Gentelmen,
All those,who are graduated in chemical engineering are kindly asked to open
their old tekstbooks on "Heat,Momentum and Mass Transfer" ( 3rd,4th and 5th
semester in faculties of chemical engineering).Basic books used to be
McCabe-Smith and W.W.W. ( Whelty + 2 other with W ) .At least those were my
books more than 30 years ago.
Edward Szpruch
Eltek Ltd
P.O.Box 159 ; 49101 Petah Tikva Israel
Tel ++972 3 9395050 , Fax ++972 3 9309581
e-mail [log in to unmask]
> -----Original Message-----
> From: Rummy Makmur [SMTP:[log in to unmask]]
> Sent: ג נובמבר 13 2001 14:12
> To: [log in to unmask]
> Subject: Re: [TN] Formula?
>
> To prove that, you need combination of mass balance and mechanical energy
> balance (i.e. bernoulli equation).
>
> mass balance: mass rate in = mass rate out. Assuming incompressible fluid
> (same density in and out), since mass rate = volume rate * density,
> density
> get canceled out and the result is volume rate in = volume rate out. It is
> also known that volume rate = velocity * Area. From this you can prove
> that,
> if area is decreased (such as, putting your thumb on the hose), velocity
> will increase.
>
> Then you will need bernouli equation. Simplified Bernoulli Equation:
> (P1/density) + (Velocity1^2/2)+ (gh1) = (P2/density) + (velocity2 ^ 2/ 2)
> +
> (gh2)
>
> Assuming h (height) is the same, they get canceled out. Then, you will
> have
> an equation with only P (Pressure) and V (velocity) as variables which you
> can use to prove that if V2 increases, P2 decreases, provided P1 and V1
> are
> constant.
>
> So, volume rate at location 2 is not dependent on Pressure at location 2,
> provided same pressure and volume rate coming in. It "feels" like pressure
> increasing, but rather it's velocity that is increasing or kinetic energy
> increases.
>
> Check out these sites
> http://physics.bu.edu/py105/notes/Bernoulli.html
> http://rabi.phys.virginia.edu/HTW/water_distribution.html
>
> For the second question, you might not be able to use same exact equations
> for air, since air might be considered as compressible. It may involve
> more
> complicated equations.
>
> Rummy Makmur
> Process Engineer
> Ibiden Circuits of America
>
> -----Original Message-----
> From: Eric Christison [mailto:[log in to unmask]]
> Sent: Tuesday, November 13, 2001 3:27 AM
> To: [log in to unmask]
> Subject: Re: [TN] Formula?
>
>
> I think you're all barking up the wrong tree.
>
> Bernoulli's equations shows the conservation of kinetic energy in fluids
> and is generally used to calculate things like areodynamic lift on an
> aerofoil or the forces exerted on a pipe wall as the the contents flows
> round a corner.
>
> I think you're searching for P1v1/T1 = P2v2/T2. However v is not volume
> but specific volume ie m^3/Kg.
>
> Spend a minute on a reality check. If you put your thumb on the end of a
> hose pipe does the pipe get smaller? If not, how can the volume of the
> pipe decrease?
>
> Hope this helps,
>
>
>
> [log in to unmask] wrote:
> >
> > Ray, try http://www.lmnoeng.com/Flow/bernoulli.htm
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]]On Behalf Of Golembiewski, Ray
> > Sent: Monday, November 12, 2001 14:34
> > To: [log in to unmask]
> > Subject: [TN] Formula?
> >
> > What is the formula that proves when I put my thumb on the end
> > of a garden house, the pressure increases and volume decreases. Is the
> > same formula used with air? Please help,
> >
> > Ray Golembiewski C.I.D.
> > Manufacturing Test Engineer
> > Projects Unlimited, Inc.
> > (937) 918-2200
> >
> --
> Eric Christison
> Mechanical Engineer
> STMicroelectronics
> 33 Pinkhill
> Edinburgh
> EH12 7BF
>
> Tel: (0)131 336 6165
> Fax: (0)131 336 6001
>
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