radiator design

[Gyro]

Wesley,

I've just started researching cooling system design, and your post was really informative. Just wanted to say thanks.

[KMan]

hello,
We are a new team in FSAE and this is just our second participation. Last time we had used gsxr-600 and a single pass radiator with 17x12.5x2.4 inch heat transfer area. this time we plan to use two 7x5x1.5 inch rads with 6mm core dia of aluminium tubing and fins. what are the odds of overheating on gsxr engine or other engine of 800cc 40bhp?

[vkarmwar]

guys we are a new team from India, and are running with a honda cbr600 rr engine and our calculations giving us a radiator size of 38 X 30.is this correct??
any help would be really nice http://fsae.com/groupee_common/emoticons/icon_smile.gif

[vkarmwar]

the above was in cm guys http://fsae.com/groupee_common/emoticons/icon_smile.gif

[shark.ashwa]

Originally posted by vkarmwar:
the above was in cm guys http://fsae.com/groupee_common/emoticons/icon_smile.gif

Depends on what you took as the total heat rejected from the engine and also the rejection rate that you are looking at... http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

Regards,
Sharath

[vkarmwar]

as i said we really dont have much data, so we are going with a radiator which we think might work. so you know just for an average 600rr do you think its good enough??

[Rex Chan]

30 by 38cm sounds a bit small for a radiator for a 4 cylinder. What core thickness? What pump are you using to pump water? We run an electric water pump (Davies Craig EWP115), which doesn't flow as much as the stock mechanical pump, so we run a larger radiator (40mm core). What kind of fan (if any) are you running?

Heat exchanger textbooks should cover the basics of sizing.

BTW: asking if something is "correct" sounds wrong. I can tell you would like to know if you're on the right track with sizing your rad. However, you have provided almost no information on what you HAVE done so far, so people can't really help you/give you advice, with no info to work off.

Also, you guys have internet/facebook. You can see other cars (like my own team, Melbourne Uni/MUR Motorsports) to see if you're in the right ballpark. If you're worried about "good enough", bigger is safer, so go with the bigger ones you see attached to FSAE cars.

[Rex Chan]

MUR 2011 Radiator pictures (http://www.facebook.com/photo.php?fbid=10150326929078036&set=a.10150326928683036.348722.559588035&type=3)

You should be able to work out how big our rad is from these pics. More info: downflow/single pass. ADRAD core. 1" hosing. Pacet 11" thermofan (~10A).

I've thought about it some more, and 30x38cm doesn;t sound that small anymore, though it will depend on how much power you plan to make/use.

[RE_Mythic]

Hey guys. I am designing the radiator system this year. I based my calcs from data from last years radiator which was a 10"x13"x1" single pass/core. For our car(600cc F4i), I calculated that a 10"x11"x1" single pass/core should be sufficient. Does this seem reasonable?

Also, where would you buy small radiators like these? I can't seem to find any site that makes them this small.

[Rex Chan]

We get ours custom made at a local radiator shop (Race Radiators in Dandenong, VIC, AUS)

[vkarmwar]

we are using a fan yes. we will be using the stock mechanical water pump. a power of 60hp.
i dont have much details cuz this is the first time for me and my team and we havent got much time to test or any past results as well. so we have decided to start off this time and turn to testing after our first event is done.
but i think i will go with something bigger rather than the 38 X 30. it should work. i just cant make up my mind.

[Rex Chan]

Well, as I said: check how big our 2011 one is, and we run it that big cos we use an eelctric pump. So for a mechanical pump, our rad size might be excessive.

[foza_11]

i have already made the calculation for the radiator dimensions by using COMAPCT HEAT EXCHANGER(by kays and london ),but there is some questions to have about this calculations :
1.the surface area Does the Required Area mean the Surface area on both sides of the radiator OR does it mean the total surface area of the cooling fins and tubes etc. ?

The value that I acquired is 0.6387m^2 which seems to be substantially larger than I expected.
2.also when i get the width of the radiator which is the water flow length is this valve divided by the number of tube per row and the number of passes?
3.some geometrical properties for water side i don't understand how they are calculated or where they can be given ?

[heat exchanger]

Surface should calculate both side and for flow should divide by number of tubes

[heat exchanger]

The gap should be fan and core face approx 4 inch and you can calculate core size by Q = U A MLTD calculation is in some simple staps

[heat exchanger]

YES WE CAN MAKE SMALL RADIATOR IF YOU HAVE GOOD QUANTITY.
Originally posted by RE_Mythic:
Hey guys. I am designing the radiator system this year. I based my calcs from data from last years radiator which was a 10"x13"x1" single pass/core. For our car(600cc F4i), I calculated that a 10"x11"x1" single pass/core should be sufficient. Does this seem reasonable?

Also, where would you buy small radiators like these? I can't seem to find any site that makes them this small.

[RE_Mythic]

I have a question. From a top view, does it matter if the radiator is angled like this ____/____ as opposed to this ____\____ ? Assuming the left side is the front of the car.

\ is the radiator

__the side body of the car

[Rex Chan]

The second method will allow hot air to exit/escape more easily. The first method may trap/restrict air in the sidepod region behind the rad.

[SomeOldGuy]

I'm not guy that designed our cooling system but we have bought our radiators from Saldana for quite a few years. They will build a custom unit for a very decent price and are quick about it. We have had no problems with them ever.

[thescreensavers]

Once we figure out our heat rejection, how do we size a radiator? I have spoke to many radiator manufactures and they have no idea other than to call their core suppliers. What am I missing?

[Dash]

Originally posted by thescreensavers:
Once we figure out our heat rejection, how do we size a radiator? I have spoke to many radiator manufactures and they have no idea other than to call their core suppliers. What am I missing?

A book on heat transfer. I have only read 1 page on this thread and they already referenced a book.

[Aly]

Guys does 1200 cm2 radiator seem resonable for a GSXR600 ... I've made alot of assumptions

[Rex Chan]

Give me more DATA!

Mechanical water pump or electric? Flow rates. How big is your fan? Do you have a fan? How thick is the core? What type of core is it?

1200 cm^2 sounds in the ballpark for OUR system: 40mm ADRAD core, EWP115 (10A, ~40L/min), Pacet 11" fan (10A). At ~30cm width, 1200 gives 40cm height, which sounds right.

[Aly]

Well
we have a mechanical water pump and we are using a fan .
1)I've assumed that water enters at 90C to radiator , and it exits at 83C , i did this assumption because I've read that the usual delta T for water you can get is 9C .
2)I've assumed that ambient air enters at 25C and exits at 30C .
3) The material is Aluminium
4) I've assumed that the max GSXR600 power with restrictor would be 67 HP

that was my assumptions for the system

We have a car radiator from last year but I know nothing about it by it's length and height
and material
i dont know its thickness
i tried to make fins calculations but I'm lost

We are experiencing sever financial problems and some sponsers just decided to change their word and don't give us the money they promised they would due to alot of circumstances in Egypt

We can't even afford to buy a thermocouple thermometer

we decided we'd better use the money we have for things we MUST do (without them we won't get to the fsae at all like the external chasis and some design team stuff )

all i want to figure out know is weather this radiator we have is suitable or not because if not then we will put buying a new radiator on our priorities

i know the theoretical calculation and it's such simple the problem is for fins and also the problem is that i can't measure temperatures.

if only one can tell me the size (Area) of original GSXR600 radiator and we'd get a slightly larger one

PLEASE HELP

[Aly]

The issue is

is 1200 cm2 suitable and logical for our engine
and shall i just take the width and heights of
radiator rectangles and add them then multiply
by 2 (front and rear faces)
and compare to the 1200 cm2 ???

or its totally far since we neglected fins

[Rex Chan]

Short answer: it will work, based on mech pump and fan.

But, I have issues with your assumptions (engineering): 25C is too low an ambient air temp. If you design for a 25C day, then in theory, your car should overheat on a 30, 40, or 45C day. Doesn't it get any hotter than 25C in Egypt??? I would personally design for a 45C day, but this may mean a very large rad.

I hope the max power of 67hp is not the power the cooling system is expected to dissipate. This means that you expect to be running at max power 100% of the time. We design for something like 16-18kW average power.

While I can see you have money problems, engineering only takes your time, and is the while point of FSAE anyway.

PS. DeltaT of 9C is in the right ballpark. From memory, we get DeltaT=4-8C (depends on airflow, I think).

[Aly]

Rez the 25C is based on this temperature graph
http://www.eldoradocountyweather.com/climate/europe/germany/Berlin.html

it indicates that temperature in Berlin doesn't exceed 25C through the year .

of coarse in Egypt it's ALWAYS hotter but we won't run the car much time .... and we will take our precautions during testing not to overheat the car .

As for the 67hp ....
The original max hp of our engine was roughly 93hp .... so I assumed that due to the restrictor the max power would be restricted to about 67 hp ...
I've read that usually designers design the raditor to dessipate about 30% of max power .
so the amount of heat that the radiator is designed to dessipate would be 30% of the 67hp

As for the fan and pump .... we are using the original mechanical water pump coming with the GSXR600 and about 20 cm diamter fan.

are these assumptions yet right or you still disagree .

Give me advice

[Aly]

Rex here is the link to the graphs
ambient temperature graphs (http://www.eldoradocountyweather.com/climate/europe/germany-city-climate-listings-a-z.html)

[Rex Chan]

Well, if 25C IS the max, then ok.

20cm ~ 8" fan. A bit smaller than what I'm used to (we use 11" fan), but with higher water flow, should be fine.

[thescreensavers]

Could the air leaving the radiator be hotter than than the water entering the radiator?

Q= (Flow)* (Specific Heat)(Out - in)

For 300 CFM I got 587.33 kg/s

I solved for "out" temp.

[Z]

Originally posted by thescreensavers:
Could the air leaving the radiator be hotter than than the water entering the radiator?
tss,

Yes, certainly.

And you won't even need any of Maxwell's demons to do it. http://fsae.com/groupee_common/emoticons/icon_smile.gif

Z

[Aly]

hey guys

I just had a strange question from my power team leader

After reporting that the radiator Area 1200 cm2 has been verified to be suitable for our case (I've calculated it and Rex Shan said on the forums roughly its acceptable)

He is asking me : are people on the forums talking about 1200cm2 as the outer area of tubes summed to give this number .

or this 1200 cm2 they're talking about is the length * breadth of the block it self no matter the spaces between tubes .

Can anyone tell me ?

Our case is an GSXR600 engine and i calculated the best area for radiator to be 1200cm2 using assumptions stated in former posts (3 or 4 posts ago)

please help

[Rex Chan]

When I talk area, I mean physical size/dimensions of the radiator core (Length x Width). So, the actual performance WILL depend on number of channels/fins and thickness. That's why I mentioned the "40mm ADRAD core", as that's what we use. I would assume that a thinner core would not transfer as much heat (but might be wrong).

[Aly]

ok that's clear now

the remaining thing is to compare this 1200cm2 to the area of radiator we have ....

I myself estimated this 1200cm2 as the outer area of tubes (heat transfer area) and therefore the length x width area would be even smaller

should i measure the length x width for each single tube and multiply by number of tubes then multiply by 2 for the 2 faces ...

or since 1200cm2 sounds quite suitable then I just calculate the length x width of our radiator block and compare

please help

[thescreensavers]

Originally posted by Rex Chan:
When I talk area, I mean physical size/dimensions of the radiator core (Length x Width). So, the actual performance WILL depend on number of channels/fins and thickness. That's why I mentioned the "40mm ADRAD core", as that's what we use. I would assume that a thinner core would not transfer as much heat (but might be wrong).

Here is a quote from Heinz Heisler book(pg727) that might help.

"Increasing the matrix core depth increases the heat dissipation capacity but this capacity increase becomes much smaller beyond some critical depth. For example, a 50% increase in core depth improves the heat dissipation capacity by 15%, whereas a 100% increase in depth raises its capacity by only 20%"

[Aly]

guys , now I can say our radiator is suitable for our case http://fsae.com/groupee_common/emoticons/icon_smile.gif thank you .

An important case now is that we are using a turbo charger .
the turbo is mainly cooled using oil. and there is a backup water cooling for the turbo when something goes wrong with the oil cooling or its over heated .

Due to shortage of fund and to save some weight
I thought that :

Why don't i make the water tank from a metallic material (higher heat transfer coefficient ) and mount the thermoelectric refrigeration cells (peltier cells) ..... they basically create a delta T ...
They should work when there is an overheating issue .

I want to hear you opinions http://fsae.com/groupee_common/emoticons/icon_smile.gif

[thescreensavers]

Using the LMTD method, how do you figure out the Heat Transfer Coefficient "U"?. Core manufactures don't know and what I been told here is that it is experimentally found.

How are you guys figuring it out?

[foza_11]

ok, the question here is that the max. load for cooling is 20 KW ( 1/3 HP of engine ) OR 60 KW (=HP of engine ).
for the second case i want fan with 1811 CFM which is unlogic .
thanks for your help

[Rex Chan]

One third (approx) of fuel that goes into the engine (chemical energy) gets turned into mechanical work. Another 1/3 goes to cooling system; last 1/3 goes out the exhaust. Thus, at a peak power of 60kW, there is another 60kW of exhaust heat, and 60kW going into the cooling system. Thus, you are using ~ 180kW of fuel.

However, when driving, you are not using/needing 60kW continuously (maybe in FSAE Boating). We calculated that our 2011 cooling system dissipates about 15kW of heat, so that means (on average), we only use/need 15kW of power from our engines.

Short answer: if you only use the cooling system for driving an FSAE style track, ~20kW is enough. If you dyno tune your engine in your car (i.e. chassis dyno), you'll need something bigger, otherwise you won't be able to hold peak power for very long. Our engine dyno can EASILY keep the water cool at peak power (50kW for us), so I'm guessing has heat removing capacity of 100kW+.

[Rex Chan]

We just did a flow test on the Honda CBR600RR (03-06) mechanical water pump.

Raw data is here: MUR 2012/Melbourne Uni FSAE: CBR600RR Mechanical Water Pump Flow Test/Rate (http://www.facebook.com/photo.php?fbid=10150813205108036&set=a.10150813204983036.409754.559588035&type=3)

Sorry for the spam. Now, people can stop asking this very common question. But you should still do the test yourself.

[Thomas123]

Rex,

Am i right to assume that the rpm values from your test are engine rpm? Therefore they need to be adjusted via the drivetrain primary reduction ratio?

[Rex Chan]

Yes, the "RPM" are Engine Speed. Thus, to get water pump speed, you will have to account for any reductions. I *think* it's 2:1, but not 100% sure.

[star]

Have you guys made any attempts to find oil flow rates?

[Rex Chan]

No. why do you need it?

[star]

I am attempting to size the oil cooler.

[Rex Chan]

Sorry, can't help you there. We run CBR600RR with stock oil-water cooler. Based on your posts, you run an Aprilia? Run what they run stock??

[star]

Hi Rex,

Yes we run Aprilia. The stock oil reservoir on the bike also functions as an oil-air cooler. The oil is also gravity fed, which means that the reservoir would have to be mounted above the engine; and for good airflow it has to be mounted up high if it is to be used as an oil cooler as well. A problem with packaging.

[Wesley]

The reservoir doesn't necessarily have to be above the engine. Review the dry sump circuits and a pressure transducer will tell you as much.

As for an oil cooler on an Aprilia, at least in our case, without an oil cooler we ended up on the verge of overheating and oil temps over 250 deg.

Because the stock system works with the tank mounted directly in airflow, where ours was packaged in a very hot engine compartment, I found the smallest oil cooler we could, a 5x5" tube and fin from an ATV, figuring the surface area significantly greater than that of the oil tank, even at that small a size.

It made a huge difference. Oil temps were down 40 deg to 210-220F, coolant temps were drastically improved, and everyone felt a lot better about the engine lasting through comp (as I recall, it has made it through at least 2 seasons)

We did this at the last minute while testing about a week before the Cali competition when the temps got pretty hot outside and cooling became an issue. That was a fun explanation to the judges, the oil cooler zip tied to the frame. http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

If I were to do some sizing work, I'd get ahold of an Aprilia pressure pump and build a cheap flow rig to test flow rate at operating pressures. We also ran it on the suction side of our pressure pump to avoid aeration and decreased cooling efficiency. Heck, you could even heat the oil and run it directly through the cooler and get some actual rejection numbers from your cooler.

[jlangholzj]

Its also never a bad idea to evaluate the results. I finally got around to looking at the data we got from lincoln and expected matched actual pretty well. Which is always good! It did also re-confirm a few things I had suspected about the system.

Our right side rad was on the pump side of the motor and as a result I'd suspect it would have a slightly higher water flow rate. We showed an additional 2-4 HP of rejection on the right side over the left. This also was apparent in that the hot side temps were similar while the cool side temps were slightly different. Keep in mind this was with one mechanical too, stressing the point of having two electrical pumps for proper flow.

Also for flow rate of the oil, shouldn't you be able to use Bernoulli's equation to calculate that? I'm assuming you're cooler is on the high pressure side of the oil pump, and you should know the diameter of the tubing coming out of your motor.

[Eduardo Malhano]

I´m new here but I was working with radiator design for my FSAE team since january.

I had already designed a radiator with 200x200x70 mm. I calculated the parameters of a Honda civic 1.6 radiator that was usefull for our project and then I modified some parameters until I get this geometry. I did this in Excel.

But I "jumped" some steps and I am back now to improve my presentation in FSAE competition. And I also have some questions.

First of all, we use a honda CB600 2006 engine and I have some difficulties to find the Q.

Q = 0,25Qi, where
Qi= Ch x PCI x N /3600 where Ch is fuel consumption in kg/h, PCI is inferior calorific power and N is combustion efficiency,
I use 96% in N and 43000 KJ/Kg in PCI, but what I use in CH? We dont run yet.

Other parameters, I use 0,7kg/s for water pump flow and for the air flow I tried m=?.A.v where A is the area of air flow and v is the speed of fan. I used 13 m/s but I dont know if is that right.

If somebody could help me..

In the end of the project, I used 98°C in the water inlet and 30°C in the air inlet.
I found 89°C in water outlet and 58°C in air outlet.

Regards,

[Rex Chan]

I might be able to help you with Q: I think you need all 4 fluid temps to work it out (radiator water in, radiator water out, ambient air (air into radiator), and radiator air out). I have logged such data for a long time on our 2011 FSAE car (CBR600RR 03-06, with EWP115, and custom radiator - see my fb for pics of how big it is). EMail me for access to this data.

In general, I found a delta water temp of 4-8C. We were getting very high rad air out (using the AT section of a Bosch MAP/AT sensor with it's exposed tip), so I have recently logged a TC through a MoTeC E888 to check.

Again, email me for data.

[jlangholzj]

We all know that core-mounting fans to your radiators is generally not good but here's just how bad it is:

http://i260.photobucket.com/albums/ii35/jlangholzj/IR_5251.jpg

the temperatures themselves aren't 100% accurate due to emissivity but this give you an idea on how much of a hotspot you get when core- mounting.

this was just the pirmary test done with our dual-pass radiator from last year. inlet is top left and outlet is top right.

I hope to get some more testing done with this before school but i though you guys might find it cool.

[HelioRicardo]

In which RPM is this radiator operating? Because 78 degrees is not to much hot.. Und what is core-mounting??

I´m the Eduardo Malhano in top of this page, but now I login in my account.

[jlangholzj]

Its amazing what a little bit of googling can do
http://trendgears.com/ebay/MiragePower/Performance/Radiator/Radiator-Fan-Civic.jpg

THIS is a core mounted fan, no shroud, no diffuser, just a fan mounted to the core of the radiator.

The point of the picture wasn't a cooling issue, in fact its on a radiator dyno to test different water pump flow rates and different radiator configurations. Water temp is heated by a burner up to about boiling and then the effects are measured via several sensors. Heat rejection is then easily calculated.

The point of the picture was to demonstrate that core mounting the fan gives about a 15*C temperature differential and that it also effectively lowers the AVG air CFM through the core, both factors are major hits on cooling efficiency

[HelioRicardo]

Hey Folks,

I'm attaching photos of my radiator and fan.
I need that you guys help me to think about some way to fix these two parts. Any idea?

http://imageshack.us/photo/my-...1/20121016175955.jpg (http://imageshack.us/photo/my-images/651/20121016175955.jpg)
http://imageshack.us/photo/my-...5/20121016180002.jpg (http://imageshack.us/photo/my-images/545/20121016180002.jpg)
http://imageshack.us/photo/my-...5/20121016180007.jpg (http://imageshack.us/photo/my-images/15/20121016180007.jpg)
http://imageshack.us/photo/my-...3/20121016180029.jpg (http://imageshack.us/photo/my-images/823/20121016180029.jpg)
http://imageshack.us/photo/my-...5/20121016180039.jpg (http://imageshack.us/photo/my-images/155/20121016180039.jpg)
http://imageshack.us/photo/my-...4/20121016180105.jpg (http://imageshack.us/photo/my-images/844/20121016180105.jpg)
http://imageshack.us/photo/my-...6/20121016180121.jpg (http://imageshack.us/photo/my-images/856/20121016180121.jpg)

Thanks!!

[jlangholzj]

Originally posted by HelioRicardo:
Hey Folks,

I'm attaching photos of my radiator and fan.
I need that you guys help me to think about some way to fix these two parts. Any idea?

http://imageshack.us/photo/my-...1/20121016175955.jpg (http://imageshack.us/photo/my-images/651/20121016175955.jpg)
http://imageshack.us/photo/my-...5/20121016180002.jpg (http://imageshack.us/photo/my-images/545/20121016180002.jpg)
http://imageshack.us/photo/my-...5/20121016180007.jpg (http://imageshack.us/photo/my-images/15/20121016180007.jpg)
http://imageshack.us/photo/my-...3/20121016180029.jpg (http://imageshack.us/photo/my-images/823/20121016180029.jpg)
http://imageshack.us/photo/my-...5/20121016180039.jpg (http://imageshack.us/photo/my-images/155/20121016180039.jpg)
http://imageshack.us/photo/my-...4/20121016180105.jpg (http://imageshack.us/photo/my-images/844/20121016180105.jpg)
http://imageshack.us/photo/my-...6/20121016180121.jpg (http://imageshack.us/photo/my-images/856/20121016180121.jpg)

Thanks!!

Fix as in somethings wrong that needs to be changed or fix as in mounting it somewhere?

[HelioRicardo]

In somewhere new.

[Phil1988]

Im wondering a bit about the fan mounting.

So if i don't mount the fan directly on the core.

I assume as a example: A cooler with the dimensions of 300*200 and a fan with a diameter of Ø180mm. So i have to laminate a duct to the fan. Maybe with a gap of 60mm between the core an the fan.

I learned to get the best efficeny of the cooler the outlet of the air duct shoulb be twice as big as the inlet? so how to do that with the duct for the fan?



Regards Phil

[jlangholzj]

Originally posted by Phil1988:
Im wondering a bit about the fan mounting.

So if i don't mount the fan directly on the core.

I assume as a example: A cooler with the dimensions of 300*200 and a fan with a diameter of Ø180mm. So i have to laminate a duct to the fan. Maybe with a gap of 60mm between the core an the fan.

I learned to get the best efficeny of the cooler the outlet of the air duct shoulb be twice as big as the inlet? so how to do that with the duct for the fan?

Regards Phil

Where did you hear that? I've never been aware of anything of the sort. I've heard of diffusers(your inlet being smaller) but having an outlet twice as large 0_o. I guess it would be serving the purpose of a diffuser as well...only on the back side..hmmmm..*scratch head*

[Phil1988]

Sorry. i mistaken something^^ the statement with the area of twice as large wasn't right. I was a bit jazzed^^..

So but if i mount the fan not direct on the core. i have a big nozzle. All the airflow has to pass trough the fan. If its turning or not. That must produce lots of pressure loss? Do you have any thermal image where the fan isn't mounted directly on the cores? Any experience?

Regards Phil

[jlangholzj]

Originally posted by Phil1988:
Sorry. i mistaken something^^ the statement with the area of twice as large wasn't right. I was a bit jazzed^^..

So but if i mount the fan not direct on the core. i have a big nozzle. All the airflow has to pass trough the fan. If its turning or not. That must produce lots of pressure loss? Do you have any thermal image where the fan isn't mounted directly on the cores? Any experience?

Regards Phil

Unfortunately life got in the way (aka capstone project at school) so my testing has been tabled until semester break. You are correct in that you'll effectively have a nozzle but I haven't had a chance yet to measure any effects on the pressure drop. What I CAN say, is that it provides an increased avg core CFM. We taped off the core in 1" squares and measured the apparent air speed with an anemometer. Core mounting really hurts this. From my understanding the shroud doesn't need to be very far away either (again, not had time to test it quite yet).

Its actually quite painfull, I almost have everything put together to test but I just plain don't have the time http://fsae.com/groupee_common/emoticons/icon_razz.gif

[Phil1988]

I have the problem of deciding whats the best at the moment.

My cooler has the dimensions of 300 *200 mm.

I decidet to take a fan with an diameter of 180mm to make the pressure loss as a minimum. But a 180mm fan would not be neccecarry. So its overdimensioned.

regards Phil

[Jish in China]

Has anyone thought about the value of K, heat transfer coefficient? or the range? need ur help~!thank u in advance!

[Harry Clegg]

I have recently tested a VW Polo radiator, with core dimensions of 480*320*33 and found it to have a coefficient K in the region of 21.

heres the data I used:

Water Inlet = 58.9, Water outlet 51.2, (Giving Delta Tw of 7.7Kelvin) delta T air was 4 K. Mass flow rate of water 8.8Kg per minute. Mass flow rate of air 1.01Kg/second.

Hope this helps!

[jlangholzj]

Originally posted by Jish in China:
Has anyone thought about the value of K, heat transfer coefficient? or the range? need ur help~!thank u in advance!

The actual overall value of your heat transfer coef. "k" of the system persay depends on a lot of different things. Like the Reynolds number through the core, your fin geometry as well as a few other things. The actual heat transfer coef. used IN THE CALCULATIONS should be readily available through any heat transfer textbook.

[BigBoss]

Can anyone shed light on how they decided to apply a Factor of Safety to their sizing/design? What are some common values/ranges? Have Design Judges inquired why your FOS was too high?

[Warpspeed]

Direct mounting the fan onto the core is very bad.

A very significant part of the core gets no forced air help at all, and the small area that does get all the forced air exhibits a higher air pressure drop.

If you have the space to do it, fit a decent air box right over the core, on the down stream side of the core, and fit your extraction fan into that.
Something like this maybe...
http://www.coolcraft.com/skin/frontend/default/default/images/media/shroud%20with%20fan.jpg
The advantage is that you get a very even airflow over the entire core surface area, and higher mass airflow through the fan, because it has less differential pressure to work against.

If the fan blows onto the core, even with an airbox, the flow will still be somewhat uneven unless the air box is enormous.

[BigBoss]

Hi All,

I'm trying to reason through a radiator sizing script, based on BeaverGuy's prescriptions. Say I know the average heat rejection that I would like to dissipate, as well as all the temps, the mass flow rates of the coolant and air, heat capacity.

1.) Ch & Cc; find Cmax & Cmin of the 2; find Cr
2.) Find Qmax
3.) Find effectiveness; Qneeded/Qmax
4.) Find NTU based on Cr & e
5.) Guess a U
6.) NTU = UA/Cmin ; re-arrange so Aguessed = NTU*Cmin/Uguessed

Qhttp://fsae.com/groupee_common/emoticons/icon_biggrin.gifoes U & A combination reject enough heat?

1b.) calculate Cc & Ch based on guessed A
2b.) calculate Cr, NTU, e
3b.) If we know Cmin from 1b.), we can find the new Qmax
4b.) From all the above, we can find the new, actual Q rejected
5b.) Check: Does new Q act ~ target Q act? If so, A & U is correct; otherwise iterate.

[BeaverGuy]

Originally posted by BigBoss:
Hi All,

I'm trying to reason through a radiator sizing script, based on BeaverGuy's prescriptions. Say I know the average heat rejection that I would like to dissipate, as well as all the temps, the mass flow rates of the coolant and air, heat capacity.

1.) Ch & Cc; find Cmax & Cmin of the 2; find Cr
2.) Find Qmax
3.) Find effectiveness; Qneeded/Qmax
4.) Find NTU based on Cr & e
5.) Guess a U
6.) NTU = UA/Cmin ; re-arrange so Aguessed = NTU*Cmin/Uguessed

Qhttp://fsae.com/groupee_common/emoticons/icon_biggrin.gifoes U & A combination reject enough heat?

1b.) calculate Cc & Ch based on guessed A
2b.) calculate Cr, NTU, e
3b.) If we know Cmin from 1b.), we can find the new Qmax
4b.) From all the above, we can find the new, actual Q rejected
5b.) Check: Does new Q act ~ target Q act? If so, A & U is correct; otherwise iterate.

Wow, people are still referring to what I did a 8 or 9 years ago.

From what I recall, that is the basic method that my sizing script used. The initial guess at U was programmed in because there is a relatively small range of U for an automotive radiator. You will also need a few tube and fin parameters so that you can calculate the air side heat transfer parameters because fins aren't 100% efficient and to calculate the size of the core.

Later on I started using only an evaluation script. I abandoned calculating the core size. I picked tube and fin configurations and core size then just calculated Qact and ensured it was sufficient for the heat load. I did this for two reasons, the code was much shorter thus easier to check, I discovered a number of errors when the code was about a year and a half old, and solved much faster though that was a only a difference of a few seconds versus 1- 2 minutes.

The sizing script had a pair of nested iteration loops. The outer loop Calculated Qact on Uguess and Aguess and compared Qact to Qneed. The inner loop calculated Aguess based on Uguess, Qneed, and the tube and fin geometry. This made it somewhat slow to converge and also unstable in some situations.

[BigBoss]

BeaverGuy,

Hmm, interesting. My script utilized only 1 while loop that encompasses the entirety of the b portion. Although, I am having trouble converging. My U guess would start would say, 200 W/msqrd*K, and the program would ideally change the U based on what Part B would tell me (as well as the A combo).

As for converging, yup. It's sticky as hell. I would change the U initial from 200 to 25, and my Q rejected would change by a very, very small percentage until the program will exhaust itself of a feasible U value. Must be something I'm missing...

[BigBoss]

The only thing(s) that could change in section B are Cmin & Cmax, since you are going through different U & A values, the cold side C is a function of A (i.e. mass flow rate equals rho*A*Velocity), the hot-side C can be recalculated through an energy balance.

EDIT: Of course, the e, NTU and Qmax would also change from Cmin, Cmax.

[matsho]

i want to help me to make a design of radiator for our formula project plzz
how i designed it and the parameter of it

[jlangholzj]

Originally posted by BeaverGuy:
Later on I started using only an evaluation script. I abandoned calculating the core size. I picked tube and fin configurations and core size then just calculated Qact and ensured it was sufficient for the heat load. I did this for two reasons, the code was much shorter thus easier to check, I discovered a number of errors when the code was about a year and a half old, and solved much faster though that was a only a difference of a few seconds versus 1- 2 minutes.


This is what my current script does in EES for our radiator sizing. I've not had a chance to actually make an iteration loop and may try that in matlab. (I'm assuming that matlab uses resources considerably better than EES does) The current file works rather well and compliments the use of fan pressure curves as well as a few other lookup tables.

doesn't change a whole lot in 8-9 years does it http://fsae.com/groupee_common/emoticons/icon_smile.gif

as an edit:

I went back and looked at some of your earlier posts....strangely enough the "compact heat exchangers" book is also what I've used as a reference with making our project and the NTU equation.

Further expanding on this I've had a chance to verify the design with some track data and its within 5% of the expected design...fits pretty darn well!

[jlangholzj]

Originally posted by matsho:
i want to help me to make a design of radiator for our formula project plzz
how i designed it and the parameter of it

and you're REALLY going to do this???? There's 16-17 PAGES of great information in here...and you're going to post in the thread with AALLLLllll that information....and beg for it...

http://www.badhaven.com/wp-content/uploads/2012/02/picard-facepalm.jpg

[jjnoble]

Does anyone have any information on sizing radiator lines? Knowing my coolant temp and flow rate is there a way to properly size the hose?

[jd74914]

You are going to want to size your lines for pressure drop. In general, more water flow through a radiator is directionally better, so you want to size the lines for minimal pressure drop to avoid moving downward in the pump curve.

[jlangholzj]

You are going to want to size your lines for pressure drop. In general, more water flow through a radiator is directionally better, so you want to size the lines for minimal pressure drop to avoid moving downward in the pump curve.

generally an excellent practice. I did however take a look at ours (we ran a twin radiator setup) because I was concerned that since the one set of tubes were longer than the other, that we'd see excessive pressure drop in the longer side, leading to reduced flow in that particular radiator. I found that at the 1" tube that the bike runs its ~negligible. I also place a paddle flow meter in line with the system at both the pump and each of the two radiators...again...pretty minimal.

What I'm venturing to guess is happening (just an educated guess here) is that if you look at the pressure drop of the lines vs the pressure drop of the radiator core, the drop in the core is going to be significantly higher than say the lines. what I'd really like to see though is do the analysis Jim is talking about and see how much smaller we can go without overly restricting flow :)

[xander18]

I need to design a cooling system can anyone tell me how?!?!

....

Just kidding. I've read this whole thread and some literature as well. I'm going to make a Matlab program similar to what BeaverGuy used (outlined here: http://www.fsae.com/forums/showthread.php?2664-radiator-design&p=27076&viewfull=1#post27076). One issue: what function to use to get NTU (step 4 in the quoted post I linked to)? I'm looking at the charts in this PDF (http://educypedia.karadimov.info/library/98254.pdf) or available in any thermal textbook. Unless there's an existing function for this I'll just extrapolate a number of points from this and create a 3D fit plot in Matlab.

Edit:
So I found this like 10 minutes after I made this comment. Whoops.
http://www.mathworks.com/matlabcentral/fileexchange/44858-heat-exchanger-solver/content/effectiveness.m

Since this thread has been so helpful for me, I'll try to give back a little bit. A thesis called "Cost Effective Method for the Evaluation of a Formula SAE Engine Cooling System" is available on the U of Illinois website (https://www.ideals.illinois.edu/bitstream/handle/2142/14676/1_Korczak_Paul.pdf?sequence=3). It has a lot of good empirical data for Thi, Tho, Tci, Tco, coolant flow rates for an F4i, and air velocity with various levels of ducting and fans. I used the data in this paper as a test data set for some of the Matlab calculations I'm doing. Also, other teams running an F4i will probably be able to directly use some of this data. Other cooling system designers may find it useful.

[mshorter]

I'm tasked with designing the radiator for the Brown University 2015 car and have read through the thread but still have a few lingering questions. Firstly, how do teams design radiator/cooling systems for both the noise event/static testing, where the engine is run at or near redline for extended periods of time with no airflow to the radiator and events like enduro where we can rely to some extent on air being forced through by the motion of the car. Currently, the fan has power supplied from the ECU only when the coolant reaches a certain temperature, so we are not constantly drawing obscene amounts of power from the alternator, but of course designing for a static car leads to a heavier radiator. However, one advantage of running a very large fan is immediate cooling response if needed...

Is there any consensus towards pulling air through the radiator or pushing it? Our team has been running a pusher but some people in this thread are saying that pullers are better for airflow while the car is moving. For reference, we are using this fan https://webstore.spalusa.com/content/files/content/PDF/30103202_3206_SPEC.pdf

Also, are there any resources on CFD/other methods for optimizing ducting/the airflow through the radiator? I've seen references to possibly using CFD but nothing useful so far.

[Swiftus]

...but of course designing for a static car leads to a heavier radiator. However, one advantage of running a very large fan is immediate cooling response if needed...

mshorter - Welcome! It is always good to see new people getting involved on the forums!

Which team are you from?

Before just giving you an answer, I would ask you to reconsider the source of the heat you are trying to reject. Is the heat necessary for rejection directly proportional to the RPMs of the engine? If not, then in what case(s) would it diverge?

[mshorter]

Before just giving you an answer, I would ask you to reconsider the source of the heat you are trying to reject. Is the heat necessary for rejection directly proportional to the RPMs of the engine? If not, then in what case(s) would it diverge?

I'm from Brown University and this is my second year on the team but my first year actually doing design work. I'm not a powertrain expert by any means, but I'm pretty sure that the engine power is divided among the exhaust, coolant/oil (someone else is doing oil on my team), and the drivetrain itself. Since horsepower is positively correlated with RPM, RPM should be the primary driver of heat to the radiator, but I'm having a hard time figuring out how that might be effected by other factors, unless running the engine at high rpm at idle means that power is going out the exhaust and water hose instead of the drivetrain. I can talk to our team's powertrain people about it.

[Swiftus]

Matthew - You have what sounds like a pretty fun project. I would like to you to remove some pressure from yourself by admitting now that you will never find an exact solution. It does not mean that you won't find a great solution for your car, it just means that it cannot be 'optimised'. Computers doing trillions of calculations in CFD still get it very wrong. Hand calcs with good factors of safety should be your primary driver on your design.

Additionally, have you started researching general engine theory or cooler design much? Back in the depths of this thread are a lot of good, free literature resources that may prove invaluable in your learning and understanding of your system. I know that a number of them have been helping me stumble through my formula career.

On to some fun stuff. You sound like you have heard the energy conversion in thirds assumption. The assumption goes, the amount of energy extracted from the fuel which is burning in a spark ignition engine is split evenly into 3 pathways: 1/3 is delivered as mechanical work via the crankshaft, 1/3 is moved through the exhaust, and 1/3 is emitted as heat into the cooling system. So, if you are seeing 75 HP at the crank, you have 75 HP to reject from your coolers. Thats (75hp x ~750Watts/hp) ~56000 Watts! Compare that to the amount of heat you can feel off the end of a 1500 Watt heat gun and you can see how big of a task the coolers have to do (56000/1500 ~37 Heat guns!)

So now you know the heat that needs rejection at maximum power.

Review the power and torque curves in the image below

http://image.sportrider.com/f/18817320/146_03+sportbike_performance_dyno_charts+yamaha_YZ F_r6_horsepower_torque.jpg

D (http://image.sportrider.com/f/18817320/146_03+sportbike_performance_dyno_charts+yamaha_YZ F_r6_horsepower_torque.jpg)oes the power keeping going up for all RPMs? Do you think more or less heat is being generated when the power starts to drop?

If I were to tell you that RPMs are not indicative of heat emitted by the engine, what other parameter might be a better fit?

[sid]

hey we are using a cbr 250 engines and cbr 600 radiators but cannot decide on the fans to be used any suggestion on how to go about it

[jlangholzj]

Matthew - You have what sounds like a pretty fun project. I would like to you to remove some pressure from yourself by admitting now that you will never find an exact solution. It does not mean that you won't find a great solution for your car, it just means that it cannot be 'optimised'. Computers doing trillions of calculations in CFD still get it very wrong. Hand calcs with good factors of safety should be your primary driver on your design.

Additionally, have you started researching general engine theory or cooler design much? Back in the depths of this thread are a lot of good, free literature resources that may prove invaluable in your learning and understanding of your system. I know that a number of them have been helping me stumble through my formula career.

On to some fun stuff. You sound like you have heard the energy conversion in thirds assumption. The assumption goes, the amount of energy extracted from the fuel which is burning in a spark ignition engine is split evenly into 3 pathways: 1/3 is delivered as mechanical work via the crankshaft, 1/3 is moved through the exhaust, and 1/3 is emitted as heat into the cooling system. So, if you are seeing 75 HP at the crank, you have 75 HP to reject from your coolers. Thats (75hp x ~750Watts/hp) ~56000 Watts! Compare that to the amount of heat you can feel off the end of a 1500 Watt heat gun and you can see how big of a task the coolers have to do (56000/1500 ~37 Heat guns!)

So now you know the heat that needs rejection at maximum power.

Review the power and torque curves in the image below

http://image.sportrider.com/f/18817320/146_03+sportbike_performance_dyno_charts+yamaha_YZ F_r6_horsepower_torque.jpg

D (http://image.sportrider.com/f/18817320/146_03+sportbike_performance_dyno_charts+yamaha_YZ F_r6_horsepower_torque.jpg)oes the power keeping going up for all RPMs? Do you think more or less heat is being generated when the power starts to drop?

If I were to tell you that RPMs are not indicative of heat emitted by the engine, what other parameter might be a better fit?

Awesome points!

Also, (directed towards matthew) how does that "power" output change with load on the engine? Say that I personally can bench-press ~200lbs. If I press ~50lbs I still have the same potential to lift those 200lbs but will be sweating considerably less than if I were lifting 200lbs....see where I was going with than analogy? Hopefully that should answer your "dynamic vs static" event question.