sp gr and pressure 1

[tomato5]

sp gr of a liquid is defined at a certain pressure and certain temperature e.g. 14.7 psia and 60 F.

does this mean at a large height, where the pressure might be 13 psia and the temp somehow maintained at 60 F, that the sp.gr. of the fluid will be different from that at 14.7 psia and 60 F. If at all so, will it be more or less?

Thank you

 

[zdas04]

Every fluid is different, but with water you need to change the pressure 319,000 psia to get a 1% change in density. No, a 1.7 psi change will not change specific gravity (defined as the density of a fluid at 60F divided by the density of pure water at 60F) a measurable amount.

Temperature is a different kettle of fish, but you asked about pressure.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[tomato5]

thank you clean answer conclusion also is that theoretically change of pressure would affect sp gr, but for a liquid it would be so minute that it would not matter in a calculation

 

[chicopee]

"but for a liquid it would be so minute that it would not matter in a calculation" I don't believe that it is true for every liquid; Research the bulk modulus of elasticity of liquids other than water.

 

[zdas04]

Dense-phase fluids act like a liquid and are compressible like a gas. Pressure is a significant component in their density (but fluids like CO2 use gas specific gravity calculations instead of liquid so their specific gravity in dense phase is not pressure or temperature dependent).

For fluids that are liquid at atmospheric pressure and ambient temperatures, I've looked at the bulk modulus for a bunch of them (when I was trying to find a hydraulic fluid for a pump that operated above 10,000 psig) and couldn't find any that were less than 100,000 psi. There are probably some, but I haven't come across them. At 100,000 psi to reduce volume 1%, 1.5 psi can be neglected.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[25362]

The following link gives tabulated values of isothermal compressibilities of liquids:

http://www.engineering.uiowa.edu/~cfd/pdfs/tables/1-42B.pdf

 

[racookpe1978]

Now, get out of the laboratory or pressure vessel-sized petro-chemical applications.

Pressure IS 1/3 of the three critical parts in the trio of pressure, temperature, AND salinity in determining the density of water in the oceans as it varies from a few feet down (near the surface) to 33,000 feet in the trenches, or from near-fresh water (right under the ice caps) down to the higher pressure and different salinity at the depths at the Arctic or Antarctic.

 

[goutam_freelance]

You mentioned height.

At large heights the gravity force will be reduced.

But I suppose you are not really considering great heights.