Radiator Mist Cooling System

[Busted Knuckle]

Hey I'm here and Marc is not from San Diego (I hope)
I'm just lurking and agreeing with almost every post on this board...
quite not the same for BNO though... I give up over there!!

Amen! I couldn't have said it better!

[Burgermeister]

Case in point - Geoff Smith.

He experienced an overheat condition while pulling a heavy trailer up a grade and misters cooled the engine down.

This is my first comment on Geoff and it's a positive one.

He is knowledgable and experienced.  He's reasonably certain that his cooling system and engine is in good order.  He knows what to look for and what to do if it's found.  He knows to watch the exhaust for over-fueling and he's a smart driver that will keep the engine RPMs up to ensure the maximum flow of coolant (MASS!!!!)  

The use of misters by such a converter is appropriate.

Now ask him if he'll repeat the situation  after blocking off 1/4 his radiator?  ( I don't think so!)

There's a possibility that one cylinder of his 6V92 engine may have compromised coolant flow.  Let's say it does for the sake of discussion.

As he starts to climb that grade again, that one cylinder will  get hot quicker than the other 5.   For awhile, the extra hot coolant coming off the one cylinder will be absorbed in the coolant of the other 5, raising the temp, but without the temp showing an overheat.  

The one cylinder can be near critical by the time Geoff sees the need to turn on the mister. This will drop the overall temp of the coolant, but by this time the coolant/metal interface isn't micro bubbles anymore, it can develop into macro bubbles and even the mister'cooled coolant can't get to the metal interface sufficient to cool it down.

I daresay that even Geoff could get "fooled" by this one, but he's one of the unlikely ones.

What would some of the converters who've so nicely detailed their "first trip" bringing a bus home, (the learning curve and numerous uncertainties) do if confronted with such a situation?   More likely than not, they'd do some serious detriment to their busses.

My comments have been directed soley to those individuals.


On Another Point - flood vs. spray.

Those parameters in the absence of distinguishing the dynamics of the heat exchange mechanism between "flood" or "spray" (evaporation) or anything else conceals the situation.

If a pure "flood" you'd have water to water conduction of heat.  What you would prefer to do is supply just enough water in such a way that it evaporates off the radiator core.  Evaporating water absorbs (takes away) much, much, much more heat than unevaporated water flow.

The goal would be to put enough water on the core but  just short of shifting from evaporation down to conduction.  The water evaporating after it is blown off the coolant tubes would waste the "opportunity" presented by the MASS of the water the misters are delivering.  

Geoff's flood approach is much more reasonable in AZ, (and might not fully be a flood if you could get a microscope on his coolant tube)  because of the high temps and low humidity.  In the MidWest and East in the summertime the 98% humidity pushing the "evaporation" method closer to "flood."  Anybody remember the term "Partial Pressure of Water" from their high school or college inorganic chemistry?  

[Melbo]

Evaporation is the best -- Remember from high school physics --

Every gram of water that is vaporized removes one Calorie of heat

If you are flooding the radiator the water has to "absorb" the heat.

As the water evaporates it "dissipates" the heat a subtle but very important difference

NOW -- on another thread I wondered which will cause an error at the temp guage

The sending unit or the temp guage itself??

Sorry to hijack the thread but what are the thoughts on that


Melbo

[Geoff]

I'm reading a lot of theory here and very little practical experience under real condtions.  I give actual experience and get back theory.  The people I know that have working radiator water sprayers use a lot of water, they may call them misters, but they are actually sprayers.  I strated with a small system using a windsheild washer pump and it did nothing, somebody on one of the boards said they had to hook their system up to the house water supply with a regular RV pump so I followed their advice and it works.  If one of you theorists want to set up their "misting" system and can honestly say it is possible to mist the air going into the radiator that is strong enough to pull your shirt off and it cools the engine I'm all ears.  I've heard enough theory.

--Geoff

[DrivingMissLazy]

I'm reading a lot of theory here and very little practical experience under real condtions.  I give actual experience and get back theory.  The people I know that have working radiator water sprayers use a lot of water, they may call them misters, but they are actually sprayers.  I strated with a small system using a windsheild washer pump and it did nothing, somebody on one of the boards said they had to hook their system up to the house water supply with a regular RV pump so I followed their advice and it works.  If one of you theorists want to set up their "misting" system and can honestly say it is possible to mist the air going into the radiator that is strong enough to pull your shirt off and it cools the engine I'm all ears.  I've heard enough theory.

--Geoff

Geoff, read all my posts. I have been there done that (BTDT) for 15 years and was 100% successful with a mist that never really got the radiator wet. At least as far as I could tell. Even sitting still with the engine at 1800 rpm, the radiator never appeared soaked.
Richard

[Sojourner]

Geoff
Your system is called "liquid-heat-exchanger" principle...liquid exchange heat or cool liquid system. However watering down radiator will reduce air-flow due to blockage or flooding air passage.

Mist-er is fine spray to cooled air before entering radiator air-fins. In so doing it shrink heated ambient air to carry more BTU with it.

After-all...ambient air is free & very light weight as compare to watering system such as old "one-lung-er" engine...no radiator but a large cast-iron tank to hold water. Even than it need running water flowing in from river whenever working steady hard load.

It hard to beat the prices of God's given air to cool our engine.

Which is most practical....carry a lot of water on hand or use less water to get the same job done?

I did mine like Richard setup (no-valve) but only one garden spray nozzle attach behind its grille of each of MCI-8 radiator's inlet.....it work to reduce about 5° F cooler in 195° F range. However Richard is better due to extra spray nozzles. MCI would be 3 spray nozzles per side to achieve greater cooling reserve.

FWIW

Sojourn for Christ, Jerry

[Geoff]

Okay, I did a Google search to see what the GPM difference was between misters and sprayers and from what I gather you can get quite a bit of water through a mister.  What I am having difficulty with is believing that you are actually going to maintain a mist directly in front of a air sucking radiator at operating speeds without the mist turning into water drops. I am happy with my spray system, but I am going to turn the sprayer adjustments down as I know I am showering more than enough water at my radiator.  I wish I could look at someone who has a true mister system-- I have absolutely the highest regard for Richard and what he has to say so if he says a mister system worked for him, I believe it.  I just want to see one in action, you may change my mind yet.

--Geoff

[DrivingMissLazy]

Okay, I did a Google search to see what the GPM difference was between misters and sprayers and from what I gather you can get quite a bit of water through a mister.  What I am having difficulty with is believing that you are actually going to maintain a mist directly in front of a air sucking radiator at operating speeds without the mist turning into water drops. I am happy with my spray system, but I am going to turn the sprayer adjustments down as I know I am showering more than enough water at my radiator.  I wish I could look at someone who has a true mister system-- I have absolutely the highest regard for Richard and what he has to say so if he says a mister system worked for him, I believe it.  I just want to see one in action, you may change my mind yet.

--Geoff

There is a company in Las Vegas that installs mister systems on busses. I do not remember the name and I have never met them but I do recall a couple of people posting on the BNO board about them, and they were very happy. Maybe someone remembers?

I do not know why you think the mist would change into drops of water. Believe me, it justs disappears before it hits the radiator and that is a very short distance. The radiator does not appear wet. If you have seen the misters at the produce department of a large grocery store, that is the type of mister you need.

Richard

[rv_safetyman]

OK guys, need your opinion on mister parts.

Background:  my air to air radiator is very marginal on long pulls.  I tried to rig up a mister for the big passes on the way home and the "irrigation" sprayer parts at Home Depot just seemed very cheesy.  Indeed, the plastic delivery tube melted from the hot air going through the air to air radiator.  In addition, Richard mentions the issue with the tubing coming off the heads (I had that problem as well). 

So, I am looking for something more practical.  Take a look at:

http://www.plumbingsupply.com/misterscooldown.html

and see what you guys think.  It sure looks like a great way to mount the misters.  The stiff PVC tubing would assure that the misters are pointed in the right direction and the tubing would be easy to mount to the radiator with tie wraps (mister pointing away from the radiator).

If you guys think this is a good approach, what size head would you use.  I think I will mount 4 units for a heat exchanger that is 20 X 30 inches.  Right now I am leaning towards the .5 GPM units.

I will be using my extra water pump and have wired a push button on the dash to operate the pump as needed (long hills).

[Buffalo SpaceShip]

Jim, I do like the idea of using rigid PVC pipe on the radiator(s). I think it's much, much better than the drip system pipe. My only concern would be the plastic head of the misters on your link. I'd worry that they might not handle the heat very well too close to the rad. and engine heat. I read their FAQ about why they don't sell brass misters anymore, but I wonder if a threaded brass mister would handle the heat better.

Maybe it'd do fine, I dunno. Anyone else with an opinion?

Thanks for the link and PVC idea,
Brian Brown
4108-216

[Buffalo SpaceShip]

Geoff, I think you'll have to consider your climate to determine how much mist/water to throw into the rad. Whether its water droplets or mist, you want to get only enough into the air to raise the humidity but keep it from actually splashing a lot of liquid water onto the rad. Not only are you wasting prodigous quantities of water, but the science that everyone keeps mentioning is working against you. But... with the super-hot, super dry air in AZ, you'll still need quite a bit of water compared to someplace milder and more humid. There's probably some formula to help convert temp./desired humidity/required air flow into GPH... but just gettin' it close(r) would be good.

Bear in mind, I believe that your solution works, I just suspect it'd do even better w/o throwing all of that liquid right onto the rad. I also get what you're saying about the massive turbulence possibly keeping the mist from ever forming in the first place. Maybe some trial and error is in order... during a time when you're not pressed to get somewhere and can pull over and cool down as needed.

Something else that just crossed my mind... I've battled is cooling of my V730 in my 4108. When pulling those grades unlocked in 1st or 2nd, there's a massive amount of heat generated by the tranny, especially towing something. If you have a tranny cooler that uses engine coolant to cool it, it could well be dumping heat from the tranny into the engine cooling system.

My bus was converted from a coolant-cooler to an air cooler before I purchased it, and the P.O. said that the engine temps were easier to maintain afterwards. I recently had the cooler fan fuse blow and it seriously affected its cooling (obviously). When fixing it, I also added some holes in the side of my bus to provide freer, cooler air the tranny cooler, and it helped immensely. Since yours came stock with the V730, I doubt if its as much of an issue... but since the the coach was originally a transit, it probably wasn't engineered to pull long highway grades in AZ hauling up big trailers either.

I'm not necessarily saying your cooling issues are definately your tranny, but it could be contributing to the heat. I sure know mine likes to heat up on the climbs.

Anyways, just some random thoughts. Please keep us posted,
Brian Brown
Longmont, CO
4108-216

[Buffalo SpaceShip]

Gads, I'm posting like a madman on this topic...

Jim, I did find some other nozzles that look interesting. http://www.mistcooling.com/nozlles.htm They're brass 1/8" MIP fittings, and the one with the 160 degree spray angle looks especially promising for a rad. spray application.

Just some more ideas,
Brian Brown
Longmont, CO

[JackConrad]

What ever mist nozzle you use, make sure the water is filtered before going to the nozzle. It does not take much to plug one (or several) of these.  Jack

Do not ask how I know this

[DrivingMissLazy]

Well, I swore to myself that I was not going to post anything else, but I really have trouble keeping my mouth shut.

When I designed my system, the Internet was not available, so I had little choice other than the local hardware store.
The misters were extremely cheap and I started off with the smallest water flow rating they had. I never had to go bigger, but I do not recall what that gph rating was.

In construction, I installed a T in the 1/4 line, then about 1 inch of line and then the mister nozzle which was a 90 degree design. That construction allowed me to turn the mister any way I wanted to try and get the best performance. I ended up with the misters turned outward and forward to try and get the mist blowing away from the coach. Once the engine got up to speed it sucked the mist back and did a good job of dispersing the mist over a larger area.  If you use the drip mist tubing, make sure you tie wrap all the joints to keep them from coming apart due to heat expansion of the tubing.
Richard

[rv_safetyman]

I am making a post to this thread so that it comes up on top again.  DrDave posted a source of mister nozzxles and I thought folks should also see this excellent thread.