alright when trying to find the velocity, i'm getting like 15.35....i have sqrt((2*8.14684 lb/ft2)/(.0719 lbm/ft3)). What conversion factor am i missing necessary to get ft/s? My density is .0719 lbm/ft3 and my delta p is 1.566 in H20. When i convert the in H20 to lbf/ft2 i get 8.1374 lb/ft2.

2/20/2006 2:36:14 PM

for velocity, u need to use rho in slug/ft^3. then when u plug that into ur velocity equation, u will have sqrt(lbf*ft/slug). remember that a slug is a lbf*s^2/ft. it all works out once u do the conversions.

2/20/2006 2:50:44 PM

or you can leave rho in lbm/ft^3 and convert your delta P from lbf/ft^2 to lbm/ft-s^2

2/20/2006 2:53:27 PM

when i calculate the integral im getting 13.1

then after multiplying by 2*pi*rho i end up with a mass flow rate of 6.04

anyone else getting something like this??

^^how did you plot your Vr vs. r graph. Vr. is in ft^2/s and r is in inches.

then when calculating the area under the curve you go from 0 to 2 inches. does any of that make a difference? it seems like it would.

[Edited on February 20, 2006 at 3:43 PM. Reason : .]

2/20/2006 3:19:12 PM

where the hell is table A-6? lol

2/20/2006 7:54:53 PM

r has to be converted to feet. NEVER use inches, ALWAYS feet when dealing with english units..words right from Dr. Tran's mouth from 415 class bitching about people who never use feet. the radius has to be converted to feet then to get a realistic number since everythin else is in feet. same with the graph. plot r (ft) on x axis and Vr (ft^2/s) on y axis. and ur not supposed to use 2 (due to the 0's and N/A), use the next radius after 2 on ur data sheets.

table A-6 is using the Fluid Mechanics book.

[Edited on February 20, 2006 at 8:00 PM. Reason : .]

2/20/2006 7:59:10 PM

ah shit, i don't have that book. can someone be a sport and look up the viscosity for air at 23 celsius, please?

nvm

[Edited on February 20, 2006 at 8:38 PM. Reason : used intarnet]

2/20/2006 8:10:00 PM

Ah, thanks for mentioning not using 2 in the graphs. Need to adjust mine now.

2/20/2006 9:10:05 PM

Im in lab section 207, wed 130-315.
I only have 11 values written down for the lastest lab,can anybody help me out and post I guess all 12 that we are suppose to have.thanks

2/21/2006 7:27:29 PM

^ there are only 11 values in our section
10 from 0" to 1.9335", and then the 2"

2/21/2006 9:50:49 PM

^^ yeah I'm in that same section

only use the data points we have, I'm pretty sure we don't need more

2/21/2006 10:13:57 PM

yo nerdchick, do you know what the dynamic viscosity is for our temp of 22.1 degrees c????

2/21/2006 10:26:49 PM

my friend's TA told them 0.0433 lbm/(hr-ft)

and their room temperature was similar so I used that for mu

2/21/2006 10:49:01 PM

okay quick question

wtf is Vr supposed to represent, like in words. I can't just call it Vr for the entire lab writeup

2/22/2006 12:24:14 AM

^ I did.

2/22/2006 12:33:47 AM

anyone have a room temp for this past week's lab? i know it's not important for calculations but i need to include it for the observed data.

2/26/2006 5:47:56 PM

23 degrees C

2/26/2006 7:03:08 PM

how do we find density of the oils at different temperatures for the sae 10w and sae 40w. Or do we even need those values?

2/26/2006 10:41:17 PM

find density of water at each temperature and then use specific gravity to find density of oil at each temperature.

2/26/2006 10:43:42 PM

so SG is constant?

2/26/2006 10:49:19 PM

density of water changes with temperature?

2/26/2006 10:49:20 PM

Is the suv chart seconds the time to fill a 60ml flask?

2/26/2006 10:50:58 PM

SG is constant for each specific oil

yes water density changes with changes in temperature. the change isnt large, but still does change.
http://antoine.frostburg.edu/chem/senese/101/measurement/faq/water-density.shtml

i believe it's for 60ml

[Edited on February 26, 2006 at 11:00 PM. Reason : .]

2/26/2006 10:59:28 PM

for the pump analysis lab, which is the input power? the fluid horsepower or brake horsepower?

3/7/2006 2:46:27 PM

^bhp,
what are the numbers you guys are getting, im gettin really low HP, like 0.3HP to 0.15HP.
for Pfluid its eeven lower, like 0.0123HP. i must be doing something wrong. my Q is converted from gpm to ft^3/sec, psi to lbf/ft^2 for Pfluid and for bhp, rpm converted to ft/sec and T converted to lbf-ft. and then those numbers multiply by 1/550 to get HP.
this thus caused my coefficients to be really low too.

3/7/2006 10:07:28 PM

i get really low numbers as well for my input and output powers

3/7/2006 10:37:43 PM

I am getting small numbers for the power values as well. For example, at 1200 RPM for 1.5 gpm, I have bhp = 0.0762 HP and P_fluid = 0.00351 HP.

3/8/2006 12:03:07 AM

head rise.....isnt it supposed to be in ftH20?

why do you divide by density*grav for this....doesnt seem to make sense.

3/12/2006 3:53:54 PM

check ur units..ur dealin with lbm and lbf

3/12/2006 3:55:11 PM

deltap is in ftH2O, and density*gravity comes out to be lb/(ft2s2)

but head rise is supposed to be in ftH2O, how does pg cancel itself out?

3/12/2006 4:13:26 PM

deltap (a pressure) has to be in lbf/ft^2.

3/12/2006 4:14:38 PM

is 1lbf = 1lbft/s2 ?

3/12/2006 4:30:11 PM

1 lbf = 32.2 lbm*ft/s^2

1 lbf = 1 slug*ft/s^2

3/12/2006 4:35:43 PM

nevermind

[Edited on March 12, 2006 at 8:07 PM. Reason : nm]

3/12/2006 8:06:10 PM

I'm still not getting this head rise thing, i cant see any way to manipulate a pressure devided by density and gravity that leaves you with only pressure.

[Edited on March 13, 2006 at 1:42 AM. Reason : .]

3/13/2006 1:41:42 AM

I asked my TA. The units of head rise and the units of
pressure are not the same. A foot of water head rise is not the same as a
foot of water of pressure.

3/13/2006 10:43:52 AM

when we calculated the inlet and outlet pressures in lab, what were the units then.......were they both in h20 or was the outlet pressure in psi?

3/13/2006 12:19:24 PM

Quote :

"I asked my TA. The units of head rise and the units of pressure are not the same. A foot of water head rise is not the same as a foot of water of pressure."

no offence but u had to ask the TA that? foot of water pressure needs to be converted to lbf/ft^2 so that units will cancel properly in conjunction with density and gravity. have u guys not had 308 yet?

3/13/2006 12:49:36 PM

What should I get for my head rise at 1200 rpm at a flow rate of 1.5 gpm?

3/13/2006 1:17:17 PM

for the head rise if you use lbf for both pressure and density you dont get the correct units

someone who knows how to get ft H2O please lay it out real nice like

[Edited on March 13, 2006 at 3:25 PM. Reason : .]

3/13/2006 3:05:18 PM

i dont know how else to explain this.

3/13/2006 3:53:00 PM

when I calculate H, it comes out to be the same as deltap because the p*g cancels out with my conversions, is it supposed to be like that?




also I am getting an efficiency of 20% or so, is anybody getting the same thing?

thanks for the help so far

3/13/2006 8:12:46 PM

What the heck are the units supposed to be for calculating the capacity, head, and power coefficients? I can't find a way to make them cancel out. I've tried several different things and can't get an efficiency value anywhere close to the one calculated the other way.

3/13/2006 8:14:56 PM

i'm having trouble determining how to get variable n, the pump speed, into rad/s. i used the equation dr. tran gave:

Pin = [2(pie)/33000]*T*n

is the coeficient suppose to be the conversion factor?

i just need how to use n to get the coefficient equations. any help, please?

[Edited on March 13, 2006 at 8:23 PM. Reason : .]

3/13/2006 8:17:02 PM

^ I'm not really sure what you're asking

you need to convert n from rpm to rad/s, our TA told us that 1 rad/s = 9.549 rpm

you have to convert T into lbf-ft, multiplying by n gives you (lbf-ft)/s, which you can convert into HP using 1/550

^^ I've only done Cq so far, but for that one you convert gal/min to in3/s, and rpm into rad/s, and D is inches, so it all cancels out

3/13/2006 8:27:01 PM

yeah, i just need the conversion factor. thanks.

3/13/2006 8:35:56 PM

nerdchick, where did u get ur conversion factor numbers from for ur pressures?

capacity coefficients, head coefficients, power coefficients are unitless. units MUST cancel out entirely

n is just the speed of the motor being converted from rpms to rad/s. for 1200rpm:
1200rev/min*1min/60sec*2PIrad/1rev

EVERYTHING MUST ALWAYS BE IN TERMS OF FEET, NEVER INCHES!!

[Edited on March 13, 2006 at 8:40 PM. Reason : .]

3/13/2006 8:39:52 PM

I got all my pressure conversions online, our TA didn't give them to us

the conversion from psi to ftH2O, and from ftH2O to lbf/ft2 are the only ones I used for those, are they wrong?

3/13/2006 8:45:17 PM

use these conversions. they are a shit load easier to do and understand.

3/13/2006 8:56:42 PM

Our TA gave this conversion for in. H2O: 1 in H2O = PSI * 27.684

[Edited on March 13, 2006 at 10:38 PM. Reason : also, 1 rad/s = 9.549 RPM]

3/13/2006 10:37:11 PM