Den Pressure - A Definable Hypothesis & Experiments (Scepti, iWitness)

Wow, is your compressor bigger than mine? 

We should know what volume of the container it has? It first accumulates some air within some cavity, right?

Wow, is your compressor bigger than mine?

I dunno, how big is your compressor? What does it have to do with the topic, anyway?

Quote from: jroa on August 04, 2016, 01:14:19 PM

Wow, is your compressor bigger than mine?

I dunno, how big is your compressor? What does it have to do with the topic, anyway?

You seem to be trying to impress us.  How big is yours? 

Quote from: TheRealBillNye on August 04, 2016, 01:38:03 PM

Quote from: jroa on August 04, 2016, 01:14:19 PM

Wow, is your compressor bigger than mine?

I dunno, how big is your compressor? What does it have to do with the topic, anyway?

You seem to be trying to impress us.  How big is yours?

You seem to be ignoring the results of the study.

Quote from: jroa on August 04, 2016, 01:40:16 PM

Quote from: TheRealBillNye on August 04, 2016, 01:38:03 PM

Quote from: jroa on August 04, 2016, 01:14:19 PM

Wow, is your compressor bigger than mine?

I dunno, how big is your compressor? What does it have to do with the topic, anyway?

You seem to be trying to impress us.  How big is yours?

You seem to be ignoring the results of the study.

Which study measured the size of any of our air compressors? 

We should know what volume of the container it has? It first accumulates some air within some cavity, right?

17 gallon.  I'm not sure exactly what you mean by the second question.

Quote from: jroa on August 04, 2016, 01:40:16 PM

Quote from: TheRealBillNye on August 04, 2016, 01:38:03 PM

Quote from: jroa on August 04, 2016, 01:14:19 PM

Wow, is your compressor bigger than mine?

I dunno, how big is your compressor? What does it have to do with the topic, anyway?

You seem to be trying to impress us.  How big is yours?

You seem to be ignoring the results of the study.

Ignore jroa.  He's just trying to flip over the Monopoly board.

Seems to be some poor sportsmanship in this thread.  Sorry if I brought that on. 

Does this help:

https://www.reddit.com/r/askscience/comments/2a3anz/does_a_compressed_air_tank_weigh_more_when_filled/

and

1 cubic foot of air weighs 0.0807 lbs at standard pressure and temperature
there is approx 80 cubic feet of air in a normal rental tank at 2400 psi
so the air in the tank weighs approximately 6.4 lbs
If you enter at 2400 and exit at 500 then you will be about 5.1 lbs lighter than when you went in.

It is becoming clear to me. There are only 2 or 3 posters on this entire website who truly believe and will try to logically defend their hypothesis. Every other FE believer I have spoken with in this forum has been exactly like JROA. They ignore any logical reasoning and attempt to change the subject so nobody notices their flawed thinking. We notice.

Do you?

So, which part of my statements do you disagree with? 

BTW, it was ignored, but my syringe experiment showed that there is no connection between weight and atmospheric pressure.

Quote from: sceptimatic on August 04, 2016, 11:11:46 AM

Quote from: markjo on August 04, 2016, 10:52:18 AM

Are air molecules the only molecules that expand, or can liquid and solid molecules expand too?  Why doesn't a block of wood expand when put into a vacuum chamber if it has air molecules trapped inside it?

Some wood probably would (pardon the pun) but some wood is actually very porous.
A denser wood would probably start to break down if a suitable strong and a strong chamber was used.

Well, that sounds like it would be easy enough to test.  But why would the wood molecules break down instead of expand to fill the chamber?

They don't break down. They expand and break down the wood.

Enough talk!  Let's science!!

Here we see my compressor at 0 psi weighing 52.8lb:



Here we see it at 120psi weighing in at 54.3lb:



Discuss!

How much of that excess weight is water?

Why don't you come up with an experiment that will satisfy you?

Why don't you come up with an experiment that will satisfy you?

I am satisfied.

How much of that excess weight is water?

Yep, and this is another good reason why a balloon's a better example: transparency. We'd generally be able to see it's the same balloon, and usually be able to see if anything else is in it.

Quote from: crutonius on August 04, 2016, 01:11:56 PM

Enough talk!  Let's science!!

Here we see my compressor at 0 psi weighing 52.8lb:



Here we see it at 120psi weighing in at 54.3lb:



Discuss!

How much of that excess weight is water?

Well according to weather.com the humidity where I'm at is 9%.  I'm not totally sure what that number translates into with predicting how much water there is.  So I'm going to throw out a guess and say less than 10% of what's been compressed into that tank is water vapor.  If anyone knows what "humidity" means in the context of a weather report is please feel free to correct me.

Quote from: sceptimatic on August 04, 2016, 03:17:18 PM

How much of that excess weight is water?

Yep, and this is another good reason why a balloon's a better example: transparency. We'd generally be able to see it's the same balloon, and usually be able to see if anything else is in it.

That's right. It's not as simple as 123 these experiments, are they?

Quote from: sceptimatic on August 04, 2016, 03:17:18 PM

How much of that excess weight is water?

Yep, and this is another good reason why a balloon's a better example: transparency. We'd generally be able to see it's the same balloon, and usually be able to see if anything else is in it.

You'd have the same challenge with a balloon.  Worse even if you're using your own breath to fill it up.

Maybe I'll do a balloon test later.  I don't have any right now.

Quote from: Jane on August 04, 2016, 03:28:41 PM

Quote from: sceptimatic on August 04, 2016, 03:17:18 PM

How much of that excess weight is water?

Yep, and this is another good reason why a balloon's a better example: transparency. We'd generally be able to see it's the same balloon, and usually be able to see if anything else is in it.

That's right. It's not as simple as 123 these experiments, are they?

What would make the experiment more transparent? A balloon? Harder to accurately measure it.

Quote from: Jane on August 04, 2016, 03:28:41 PM

Quote from: sceptimatic on August 04, 2016, 03:17:18 PM

How much of that excess weight is water?

Yep, and this is another good reason why a balloon's a better example: transparency. We'd generally be able to see it's the same balloon, and usually be able to see if anything else is in it.

That's right. It's not as simple as 123 these experiments, are they?

I'm not sure the presence of humidity invalidates the experiment.  Whatever humidity in the tank is also present in the air around it.  Wouldn't that cancel out any effect humidity might have?

I've gone ahead and updated Experiment 3 with the Balloon Hypothesis.  I was very busy at work today and skimmed the thread and only halfway understand the experiment so If there is some information that needs more clearly defined please feel free to PM me.  I don't want it getting lost in the pages.

Also I'd encourage everyone to do all the experiments if possible.  I'm not sure if I can accurately do number 1, even with a compressor so it might be up to others to test.

I understand that number 2 could result in some issues with floating.  Would a weight to hold the object down and water covering both the object and weight to the same volume level in each container make the test inaccurate?  (Assuming the same weight is used in each test).

Quote from: TheRealBillNye on August 04, 2016, 01:43:54 PM

Quote from: jroa on August 04, 2016, 01:40:16 PM

Quote from: TheRealBillNye on August 04, 2016, 01:38:03 PM

Quote from: jroa on August 04, 2016, 01:14:19 PM

Wow, is your compressor bigger than mine?

I dunno, how big is your compressor? What does it have to do with the topic, anyway?

You seem to be trying to impress us.  How big is yours?

You seem to be ignoring the results of the study.

Which study measured the size of any of our air compressors? 

Jroa, I'd appreciate it if you do not derail the thread.

Feel free to pm me your results and evidence of results and I can add them to the appropriate experiment posts too.

I still see nothing wrong with the experiment already completed with an air compressor? What does humidity have to do with such an experiment? I would be glad to have some sort of input from a denpressure advocate.

I still see nothing wrong with the experiment already completed with an air compressor? What does humidity have to do with such an experiment? I would be glad to have some sort of input from a denpressure advocate.

I thought about it a little more, did some googling and lo and behold, my air compressor has a drain valve. So I can measure exactly how much of that gain was water. 1oz it turns out.

I'm going to need a better reason to declare that experiment invalid other than humidity.

Enough talk!  Let's science!!

Here we see my compressor at 0 psi weighing 52.8lb:


Here we see it at 120psi weighing in at 54.3lb:


Discuss!

Simple.   Just apply  PV = nRT,    since  Volume,Temperature and R ( assuming ideal gas laws and no phase changes)  are constant only n and P change and they change in linear fashion,   so converting from psig to psia,  the pressure has risen from 14.7 to 134.7 or 9.16 times, so the amount of air in the volume V is 9.16 times. The density of air is 0.0765 lbs/ft³  so  Weight change = V*0.0765*9.16 - V*0.0765  = V*0.624 lbs

Since crutonius didn't tell us the volume V,  (jroa derailed that discussion)  but he did tell us the weight change, so we can backtrack for an estimate of his compressor volume    deltaW = 54.2 - 52.8 = 1.4lbs = V*0.624,   V = 1.4/0.624 = 2.2 cu ft

So what is the actual compressor tank volume?  How close is close enough for a proof?

There will be a temperature change caused by compression,  but given the thermal mass of the steel tank I'd expect it to only contribute a few extra psi to the pressure gage.

PS.  When is America going to join the rest of the world and adopt the metric system!!!

Quote from: crutonius on August 04, 2016, 01:11:56 PM

Enough talk!  Let's science!!

Here we see my compressor at 0 psi weighing 52.8lb:


Here we see it at 120psi weighing in at 54.3lb:


Discuss!

Simple.   Just apply  PV = nRT,    since  Volume,Temperature and R ( assuming ideal gas laws and no phase changes)  are constant only n and P change and they change in linear fashion,   so converting from psig to psia,  the pressure has risen from 14.7 to 134.7 or 9.16 times, so the amount of air in the volume V is 9.16 times. The density of air is 0.0765 lbs/ft³  so  Weight change = V*0.0765*9.16 - V*0.0765  = V*0.624 lbs

Since crutonius didn't tell us the volume V,  (jroa derailed that discussion)  but he did tell us the weight change, so we can backtrack for an estimate of his compressor volume    deltaW = 54.2 - 52.8 = 1.4lbs = V*0.624,   V = 1.4/0.624 = 2.2 cu ft

So what is the actual compressor tank volume?  How close is close enough for a proof?

There will be a temperature change caused by compression,  but given the thermal mass of the steel tank I'd expect it to only contribute a few extra psi to the pressure gage.

PS.  When is America going to join the rest of the world and adopt the metric system!!!

Nice math. My compressor is 17 gallons. Which equals 2.273 cubic feet, very close indeed.

Regarding a proof or disproof of denpressure it's not how much weight gains there was. It's that there was any at all. In fact denpressure predicted that the weight should decrease.

I do share your frustration with the Imperial system. But that's the country I'm in.