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| Gasification Archive for October 2001 |
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| 37 messages, last added Tue Nov 26 17:18:03 2002 |
[Date Index][Thread Index]
No Subject
For an engine 33% goes to mechanical energy, 33% into coolant, and 33% =
into exhaust.
If one assumes a coolant temp of 212 and an exhaust temp of 350 and a =
practical efficiency of 70% of Carnot efficiency then coolant to steam =
=3D.33*.7*19.6=3D4.5%
For exhaust having an averaged temp of 350 degrees steam =
output=3D.33*.33*.7=3D7.6%=20
total gain from coolant and exhaust steam =3D12.1%=20
total output from IC, coolant, and exhaust=3D33+12 =3D45.%=20
For a conventional biomass gasification system with no steam, efficiency =
of conversion to gas=3D70%. If engine efficiency=3D33% then overall =
efficiency=3D23.1%.You can do better with a triple expansion steam =
engine.
If we assume a 350 deg temp for cooling of hot gases. Steam energy from =
biomass gasification gas cooling is .3*.7*.33=3D6.9% efficient
If we assume that the engine with steam has a 45.1% eff with a 70% heat =
input then that eff=3D31.57
Total efficiency of gasification to power with steam auxiliary would be =
31.57+6.9=3D38.47%. By using auxiliary steam, conversion efficiency can =
be improved from 23% to 38.47%=20
Kermit Schlansker PE
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<P> &nbs=
p; =20
Steam Calculations</P>
<P>We know that there is considerable energy to be recovered in the gas =
cooling=20
from biomass gasification, from engine cooling, and from engine exhaust. =
My very=20
approximate calculations are intended to show that steam engines are not =
obsolete but can be used as auxiliaries to an internal combustion engine =
and=20
biomass gasification to get increased efficiency. I feel that steam =
engines are=20
very valuable in solar energy systems, gasification systems or in =
general=20
wherever there is waste heat. We need small steam engines in production =
at a low=20
price. My feelings about Stirling engines is that their advantages might =
have=20
been magnified by wishful thinking. Some of the specs that I have seen =
indicated=20
very high temp and pressure operation. This could be trouble.</P>
<P>The Carnot equation which defines the limits of efficiency of =
conversion of=20
heat to mechanical energy is (T hot absolute-T cold absolute)/T hot =
absolute</P>
<P>In Farenheit units, abs 0=3D-460 So this equation becomes (T hot F-T =
cold F)/(T=20
hot F+460) </P>
<P>For a steam system with 212 deg boiler and 80deg condenser Carnot=20
efficiency=3D</P>
<P>(212- 80)/(212+460) =3D132/672=3D.196 or 19.6%</P>
<P>For 350 deg boiler and 80 deg condenser E=3D270/810=3D.33 or 33% =
efficiency </P>
<P>For 1000 deg boiler and 80 deg condenser E=3D920/1460=3D63% </P>
<P>From practice we know that a good steam system is only about 40% =
efficient=20
instead of 63%. Therefore we assume that Carnot limits must be =
multiplied by=20
about .7 to get practical.</P>
<P>For an engine 33% goes to mechanical energy, 33% into coolant, and =
33% into=20
exhaust.</P>
<P>If one assumes a coolant temp of 212 and an exhaust temp of 350 and a =
practical efficiency of 70% of Carnot efficiency then coolant to steam=20
=3D.33*.7*19.6=3D4.5%</P>
<P>For exhaust having an averaged temp of 350 degrees steam=20
output=3D.33*.33*.7=3D7.6% </P>
<P>total gain from coolant and exhaust steam =3D12.1% </P>
<P>total output from IC, coolant, and exhaust=3D33+12 =3D45.% </P>
<P>For a conventional biomass gasification system with no steam, =
efficiency of=20
conversion to gas=3D70%. If engine efficiency=3D33% then overall=20
efficiency=3D23.1%.You can do better with a triple expansion steam =
engine.</P>
<P>If we assume a 350 deg temp for cooling of hot gases. Steam energy =
from=20
biomass gasification gas cooling is .3*.7*.33=3D6.9% efficient</P>
<P>If we assume that the engine with steam has a 45.1% eff with a 70% =
heat input=20
then that eff=3D31.57</P>
<P>Total efficiency of gasification to power with steam auxiliary would =
be=20
31.57+6.9=3D38.47%. By using auxiliary steam, conversion efficiency can =
be=20
improved from 23% to 38.47% </P>
<P>Kermit Schlansker PE</P></DIV></BODY></HTML>
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