temperature of your hot well?

[artemis]

Bart's got it right.
1. Excess cooling capability in condenser means maximum vacuum - good for the engine.
2. Feedwater heater on exhaust so the heat is not going to waste. Probably means smaller condenser required.
3. Economiser in boiler to use waste hot gas.

The question remains "How hot the "hotwell?" In this situation the only reason for a HOTwell is to de-aerate the feedwater. Otherwise a COLD hotwell would be just fine.

This was the basic system I used on Artemis and the one used by Al Giles on Crest from the mid 1960s one. This was coupled with his hotwell/float control for feedwater. He pumped his feedwater from the hotwell through the engine exhaust preheater and THEN through the hotwell float control. The excess feedwater was bypassed back to the hotwell, thus warming it (over a period of about an hour) to close to 130F. The feed pump was below the bottom of the hotwell and the injector took its water from the water makeup tank. I did the same and was able to maintain a vacuum of 21"Hg average despite some air leakage into the system.

[barts]

Note that the boiler itself is at saturation temperature: 300-400F depending on steam pressure. This means that it cannot efficiently absorb heat from the flue gases once they;re down to 500 or 600F or so - too much area is required. This is where the economizer comes it - because the water is relatively cold (hot well temp unless you're running a feed water heater), there's a bigger temperature difference and heat transfer is aided. In addition, if relatively small tubing is used for the economizer, the flow conditions will be nicely turbulent - and so the heat transfer is aided again. So, if you're running a hot well, make sure to fit a float rather than trying to control the bypass by hand. With the float, the level will go to the point where the flow through the economizer is just sufficient to make up what's coming out of the engine - the continuous flow will help your heat transfer some more.

Note that fitting a large economizer is also a good way of compensating for a boiler that really needs to be a little bigger; it's generally easily done and the boiler won't mind if there are some steam bubbles in the feed.

An infrared thermometer is a great tool for quickly figuring out what's going on in your steam plant, and where you can pick up some more efficiency.

- Bart