Chemisty Question

[Valving]

Sorry for this question, but I am confused and need a clear advice
I need to calculate specific weight of some fluids and I have
following parameters of them,
SG / Mol Wt
Viscosity
Vapor Pressure @ Op. T
and flow rates.

Could I reach the SW with these data? Pls. advice

 

[25362]

May be this site may clarify matters:

http://en.wikipedia.org/wiki/Specific_weight

 

[Valving]

I already did but I am trying to calculate it for fluid and it does not work. if you could understand the direct relation, pls. advice kindly.

 

[zdas04]

Specific gravity is [ρ]_liquid/[ρ]_water. Specific Weight is 1/[ρ]_liquid. If you know SG then you know SW if you have the wherewithal to look up the density of water.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[Valving]

Thanks David, but if 1/ SG does not give molecular weight? or I am totally lost?

 

[Latexman]

You are so very lost.

Good luck,
Latexman

 

[Latexman]

Density = mass/volume.

Specific weight = weight/volume.

Weight = mass x g/g_c.

Therefore, specific weight = density x g/g_c.

For example, density of water = 62.4 lb_m/ft³.

62.4 lb_m/ft³ x 1 lb_f/lb_m = 62.4 lb_f/ft³ and specific weight of water = 62.4 lb_f/ft³.


Good luck,
Latexman

 

[zdas04]

OK, I described Specific Volume.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[Valving]

Latexman thanks but I am trying to calculate if possible SW from SG, is it possible?
This is a combination of steam, CO and water (geothermal brine)
Parameters I have is
SG / Mol Wt
Viscosity
Vapor Pressure @ Op. T
and flow rates.
could I calculate SW of the brine?

 

[TD2K]

As David and Latexman have said, SG is the ratio of the density of a fluid at some temperature to that of water at a reference temperature.

The density of water is usually around 62.4 lb/ft3 or 8.34 lb/gal depending what temperature you use. The density doesn't shift a lot with 'small' temperature changes but there are times where that can be a factor, say for custody transfer of fluids.

So, if the brine has an SG of 1.2, its density is 1.2*62.4 = 74.9 lb/ft3. That SG can be at temperature (which for geothermal can be pretty hot) or it can be at the same reference temperature as the water reference, you need to understand what you have and it's not something we can likely tell you what you have. Back the density, the specific volume is the reciprocal of that (1/density) or 0.01335 ft3/lb in this case.

Just to confuse things more, SG can also be used to describe the ratio of the MW of a gas to that of air. CO has a MW of about 28, air is 28.96 so the SG for CO would be 0.967. For H2 with a MW of 2.016, the SG is 0.0696.

I'm not sure what data you have to answer your question specifically.

 

[MatthewL]

Valving,

Your first known, is it specific gravity DIVIDED by molecular weight? If so, you have to back calculate specific gravity using the molecular weight, then specific weight is specific gravity times density of water times g/gc. In english units, it would be SG * 62.4 lbm/ft3 * (32 ft/s2) / (32 lbm *ft/(s2 * lbf)) , but in SI units, it is SG * 1000 kg/m3 * (9.8 m/s2) / (1 kg * m / (s2 * N)). Remember, mass is lbm or kg while weight is lbf or N!

NB: Specific gravity is dimensionless, since it is the ratio of two densities ,specifically, the density of a substance divided by the density of water, usually at 4 C, where the density of water is 1.00 g / cm3.

Matt

Quality, quantity, cost. Pick two.

 

[Latexman]

Maybe this will help you:

SG

Good luck,
Latexman

 

[25362]

Density and specific gravity were well defined above.
Specific Weight (SW) -as Latexman said- is defined as weight per unit volume. Weight is a force. SW can be expressed as

[γ] = ρ•g​

Where:
[γ] = specific weight (N/m³)
ρ = density (kg/m³)
g = acceleration of gravity (m/s²)

The SI-units of SW are N/m³. The local acceleration g under normal conditions is taken as 9.807 (~ 9,81) m/s² in SI-units.

Example - SW of Water

SW for water at 4^oC is 9.81 kN/m³. SW, in SI units, can be expressed:

γ = (1000 kg/m³) (9.81 m/s²)
= 9810 N/m³
= 9.81 kN/m³