+ Reply to Thread
Page 24 of 34 FirstFirst ... 14 22 23 24 25 26 ... LastLast
Results 231 to 240 of 334

Thread: radiator design

  1. #231
    Senior Member
    Join Date
    Mar 2008
    Location
    Palo Alto, CA
    Posts
    269
    We basically used the stock engine (f4i) setup as a baseline, and took water temps before and after the radiator with no forced convection (no fan) as a worst case scenario. Sized the radiator based on the NTU-effectiveness method from there.

    In terms of weight savings, just for fun we chopped our main rubber coolant line and replaced it with about 18in of aluminum tube with small rubber ends. We saved 1/3lb over the rubber alone.
    Formula SAE: When you just can't get rid of a girlfriend.

  2. #232
    Mark, are you guys a new team? If not, was your cooling system not up to snuff last year? Many on here will say that modeling and calculating a cooling systems efficiency won't get you very close to actual. I tend to agree. I've been doing our cooling system for the past 2 years. I started with no knowledge and had no help from previous teams. If you are like I was, I recommend looking at the stock radiator. You can get rough sizing requirements there. If you don't have or want to use the stock radiator, ATV radiators work well. If the ATV has comparable displacement and the radiator has similar frontal area as the stock one, it should work pretty well on your engine.

    If you aren't a new team and have previous work to go on, where were the shortcomings last year? Increasing cooling efficiency can be done by increasing radiator size or simply better ducting and higher flow fans. You could use two smaller radiators instead of on larger one if space is an issue (this is what I did this year).
    Shaun Kapples
    Mechanical Engineer
    Alumni, FSAE at UCF

  3. #233
    We are by no means a new team here at Rutgers(though this is only my second year on the team). We just had serious cooling issues last year preventing us from finishing endurance at Virginia and Michigan last year (though it was a little more involved than bad cooling at MIS).

    I know its not very accurate to try to calculate everything, but seeing as we just switched over to the honda CBR and had big heat issues the first year we used it, I need something to base my setup off of at least initially. All I have so far is a system that didn't work last year. I will have to take a look at the stock radiator size though as a rough base point.
    Mark
    Rutgers Formula Racing

  4. #234
    I'd recommend as much data gathering as possible to determine what kind of heat loadings you're going to see.

    A couple of thermocouples before and after the engine and radiator(s) will give you heat rejection numbers. Really, even that isn't necessary. We did some really long dyno pulls on a 1500HP superflow chassis dyno, and basically we could look at logged coolant temperature data and watch the increase over time - knowing system fluid mass and a little conservation of energy tells us the heat rejection by the motor. It actually worked out pretty close to Heisler's 1/3 engine horsepower suggestion. After that, do a couple hand calcs just to see what kind of size range you're going to need a radiator in, include an appropriate safety factor, and go.
    Wesley
    OU Sooner Racing Team Alum '09

    connecting-rods.blogspot.com

  5. #235
    Hey i just went through all the post in this article and i really cant understand how to get the area of heat transfer of a radiator core while calculating the NTU( NTU=UA/Cmin)............
    can anyone pls help me out with this????

  6. #236
    Well, the air-side transfer area is the total area of all the fins, (both sides) plus the tubes, (assume negligible losses other than the core)

    The water-side transfer area is the inner wetted area of the tubes.
    Wesley
    OU Sooner Racing Team Alum '09

    connecting-rods.blogspot.com

  7. #237
    Iam new to the cooling systems in my team. Was going thru the posts. I came across Heisler's one third suggestion over heat rejection. Does it mean ideally if the engine generates X BHP the heat absorbed by the cooling water should X/3 for optimum performance?

  8. #238
    It's a generality, but yes.
    In Heywood the following are listed for SI engines at max power.
    Power = 25-28% of fuel energy
    Cooling system = 17-26%
    exhaust 34-45%
    Misc = 3-10%

    Compression ratio and total engine piston area are the largest factors in where a specific engine lies in these ranges.

    The listed values assume steady state, so if you base your cooling system requirements over MAX power(not average), it will be close to 1/3rd of that max.
    'engine and turbo guy'
    Cornell 02-03

  9. #239
    We used the same assumptions that VFR750R did from the Heywood book and came out with a really good cooling system (hottest it got in Cali Enduro was 190F with a 90F+ ambient temp).

    You can look up the lower heating value of the fuel your using and compute how much of the energy is going to be dissipated into the cooling system (17-26%). This has to be done using the mass flow rate of the fuel @ the maximum power RPM (or atleast that would give you worse case). Then you can size your radiator accordingly as far as how many kW of heat dissipation you'll require. I think we even did some calculations on fans and such, but I think we might have went overkill on the fan we chose.
    Lawrence Tech University
    2009 Formula SAE
    Team Captain

    (AKA The Dollar Nazi)

  10. #240
    @ above

    So that means knowing the fuel flow rate @ MAX POWER RPM, its Lower heat value I get to know how much heat is to be rejected. And then knowing the pump capacity i will get to know the water flow rate in the engine block.

    Now the thermostat full valve opening temp of our engine is 95 deg celsius. I just have a doubt.
    Should I take the temp at radiator inlet as 95 deg? And to what temp approx should the water be cooled by the radiator??

+ Reply to Thread
Page 24 of 34 FirstFirst ... 14 22 23 24 25 26 ... LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts