I'm not sure what p=1 means, the initial pressure whatever it might be?? And then you say PSI is 1/3 not 5, well 1/3 of a PSI?? But what you say contradicts the ideal gas law which applies to gas in the pressure and temp range I am considering.
On Mon, 17 Jun 2024 at 21:15, Jürg Wyttenbach <ju...@datamart.ch> wrote: > As said, if you start at p=1 and increase T by 100C then psi is 1/3 not 5. > For 200C its 2/3 etc... > > J.W. > On 17.06.2024 11:01, Jonathan Berry wrote: > > Yes but I am assuming the gas is hot enough to behave according to the > ideal gas law. > > And it follows that to a presst decent temp close enough as I understand. > > For my purposes it only has to be close enough. > > Now to be clear what I am talking about has NOTHiNG to do with the TOTAL > pressure, rather the pressure increase with a certain amount of added > energy (thermal). > So if you add enough energy to increase temp by 100 Kelvin from say 300 or > so Kelvin the pressure increase you get will be about 5 PSI, and if you put > double the energy in, especially if the gas is Helium say (Monatomic) you > increase the temp by 200 K degrees instead to a total of say 400K (roughly) > then you get 10 PSI... > > But the amount that 10 PSI must push a Piston to reach go back to 0 PSI > (actually, it's sea level of 14+10 so 24PSI that has to reduce to 10 btu > whatever) is twice as far as if it were just 5 (technically 19) PSI. > So double the force over double the distance (kinda, pressure drops every > millimeter but I did check every millimeter of movement and it does work > out). > > So I think I'm right still. > > > On Mon, 17 Jun 2024 at 20:50, Jürg Wyttenbach <ju...@datamart.ch> wrote: > >> Jonahan >> >> >> Classically pV/T = constant.. So to keep it simple if you increase T by >> 100 (starting at 273K) then the pressure does only increase about 1/3. >> 373/273 about 4/3. >> >> Further gas internal energy is defined by the Gibbs equation that >> includes the entropy. Pressure is not a linear function of added energy >> only T absolute follows p. >> >> The ideal gas law only matches real physics for a certain band of T. >> Never for T below evaporation point that also is defined as an equilibrium. >> So a gas must have enough internal energy to overcome the Van der Waals >> attractive forces to finally behave "ideal". >> >> J.W. >> On 17.06.2024 09:07, Jonathan Berry wrote: >> >> Jürg, the problem with that is if that is so then the thermal capacity of >> the gas would need to increase as temp increases but with say Helium it's >> pretty flat. >> >> Every time I look into the math for increasing temp it is the same, if >> you heat it up twice as much it needs twice as much energy not 4 times as >> much! >> >> So if you aren't disputing the temp that is created with a given energy >> input, then you are disputing the pressure, but the pressure is predicted >> by the Ideal gas law. >> >> So unless you are saying that either the ideal gas law or thermal energy >> goes up at the square and not in a linear manner (feels it might have been >> noticed) you can't be right. >> >> >> On Sun, 16 Jun 2024 at 22:06, Jürg Wyttenbach <ju...@datamart.ch> wrote: >> >>> The energy of a gas is the sum over all kinetic energies. So you need 4x >>> energy input to get 2x average speed = pressure. (comes from momentum >>> exchange!) >>> >>> J.W. >>> >>> >>> On 16.06.2024 10:27, Jonathan Berry wrote: >>> >>> Hooke's law states that if you compress a spring the increase in >>> pressure is linear, if you compress it 1 cm you might have 1 lb of force, >>> if you compress it 2cm you get 2 lb of force. >>> >>> As that is double the force over double the distance it also involved 4 >>> times more work to compress it and 4 times more work out. >>> >>> Reference: >>> http://labman.phys.utk.edu/phys135core/modules/m6/Hooke's%20law.html >>> >>> "If we double the displacement, we do 4 times as much work" >>> >>> Ok, but this seems problematic when the thermal capacity of a gas is not >>> just changed by making it hotter so if you put in 100 Joules and increase >>> the temp 100 Kelvin you get about 5 PSI of pressure increase, but if you >>> input 200 Joules you get about a 200 Kelvin increase and a 10 PSI increase >>> and to compensate for this greater pressure change the piston moves about >>> twice as far, so twice as far with twice the pressure again is 4 times the >>> energy. >>> >>> At 10 times more input you get 100 times more out, at 100 times more in >>> you get 10,000 time more energy out! >>> >>> The energy increase is exponential with linear increase of temp! >>> >>> If this is not so please explain why not? >>> >>> If the ideal gas law wrong about pressure increase being linear with >>> temp? >>> >>> Does the thermal capacity of a gas change more with temp than I'm >>> finding out when I research it? >>> >>> It sure does seem the gas will like the spring with twice the pressure >>> move about twice as much before the piston isn't motivated, and as such it >>> seems some laws of physics are wrong. >>> >>> >>> Jonathan >>> >>> -- >>> Jürg Wyttenbach >>> Bifangstr. 22 >>> 8910 Affoltern am Albis >>> >>> +41 44 760 14 18 >>> +41 79 246 36 06 >>> >>> -- >> Jürg Wyttenbach >> Bifangstr. 22 >> 8910 Affoltern am Albis >> >> +41 44 760 14 18 >> +41 79 246 36 06 >> >> -- > Jürg Wyttenbach > Bifangstr. 22 > 8910 Affoltern am Albis > > +41 44 760 14 18 > +41 79 246 36 06 > >
