How to work out the area of a circle?...

[Alchemy]

Originally posted by MadDogMe
I like the idea of having two 'small'(1/2 of 'big') rads in parallel rather than one 'big' because it effectivly gives you twice the time water's 'in~rad' comparitivly does'nt it?. Same radiator surface area but flow is cut by half in each one doubling time spent there, how much do you think this equates to cooling capacity?, not double cause it's not directly comparable is it?,flow to BTU(or whatever it is.what does BTU stand for?). it may even be less restrictive. if it's not as restrictive at a lower flow as it is at a higher flow?(Hmm?, they'd equal out though would'nt they?). I don't know about pressure drop though, I'd have thought it would negate itself as long as it rejoins to a 1/2 tube(same as prior to split).

Can someone enlighten me to any mistakes or anything pertinant?, or direct me to a previous post please?(you must get tired of repeating yourselves )...

BTU=British thermal unit, interestingly used almost entirely in America rather than the metric unit of Joules. It's a unit of energy. The more BTUs the radiator can emit, the better.

The general rule is that higher flow rate will lead to better thermal transfer between the fluid and the tubes in the radiator. I've seen cases where this has been suggested to be not true. My specialty is in complex fluid mechanics and not heat tranfer, so I can't say for sure why that is so. I would venture, however, that the problem lies with higher flow rate causing enough friction and creating heat within the fluid, eventually overtaking the benefits of increased heat transfer. That's just a guess, though. If someone wants an educated answer, I should have to have a think about it.

As for the radiators, I'd try to put them in parallel if they are identical. The temperature difference between the fluid in the radiator and the air would be the same, so you'd get the same amount of heat removed from each one. The lower flow rate would represent a decreased heat transfer rate between the fluid and the radiator (a total guesstimate using a Nusselt correlation here tells me you'd transfer ~70% as much heat per radiator) but since you have two radiators in parallel you will have a total heat tranfer increase of 40%. Whether that would be improved over a single, large radiator, I wouldn't really know.

If they are in series, however, you're going to cool the fluid quite a bit in the first radiator and not very much in the second. Not very effective, unless the first radiator is not very effective, such as a tube-and-fin transmission cooler job.

Er, anyway. . .

If this was a bit to techie, I apologize, but I just recently took the first half of my licensing exam and all this stuff is floating around in my head.

Alchemy

[bigben2k]

Welcome to Pro/Cooling!

Since you're in the field (complex fluid mechanics), maybe you might be able to help me with a problem.

Wibble over here