1 Steam Cars : Phorum
General Steam Car topics
Efficient condensing
Posted by: Peter Heid (IP Logged)
Date: May 02, 2003 08:01PM
<HTML>In my quest for the best steam system I can build with the tools and materials I have available, I have noticed a need for an efficient condenser. To insure maximum condensation while keeping a reduced size is important for low weight and minimum air drag. Of course the first step is to run the system as efficiently as possible to cut down on the amount of steam going to the condenser and reduce the heat it contains. In my quest I came across a book from MIT press on air cooled condensers for power plants with a few clues in the efficient condenser hunt.
The first important point is that the air side must be about 10 times the area of the steam/water side on the condenser to accommodate the difference in heat transfer.
The next point seems just as important but hardly spoken, let alone applied to steam vehicles. Velocity is important for turbulent flow which helps promote heat transfer. Just as the boiler might use increasing tubing sizes to allow for the increase in steam volume, as the flow heads toward the outlet of the condenser, the size of the tubing should be reduced. Or the number of passages can be reduced in the flow path to keep the velocity up as the volume decreases. As a general rule, the heat transfer increases to the 0.58th power of the vapor velocity for parallel flow which is much more efficient than counter flow for condensation
An automotive radiator is designed for a 10 to 15 degree differential on the air side while those designed for power plants are designed for a 30 to 40 degree differential.
Based on these 3 bits of information, I can’t see where a normal automotive radiator has much practical application on a steam vehicle. A possible way to use a regular radiator might be by removing the top and bottom tanks and use the core in a more effective way. If the core were turned so the sides were on top and bottom and the tanks were replaced with smaller, individual units to direct the flow back and forth while reducing the number of tubes used. You would be changing from a multi path condenser to a once through type, but using multitubes.
My greatest interest in condensers is the rotary type. No not rotary boiler. Aero Turbines Ltd. of London produced a rotary boiler/turbine of 30 hp in 1938 designed for aircraft use. According to the makers, the rotary boiler could be used as a condenser. The unit could provide maximum heat transmission at 830 ft/sec of 553,000 BTU/sq ft-Hr as a boiler with a pressure of 2200 lbs. If I am not mistaken, this is more than 10 times the heat transfer rate of the next closest boiler. The rotary boiler concept is great but in practice I might have trouble with the seals and all the impurities in the feed will centrifuge to the periphery and plug the passages or create an imbalanced condition. It really doesn’t seem like a project for my skills, tools or materials but the rotary condenser might be. The Aero boiler was run as a condenser and at the speed of 830 ft/sec or 10,000 rpm, the heat transfer was 203,000 BTU/sq ft-sec. The same rotary condenser could be built with a separator for the oil and impurities in the same housing and a great space savings might be seen. The impurities that cause trouble in a rotary boiler are removed before they would enter the rotary condenser and relatively cool, low pressure exhaust steam is much easier to work with when using rotary seals.
It is interesting to note that Aero Turbines claimed a fuel consumption rate of 0.35 lbs/bhp-hr, I think a Doble E was 0.916 when developing 125 hp.
Peter Heid</HTML>
The first important point is that the air side must be about 10 times the area of the steam/water side on the condenser to accommodate the difference in heat transfer.
The next point seems just as important but hardly spoken, let alone applied to steam vehicles. Velocity is important for turbulent flow which helps promote heat transfer. Just as the boiler might use increasing tubing sizes to allow for the increase in steam volume, as the flow heads toward the outlet of the condenser, the size of the tubing should be reduced. Or the number of passages can be reduced in the flow path to keep the velocity up as the volume decreases. As a general rule, the heat transfer increases to the 0.58th power of the vapor velocity for parallel flow which is much more efficient than counter flow for condensation
An automotive radiator is designed for a 10 to 15 degree differential on the air side while those designed for power plants are designed for a 30 to 40 degree differential.
Based on these 3 bits of information, I can’t see where a normal automotive radiator has much practical application on a steam vehicle. A possible way to use a regular radiator might be by removing the top and bottom tanks and use the core in a more effective way. If the core were turned so the sides were on top and bottom and the tanks were replaced with smaller, individual units to direct the flow back and forth while reducing the number of tubes used. You would be changing from a multi path condenser to a once through type, but using multitubes.
My greatest interest in condensers is the rotary type. No not rotary boiler. Aero Turbines Ltd. of London produced a rotary boiler/turbine of 30 hp in 1938 designed for aircraft use. According to the makers, the rotary boiler could be used as a condenser. The unit could provide maximum heat transmission at 830 ft/sec of 553,000 BTU/sq ft-Hr as a boiler with a pressure of 2200 lbs. If I am not mistaken, this is more than 10 times the heat transfer rate of the next closest boiler. The rotary boiler concept is great but in practice I might have trouble with the seals and all the impurities in the feed will centrifuge to the periphery and plug the passages or create an imbalanced condition. It really doesn’t seem like a project for my skills, tools or materials but the rotary condenser might be. The Aero boiler was run as a condenser and at the speed of 830 ft/sec or 10,000 rpm, the heat transfer was 203,000 BTU/sq ft-sec. The same rotary condenser could be built with a separator for the oil and impurities in the same housing and a great space savings might be seen. The impurities that cause trouble in a rotary boiler are removed before they would enter the rotary condenser and relatively cool, low pressure exhaust steam is much easier to work with when using rotary seals.
It is interesting to note that Aero Turbines claimed a fuel consumption rate of 0.35 lbs/bhp-hr, I think a Doble E was 0.916 when developing 125 hp.
Peter Heid</HTML>
Re: Efficient condensing
Posted by: Peter Brow (IP Logged)
Date: May 04, 2003 05:06AM
<HTML>Hi Peter,
Interesting stuff. One thing to keep in mind is that increased steam velocity and turbulent flow on the steam side of a condenser will increase the back pressure on the exhaust, decreasing the efficiency of the engine. Meanwhile, turbulent flow on the air side increases the air drag of the vehicle, cutting fuel mileage. You can condense more steam with these tricks, but at the expense of using more fuel.
I am not yet convinced that a finned radiator is best, though I may end up using one, at least in my first prototype. I suspect that they are universally used in production automobiles because of their greater simplicity and much lower cost -- fewer soldered joints. However, there may be ways to cut the cost of the much better Philips/Saab type "V-front" radiator to competitive levels. Note that modern radiators bond plastic to metal.
I don't like the expression "V-front". Sounds like a standard tube/fin radiator core with a V-shaped front, like an early condensing Stanley. Perhaps "sawtooth-front unfinned micro-tube radiator" or "pleated tube-grid" would be a better description, though it is a mouthful. I should probably put a picture on a web page, so that the design is clear.
As you can tell, I am still intrigued by the Philips/Saab radiator's potential for getting 4x the condensing power for a given frontal area, without the cost or problems of a honeycomb type radiator/condenser. Per your comments, I am considering designing a Philips/Saab (P/S) type radiator for parallel flow, steam running from the front to rear headers, though technically it is mainly a cross-flow design. With maximum temperature differential at every point on the heat-exhange surface -- every square inch of tubing receiving ambient-temperature air -- and lots more of it -- it seems that this type of radiator/condenser can get a lot more heat exchange per square foot of surface area, or, looked at another way, can use much less surface & frontal area for a given heat flow.
In a standard finned radiator, the fins run much cooler than the tubes, rear tubes and fins receive hot air from tubes & fins ahead of them, the temp diffs are lower throughout, and air flow is much less, meaning more square footage is needed for the same heat flow -- relative to the P/S radiator.
Varying the steam/water flowpath area is good for a constant-load system like a stationary powerplant, but for a steam car, where the flow of both air and steam/water will vary considerably and some amount of steam may have to blow through under some conditions, it may not be practical.
The rotary boiler and condenser sound interesting. How are the tubes and fins(?) arranged? Hope it's not as hard to explain in print as the Philips/Saab radiator. :)
Peter</HTML>
Interesting stuff. One thing to keep in mind is that increased steam velocity and turbulent flow on the steam side of a condenser will increase the back pressure on the exhaust, decreasing the efficiency of the engine. Meanwhile, turbulent flow on the air side increases the air drag of the vehicle, cutting fuel mileage. You can condense more steam with these tricks, but at the expense of using more fuel.
I am not yet convinced that a finned radiator is best, though I may end up using one, at least in my first prototype. I suspect that they are universally used in production automobiles because of their greater simplicity and much lower cost -- fewer soldered joints. However, there may be ways to cut the cost of the much better Philips/Saab type "V-front" radiator to competitive levels. Note that modern radiators bond plastic to metal.
I don't like the expression "V-front". Sounds like a standard tube/fin radiator core with a V-shaped front, like an early condensing Stanley. Perhaps "sawtooth-front unfinned micro-tube radiator" or "pleated tube-grid" would be a better description, though it is a mouthful. I should probably put a picture on a web page, so that the design is clear.
As you can tell, I am still intrigued by the Philips/Saab radiator's potential for getting 4x the condensing power for a given frontal area, without the cost or problems of a honeycomb type radiator/condenser. Per your comments, I am considering designing a Philips/Saab (P/S) type radiator for parallel flow, steam running from the front to rear headers, though technically it is mainly a cross-flow design. With maximum temperature differential at every point on the heat-exhange surface -- every square inch of tubing receiving ambient-temperature air -- and lots more of it -- it seems that this type of radiator/condenser can get a lot more heat exchange per square foot of surface area, or, looked at another way, can use much less surface & frontal area for a given heat flow.
In a standard finned radiator, the fins run much cooler than the tubes, rear tubes and fins receive hot air from tubes & fins ahead of them, the temp diffs are lower throughout, and air flow is much less, meaning more square footage is needed for the same heat flow -- relative to the P/S radiator.
Varying the steam/water flowpath area is good for a constant-load system like a stationary powerplant, but for a steam car, where the flow of both air and steam/water will vary considerably and some amount of steam may have to blow through under some conditions, it may not be practical.
The rotary boiler and condenser sound interesting. How are the tubes and fins(?) arranged? Hope it's not as hard to explain in print as the Philips/Saab radiator. :)
Peter</HTML>
Re: Efficient condensing
Posted by: Tom Ward (IP Logged)
Date: May 04, 2003 04:13PM
<HTML>Not long ago I saw a patent for a turbine/feed pump arrangement that acted as an efficient compact condensor. The turbine consisted of a perforated cylinder within a slightly elliptical housing. Exhaust steam entered through a nozzle inside the cylinder while the condensation was pumped out by vanes driven by the turbine. The whole idea was to convert heat into work instead of hot air. Don't know if an actual working model was ever constructed and tested or if this was just a paperwork patent.
I'll check in with the patent number later.</HTML>
I'll check in with the patent number later.</HTML>
Re: Efficient condensing
Posted by: Caleb Ramsby (IP Logged)
Date: May 04, 2003 04:30PM
<HTML>Peter and. . . uh. . . Peter,
I think that the conventional surface condensor that is used in most steam cars is ignoring a siginificant resource that said cars have. That is the water tank.
Let me explain.
My idea is to use a jet condensor with the application of three water pumps, all of which are regular automotive style centrifugal pumps. Why THREE pumps you ask?
Well, the first pump would take water from the water tank and send it to the jet condensor.
The second pump would take the water from the jet condensor and send it to the radiator.
Well that is all normal so far, but, lets keep going.
The third pump would take water from the water tank and send it directly to the radiator.
The second and third pumps would both feed water into a mixing chamber, basically a metal box. From this mixing chamber the water would go into the radiator and from there back to the water tank.
The first and third pump could be ran on the same shaft either by a motor or an auxillary engine.
For simplicity of design I would have all of the pumps running at a sufficient capacity to handle the full output from the main engine at all times. This may sound wastefull, but it would keep the water in the tank cool, so that when the maximum cooling capacity of the system was required, it would have an adequate supply of cool water.
The reason for the third pump is that it would mix the cooler water from the tank with the warmer water coming from the jet condensor and thus increase the steam capacity of the system.
Another benefit is that the water going through the radiator has a greater rate of heat transference than steam. This also increases the condensing capacity of a system.
I think that an oil seperator would also be beneficial before the jet condensor so that the radiator would remain relatively clean.
I also think that the high velocity of the water going through the radiator would help keep it clean, well at least cleaner than if it were just steam entering it.
What do you guys think?
If you like the idea, go ahead and use it. Just remember where it came from!grin
Still thinking. . . I think. . .
Caleb Ramsby</HTML>
I think that the conventional surface condensor that is used in most steam cars is ignoring a siginificant resource that said cars have. That is the water tank.
Let me explain.
My idea is to use a jet condensor with the application of three water pumps, all of which are regular automotive style centrifugal pumps. Why THREE pumps you ask?
Well, the first pump would take water from the water tank and send it to the jet condensor.
The second pump would take the water from the jet condensor and send it to the radiator.
Well that is all normal so far, but, lets keep going.
The third pump would take water from the water tank and send it directly to the radiator.
The second and third pumps would both feed water into a mixing chamber, basically a metal box. From this mixing chamber the water would go into the radiator and from there back to the water tank.
The first and third pump could be ran on the same shaft either by a motor or an auxillary engine.
For simplicity of design I would have all of the pumps running at a sufficient capacity to handle the full output from the main engine at all times. This may sound wastefull, but it would keep the water in the tank cool, so that when the maximum cooling capacity of the system was required, it would have an adequate supply of cool water.
The reason for the third pump is that it would mix the cooler water from the tank with the warmer water coming from the jet condensor and thus increase the steam capacity of the system.
Another benefit is that the water going through the radiator has a greater rate of heat transference than steam. This also increases the condensing capacity of a system.
I think that an oil seperator would also be beneficial before the jet condensor so that the radiator would remain relatively clean.
I also think that the high velocity of the water going through the radiator would help keep it clean, well at least cleaner than if it were just steam entering it.
What do you guys think?
If you like the idea, go ahead and use it. Just remember where it came from!grin
Still thinking. . . I think. . .
Caleb Ramsby</HTML>
Re: Efficient condensing
Posted by: Caleb Ramsby (IP Logged)
Date: May 04, 2003 04:32PM
<HTML>Tom,
Sounds neet, let us know what you find out.
Caleb Ramsby</HTML>
Sounds neet, let us know what you find out.
Caleb Ramsby</HTML>
Re: Efficient condensing
Posted by: Peter Brow (IP Logged)
Date: May 04, 2003 08:27PM
<HTML>Hi Caleb,
Not bad. Similar systems have been tried before. I remember Karl Peterson's spray condenser, essentially a water nozzle that put a fine spray of water into the exhaust steam headed for the radiator. At the opposite end of the condensing chamber, there was a spring-loaded disk, with some clearance around it, which automatically changed the volume of the spray chamber with steam flow/backpressure. Can't remember if the water was circulated through the radiator or just ran straight through.
Another fun idea was John Wetz's percolator/condenser. Exhaust steam went to a bubbler at the bottom of a small percolator column as tall as the radiator. The rising steam bubbles in the column, condensing into the water as they rose, drew water from the bottom of the radiator into the column. Hot water overflowed from the top of the column into the top of the radiator. Recovered water overflowed into the water tank. It was plumbed so that cylinder oil gravitated to the top of the bubbler column, in theory keeping oil out of the radiator and making it easy to recover (skimmer? oil absorber?). Natural circulation was maintained in the radiator and bubbler column with no pumps whatsoever.
I did some conceptual work on that one. Might work in a car, but would need "mods". Volume of water in circulator column would vary with steam flow -- the steam bubbles take time to condense, and meanwhile they take up space!
This is all treading close to my possibly patentable ideas, so my comments will now become cryptic. Remember that it is desireable to keep the air/steam and air/water temperature differential as high as possible for good heat transfer and a smaller/lighter/cheaper heat exchanger. The heavier the oil, the hotter the heat exchanger the better, to avoid clogging. Some oil seems to get through even the best oil separators -- except maybe a water/oil centrifuge like Peter Barrett uses. And don't forget the freezing problem. A water-filled radiator might benefit from automatic means to drain it to an insulated tank when standing or running very slow in freezing weather, and/or thermostatic air shutters like those used in some 1920s-'30s gas cars. In really cold weather, a bare water-filled radiator could freeze up PDQ at a stoplight or in slow-and-go traffic. Then again, water can't freeze if you keep it moving fast enough (but that takes horsepower).
I think it was Jim Crank who mentioned a trick tried by some Stanley owners. They ran the feedwater bypass through the condenser. This condensed all the steam for a while, but, unfortunately, resulted in the water tank overheating & pumps vapor-locking/pounding. By cooling the radiator with all that water, they ironically reduced the amount of heat the radiator was throwing away.
Tom: Very interesting, but weird! Wonder if it worked. Might have just been a paper patent (most are). Still, there is a good bit of potential energy to be recovered by condensing steam, with the right equipment. Cost-effectiveness & available space for equipment are serious issues with vacuum condensing in cars.
Peter</HTML>
Not bad. Similar systems have been tried before. I remember Karl Peterson's spray condenser, essentially a water nozzle that put a fine spray of water into the exhaust steam headed for the radiator. At the opposite end of the condensing chamber, there was a spring-loaded disk, with some clearance around it, which automatically changed the volume of the spray chamber with steam flow/backpressure. Can't remember if the water was circulated through the radiator or just ran straight through.
Another fun idea was John Wetz's percolator/condenser. Exhaust steam went to a bubbler at the bottom of a small percolator column as tall as the radiator. The rising steam bubbles in the column, condensing into the water as they rose, drew water from the bottom of the radiator into the column. Hot water overflowed from the top of the column into the top of the radiator. Recovered water overflowed into the water tank. It was plumbed so that cylinder oil gravitated to the top of the bubbler column, in theory keeping oil out of the radiator and making it easy to recover (skimmer? oil absorber?). Natural circulation was maintained in the radiator and bubbler column with no pumps whatsoever.
I did some conceptual work on that one. Might work in a car, but would need "mods". Volume of water in circulator column would vary with steam flow -- the steam bubbles take time to condense, and meanwhile they take up space!
This is all treading close to my possibly patentable ideas, so my comments will now become cryptic. Remember that it is desireable to keep the air/steam and air/water temperature differential as high as possible for good heat transfer and a smaller/lighter/cheaper heat exchanger. The heavier the oil, the hotter the heat exchanger the better, to avoid clogging. Some oil seems to get through even the best oil separators -- except maybe a water/oil centrifuge like Peter Barrett uses. And don't forget the freezing problem. A water-filled radiator might benefit from automatic means to drain it to an insulated tank when standing or running very slow in freezing weather, and/or thermostatic air shutters like those used in some 1920s-'30s gas cars. In really cold weather, a bare water-filled radiator could freeze up PDQ at a stoplight or in slow-and-go traffic. Then again, water can't freeze if you keep it moving fast enough (but that takes horsepower).
I think it was Jim Crank who mentioned a trick tried by some Stanley owners. They ran the feedwater bypass through the condenser. This condensed all the steam for a while, but, unfortunately, resulted in the water tank overheating & pumps vapor-locking/pounding. By cooling the radiator with all that water, they ironically reduced the amount of heat the radiator was throwing away.
Tom: Very interesting, but weird! Wonder if it worked. Might have just been a paper patent (most are). Still, there is a good bit of potential energy to be recovered by condensing steam, with the right equipment. Cost-effectiveness & available space for equipment are serious issues with vacuum condensing in cars.
Peter</HTML>
Re: Efficient condensing
Posted by: Brian Drake (IP Logged)
Date: May 05, 2003 02:40AM
<HTML>I posted this site [www.thebrassworks.net] once before in a discussion about condensors and someone said that they were going to contact the manufacturer about using the design as a condensor, but as far as I know, they haven't posted anything about it. Considering some of the specs of the unit (it has 3.2 times the internal core surface area in direct contact with the cooling system liquid compared to a tube-and-fin radiator), it certainly sounds like it'd be worth looking into.</HTML>
Re: Efficient condensing
Posted by: Peter Brow (IP Logged)
Date: May 05, 2003 07:29AM
<HTML>Hi Brian,
At the SACA Discussion Group, Caleb posted the link to the Brassworks Heat Sponge page, and Jim Crank replied that based on his extensive experience, these "honeycomb" type radiators, as used in Dobles, tend to clog with oil and channel the steam, are a nightmare to repair and clean, and condense no more steam than a good tube and fin condenser of the same size. He also said that for a steam car, a honeycomb radiator's internal passages have to be bigger than those in a gas car honeycomb radiator, to avoid excessive backpressure. The discussion is toward the end of the "Waterman Control System" thread.
I suspect(?) that the clogging & lackluster condensing may be due to the use of heavy steam cylinder oil (which Doble himself once said was unsuitable for condensing steam cars due to condenser clogging), but the Heat Sponge is awfully expensive -- $1100 for a Ford T or A size, and Jim said $3500 or something for a Doble-sized condenser. Looks like it would be a bear to tool up for a cheaper(?) home-shop version too -- tricky dies, fixtures, and solder work.
Peter</HTML>
At the SACA Discussion Group, Caleb posted the link to the Brassworks Heat Sponge page, and Jim Crank replied that based on his extensive experience, these "honeycomb" type radiators, as used in Dobles, tend to clog with oil and channel the steam, are a nightmare to repair and clean, and condense no more steam than a good tube and fin condenser of the same size. He also said that for a steam car, a honeycomb radiator's internal passages have to be bigger than those in a gas car honeycomb radiator, to avoid excessive backpressure. The discussion is toward the end of the "Waterman Control System" thread.
I suspect(?) that the clogging & lackluster condensing may be due to the use of heavy steam cylinder oil (which Doble himself once said was unsuitable for condensing steam cars due to condenser clogging), but the Heat Sponge is awfully expensive -- $1100 for a Ford T or A size, and Jim said $3500 or something for a Doble-sized condenser. Looks like it would be a bear to tool up for a cheaper(?) home-shop version too -- tricky dies, fixtures, and solder work.
Peter</HTML>
Re: Efficient condensing
Posted by: George Nutz (IP Logged)
Date: May 05, 2003 10:47AM
<HTML> I called the company that makes the "heat sponge" last year and had quite a talk with them about our steam car parameters and the utility of the "heat sponge". They recommended one of there more conventional radiator cores(they make many custom replacements for old collectible cars), it did appear to them that the "heat sponge" would not be ideal for the parameters we were discussing.
George</HTML>
George</HTML>
Re: Efficient condensing
Posted by: Peter Heid (IP Logged)
Date: May 05, 2003 01:21PM
<HTML>Caleb,
The industrial power plants have found in recent years that it is worth it to pay a bit more for the larger air cooled condensers than to install pumps and spray condensers on installations under 250mW. Though larger in space, very compact designs have been developed and there is no reliability of pumps and seals to worry about. I like the idea of a water tank that is finned and has forced draft for extra cooling.
Peter,
You are correct that keeping the velocity high may cause higher exhaust pressures but if you are using a vacuum pump, very little change will be seen. If you are not exhausting to a vacuum, what percentage of 1000 psi is that pound or 2 that you increase the exhaust pressure compaired to the reduction in frontal area that it provides by increased efficiency ? The most modern natural and forced draft power plant condensers are finned.
Peter Heid</HTML>
The industrial power plants have found in recent years that it is worth it to pay a bit more for the larger air cooled condensers than to install pumps and spray condensers on installations under 250mW. Though larger in space, very compact designs have been developed and there is no reliability of pumps and seals to worry about. I like the idea of a water tank that is finned and has forced draft for extra cooling.
Peter,
You are correct that keeping the velocity high may cause higher exhaust pressures but if you are using a vacuum pump, very little change will be seen. If you are not exhausting to a vacuum, what percentage of 1000 psi is that pound or 2 that you increase the exhaust pressure compaired to the reduction in frontal area that it provides by increased efficiency ? The most modern natural and forced draft power plant condensers are finned.
Peter Heid</HTML>
Re: Efficient condensing
Posted by: Tom Ward (IP Logged)
Date: May 05, 2003 01:50PM
<HTML>Patent numbers 6,233,942 and 6,434,944 are assigned to Thermaldyne LLC. There is nothing in physics against the ideas claimed in these inventions but my guess is that it would only work over a narrow range of steam rates.</HTML>
Re: Efficient condensing
Posted by: Peter Brow (IP Logged)
Date: May 06, 2003 08:15AM
<HTML>Hi Peter,
Personally, I don't plan to try vacuum pumps or vacuum condensing. In a car, I think that the pump(s) and fan required would eat more horsepower than the vacuum would produce, under almost all conditions except high-speed cruising. Full-time vacuum condensing would probably require too large a condenser and/or fan to be practical in a standard car. With atmospheric condensing, it seems possible that reduced condenser size/drag could compensate for the increased exhaust backpressure needed to accomplish them. It also looks like one of those things that would be difficult to measure and calculate, maybe more difficult than the small gains/losses (in an optimized system) involved would justify.
Yes, finned heat exchangers are everywhere, including condensers. In stationary applications, the reduced cost (fewer tube joints) is probably crucial. Also, for an unfinned heat exchanger to compete with a finned type, much smaller tubing has to be used in the unfinned type. Standard practice is larger tubing, fins, and fewer tube joints. I have some ideas for making "smaller tube/more joints" type heat exchangers competitive in price. These involve new fabrication methods/materials; if those don't work out, then the finned type will remain more cost-effective. One thing to note is that finned tubing is more expensive per square foot of heat exchange area than unfinned.
I like your idea for a multi-pass condenser. Not sure if it would be practical to convert a std. radiator core to multi-pass design (depends on the available flowpath area), but your comments inspired a redesign of the "V-front" condenser type which I think is an improvement. Basically a stack of small V-front condensers, the same size/shape as a standard car radiator (~1" x 12" x 24"), plumbed together in series. Header size and tube numbers in each of the plumbed-together modules would be tuned to keep total steam/water flow path cross-section area constant from one end to another. I am thinking approximately the same flowpath area as the exhaust steam pipe from the engine, though a larger flowpath, maybe 2x that or more, might be necessary to compensate for the flow resistance imposed by all the small tubing and twists and turns.
However, if a fan, controls, etc were worked out so that exhaust steam never blows through, or only a small amount, then the flowpath area could be reduced toward the outlet as you suggested. I am currently designing for a system with no condenser fan.
Finned tank is one way to cool the tank; I came up with one idea where ram-air blows over a duct-encased water tank with a deeply corrugated wall. In freezing weather, the air inlet ports could be closed, partly or fully, by an automatic thermostatic shutter, and the duct would be insulated to prevent freezing when air shutter is completely closed.
Peter</HTML>
Personally, I don't plan to try vacuum pumps or vacuum condensing. In a car, I think that the pump(s) and fan required would eat more horsepower than the vacuum would produce, under almost all conditions except high-speed cruising. Full-time vacuum condensing would probably require too large a condenser and/or fan to be practical in a standard car. With atmospheric condensing, it seems possible that reduced condenser size/drag could compensate for the increased exhaust backpressure needed to accomplish them. It also looks like one of those things that would be difficult to measure and calculate, maybe more difficult than the small gains/losses (in an optimized system) involved would justify.
Yes, finned heat exchangers are everywhere, including condensers. In stationary applications, the reduced cost (fewer tube joints) is probably crucial. Also, for an unfinned heat exchanger to compete with a finned type, much smaller tubing has to be used in the unfinned type. Standard practice is larger tubing, fins, and fewer tube joints. I have some ideas for making "smaller tube/more joints" type heat exchangers competitive in price. These involve new fabrication methods/materials; if those don't work out, then the finned type will remain more cost-effective. One thing to note is that finned tubing is more expensive per square foot of heat exchange area than unfinned.
I like your idea for a multi-pass condenser. Not sure if it would be practical to convert a std. radiator core to multi-pass design (depends on the available flowpath area), but your comments inspired a redesign of the "V-front" condenser type which I think is an improvement. Basically a stack of small V-front condensers, the same size/shape as a standard car radiator (~1" x 12" x 24"), plumbed together in series. Header size and tube numbers in each of the plumbed-together modules would be tuned to keep total steam/water flow path cross-section area constant from one end to another. I am thinking approximately the same flowpath area as the exhaust steam pipe from the engine, though a larger flowpath, maybe 2x that or more, might be necessary to compensate for the flow resistance imposed by all the small tubing and twists and turns.
However, if a fan, controls, etc were worked out so that exhaust steam never blows through, or only a small amount, then the flowpath area could be reduced toward the outlet as you suggested. I am currently designing for a system with no condenser fan.
Finned tank is one way to cool the tank; I came up with one idea where ram-air blows over a duct-encased water tank with a deeply corrugated wall. In freezing weather, the air inlet ports could be closed, partly or fully, by an automatic thermostatic shutter, and the duct would be insulated to prevent freezing when air shutter is completely closed.
Peter</HTML>
Re: Efficient condensing
Posted by: Peter Brow (IP Logged)
Date: May 06, 2003 08:26AM
<HTML>Hi George,
Thanks for following up on this. I have found many times that a discussion with manufacturers of "interesting possibility" items for possible steam car use, leads to very different conclusions. Like the amazing metal-fiber flameholder matrix that turned out to cost an arm and a leg. It pays to check these things out more closely, though it is often disappointing.
One of the biggest problems with steam car development is the amount of equipment that cannot be commercially sourced, and has to be built from scratch -- "if you want it done right, do it yourself". Electric car guys, on the other hand, can buy virtually everything off the shelf.
For condensers, however, I think that pretty good results can be had with off the shelf gas car radiators and proper design.
Peter</HTML>
Thanks for following up on this. I have found many times that a discussion with manufacturers of "interesting possibility" items for possible steam car use, leads to very different conclusions. Like the amazing metal-fiber flameholder matrix that turned out to cost an arm and a leg. It pays to check these things out more closely, though it is often disappointing.
One of the biggest problems with steam car development is the amount of equipment that cannot be commercially sourced, and has to be built from scratch -- "if you want it done right, do it yourself". Electric car guys, on the other hand, can buy virtually everything off the shelf.
For condensers, however, I think that pretty good results can be had with off the shelf gas car radiators and proper design.
Peter</HTML>
Re: Efficient condensing
Posted by: Peter Heid (IP Logged)
Date: May 07, 2003 03:26PM
<HTML>Peter,
I agree with you about the vacuum pump. If you exhaust to vacuum or run a turbine, reduced back pressure makes a difference. On a condensing engine there is a point where the amount of exhaust pressure is correct for the system and this is related to the expansion ratio and the effectiveness of the feed water heater as well as the capacity of the condenser. Since the feed water temperature increases as the exhaust pressure increases, the net effect of the changing pressure is minimal on a 1000 psi engine that runs in condensing mode.
Peter Heid</HTML>
I agree with you about the vacuum pump. If you exhaust to vacuum or run a turbine, reduced back pressure makes a difference. On a condensing engine there is a point where the amount of exhaust pressure is correct for the system and this is related to the expansion ratio and the effectiveness of the feed water heater as well as the capacity of the condenser. Since the feed water temperature increases as the exhaust pressure increases, the net effect of the changing pressure is minimal on a 1000 psi engine that runs in condensing mode.
Peter Heid</HTML>
Re: Efficient condensing
Posted by: Caleb Ramsby (IP Logged)
Date: May 08, 2003 02:55AM
<HTML>Peter Heid,
One thing that might help the effectiveness of a finned water tank is a small radaitor, one from a heater core or an air conditioner inside the water tank. That way the steam would enter the radaitor and give it's heat to the water in the tank thus one wouldn't have to worry as much about steam being admited directly into the water tank and causing issues. For instance, if there were a vast amount of steam going into the tank directly it would most likely bubble up and start to fill the cavity above the water line. This would make it difficult to turn that steam back into water.
Also, if the tank were constructed out of a deeply corigated material which had fins soldered inside the deep grooves, with a close fitting shell around it. This would give the air a high velocity path in which it could extract a vast amount of the heat more effeciently.
There are two reasons that I am looking at jet condensors.
1. They are realitively imune to gravity. Except for drastica angles for the actual jet.
2. They utalize a fluid instead of a gas as the medium by which the heat is extracted.
It seems like a water tank heat extraction system would also have these two qualities. Yet another option. grin
I really don't car much about back pressure. I am planning on using a turbine system like on the Dobles on my future designs. Although right now I am looking at getting a casting kit for a small marine engine, making a copper tube flash boiler and making a fun little go-cart, which would be non condensing(smirk). I have not had any hand's on experience with steam as of yet, so I need to find that first pebble to step on.
Peter Brow,
Sound's like some good ideas. In reality any one who would be interisted enough in using or even buying a steam car won't mind filling up the water tank when they get fuel.
That being said, I think that with a rapid enough circulation of the cooling air and steam/water that the use of water could be cut to a minimum. However this would all be at a cost of power to drive the circulators. So there must be a balance with cost and water milage, this of course you are very aware.
I understand fully your concern about exposing too much of you ideas. Being an inventor my self I know how dangerous it can be to let your tounge(or finger in this case) slip for an instant can be.
Caleb Ramsby</HTML>
One thing that might help the effectiveness of a finned water tank is a small radaitor, one from a heater core or an air conditioner inside the water tank. That way the steam would enter the radaitor and give it's heat to the water in the tank thus one wouldn't have to worry as much about steam being admited directly into the water tank and causing issues. For instance, if there were a vast amount of steam going into the tank directly it would most likely bubble up and start to fill the cavity above the water line. This would make it difficult to turn that steam back into water.
Also, if the tank were constructed out of a deeply corigated material which had fins soldered inside the deep grooves, with a close fitting shell around it. This would give the air a high velocity path in which it could extract a vast amount of the heat more effeciently.
There are two reasons that I am looking at jet condensors.
1. They are realitively imune to gravity. Except for drastica angles for the actual jet.
2. They utalize a fluid instead of a gas as the medium by which the heat is extracted.
It seems like a water tank heat extraction system would also have these two qualities. Yet another option. grin
I really don't car much about back pressure. I am planning on using a turbine system like on the Dobles on my future designs. Although right now I am looking at getting a casting kit for a small marine engine, making a copper tube flash boiler and making a fun little go-cart, which would be non condensing(smirk). I have not had any hand's on experience with steam as of yet, so I need to find that first pebble to step on.
Peter Brow,
Sound's like some good ideas. In reality any one who would be interisted enough in using or even buying a steam car won't mind filling up the water tank when they get fuel.
That being said, I think that with a rapid enough circulation of the cooling air and steam/water that the use of water could be cut to a minimum. However this would all be at a cost of power to drive the circulators. So there must be a balance with cost and water milage, this of course you are very aware.
I understand fully your concern about exposing too much of you ideas. Being an inventor my self I know how dangerous it can be to let your tounge(or finger in this case) slip for an instant can be.
Caleb Ramsby</HTML>
Re: Efficient condensing
Posted by: Peter Heid (IP Logged)
Date: May 12, 2003 02:18PM
<HTML>Peter,
The tubes in the pictures I have seen of rotary boilers are u shaped and finned. I unique feature of the rotary condenser is that it can recompress the steam not condensed to feed it back to the boiler with some latent heat conserved. Saturated steam at atmospheric pressure has an enthalpy of 1150 BTU/Lb and that of water at 3000 psi is 802 BTU/Lb. The reduction of steam by compression to 3000 psi would leave 348 BTU's left to remove to complete the condensation. Compression condensation alone is not a likely scenario, but to compress the remainder of the steam after initial condensation has occurred could prove useful. In a system using 1200 PSI boiler pressure, the mixture of steam and water to be compression condensed would have to be about 40% steam by weight or less for complete condensation. The savings of latent heat might seem small but it is a free benefit of the space saving rotary condenser and the more saved, the smaller it gets. It would not pay to compress to less than the boiler pressure as the result would still have to be pumped to the boiler and too much heat would be wasted. To pump above boiler pressure would store the heat until the water is feed to the boiler, maybe even providing a means of regenreative braking.
Again, compression condensing is only a part of the total condensing system and it's use, rotary or piston, might be able to reduce the demands on system power and the size of the system.
Peter Heid</HTML>
The tubes in the pictures I have seen of rotary boilers are u shaped and finned. I unique feature of the rotary condenser is that it can recompress the steam not condensed to feed it back to the boiler with some latent heat conserved. Saturated steam at atmospheric pressure has an enthalpy of 1150 BTU/Lb and that of water at 3000 psi is 802 BTU/Lb. The reduction of steam by compression to 3000 psi would leave 348 BTU's left to remove to complete the condensation. Compression condensation alone is not a likely scenario, but to compress the remainder of the steam after initial condensation has occurred could prove useful. In a system using 1200 PSI boiler pressure, the mixture of steam and water to be compression condensed would have to be about 40% steam by weight or less for complete condensation. The savings of latent heat might seem small but it is a free benefit of the space saving rotary condenser and the more saved, the smaller it gets. It would not pay to compress to less than the boiler pressure as the result would still have to be pumped to the boiler and too much heat would be wasted. To pump above boiler pressure would store the heat until the water is feed to the boiler, maybe even providing a means of regenreative braking.
Again, compression condensing is only a part of the total condensing system and it's use, rotary or piston, might be able to reduce the demands on system power and the size of the system.
Peter Heid</HTML>
Re: Efficient condensing
Posted by: Peter Heid (IP Logged)
Date: May 23, 2003 04:29PM
<HTML>A very important point that is often over looked in condenser design is the insulating ability of the condensate as it drains from the wall of the condenser. It was found that a pipe carrying coolant would condense twice the steam if it were horizontal versus upright. The film of condensate grows as it flows down the surface and it soon falls from a horizontal tube where it must flow the length of the upright tube.
Peter Heid</HTML>
Peter Heid</HTML>
Re: Efficient condensing
Posted by: malik dildar awan (IP Logged)
Date: September 26, 2004 02:15PM
<HTML>we need a condesor steam turbine having following parameters
1)-Steam Turbine :condersor
2)-Company Name :Kawasaki
3)-Power :6MW
4)-Pressure :25 Kbar
If u have this kind of turbine then u can
contact me the following
phone#:0092-03334338743
Fax#:0092-041689940
E-mail : dildarmalik@hotmail.com
Thanks
Malik Dildar Awan</HTML>
1)-Steam Turbine :condersor
2)-Company Name :Kawasaki
3)-Power :6MW
4)-Pressure :25 Kbar
If u have this kind of turbine then u can
contact me the following
phone#:0092-03334338743
Fax#:0092-041689940
E-mail : dildarmalik@hotmail.com
Thanks
Malik Dildar Awan</HTML>
Re: Efficient condensing
Posted by: Jim Anneken (IP Logged)
Date: June 11, 2005 05:09PM
<HTML>Do you know anything more about those Thermaldyne patents?</HTML>
Re:surface steam condesor for steam power projects.
Posted by: p.k.shewale (IP Logged)
Date: October 24, 2005 09:42AM
<HTML>kindly highlight on
techanical specification.
selection.
water requairement,
standard& codes.
manufacturing,
testing menthods.
efficiency to be calculated.
performance parameters.
tube& other acceseriesw
thanks
P.K.SHEWALE
Dy Tech.Adviser
NFCSF(india)
Email- nfcsf@rediffmail.com</HTML>
techanical specification.
selection.
water requairement,
standard& codes.
manufacturing,
testing menthods.
efficiency to be calculated.
performance parameters.
tube& other acceseriesw
thanks
P.K.SHEWALE
Dy Tech.Adviser
NFCSF(india)
Email- nfcsf@rediffmail.com</HTML>
Re:surface steam condesor for steam power projects.
Posted by: Sanjay Bhoyar, Asstt. Engineer (IP Logged)
Date: November 27, 2005 08:39AM
<HTML>Please inform about the maximum limit of chlorine to be added in the cooling water to avoid pitting on stainless stee condenser tube. We are facing the problem of pitting on tube.
thanks,
with regards
Sanjay Bhoyar
MahaGenco, Mumbai, India.</HTML>
thanks,
with regards
Sanjay Bhoyar
MahaGenco, Mumbai, India.</HTML>
Re:surface steam condesor for steam power projects.
Posted by: Sanjay Bhoyar, Asstt. Engineer (IP Logged)
Date: November 27, 2005 08:40AM
<HTML>Please inform about the maximum limit of chlorine to be added in the cooling water to avoid pitting on stainless stee condenser tube. We are facing the problem of pitting on tube.
thanks,
with regards
Sanjay Bhoyar
MahaGenco, Mumbai, India.</HTML>
thanks,
with regards
Sanjay Bhoyar
MahaGenco, Mumbai, India.</HTML>
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