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Re Coolant Coice

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irampil(at)notes.cc.sunys
Guest

Posted: Fri May 04, 2007 7:32 am Post subject: Re Coolant Coice

Pretty pictures Ron but the fires do not illuminate the situation

 regarding coolant.  The fact that it easily burns is no surprise.

 Rotax made an engineering mistake with Evans and is backing off.

 PFA is making the situation more confusing with a totally mindless

 directive.

 

 For safety, experimental a/c builders need to understand the facts,

 rationales, and theorys, and to know which is which.

 

 

 Unlike the the antique powerplants in certificated a/c, Rotax engines

 have a significantly different metallurgy - they are made of aluminum

 alloy. Fact.  This alloy anneals just below 300F.  That is to say it

 softens and the cylinder heads will begin to warp with temperatures

 exceeding 275F for a length of time. Fact, see Line maint manual for

 temp-time tolerance curve. This temperature limit is more than 100F

 below routine lycosaurus CHT. Exceeding the time-temp limits buys you

 a tear down and Rockwell hardness testing of heads.

 

 Liquid coolant is required to keep Rotax CHTs in the required range.

 The coolant must provide an efficient path to dump combustion and compression heat to preserve the temper of the aluminum. Evans is far less

 efficient at heat transfer then water-based coolant.Fact. The "value" of

 Evans is its higher vapor pressure. Why?  As fluids approach their boiling

 point they start to nucleate small bubbles (look at a pot of near-boiling water).  These bubbles insulate the walls of the coolant path from

 efficient heat transfer from the metal to the liquid.

 Evans will not form as many of these bubbles at operating temperature

 as standard coolant. It will nontheless let heads rise closer to the

 annealing temp because it can't carry away the heat as fast even

 without the bubbles.

 

 A new solution to continue using water based coolant is to change the radiator

 cap to 1.2 atm from 0.9.  This will keep the vapor bubbles from forming in the

 old coolant and lead to altogether better heat sinking the cylinder heads.(Theory)

 

 There is a new SB for kit manufacturers to measure coolant temperature or to

 measure the extent of the gradient between the standard CHT measurement point

 on the outside of the head and the coolant outflow point.  The temperature of the

 coolant exiting the head, going to the radiator is always hotter and more

 closely related to the max temp inside the head than the CHT sensor. The coolant

 temp must not exceed 275F and if the gradient to the true internal temp is not

 known, then a worst case assumption leads to the new max (old style) CHT of 248F

 

 As for the flammability and the PFA, every other fluid forward of the firewall is

 flammable. One more adds no significant added risk.  Stemme had a poorly designed

 coolant/exhaust system which lead to melting of coolant lines.  This, I submit was the

 problem, not the flammability of the coolant!  It could have just as easily been

 a gas or oil line.

 

 Temperature shield hoses and keep the engine aluminum cool!

 Check out the new intrinsically heat-shielded fuel line hoses in the 900 series

 now shipping. Nice clean new design to deliver fuel to mechanical pump and thence

 to carbs with new crimp fittings, a double banjo line splitter, etc.

 

 

 Ira N224XS

 Fresh from Dean Vogel's Rotax Engine course.

   [quote][b]

mikenjulie.parkin(at)btop
Guest

Posted: Fri May 04, 2007 8:09 am Post subject: Re Coolant Coice

I have just drained the Evans stuff out of my 914 -  putting it in the engine in the first place was not my best ever decision.   What is the 'totally mindless PFA directive' ??  

 Have I missed something??

  

 regards,

  

 Mike

 [quote]   ---

Gilles.Thesee(at)ac-greno
Guest

Posted: Fri May 04, 2007 8:46 am Post subject: Re Coolant Coice

irampil(at)notes.cc.sunysb.edu a écrit :

 	  Quote: 	
		  

 As fluids approach their boiling

 point they start to nucleate small bubbles (look at a pot of 

 near-boiling water).  These bubbles insulate the walls of the coolant 

 path from

 efficient heat transfer from the metal to the liquid.




	


Ira and all,



I'm afraid it is the other way round : nucleate boiling help reject 

tremendous amounts of heat from  the engine.

Phase change from liquid to vapor absorbs several hundred times more 

heat than just raising the coolant temperature just another degree, and 

helps convection. This was clearly established by NACA researchers 

during the '40s.



See Contrails

http://contrails.free.fr/engine_liquide_refroid.php (only in French at 

the moment)

Scroll down to the NACA reports.



Also some basic info at :

http://www.tpub.com/content/doe/h1012v2/css/h1012v2_62.htm



Please note that we are speaking of nucleate boiling, and not of  the 

"boiling crisis", which is the transition from nucleate to "film 

boiling". It is film boiling which tends to isolate the hot walls from 

the coolant.



Best regards,

Gilles

http://contrails.free.fr

rparigor(at)suffolk.lib.n
Guest

Posted: Fri May 04, 2007 9:50 am Post subject: Re Coolant Coice

Hello Ira



The info provided about flammable liquids was not a full discussion on the

Pros and Cons of Evans, but was results about the flammability which I

wanted to see and feel actual results for myself before I went flying with

it in my cooling system. The results were just about what I expected. I

added a test to see if 100LL in fact does ignite as easily as Mobil 1 when

put on a hot muffler (it does not, Mobile 1 ignites a lot easier). 



There are Pros and Cons about Evans. I spent several days in contact with

folk at Evans when Rotax first came out with recommendation. I have posted

results and my conclusion in the past, but will restate:



The folk at Evans were a bit shocked that Rotax made such a quick and bold

jump with so little testing in their opinion



It is true that Evans can run with a Zero pressure coolant pressure cap,

but that is when the system design has cap located on the vacuum side of

the water pump. The Rotax 9xx has the pressure cap on the pressure side of

the water pump. You should not run a Rotax 9xx with a zero pressure cap.

On my 914 install, I will run Evans with a .9 bar cap.



The ability of Evans to transfer heat is not as good as water, or quite as

good as a 50/50 mix of water and Ethylene Glycol. Evans on most of their

applications recommend increasing flow rate of water pump or increasing

radiators ability to dump heat to compensate for this. I don't know of a

high flow Rotax water pump for use with Evans, but may be a good idea??



Evans also knows that Evans is more viscous and the radiator should not be

too restricting, or it needs to be replaced with one less restrictive, I

have the info of core requirements if anyone needs, but the Stock Europa

Radiator seemed OK when I measured it.



Evans will run a bit hotter than a 50/50 mix due to a poorer ability to

carry away heat (Perhaps 10 degrees F, what I have read anyway about

Europa Monowheels). I am willing to accept this downside. I am installing

a Rotax cooling air baffle that I think will just bout negate the slight

higher temp Evans will run over a 50/50 mix. 



On a 914 with intercooler, and a monowheel to restrict cooling flow on the

ground, boil overs on ground and in the air are not a welcome occurrence.

In addition when you are making some BTUs at altitude (an intercooled 914

can more easily do than normal aspirated), remember that the pressure cap

for the cooling system is not altitude compensating, thus at altitude you

will have less pressure in the system than at sea level, and less air to

cool things. (Side note, this lesser pressure at altitude and higher oil

temperature can cause oil tank to not condense foaming oil and a very

undesirable oil pressure drop can occur, same goes for 912 or 912S).  Even

though you could have an overall acceptable coolant temp and cylinder head

temp there can be pockets of boiling coolant that have very little ability

to carry away heat and can cause hot spots a gauge will not reveal. Evans

has a much higher boiling point, and even if you did get it to boil, it

still will carry away a significant amount of heat (Think it is 50% ??) of

what it is capable of when not boiling. 



Evans does not have to be changed, and will not hurt aluminium. Use of

Silicone coolant and radiator hoses, should negate having to replace every

5 years, not a trivial job. 



Should a leak occur where pressure was reduced, Evans would conduct at a

lower pressure better than a boiling 50/50 mix.



If you developed a coolant leak, landed and repaired and could not find

Evans, You could mix up to about half with Ethylene Glycol to get you

home, but then should flush and replace with Evans 100% (according to

Evans Tech.).



Evans about a year ago would test your coolant (for free) to make sure it

is still up to snuff (CT office).



I fully agree that keeping the heads of a 9xx cool so as not soften them

is a worthy effort. If I find that there are conditions that temporary put

motor hotter than I care for, a water spray onto radiator could help with

that, no matter Evans or 50/50. I am also going to try and optimize

cooling intake and exhaust for radiator, intake no larger than needs to

be, exhaust adjustable cowl flap (Gilles has great info on cooling

dynamics). If I see that things are not quite acceptable, an easy thing to

try a 50/50 mix (I also have a 1.2 bar cap).



Another subject, but keeping the oil hot enough, and warming it up before

you make some BTUs is a worthy effort. Especial desirable when performing

a restart after soaring. I am installing a Mocal oil thermostat with -8

fittings. It always allows a path to and from oil cooler, so if it failed

with valve opened or closed, you would never starve for oil (like some

others I looked at). What the Mocal does, is allow a easier bypass path

internal so instead of all the oil going through the cooler, for the most

part takes the easy path. there is however some oil going through the

cooler at all times. I will plumb my oil system with Aeroquip 498 and 598

(same hose, black or blue) and use mostly Aeroquip steel crimp on

fittings. Will use McMaster 90 degree stainless large radius thin wall

barbed tube fitting for bend needed. The 498 and 598 have same ID as

FC332, has a slight tighter bend radius ability without kinking (slight

larger OD, not much), and I like the crimp on steel fittings better than

the brass or aluminium push on barb fittings. The ID is very large for a

-8 hose, and is good for 300F on inside and 250F with air.



Ron Parigoris

mikenjulie.parkin(at)btop
Guest

Posted: Fri May 04, 2007 10:48 am Post subject: Re Coolant Coice

Ron,



While I would not have a problem with Evans coolant on a system designed to 

operate with it.  However, the original Europa installation was not designed 

to operate with Evans.



With G-JULZ, Rotax 914 monowheel, it is quite obvious that the cooling 

system is working close to its maximum capacity during a sustained climb on 

a summers day.



With the original configuration (oil cooler directly behind the radiator) I 

had such a problem with 50/50 during a fairly slow speed climb in the Swiss 

Alps behind Dave Buzz.  In the end, I had to leave the formation and fly 

back down the valley at an increased speed to get the temperatures back 

under control.



Once back on the ground under the advice of Andy Draper, I attacked the 

lower cowling with a hacksaw to take off a lip that I had misguidedly left 

on.  That made a slight improvement.



When I arrived back in UK, I lowered the oil cooler to the optional 

position.  From that point on, G-JULZ never had a temperature problem even 

in the most sustained climbs to altitude.



On the introduction of Evans fluid, the temperature problems in the climb 

returned.  On a summers day it was necessary to level off and accellerate at 

about 3,000ft to keep the temperatures within limits.



With both Evans and 50/50,  in the cruise the temperatures will drop to 50 

to 60 degrees C.  Which is why I am just modifying the air duct exhaust with 

a temperature controlled 'cowl' flap.



Incidentally, I had considered using an oil thermostat, but gave up on the 

idea when I read on this site that the oilstat mod did not work too well.



The bottom line is that if you chose to use Evans coolant on the standard 

Europa configuration, don't be surprised if you experience unnecessarily 

high CHT temperatures.

regards,



Mike.

josok-e(at)ukolo.fi
Guest

Posted: Fri May 04, 2007 11:19 am Post subject: Re Coolant Coice

Hi Folks,



Maybe i can help and add some more fuel for thought on this burning issue.

My coolant system has an electric heater in it, and is filled with NPG.

Reasons are that cooling is not the problem in my region, heating is.

To my surprise the coolant liquid sizzles in that heater, so it is  

micro-boiling.

That while i expected it not to form bubbles on the element.

If the stuff micro-boils at the heater, it will certainly do the same in  

the cylinder heads.

This experience imho nolliefies the argument that NPG would prevent  

micro-boiling.

The only remaining advantage for me would be that it would not pressurize  

the system, preventing blow-outs.



Regards,



Jos Okhuijsen

-- 

workshopcam http://www.okhuijsen.org/plane

http://www.europaowners.org/kit600

mau11(at)free.fr
Guest

Posted: Fri May 04, 2007 11:55 am Post subject: Re Coolant Coice

Hi all,

Just for information, since more five years we use a volkwagen coolant

liquid G012 (colour is pink).

This is perfect,there is no limit time to use, no corrosive, and

auto-obturating if you have small leak.

Many users of Rotax 4 strokes family use this liquid on ultralight

airplanes.



-----Message d'origine-----

De : owner-europa-list-server(at)matronics.com

[mailto:owner-europa-list-server(at)matronics.com]De la part de Mike Parkin

Envoyé : vendredi 4 mai 2007 20:48

À : europa-list(at)matronics.com

Objet : Re: Re Coolant Coice


<mikenjulie.parkin(at)btopenworld.com>



Ron,



While I would not have a problem with Evans coolant on a system designed to

operate with it.  However, the original Europa installation was not designed

to operate with Evans.



With G-JULZ, Rotax 914 monowheel, it is quite obvious that the cooling

system is working close to its maximum capacity during a sustained climb on

a summers day.



With the original configuration (oil cooler directly behind the radiator) I

had such a problem with 50/50 during a fairly slow speed climb in the Swiss

Alps behind Dave Buzz.  In the end, I had to leave the formation and fly

back down the valley at an increased speed to get the temperatures back

under control.



Once back on the ground under the advice of Andy Draper, I attacked the

lower cowling with a hacksaw to take off a lip that I had misguidedly left

on.  That made a slight improvement.



When I arrived back in UK, I lowered the oil cooler to the optional

position.  From that point on, G-JULZ never had a temperature problem even

in the most sustained climbs to altitude.



On the introduction of Evans fluid, the temperature problems in the climb

returned.  On a summers day it was necessary to level off and accellerate at

about 3,000ft to keep the temperatures within limits.



With both Evans and 50/50,  in the cruise the temperatures will drop to 50

to 60 degrees C.  Which is why I am just modifying the air duct exhaust with

a temperature controlled 'cowl' flap.



Incidentally, I had considered using an oil thermostat, but gave up on the

idea when I read on this site that the oilstat mod did not work too well.



The bottom line is that if you chose to use Evans coolant on the standard

Europa configuration, don't be surprised if you experience unnecessarily

high CHT temperatures.

regards,



Mike.

grahamsingleton(at)btinte
Guest

Posted: Fri May 04, 2007 3:20 pm Post subject: Re Coolant Coice

Gilles

I think you have pointed out the difference between theory and testing. 

Theory should be used to explain observed facts not the other way round.

The latent heat of vaporization of water is 525 calories per gram, 

whereas it only takes one calory to raise the temperature from 99 deg. 

to 100, boiling point. It won't boil until it gets the other 524 calories.

Thanks for your clear thinking. It made me think again

Graham

Gilles Thesee wrote:

 	  Quote: 	

 <Gilles.Thesee(at)ac-grenoble.fr>

 irampil(at)notes.cc.sunysb.edu a écrit :

>

> As fluids approach their boiling

> point they start to nucleate small bubbles (look at a pot of 

> near-boiling water).  These bubbles insulate the walls of the coolant 

> path from

> efficient heat transfer from the metal to the liquid.

>

 Ira and all,

 I'm afraid it is the other way round : nucleate boiling help reject 

 tremendous amounts of heat from  the engine.

 Phase change from liquid to vapor absorbs several hundred times more 

 heat than just raising the coolant temperature just another degree, and 

 helps convection. This was clearly established by NACA researchers 

 during the '40s.

 See Contrails

 http://contrails.free.fr/engine_liquide_refroid.php (only in French at 

 the moment)

 Scroll down to the NACA reports.

 Also some basic info at :

 http://www.tpub.com/content/doe/h1012v2/css/h1012v2_62.htm

 Please note that we are speaking of nucleate boiling, and not of  the 

 "boiling crisis", which is the transition from nucleate to "film 

 boiling". It is film boiling which tends to isolate the hot walls from 

 the coolant.

 Best regards,

 Gilles

 http://contrails.free.fr

-- 

Graham Singleton

Tel: +441629820187

Mob: +447739582005

nwcmc(at)tiscali.co.uk
Guest

Posted: Fri May 04, 2007 10:46 pm Post subject: Re Coolant Coice

 	  Quote: 	
		  Which is why I am just modifying the air duct exhaust with 

a temperature controlled 'cowl' flap. <
	




I have been down this route on 2 occasions once with a Classic cowl and

once with an XS cowl. It is normal to control the exhaust rather than

the inlet air which is what I did in both cases. Even with the outlet

for the XS cowl being fully closed it made little difference to

controlling either oil or coolant temperature. The only flap I have seen

work really successfully controls the inlet air. The design uses a flap

which can be raised to close off airflow whilst airborne or lowered on

the ground to encourage increased airflow.

Nigel Charles

karelvranken(at)hotmail.c
Guest

Posted: Sat May 05, 2007 1:11 pm Post subject: Re Coolant Coice

---

karelvranken(at)hotmail.c
Guest

Posted: Sat May 05, 2007 2:04 pm Post subject: Re Coolant Coice

Nigel, Ron, Gilles, Ira and all,

For instance I much appreciate your valuable interventions.

Using water/glycol or Evans was and still is a choice

But let's make a statement. We have the performing engine and we have the 

fixed configuration with cowlings and radiators. The engine has three 

cooling elements: air, oil and coolant. Oil and coolant temperatures are 

regulated by air flow thru the radiators. Air flow is dependent of ducts, 

speed and propeller wash. Not so simple as at a given outer temperature all 

is in the limits when cruising at more then 110 knts. The discussion about 

Evans or water/glycol may give a difference of about 10°C. But for the same 

configuration with a difference of temperature between winter and hot summer 

of 40°C and a take off speed of 60 knts at full power creates the problems. 

With 3 liters of oil and 4 liters of coolant we have no margin and no 

buffer. Until we don't find to regulate and control from the cockpit this 

temperatures we canot climb at the 1000'/min rate in every season. Let us be 

humble and say that the cowlings are of a very poor design. But we build an 

experimental airplane and we are proud of it. I think that I can find in 

Ron's approach a stimulation to continue the experiment by making several 

small changes until we succeed. And for my results you still have to wait.

Kind regards,

Karel Vranken, # 447 XS mono 912ULS Airmaster AP332 now only 35 hours.

---

grahamsingleton(at)btinte
Guest

Posted: Sat May 05, 2007 3:01 pm Post subject: Re Coolant Coice

Karel

just one further thought, you should make only one modification then 

test before you make the next mod, then you have an idea which mod works 

and which doesn't

Graham



karelvranken wrote:

 	  Quote: 	
		   

 <karelvranken(at)hotmail.com>

 

 Nigel, Ron, Gilles, Ira and all,

 I think that I 

 can find in Ron's approach a stimulation to continue the experiment by 

 making several small changes until we succeed. And for my results you 

 still have to wait.

 Kind regards,

 Karel Vranken, # 447 XS mono 912ULS Airmaster AP332 now only 35 hours.

karelvranken(at)hotmail.c
Guest

Posted: Sun May 06, 2007 2:25 pm Post subject: Re Coolant Coice

Graham,

That's the way I am thinking. Thank you for your dedication.

Karel Vranken.

---

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