How to assign thermodynamic properties after splitting two phase into gas and liquid

[mad fridgie]

This quote stands!!

For the quote to stand we have to make a start, and this is the start. Jumping straight into the process will only ask many more questions, than can be quickly answered.

Peter was is your opinion! what would be the properties of a seperated streams of flashed liquid.

[mad fridgie]

I thinks it is time to bring Carters Widget into the open (against my peers advice, you know who are !!! lol)

[desA]

Would the flow regime relate directly to the exit of the expansion valve and its effects reduce if the bell (liquid vapour seperator) is a reduced velocity and impegement type. (basically allowing the heavy liquid to fall to the bottom and the lighter vapour to rise to the top)

Basically separating & then forcing flow in a certain pattern. An interesting idea. Perhaps pipe diameter would play a useful part here?

Keep the liquid on the bottom part, with vapour sliding along the top part. There will be a critical vapour velocity at which surface waves will occur in the liquid - trying to re-introduce another more complicated flow pattern.

Keep below the critical velocity, or alter pipe diameter & we should be able to convey both separately. Thereafter, we can then treat Chef's problem from a thermodynamic point of view.

[desA]

Ok, Chef. I've been re-reading your post.

Would you want to re-combine the separate flows, or keep them separate? If separate, then the thermo should be a little easier to resolve, I'd think. If re-combined, then flow regime will impact the final solution.

Can I suggest that we introduce some diagrams, then superimpose their thermodynamic states on the log(p)-h diagram?

If the two fluids remain at same pressure, then their properties ?will? lie on the same pressure line on the log(p)-h diagram - no? Their individual states should surely then move to liquid sat line & vapour sat lines respectively?

Interesting.

[Peter_1]

To be honest, I explain this each year to my students. I take the fully expanded point on the refrigerant cycle where evaporation starts.
For me, the enthalpy of the gas and the liquid are there the same. Enthalpy can be found in charts and saturated tables (ST)
I then took the specific volume in the chart because you can't find those in the ST. For gas I took the value of both 'v' value on both sides of the saturated and multiplied this with the 'x' value, the lather found again in the chart.
For the liquid same but multiplying with 1-x.

DesA, isn't this a little bit the same conversation we once had via PM about something I didn't understand in the Dossat book Principles of Refrigeration?

I'm struggling also with the fact that a chart is a chart for a standstill refrigerant. But in a real life cycle, the refrigerant is flowing and then Bernouilli is coming around the corner. Then my brain starts to twist because I never studied thermodynamics really into its deep aspects and therefore, I can't combine a static situation with a flowing situation.

The compression process.. I had to study this the last in 1999 when I took my ATPL exams and we there had a complete course about jet engines, going really very deep into the theoretical side of a jet. I still remember I struggled with this one but anyhow, I made this one. There were +/- 130 out of 180 who had to go back a second time. I still have my exams about this course somewhere and if I re-read those now, it's far, so far away.

Chef, perhaps we should ask this once to real authorities in this field like Cengel , Boles, White,...

[desA]

DesA, isn't this a little bit the same conversation we once had via PM about something I didn't understand in the Dossat book Principles of Refrigeration?

Good memory, Peter.

Chef, perhaps we should ask this once to real authorities in this field like Cengel , Boles, White,...

Would be lovely to invite them.

[chillerman2006]

I thinks it is time to bring Carters Widget into the open (against my peers advice, you know who are !!! lol)

Definately NOT !

Apart of the thread I do fully Understand

Leave the widget in the can, We all are very curious obviously, but if this all works, curiousity will not kill the cat, but make him into a Fat Cat, if he has the ability to produce. And there are probaly many viewers to this site, some I suspect only viewing for this exact reason !

A few Red Herring's would not hurt though would they !

[install monkey]

im not keen on herrings or most other fishies,i bet mad fridgies kids hate him when he drops hints of christmas prezzies in march!-if he's put time and money into such an item,he should test it,refine it then sell it and hopefully reap the rewards-so dont tell me what it is-keep the cat in the bag(it will die of starvation or asphixiation)-but can i buy a beta version of it and can i have a service manual for it and a few passwords to interogate it-not the dead cat!!!

[chillerman2006]

the fact that a chart is a chart for a standstill refrigerant. But in a real life cycle, the refrigerant is flowing and then Bernouilli is coming around the corner.

we should ask this to real authorities in this field like Cengel , Boles, White,...

Evening Peter

Heisenberg's Uncertainty Principle, is also rearing his head (for me in more ways than one)

momentum = mass x velocity, the refrigerant has momentum p = mv, where 'p' is momentum, 'm' is mass and 'v' is velocity.

'Mass' can be considered as the amount of 'stuff' an object is made of. 'Velocity' is the component of the particle's speed acting in a specific, defined direction.

Basically the constant changing flow in a system, makes so many changes to your calculations (If I am understanding correctly so far) ??????

Evening Install,

Even though this is way beyond the premiership & way way beyond you & I, to start to understand the basics here of what is being said will be so valuable to us in the field, when the product is adventually released.

My miss-understandings are there with corrections from 'MF' & 'Chef', which should illiminate miss-conceptions for others.

A thread to be followed by everyone who wishes to understand how/what/why this product works

R's chillerman

[chillerman2006]

This quote stands!!

"It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt."

These are both very true, But

If everyone is afraid to pipe up & make a fool of themselves, then none of us lesser knowledgible members will ever understand the concept & will not understand the system fully that we will be working on once it is released,

I'm quite happy to be branded, as long as I am learning, I win !

Would you not agree Sir ????

[simon@parker]

"It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt

better to ask a stupid question than do a stupid thing because if you dont know its not stupid have told all the apprentices i have worked with that works as well

[Peter_1]

"It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt."

These are both very true, But

If everyone is afraid to pipe up & make a fool of themselves, then none of us lesser knowledgible members will ever understand the concept & will not understand the system fully that we will be working on once it is released,
I'm quite happy to be branded, as long as I am learning, I win ! Would you not agree Sir ????

Agree for 100%. Hey, not Sir but Peter. PM me once your private email, I think there's a misunderstanding and I want to explain something.

[Peter_1]

I wrote this afternoon Professor Boles. Will see if and what the man has to say us.

[mad fridgie]

Definately NOT !

Apart of the thread I do fully Understand

Leave the widget in the can, We all are very curious obviously, but if this all works, curiousity will not kill the cat, but make him into a Fat Cat, if he has the ability to produce. And there are probaly many viewers to this site, some I suspect only viewing for this exact reason !

A few Red Herring's would not hurt though would they !

The fact is I can not get repeatable test results, so does the actual widget work or not.
I also technical limitations. and do not have the right set of quals to quantify the theory a proven principle. I now long have the finacial resources to employ those with the skills to take this to a theoretical and practical level. Plus after ecent expericiences, even when I developed other technologies it is just near impossible to sell the technology for any value, (I also buy a Lotto ticket)
So I either let is die and waste my money, or hope that some one picks it up, helps the industry, reduce energy use, loss my money. (with perhaps a honourable company who will thank MF with apalm full of silver for the idea, no that is dreaming)

[chillerman2006]

The fact is I can not get repeatable test results, so does the actual widget work or not.
I also technical limitations. and do not have the right set of quals to quantify the theory a proven principle. I now long have the finacial resources to employ those with the skills to take this to a theoretical and practical level. Plus after ecent expericiences, even when I developed other technologies it is just near impossible to sell the technology for any value, (I also buy a Lotto ticket)
So I either let is die and waste my money, or hope that some one picks it up, helps the industry, reduce energy use, loss my money. (with perhaps a honourable company who will thank MF with apalm full of silver for the idea, no that is dreaming)

MF

I fully understand

You should be commended & indeed rewarded by who ever picks up your Idea for free

That is a 'very unselfish approach' to your current dilema

Mad, I take my hat off to you Sir.....much respect.....

& I hope very much that your other ventures in progress reward you to the extent you undoubtedly deserve.

Very Best Regards chillerman

ps. I removed my post from the other thread as so not to start confusing others
also I shall pm you my numbers & if I can do anything for you when in the UK, please give me a call.

[Chef]

So it would seem that all we need to know at this point, is the % by mass of the lquid and vapour streams at the relevent saturation points?

Interetsing question and an even more interesting outcome.

So the state equations seem to show the gas has no effect on the process of a 2 phase flow and therefore the corollary to this discussion so far is that the internal properties of say an evaporator can be described in fixed enthalpy values rather than a variable enthalpy.

Let me try and explain. After the TXV the value of h3 is known but as we move along the evaporator and more liquid evaporates to a gas the value of h changes and to define the properties at a new location we need to re-evaluate h from say a PH diagram.

But if we use the new equation

x=[dQ/dy*m-h4+h5]/(h4-h5)

we can now use fixed values of h namely those of the liquid line and gas line at the respective pressure. Now we can relate the fluid properties at any location with just heat input and do not need to revisit the PH diagram. The properties are defined by heat per unit length ie dQ/dy.

That would make calculations rather simpler in a 2 phase evaporator.

But this digresses from the original thread and just an interesting aside but should answer Mad's question? I think?

Chef

[Chef]

Mad – I am not sure that putting up widget #1 is your best idea. Better to solve the process issues which will then be public and other widgets may evolve along the way.

Widget #2 is not even close to being resolved yet.

Peter – very nice to see you here and I am not sure who Boles is but he sounds interesting and we await his thoughts.

There seems to be a lot of stuff needs to be done to fully understand the bell and the consequences of messing with it can be fruitful or a failure. So far the out come as noted in my last post is to relate the properties to fixed h points and that is significant from a computational point of view.

Chef

[chillerman2006]

Good Afternoon Chef

I am still to fully get my head around your equations, but I will adventually

And if I am totally honest, my first thought of your post, was this is a wind up !

Quite clearly not - Just at a level far beyond most

R's chillerman

[mad fridgie]

Mad – I am not sure that putting up widget #1 is your best idea. Better to solve the process issues which will then be public and other widgets may evolve along the way.

Widget #2 is not even close to being resolved yet.

Peter – very nice to see you here and I am not sure who Boles is but he sounds interesting and we await his thoughts.

There seems to be a lot of stuff needs to be done to fully understand the bell and the consequences of messing with it can be fruitful or a failure. So far the out come as noted in my last post is to relate the properties to fixed h points and that is significant from a computational point of view.

Chef

Hi chef, I did have to think hard about what i was going to give, but after the last few attempts at commercialization, on other ideas, (which were somewhat easier, to prove, build and test) i have decided to cut my losses, enjoy the ride. i have been in contact with one of the big multi-national component manufactures, who showed interest, only if i could front with a full working prototype and the theorectical calculations to back other selections. They would then look at the manufacture and marketting
At this time more than i am willing and can afford to risk.
To be truthful it is not an exiting enough product/idea for venture capalists

[Chef]

Good Afternoon Chef

I am still to fully get my head around your equations, but I will adventually

And if I am totally honest, my first thought of your post, was this is a wind up !

Quite clearly not - Just at a level far beyond most

R's chillerman

Chillerman this is not a wind up but serious stuff that Mad and I have been discussing for a long time without a conclusion so we thought to open it up and see if others could input some ideas. You have made several comments that are useful so that part is working - solved no - but a few more ideas to help us resolve it.
All it takes is just one comment so keep tweeting away.

Chef

[Chef]

Hi chef, I did have to think hard about what i was going to give, but after the last few attempts at commercialization, on other ideas, (which were somewhat easier, to prove, build and test) i have decided to cut my losses, enjoy the ride. i have been in contact with one of the big multi-national component manufactures, who showed interest, only if i could front with a full working prototype and the theorectical calculations to back other selections. They would then look at the manufacture and marketting
At this time more than i am willing and can afford to risk.
To be truthful it is not an exiting enough product/idea for venture capalists

Well maybe when I finally get to NZ we can sit down with the back of a fag packet and sort this all out. It needs to sorted one way or the other as it is too interesting.

[mad fridgie]

fag packet (s), now thats what i call a real design tool.

PS
NOT an homosexual packet, cigerette packet (for our north american friends)

[desA]

I'd like to introduce the basic laws of thermodynamics, to clear up the discussion a little:

http://en.wikipedia.org/wiki/Thermodynamics

If a system is in thermodynamic equilibrium and is not subject to an externally imposed force field, such as gravity, electricity, or magnetism, then (subject to a proviso stated in the following sentence) it is homogeneous, that is say, spatially uniform in all respects.[48] There is a proviso here; a system in thermodynamic equilibrium can be inhomogeneous in the following respect: it can consist of several so-called 'phases', each homogeneous in itself, in immediate contiguity with other phases of the system, but distinguishable by their having various respectively different physical characters; a mixture of different chemical species is considered homogeneous for this purpose if it is physically homogeneous.[49] For example, a vessel can contain a system consisting of water vapour overlying liquid water; then there is a vapour phase and a liquid phase, each homogeneous in itself, but still in thermodynamic equilibrium with the other phase. For the immediately present account, systems with multiple phases are not considered, though for many thermodynamic questions, multiphase systems are important.

So, the moment the vapour & liquid are 'physically separated e.g. by a wall, then they can be considered in isolation, with their own states. Once separated, thermodynamic theory would then instruct you to place the new state point at its pressure/temp/enthalpy/entropy value. In some cases, the point seems allowed to 'jump' to its new position.

Perhaps we can now explore this via thermodynamic diagrams, Chef. (Very interesting thread. Making me think a fair bit... )

[Peter_1]

Peter – very nice to see you here and I am not sure who Boles is but he sounds interesting and we await his thoughts.

This will clarify
http://books.google.com/books/about/...d=5-hSAAAAMAAJ

[mikeref]

fag packet (s), now thats what i call a real design tool.

PS
NOT an homosexual packet, cigerette packet (for our north american friends)

TO clarify further: Fag packet, meaning, packet of taylor made smokes or factory made cigarettes, as opposed to "Rollies", where one has to roll your own, and generally don't include a filter. Note: roll your own means pulling strands of ready rubbed tobacco and rolling into formation prior to placing into specific paper, such as the brand, "tally ho" than, with desired thickness, and some skill, manage to seal the deal and light the end while sucking on the other... Others, who choose to to roll funny weed will have this skill mastered. please... continue. . hand movement similar to Jedi master. Move along.

[Chef]

I'd like to introduce the basic laws of thermodynamics, to clear up the discussion a little:

http://en.wikipedia.org/wiki/Thermodynamics

So, the moment the vapour & liquid are 'physically separated e.g. by a wall, then they can be considered in isolation, with their own states. Once separated, thermodynamic theory would then instruct you to place the new state point at its pressure/temp/enthalpy/entropy value. In some cases, the point seems allowed to 'jump' to its new position.

Perhaps we can now explore this via thermodynamic diagrams, Chef. (Very interesting thread. Making me think a fair bit... )

OK we are both on the exact same page and 'jumping' to a new position with new properties seems to be possible but there is no precedence or rules as of yet.

The thermodynamic relations I proposed earlier seem to show this jump is supported for isobaric and isochoric processes but may only work for specific circumstances. What is the general form of the equations that allow us to jump to any part of the bell still keeping p and T constant?

So what have you found for a process at the moment that may take us forward?

Thanks

Chef

[Chef]

So here is a PH diagram of a 4 stage drop with phase seperation. To keep it simple I have started at h2 at the outlet of the condenser and ended up at h3-4 at the inlet to the evaporator. At each location after a stage drop the phases are split into their gas and liquid forms and repositioned on the PH diagram to relevant gas or liquid line.

This is a very basic start at suggesting a process to discuss further and obvious errors include gas that has been removed at stage 1, 2 and 3 are cooled to the final evap temperature and the process should follow an isenthalpic drop but maybe we can include that at version 2 of the diagram.

Now we have the same (actually more cooling effect) cooling as a one stage drop but several gas flows at intermedite pressures that can do work. Enter the Carter Widget.

Any comments so far?

ChefPH1.jpg

[mad fridgie]

The question then begs, when we have our various vapour streams, at different pressures (which has very little practical use in the net cooling effect) is how we can utalise the ? (being vague on purpose) to increase the pressure at the compressor suction without restricting flow in the evaporator.
What is the best possible theorectrical out come

[Chef]

Well I presume a multi ring expander with each concentric ring sized correctly for the pressure input and flow rate to combine the flows and then use the suction provided to reduce the last section of flash gas and lower its pressure and temperature and hence get more cooling. then the final gas goes to the compressor and combines with the evap gas. Seems logical.

[mad fridgie]

Well I presume a multi ring expander with each concentric ring sized correctly for the pressure input and flow rate to combine the flows and then use the suction provided to reduce the last section of flash gas and lower its pressure and temperature and hence get more cooling. then the final gas goes to the compressor and combines with the evap gas. Seems logical.

that is the problem, "it just seems logical", but somewhere in the back of mind, i feel the "Murphy effect" maybe present, the guy who trips you up at the end!

Because it is so logical, surely someone else must of been down this track?

[Chef]

Maybe you missed my point so I will try again. We have removed gas at the 8 bar line and so this gas is no longer cooled by flashing liquid, similarly the gas at 4 and 2 bar are seperated and they also need no further cooling. In a standard TXV system all the gas is cooled to the evap temp so we have saved some energy here. The question is - is it enough to help and then we have the side streams of gas.

Got to replace the mainsail so the diagram will come later.

Chef

[mad fridgie]

I understand, each proportion that is removed no longer requires the sensible energy removed. to the next stage.
Each stage then will have a greater amount of potential energy to be used for work. Whilst increasing the actual liquid mass flow to the evap (less total flash gas produced). Struggling in how to manufacture cheaply for small to medium systems, larger becomes much easier. (maybe this where it should be?)

[Chef]

The savings in liquid flashing off to cool the gas is the first part. You seem to like that bit and then something like a deLaval nozzle, they can be multi ringed concentric and have nice thermo properties. Small system is a financial problem but medium would be OK. Large systems would definetly use a compander to extract the energy sucked out of the flash gas but that is known technology for decades in the cryogenic industry so not new by an means.

To get the theory of this nailed is huge - really huge so may be a while till this thread gets a final answer unless someone pops up with a neat idea!!! Still I love a challenge.

Chef

[chillerman2006]

Chillerman this is not a wind up but serious stuff that Mad and I have been discussing for a long time without a conclusion so we thought to open it up and see if others could input some ideas. You have made several comments that are useful so that part is working - solved no - but a few more ideas to help us resolve it.
All it takes is just one comment so keep tweeting away.

Chef

Thankyou Chef

I take that as a massive compliment, coming from someone at your level

R's chillerman

[Gary]

Maybe you missed my point so I will try again. We have removed gas at the 8 bar line and so this gas is no longer cooled by flashing liquid, similarly the gas at 4 and 2 bar are seperated and they also need no further cooling. In a standard TXV system all the gas is cooled to the evap temp so we have saved some energy here. The question is - is it enough to help and then we have the side streams of gas.

Got to replace the mainsail so the diagram will come later.

Chef

I'm confused. Does the liquid cool the gas?... or does the gas cool the liquid?

[chillerman2006]

This will clarify
http://books.google.com/books/about/...d=5-hSAAAAMAAJ

Peter

Are any of these recommended purchases for my self, or a level I can not reach ???

R's chillerman

[chillerman2006]

I'm confused. Does the liquid cool the gas?... or does the gas cool the liquid?

Hi Gary

If I have followed properly, the liquid is cooled by the drop in pressure after the condensor, before the vessel, (constant pressure valve) the flash gas removal, does not affect 'p' or 't' but increase's mass to txv

Regards Chillerman

[desA]

OK we are both on the exact same page and 'jumping' to a new position with new properties seems to be possible but there is no precedence or rules as of yet.

The thermodynamic relations I proposed earlier seem to show this jump is supported for isobaric and isochoric processes but may only work for specific circumstances. What is the general form of the equations that allow us to jump to any part of the bell still keeping p and T constant?

So what have you found for a process at the moment that may take us forward?

Thanks

Chef

Ok, Chef. So you're looking for the 'jump' condition inherent within the equations - rather than simply taking for granted that the fluid 'has to' jump when split into vapour & liquid.

Let me look a little more into the equations for the 'jump' condition. Never so easy, but it should surely be there to justify the change. (I love jump conditions...

[Gary]

Hi Gary

If I have followed properly, the liquid is cooled by the drop in pressure after the condensor, before the vessel, (constant pressure valve) the flash gas removal, does not affect 'p' or 't' but increase's mass to txv

Regards Chillerman

Actually, on a drop in pressure part of the liquid flashes into vapor and heat from the liquid is transferred to that vapor... the gas cools the liquid.

[chillerman2006]

Actually, on a drop in pressure part of the liquid flashes into vapor and heat from the liquid is transferred to that vapor... the gas cools the liquid.

Hi Gary

Thankyou Sir,

Dont know what I was thinking trying to educate you, duh!

The info hit a reverse cycle valve & miss-directed

But still got you thinking, mate & now we both understand,

R's chillerman

[Chef]

Actually, on a drop in pressure part of the liquid flashes into vapor and heat from the liquid is transferred to that vapor... the gas cools the liquid.

So a small experiment is due here I feel. I pour lighter fuel on my hand and as it evaporates it gets cold, if I blow on it it gets even colder as more evaporation takes place. So you are telling me that the gas after evaporation is cold and in the time available before it disperses in the atmosphere it has time to transfer it coldness to the liquid. Yeah right I beleive that. If you wish you could provide a useful referance to support your comments.

In the PH diagram I posted there are 3 places where we propose to strip the gas away and pipe it off for its own process. The first split is at 8 bar which is 31.4C so the gas remains at that temp in its side pipe.

If we had left that gas with the rest of the refrigerant as in a standard TXV system it would need to be cooled down to -26C which is the evap temp in this case.

So we are going to need to cool that gas and the only source of 'cold' is the liquid hence my comment the liquid will cool the gas. The JT effect is not enough on its own. It is the phase transition that does the cooling.

But you say the gas cools the liquid so by dropping some gas from 8 bar to 1 bar it will cool in a process that not not only cools itself but has enough (negative) energy to also cool some of the liquid. ????

Chef

[mad fridgie]

Actually, the liquid cools the liquid.
Liquid at saturation, "no gas/vapour" so how can the gas cool he liquid.
Part of the liquid stream absorbs energy for the remainder of the liquid stream, for the correct amount of energy to be absorbed, (to reach balance) then some of the liquid has to convert into vapour(gas). The gas/vapour is a "by product". of the process. "It is the conversion" of state
I would say that the choice of word "cool" is incorrect.

[Gary]

Actually, in the transformation of liquid to vapor, heat energy is transferred from the liquid to the vapor... so... the vapor cools the liquid.

[mad fridgie]

Actually, in the transformation of liquid to vapor, heat energy is transferred from the liquid to the vapor... so... the vapor cools the liquid.

If the vapour does not exist, then it can not do any work. Yes it is the transformation, the new formed vapour holds the energy. No energy is transfered to the vapour after the vapour is formed, so the vapour can not cool the liquid.

[Gary]

Open a valve on the top of a refrigerant container. Vapor boils off and the liquid on the bottom gets very cold. Where did it's heat energy go to? It is contained in the escaping vapor.

[mad fridgie]

Open a valve on the top of a refrigerant container. Vapor boils off and the liquid on the bottom gets very cold. Where did it's heat energy go to? It is contained in the escaping vapor.

Yes the vapour hold the energy of transformation which gives the "impression" that the vapour must of cooled the liquid. For the vapour to cool the liquid, then for heat transfer to occur the liquid has to be warmer than the vapour (vapour has to be colder than the liquid).

I supose to be factual; it is the change in pressure that cools the liquid by method of liquid to vapour transformation

[Gary]

If the vapour does not exist, then it can not do any work. Yes it is the transformation, the new formed vapour holds the energy. No energy is transfered to the vapour after the vapour is formed, so the vapour can not cool the liquid.

Okay... I'll buy that.

[Chef]

Okay... I'll buy that.

Good so we all agree the cooling effect comes from the latent heat of vapourisation.

So back to the point how much energy do we save by not cooling the seperated gas flows?

[mad fridgie]

On R134a 50SCT and -30SST no sub cooling

3 takes off

30C
10C
-10C

between 9-10% extra net cooling for the same liquid mass flow

[Chef]

I also make it 9% and we still have usefull work that the gas can do.

So next how much energy do we have in the 3 streams. Lets start with the theoretical amount and then we can reduce it by an efficiency dependant on which method id used to gain that energy.

Chef