Steam cannon idea

[kablooie]

If you really wanted to get fancy you could use a pipe running through the chamber as a heat exchanger and have hot oil in the pipe. You could either use a small pump or a heat-powered pump (no moving parts or external power source). For the second choice you'll have to do some research I think.

Wouldn't steel work at high temperatures? Maybe it would it give off horrible chemical gas, I've noticed when heating steel pipe that it does give off a distinctive smell. Copper w/compression fittings (would solder melt or soften?) would probably work too.

[rp181]

copper would be bad, its a good conductor of heat, so its harder to heat, also finding compression fitting that can handle that kind of pressure and tempeture.

[jimmy101]

Yeah I dont plan on going very high but higher than my pnuematic cannons (120 psi).

You have to remember that the pressure you get is really only limited by the amount of heat you put into the system, hence the maximum pressure the system will reach. There are two limits on the maximum amount of heat you can get into the system. As long as the heater is hotter than the water/steam you will still be adding heat to the system so the pressure will continue to rise. The other limit is heat loss. Once the chamber gets sufficiently hot it'll be loosing heat like crazy to thermal conduction to the environment. Once the heat conduction rate matches the heat output rate of the heater the chamber's temperature and pressure will stop rising.

As long as the heater is hotter than the water/steam and the heat input rate is greater than the heat loss rate the chamber's pressure will continue to rise. You absolutely positively have to have some type of safety relief valve in the system.