GAS-L: Re: [energyresources] Steam Calculations

["Kermit Schlansker" <kssustain@provide.net>]

       According to an article In "Machine Design" which I read years ago,
Bill Lear's bus engine was a single stage vapor turbine. Such a device can
not be used at high enough temperatures to compete with internal combustion.
The fuel economy was terrible. I believe that his goal was lower pollution
but he forgot about efficiency.
       The Stirling engine is a hot air cycle which works at extremely high
temperatures and is theoretically very efficient. However, like the fuel
cell, it has been around a long time but as far as I know, has never been
put into production. If it really were a good device, then it would greatly
reduce the need for making liquid fuels from coal and wood.
      The steam engine is not competitive with internal combustion if you
have pure gaseous or liquid fuels. However, if you are using solar, wood,
coal, or waste heat then it is useful. Steam engines could  use the exhaust
heat of any high temperature engine to further improve efficiency. The vapor
turbine could also be used in this manner. The disadvantages of steam are
lower efficiency, the need for boilers and condensers, and the fact that the
low output temperatures are less useful for space or industrial heating.
       The furnace for space heating is a totally inefficient device.
Universal cogeneration,  comanufacturing, or the combustion driven heat pump
would save a lot of energy..

                         Kermit Schlansker


From: Ron Patterson <readyourdarwin@yahoo.com>
To: energyresources@yahoogroups.com <energyresources@yahoogroups.com>
Date: Friday, October 12, 2001 1:20 PM
Subject: Re: [energyresources] Steam Calculations


>Kermit, not being an engineer in the field of
>thermodynamics, I could not make heads or tailes out
>of your post. But I would like to ask you one
>question.
>
>As I am sure you know, Lear, of Lear Jet fame, spent
>millions trying to build a small steam engine. He put
>all his resources, along with his entire staff of
>engineers into this endevour, which consumed the last
>several years of his life. In the end, he threw in the
>towel, he, and his engineers, decided it was
>impossible.
>
>My question is this, do you now think it is possible,
>and if so, what do we know now that Lear and all his
>engineers could never figure out? I don't know what a
>Sterling Engine is. Is this the engine that Lear tried
>to build but failed?
>
>Ron Patterson
>
>--- Kermit Schlansker <kssustain@provide.net> wrote:
>>                   Steam Calculations
>>
>> We know that there is considerable energy to be
>> recovered in the gas cooling from biomass
>> gasification, from engine cooling, and from engine
>> exhaust. My very approximate calculations are
>> intended to show that steam engines are not obsolete
>> but can be used as auxiliaries to an internal
>> combustion engine and biomass gasification to get
>> increased efficiency. I feel that steam engines are
>> very valuable in solar energy systems, gasification
>> systems or in general wherever there is waste heat.
>> We need small steam engines in production at a low
>> price. My feelings about Stirling engines is that
>> their advantages might have been magnified by
>> wishful thinking. Some of the specs that I have seen
>> indicated very high temp and pressure operation.
>> This could be trouble.
>>
>> The Carnot equation which defines the limits of
>> efficiency of conversion of heat to mechanical
>> energy is (T hot absolute-T cold absolute)/T hot
>> absolute
>>
>> In Farenheit units, abs 0=-460 So this equation
>> becomes (T hot F-T cold F)/(T hot F+460)
>>
>> For a steam system with 212 deg boiler and 80deg
>> condenser Carnot efficiency=
>>
>> (212- 80)/(212+460) =132/672=.196 or 19.6%
>>
>> For 350 deg boiler and 80 deg condenser
>> E=270/810=.33 or 33% efficiency
>>
>> For 1000 deg boiler and 80 deg condenser
>> E=920/1460=63%
>>
>> From practice we know that a good steam system is
>> only about 40% efficient instead of 63%. Therefore
>> we assume that Carnot limits must be multiplied by
>> about .7 to get practical.
>>
>> 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
>> =.33*.7*19.6=4.5%
>>
>> For exhaust having an averaged temp of 350 degrees
>> steam output=.33*.33*.7=7.6%
>>
>> total gain from coolant and exhaust steam =12.1%
>>
>> total output from IC, coolant, and exhaust=33+12
>> =45.%
>>
>> For a conventional biomass gasification system with
>> no steam, efficiency of conversion to gas=70%. If
>> engine efficiency=33% then overall
>> efficiency=23.1%.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=6.9% efficient
>>
>> If we assume that the engine with steam has a 45.1%
>> eff with a 70% heat input then that eff=31.57
>>
>> Total efficiency of gasification to power with steam
>> auxiliary would be 31.57+6.9=38.47%. By using
>> auxiliary steam, conversion efficiency can be
>> improved from 23% to 38.47%
>>
>> Kermit Schlansker PE
>>
>>
>
>
>=====
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assumes that the laws of nature which govern all other species of plants and
animals were negated for man by the God of Genesis. Man is saved by the
formula, ''X will provide'', where ''X'' may be God, Providence, or Science.
>Garrett Hardin, "The Feast of Malthus".
>
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