mathematicians and engineers - useful stuff
- Thread starter Shannow
- Start date
- Status
Pretty neat.
Thanks - some stuff you just come across as a kid and wonder.....
I liked this, too. Why use steam? Rig this with some fissile material: http://www.youtube.com/watch?v=dtbbeLe2CjM&feature=related
I liked this, too. Why use steam? Rig this with some fissile material: http://www.youtube.com/watch?v=dtbbeLe2CjM&feature=related
Yeah, that was my very next click off the vid I posted
(was trying to tell some precision toolmakers that it was possible to drill a square hole, and thought youtube might have the answer)...found it, and a whole lot of other neat stuff...I want stirling fan.
edit...it's been an interesting couple of years on the Stirling. People keep "discovering" ultra low temperature difference stirlings, realise that at work, we've got GWs of low grade heat (110F), and send "suggestions" that we (I) explore stirling cycle utilisation of the waste heat.
Nobody understands (nor will ever agree with me when they see a machine turning due to the heat of a human hand) that these things work on temperature difference, and the ones that they see on the internet are producing zero work.
I recall an old mech illustrated mag with a stirling powered mustang (FoMoCo research project). Great mileage, great performance, albeit a little laggy.
They've got a place, but not in Power Station cooling systems.
(was trying to tell some precision toolmakers that it was possible to drill a square hole, and thought youtube might have the answer)...found it, and a whole lot of other neat stuff...I want stirling fan.
edit...it's been an interesting couple of years on the Stirling. People keep "discovering" ultra low temperature difference stirlings, realise that at work, we've got GWs of low grade heat (110F), and send "suggestions" that we (I) explore stirling cycle utilisation of the waste heat.
Nobody understands (nor will ever agree with me when they see a machine turning due to the heat of a human hand) that these things work on temperature difference, and the ones that they see on the internet are producing zero work.
I recall an old mech illustrated mag with a stirling powered mustang (FoMoCo research project). Great mileage, great performance, albeit a little laggy.
They've got a place, but not in Power Station cooling systems.
Last edited:
Love your edit reason!
Just bloody say it - all spin and no torque!
Just bloody say it - all spin and no torque!
JHZR2
Staff member
we have an active program looking at them for bottoming cycles for high efficiency APU systems.
JMH
JMH
Fuel cell plus pruducer gas would be neat, if they can be made to last 20 years. You can still hook a stirling cycle to the waste heat, too.
Originally Posted By: Pablo
Just bloody say it - all spin and no torque!
Could this not be overcome with a large enough piston? I'm also not familiar with the typcial ambient in Shannow's local.
Just bloody say it - all spin and no torque!
Could this not be overcome with a large enough piston? I'm also not familiar with the typcial ambient in Shannow's local.
Tempest, think of it as a "ladder" to get the steam exit temperature of the turbine as low as possible.
Air is at x degrees wet bulb, that's the lowest point in the cycle. The cooling water (cooled by the air) can be no colder than the ambient wet bulb, it's always warmer. That water flows through the condensers, cooling the turbine exhaust steam. The condensed steam can be no colder than the cooling water, and as the heat must pass through a brass tube, will be hotter still.
If I put another step anywhere in the ladder, it distances the exhaust steam further from the ambient wet bulb temperature, reducing power station efficiency.
Plus the stirling cycle usually works on dry bulb temperatures, making placement of a stirling cycle in the ladder even worse.
Air is at x degrees wet bulb, that's the lowest point in the cycle. The cooling water (cooled by the air) can be no colder than the ambient wet bulb, it's always warmer. That water flows through the condensers, cooling the turbine exhaust steam. The condensed steam can be no colder than the cooling water, and as the heat must pass through a brass tube, will be hotter still.
If I put another step anywhere in the ladder, it distances the exhaust steam further from the ambient wet bulb temperature, reducing power station efficiency.
Plus the stirling cycle usually works on dry bulb temperatures, making placement of a stirling cycle in the ladder even worse.
http://www.canadiancleanpowercoalition.c...A2?OpenDocument
I found this while searching for what you are talking about.
It would seem that the waste heat right after the turbine would be useful (collected by heat exchanger) which would bleed off even more heat out of the steam/water and make condensation/cooling easier.
And why is water released out of the system or condensed? Why not just reuse the same water over and over which would already be hot?
There must be a reason for these things but it is not self evident to an outsider.
Tempest,
to get any work out of the exhaust steam needs a temperature difference. To use the waste heat will require a heat engine that of itself will have even lower grade waste heat than that which it is absorbing.
The absolute bottom temperature into which the waste heat (from your waste heat collection machine) discharges is the environment, so collecting and using it would add another "rung" to the ladder, increasing the turbine backpressure and reducing load and efficiency.
The turbine uses every last bit that it can, with the condenser operating at under 1psi absolute, meaning that the last three rows of blades are operating under a pressure difference, while still under vacuum.
The water is ultra pure, and condensed int he condenser for return to the boiler. The cooling water loop is where the evaporation to the environment takes place.
to get any work out of the exhaust steam needs a temperature difference. To use the waste heat will require a heat engine that of itself will have even lower grade waste heat than that which it is absorbing.
The absolute bottom temperature into which the waste heat (from your waste heat collection machine) discharges is the environment, so collecting and using it would add another "rung" to the ladder, increasing the turbine backpressure and reducing load and efficiency.
The turbine uses every last bit that it can, with the condenser operating at under 1psi absolute, meaning that the last three rows of blades are operating under a pressure difference, while still under vacuum.
The water is ultra pure, and condensed int he condenser for return to the boiler. The cooling water loop is where the evaporation to the environment takes place.
- Joined
- Sep 28, 2002
- Messages
- 39,798
Quote:
The cooling water loop is where the evaporation to the environment takes place.
This is where serious conservation could be realized. It would cost a bundle to soak up that heat in a useful manner ..but I sure wouldn't mind heated streets (or whatever) in the winter instead of the local nuke plant sending into the atmosphere.
The cooling water loop is where the evaporation to the environment takes place.
This is where serious conservation could be realized. It would cost a bundle to soak up that heat in a useful manner ..but I sure wouldn't mind heated streets (or whatever) in the winter instead of the local nuke plant sending into the atmosphere.
Ok, makes more sense. But why the condenser and cooling? It would seem that keeping everything hot, hot, hot would be the goal and pumping steam out of the back of the turbine immediately back into the boiler would be the most efficient way to keep things hot.
Nope, that would turn the system into a Brayton cycle (like the gas turbine). The energy used in compression would be horrific, efficiencies in the low 20s percentage wise.
By running it back to water, we can pump it up to 2800psi (using only about 20,000hp), and run mid to high 30s efficiencies.
By running it back to water, we can pump it up to 2800psi (using only about 20,000hp), and run mid to high 30s efficiencies.
The biggest efficiency losses are at the top end, with flame temperatures of 3000F, materials aren't available to run a normal steam cycle here. Energy is wasted diluting the heat down to a usable temperature.
If solid oxide fuel cells are perfected, you can turn the coal into producer gas, run it through the fuel cell at 65% efficiecy, with exhaust coming off at maybe 500F. The exhaust would go through a conventional steam cycle to ride the temperature down to ambient. Total cycle efficiency of such a system might be 70% (there are losses in gasification)
If solid oxide fuel cells are perfected, you can turn the coal into producer gas, run it through the fuel cell at 65% efficiecy, with exhaust coming off at maybe 500F. The exhaust would go through a conventional steam cycle to ride the temperature down to ambient. Total cycle efficiency of such a system might be 70% (there are losses in gasification)
Interesting. Thanks guys.
- Status
Similar threads
