Fluid Mechanics Help Please

[Acasta]

Actually this is the correct formula no matter what size pipe you use the problem is accounting for the pressure loss. For this problem the pressure loss in question is going to be the frictional loss in the pipe. In a 6mm ID pipe I would imagine there will be some fairly large pressure loss particularly over 16m.

Having said that you can't make the assumption that the flow rate of the open tap will be the same as that once 16m of 6mm ID pipe is attached to it. The increase in static pressure from the pipe will reduce the flow rate.

Yeah i know, the formula is correct, but on this scale its not really relevant. Your right, the friction in the pipe would be the main flow changer. And also the pressure at tap i have no idea how to get tap pressure, just taking a quick stab.

 

[MHB]

It would work just fine

You are going to get plenty of water through it, from experience the dynamic pressure drop will be between 150 and 180 kPa and the flow rate will be more than adequate. We pulled the coil out of an old Temprite to use as an immersion chiller worked well; it eventually got reconfigured into a HERMS coil.

As for stainless being a crap conductor well yes it is for a metal but it's still pretty dam good compared to glass. Glass lab equipment is used for boiling and condensing liquids and gases on a daily basis. I would bet that a fair number of the people that tell you Stainless won't work as a chiller are boiling the wort in a Stainless pot with ought a second thought.

At around $150 it isn't the cheapest way to do it but if you don't want to add copper to your wort or you just plain like the look of the stainless coil go for it looks dam sexy.

MHB

 

[katzke]

What was the question again?

Easy answer is email them and ask what the specks are for balancing a tap system. The coil will effect how the beer pours so they should know. If that does not work I remember finding information on balancing taps that had a factor for different size and type of tubing. It worked backwards so if you know what flow out you want and how long of what type of tubing then you can find out what the tank pressure has to be for the beer.

I would not worry about how it will effect the flow of tap water. I use a copper chiller and always turn the tap down to slow the water flow. I have found that there is a sweet spot where the chiller works best and it is not full open. Full open also gives a lot of head pressure and almost always blows the tubing off the connection I have. It uses much more water and does not speed up the process any. I think it may actually slow it down. I am not sure if it is just a time calculation or the way the water flows when you increase the flow past optimal for the size of tubing.

Now a counter flow chiller is a different thing. Part of the difference is the hot wort is moving as well as the cold water. They can actually chill the wort down too much depending on the temperature and flow rate of the source water as well as the wort. A properly designed counter flow chiller also is designed so both liquids move in such a way to ensure complete and multiple contact with the metal thus increasing the efficiency of the unit.

 

[katzke]

Last thought, the tubing you use may have a different flow then the one they use. It all has to do with how smooth the inside is. How well you coil it and what fittings you use will also have an effect. Dont forget the supply tubing to hook it to the water as well as the exit tubing to get rid of all the warm water.

So you question about 1 calculation has turned into at least 5 calculations.

 

[egolds77]

Flow in pipe is always creating energy loss due to friction. Energy loss can be measured like static pressure drop in the direction of fluid flow with two gauges. General equation for pressure drop, known as Darcy's formula expressed in meters of fluid is:

where is:

h_L - head loss due to friction in the pipe
f - friction coefficient
L - pipe length
v - velocity
D - internal pipe diameter
g - acceleration of gravity


To express this equation like pressure drop in newtons per square meter (Pascals) substitution of proper units leads to:

where is:

&Delta p - pressure drop due to friction in the pipe
&rho - density
f - friction coefficient
L - pipe length
v - velocity
D - internal pipe diameter
Q - volumetric flow rate


The Darcy equation can be used for both laminar and turbulent flow regime and for any liquid in a pipe. With some restrictions, Darcy equation can be used for gases and vapors. Darcy formula applies when pipe diameter and fluid density is constant and the pipe is relatively straight

 

[unrealeous]

So plug some numbers in Einstein and see what you come up with for a flow rate.

26 meter head pressure
6 mm stainless tube (you can get the roughness vals from this)
16 meters length

 

[egolds77]

What is the diameter of the pipe that the water from the tap is leaving from? You need this as a starting point to determine the difference in flow from the two pipe diameters and the coil pipe length.

 

[unrealeous]

What is the diameter of the pipe that the water from the tap is leaving from? You need this as a starting point to determine the difference in flow from the two pipe diameters and the coil pipe length.

You can assume anything you like - we are guessing the head pressure so say 16mm id which is roughly the id for a 3/4" copper water pipe. But I think this is the wrong way to look at the problem since the stainless tube is a lot smaller than the feed pipe - so its really a question of pressure.

ie: Its the same as asking what flow rate would you get if you stuck the tube into a dam wall 26 meters below the water line (ie constant head pressure).

 

[schooey]

Watching this thread is like watching a bunch of lawyers design a better cow...

Not being a smart ass, OP, but you're asking for a reasonably complicated answer but only supplying half assed information; hence all the guessing and over-complication in the replies...

Short answer is if you can't prvide the information required for the correct answer to be theoretically calculated, go adapt a hose fitting on your coil and turn the tap on and see how many minutes it takes to fill a 5 litre bucket or 30 litre fermenter... bingo!


My gut feeling says somewhere around 8-10 L/min, but like a few other replies here, that's a guess I just pulled outta my arse....

 

[egolds77]

Thank you Schooey . . .

 

[donburke]

Not being a smart ass, OP, but you're asking for a reasonably complicated answer but only supplying half assed information; hence all the guessing and over-complication in the replies...

whats half assed about my information ?

all data was provided, incoming flow rate through a normal household tap, a coil of a given material, length and diameter

what more could i possibly provide, the coloured shirt i'll be wearing when using it ?

thanks everyone for your replies, i've ordered 2 of them, i'll join them together and see what happens,

if the flow is like someone with a prostate problem, i'll donate them to the zoo so the elephants can use them as cockrings

 

[schooey]

Like I said, Don, I wasn't trying to be offensive... But what is 'normal' at a household in your part of the world may not be in normal in others... Pressure at a tap can vary wildly, you didn't state what fittings, if any would be in the system, is the stainless cold drawn annealed seamless or non annealed (this will affect the internal smoothness, therefore friction losses), you said 'about' 20 L/min; is it 19 or 21? All these things and more play s part in an accurate answer...

Anyway, good luck with it...I'm pretty sure they'll serve you well and the elephants will be safe from your kinky antics...

 

[donburke]

Anyway, good luck with it...I'm pretty sure they'll serve you well and the elephants will be safe from your kinky antics...

lol,

point taken

 

[michael_aussie]

Watching this thread is like watching a bunch of lawyers design a better cow...

Not being a smart ass, OP, but you're asking for a reasonably complicated answer but only supplying half assed information; hence all the guessing and over-complication in the replies...

Short answer is if you can't prvide the information required for the correct answer to be theoretically calculated, go adapt a hose fitting on your coil and turn the tap on and see how many minutes it takes to fill a 5 litre bucket or 30 litre fermenter... bingo!


My gut feeling says somewhere around 8-10 L/min, but like a few other replies here, that's a guess I just pulled outta my arse....

the only sane advice given i think.

An interesting thread .... a bit of thermo .. a bit of fluid mechanics .... a bit a shit stirring ... a bit of chest puffing .......
and a bit of perversion (elephant cock rings)......

exact the reason why I keep coming back to this site.

 

[Nodrog]

OK, no high fallunging fluid mechanics, but a rough rule of thumb:

count on a velocity of 2 metres per second going full chat. You might get 3, and probably 1 is reasonable with the tap partly open.

So 6mm (ID ??) tube has a cross section area of 3*3*3.14 mm2 = 28.3mm2.
1 m per second velocity = 0.000028 m3 per second
or
0.0017 m3 per minute
1.7 litres per minute
Not alot

You'd easily double that, maybe triple, I doubt you'd get 10x that.

From what i recall, any liquid flowing faster than 3m per second is some serious speed, back pressure becomes too much, and it just doesn't happen without monster pressures..

Would be interested to hear what you get in practise.

 

[donburke]

my 2 coils arrived today, as soon as i got home i made a bodgie join of the two coils in series,

and another bodgie coupling to the garden hose, all consisting of some gaffa tape

well it leaked, and i got squirted a fair bit,

even with these leaks i managed a flow rate of 4 litres a minute through 32 metres of 6mm id coil

now the next question is, will it improve flow rate if i connect the coils in parallel ?

 

[Bongchitis]

G'Day Don,

Theoretically yes the total pressure drop across parallel vs series will be less thus the flowrate will be slightly higher, all other things being equal.

... but, fittings that disrupt the flow yield a pressure drop, as schooey has already stated, and unless you had lovely smooth 'y' pieces for the parallel setup, any benefit will be squandered I reckon.

I really don't think that we are dealing with pressures/flowrates/run lengths etc that would give us anything tangible with respect to benefits but let us know how you go. If you want process improvement, i'de say focus on long sweeping directional changes for fittings and smooth walled tube but you probably don't have much control over these.

The above is only for flowrate aswell, who knows if the parallel or series setup would be better for total heat transfer, for which i am assuming you are using the coils for.

I too think some more info would be good.

 

[MHB]

my 2 coils arrived today, as soon as i got home i made a bodgie join of the two coils in series,

and another bodgie coupling to the garden hose, all consisting of some gaffa tape

well it leaked, and i got squirted a fair bit,

even with these leaks i managed a flow rate of 4 litres a minute through 32 metres of 6mm id coil

now the next question is, will it improve flow rate if i connect the coils in parallel ?

Being a (very X) plumber by trade, I'm not qualified to answer that question, so I'm going to leave it alone.

If you want to connect something as small and "slippery" as " SS to the mains you are going to want to solder a threaded connector onto the ends, or use a flair nut, both options require that you know what you're doing and have the right tools, lacking those, consult an expert

Oh Hang it yes of course you will get a higher flow rate if you connect them in parallel, provided you don't reduce the mains connection too much before splitting, the flow rate won't be double or anything like it maybe 5-6 L/m at best guess.

If you use 1 coil as a pre-chiller in a bucket of ice slurry your 4L/m will be heaps and I think you will be surprised at how fast it cools the wort.

MHB

 

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[speedie]

test 002 has sneeked through the firewall

and mhb stainless is a good alternative to copper
but some copper in the brew process is always good for the beer
cheers speedster