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actually speaking, this thread should not be posted here. it is just calclulation method on combined cycle (thermodynamics).
I read an example on combined cycle recently. The calculation procedure considers the effect of fuel composition on thermal efficiency. when I did this calculation following the example, I found that the final efficiency would be greater than 100% if air surplus coefficient was large enough. Could anybody here tell me the reason?
p.s. I use trial and error method to estimate some parameters in the worksheet, but it is manually, can I do it automatically in mathcad?
thx
the mcd file is v11
May be this
http://twt.mpei.ac.ru/MCS/Worksheets/PTU/PGU-eng.xmcd
will be interecting for you.
See the screenshot of this Mathcad-Web-Sheet:
One example calculation of the gas mixture in the gas turbine of the Braiton thermal Cycle on Mathcad Server:
I think this answer will be more helpful to my confusion than your last answer. what confuses me is when I change the air surplus ratio to a higher value than what is given in this example, the efficiency based on the lower heating value of the fuel will exceed 100%. I m not sure whether it is right in this book.
I will study your example a few hours later . many thanks
I m studying this file now (http://twt.mpei.ac.ru/MCS/Worksheets/PTU/Vv-9eng.xmcd), up to now, I think maybe my fault lies on the pre-assumption of air coefficient alpha. I will redo my calculation following this example to see whether the error I mentioned above will appear again.
ps. I think that the section "humidity ratio of air " gives a wrong unit, should it be kg/kg?
Fan CG wrote:
ps. I think that the section "humidity ratio of air " gives a wrong unit, should it be kg/kg?
See properties of humid air as function of temperature and moisture g H2O/kg dry air:
http://twt.mpei.ru//MCS/Worksheets/rbtpp/eng/tab26.xmcd
The screenshot
yes, you are right. But by what I mean is as following:
I think maybe it is wrong