Twin/Double Coolant Radiators

[skippydiesel]

I am intrigued by the twin/double, in series coolant radiators , as fitted to some (all?) Rotax powered Europa's and other aircraft.

 

Anyone had an experience with such an installation? What might be the pros/cons (aside from slight weight penalty and more complex plumbing/failure points)?

 

AND

 

Does anyone know of a reputable supplier(s) of the above ?

Edited March 29, 2023 by skippydiesel

[facthunter]

Can't see the point of having them in series or for having two for that matter although it was done on the SV Ford V8's. Temperature difference is directly related to heat transfer. The hotter you can run your radiator the smaller it can be,  Nev

[IBob]

Do you have a pic as to how/where they are mounting them, Skippy?

[onetrack]

Twice the level of potential problems, to my way of thinking.

[skippydiesel]

1 hour ago, facthunter said:

Can't see the point of having them in series or for having two for that matter although it was done on the SV Ford V8's. Temperature difference is directly related to heat transfer. The hotter you can run your radiator the smaller it can be,  Nev

Simple! The points are: 

 

• Space Salutation
• Small Frontal Area

 

 

ATTACHMENTS

[skippydiesel]

35 minutes ago, onetrack said:

Twice the level of potential problems, to my way of thinking.

Absolutely!

 

In the pursuit of efficiency, sometimes compromise is called for.

[skippydiesel]

48 minutes ago, IBob said:

Do you have a pic as to how/where they are mounting them, Skippy?

See above IBob.

 

I have also seen similar setups in Europa aircraft. The Europa radiators where very much thicker ( depth of fin) than the two Sonex shown.

[IBob]

30 minutes ago, skippydiesel said:

See above IBob.

 

I have also seen similar setups in Europa aircraft. The Europa radiators where very much thicker ( depth of fin) than the two Sonex shown.

Looks okay to me, apart from the possible drawbacks already mentioned.
About the only comment I would add is that they must be in series, not in parallel: I had a site with twin industrial boilers in parallel, in a closed circuit feeding a plate heat exchange. While the pipe work was almost exactly mirrored between the two boilers and each boiler had it's own circulating pump, if there was any restriction in the system then the flow would go through one boiler or the other. And once the flow began to favour one boiler, it tipped increasingly that way. So the stable states were flow through one boiler or the other, and the unstable state was equal flow through both.

Edited March 29, 2023 by IBob

[skippydiesel]

SUPPLIIERS?????

[facthunter]

Why are you sure they are in series? It pretty much precludes any airflow adjustment in flight and is exposed to FO damage and why is more efficient than other designs? Nev

[facthunter]

What does space salutation mean? Are you greeting aliens?  And the frontal  area is not particularly small. Nev

[turboplanner]

2 hours ago, skippydiesel said:

Absolutely!

 

In the pursuit of efficiency, sometimes compromise is called for.

Other than failing to correctly judge the right time to change the hoses, what makes you say this?

[skippydiesel]

27 minutes ago, facthunter said:

Why are you sure they are in series? It pretty much precludes any airflow adjustment in flight and is exposed to FO damage and why is more efficient than other designs? Nev

Pretty sure - In this context I use series to indicate the coolant will flow from engine into one radiator top/out the bottom - top /then exit bottom, back to engine. Series also minimises the number of connections/hoses. Parallel would require each radiator to have three openings,  so that the top/top & bottom/bottom of each radiator would be connected  - cant see this being efficient, as hot coolant may bypass the internal tubes.

 

What airflow adjustments (other than cowl flap) do you think might be precluded?

 

FO damage?- I would suggest that this radiator solution, offers less change of FO damage compared with so may other (Rotax) radiator front of cowl  installations - do you know of any radiators being damage in this class of aircraft?

 

I will be happy with equal efficiency (to Rotax supplied rad) - problem is that where current rad located (exit air vent) it appears to be restricting the exit ait/pressurising the cowling , which in tern is impacting negatively on other (oil/barrels) cooling systems. I am exploring solutions - the two small radiator concept will be looked at along side more conventional lay outs.

 

I would much preferer to go with a known, effective heat exchanger location/cowl air management solution, problem is Rotax 9 engines are relatively new to Sonex and most builds seem to have their fair share of heating issues (including a recent Sonex factory build, that used two radiators back near the firewall).

22 minutes ago, facthunter said:

What does space salutation mean? Are you greeting aliens?  And the frontal  area is not particularly small. Nev

Yeah! Salutation to you - it should have read Space solution.

 

As for frontal area - it all relative - sure beats having a single radiator slung out the front. I would expect it would ensure a good supply of "ram" air to the radiators even on the ground. Climb angle would have little impact on air flow. Having said that there are options to "burry" the single radiator further back under the engine & duct air from a "smiley face" vent or similar.

 

 

[Blueadventures]

Poor positioning and cowl design.  The two are blocking air flow to the cylinder fins.  Better to situate single larger radiator below gearbox output housing / shaft so ambiant temp air flow contacts cylinder fins, thereby adding to the temp removal systems efficiency.  Bit more profile drag but best / better overall in my opinion.

[skippydiesel]

41 minutes ago, turboplanner said:

Other than failing to correctly judge the right time to change the hoses, what makes you say this?

Don't know where you are coming from here Turb - changing hoses?? I have always adhered to the Rotax 5 year "rubber" replacement recommendation.

 

"the pursuit of efficiency," is the hope for reduced drag, by having minimal cowl frontal area & openings, allowing for high cruise speed/fuel efficiency..

 

[skippydiesel]

3 minutes ago, Blueadventures said:

Poor positioning and cowl design.  The two are blocking air flow to the cylinder fins.  Better to situate single larger radiator below gearbox output housing / shaft so ambiant temp air flow contacts cylinder fins, thereby adding to the temp removal systems efficiency.  Bit more profile drag but best / better overall in my opinion.

Fair comment Blue - I haven't discounted this approach - just exploring options. 

 

I note that the two Sonex/Rotax, with frontal twin radiators, examples, also have small cowling inlets directly below the radiator "nostrils" presumably to address your point.

 

[facthunter]

Props get plenty of stone damage so I would think radiators would be vulnerable They are very fragile really. You have a lot of choices where you can locate radiators. Adjusting the cooling effect for changed conditions has been the most constant and only problem I've experienced with 9 series installations other than roughness at part load. I am a fan of cowl flaps for quicker  warm up and keeping the motor hotter when descending AND saving drag.. Nev.

[skippydiesel]

SUPPLIIERS?????

[turboplanner]

6 hours ago, skippydiesel said:

Don't know where you are coming from here Turb - changing hoses?? I have always adhered to the Rotax 5 year "rubber" replacement recommendation.

I would suggest you check cooling hoses every few hours; they certainly don't all last for five years, for a variety of reasons

 

1. Quality of the hoses bought

2. Type of clamps used

     (a) where the manufacturer uses spring type clamps, they are designed for a standard clamping pressure which will not reduce wall thickness.

     (b) where someone buys a handfull of worm drives usually a couple will crack and the hose will fail.

     (c) where worm drives are used they need to be torqued to a standard; where someone torques one until his blood vessels nearly burst (most  people) you'll see the hose squeezed down to a fraction of its original wall thickness and there will be pin prick leaking from this point early in the normal hose life.

 

6 hours ago, skippydiesel said:

 

"the pursuit of efficiency," is the hope for reduced drag, by having minimal cowl frontal area & openings, allowing for high cruise speed/fuel efficiency..

When you get into engineering a radiator there are varying tube sizes and fin sizes producing varrying results.

Formula 1 cars use spit cores; I've used a single offset core for a head-only cooling application, and I've built tunnels for off-engine prop shafts. You don't have to be tied down by convention.

6 hours ago, skippydiesel said:

 

 

Edited March 29, 2023 by turboplanner

[Thruster88]

Rotax 582 with engine mounted radiators as used on Thrusters and trikes etc have twin radiators. Flow is in series. Twins are used by Rotax in this situation because it makes a better package, reliable mounting etc.

 

There are two sizes of radiators used on 582, standard and tropical. The small sizes cools 65hp on very hot days at low airspeed, 35-40knots. The tropical may have enough area for a 100hp 912, they are supplied by Rotax.

 

We recently had a Sling tsi at the shop. The way the coolers were mounted was pretty neat. They just clip to the cowling, no air leaks, reduced vibration on the radiator. 

 

To get maximum efficiency you will need cowl flaps. It is a simple way to reduce cooling drag when you don't need maximum cooling.  

[Thruster88]

Correction, flow is parallel in the Rotax twin radiators.  

[RFguy]

I've never seen any stone damage in the very low mounted Jabiru oil cooler.

Do propellors (on GA)  'suck' stones in from in front of them , or do they stir up the stones beneath them ?
 

As I commented elsewhere, its all about whether you can acheive an air pressure differential across the radiator, which is VERY cheaply assessed with a clear bit of tube and some water.

if its frontal facing, you can estimate the frontal pressure using the formula for inches of water = ((airspeed knots  * airspeed knots )  * 25 ) / 40000
Then have a tube from behind the radiator to static  .  performance will be compromised by how much air is getting into the cowl  (if the radiator exit is in the cowling) 
If the radiator is ducted, like many GA,  have the tube across both sides of the radiator. 

 

 

Edited March 29, 2023 by RFguy

[facthunter]

Aluminium Radiators are of much lighter construction than oil coolers are. You can't even safely wash them with a water jet.  Nev

[skippydiesel]

23 hours ago, RFguy said:

I've never seen any stone damage in the very low mounted Jabiru oil cooler.

Do propellors (on GA)  'suck' stones in from in front of them , or do they stir up the stones beneath them ?
 

As I commented elsewhere, its all about whether you can acheive an air pressure differential across the radiator, which is VERY cheaply assessed with a clear bit of tube and some water.

if its frontal facing, you can estimate the frontal pressure using the formula for inches of water = ((airspeed knots  * airspeed knots )  * 25 ) / 40000
Then have a tube from behind the radiator to static  .  performance will be compromised by how much air is getting into the cowl  (if the radiator exit is in the cowling) 
If the radiator is ducted, like many GA,  have the tube across both sides of the radiator. 

 

 

Thanks RF - you always come up with the reasoned approach.

[skippydiesel]

FYI