Sonic Velocity 1

[stech2006]

Please help...I am new at everything.
I just had someone ask me to find the Sonic Velocity.

I have no idea what to do.

This is the information that I was given...

Hydrogen
1050# Pressure
Ambient
Hole 3/16

I got the Molecular weight through a website 2.02

I am lost and new at this job. If anyone can help me I would appreciate it or guide me in the right direction.

Thank you.

 

[sreid]

Here's my input. If the pressure is 1050 PSI, I'm certain that the flow through a 3/16 inch hole would be sonically limited so the velocity would be 1270 m/s.

http://dictionary.laborlawtalk.com/Hydrogen

 

[Montemayor]

And yet - another Sonic velocity thread (a.k.a. Choked Flow thread).

You can't have any velocity without establishing a pressure drop - otherwise known as the driving force. As per Crane Tech Paper #410, the maximum possible velocity in a pipe is sonic velocity which is:

V_s = (k * g * R * T)^0.5
where,
k = the ratio of specific heats;
g = acceleration of gravity, 32.2 ft/sec²;
R = the individual gas constant;
T = the absolute temperature, ^oR

You can find out more information than you ever wanted to know about the subject by using the Search feature and looking for the Choked Flow thread in these forums.

 

[sailoday28]

Montemayor (Chemical)
Velocity in a pipe can exceed sound speed. M>1 can occur in a piping system. Will it subsist? Well, not if the flow goes through a shock.
Limiting flow with the FANNO LINE is M=1. If upstream M>1, then M decreases toward M=1 in flow direction. If upstream M<1, then M increase to M=1 in flow direction.

Regards

 

[Latexman]

stech2006,

I applaud you for having the iniative and guts to ask for help when you needed it. I suspect you'll do just fine in your new job if you keep it up. It will not take you long to realize that university did not teach you nearly enough for a real world job. You always have to be learning, reading pertinent journals, buying the references the gray beards say are worth their weight in gold. Learn to use Google! Google is your friend! Check out the used book sites for the references you need, like Powells, Addall, Amazon, and Alibris. Find a mentor or co-engineer to bounce things off of. Two heads are better than one. Last, but not least, keep a journal of all you do AND keep a copy or originals of ALL your calculations. You'll be amazed how often you'll do some things. And on those repeat calcs, automate them with an Excel spreadsheet or something.

Good luck,
Latexman

 

[zdas04]

stech2006,
To reinforce Latexman's good advice, I started a MathCad worksheet in version 4 (they're now on version 13, so it has been a while) that has grown to 12 MB through the years. I put every equation that I have ever had to look up into it, with explainations of the terms, limiting assumptions, and references to where I found the equations. When MathCad started allowing collapsable areas, I put in headings and collapsed the equations (just the headings is 10 pages long).

I have this file backed up in my fire safe once a month. It would be easier to replace my business financial records than this journal. The earlier you start, the sooner it will be useful.

David

 

[ThetaJC]

I agree... Spreadsheets are a great way to wrap your head around a problem.

ThetaJC
Proud member of

http://www.engspreadsheets.com!

 

[magicme]

as others have well advised..... start your own library of spreadsheets or MATHCAD or MATLAB or C++ or whatever you like to use. put every common calculation you run across into that format and update it as the years go by.
keep the folder and file names logical so stuff is easy to find (not like me with stuff scattered about 4 computers !!! )

AND DO BACKUPS

regards

magicme

------------------------------------
"not all that glitters is gold"

 

[davefitz]

soundpspeed is dependent on the temperature of the gas, yet you have not yet defined that.

 

[ThetaJC]

I think it was inherent in the word "Ambient"; approximately 68°F would be my guess as I believe he was implying standard temperature conditions.

ThetaJC
Proud member of

http://www.engspreadsheets.com!

 

[sailoday28]

davefitz (Mechanical)
Sound speed is dependent only upon temperature-if one is dealing with a perfect gas.
Regards

 

[davefitz]

It is not a matter of "only with a perfect gas"- for all gases, at all times, the soundpseed is a function of temperature; as I recall, soundpseed is representative of the mean molecular velocity passing in one direction, which is something like c= 2/3 SQRT(kT/M) . The temperature is likewise representative of the mean velocity of the molecules, so in some ways temperature and soundpseed are interchangeable.

 

[sailoday28]

davefitz
Sound speed^2=dp/drho under isentropic conditions.
For other than a perfect gas, sound speed is dependent on two independent variables, such as Pressure and Temp.

For simplicity try it with a VanderWall gas.

Regards

 

[davefitz]

right. For all gases, there is an equation of state. dP/dRho | s can be shown to be directly related to T, for all gases. More to the point, the soundspeed represtents the avg spped of all gas molecules in one direction, and that is directly associated with the gas temperature, for all gases, at all times, in every nomral case ( excepting stratified or ionized gases).