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

[MadDogMe]

That's all folks . I slept through maths at school, and my memory gets selective after 16 years ...

[Cathar]

r = radius = half of the circle diameter (distance across the circle at the widest point

area = 3.14159265 * r * r

eg. if your circle is 9mm across

the area is 3.14149265 * 4.5 * 4.5 ~= 63.6 mm^2

[tinman5555]

Try Pi*R², that's 3.14 x (Radius x Radius)

[bigben2k]

Here's an easy reminder:

pi R 2 = area

2 R pi = perimeter

The order is simply reversed (2*R*pi <> pi*R^2). The one that's squared is the area formulae, since area is measured in units^2 (square).

[MadDogMe]

Is the '*' key usualy used to indicate multiplication in equations?. I only just found out that ^ is squared thanks to Cathar recently ...

Thanx people! ...

[bigben2k]

Yes.

* is multiplication
^ is to indicate an exponent (^2 is "squared", ^3 is "cubed", ...)

Now I know that you don't do any programming!

[dreamie]

Pi = 22/7

the formula is Pi * Radius * Radius, or (Pi)(R(square))
To find area, just get that area multiply by the height.

[MadDogMe]

To find area, just get that area multiply by the height

Do you mean to find 'cubic' area?...

Thanks!, another useful bit of knowledge ...

I'll be trying to find out how to 'equalise' flow over a radial block design soon by balancing the size of the holes around it, (cause the outlet will be off centre). I'll need some help with that I think, especialy designing the fin patern over the core. I was thinking of something that'd look abit like a lemon/orange juice squeezer with *'X' amout of fins radiating from it...

*'X' = depending on the amount of outlets/holes around the circle are feasable/needed...

[bigben2k]

I can help you with that, at least a good bit! PM me.

[dreamie]

Originally posted by MadDogMe
Do you mean to find 'cubic' area?...

Thanks!, another useful bit of knowledge ...

I'll be trying to find out how to 'equalise' flow over a radial block design soon by balancing the size of the holes around it, (cause the outlet will be off centre). I'll need some help with that I think, especialy designing the fin patern over the core. I was thinking of something that'd look abit like a lemon/orange juice squeezer with *'X' amout of fins radiating from it...

*'X' = depending on the amount of outlets/holes around the circle are feasable/needed...

yea.. i meant volume.. sorry if i misled u... typed it out wrongly!

[myv65]

Balancing flow can be a very tricky proposition. If you enter at a given location and eventually get back together at another location, then you have a defined pressure drop between those two points. This means that each of multiple paths will have the same pressure drop. The flow through each path is then a function of that pressure drop.

If the resistance of the paths is not uniform, then the flow will also vary. The variance may be minor (all within say 10%) or major (one of more branches with essentially no flow). Here's the rub: If the inherent resistance isn't pretty much the same, then usually the only way to equalize flow is to raise the resistance of all paths to match the highest resistance. Obviously this drops overall flow rate (and convection). Lowering all resistances to match the lowest or even modifying them to meet the "average" generally is not an option.

You may find that the inherent resistances are close enough to ignore their differences. If this isn't the case, things can get nasty in a hurry. This gets doubly-ugly (is that an acceptable term?) when you consider that you probably want to have a decent pressure drop at the entrance to get a good impingement velocity.

[MadDogMe]

As long as the path with highest resistance is'nt too high it should'nt impinge flow too much should'nt it?.I mean if the channel with highest resistance equalled the area of the inlet in the first place?. or have I got the wrong end?...

Imagine a circle/clockface with eight hours divided into four quadrants, the flow will enter the centre then divide into four(seperated) quadrants, at the outer part of each quadrant there are two 'holes' in a plate above, the flow will rise up through these to a chamber, the outlet will be at the 1/2 o'clock corner(almost straight above 1&2 o'clocks 'holes').
What I want is to balance the flow across the face of the circle by making the holes of different size(to stop it going straight out 1&2).
if I manage to balance the flow, will it stay balanced at different flow speeds?, I'd say yes but I'd like to know for sure ...

[myv65]

In answer to your final question, essentially "yes". Once flow is balanced, it will remain reasonably balanced through a range of flow rates. If flow drops to a fraction of original or quadruples, then things may get out of proportion.

The whole concept of flow resistance is not entirely intuitive. Resistance is not merely linear with flow area, for example. Geometries with equal area, but different shape (eg circle vs square) will have different flow qualities. Even for a given geometry (say circular) flow resistance is not linear with area.

[bigben2k]

Right on.

I used to have a web link, but lost it. I guess I'll just have to pick up Crane 410!

[MadDogMe]

How do you define flow resistance?, is it the total surface area of distance travelled?(in a straight in~out single channel), it get's more complicated if you consider the '1&2 o'clock' aspect of my design, the fact that more flow is using the 1&2 channel is creating resistance to the 5&6 channel is'nt it?, where they join that is,(as well as vice a versa!), it's a can of worms all right. good job I've got you guys ...

Resistance is not merely linear with flow area

PS, just took this in to answer my own question [Doh!] ...

It's anoying sometimes not being totaly conversant with people, specialy when you want to learn :shrug: , but I'll get there I hope , just bare with me(not Bear at me, [BillA!] )...

[g.l.amour]

thats why airspirit's statement in the dual rad parallel thread kinda sucks. all things are NOT equal between serial and parallel mounting of rads.

in my situ, mounting the rads parallel resulted in such a pressure drop that the air wasn't primed anymore, and mounting them serial the air was primed just ok. so myv65 you got my vote here, haven't forgotten the row between u and airspirit.

not to dis airspirit, his argument was valid, results would be better with parallel in very specific situations, and u will have some work to create that ideal situation: e.g.:

pump outlet, big diameter tubing + pump that can handle the 2 x load. goto a Y where u halve the diameter to each tube to +/- keep the pressure the same. let them come back together after the rads, and increase the tubing diameter again. there will prolly always be a flow difference between the two rads.

so if u want an easy no brainer , go serial dual rads. if u want some headaches and some try and error, go for parallel, doing it right should give u an added temp benifit. doing it quick and dirty will result to nothing.

so; lets get practical. lets say u need 1/2" discharge from pump to goto WB, then u split em into two 1/4" tubes going to each rad. u will have to make adapters to get em over the jumbo 3/4 barbs of your HC's... if u get serial u need only 1/2" tubing, no Y'z, and no adapters, so u choose.

[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 )...

[myv65]

I have no intention of rehashing the radiator debate that occured here a while back. The easiest answer is somewhat of a cop-out, and that's "test both ways and use the better". Just remember that slow flow = poor heat transfer. This statement is true in relation to water blocks, water in radiators, and air flowing over radiators. Spending more time in a radiator is generally not beneficial. The argument that ensued over parallel vs series did not center around water velocity but rather the relation of fluid to air delta-T through the radiator.

The article I'm presently working on (and have been dallying with for ~2 months off and on) covers blocks and radiators. When (no guarantees when) it gets finished, I'll try to have it all explained there.

[g.l.amour]

well, i certainly do'nt want to open old wounds. what i mean to say is that like u say, try both. but generally serial requires no special thought; parallel needs well thought out tubing diameters, more stress on pump, etc.

ohh, and about the upcoming article, warn us a couple of days in front, so i can make sure i get optimum night rest and food , so concentration can be at best. ;-)

[MadDogMe]

Spending more time in a radiator is generally not beneficial

I can understand why someone would have a hard time believing that!, but from what I know of your reputation it's no wildass claim , I look forward to your article, I'd like to see how it explains out.
I really don't have the £$% to buy two rads if I don't need them to test(and 1 big [OCPC Atlantis] is always cheaper than 2 small[OCPC Deep]), and if there's going to be no clear temp drop from using them then there's no point. can you point me to the thread?, I take it there's some info in there as well as the flaming? , or give me an outline of how you came to the conclusion?, what rads/pump you used as well?...

It seems to be another of those 'truths' that you read and take onboard everywhere has come home to rest does'nt it? ...

***************************************

ohh, and about the upcoming article, warn us a couple of days in front, so i can make sure i get optimum night rest and food , so concentration can be at best. ;-)

Usually takes me 20grms of sugar and three reads(plus! ) to take on board ...

[g.l.amour]

http://forums.procooling.com/vbb/sho...&threadid=4409

there u go.

as mentioned i like the serial rads alot. take 2 cheapass heatercores and an old maze style block and i'll beat anyone with some way too expensive design WB, and a tiny black ice rad. my take is a lazy one, as someone with higly optimised flow and rads + WB might do good too. give me a bigger case; 4 x rad surface; and with 1/10th of the testing time i will still have a rig i can almost passively cool without too much hassle.

[#Rotor]

your all wrong.....


it's: Pi*(d^2)/4




I'm Joking... ok....


to get the volume of a cylinder:

Pi*(d^2)/4*h


to get the surface area of same cylinder

( (2*(Pi*(d^2)/4)) + (Pi*d*h) )


where:

h = height of cylinder
Pi = Pi or you favorite numeral to the approximate equivalent thereof
d= diameter of cylinder

opperand significance: ^*/+- in that order


why only I work with diameter, and not radius...

well simple... try to measure the Radius of a round object, using a micrometer....

[MadDogMe]

whats the /4 bit mean in foolspeak? ...

[utabintarbo]

Originally posted by MadDogMe
whats the /4 bit mean in foolspeak? ...

divided by 4.

[Axly]

CIRCLE:
perimeter = 2 * pi * r
area = pi * r^2

CYLINDER:
volume = pi * r^2 * h (area of circle-part * height of cylinder)
could also use pi * d^2 * h / 4 (as said earlier)

area = 2 * pi * r^2 (circular ends) + 2 * pi * r * h (tube part)
or it could be written as: 2 * pi * (r^2 + (r * h))

SPHERE:
area = 4 * pi * r^2
volume = (4 * pi *r^3) /3