I want to fit 2 radiators in parallel...

  • Thread starter Shivam2112
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Main Question or Discussion Point

What are the downside for it ,also can i fix 2 bike radiators (cross flow) by rotating them by 90 like top to down flow
 

Answers and Replies

  • #2
Baluncore
Science Advisor
2019 Award
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Welcome to PF.
Unfortunately there are too many possible interpretations of your post.
You have no question in the post, but you question your want for parallel radiators in the title.
Is this about a motor bike ?
Radiators in parallel? For coolant flow, for airflow or both?
Rotated by 90, degrees? about which axis? from what orientation to what other orientation?
How will you keep the rocks from the road away from the radiator?
Will you use two flow restrictors, or two coolant pumps, to balance the flow through the radiators?
Can you drag and drop an image onto your next post, or link to an example on the web.
 
  • #3
11
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Welcome to PF.
Unfortunately there are too many possible interpretations of your post.
You have no question in the post, but you question your want for parallel radiators in the title.
Is this about a motor bike ?
Radiators in parallel? For coolant flow, for airflow or both?
Rotated by 90, degrees? about which axis? from what orientation to what other orientation?
How will you keep the rocks from the road away from the radiator?
Will you use two flow restrictors, or two coolant pumps, to balance the flow through the radiators?
Can you drag and drop an image onto your next post, or link to an example on the web.
Thanks for pointing out, im doing a project track car, radiators will be mounted in the side pods in b section, radiators are stock ktm 390rc, car is using a ktm 390rc engine , im using parallel connection for coolant flow, im not sure about the pump if necessary maybe I'll, if it's worth it.
MVIMG_20180818_221744.jpg
Hope you can understand the orientation from the hand drawing ,this car from front view, the radiators are connected in parallel with their caps facing opposite direction(if it's best).
thanks
 

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  • #4
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Hi ! Our domestic radiators have 'flow balancing' valves to ensure pipe bends, joints, friction and room thermostats don't derange an 'even' supply of hot water.

I don't know much about vehicle radiators beyond hosing bugs out of them, but turning a front-facing radiator sideways does not seem a good idea. IMHO, the reduced natural airflow over the fins etc would seem to negate benefits of a second radiator mounted likewise...

Is there depth to mount such radiator with shrouded electric fan to provide adequate airflow ??
 
  • #5
11
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Hi ! Our domestic radiators have 'flow balancing' valves to ensure pipe bends, joints, friction and room thermostats don't derange an 'even' supply of hot water.

I don't know much about vehicle radiators beyond hosing bugs out of them, but turning a front-facing radiator sideways does not seem a good idea. IMHO, the reduced natural airflow over the fins etc would seem to negate benefits of a second radiator mounted likewise...

Is there depth to mount such radiator with shrouded electric fan to provide adequate airflow ??
Radiators are still front facing theu are rotated along the axis normal to the front face
 
  • #6
Tom.G
Science Advisor
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Sure they can be rotated, both cars and motorcycles used to be built with vertical flow radiators, hot in the top and cool out the bottom.

Since a low hood profile is desired for aerodynamic and esthetic reasons, the cross flow design is currently used. They are probably a little cheaper to build that way, fewer and longer individual tubes needed running the horizontal dimension for a given air flow area.

Just be sure to include an expansion tank (overflow tank) in the design. The vertical flow design had that built into the top tank, but the crossflow design doesn't leave any extra volume in the side tanks.

Just from a flow balancing standpoint, I suggest the radiators be connected in series.
That is {Engine} --> {Radiator#1} --> {Radiator#2} --> {Engine}
That configuration is probably not quite as thermally efficient as having them in parallel, but eliminates all the "extra" stuff to balance the flows.

I noticed your sketch seems to show both inlet and outlet at the top of the vertically oriented radiator. That's not going to work well. Put the inlet at the top and outlet at the bottom.

Let us know how it goes. If you can manage it, some photos of the results would be nice.

Cheers,
Tom
 
  • #7
Ranger Mike
Science Advisor
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Been there many times. We run Formula Car in SCCA. These mini Indy race cars are factory built for racing. Every one we ever ran had cooling problems to some extent. When waiting at the grid to race, idling, no air is moving and these cars are very susceptible to overheating. Typical design has two radiator cores, one per side, covered by the side pod. The most popular design is plumbed parallel so the “ same amount” of coolant runs through each radiator.


You must have an expansion tank mounted higher than the radiators. This is also called a burp bottle. You need this for 2 reasons. To fill the system with coolant as the tank must have radiator cap to permit this. You need this burp bottle to purge trapped air from the entire system. This is done by filling the system and squeezing the rubber ( high temperature silicon in racing) hose to “ burp “ air bubble to the top of the tank. You will have to do this numerous times when first filling the system. Air will remain in the high points of the radiator cooling circuits until displaced by coolant. We ran an electric water pump and this really helped purge the system and cooled the car while idling on the grid even though no air was flowing thru the radiator cooling fins.



We did try running the system in series but felt that this did not benefit and one side would be more cooked than the other side and could cause a reliability problem for the hot side. It did help cut down the ‘ burp time” when we ran the electric water pump but no empirical difference on the cooling.



On these cars flow is everything so read the attached article on duct flow to the side pods. See PDF below on proper way to mount and duct side pods.



https://support.ansys.com/staticassets/ANSYS/staticassets/awc/optimizing-the-cooling-air-flow-of-formula-car.pdf


I wrote about this a while back on this forum.



https://www.physicsforums.com/threads/formula-car-cooling.363502/



One last thing. Ifin you have the word race car in anything you own, you had better be running and oil cooler. Everyone forgets the biggest thing oil does is remove heat from the bottom side of the piston. Yes, lubrication is a big service too but heat is your enemy in racing. Plumb an oil cooler and keep the oil clean.
 
  • #8
11
0
Been there many times. We run Formula Car in SCCA. These mini Indy race cars are factory built for racing. Every one we ever ran had cooling problems to some extent. When waiting at the grid to race, idling, no air is moving and these cars are very susceptible to overheating. Typical design has two radiator cores, one per side, covered by the side pod. The most popular design is plumbed parallel so the “ same amount” of coolant runs through each radiator.


You must have an expansion tank mounted higher than the radiators. This is also called a burp bottle. You need this for 2 reasons. To fill the system with coolant as the tank must have radiator cap to permit this. You need this burp bottle to purge trapped air from the entire system. This is done by filling the system and squeezing the rubber ( high temperature silicon in racing) hose to “ burp “ air bubble to the top of the tank. You will have to do this numerous times when first filling the system. Air will remain in the high points of the radiator cooling circuits until displaced by coolant. We ran an electric water pump and this really helped purge the system and cooled the car while idling on the grid even though no air was flowing thru the radiator cooling fins.



We did try running the system in series but felt that this did not benefit and one side would be more cooked than the other side and could cause a reliability problem for the hot side. It did help cut down the ‘ burp time” when we ran the electric water pump but no empirical difference on the cooling.



On these cars flow is everything so read the attached article on duct flow to the side pods. See PDF below on proper way to mount and duct side pods.



https://support.ansys.com/staticassets/ANSYS/staticassets/awc/optimizing-the-cooling-air-flow-of-formula-car.pdf


I wrote about this a while back on this forum.



https://www.physicsforums.com/threads/formula-car-cooling.363502/



One last thing. Ifin you have the word race car in anything you own, you had better be running and oil cooler. Everyone forgets the biggest thing oil does is remove heat from the bottom side of the piston. Yes, lubrication is a big service too but heat is your enemy in racing. Plumb an oil cooler and keep the oil clean.
Thank you for suggestion, these reports and artciles were very helpful,also i can't use oil cooler.
 
  • #9
11
0
Sure they can be rotated, both cars and motorcycles used to be built with vertical flow radiators, hot in the top and cool out the bottom.

Since a low hood profile is desired for aerodynamic and esthetic reasons, the cross flow design is currently used. They are probably a little cheaper to build that way, fewer and longer individual tubes needed running the horizontal dimension for a given air flow area.

Just be sure to include an expansion tank (overflow tank) in the design. The vertical flow design had that built into the top tank, but the crossflow design doesn't leave any extra volume in the side tanks.

Just from a flow balancing standpoint, I suggest the radiators be connected in series.
That is {Engine} --> {Radiator#1} --> {Radiator#2} --> {Engine}
That configuration is probably not quite as thermally efficient as having them in parallel, but eliminates all the "extra" stuff to balance the flows.

I noticed your sketch seems to show both inlet and outlet at the top of the vertically oriented radiator. That's not going to work well. Put the inlet at the top and outlet at the bottom.

Let us know how it goes. If you can manage it, some photos of the results would be nice.

Cheers,
Tom
Previously i used series connection, the problem was insufficient cooling done by 2nd radiator ,hence i was thinking about using them in parallel or using a single big equivalent.

Also, here's a pic of my radiator fan (stock),
To me it looks in efficient somehow, please suggest something i can do for better performance.
IMG_20180819_190626.jpg
 

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  • #10
Tom.G
Science Advisor
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1,805
Previously i used series connection, the problem was insufficient cooling done by 2nd radiator ,hence i was thinking about using them in parallel or using a single big equivalent.
Yes, the second series radiator won't dump as much heat because its inlet temperature is lower, that's why I mentioned not quite as thermally efficient. Since you've already found that to be a problem I agree that bigger or parallel radiator(s), or fans are needed.
Also, here's a pic of my radiator fan (stock),
To me it looks in efficient somehow, please suggest something i can do for better performance.
I agree, it certainly looks non-ideal. The mounting, with its 90° bend in air flow, is a problem. Take a look at the fan configuration in a car, straight thru air flow using a shrouded (ducted) fan. Some vehicles have two fans next to each other when the radiator has a high aspect ratio, wide but short (which yours seem to be). The shroud increases the fan efficiency by 10% or more.

I recommend mounting the fan with some struts, allow straight thru air flow, and a duct around the fan blades. For maximum cooling, a shroud could be constructed so that the fan(s) pull(s) air thru the full radiator surface.

Note that vehicles with electric coolant fans often have a temperature actuated switch installed in the bottom of the radiator. That way the fans run only when needed.

Tom
 
  • #11
11
0
Yes, the second series radiator won't dump as much heat because its inlet temperature is lower, that's why I mentioned not quite as thermally efficient. Since you've already found that to be a problem I agree that bigger or parallel radiator(s), or fans are needed.

I agree, it certainly looks non-ideal. The mounting, with its 90° bend in air flow, is a problem. Take a look at the fan configuration in a car, straight thru air flow using a shrouded (ducted) fan. Some vehicles have two fans next to each other when the radiator has a high aspect ratio, wide but short (which yours seem to be). The shroud increases the fan efficiency by 10% or more.

I recommend mounting the fan with some struts, allow straight thru air flow, and a duct around the fan blades. For maximum cooling, a shroud could be constructed so that the fan(s) pull(s) air thru the full radiator surface.

Note that vehicles with electric coolant fans often have a temperature actuated switch installed in the bottom of the radiator. That way the fans run only when needed.

Tom
Sure , I'll get new shrouds for that.

Do i need a bigger pump for a bigger radiator?
And if i use parallel connection do i need some kinda extra pump?
As my engine(400cc) and radiator are quite small.
 
  • #12
Tom.G
Science Advisor
3,054
1,805
And if i use parallel connection do i need some kinda extra pump?
Probably not. (But that is pure opinion!)
Do i need a bigger pump for a bigger radiator?
It depends on where the limiting factor for cooling occurs.
  • If the coolant flow rate is being limited by the internal engine cooling channels a bigger pump won't help, you will just get cavitation in the pump. If the flow rate is limited by the radiator(s)/plumbing a bigger pump would help, until the increased pressure bursts a radiator; the pump would also require more power.
  • If the cooling is limited by air flow thru the radiator(s) then higher volume fans/better shrouds/ducting would help. You could also get better cooling by using radiators with a different aspect ratio. The current one has the core flow channels running the long dimension of the radiator. Replacing that with a same size radiator having flow channels running the short dimension would marginally improve efficiency if keeping the coolant and air flows constant. Increased efficiency come from lower coolant backpressure; and maybe heat transfer to the air would be improved; but again, that last part is a conjecture on my part. There are folks here at PF who could give a definitive answer for the heat transfer to air at different radiator configurations, maybe one of them can chime in.

That's about my limit of knowledge on the subject. Hopefully the more experienced/knowledgable in fluid flow and thermal analysis can take over from here.

Cheers,
Tom
 
  • #13
11
0
Probably not. (But that is pure opinion!)

It depends on where the limiting factor for cooling occurs.
  • If the coolant flow rate is being limited by the internal engine cooling channels a bigger pump won't help, you will just get cavitation in the pump. If the flow rate is limited by the radiator(s)/plumbing a bigger pump would help, until the increased pressure bursts a radiator; the pump would also require more power.
  • If the cooling is limited by air flow thru the radiator(s) then higher volume fans/better shrouds/ducting would help. You could also get better cooling by using radiators with a different aspect ratio. The current one has the core flow channels running the long dimension of the radiator. Replacing that with a same size radiator having flow channels running the short dimension would marginally improve efficiency if keeping the coolant and air flows constant. Increased efficiency come from lower coolant backpressure; and maybe heat transfer to the air would be improved; but again, that last part is a conjecture on my part. There are folks here at PF who could give a definitive answer for the heat transfer to air at different radiator configurations, maybe one of them can chime in.

That's about my limit of knowledge on the subject. Hopefully the more experienced/knowledgable in fluid flow and thermal analysis can take over from here.

Cheers,
Tom
Thank you so much tom, cheers!
 

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