More powerful batteries to make steam?

[MuzzerParticipant @muzzer]

Posted by Ian P on 30/09/2018 21:32:11:

Posted by Neil Wyatt on 30/09/2018 16:35:57:

I'm pretty sure a wallpaper stripper would work fine for testing unloaded model steam engines. I think the pressure caps are rated 4psi, enough to turn most small models but not more.

But they use a lot of electricity compared to what a compact battery can deliver.

N.

I think the pressure cap is fitted as a last resort in case the steam outlet got blocked. In normal use the boiler/heater generates very little pressure, probably only slightly above ambient but obviously enough to induce the steam to travel along the large bore outlet hose.

If the boiler output was restricted by being connected to an engine the pressure would build up and possibly move the piston but I suspect it would not be able to generate steam fast enough to keep the crankshaft turning. That's what I think anyway as I have no live steam experience.

Ian P

No, that's the problem. You will continue to generate steam, no matter what back pressure you impose on it. You can calculate the amount of water you are converting to steam quite easily.

The heat of evaporation of water is about 2200 kJ/kg, so every 2200 J will result in the evaporation of about 1 ml of water. If you had a 2.2kW steam generator, you would evaporate about 1ml per second. The volume of steam is about 1600 times that of water at atmospheric pressure, so you would be generating about 1.6 litres of steam per second.

Obviously if you restrict it, the pressure will rise and the resultant volume per ml will decrease but it won't reach equilibrium unless you tun off the electricity or allow it to escape. Failure to do so is likely to cause you to "make mud" and put you in hospital or a box.

Murray

[Sam StonesParticipant @samstones42903]

My 'Tongue-in-cheek' are getting worser by the minute, Murray.

Sam

[Neil WyattModerator @neilwyatt]

Posted by Muzzer on 01/10/2018 17:00:41:

The heat of evaporation of water is about 2200 kJ/kg, so every 2200 J will result in the evaporation of about 1 ml of water. If you had a 2.2kW steam generator, you would evaporate about 1ml per second. The volume of steam is about 1600 times that of water at atmospheric pressure, so you would be generating about 1.6 litres of steam per second.

In practice I'm sure they generate a fair bit less than that, bear in mind they are totally unlagged.

You could add insulation and use a high power dimmer switch to regulate the steam rate, as long as you didn't block the safety cap.

Neil

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