Physics question very unrelated to diving

[dlwalke]

Anyone know a formula by which you can derive the number of atmospheres pressure (g-forces) generated by centrifugal force given rotational velocity and the radius (or diameter or circumference) of the circle being traversed. I am becoming addicted to espresso and am contemplating (during my caffeine-induced manic states) a new less expensive way of making espresso. Apparently, stovetop "Moka"-style pots generate no more than 3 atm pressure which is quite sub-optimal for true espresso. To better fit this into a diving forum.....there is nothing I enjoy after diving more than espresso, but can't bring a machine on the boat. Am thinking about swinging some beans in a can on a string from the poop deck. OK, the last part's not for real....but I AM wondering about the equation. Thanks.

Dave

 

[scubasean]

F = (m[v^2])/r

Centrifugal force = mass times the square of the velocity, divided by the radius....

Is that what you wanted? The result is not in atmospheres...Atmosphere is a pressure term, not a force term.

If you use meters per second, grams, and
meters, your answer will be in Newtons...

 

[Big-t-2538]

Well, scubasean is half way there....

Once you have force...pressure is easy...

Pressure = Force / applied area......or P = F/A

So take the area of the bottom of the can you are swingin your beans around in....and divide that into the force.

Using Newtons for force....you'll end up with Pascals for pressure, but you can convert that to ATMs using any on-line converter (since I don't know the conversion off the top of my head)

 

[dlwalke]

Thanks guys. I'll cut you in for a piece of the first months profit from the new Espresstrifugal 2000.

Dave

 

[cornfed]

I have this strange feeling something about compressable fluids is being overlooked.

Just remember, it at first it doesn't work just swing faster!

Cornfed

 

[Big-t-2538]

cornfed once bubbled...
I have this strange feeling something about compressable fluids is being overlooked.

Just remember, it at first it doesn't work just swing faster!

Cornfed

I agree...but I think the compression has to do with the beans.....alright...this is a long way away from beer.

 

[cornfed]

Big-t-2538 once bubbled...


I agree...but I think the compression has to do with the beans

I think you compress the steam then force it through the ground coffee.

.....alright...this is a long way away from beer.

Are you a homebrewer?

 

[dlwalke]

I think you compress the steam then force it through the ground coffee.

Well...on a stovetop espresso maker, I think the water heats up and starts steaming. The expanding gas then forces the water up through a tube at high pressure through some very finely ground coffee beans. The water collects in a resovoir.

I have this strange feeling something about compressable fluids is being overlooked.

The fluid is really compressed. Its being forced at high pressure through a compartment that contains ground beans. So it would be kind of like a 3-compartment chamber. A chamber where you would pour 8 oz or so of just boiled water, a middle chamber containing the grounds with perforations on both sides of the chamber to allow water to pass, and the third compartment to which the water would flow at a pressure (don't recall if this is the right word or not vis-a-vis force v pressure) produced by centrigugal force. Thants the idea anyway...am not entirely sure that it makes sense, but right now it does to me.

Dave

 

[Big-t-2538]

dlwalke once bubbled...


The fluid is really compressed. Its being forced at high pressure through a compartment that contains ground beans. So it would be kind of like a 3-compartment chamber. A chamber where you would pour 8 oz or so of just boiled water, a middle chamber containing the grounds with perforations on both sides of the chamber to allow water to pass, and the third compartment to which the water would flow at a pressure (don't recall if this is the right word or not vis-a-vis force v pressure) produced by centrigugal force. Thants the idea anyway...am not entirely sure that it makes sense, but right now it does to me.

Dave

O.K...reverting to geek stage here....in it's pur liquid form, water is not compressible, the stage you speak of for water is the vapor stage where it can be compressed...it is like compressed steam in old steam turbine engines.....oh wait, those aren't old are they?

And no, unfortunately, I am not a home brewer, I just don;t have the time for it, or I'd love to try a batch. I'd start with something simple like a pale lager and go from there though. No sense in trying to make a dark beer off the bat if you can;t get the easyt stuff done first.

Alright...back to diving

 

[cornfed]

And no, unfortunately, I am not a home brewer, I just don;t have the time for it, or I'd love to try a batch. I'd start with something simple like a pale lager and go from there though. No sense in trying to make a dark beer off the bat if you can;t get the easyt stuff done first.

Actually a dark ale is much easier then a lager. First, the darker, roaster malt flavors help mask any small problems. Second, lagers require cold fermentation and storage (40s vs mid 60s for ales) so the equipment and logistics are more complicated.

Alright...back to diving

Fine...

Cornfed