Hot cylinder temperature

[Aviator168]

Has anyone put a thermometer in the hot cylinder to check the gas temperature? Do that and you will be in a surprise. The gas temperature in the hot cylinder is actually a lot lower than what people generally believe in a lot of stirling engines. I wrote a program that actually models a heating tube accurately, and when I put the heating data from some commercial stirling in it, the results point to the the reason they have to use hydrogen as the working fluid. The program is only be able to calculate using air as the working gas. When I finish adding the capability of modeling other gases, I am going to upload it here for you guys to check it out.

[Ian S C]

A motor using Hydrogen/Helium can use a lot more heat because the gas is not an insulator as air is. Changing from air to another gas makes quite a difference even in a mildly pressurized motor. Argon seems to work quite well, and easy to get.
Ian S C

[Aviator168]

That is very true, and that's why stirlings don't get adopted as a prime mover. Another very important aspect is the tubes. They are too big and too few. For the same dead volumn, I rather have much shorter, much smaller, and many more tubes. As for argon gas, it is good gas. But for us home builders, nitrogen is better. Nitrogen is about 2/3 of argon in term of weight, conducts heat 50% better, but it also has the twice the specific heat. I have not run the numbers; but I think argon has a small edge. Here is the thing, nitrogen is a lot easier to get than argon; especially in a moving environment.

[Ian S C]

I don't know if it was on this forum, but I read somewhere of someone building heat sensors into an engine, can't remember the results of this exercise.
I'll watch with interest your assessment of the gasses.
Ian S C