Go to Wikipedia and click 'random article' and post what you get!
Here's what I got:
Thimble tube boiler - A thimble tube boiler is a form of steam boiler, usually provided as an auxiliary boiler or heat-recovery boiler. They are vertical in orientation and would be considered a form of water-tube boiler.
Here's what I got:
Thimble tube boiler - A thimble tube boiler is a form of steam boiler, usually provided as an auxiliary boiler or heat-recovery boiler. They are vertical in orientation and would be considered a form of water-tube boiler.