Mister system

windtrader · July 02, 2018, 10:02:06 PM

QuoteThe actual coverage of water on the rad is problematic due to the wind patterns entering the rad cavity. At speed, some misters are not wetting anything except a thin strip behind them.

BW said this earlier. I'm thinking that maximum cooling occurs through heat transfer via the water and wetted fins. Like, sweat on the body provides more cooling that just air cooling the body. Evaporation occurs from the air being forced along by the fans and onto the fins of the radiator cores. Temperatures are lower than if only air flow with no liquid for added evaporation.

Clifford - I could not find any technical documentation with that Hayden unit, not even a simple line chart showing cooling without and with the mister. More like a shopping channel item - catchy but hardly well designed or of true quality.

And good point that efficiency of misters diminishes as the ambient humidity increases. Makes one ponder how well misters would work on a long 6% grade where it would be hot and humid. Seems high humidity and low elevations go hand in hand so unlikely to need to worry about this issue in mostly flat lands.

JC - makes sense less engineering is required if drivers are expected to manually in real time know just what is happening and making adjustments to keep the equipment running "in spec" and as operating as designed and intended to be used (with experienced drivers)

John - That agrees with what others say.

Excessive water simply is unnecessary. The maximum needed is to coat the radiator fins and keep them wetted.

luvrbus · July 03, 2018, 07:02:49 AM

Sorry guys but I never owned a bus that ran hot so there was never a need for so called misters for me,I could heat my MCI 8 with a 8v92TA if I kept my foot it on a long pull,the Eagle with a 8v92TA was never a problem.There is a old saying when you push the throttle and don't gain speed it's lugging find another gear

chessie4905 · July 03, 2018, 07:24:14 AM

How about a humidity sensing switch that injects washer solvent solution when humidity is really high........

lvmci · July 03, 2018, 09:25:54 AM

What hasn't caught on here, is that there are 2 kinds of water sprayers. The misting system, which cools the air just like in your back yard or restaurant, which does not work above 25% humidity and the sprayer system, taking misters and drilling out the hole to allow streams of water. This last system doesn't transfer the heat from the radiator fins and cores to the air, rather transfers heat from fin & core to the water. On my radiator spray system the 3 sprayer per side, alternate and divides the radiator into 7 sections, air cooling, water cooling every other section. The water carrying the heat, exiting the engine side, becomes a heavy mist, sprinkling over the engine parts as it is pushed past the engine causing a second layer of misting cooling, possibly helping to accelerate the speed of the air flowing towards the road, creating a greater vacuum effect with the weight of the air, because of the droplets of water, based on speed of the bus, lvmci...

luvrbus · July 03, 2018, 09:56:58 AM

Ok why are folks calling this a misting system Tom the way you describe it is like a flood system like the difference between a drip system and sprinkler system ,thanks for the 26% number I couldn't remember that number for the life of me

Lin · July 03, 2018, 10:50:43 AM

Clifford-- I think that that is what I was saying about my system; it is not really misting, it is spraying. That is why I don't even use nozzles-- just holes in a PVC pipe. The spray is not aimed at the radiators but rather parallel to the front of the radiator with the assumption that the airflow will just pull the water in. The system works well but may use more water than a better engineered one. Since it is off my main tank, I am not worried about how much water it is using. It only needs to be on for 5-10 minutes at a time anyway.

When I started with this bus I did have a heat problem. I tried several things to deal with it:

1. Made a jig to partially hold the engine doors open to allow more air to pass through
2. Put a mud flap forward of the engine to create a negative pressure to also increase airflow
3. Put air scoops on the intakes
4. Add the spray system as the ultimate back up

All helped to some degree. I also changed my driving habits to keep the rpm's between 1600 and 1800 at all times while climbing, which may be the most important alteration. It should go without saying that a properly sized cooling system should just work without needing to be sprayed, but adding a spray system is certainly an efficient alternative to redesigning/rebuilding the dubious cooling that some of these came with.

windtrader · July 03, 2018, 12:07:27 PM

Quote It should go without saying that a properly sized cooling system should just work without needing to be sprayed

Like Lin and Clifford are thinking. For stock motor/coach configurations, maybe all these extra cooling mods are just restoring lost efficiency from poor sealing or other defects in the original system.

lvmci · July 03, 2018, 12:35:55 PM

Yes Clifford, I agree, they both spray out water, one a stream, one a mist. I've been looking for a nozzle that creates a flat spray, thinking it would spray a wider, flatter area, increasing the radiators tubes directly hit with the spray and would use less water for shorter amount of time, tom...

Iceni John · July 03, 2018, 01:08:25 PM

Quote from: windtrader on July 03, 2018, 12:07:27 PM
Like Lin and Clifford are thinking. For stock motor/coach configurations, maybe all these extra cooling mods are just restoring lost efficiency from poor sealing or other defects in the original system.

The reason for me to make a mister system was very simple - my bus's radiator is slightly undersized compared with an Eagle's that was parked near me. Eagles are well known for having fewer cooling issues than other makes, and one look at the size of their radiators tells you why. I managed to make my new radiator a few inches taller than before, but I could not make it any wider, lower or thicker due to its mounting frame and space. All we can do is work with what we have, and use imaginative solutions to the inevitable problems that bus ownership entails. Heck, I'd even consider radiator scoops if they worked . . .

John

Lin · July 03, 2018, 02:23:23 PM

There are mixed reports on scoops. Some have tried ready made ones that are kind of narrow and did not find them helpful. I had some made according to the design recommended by Fred Hobie, who said he got good results in his own tests. I don't know if his blog is still available or not. Do mine work? I think they help a little, but who knows.

buswarrior · July 03, 2018, 03:30:47 PM

I do not recall reading about scoops from Fred Hobe, but I listened closely when he told a few of us the story one evening at Arcadia back a bunch of years ago.

Scoop needs to stand off 3" and come forward half way or better on the screens.

His test set actually ran more air than the fans could swallow. Propped open the fan door to BYPASS the fans... crazy like a fox... took off up the highway, watched temp climb and then watched it drop right back down.

Try that with your personal military spec engine, brave internet warriors...

Forget those little Mickey Mouse ears, they actually roll the air OUT of the radiator cavity.

An engineer who does airliner engine intakes was working on this with Mr Hobe. They had some fun, calculations on napkins, proved their theories and that was it.

Why? Because busnuts will not buy stuff. No return on the investment needed to finish the job properly, as soon as one set got out there, the copying would begin.

At times, we are our own worst enemies...

The pioneers had no Internet to wipe their noses and a$$e$.

Happy coaching!
Buswarrior

Iceni John · July 03, 2018, 04:01:22 PM

One thing I noticed when I was last in Mexico traveling by bus, the new long-distance buses there mostly have some sort of scoops or louvers to encourage air into their radiators. They're usually simple vertical angled panels a few inches wide pointing forward at about 45 degrees or so, with a few per radiator opening. Certainly nothing high-tech, but presumably they work. They looked like they were original from the factory, not some after-market doodad cobbled together. Next time I'm there I'll pay closer attention to them and see if I can replicate something myself, just like BW says "as soon as one set got out there, the copying would begin"! If they help even a tiny bit without any downsides, then why not? I just don't want it to look too hoky or amateurish.

John

lostagain · July 03, 2018, 04:39:45 PM

The new Prevost H3-45, and maybe the older ones too, have 45 degree angled louvers on the radiator door. Looks like it would direct the air flow into the rad when the bus is at speed...

I know for sure the rad scoops you see on some old buses don't work... You'll get as good or better cooling without them. They are ugly, and they really make your bus look like it has a cooling problem...

JC

windtrader · July 03, 2018, 07:12:24 PM

Seriously? The air scoops don't help? Is that folklore or factually proven?

luvrbus · July 03, 2018, 08:48:01 PM

Quote from: windtrader on July 03, 2018, 07:12:24 PM
Seriously? The air scoops don't help? Is that folklore or factually proven?

You get a scoop out 7 or 8 inches they work,you can check it yourself with a poor mans wind tunnel that is a ball of yarn at 30 mph you can see the wind pattern by watching the yarn,the R&M scoops are for decoration they are useless for helping with cooling,Richard never sold his scoops except for dress