Talking Thermodynamics

[MJM460]

Hi Willy, it is time all those computer gurus at Apple and Microsoft got their acts together and included a "send package" button in their operating systems, so you could share that quiche with the forum members.  I am sure it would improve the discussion no end!  And we could send chocolates on big days and so on.  It would be quite popular, and might provide the incentive for many who have old, slow computers to update.

When it comes to cooling, I suggest the number of corners is not very relevant, it is mostly about areas.  So the area of the top, area of the base, and total area of the side walls each have a separate heat transfer coefficient for natural convection, and the heat transfer area, area and temperature difference are the factors determining the amount of heat transfer and hence the cooling rate.

When it comes to your motor bike, the cooling fins form an extended surface area.  The increased area however involves heat transfer along the length of the fins, so the temperature in contact with the air is not uniform.  The calculation methods I have seen account for this with an efficiency factor for the fins.  The square fins have a bit more surface area for cooling than uniform circular fins would have, even though the area in the corners would have slightly less efficiency than the area mid way along the sides, due to being a greater distance from the cylinder.  So I would expect the square fins would provide slightly more cooling than round ones with a diameter equal to the distance across the flats of the square, but slightly less than circular fins with diameter equal to the distance across the corners of the squares.

It is hard to know whether the difference is really enough to be important, and hence part of the design intent, or whether the square fins are there purely for appearance.

I did notice your post about the paint colour experiment the other day, sorry I omitted to mention it.  It seems like a really good way to further investigate the effect of the surface temperature on radiation heat transfer from the sun.  I assume you will collect some similar size tins and paint one each colour.  You could use the tins as cookie cutters in a piece of styrofoam for insulating lids.  And leave a small hole in each for your temperature probe.

However, as always, radiation is not the only heat transfer going on.  As the sun heats your tins, the atmospheric air will start some cooling by convection.  But I would expect there would be a difference in temperature after some time in the sun.  Given the small difference Derek's car temperature measurements, the difference might be quite small, but it will be very interesting to find out.  It is only carefully controlled experiments like you are suggesting that really confirm the answers.  Waiting for results with interest.

Hi Derek, how much the car heats up due to the glass effect is a quite different effect on heating the car internal space, so I expect would not change your measured temperature difference with colour.  So well done on thinking of doing those measurements and posting the results.  You have clearly shown that the "white cars are cooler" belief that is so widespread is not totally urban myth, but the effect is not really so great that you would buy a car of a colour you really disliked. 

The other colour understanding that most of us subscribe to, is that black and grey cars are quite difficult to see in the distance on the road in poor light conditions.  They are certainly difficult to see as I have found out once again in driving about 600 km in grey sky's and light rain this last weekend.  But I am not sure that the lighter colours are really any easier to see.  Travelling with headlights on in the day time clearly makes much more difference.  So all around, to keep the car cool when parked in the sun, and to be visible to other drivers on the road, it would seem that while colour makes a difference, reflector blankets and headlights have a much more significant effect on your comfort and safety.  But it still mystifies me why black and grey seem so popular these days.

By the way, which car did you eventually buy?  Or is it still under consideration?  And how much weight did you give to the temperature difference?

Thanks for looking in,

MJM460

[MJM460]

Displacement lubricators-

I have been thinking a bit about displacement lubricators, particularly with regard to that steam cylinder oil.  I have seen various comments about how well they work, but nothing really definitive except that they have been used forever, and surely they would have been replaced long ago if engines were showing signs of poor lubrication.  I have thought about whether it is possible to measure how much oil they actually deliver, and how long a given quantity of oil in the lubricator might last.  I am confident that they work ok, as there is a small amount of oil makes it through with  the condensate that drains from the exhaust separator, but it's time to try and quantify it.

It occurred to me that it might be might be worth looking at how much steam a small displacement lubricator might condense.  The recent discussions on radiation heat transfer reminded me of the calculations I did earlier for small locomotive fire boxes.  As with the fire boxes, the lubricator looses heat by convection and radiation.  In addition, the body of the lubricator and oil start at ambient temperature, and are heated by steam on the oil surface, the heat taken by the lubricator  body and oil comes from condensing steam.   As heat is lost by the steam, it condenses, and the water displaces an equal volume of oil into the steam pipe, and hence to the engine.  I include a valve at the lubricator inlet, which I keep closed until the cylinder has warmed up and the engine is running, then I open the valve so that some steam is admitted to the lubricator.  I have attached a picture of one of my lubricators in case my description is unclear.

I measured up one of my lubricators, (they all seem to depart from the drawing dimensions!) and calculated the approximate surface area, and volume.  I assumed the body heated up to about 80 degrees, cool enough to be condensing some steam but hot enough to burn the finger.

Heating the body and oil took slightly more than convection losses for a 10 minute run, about 1000 J for each, about double what was lost by radiation in that 10 minutes.  Ten minutes is about the normal steaming time for my small boilers and in any case can easily be multiplied up for a longer run.  So convection plus radiation plus initial heating of the lubricator body and oil added up to enough heat to produce about 1 ml of condensate, with an additional 0.65 ml each 10 minutes.

So how do these calculations relate to the performance.  First, I opened the lubricator and removed the drain valve at the bottom.  As I suspected, full of sticky emulsion from when I was using engine oil instead of steam cylinder oil.  I have given it plenty of time to drain, and washed it with a good squirt of WD40.  Then I let a bit more WD40 soak overnight in the the reservoir, drained it again and now it looks quite clean.  I left it open overnight to let any remaining WD40 film evaporate.

I normally fill the lubricator with an eye dropper.  It has to be filled slowly as the oil goes slowly past the valve stem so blocks the exiting air.  A point to try and improve in the next design.  It is hard to measure the oil in, as there seems nearly as much oil clinging to the outside of the dropper as inside, but the calculated capacity is about 3 ml.  So the next step is to run the engine again, remember to measure the lubricator body temperature and steaming time, and see how much water will drain out afterwards.

It will be interesting to see if the measured water drained after the run is anywhere near the calculated numbers.  So stay tuned.

Thanks for looking in,

MJM460


Oh dear, the photo is too large to load up.  I will return shortly with it.

[MJM460]

You can see the lubricator with the steam valve at the top and drain valve.  Perhaps this time the size will be ok.

MJM460

[steam guy willy]

Hi MJM, Does the lubricator need a drain cap ? i don't have one on mine so should i install one ? Does it eventually fill with water as oil floats on water ?  Also i am drinking hot tea and my glasses have steamed up!!  so why don't your eyeballs steam up ?? another silly question perhaps ??  Nice looking engine btw.......On the colour experiment ,i was thinking of just using brass rod with a hole drilled into it the same size as the probe. I will then just paint the tubes the different colours and have them screws onto a piece of wood. This will be better than using water as the amount may evaporate at different rates and so introduce discrepancies ??  would this wrk  OK ??
Willy

[derekwarner]

When we think about how these displacement lubricator function, the one point sadly lacking in manufacturers directions, is the preference to fill the lubricator until the oil level is lapping the lubricator internal cross tube with the drilled orifice...this is where the eye droppers MJM mentions ...either underfill or overfill

So fully agree that eye-droppers are best left to eye drop fluid, however it is rather easy to modify standard hypodermic needles to be used to carefully & visually see how much oil is being injected [the modification firstly dispense with the ''sharp'', then inset a 2.0 mm OD brass tube & epoxy cement into the plastic spout of the syringe body .....the stoppers are shortened toothpicks.......[so far {in 12 months?} the oil has not migrated out of the timber]

The advantage of the quartz glass tubed displacement lubricator is the visual confirmation of condensate to oil remaining or used during a run...[as shown in the second snap]

Some suggest a fixed orifice version wastes too much oil....I understand this, however the most inexpensive commodity in a build is surely the cost of oil...the bottom needle valve drain allows easy pressurised blow down via the tube to the de-olier.....again the visual advantage is clear

The bright light green is ISO 060..lubrication oil [sewing machine oil], the dark olive green is ISO 460 steam oil...so impossible to mix up

Derek

Edit...........

don't be confused, in the second snap, it is the morning sunlight streaming thru the ISO460 pea soup that changes the appearance of a lighter oil [the attributes of ..opulence and translucent are probably more appropriate terms]

[MJM460]

Hi Willy, whether you have a drain valve at the bottom or not depends largely on how you normally operate your steam engine.  As you suggest, the steam condenses in the lubricator, and the condensed water sinks to the bottom of the reservoir, and in the process lifts the oil, so that some leaks out into the steam pipe.  Eventually, all the oil is gone, and the lubricator is full of water.  If you have a syringe with a small enough tube, you could extract the water through the filler plug when the system has stopped and cooled down.  If you have a feed pump and want to keep the engine running all day, you may need to drain the lubricator from the bottom, depending on how well the shutoff valve works.  With a drain valve at the bottom, as Derek says, the steam pressure can help push all the water out, especially of you want to drain it to the exhaust separator.  I just loosen the screw in valve at the bottom with the filler plug removed, and the water runs out easily enough, then when the oil starts coming through it becomes quite slow, in distinct drops, so it is easy to close the valve and retain the remaining oil for next time.

My lubricator has only one entrance when in operation, a 1 mm diameter hole through to the steam passage.  When I open the valve, which closes off that hole, steam pressurises the lubricator, but there is no flow through, so the steam just condenses in that stationary volume as it loses heat.  That heat loss determines how much steam condenses.  The condensate that forms in the reservoir and sinking to the bottom is the only way the oil can be lifted so it can leak into the steam passage.  I deliberately say "leak" rather than "flow", as it feels like a better description of high viscosity oil through a 1 mm diameter passage, with no real driving pressure.  Of course, the oil viscosity reduces rapidly with temperature, so it is not nearly so viscous where it is in contact with steam, but never-the-less, to describe it as "flow" feels like an exaggeration.

It is also complex to analyse when the system is first started.  I probably overfill the reservoir.  I suppose that when I screw in the plug, a little oil is forced into the steam pipe even with the valve closed, or is there a little air bubble somewhere?  I keep the valve closed until the cylinder has heated and the engine starts, but then the steam can only condense against the surface of the oil in that 1 mm diameter passage.  It is hard to see how too much oil can move, but as there is always a little oil in the condensate that drains from the exhaust separator, clearly some gets through, and it seems to be enough.  I guess that surface tension and capillary effects are important both at the very start, and continuing after a little oil has been used.

Your glasses are quite cool (in every sense of the word!), especially in winter, and compared with the hot steamy vapour rising off your tea as you drink it.  Hence the "steaming up".  And the fogging is because the condensation occurs in tiny droplets which scatter the light.  It is only when those drops coalesce into a continuous film, that it becomes transparent.  However, not only are your eyes close to body temperature, so much warmer than your glasses, but they always have a film of moisture over them to lubricate your eyelids.  Any excess or deficiency is fixed every time you blink, which is generally more often than most people think.  And the film is quite transparent, so no problem to your eyes.

With your colour experiment, I suspect you could do it either way, but you have raised a good point, you would need to carefully measure the same quantity into each tin if you go the water way.  But with the same quantity in each, and styrofoam lids, I don't think evaporation will be much of an issue in the temperature range you will be seeing.  Water has the advantage of better contact with the probe, so might give more consistent measurement.  However if all the holes in the brass are the same depth, and the probe is a reasonable fit, you will soon see if your readings are reasonably consistent.

Hi Derek, I really like that glass tube lubricator.  As you say, you can clearly see how much water you have.  Do you find it stays clear? Or does some emulsion eventually make it hard to see through?  It probably also looses heat more slowly than the copper/brass variety, so further slowing the oil rate, which would help if lubricators generally over supply oil.  Of course, once you blow down the condensate, you have to top up the oil to that ideal level for the lubrication to continue without a break while the condensate is replaced.

Your modified syringes are a great idea for precision oiling and for getting into inaccessible spots.  Eye droppers also work, but mine only hold 1 ml, so not good for larger volumes, like Meths in the fuel tank, though for a top up to get a precise quantity they are ideal.  For the cylinder oil, I find that they probably have at least 0.5 ml on the outside, sticking like honey, so I doubt that they are at all accurate for this.

I never cease to be impressed by the detailed work you do on the piping on your model.  Particularly the neat bend around the lubricator valve stem.

Have you made any more progress on your paddle wheel drive train?

Not much time for an engine test today, besides, I want to install a tray under the boiler and gas tank to see how much that helps the gas pressure.  It was only 12 in the shop today!  I have some sheet brass, so I am inclined to say hang the expense, and use the brass.   I don't see a flood of oil from the exhaust separator, so I tend to agree with you that over oiling is not a significant issue.  Also, the oil that does appear appears gradually throughout the run, I don't see a big blob arriving in a short period.  But comments by other people about lubricators supplying too much or too little oil make me even more interested to see what I can demonstrate, so we all have a little more information when such issues are discussed.

Thanks for looking in,

MJM460

[derekwarner]

I look at the sequence of events here with a slightly different view

If the lubricator is filled with a heavy Grade Steam/cylinder oil with a virtual ZERO air gap and the engine steam regulator is set to ZERO flow, when the boiler steam stop valve is opened, [the assumed air pocket in the tube to the lubricator], we get a shot of steam which partially pressurises and condenses with the entrapped pocket of air

When the engine steam regulator is opened, this allows a flow of steam....which at the same time provides the same back pressure into the lubricator as is offered by the steam regulator

So all things being equal, a volume of steam admitted into the lubricator [under the uniform steam pressure between the boiler steam stop valve and the steam regulator] condenses and the volume of the condensate displaces the same fluid volume of steam lubrication oil into the steam tube to the steam regulator & hence to power the engine

So ISO 460 steam/cylinder oil at 20 degrees C and atmospheric pressure is yes like pea soup, however when elevated to operating temperatures of say 80 degrees C and 1 Bar...is more like water in it's fluid characteristic's

It is in fact an open loop hydraulic fluid system.... there are no leaks...[only onto the drip tray] with the spent fluid [exhaust steam] going to the de-oiler with the fatty/water content trapped & the mist of clean steam to atmosphere

Derek
 

[steam guy willy]

HI MJM, So, my lubricator gets filled each time i start the boiler up so the oil must be going somewhere ?!! I just assume it works !!  and my eye's do go a bit misty when i watch sad films ..and look at some of the amazing work going on in this forum.  Also saw this in a book from 1836 talking about Naphtha....,apparently the Russians actually drank it !!!!
Willy
PS.... just looked on the web and found this !!!! no trade descriptions act in those days !!

[MJM460]

Hi Derek, I really appreciate your constructive engagement in the topic, it helps the thread enormously.  I don't really think there is much difference in what we are saying.  If I understand correctly, you have two valves, a boiler stop valve, and an engine regulator.  I assume your lubricator is always open the the steam line between the boiler and the engine.

My system is slightly different, you could say less complete.  I also have two valves, and one is the boiler stop valve, but in my case the other is in the top of the lubricator, so when it is shut, there is no contact between the steam and the oil in the lubricator.  My simple steam plants do not have a separate engine regulator.  A governor with a throttle plate will be an interesting challenge for a future project.

I think both systems are quite common, as some of the simple lubricator designs I have seen for small engines simply have the steam line passing completely through the lubricator body, with a small hole in the tube connecting the steam line to the oil space.  However many of the commercial regulators, and various other design drawings have a needle valve separating the lubricator oil space from the steam line.  I have seen it suggested that this needle valve enables regulation of the flow of steam, however, I suspect it is effectively only a stop valve, either open or closed.  Leaving it closed until the engine is running means there is no possibility of "a slug of condensate" entering the lubricator during the warm up, displacing a larger volume of oil when the cylinder drains might be open so the oil might not even contribute to the engine lubrication.  When I open the valve, there is hot, relatively dry steam flowing past in the steam line.  But it may not be a big issue.

Once the engine is running, I open the lubricator valve, and that "shot of steam" pressurises to lubricator to steam pressure.  But assuming the lubricator is cold, or perhaps just warm due to conduction from the steam pipe, the steam starts condensing on the cold metal.  Now we know that steam condenses very quickly on a cold surface, quick enough that condensation on the cylinder walls of a running engine reduces its efficiency, but depending on the actual pressure in the steam line, when the steam condenses the volume of condensate is of the order of 1/1000 of the volume of steam.  New steam keeps coming in to replace the lost volume and condensate increases the volume of liquid in the reservoir, and slowly makes its way to the bottom, so lifting the oil level.

I like your suggestion that the oil should only be filled to the level of the cross bar, leaving an air bubble trapped in the top of the lubricator, and meaning that oil should start to be transferred quite quickly and no problems with seating the filler plug against a liquid full space.

Now I see two mysteries, first the reservoir is a blind enclosure with one tiny hole connecting it to the steam pipe.  With steam flowing in to replace the volume lost by condensing, how does the air get out through the same opening?  Similarly for the oil.  Though I have seen, in close study of pump and compressor seals, that even with a pressure drop by the seal fluid in one direction, gas or liquid does migrate the opposite direction if velocities are not sufficient to keep everything in its place.  And there will be surface tension effects that will help the oil travel, but counterintuitive to have flow in both directions at the same time, especially with a hole only 1mm in diameter.

I don't really know how to calculate the volume flow in that initial period while the steam condenses on the reservoir walls, but once the metal is up to temperature, further heat transfer is limited by convection and radiation to the surrounding environment.  My calculations give an idea of heat transfer by convection and radiation, hence mass flow through that 1 mm passage.  I may even be able to make an estimate of the resulting steam velocity.

Now, I have been out enjoying my granddaughters school play this evening, so I won't try and keep tracking all those zeros tonight.  But I will try it tomorrow, and see if the calculation yields a plausible result.

However, it is clear that the heat loss ensures a continuing controlled condensation in the reservoir that ensures the oil level is continually lifted, so is able to flow out and be carried through to the engine in a controlled manner.

Oh, and the matter of leakage, I totally agree, no leaks, even into the drip tray.  Unfortunately I can't say the same for the engine, I can see some liquid gaskets in my life in the near future.  When I was referring to leakage, I was referring to the oil escaping from the reservoir into the steam line.  The quantity is very small, and to call it flow feels like an exaggeration.  It might be better to call it seepage, or perhaps just call it a very small flow.

More to those little lubricators than meets the eye.

Hi Willy, I agree totally with your logic, if you are able to top up the oil every run, it must be going somewhere and the only way available is to the steam pipe where it is carried on to the engine.  And they definitely seem to work when running on steam, though a different principal is required if you are running on air.  But you did not mention the water.  If you don't empty it, I have to wonder where the water goes, assuming that the steam connection to the lubricator is near the top, similar to mine in the picture.  I know that when mine has cooled down, I remove the plug and open the drain at the bottom, and get quite a bit of water draining out.  I just have not previously made any attempt to measure the quantity.  I would expect that if you don't have a drain valve, you would need to use a syringe to suck it out through the top, or detach the reservoir and tip it out.

I think most of us know of circumstances which make the eyes misty, when there is too much moisture for blinking to adequately remove.  Much more than the quantity which might get past your glasses when you have a hot drink.  But eventually blinking eyelids catch up, perhaps with the help of a handkerchief, and you can see again.

Drinking naphtha?  I certainly wouldn't recommend it.  But poisoning the customers was never a consideration when those snake oil salesmen had a potion to sell.  I believe that in your country, and possibly others, publicans would increase their profits by watering down the beer, then restoring the "kick" by adding arsenic, a totally natural product as my wife would say!  We have a bit of a problem with people sniffing petrol, and over time it really scrambles their brains.  We even have odourless petrol available in some areas to discourage it.  Others choose glue with similar results.  I would expect drinking naphtha would be similarly damaging, with a very high probability of inducing a chemical pneumonia if any gets into the lungs.  It is tragic when people feel so bad, that they have so little respect for the wonders and health of their own brain.  Mind you if some of those remedies involved external application it might sometimes help, though I have no real knowledge to prove it.  However, some of the components are carcinogenic, so unlikely to lead to a happy result in the long term, however it is used.  I would not be in a hurry to try it.  But getting off topic, perhaps we had better return to thermodynamics.

Thanks for following along,

MJM460

[derekwarner]

 'With steam flowing in to replace the volume lost by condensing, how does the air get out through the same opening?  Similarly for the oil'

 ...following is my understanding of the sequence of events that occur at the steam startup all hidden away within the sealed lubricator ...[although I am always happy and prepared to listen to other thoughts]

The design of [my] displacement lubricator [Winfried Niggle Germany] provides the ~~ 0.7 diameter hole in the steam transfer tube [4 OD x 2 ID] with the hole drilled in the horizontal plane....so as such, when the boiler steam stop valve is opened, each component down stream is pressurised 

With oil prefilled to lap the lower diameter of the steam transfer tube ....the hole is ~~ 1.7 mm above the level of the oil leaving a relatively small volume airspace ......so the steam enters the lubricator bowl via the 0.7 diameter hole, this then continues to condense as bubbles of water that naturally sink to the bottom and carries on until the oil fluid surface meets the 0.7 diameter hole ...

With the oil being virtually incompressible, it overcomes the compressibility of the entrapped 'air and steam' and oil is injected into the steam path to the regulator. This explains how the entrapped air is forced into solution with the oil and is quickly purged as steam oil with air bubbles

So it would appear reasonable to be careful with the oil level especially with cast iron cylinders as under filling the lubricator will then take a longer time period before condensate can displace the oil

With brass cylinders & pistons with the relatively low pressures we are using, a number of knowledgeable modellers suggest the lubricity of LP steam  itself is sufficient for the requirement

I certainly do not discount this, however visualise hardened steel pivot pins between the piston the connecting rods in the internals of my engine......

My understanding of lubricators with needle valves fitted is the valve is an adjustable orifice to adjust or limit the amount of oil that is displaced or thus injected into the steam tube passage. [I have not seen any commercially manufactured lubricators fitted with a valve to limit steam flow]

Derek

[MJM460]

Oh, the joys of a sewered society!  Of course we would not want to be without it, but when my neighbour rang the doorbell at 7 am this morning, waking me from a sound sleep, I knew we were in for a bad day.  We had sewage flowing down the side of the house, under the fence to his yard, where the grade diverted it under his house.  He was woken by the smell from his floating heater ducts!

Our area had the sewage installed about 1918 despite material shortages, so not real great.  Our forefathers had the wisdom to know that plumbers have saved many more lives than doctors, and invested in a system with plenty of allowance for flooding rain and the foreseeable population increase.  But our city is now over 4,000,000, an unimaginable number back then.  And modern economists tell us it is cheaper to increase housing density than start a new city.  And that is after they have chewed up all that flood provision.  I don't think they allow for the cost of what follows.

The main sewer blocked near us, and the vagaries of varying land slope and changes of elevation along the street mean our vents are the first low point above the blockage.  So we were greeted by far too much information about what all the neighbours to the west and slightly higher elevation were putting down the sewer.  We had a gusher for over three hours before it was stemmed.   But in the grand scheme of things, after the heat of the moment has passed, I guess that even that is not too bad.  But you don't want the pictures!

We know the procedure well.  We know who to ring, how to prove it was their responsibility, not ours, as if we could ever produce the quantity, no matter how unwell.  It used to happen every five years, now down to two.  The sewer main needs relining, they don't even dig it up these days, but every few years all the contracts are relet, and nobody has any long term memory.  Except us!

So, many phone calls later, showing countless people where everything is, written reports, more phone calls later and so on, we now have the flow going the right direction, our sink will drain, and only the cleanup, by the supply authority of course, to be done tomorrow, and the replacement of the neighbours heating ducts, again!  At least there is no doubt when the problem is this magnitude.  A small issue is much harder as bureaucracy seems always to try and blame the householder, rather than take responsibility.  I assume the same everywhere.

So now I can sit and read a little more thermodynamics for light relief.

Hi Derek, I guess we could toss that back and forth for quite a while, but I am sure you will agree that typing it all gets a bit tedious.  Perhaps over a drink sometime.  But I did manage to carry my calculations a bit further. 

When steam is initially introduced to the lubricator, it condenses against the cooler metal body and oil, heating it all up.  This happens quite quickly but I don't have an estimate for the time this process takes.  However, once the lubricator body is up to a steady temperature, I can estimate the heat loss to the atmosphere from convection and radiation, and this determines the amount of steam that can continue to condense while the engine runs.  With the boiler stop valve fully open (or absent), I assume the steam pipe pressure is close enough to boiler pressure.  Regardless of superheat (though would require a little additional heat loss for condensing) steam is saturated in the top of the lubricator where the condensing is happening, so the steam tables tell me the latent heat, but also the specific volume of the steam.  So using the heat loss calculation, I can calculate the mass and volume of steam entering the lubricator. (It's more like an estimate really, as while the calculations are OK, they rely on a lot of input numbers that can only be approximate).  Then, using the diameter of the passage between the lubricator and the steam pipe, I can calculate the velocity in that 1 mm diameter passage.

Now the biggest issue in all calculations of this type, especially when numbers are very large or very small, is keeping track of the correct order of magnitude.  Perhaps it comes from all those years using a slide rule.  I find the best procedure is to very strictly stick to the fundamental units for the unit system being used.  This is  SI as for all my calculations, and the fundamental units are are kg, meters and seconds.  While the numbers are very small for this particular example, these units are used in the steam tables, so there are no conversions of units required.  Rather than keeping track of large number of zeros, I select scientific format for the numbers with two or three digits, and even an iPad can neatly display the numbers and keep track of the powers of ten.  Unfortunately, the iPad does not offer engineering format, which always has exponents divisible by three, so fits in better with prefixes like mili or micro or nano etc.

So what was the result?  I know most don't like too much calculation, so I will just provide the summary.  After the initial warm up of the metal lubricator body and oil, I calculated a total heat loss by conduction and radiation of 2.4 W.  For steam, I assumed about 300 kPa, as something representative of the likely pressures. The specific volume is about 0.6 m³/kg. And the quantity of steam condensed is about 0.64 grams in ten minutes, quickly converted to 1.2 X 10^-6kg/s.

A little maths and the steam velocity in that 1 mm diameter passage is 0.8 m/s.  A 0.7 mm hole would result in a velocity about 30% higher.  Not even difficult, using a spreadsheet.  When I manage some measured temperatures from the next test run, I can update the figures and let the apple recalculate.  Operating pressure ranging from unloaded runs to around 50 psig would make this velocity range from about 0.4 m/s to about 1.6 m/s. 

Now, if my memory is recalling anything about dry gas seals on a pump, the required velocity across the seal faces has to be somewhat higher than 0.8 m/s to prevent liquid migration across the seal faces against the imposed pressure drop.  Counterintuitive, I know, but I had the opportunity, and privilege to talk to experts on this topic in that previous life, and it was quite memorable, even if I can no longer recall the precise figures.   But I am sorry to say that calculating the oil flow rate for that situation is beyond me.

A better approach for oil flow estimates will come from operating the lubricator, timing how long the lubricator is in operating and measuring the water drained at the end of the run.  This is the same as the volume of oil consumed, with the only issue being allowing for the condensed water for that initial metal warming.

I think I have already mentioned that there is more to those displacement lubricators than it first appears.  I hope this little excursion into the detail is interesting.

Thanks for following along.

MJM460

[Gas_mantle]

Oh, the joys of a sewered society!  Of course we would not want to be without it, but when my neighbour rang the doorbell at 7 am this morning, waking me from a sound sleep, I knew we were in for a bad day.  We had sewage flowing down the side of the house, under the fence to his yard, where the grade diverted it under his house.  He was woken by the smell from his floating heater ducts!

Maybe they should have built a proper pumping station like the Victorians would have done ;-)

http://www.dailymail.co.uk/news/article-3742144/New-museum-opens-inside-Victorian-pumping-station-dubbed-Cistern-Chapel-originally-built-combat-Great-Stink-1858.html

[derekwarner]

I didn't realise your little city had multiplied itself to the dizzy number of 4M persons 

Well that was certainly a sordid sewerage tail MJM.......not quiet sure why your you neighbour had heating elements near a sewer line?

However only the Scott's would take a disused sewage sludge steam boat tanker and turn it into a Tourist attraction    it gets even worse...one of the tanks is now a carpenters workshop   

https://www.google.com.au/url?sa=i&source=images&cd=&ved=2ahUKEwiswNPairbbAhUGi7wKHQtAC0QQjhx6BAgBEAM&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FSS_Shieldhall&psig=AOvVaw0uhg2Uf6RTaGHsvwy47KzV&ust=1528066831582648

[MJM460]

Hi Gas Mantle, good to hear from you again.  I have been quietly following your progress with that vertical boiler.  I am still hoping that you will eventually try and measure how much steam it produces in a given time.  Probably easier on gas than coal.

They did build a pumping station, just like in Victorian times.  In fact, we are in the state if Victoria, and it was built quite a long time ago, so it was actually Victorian times in many ways.  And it is still operating last I heard.   And I have even been on a tour.  Needless to say, everything you see is pristine clean.  Our problems were not related to pumping problems, but a collector piping blockage.  I believe those baby wipes that you just "throw away thoughtfully" and "wet strength" tissues are high on the list of probable culprits, even in quite large pipes.

Hi Derek, your comment on Melbourne's population prompted me to check the latest figures.  Seems I missed a few folks, the official 2017 figure is 4.8 million.  Accuracy like convection calculations!

The neighbours heating ducts are not really so near the sewer, after all the flow all came from the vents on our property.  But the neighbour is slightly down hill, and the flow ran under the fence, then under his house.  The puzzling bit is why the insurance company did not make sure the ducts were tied up to the floor beams, clear of ground level last time they replaced them.

You laugh at that tourist attraction, but ours is the feature attraction at the children's science museum.  Nothing like letting the kids play there.  But they are learning more real science than they can find in a book shop.

I meant to comment on the water lubrication of brass pistons.  I don't think all those Mamod, and other similar models we had when we were young, had lubricators at all.  At least, mine did not.  And the drop of oil on the port face before a run or even during, probably did not help the piston much.  So moisture from that wet steam was probably all they had.  Of course, some experienced a lot of wear, and I have seen magazine articles by people who have restored them.  But many probably lasted by not being overused.  Somebody may have information on what they do on small  steam launches, where they reuse the water as boiler feed.  They don't really want oil in the boiler, so do they use piston rings that are happy with water lubrication, or just have really good oil separators?

The big clean up was completed today, but took most of the day.  However I have managed to cut a brass plate and put it under the boiler, squeezed between the boiler feet and the base board by the boiler hold down bolts.  The boiler feet are soldered to the boiler shell so probably get quite hot.  I also made a clamp around the gas tank which has an extension tab that bolts down to the boiler tray plate, which I hope will transfer enough heat to the gas tank to keep the pressure up a bit.  Should get to test it this week some time.

Thanks for looking in,

MJM460

[steam guy willy]

Hi MJM, I have looked at my displacement lubricator and it is different to others... I took the design from one of my books but cannot find the actual drawing !...... also saw this post on our forum about "growing" cast iron ?? !! also one of the other posts is featuring a triple engine but has quite a few valves to block off the steam input to the individual cylinders.. I think this was to reduce the steam consumption with differing loads. the chap making these valves is doing a great job ,I forget the actual name of the posts , but was wondering how the pistons get lubricated with out the steam entering the cylinders ??
willy