This would change too much of TPT to make it feasable for use in an actual future version of TPT (LOTS of saves would be broken), but this would be really good for a mod.

This is my idea for how to make gases more realistic. (and when I say gas in here I mean elements GAS, NBLE, CO2, H2, and O2, FIRE, PLSM, and any other gases I may have not mentioned that are TPT elements)

Do not have gas particles move in random diffusion, nor have them move outward in response to pressure. These behaviors makes them behave a very unnatural way. Instead, have them move in straight lines like the energy particles currently do (phot, elec, neut, prot). Have them bounce off of each other and other particles, so that they behave like actual gas particles would. Do not have them carry a temperature value. Temperature in real life is a description of the behavior of a COLLECTION of particles. Individual particles (atoms or molecules) don't have a temperature. They just have a velocity. In my idea for a mod, when a gas particle comes in contact with a surface that has a high temperature, a certain amount of thermal energy will be transferred from the hotter particle to the colder particle. When the speed of the gas particle represents a kinetic energy that represents the a temperature that is the same temperature as the other particle it collides with the speed of the gas particle will not change because no heat transfer will occur (thermal equilibrium). If a gas particle is hotter than another particle, then the gas particle's speed will decrease and the other particle's temperature will go up. Again this can happen any number of times until the 2 are in thermal equilibrium. And the farther apart they are in temperature the faster the transfer will occur.

So temperature in gas particles will be replaced by speed. And temperature in all other particles will remain temperature.
Here's a basic table for how it would work.
gas to gas
hot gas transfers speed to cold gas

gas to other
hot gas transfers its speed to other particle's temperature

other to gas
hot other transfers its temperature to gas particle's speed

other to other
remains the same as always
hot other transfers its temperature to cold other's temperature


In keeping with the realism theme, lets remove the air pressure and air velocity from this mod. And in its place introduce the concept of force. Whenever a particle colides with another particle, it will impart force to it. That will accelerate whatever it collides with, and in keeping with Newton's laws, there will be an equal and opposite reaction on the first particle. With this collision force framework in place air particles colliding with each other and their surroundings will impart an impact force on what they collide with, and thus the very workings of this new framework accurately simulate pressure. There is NO LONGER a need for a separate framework in TPT to hold air pressure and velocity values.

This means:
no more air velocity and pressure displays
no more pressing "y" key to change air mode
no more need for walls that only affect air
hotter gasses will naturally rise due to decreased density (no more need for separate code to force fire or plasma particles to rise, or for air to rise in ambient temperature mode)
no more need for ambient temperature mode
no more need for ambient temperature display mode
the entire TPT region can be considered a vacuum (not full of air), unless gas particles have been manually placed
the addition of nitrogen element NTGN (so that you can represent air with O2 and NTGN)
changing how things burn (requiring an O2 particle to be directly adjacent to the flamable substance, or at most 1 particle gap between it and the flammable substance)
O2 is consumed when it is used in a fire
overall it behaves a LOT more realistically than TPT
a LOT of current code needed to attempt to force particles to behave correctly can be removed because now they will NATURALLY behave correctly

Schmolendevice:

I'd imagine you want more collision between gas particles instead of the 'simulated' Browning motion? It's something but one concern is what happens to all the hard fluid dynamics work past programmers did for this game and I'd consider it best to be a better 'viewing option.' Sort of like a chemistry mod to edit how things are processed.

 

Algodoo is free and has good particle simulation for rigid body collisions. If you want to see nice simulated browning motion, use this game and literally just make a bunch of circles. Many people have tried to simulate gases and such. Chemistry though in TPT might be viable but ultimately just adds a subatomic particle simulator aspect to the game. I'd guess that TPT is more 'macro.' 

In my suggested mod, you can just throw out those "hard fluid dynamics work past programmers did for this game". Those dynamics take shortcuts to show macro effects, but these can break down and not work at times. The best way to simulate realistic material behavior is start at the atomic level. The reason our real world works like it does is because of the collective actions of particles at the ATOMIC and SUBATOMIC levels. The best way to get materials in a simulator to behave like real world materials is NOT to do macro level simulations, but rather create models at the atomic and subatomic levels, and then the collections of particles in the simulation that make up macro objects and materials is GUARANTIED to behave in a VERY REALISTIC fashion. Once the individual PARTICLES are behaving as they should, everything else at the macro level will likewise start working as it should without any additional macro level simulation code, just as it does in our real universe.

Even the most complex phenomenon in our universe are the result of the smallest particles obeying the laws of physics that govern these smallest particles. And that is how it should be done in TPT as well.

Somebody, PLEASE make this super-realistic TPT mod that I'm suggesting.