this post was submitted on 22 Feb 2025
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Maybe a weird aside, but what does this mean?
Are there "liters" other than the 10cm x 10cm x 10cm definition?
To totally confuse you: The USA uses the "standard litre" while Europe uses "normal litre":
https://en.wikipedia.org/wiki/Standard_litre_per_minute
Thanks, you succeeded hahaha.
From what I'm reading there this is a measure of mass flow rate of gas, expressed as volume per minute at some standard volume and pressure. Which makes some sense, you need those two parameters to be fixed so you can measure mass by volume.
And then I realized the OP article uses it for a ~~fluid~~ liquid 😂
Aren't fluids and gases kinda the same thing in some aspects, just different mass? (Clearly, not a scientist).
The major difference is compressibility. Generally, liquids are practically incompressible. So just knowing the mass flow rate and density, volume flow rate can be calculated. It's not so simple for gases
First of all: Sorry, I made a mistake yesterday. I ment to say liquid but translated it wrong in my head
Now to your question, they are similar in some aspects, that's what makes gasses and liquids both be considered fluids, so fluid dynamics apply to both for example.
The difference is how much the molecules in the liquid or gas interact: A lot in the liquid, not significantly in most gasses under standard conditions.
And the things is, the SLPM measure apparently relies on a characteristic of ideal gasses, that one mol of gas particles under standard conditions always takes a fixed volume 22.41 l. So now I'm confused why they would use it for hydraulic fluid, which sounds like a liquid to me.
Volume changes based on temperature and pressure. So when we reference volume measurements like for flow rates, we typically do the math to adjust those to standard temperature and pressure. Standard pressure is 1 atm but standard temperature varies based on who you're talking to because of competing standards. It's usually 25 C or 20 C.
When we want to reference the non temperature and pressure corrected volume, we append actual to it so that people know what the measurement is. Some people don't do that and that causes confusion for others using their work if the reading is standard or actual.
You mean the flow rate of a volume of liquid? What are you confused about exactly?
They're asking why it's "standard litres per minute", instead of just "litres per minute"
Oh, well yeah Standard liters per minute or SLM, specifically refers to flow rates measured in the U.S.
So the “other” measurement would evidently be Europes “Normal liters per minute”.
What the difference is, I couldn’t tell you.