So, the objective is to generate a water flow similar to a household water system (60 PSI) inside copper pipes that have 30 coil turns that are inside a stove that burns wood.

Illustration of a monotube pumpless boiler

A monotube steam generator is basically a "boiler" without a pressure vessel/steam drum, generating steam pumping water through a coiled tubing above a heat source, transforming the water in steam in the process.

The idea here is to make a pumpless monotube boiler, the water will eventually evaporate and push the hydro generator, eventually emptying the copper coil, which will make the water come back into the tubing.

The Problem:

The problem is that this seems too much like the putt putt boat engine, because I'm assuming the water will only flow into the coil once the water inside it turns into steam.

And I found this PDF that affirms that the putt-putt boat only achieves 0,02% of efficiency. And the closest thing I found to this contraption was this putt putt heat engine water pump, but they didn't specify the efficiency of the pump.

putt putt pump explanation illustration

There are also Water-tube Boilers, but I don't know if this system is the same or something else. Simply because the tubes in the water tube are separated and connected to a somewhat pressure vessel. And they also need a water pump.

Water tube boiler explanation illustration

The question:

How efficient would this system be in generating steam pressure (and thus, work)?

Here are the measurements of the stove and copper tubing:

  • Height of stove: 23 cm
  • Diameter of stove: 8cm

Copper pipe has the following measurements:

Copper pipe diagram

  • $\begingroup$ look at how automatic coffeemaker works $\endgroup$
    – jsotola
    Commented Nov 21, 2022 at 19:52

1 Answer 1


You need a pump to make steam because otherwise the water will never flow into the boiler. In this case, you would only get a little water flow when all water went to steam, and pressure in the coil dropped. As soon as any water enters the coil, pressure will instantly rise and flow will stop.

You need a pump.

  • 1
    $\begingroup$ Commercial power boilers , as shown in the lower figure , do not use pumps. Thermal convection provides flow. $\endgroup$ Commented Nov 21, 2022 at 20:30
  • 1
    $\begingroup$ @blacksmith37, Commercial power boilers, of which I have run three, a B&W, & a Foster Wheeler, & nuclear submarine, use feedwater pumps. Thermal convction provides flow inside the boiler. The pump is what makes the "water in" work. You can't get water in unless the water is at a a higher pressure than boiler pressure. $\endgroup$
    – Tiger Guy
    Commented Nov 21, 2022 at 20:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.