Author Topic: Talking Thermodynamics  (Read 105437 times)

Offline steam guy willy

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Re: Talking Thermodynamics
« Reply #810 on: April 02, 2018, 04:24:05 AM »
HI MJM , here is more of the text about cylinder sizes of compounds ...but nothing definitive though !!!

Offline MJM460

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Re: Talking Thermodynamics
« Reply #811 on: April 02, 2018, 12:52:30 PM »
Sorry to be absent without notice last night.  We had an international visitor for dinner.  Quite an interesting evening, but too tired after.  Always interesting to get a glimpse of a different culture.

Hi Willy, that is a complex procedure described in your book.  It appears to be a mixture of theoretical ideas and some empirical factors based on experiment.  Interesting that he mentions that square root for compounds, cube root for triples etc. and also talks about valve timing, those pressure ratio factors are recognised these days as giving the best efficiency.  Of course part of the complexity is that the formula seems to be calculating the required size for the hp cylinder for a required power output, not just the relative sizes of the cylinders. 

The point about the cut off for the hp cylinder determining the total power of the engine is clear, as it determines the steam consumption and hence the energy available.

The point about the lp cylinder cutoff is more interesting.  Earlier cutoff of the lp inlet decreases the power of the hp cylinder by increasing the back pressure, clearly.  But increases the power of the lp?  Well, if it increases the back pressure on the hp cylinder, it also means the inlet pressure of the lp is higher when expansion starts and expansion occurs over a greater volume change.   But if the cut off is later, the volume of steam into the lp is increased, but the pressure is lower, and the volume change remaining for further expansion is less.  So higher pressure, smaller volume, greater volume change for expansion, or lower pressure more volume, less volume change for expansion, which produces more power?

Well, as mentioned earlier in the article, the second cylinder admission timing does not affect the total power of the engine, that is determined by the hp inlet timing, but just redistributes the power between the cylinders.  So if the hp cylinder power is reduced, the lp power output must be increased.  So that is the answer, much easier to work it out that way. 

There is also mention of an exhaust pressure of 4 lb. , presumably psi, and clearly absolute.  If Mr Woolf expected such a good vacuum for the exhaust, his cylinder diameters would indicate quite a low boiler pressure.  It will be interesting to apply the formulae in those pages to the engine when you eventually discover the operating pressure (probably similar to the boiler operating pressure) and expected exhaust condition, and see how the power compares with the rating.

So two complex questions intertwined.  What size must the house cylinder be for a given power output?  And what are the proportions of the lp cylinder compared with the hp?  Very interesting that the author starts with the assumption that all the power is developed in the lp cylinder, then uses the overall absolute pressure ratio to size the hp cylinder.  I am not sure that I understand the procedure, but I assume that it worked, and those empirical constants were found by painstaking experiment that revealed or at least indirectly included the necessary efficiency factors.

Thanks for looking in,

MJM460
« Last Edit: April 02, 2018, 12:58:36 PM by MJM460 »
The more I learn, the more I find that I still have to learn!

Offline MJM460

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Re: Talking Thermodynamics
« Reply #812 on: April 03, 2018, 01:58:00 PM »
After thinking a little more about last nights topic, I realised that while the most efficient split between stages is equal pressure ratio as I stated before, to set the volume ratio for calculation of the cylinder diameters, I had implied, but not stated directly, that  we could use the equation
 P1 x V1= P2 x V2
which is of course the ideal gas law.  Had I thought a bit longer, I should have remembered that expansion of steam, a real gas, does not follow the ideal gas law, especially when we are talking about expansion of saturated steam.  It gets a little closer if there is a lot of superheat, but for the historical engines in particular, I am sure that we can assume it is saturated steam.  If not the ideal gas law, what should we use?  Obviously, our old friend, the steam tables!

If you look again at a copy of the steam tables, you will see that after the pressure and temperature columns, there are two columns for specific volume, which give the volume of a kg (or pound mass) of steam.  Then follow the energy columns, enthalpy and entropy that we have discussed often.  The steam tables contain our best knowledge of the properties of steam.

So I started again.  It is not nearly so simple, as not all pressures are listed.  If I assumed a supply pressure of 250 kPa, and exhaust 80 kPa, figures in the possible range based on Willy's measured piston dimensions, and took the square root of the pressure ratio, 1.76, as the intermediate pressure, then the intermediate pressure is 250 / 1.76 = 142 kPa.

This would have involved a lot of work interpolating the tables, so to simplify this, I took as the intermediate pressure 150 kPa which is directly tabulated.  This is a pressure ratio of 250 / 150 = 1.67.  The problem is to calculate using steam tables as the model, the volume ratio, and compare this with that value.

This involves first estimating the exhaust steam properties resulting from expansion of steam through that pressure range.  First we use the second law of thermodynamics which says for an ideal adiabatic engine, the entropy of the exhaust is the same as the entropy of the supply steam.  Using this entropy the dryness of the ideal engine exhaust is calculated as 0.97, and hence the enthalpy change can be calculated.  Assuming a real engine adiabatic efficiency, the real engine exhaust conditions can be calculated, (dryness 0.98) and from this comes the volume of exhaust steam and the volume ratio.  My calculation gave the actual volume ratio by steam tables as 1.56.

The volume ratio is proportional to the square of the piston diameter, so the ratio of diameters is the square root of that volume ratio.

So, if we assume the pressure ratio 1.67 is the same as the volume ratio, we get each cylinder diameter should be 1.29 times the previous one.

However, if we use the volume ratio from the steam tables we get the cylinder diameters should be 1.25 times the previous one, and the resulting lp cylinder diameter will be a little smaller than the one resulting from using the ideal gas law.

If we repeat the whole calculation for the expansion from the intermediate pressure to exhaust, I expect we will get a similar ratio, though I have not done the calculation.  Based on the calculations I have done, I suspect that any difference might only affect the third or fourth significant figure, if there is any difference at all.

Now, we have quite accurate steam tables, while Mr Woolf was probably reliant on the ones you posted from the book with the footnote about accuracy, but either way, we should start with diameters based on real volume ratios.  However, at the end of the day the difference is not large and that ratio will just alter the division of work between the cylinders.  The larger lp cylinder, in principal expands the steam a little more.  As even a compound engine does not fully expand the steam to the exhaust pressure, the effect of this is probably only a bit lower pressure in the cylinder immediately before the exhaust valve opens at the release point, and depending on the actual valve timing, might affect the efficiency a little, but the differences will not make the difference between producing adequate power and not.

I hope that gives a little more insight into how the calculations are done, and how the steam tables are used in calculations involving an engine.

Thanks for looking in,

MJM460
The more I learn, the more I find that I still have to learn!

Offline steam guy willy

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Re: Talking Thermodynamics
« Reply #813 on: April 03, 2018, 03:19:35 PM »
Hi MJM ,  thanks for all this , i have a book from 1829 about steam engines and i will trawl through it to see what their understanding was then of Thermodynamics,!! Also Will saturated steam ...superhearted steam and compressed air give you the same oomph value  at the same indicated pressure ? Is there a value for oomph btw !! Actually does wet steam just change into dry steam at a certain temp or can you have wet steam at a really high temp ?? Perhaps i should know this already ?? is there a phase change for extra super super heated steam or is that another silly question ??!
Willy

Offline MJM460

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Re: Talking Thermodynamics
« Reply #814 on: April 04, 2018, 12:07:01 PM »
Hi Willy, your research into the state of knowledge of thermodynamics at the time your engine was designed are most interesting.  I would be very surprised if someone such as Mr Woolf was not right up to date on the state of knowledge at the day.  He would have been limited by the accuracy of tables as we have mentioned before.  But I am sure his knowledge would have been extensive, and supported by a keen intuition, acute powers of observation and painstaking experiment.

Regarding your question on saturated steam, superheated steam and air at the same pressure, it is the one that tripped me up right at the beginning of this thread and I am quite embarrassed that I have not yet returned to provide the correct answer, and I am going to defer it for a day or two more, but this time I will return to it.  First your other questions.

It is difficult to describe exactly what happens at different pressures as we are all so familiar with a kettle on the stove, or a saucepan when the vapour space above the liquid surface is always at the relatively constant atmospheric pressure, and the composition of the gas in that vapour space is a variable concentration of air and water vapour.

When we say that water boils at 100 degrees, we are actually describing what happens when the equilibrium water vapour pressure of the water is the same as, or exceeds atmospheric pressure.  At this point, the water liquid starts changing to vapour and the resultant rapid volume expansion results in those bubbles we associate with boiling.  As we continue to supply heat to the boiling pot, more of the liquid changes to vapour, but the temperature and vapour pressure remain constant until the last bit of liquid has evaporated.   At this point, the vapour is called dry saturated steam.  Only when this point is reached can the temperature start to increase.  As soon as the temperature starts to rise, it is defined as superheated steam.  As the pot is now dry, the temperature of the pot is no longer cooled by the boiling water, so it also gets very hot.

I have skipped the description before the pot boils dry.  Those bubbles rising rapidly to the surface due to the huge density change tend to carry some liquid into the vapour space with the gas phase, that is the mist we are trying to describe when we use the word vapour instead of gas phase.  Dry saturated steam is when all the liquid in that mist has evaporated, then superheating begins.

Before boiling starts, in principle the water gas phase or vapour phase is in equilibrium with the liquid with the water vapour pressure shown in the steam tables.  In an open pot, or kettle with a leaky lid, atmospheric air mixes with the water vapour and the total pressure of water vapour plus air is constant at atmospheric pressure.  Below 100 degrees, that atmospheric pressure at the surface suppresses any vapour formation below the surface, so we have evaporation at the surface as the liquid absorbs heat, but not that vigorous bubble formation we know as boiling.  Because of that constant atmospheric pressure, the whole process occurs at constant pressure.  The water vapour just displaces some of the air from the kettle.

To conduct the experiment at any other pressure, we have to enclose the water in a sealed pressure vessel.  Of course, we could take our kettle to the moon, or the international space station, or perhaps even Jupiter to experience different pressure, but I assume you want me to stay practical.

We have previously discussed the issue of that air in the boiler, so this time let's assume we extracted the air with a vacuum pump, or have even just driven it out by raising steam, then shut the isolation valve and let the boiler cool down.  Now, the vapour space will contain only water vapour at the equilibrium pressure for the temperature, assuming that everything is happening slowly enough to ensure equilibrium.  At 15 deg C, the vapour pressure, so the boiler internal pressure, will be quite a good vacuum.

If we now heat that closed boiler, we will see the pressure tending to rise to stay in equilibrium with the liquid as the temperature rises.  If we have a pressure regulator so that the pressure is kept constant by blowing off excess water vapour, the water temperature will stay constant as heat is added at constant pressure until all the liquid has evaporated, at a temperature dependent on the pressure setting of that regulator.

The data for pressure temperature and all the other properties we have spoken about is contained in the steam tables, but is perhaps easier to understand on one of the diagrams.  I have previously posted the Temperature-Entropy diagram, and the Pressure-Enthalpy diagram and there are others.  All are characterised by that line which forms a loop, under which is the two phase region.  If you look closely, the temperature and pressure stay constant within that loop as energy is added.  Specific volume, enthalpy, and entropy change inside that loop as shown by the various sloping lines.  But pressure and temperature are both straight lines of constant temperature and pressure.  So under that loop, we have wet steam in equilibrium with the liquid.  The loop is the line that separates wet steam from liquid water or superheated steam.  If you add heat to superheated steam, it gets more superheated.  If you expand the steam to lower pressure it stays superheated.  You can even compress steam to a higher pressure and it stays still superheated.  The "super" in superheated does not mean anything spectacular, it just means heated above saturation, even if only a fraction of one degree.

At the very high pressure and temperature at the top of the loop there is no distinct phase change between the cooler end where we would call it liquid, and the higher energy side where it is clearly vapour.  There is just a continuous change of density.  Very hard to grasp.

The only other phases changes occur off the bottom of the diagram, where there are phase changes between liquid and solid (ice or snow) and also between solid and vapour.  There are also some more obscure phase changes between some different forms of solid, that I am not so familiar with.  Though I have experienced solid water (snow) changing directly to vapour without becoming water in between.  It is called sublimation.

Once the steam in our boiler is dry, further heat superheats the steam.  Or, if we run the pipe with the steam escaping through that pressure controller through our furnace, then superheating occurs outside the boiler.  The temperature rises quite quickly, and the heat transfer coefficient reduces markedly, so we have to be careful not to melt the boiler.  It no longer takes much heat to increase the temperature, we no longer have to deal with that latent heat.

If we choose to conduct the heating of the boiler at higher temperature, the whole process is much the same, and we have wet steam, saturated steam and liquid, and evaporation at constant temperature and pressure, right up over 370 deg C.  Try looking closely at one of those diagrams, and identifying the lines which define a constant value for some property.  Then follow those lines through the two phase area into the superheated area.

Above 374.14 degrees, there is no longer a distinct liquid phase.  This is called the critical temperature.  The corresponding pressure is 22,090 kPa, called the critical pressure, right at the very top of that loop that encloses the two phase region.  Modern power station boilers can operate above these conditions and are called supercritical boilers.  But I don't recommend a model at these conditions.  A tiny steam leak at those conditions is extremely dangerous and difficult to see until too late.  Up to 374 degrees, you can have wet steam at the appropriate pressure, but the pressure is well above atmospheric pressure.  Your electric boiler at 135 degrees, has liquid and wet steam in equilibrium at 135 degrees, so quite hot wet steam.

So not silly questions, just questions that highlight areas I have not explained well enough.  I hope this makes it a little clearer.  It feels like a lot of words, perhaps I should have stopped at one question for one post.  Please let me know where I have to try again.

Thanks everyone for looking following along,

MJM460
The more I learn, the more I find that I still have to learn!

Offline paul gough

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Re: Talking Thermodynamics
« Reply #815 on: April 04, 2018, 01:29:58 PM »
Willy, (hope I am not trespassing on your turf MJM), I was wondering if your 'phase change with super, super heated steam' was another way enquiring about the breakdown of steam to its constituent gases, oxygen and hydrogen. Well out of the model arena but still worth knowing about. The text from a reply to that issue is below. Regards Paul Gough.

2 years ago
Jack Denur
University of North Texas
An appreciable fraction of water will be decomposed into hydrogen and oxygen at a temperature high enough so that the Gibbs free energy change for the decomposition reaction equals zero. At 1 atmosphere pressure this will occur at around 3000K to 4000K. At higher pressures the required temperature will be higher, and at lower pressures the required temperature will be lower, because one mole and hence one volume of water vapor decomposes into 1 1/2 moles and hence 1 1/2 volumes of (hydrogen plus oxygen). So decomposition is favored by high temperature and low pressure and is inhibited by low temperature and high pressure.
The high temperature of steam boilers almost certainly cannot exceed 2000 degrees F which is about 1400K even for short intervals, and probably not 1000K on a sustained basis, as these are typical metallurgical limits. At these temperatures there is not much dissociation of water vapor. See, for example, Thermodynamics by Kenneth Wark, Jr. and Donald E. Richards, 6th edition, Table A-24 on p. 1066. (The material in Sects. 14-5 through14-7 on pp. 762-773 and Tables A-12 through A-15 on pp. 1047-1055 may also be helpful.)

Offline MJM460

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Re: Talking Thermodynamics
« Reply #816 on: April 05, 2018, 11:55:18 AM »
Hi Paul, not breaking in, contributions are very welcome, I would much prefer more discussion rather than question and answer.

First, I hope you did not get to badly hurt by cyclone Iris.  Always seems a bit anomalous that a cyclone should be called Iris.  After all, Iris, the messenger of Zeus is supposed to be one of the more pleasant characters of that lot.  However, I suppose Iris did not treat you as badly as the last one a couple of years ago.

I will comment on your suggestion about dissociation into hydrogen and oxygen.  This involves a chemical change as is not really classed as a phase change.  You started me thinking about what is the definition that separates the two, and I don't really know.  But it is normally more about the changes between solid, liquid and vapour through melting/solidification and evaporation/condensation, without chemical changes.

There is certainly a chapter about such chemical reactions in my thermodynamics book, and plenty about that Gibbs function, but it is not a chapter I am familiar with.  We need a Chemical Engineer to come in on that one.

In most chemical reactions, such as acid plus base giving salt plus water, there is just rearrangement of the reactants, but they are all in the products.

In water dissociation to give hydrogen plus oxygen, the constituent molecules of the products are different from the ones that you started with.  And that Gibbs function tell you you need to contribute a lot of energy, the reaction would much rather go the other way, where hydrogen plus oxygen combine to give out plenty of heat, making hydrogen a very clean fuel, as the combustion products are simply water (or steam as first produced).  But you no longer are talking about steam in dissociation.

However, even in dissociation, all the atoms present at the start are still present after.  Similarly, oil can be dissociated into carbon and hydrogen at sufficiently high temperature (and total lack of oxygen).  This happens in a furnace, and when the gas cools after the dissociation, all compounds of hydrogen and carbon are possible, and do form.  The conditions during cooling determine which compounds are most favoured, and the ones required are later separated out.  The process is generally called cracking.  The heat is such that the water cooled heat exchanger which cools the gases generates 1500 psi steam!  If you call that cool.  Well, I suppose kids today would call it cool.

If you really produce high pressure and temperature, the next step is to split the atom.  Then the original constituent atoms are no longer in the products.  And we all know that releases a huge amount of energy in the process that demolished our simplistic "conservation of mass" law of physics.  Fortunately the loss of mass is so very small that for all our normal modelling purposes, we can assume conservation of mass is close enough for practical purposes.

Other processes which I don't believe are classed as phase changes include precipitation and crystallisation, which both occur at much more moderate conditions.  These are more about solubility of a solid in a fluid.

So certainly another most interesting train of enquiry, but one I don't feel qualified to comment much more on.  Others are most welcome to comment, and many thanks for introducing the question.

I hope things dry out soon, but perhaps you at last have the start of a decent wet, after so many dry seasons.  Should be plenty of frogs to count if they weren't washed away.

MJM460
The more I learn, the more I find that I still have to learn!

Offline steam guy willy

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Re: Talking Thermodynamics
« Reply #817 on: April 06, 2018, 01:50:47 AM »
Hi MJM, et al  more brain food   thanks..Saw this in the engineer mag ...so as the pressure decreases the temp falls .....but if the cylinder does not have time to give up its heat then the pressure should stay the same ...but only intuitively of course !!! Also 750 pages from Dalby full of these diagrams and text and formulae !  unfortunately being three score years and ten  i may not get through it !!!! The Freelance is now a runner on air  ,so when it is closer to being finished  it will be interesting to see it run on steam !  Also the 1829 book that is available as a rather bad facsimile .....

Offline MJM460

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Re: Talking Thermodynamics
« Reply #818 on: April 06, 2018, 12:27:42 PM »
Hi Willy, a truly interesting account of early attempts to analyse engine operation in a more detailed way.  And all done without computers, calculators, or possibly even a slide rule.  I don't know when the slide rule was invented/developed.

As the piston moves down the power stroke, once the admission valve is closed, the volume of the trapped gas increases, so the pressure must fall.  Predicting how much it falls as the volume increases is behind the questions about the ideal gas law, and then real gas correlations such as the steam tables.

The reason the temperature falls is that the gas is doing work on the piston, so energy of the random motion of the gas molecules is being converted to mechanical energy in the form of work.  As the gas looses energy, you must either replace it in the form of heat or the gas must get cooler.  All of this is nothing to do with heat transfer through the cylinder walls.  With steam as our motive fluid, the gas is generally hotter than the cylinder wall, so in addition to the process of converting energy in the gas to work, there is also heat transfer taking place.  If we use air to drive our engines, the air also gets cooler as energy is converted, very cool if the air starts at atmospheric temperature, and the heat flow can be inwards to the gas.

The most efficient engine possible is the adiabatic engine, which you might remember means no heat transfer in or out.  You might approach the no heat transfer condition if you constructed a cylinder out of some sort of perfect insulating material.  But a real engine out of a metallic material absorbs heat from the steam in addition to the heat being lost by conversion to work.  This reduces the engine efficiency.  Those early pioneers were trying to understand how much heat is lost as a step towards understanding how that heat loss  affects engine performance.  Of course the cylinder walls are in contact with an expanding gas with reducing temperature alternated with high temperature incoming steam for the next cycle.

Now that is a complex problem in three dimensional unsteady heat transfer.  The heat transfer book has a chapter for two dimensional unsteady heat transfer.  They then write out the partial differential equations in three dimensions, called the Navier Stokes equations.  When I was a student, that was as far as it went and the lecture ended with an off hand comment about all that remained to be done was to solve those equations.  With a modern computer and a very sophisticated finite element program, these equations can now be solved, probably still with some approximations, but in those days, no way.

The approximations used are a reasonable attempt, and I don't know how accurate the answer.  Sometimes a simple assumption gives you most of the answer, and a huge amount of extra complexity  only gives a little improvement in accuracy.  But it looks like they are assuming the temperature is constant at each level in the cylinder, though I could have skipped through it too quickly.  The issue is complicated by storage of heat in the cylinder walls, so at any point on the wall, the temperature rises as heat is received from the gas then returns some of this heat as the gas further cools.  Lagging the cylinder helps lift the average temperature, and keeping the walls thin reduces the amount of heat stored, but on the other hand, a bit more metal acts a bit like a thermal flywheel, reducing the amount of temperature fluctuation, so helping the walls reach a steady temperature.

And of course, heat travels along the cylinder as well as radially.  But while the problem is very complex, someone has to make a start somewhere, and those guys did an amazing job with the resources at hand.  And each step forward contributed to our knowledge today.

It sounds like you have a lot of interesting reading ahead, but make sure it does not get in the way of making more of your wonderful engines.

Thanks everyone for following along,

MJM460
The more I learn, the more I find that I still have to learn!

Offline MJM460

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Re: Talking Thermodynamics
« Reply #819 on: April 07, 2018, 12:39:28 PM »
Not much to say today.  Willy asked the other day about steam vs air, a question I have intended to get back to since my first effort at the very start of this thread.  I have at last made a start.  I am happy with the steam calculation but have to complete the calculations for air.

I have had another 300 km drive today, so all calculations need careful checking.  It is too early yet to say if I have a better answer than before, but more work on it tomorrow will, I hope, produce some results.

With less heavy reading to do, perhaps everyone will have more time to make swarf.

Have a great day,

MJM460
The more I learn, the more I find that I still have to learn!

Offline steam guy willy

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Re: Talking Thermodynamics
« Reply #820 on: April 07, 2018, 02:47:15 PM »
Hi MJM, so when did they know all there was to know about thermodynamics so there was no more improvements to steam engines ??....basically apart from the Corliss configuration nothing has really changed since the 1850's....?

Offline Admiral_dk

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Re: Talking Thermodynamics
« Reply #821 on: April 07, 2018, 06:46:10 PM »
Quote
basically apart from the Corliss configuration nothing has really changed since the 1850's....

I'm not sure that I can agree on this unless you will insist that it's only a steam engine if it has pistons - there has been a great increase in efficiency with turbines ....

Offline MJM460

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Re: Talking Thermodynamics
« Reply #822 on: April 08, 2018, 01:23:09 PM »
Hi Willy, you are starting to sound like that director of the US Patents office who was reported to have recommended to the government that the office be closed down because everything that could be invented had been.  Or the one who commented on Alexander Bell's telephone that no thinking man could believe you could send sound down a wire, and in any case, even if you could, why would you want to.

Technology tends to move in steps and stairs.  I don't know what development of reciprocating steam engines followed the Corliss, but I suspect you would need a more recent text book to be sure.  There have certainly been developments in welding and steel making technology that enable operation at higher temperatures and pressures.  But as Admiral DK says, thermodynamics also covers steam turbines, and gas turbines.  I am sure that Sir Frank Whittles invention of the gas turbine was more recent than the 1850's.

I mentioned early in this thread that even the best power station sized plants were just meeting 50% efficiency at the time I retired.  Since then, GE have announced two power plants which exceeded 60%.  They were combined cycle plants, that is gas turbines with steam generators using the exhaust heat to raise steam and drive steam turbines to generate more power.  All up output exceeded the 60%, even if it was only during initial operations with everything new and clean.  I don't know what other conditions had to be met for the test run.  But certainly not possible with the knowledge available in the 1850's.  Sometimes development is something obvious like a new valve gear, other times it is a solution to an equation that is not so visible but opens the door to further explorations.

Hi Admiral DK, good to see you dropping in again.  I am with you entirely, thermodynamics is not limited to reciprocating steam engines.  Apart from steam turbines and gas turbines, I would expect thermodynamics to have played an important part in space exploration, both in the rocket motors and the heat shields.  And also in modern large scale solar.  All developments since the 1850's.

Computers now allow us to solve equations not dreamed of before, so also facilitate the continuing development.  While human beings are thinking, development will continue.

I have made a bit more progress on the calculations for air.  Steam was easy, but the superheated steam case required some interpolation of tables due to a less than ideal assumed steam pressure as the basis, but all done now, so a bit more checking then some results.

Thanks for looking in,

MJM460
The more I learn, the more I find that I still have to learn!

Offline Admiral_dk

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Re: Talking Thermodynamics
« Reply #823 on: April 08, 2018, 09:20:33 PM »
Quote
Hi Admiral DK, good to see you dropping in again.

Oh - I haven't left .... I normally read every post in all forums here every day ...!!!

In the beginning (2013 ?) I only followed the subjects I really found (most-) interesting, but I discovered that even the most uninteresting subjects (in my book) might contain some very interesting tidbits of information and some are just plain fun to read (Jo vs. Jason springs to mind  :stir: ).

I will have to admit that I do not read all post in this thread word for word as some of them are a bit more esoteric on the subject than what tickles my curiosity - and then there are some I can't help comment  8)

Best wishes

Per

Offline steam guy willy

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Re: Talking Thermodynamics
« Reply #824 on: April 08, 2018, 11:01:01 PM »
Hi MJM, sorry i was being a bit selfish with the 1850 comment !! However this is just my main areas of interest...of course there are modern turbines that have quite a range of systems in built..Delaval etc etc etc It is just the basic concept of cylinder, piston ,crosshead etc through to the steam pipe that has remained the same. Even the brand new Tornado loco is basically just this ?? and how efficient is this engine ?? not taking into account digging the coal and transporting it to the engine. Perhaps there are figures available ??
willy