First, I’m a retired electronics engineer with almost no formal education in thermodynamics. All the meager knowledge I have on boiler design comes entirely through self-learning. So don’t take anything I state as being 100% accurate. Which means I’m open to advice, critique and suggestions,... which I may, or may not take 
I’ve started designing a Monotube Flash Boiler to be used with the Burner I’ve already built. My boiler design is roughly based on the SES automotive boiler built in the early 1970s which supplied steam at 1000 psi at 1000F, and reportedly provided instantaneous zero-to-full flow. The SES boiler used water as the working fluid, but my boiler will use the Freon R-123, instead of water which will require some major changes as compared to the SES boiler, most notably, a far shorter monotube will be needed.
I copied the below P-h diagram from an internet page which already had existing lines, so please excuse and ignore those lines marked with circled numbers.
Looking at the P-h diagram for water, I’ve drawn a red-orange horizontal line starting at 100C & 7 MPa (1000psi) which roughly intersects the 500C (1000F) line. Moving from left to right along this line represents the enthalpy needed to raise 1 kg of water from roughly 480 kJ on the left up to about 3300 kJ on the right; which means the SES boiler must transfer 2,820 kJ into each kg of water inside the boiler to change it into a useful steam.
Now let’s look at the P-h diagram for R-123:
Starting at the red “1” on the left and going right to the Blue line near the red “3” represents the amount of Enthalpy needed to raise 1kg of R123 from roughly 228 kJ on the left up to about 485 kJ on the right; which means my boiler only needs to transfer 257 kJ into each kg of R123 inside the boiler to change the R123 into a useful vapor at 3.5MPa (500 psi) and 185C.
So, 2,820 kJ for water vs 257 kJ R123,….that’s eleven times less energy per kilogram needed to be transferred into R123 compared to water to go from liquid to useful vapor. In other words, a monotube boiler using R123 will need far less tube surface area compared to a boiler designed to use water.
Below is my current monotube boiler design; wider blue grid lines are 1” spacing. Green circles represent 5/8" tubing. Numbers inside the green circles indicate tube circumference. Total tube length = 348" (29 ft). Tube surface area + Hollow disc = 700 sq in. I'm always fine tuning the design details so expect changes.
Planned flow rate: 5.21 kg/sec.
Hot exhaust gases exit the burner with an annular shape and immediately impact a hollow disc containing flowing liquid R123. The hollow disc is part of the monotubes and will receive both radiant and convective heating.
The photo below is of the burner in operation and is provided here to give readers a visual image of how the exhaust gases exit the burner.
More specs and details in the next post.
I’ve started designing a Monotube Flash Boiler to be used with the Burner I’ve already built. My boiler design is roughly based on the SES automotive boiler built in the early 1970s which supplied steam at 1000 psi at 1000F, and reportedly provided instantaneous zero-to-full flow. The SES boiler used water as the working fluid, but my boiler will use the Freon R-123, instead of water which will require some major changes as compared to the SES boiler, most notably, a far shorter monotube will be needed.
I copied the below P-h diagram from an internet page which already had existing lines, so please excuse and ignore those lines marked with circled numbers.
Looking at the P-h diagram for water, I’ve drawn a red-orange horizontal line starting at 100C & 7 MPa (1000psi) which roughly intersects the 500C (1000F) line. Moving from left to right along this line represents the enthalpy needed to raise 1 kg of water from roughly 480 kJ on the left up to about 3300 kJ on the right; which means the SES boiler must transfer 2,820 kJ into each kg of water inside the boiler to change it into a useful steam.
Now let’s look at the P-h diagram for R-123:
Starting at the red “1” on the left and going right to the Blue line near the red “3” represents the amount of Enthalpy needed to raise 1kg of R123 from roughly 228 kJ on the left up to about 485 kJ on the right; which means my boiler only needs to transfer 257 kJ into each kg of R123 inside the boiler to change the R123 into a useful vapor at 3.5MPa (500 psi) and 185C.
So, 2,820 kJ for water vs 257 kJ R123,….that’s eleven times less energy per kilogram needed to be transferred into R123 compared to water to go from liquid to useful vapor. In other words, a monotube boiler using R123 will need far less tube surface area compared to a boiler designed to use water.
Below is my current monotube boiler design; wider blue grid lines are 1” spacing. Green circles represent 5/8" tubing. Numbers inside the green circles indicate tube circumference. Total tube length = 348" (29 ft). Tube surface area + Hollow disc = 700 sq in. I'm always fine tuning the design details so expect changes.
Planned flow rate: 5.21 kg/sec.
Hot exhaust gases exit the burner with an annular shape and immediately impact a hollow disc containing flowing liquid R123. The hollow disc is part of the monotubes and will receive both radiant and convective heating.
The photo below is of the burner in operation and is provided here to give readers a visual image of how the exhaust gases exit the burner.
More specs and details in the next post.
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