting until the pressure goes up past the internal pressure switch setback.
What did I say?
RE: Water misters to improve condenser performance?
Let me preface by saying I like the way you think. You've obviously graduated to the point where anything is within your realm from a controls standpoint. My friend at one time had a cat litter box with a motion detector that ran an exhaust fan.
Cooling in the evaporator is by flashing the refrigerant from a liquid state to a gas state. If your condenser does not currently return the refrigerant to the liquid state (which you have not yet mentioned as being a problem with this unit - e.g., no mention of head pressure trips, etc., and I like your unit size with respect to the square footage) I would trust the unit to do what it's designed to do without meddling. Demineralizing water as you mention will probably provide improvement in the corrosion rate over city water, but even pure deionized water will form some carbonic acid (H2CO2), especially when introduced as a mist onto condenser surfaces (by the way, will the condenser fan also be wetted?). The net effect in time will be degradation of your condenser and associated moving parts in a manner that I think would outweigh any benefits that you mention.
I like the discussion above and all posts are insightful and interesting, but I would recommend you instead catch an Angels game (World Series Champs) or even a Ducks game, who I'm adamantly rooting for to win over the Devils. Clean the evaporator coils, change the filters, and maybe even add a small window AC for design day purposes. -CB
RE: Water misters to improve condenser performance?
RE: Water misters to improve condenser performance?
RE: Water misters to improve condenser performance?
RE: Water misters to improve condenser performance?
In the technical papers I have written about this process, the improvement in performance is quite impressive. Based on typical UK conditions, a standard Carrier chiller delivered a COP of about 3, when the adiabatic spray system is activated it increases to over 5.
To avoid over condensing of the liquid refrigerant, it may be neccessary to 'pulse' the water flow on & off. Particularly on such a small system.
Regards,
Cooky
RE: Water misters to improve condenser performance?
From a previous post of mine:
"I will use the two stage thermostat and put the water activation signal (the higher temp thermostat setpoint) in series with (contingent upon) a compressor head pressure switch such that as long as the head pressure stays above a certain point, the misting system can activate. Once the pressure drops below the allowable point the pressure switch cuts out the misting until the pressure goes up past the internal pressure switch setback."
RE: Water misters to improve condenser performance?
You must have a dedicated HP cut-out switch, so if all else fails the compressor will be switched off.
On the subject of controlling the system head pressure, it may be helpful to realize that when the water spray is activated, the heat rejection from the condenser increases almost immediately by 35% to 40%. Which will cause a rapid reduction in the head pressure (hence the suggestion to pulse the water).
You may need to have more than 2 stages of control if you hope to achieve good control of the head pressure. Maybe you need to experiment to find the best solution, as you are using such a small system.
Regards,
Cooky.