Ambitious ORC Turbine

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

solarenergyadventures

Active Member
Joined
Sep 20, 2012
Messages
34
Reaction score
15
Glad you jumped in Solarenergyadventures,...always nice to get input from someone with actual experience with ORC.

Some 50 years ago I was taught that the Ideal Gas Law, PV=nRT, only works for an ideal gas, which doesn't actually exist in the real world,...but that PV=nRT will get you pretty close; I've never had a reason to doubt that,...until today.

So, looking a little closer at the thermo tables Steamchick and I have both been using, under the heading, Equations, in the DuPont Suva paper on the Thermodynamic Properties of HCFC123 it's stated that the Modified Benedict-Webb-Rubin (MBWR) equation of state was used to calculate the tables of thermodynamic properties,...PV=nRT was not used.

Since I was using the DuPont Suva table to get the values I referenced in posts #56 & #58, I was wrong to state that those values were derived from PV=nRT.

But, I'm still left with the question: am I using the DuPont Suva table correctly? I determined the gas volume expanded 5.38 times as it passes through the turbine nozzle. At the most restricted part of the nozzle, Using Table 1, I find at 183°C the gas volume is 0.0022. The gas will expand 5.38 times as it passes through the nozzle, so 0.0022 x 5.38 = 0.0118. Again from Table 1, the new gas volume of 0.0118 corresponds to a temperature of 126°C or 127°C. Therefore, the nozzle will have a temperature drop from 183°C to 126°C.

If you've used similar thermo charts in your work, I'ld appreciate your feedback.
I looked at the table, and I do believe you are interpreting the volume correctly. Are you planning to superheat above 183 C? Keep in mind that as the gas expands and cools, it will be dropping into the wet region under the "steam dome." At this point, some of your steam will have started to condense, and turbines don't really like being bead blasted by little liquid droplets. Superheat would move the point that you start your expansion up and to the right allowing your isentropic expansion to mostly avoid the steam dome. Some moisture is okay, but too much can tear things up.

Looking at previous posts, I see you are planning to use aluminum for your boiler. In my humble opinion, this is not a good idea. Steel pipe is easily available, cheap, roughly three times stronger than aluminum, and, most importantly, does not lose strength at such a low temperature.
Cheers all!
 

Toymaker

Well-Known Member
HMEM Supporting Member
Joined
Jan 26, 2022
Messages
237
Reaction score
98
Location
Thailand
I looked at the table, and I do believe you are interpreting the volume correctly. Are you planning to superheat above 183 C? Keep in mind that as the gas expands and cools, it will be dropping into the wet region under the "steam dome." At this point, some of your steam will have started to condense, and turbines don't really like being bead blasted by little liquid droplets. Superheat would move the point that you start your expansion up and to the right allowing your isentropic expansion to mostly avoid the steam dome. Some moisture is okay, but too much can tear things up.

Always nice to get confirmation from someone who's done this before,...thank you.

Because I want to keep those aluminum boiler tubes from losing too much strength as they get warm, I don't plan to superheat above 183C.

I dont fully understand why, but I do know that some fluids are classified as "wetting fluids", such as steam, for the reasons you've stated, while others are classified as "drying fluids", meaning they don't tend to form little condensation droplets as the gas cools; that web page I sent you , Power from the sun, talks briefly about this. As far as I know, R123 falls into the "drying" category. I wont use a working fluid that is classified as "wetting".

Looking at previous posts, I see you are planning to use aluminum for your boiler. In my humble opinion, this is not a good idea. Steel pipe is easily available, cheap, roughly three times stronger than aluminum, and, most importantly, does not lose strength at such a low temperature.
Cheers all!

Yep, I know I'm getting myself into quite a challenge by attempting to use aluminum tubing in the boiler. I've devised a few simple experiments I'll perform to insure the aluminum tubing, and of equal importance, the aluminum brazing, are both up to the task. Only if the aluminum cant take the heat will I replace it with steel or copper or perhaps titanium tubing, and even then I will start by replacing only the hottest section, leaving the remaining tubing aluminum. Boilers are one of the heavier parts of any Steam engine, and one of my goals is to make the entire engine as light as possible.
 
Joined
Apr 2, 2020
Messages
2,848
Reaction score
894
Location
Sunderland , UK.
Hi Solar-man. I appreciate some expertise joining the discussions. I am only here because it sounds like an interesting project, and while I have little Thermodynamics knowledge -definitely not expert! - I am trying to learn how to work things out using this model. So I'll be very glad of advice from someone who has done the calcs.
K2
 

solarenergyadventures

Active Member
Joined
Sep 20, 2012
Messages
34
Reaction score
15
Always nice to get confirmation from someone who's done this before,...thank you.

Because I want to keep those aluminum boiler tubes from losing too much strength as they get warm, I don't plan to superheat above 183C.

I dont fully understand why, but I do know that some fluids are classified as "wetting fluids", such as steam, for the reasons you've stated, while others are classified as "drying fluids", meaning they don't tend to form little condensation droplets as the gas cools; that web page I sent you , Power from the sun, talks briefly about this. As far as I know, R123 falls into the "drying" category. I wont use a working fluid that is classified as "wetting".



Yep, I know I'm getting myself into quite a challenge by attempting to use aluminum tubing in the boiler. I've devised a few simple experiments I'll perform to insure the aluminum tubing, and of equal importance, the aluminum brazing, are both up to the task. Only if the aluminum cant take the heat will I replace it with steel or copper or perhaps titanium tubing, and even then I will start by replacing only the hottest section, leaving the remaining tubing aluminum. Boilers are one of the heavier parts of any Steam engine, and one of my goals is to make the entire engine as light as possible.
That makes sense. I was reading through your earlier posts and noticed you are planning to drive a turbocharger compressor with your engine. What happens to all that high volume/ medium pressure air from the turbocharger compressor?
 

Toymaker

Well-Known Member
HMEM Supporting Member
Joined
Jan 26, 2022
Messages
237
Reaction score
98
Location
Thailand
That makes sense. I was reading through your earlier posts and noticed you are planning to drive a turbocharger compressor with your engine. What happens to all that high volume/ medium pressure air from the turbocharger compressor?

The complete answer to your question gets pretty complicated, but the short answer is: all that air flow will be the primary thrust producer for a large quadcopter (aka: a drone).

Much more complicated answer:
Finishing the steam turbine is only the first step in my larger experimental project that involves using the field of fluidics and applying it to propulsive thrust. If you're not already familiar with the Coanda effect, please watch this short YouTube video on the Coanda Effect; if you're already familiar with the basic aerodynamics of how air flows over a wing, skip ahead in the video to the 4:55 time mark. The video doesn't mention it, but this is the principle of how the Dyson fan works, and more importantly, it shows how high velocity air can be used to force a much larger volume of air to be added to the thrust producing airflow. At this point, we need to understand that the overall thrust didn't magickly increase; total thrust is still governed by F=ma and the Coanda effect thruster simply changed a small amount of high velocity air into a much larger volume of lower velocity air, keeping "F" pretty much unchanged.

So if the Coanda effect thruster didn't increase thrust, then why use it at all,...what's the advantage?
In all aircraft, efficiency is greatest when the velocity of the exhaust gases from a jet engine is only slightly higher then the forward velocity of the aircraft. Applying this fact to an aircraft that's hovering, (zero forward velocity) it's easy to see that we need very large volumes of low velocity air if we want to hover, which is why helicopters have such long blades, and not the smaller propellers found on similar sized airplanes.

If you're still interested, it's time to watch another short video:
Jetoptera. The Jetotera planes are pretty innovative, but they are not the first to use the Coanda effect to augment thrust in an aircraft, as it appears they've borrowed extensively from the Rockwell XFV-12 built in the late 1970's for the US Navy; this was America's first serious attempt to build a supersonic fighter plane with VTOL capabilities. Although the XFV-12 program was ultimately cancelled, engineers learned a great deal about fluidics as applied to aircraft.

Referencing the Jetoptera video, my plan is to replace their jet engine, which supplies the airflow into their Coanda effect thrusters, with a steam turbine driving a centrifugal compressor. Because I'll be supplying my Coanda effect thrusters with relatively cold air, I can use light weight materials such as plastics, carbon fiberglass, and aluminum for their fabrication.

This is one of the most ambitious projects I've ever taken on, but I'm retired now, and have lots of time to take one vary small step at a time, and then slowly put all those pieces together; it's what I enjoy doing.

A bit of trivia: whether I succeed or not, I wont be the first person to build a plane powered by a steam engine. In 1933 the Besler brothers built and flew their Steam powered Biplane. Imagine,...flying a plane powered by a steam driven twin-piston engine! Just Amazing !
 

Toymaker

Well-Known Member
HMEM Supporting Member
Joined
Jan 26, 2022
Messages
237
Reaction score
98
Location
Thailand
Boiler Design & online calculator How much tubing will I need?

I'm still waiting for an IR thermometer to arrive from an eBay purchase, which allow me to read the actual temperature of the burner's exhaust flames, but for now, based on the bright yellow color of the flame, I'll guess the temperature is between 1200 C to 1400 C. Since the burner is being fed by a centrifugal air blower (aka leaf blower) I will assume the flame temp will not drop across the hottest section of the boiler tubing. I will also assume the feed pump is large enough to keep the "steam" moving rapidly through the 8mm OD tubing.

While researching the topic of Heat Transfer, I came across an online calculator that I believe can be used to help determine how much tubing will be required.

If I'm right and I'm using the calculator correctly, I will need less than 1/2 meter length of 8mm OD tubing. My instincts are telling me that can't be right,...seems way too little. And maybe I've got this part wrong. But I will walk through the process and those that have done these calculations before can check my work.
Assume I want to get approx 150 kW output.
If I go with my original plan and use Aluminum tube, the calculator inputs and single output are as follows:

200 k - thermal conductivity (W/(mK)
0.0008 A - area (m2)
1200 t1 - temperature 1 C
184 t2 - temperature 2 C
0.001 s - material thickness (m)

Heat transfer (W): 162560

I only need 0.0008 sqr meters of tube surface. Even using the ID surface area of an 8mm OD tube, the tube length needed is less than 1/2 meter. This seems impossibly short, yes ??

If these calculations are accurate, I no longer need to be concerned about the weight of tubing in the hottest section of the boiler, and I can easily use copper or steel tubing instead.

Comments Please.
 
Joined
Apr 2, 2020
Messages
2,848
Reaction score
894
Location
Sunderland , UK.
I agree with expectations of flame temp from colour....
I haven't checked your calculations, but the simple "tools" (calculations) usually work correctly.

I should use steel tubing: Safest in case of pump failure, or whatever... "expect the unexpected" - The strongest is always best!
K2
 

Bentwings

Well-Known Member
HMEM Supporting Member
Joined
Jun 18, 2020
Messages
984
Reaction score
165
Location
Minnesota
The complete answer to your question gets pretty complicated, but the short answer is: all that air flow will be the primary thrust producer for a large quadcopter (aka: a drone).

Much more complicated answer:
Finishing the steam turbine is only the first step in my larger experimental project that involves using the field of fluidics and applying it to propulsive thrust. If you're not already familiar with the Coanda effect, please watch this short YouTube video on the Coanda Effect; if you're already familiar with the basic aerodynamics of how air flows over a wing, skip ahead in the video to the 4:55 time mark. The video doesn't mention it, but this is the principle of how the Dyson fan works, and more importantly, it shows how high velocity air can be used to force a much larger volume of air to be added to the thrust producing airflow. At this point, we need to understand that the overall thrust didn't magickly increase; total thrust is still governed by F=ma and the Coanda effect thruster simply changed a small amount of high velocity air into a much larger volume of lower velocity air, keeping "F" pretty much unchanged.

So if the Coanda effect thruster didn't increase thrust, then why use it at all,...what's the advantage?
In all aircraft, efficiency is greatest when the velocity of the exhaust gases from a jet engine is only slightly higher then the forward velocity of the aircraft. Applying this fact to an aircraft that's hovering, (zero forward velocity) it's easy to see that we need very large volumes of low velocity air if we want to hover, which is why helicopters have such long blades, and not the smaller propellers found on similar sized airplanes.

If you're still interested, it's time to watch another short video:
Jetoptera. The Jetotera planes are pretty innovative, but they are not the first to use the Coanda effect to augment thrust in an aircraft, as it appears they've borrowed extensively from the Rockwell XFV-12 built in the late 1970's for the US Navy; this was America's first serious attempt to build a supersonic fighter plane with VTOL capabilities. Although the XFV-12 program was ultimately cancelled, engineers learned a great deal about fluidics as applied to aircraft.

Referencing the Jetoptera video, my plan is to replace their jet engine, which supplies the airflow into their Coanda effect thrusters, with a steam turbine driving a centrifugal compressor. Because I'll be supplying my Coanda effect thrusters with relatively cold air, I can use light weight materials such as plastics, carbon fiberglass, and aluminum for their fabrication.

This is one of the most ambitious projects I've ever taken on, but I'm retired now, and have lots of time to take one vary small step at a time, and then slowly put all those pieces together; it's what I enjoy doing.

A bit of trivia: whether I succeed or not, I wont be the first person to build a plane powered by a steam engine. In 1933 the Besler brothers built and flew their Steam powered Biplane. Imagine,...flying a plane powered by a steam driven twin-piston engine! Just Amazing !
Look into the Tesla turbines there is a guy making a model that has don some remarkable work with them I think he is building a new one with ceramic bearings so it can rev higher
 

Toymaker

Well-Known Member
HMEM Supporting Member
Joined
Jan 26, 2022
Messages
237
Reaction score
98
Location
Thailand
150kW is a big engine. - WOW!
K2

I recently calculated the power output of my little 3 stage turbine using the calculated enthalpy drop across each stage and came up 144 kW output. That's a rough number that doesn't take into account number of blades at each stage, power from impulse & reaction forces of each stage, tip clearance losses, RPM, etc. But I suspect that number wont drop below 100 kW, nor is it likely to go above 200 kW.

So spec'ing the boiler at 150 kW seems like a nice place to start. :)
 
Joined
Apr 2, 2020
Messages
2,848
Reaction score
894
Location
Sunderland , UK.
Hi Toymaker,
I have been pondering to try and understand all this: As you say earlier, "I will try to operate the boiler in the super critical pressure-temperature region for R123, meaning that I need to keep the pressure at or a little above 526 psi (3627 kPa ), and the temperature at or a little below 183°C, which will keep the R123 in a liquid state. My goal is keep the working fluid, R123, in it's liquid stated until it reaches the De Laval nozzles (or convergent-divergent nozzles). As the R123 liquid passes through the nozzles it will flash into a vapor" I assumed that the liquid state was intended to pass all the way through from the heating coils, the aluminium bent tubes towards the turbine, the conical part and up to the first set of fixed blades - that I understand form the De Laval nozzles... the first part of the first stage of the turbine...?
So at what point do you envisage the Liquid turning to gas, so I can "stop using my supercritical approach" (Sorry, I didn't mean to offend, just try and learn how this works).
I am not "having the working fluid remain a liquid right up to the nozzle exit, and instead do the calculations for a vapor state at the nozzle input and output" but I thought that when you said the "liquid stated until it reaches the De Laval nozzles" you meant the narrowest point of the nozzle. It seems logical to me as the expansion starts at the narrowest point I think?
Anyway, my point, is simple - I think? If the liquid turns to gas inside the flame heated part of the plumbing then it will absorb the 18.9kJ/kg. of latent heat it needs for the change of state. BUT it the liquid turns to gas OUTSIDE the heated zone, then it must be an adiabatic process, and the pressure and temperature will drop as the Enthalpy change is zero. So the Liquid at 183C and 3627kPa (abs) with Enthaply of 422.6kJ/kg remains the same enthalpy when it becomes gas at 71C and pressure of 388kPa (abs). At least, this is what I understand the thermodynamics to say from the tables Thermodynamic Properties of HCFC-123, SI units (frigoristes.fr) - which I use as I would normally use steam tables. This is still an input to the Laval nozzles in GAS form of 41psi (bar) or 56psi (abs).... I think Absolute pressure is more appropriate, as you will have the suction from the compressor to re-pressurise the gas and liquidise it as it is pumped back to the boiler pipework. Thinking of how the boiler pipework must end in some sort of manifold in order to travel down the aluminium pipes to the turbine, I guess that the liquid will lose pressure slightly there and start to boil and cool, and may be totally gasified by the time it reaches the compression side of the De Laval nozzles... Are these in the hot or cold zone? System diagram in post #1 suggests the cold zone, so adiabatic change of state will more likely occur there, not at the De Laval nozzles.
Have I understood this correctly yet?
Thanks,
K2
 
Joined
Apr 2, 2020
Messages
2,848
Reaction score
894
Location
Sunderland , UK.
re: post #71. Specifying the boiler for 150kW is a fair sized boiler! As a comparison, a domestic central heating boiler of 30kW sits in my kitchen... so you want a boiler 5 times as big. (That deserved the "Wow!").
I know a locomotive boiler that uses 27kW of gas (determined from pressure and jet size), which is on a 5 inch gauge chassis. So 150kW could be the sort of boiler for a loco for a 13inch gauge track (or whatever!). Have you calculated the "fuel-power" you are pumping into your burner? (I may have missed it in an earlier post).

I think (again, not an expert, just a novice learning how to do this) - that you can take the 150kW and translate it into the kgs per second of liquid HCFC123 you need to pump into the boiler to extract the heat, by using the difference in Enthalpy of the HP and cold liquid (post pump) to the Enthalpy of the HP and hot liquid. - Values taken form the table I attached earlier - as the pump power (I think?) does the change of state from LP cold gas to HP liquid...?
Ta,
K2
 
Joined
Apr 2, 2020
Messages
2,848
Reaction score
894
Location
Sunderland , UK.
I am fascinated by your project. Considering the exhaust from your burner: and the coanda effect nozzles....
The momentum exchange of moving gases reacting on the host vehicle causes thrust. So if the host vehicle generates a lot of low pressure hot gas, made of larger molecules than N2 and O2 in air, then it may be a good idea to inject this gas into the coanda nozzle. The basis is that this gas is initially a part of the vehicle, so when accelerated and ejected from the nozzle will add to the momentum ejected backwards, thus increasing the momentum reaction force forwards....
I think?
If so, perhaps it should be in the form of a De Laval nozzle in the middle of the coanda nozzle, and thus the exhaust gas jet can enhance the mass of air drawn through the coanda nozzle, utilising the last of the heat energy in the exhaust as it expands and cools adiabatically through the nozzle...?
Sorry if this is a crazy idea, but perhaps worth considering?
K2
 

Toymaker

Well-Known Member
HMEM Supporting Member
Joined
Jan 26, 2022
Messages
237
Reaction score
98
Location
Thailand
Hi Toymaker,
I have been pondering to try and understand all this: As you say earlier, "I will try to operate the boiler in the super critical pressure-temperature region for R123, meaning that I need to keep the pressure at or a little above 526 psi (3627 kPa ), and the temperature at or a little below 183°C, which will keep the R123 in a liquid state. My goal is keep the working fluid, R123, in it's liquid stated until it reaches the De Laval nozzles (or convergent-divergent nozzles). As the R123 liquid passes through the nozzles it will flash into a vapor"

The three most important words out of everything I stated above, are, I will try :) I am not at all confident that I can accomplish this.
The only reason for my wanting to operate in the super critical region is because the R-123 would remain in the liquid state, therefore remaining more dense, which means greater contact with the walls of the boiler tubes and therefore capable of carrying away more heat from the Aluminum tubes. For me, it's only a secondary benefit that the entire engine should operate a bit more efficiently.

I assumed that the liquid state was intended to pass all the way through from the heating coils, the aluminium bent tubes towards the turbine, the conical part and up to the first set of fixed blades - that I understand form the De Laval nozzles... the first part of the first stage of the turbine...?

You got it right all the way up to the nozzle. The R-123 will flash into a vapor just as it passes through the narrowest section of the nozzle. If all goes as planned, the gaseous R-123 will greatly accelerate, perhaps reaching Mach 2 as it reaches the entrance to the first row of rotor blades.

So at what point do you envisage the Liquid turning to gas, so I can "stop using my supercritical approach" (Sorry, I didn't mean to offend, just try and learn how this works).
I am not "having the working fluid remain a liquid right up to the nozzle exit, and instead do the calculations for a vapor state at the nozzle input and output" but I thought that when you said the "liquid stated until it reaches the De Laval nozzles" you meant the narrowest point of the nozzle. It seems logical to me as the expansion starts at the narrowest point I think?

Yes, exactly right.

Anyway, my point, is simple - I think? If the liquid turns to gas inside the flame heated part of the plumbing

The only way for that to happen is if my tubing springs a leak and the pressure drops. Otherwise, the flames will be washing the tubing in 1200 C exhaust gasses, keeping the R-123 firmly in a super critical liquid state,...assuming of course that I can actually attain and keep the super critical condition inside the boiler.

then it will absorb the 18.9kJ/kg. of latent heat it needs for the change of state. BUT it the liquid turns to gas OUTSIDE the heated zone, then it must be an adiabatic process, and the pressure and temperature will drop as the Enthalpy change is zero. So the Liquid at 183C and 3627kPa (abs) with Enthaply of 422.6kJ/kg remains the same enthalpy when it becomes gas at 71C and pressure of 388kPa (abs).

This is where you and I disagree.

I think understanding how the process works will be easier if, for the moment, we step away from using a supercritical fluid and consider only the gaseous state. On the input side of the nozzle the gas temp is 183 C, the pressure is 3627.05 kPa and the enthalpy of our R-123 is 441.5 kJ/kg. The most restricted part of the nozzle has an area of 0.231 sqr inches, and after the R-123 passes through the nozzle openings it expands until it reaches the first rotor blades, where the total area is 1.185 sqr inches. So the gases have expanded 5.13 times. From the R-123 properties table we see that the volume of the gas at the smallest part of the nozzle, when it was still at 183 C, is 0.0022 m3/kg. We just calculated that the volume of the gas expanded 5.13 times. So 5.13 x 0.0022 m3/kg = 0.01128 m3/kg; this is the new volume we need to look up on our table, and it's at 128 C (not 71 C).

At least, this is what I understand the thermodynamics to say from the tables Thermodynamic Properties of HCFC-123, SI units (frigoristes.fr) - which I use as I would normally use steam tables. This is still an input to the Laval nozzles in GAS form of 41psi (bar) or 56psi (abs).... I think Absolute pressure is more appropriate, as you will have the suction from the compressor to re-pressurise the gas and liquidise it as it is pumped back to the boiler pipework. Thinking of how the boiler pipework must end in some sort of manifold in order to travel down the aluminium pipes to the turbine, I guess that the liquid will lose pressure slightly there and start to boil and cool, and may be totally gasified by the time it reaches the compression side of the De Laval nozzles... Are these in the hot or cold zone? System diagram in post #1 suggests the cold zone, so adiabatic change of state will more likely occur there, not at the De Laval nozzles.
Have I understood this correctly yet?
Thanks,
K2

There is no manifold. All 8 tubes feeding into the turbine's steam chest have their own separate tube on the inside of the boiler. All tubes external to the boiler will be covered in insulation to limit heat loss. Given the high flow rate of 183 C fluid between the boiler and the nozzle, I suspect all components will heat up to 183 C very quickly, after which there will no longer be any heat loss.
 
Last edited:

Bentwings

Well-Known Member
HMEM Supporting Member
Joined
Jun 18, 2020
Messages
984
Reaction score
165
Location
Minnesota
Hi Toymaker,
I have been pondering to try and understand all this: As you say earlier, "I will try to operate the boiler in the super critical pressure-temperature region for R123, meaning that I need to keep the pressure at or a little above 526 psi (3627 kPa ), and the temperature at or a little below 183°C, which will keep the R123 in a liquid state. My goal is keep the working fluid, R123, in it's liquid stated until it reaches the De Laval nozzles (or convergent-divergent nozzles). As the R123 liquid passes through the nozzles it will flash into a vapor" I assumed that the liquid state was intended to pass all the way through from the heating coils, the aluminium bent tubes towards the turbine, the conical part and up to the first set of fixed blades - that I understand form the De Laval nozzles... the first part of the first stage of the turbine...?
So at what point do you envisage the Liquid turning to gas, so I can "stop using my supercritical approach" (Sorry, I didn't mean to offend, just try and learn how this works).
I am not "having the working fluid remain a liquid right up to the nozzle exit, and instead do the calculations for a vapor state at the nozzle input and output" but I thought that when you said the "liquid stated until it reaches the De Laval nozzles" you meant the narrowest point of the nozzle. It seems logical to me as the expansion starts at the narrowest point I think?
Anyway, my point, is simple - I think? If the liquid turns to gas inside the flame heated part of the plumbing then it will absorb the 18.9kJ/kg. of latent heat it needs for the change of state. BUT it the liquid turns to gas OUTSIDE the heated zone, then it must be an adiabatic process, and the pressure and temperature will drop as the Enthalpy change is zero. So the Liquid at 183C and 3627kPa (abs) with Enthaply of 422.6kJ/kg remains the same enthalpy when it becomes gas at 71C and pressure of 388kPa (abs). At least, this is what I understand the thermodynamics to say from the tables Thermodynamic Properties of HCFC-123, SI units (frigoristes.fr) - which I use as I would normally use steam tables. This is still an input to the Laval nozzles in GAS form of 41psi (bar) or 56psi (abs).... I think Absolute pressure is more appropriate, as you will have the suction from the compressor to re-pressurise the gas and liquidise it as it is pumped back to the boiler pipework. Thinking of how the boiler pipework must end in some sort of manifold in order to travel down the aluminium pipes to the turbine, I guess that the liquid will lose pressure slightly there and start to boil and cool, and may be totally gasified by the time it reaches the compression side of the De Laval nozzles... Are these in the hot or cold zone? System diagram in post #1 suggests the cold zone, so adiabatic change of state will more likely occur there, not at the De Laval nozzles.
Have I understood this correctly yet?
Thanks,
K2
You are way beyond me here . My experience was more in aerodynamics and orface flow. The poin in orfaces was not exceeding super sonic and reducing turbulence. It’s been many years and I don’t have the sophisticated computer programs that let you see graphically what was happening . I did get to observe what happens to very critical snd dangerously corrosive effects materials that were forced outside the envelope. It resulted in “ extremely rapid decomposition with release of very great pressures “ more commonly called explosions . It was often said our batteries were more powerful than the ordinance . Thank goodness we had a nice bunker
 

Bentwings

Well-Known Member
HMEM Supporting Member
Joined
Jun 18, 2020
Messages
984
Reaction score
165
Location
Minnesota
You are way beyond me here . My experience was more in aerodynamics and orface flow. The poin in orfaces was not exceeding super sonic and reducing turbulence. It’s been many years and I don’t have the sophisticated computer programs that let you see graphically what was happening . I did get to observe what happens to very critical snd dangerously corrosive effects materials that were forced outside the envelope. It resulted in “ extremely rapid decomposition with release of very great pressures “ more commonly called explosions . It was often said our batteries were more powerful than the ordinance . Thank goodness we had a nice bunker
Pardon my ignorance but what is this 123 you note? Sounds like a refrigerant or something similar.
 
Joined
Apr 2, 2020
Messages
2,848
Reaction score
894
Location
Sunderland , UK.
Hi Owen, I appreciate your efforts trying to unscramble my brain, but maybe we had better just leave it there. I was never able to pass my thermodynamics exams, as I seem to have a mental block that gives the "wrong" answers.
In this case, it is how the fluid gets from the liquid to gaseous state, so you can do you gaseous expansion from nozzle to turbine blades. I think we have to get the 18.6kJ/kg. of latent heat from the liquid enthalpy, (because that's what I have been working on when I use similar tables for water/steam change of state). But I can't see how you manage that bit of the calculation.
No hassle, I'll sort it out in time.
Thanks for your patience.
K2
 

Toymaker

Well-Known Member
HMEM Supporting Member
Joined
Jan 26, 2022
Messages
237
Reaction score
98
Location
Thailand
Pardon my ignorance but what is this 123 you note? Sounds like a refrigerant or something similar.

You're correct !! R-123 (also known as HCFC-123) was developed as a refrigerant, but has also been used as the working fluid in numerous heat expansion engines. If you click on R-123 the link will take you to a pdf document on it's Thermodynamic Properties.
 

Toymaker

Well-Known Member
HMEM Supporting Member
Joined
Jan 26, 2022
Messages
237
Reaction score
98
Location
Thailand
re: post #71. Specifying the boiler for 150kW is a fair sized boiler!
<snip>
Have you calculated the "fuel-power" you are pumping into your burner? (I may have missed it in an earlier post).
<snip>
Ta,
K2

Yes. My burner uses a siphon type fuel nozzle that's rated to burn 14L/h maximum. 1 liter of Diesel fuel = 10.6 kWh. So, 10.6 kWh x 14 L/h = 148.4 kW

The few test runs I've done with the burner have shown that the nozzle will supply a bit more fuel flow than the 14 L/h rating; I'm fairly certain that I can get 15 L/h, giving me 160 kW.
 
Last edited:

Latest posts

Top