The answer has been given "your" temp measurements are wrong. hence explaining about the sheet of metal, which you have not grasped.
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you wrote
on a supermarket the liquid sub cooling cooling is normally done by the medium temp rack REALLY or even an economizer, which in simple terms have a lower compression ratio to that of the freezer.
YEAH SUCTION AND DISCHARGE PRERSSURE ARE CLOSER TO ONE ANOTHER DUE TO THE HGHER BACK PRESSURE
did you read what you wrote ALSO
Plus sub cooling reduces the required mass flow, to the evap to meet a specific duty, which can also reduce the the size of the piping between the the cabinets and the rack.
sounds to me like your talking about the liquid line right above this sentence
well im only 27 and ive seen quite abit of it, so it shows how often your on the tools does it not?????
plenty of container reefers are floating around with r12 still in them, was it not me who said yeah 0.5 k glide so really very little concern in this instance remeber near azetrop
Did i say liquid line I said pipe sizing, more than one pipe.
Compression ratio reduction, equals increase in efficiency, hence saving the client money in running costs. Do you need to be spoon fed?
You have seen nothing, the world of refrigeration is massive. Why would I fix reefers, when you do?
yeah alright you really are mad,
i tell you what ill send fieldpiece a critical email and let them know the ****** who writes his own pt chart says there insruments are wrong and simply cant be used to measure a fluid in a pipe with any sort of accuracy as we get huge temp differences when placing two sensors on either side of the 1 1/8 pipe the fact that there is maybe 0.1 to .3 k diff across the readings of the two sensors stiil means the the middel of the pipe is and must be much much higher in temp as copper is a very crappy thermal conductor one of the worst probaly....
you wrote mad fridgie;
The same with your measuring methods, therefore you can not support your arguments your data is flawed.
There is a saying "shyte in -shyte out" because your raw data is shyte, then so is your assumptions.
you cant answer my question on why use a pt chart to set a txv can u, u just ignor that statement,
you also ignor my statement on turning fans off and placing probe in middel of coil and it will read the temp displayed on your gagues
dont you, u havent brought that up have u, cause that is directly contradicting all the verbal diarrhea spewing from your mouth...
you all say the chart is pointless and u say my measuring methods are flawed, u all really need to pull your heads in, as the whole world measures refrigerant like this do you think danfoss place probes in there pipework when setting there own txvs no its accebtable to have a probe on the outside of the pipe even more acctable to insulate probe area.....
you do realise temp measurement is the average rate of collision of molecules right, average being main word so all measurements of heat are flawed no sensor will ever work the way you want it to, how could it, its not measuring every single individuals molecules temp and i will never be able to measure every droplet of liquid in the liquid line
i wouldnt care if i seen a few bubbles
but when a bulk subcooled liquid flows through a sglass and u see no bubbles, then i turn the donks off and half the glass is full of massive bubbles while the temp of the liquid stays the same the whole time,
and my gauges display its subcooled the whole time....
then i turn donks back on and sglass fills up straight away all while the liquid temp stayed constant.
and the final answer u give me as to why this happens is... you measured it wrong
you cant explain it, remember i am simply copying the only temp measurment method that all of you have used your whole life
........stop thinking about it in your text book explantions simply because you cant explain what the viods in the liquid is by way of your knowledge.
lets all chuck our digi temps out with our pt charts
Just because this is the only method you know, does not mean this is the only method!
The average is correct of the pipe and its surroundings, the point you clearly miss. Is it good enough for practical refrigeration of course, but for detail it is not (and the questions you ask are about the detail). That is why when require accuracy we use various pockets, low mass sensors, sensors with limited range, thus increased accuracy and repeat-ability.
How do I know that your testing is flawed, because i too asked the same questions, but instead of being rude to those who help, i built a test rig worth well over $100,000.
let me explain about normal temps sensors, they are round, the pipe is round, so your contact point is minimal, so the rest of the probe surface area is effected by what ever is around.
The probe has mass, as does the pipe, so even though see a pressure change, there is lag between this change and changes you see in a temp probe. "thermal mass"
Then when you change form a flooded pipe (high internal thermal mass) to a pipe that has vapour in it has low thermal mass, and reduced thermal properties, then the external forces will cause a high incident of error.
When you learn some respect I will assist, but for now, you suffer in your ignorance.
Saying that let me be the first to wish you a merry christmas. I hope that santa brings you a personality
Only you say a PT chart is useless, your testing methods are for in depth knowledge. So knowing how to measure means that you can use PT chart correctly.
Why do you get the correct temp in the middle of a coil, read what I have said. The middle of a coil is effectively a pocket and is surrounded 100% by the refrigerant mass, will little influence of the ambient, not the same as a probe on the pipe, which is influenced, as proven if you wish to read.
Thanks MG Pony, it is an industry we can always learn, which is good, and it is good to ask questions and even question ourselves, but part of being a good fridgie is being able to communicate with others. Our Aussie mate has not yet learn this important part of the industry.
Haven't read all the posts, just posting this after the 2nd page: the PT chart is for a steady state system.
In a real life system, the flow also has a serious amount of kinetic energy incoporated in its flow, acting completely different than a steady state system. In the total energy is a serious amount of kineteic energy and everywhere where you decrease area (p.e. sight glass), flow will therefore increase and static pressure will decrease (Bernouillie principle) So P/T chart is then no longer valid
And measurements taken on the outside of a tube is never correct. Measure once after the TEV or at the 1st bend of the evaporator. You should see normally 'Te' but you will notice differences of 2 to 4 K, all dependend how good your probe contact is with the copper.
I think he is looking for a promotion "Public Relations Manager"
Proof,
patents, sale of IPs, commercialization, peer review. (practical and theoretical engineers)
If i am a f****** idiot, then so are those who I trained, sold to and purchased from, because I ain,t that good to pull the wool over everyone's eyes.
This site has many experts in many fields, because no one knows every thing, so your response only shows how insecure with your own knowledge base.
Much of what we believe we know is not true, but if we knew which parts then we would not believe.
On another thread I compared you to Dt larca as you seemed to show similar attributes. It is now patently clear I have done a grave injustice to DT. From your unhinged ranting (with more than a hint of racism) you are not anywhere near his level of wit or humour let alone technical ability.
I am surprised and more than a little disappointed the mods have not acted in a more appropriate manner by banning you considering we are an international forum and welcome all creeds and colours..
well said Richard, i am surprised this P**** doesn't get beaten up by every person that meets him. I can imagine he is a pleasure to work with. I did notice whilst telling us all how great he is, he didn't mention what other techs think of him. (i'm sure he will though)
.
I'm surprised this thread is still open and rjsinoz has not been reprimanded.
I have read this thread from the first post and I could not believe the hostility
in rjsinoz's posts and he reminded me of DT, like you Richard.
I have kept away from commenting (until now) because I could not weigh up
rjsinoz and I gave him the benefit of the doubt, but his post (or rantings) have
descended into personal abuse and racism.
I'm tempted to just block him (I would have done it earlier but can't remember how)
but there is an underlying problem with him if he comes onto a forum, makes a few
statements and then turns nasty because people don't shout how fantastic he is.
If you ever take advice rjsinoz, take this bit
Calm down, take deep breaths and re-read all the posts from the beginning. you might
be surprised to see that originally people were talking and offering advice but it was
you who was dogmatic in your approach and opinion that only you were correct and
every one else was wrong.
When this was pointed out to you, you then went on a personal attack and started
hurling personal insults out at almost everyone.
You might know some answers to a few things and you might be willing to learn, so
stop this arrogant, racist, insulting behavior otherwise your time on here will be
short and unpleasant.
Regards
Rob
.
I just noticed now these thread. I do not have the time these days to sit behind my computer oher than making invoices. I even read only the first 2 pages and some of the posts on the 5th page before making my statement.
It's sometimes difficult to judge how far one is going in insulting someone in another language.
I gave him the opportunity to edit his posts and perhaps previous post needs to be edited as well.
an old saying here is you can't help some on who is unwilling to help them self. I am all ways game for furthering ones grasp of their field, half the fun in refrigeration is all the neat new stuff you learn while doing it! On one of josips threads I learnt I was wrong with how I understood amonia and aluminium work togeather! some times it is hard for others to let go of their preconcieved ideas and treat it as an emotional attack rather then some one volunteering their hard earned experiance to help us on the right path!
when I look at the title in hind sight, the way it is titled lends towards he wasn't here to learn hence why I said only he could prove him self wrong, all we can do is lend out or grasp of it!
It is unfortunat he wasted this oppertunity, I hope he gets over the issues and comes back in a more responsive way to learn from the volumes of knowledge the users here posses! It has helped me along greatly. So on his behalf I thank all of you for your shared knowledge!
Mods, you are doing good job.
Just have myself a little laugh..
Checked the profile of our friend and under 'Friends' it states ---
"Rjsinoz has not made any friends yet"
About sums it up I think.
Having followed this thread from the beginning, i have to congratulate MG pony and Mad F for continuing to keep a cool head while the O.P. only showed disrespect.
Wow this has been an epic round about argument about something that doesn't even matter, totally agree with my Kiwi country man, dont ever trust instrumentation, trust averages and what is actually happening.
Let’s get a few things straight edited
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***
***
When a near stable system running at fairly consistent loads/pressures experiences a sudden or abrupt reduction in its refrigerant flow rate, the refrigerant can been seen to have a sudden pressure drop that is created at nearly the precious moment the flow rate changes
What else do we know, when a liquid line is sized up, it is, in basic terms, sized to the capacity of the compressor at a given SST at a rated ambient and pressure drop and its main function is to maintained an acceptable velocity of a liquid through the area of that pipe. So when all 4 compressors are running it can and usually does maintain a full Colum of liquid through the sight glass with minimal bubbles occurring. Assuming other conditions are correct of course.
E.g. My video-
System running normally @ 95.7psi SCT
------- THEN------
3 compressors off plus ½ of remaining compressor off (unloaded)
Effectively 12.5% capacity now running,
20seconds later video shows my awesome gauges displaying 86.8psi and rising
So its safe to safe pressure went even lower than this but let’s just go with what we can see.
Then I press some buttons and my gauges display 0.4SC..
Now it has been made perfectly clear that my measurements were flawed, which I now thank you for MAD MEN and Big Pony as you made me realise what has actually happened
I will now share it with you all, not for the benefit of this forum but to simply point out no one else ever said it or realised it.
Where is the condenser and receiver I said to myself?
Now let’s think about those statements for a while people……
That’s right all before the sight glass,
I was measuring the pressure at the inlet to the drier core and when we saw the 9psi pressure drop occur (remember probably was higher drop) then I checked sub cool reading which was only 0.4K.
Now if you all go and have a look at the various points through the video you will clearly see the liquids temp stayed the same according to my inaccurate reading.
So let’s say I now agree with you that I wasn’t recording the correct temp, whatever temp difference occurred between the pipe and the fluid, was still only ever a wrong reading on my display by which I mean my displayed showed 26.6 C when it was actually 27.6 C for an example, either way my recordings were always lower than actual fluid temp.
They must have been as if the fluid temps were lower we would have been increasing SC rate and that would completely contradicted everything you said..
So as we instantly decreased pressure by 9 psi our SCT went from 29.5C to below our actual liquid lines temp meaning the condensers coils pressure went lower and our liquid receivers pressure went lower and what happens when we lower the pressure of our condenser coil and liquid receiver to a value lower than our actual liquid lines temp……..
That’s right the liquid instantly changes state from a sub cooled liquid to a saturated liquid/fluid.
And that’s a lot of liquid which just changed state whole receiver for example…..
Then I asked myself why did the bubbles appear to become less visible as the pressure started to get higher again, then I said to myself hold on, you’re not the dumb ass, it’s because when a liquid or a saturated liquids, SCP increases as the temp of the liquid stays the same the fluid will lean towards a sub cooled state as the condensing pressure increases and start to flash the lower the SCP becomes.
And then I turn all 4 compressors on at 100% pumping rate and what happens discharge pressure rapidly rises well above the liquid actual temp and BANG we have a sub cooled liquid and see a full Colum of liquid………
AND YEAH I DID ANSWER MY OWN QUESTION .... regarding this forums actual question which was saturated conditions in a receiver tank PROVE ME WRONG
as along as equilibrium between vapour evaporating and vapour condensing is not occuring the subcooled liquid is simply evaporating inside the recevier and due to the fact that theres a constantly varying amount of liquid entering and leaving the tank, levels changing along with pressures and flow rates i know that equilibrium would never occur inside that tank.
One last thing too directed at Brian_UK.... what are you like 10 years old.
why would i want to make friend on the net i can go and drink beer with real people at the pub.... ******
as the condensing pressure DECREASES THE FLUID WILL start to flash DUE TO THE lower SCP
it’s because when a liquid or a saturated liquids, SCP increases as the temp of the liquid stays the same the fluid will lean towards a sub cooled state, as the condensing pressure DECREASES THE FLUID WILL start to flash DUE TO THE lower SCP at constant liquid temp....
Hi Ryan,
Can you answer me this, why did you join this forum. You obviously have no intention of contributing to the topics on the forum. It seems to me you only want to prove to the world you are by far the greatest engineer in the world. well done and pat yourself on the back for letting us all know how great you are. but people come on here cos they need help not belittling. You come across as being very arrogant. and just for the record, prison does not give the ability to kick the f**k out of everyone. the way you have conversed with some of the lads on here is just disrespectful,
So you just rehashed all the sh** we been saying to you and claiming it yours? Big man way to go and all that sod! indeed you are teh elite!
Why you put us in our place by throwing our own information back at us in your own words!
with your attitude I think you n the local clink will become good friends!
yeah yeah it didnt take long all i did was go through the info, shall i look for the post you clearly said its a saturated liquid caused by a sudden pressure drop.
go on show me the post that wasnt a vague statement which could me anything, in fact show me any statement you wrote to say this is what the state of the vapour is in in that sglass.
you see you are a person who gives vague answers because they dont want to back themselves on what there thoughts are.
if i think something is true ill back myself 150% and fight till the death thats what real man does, they dont um and ar cause they dont want to look like a idiot in front of other memebers they say it straight up,
then they certainly dont write a post later trying to claim they knew the answer the whole time.
you see u all think im a ****** to be polite but what u dont realise is the only time you actually said what u meant and backed yourself was when you got angry at the posts i wrote.
example big pony after i called u on it a few times you responded with why u get same sst temp as probe temp when inside a evap coil and u were spot on but u only responded cause i annoyed u enough to respond......
simply writing POCKETS in a statement is vague and not at all helpful now with a bit of anger from ur end u told me how it is........
at least i can respect you when your angry. you might not want my respect but every man should be a man and say what they belive.......
come on MAD MEN where was your answer as all i remeber u saying was saturated vapour which it clearly was not.
and when you get down to details saturated liquid is alot different to saturated vapour isin it ?>????????
Glad to see it still makes your think.
I think that the answer is covered by the terms dynamic and or change.
An in depth answer of any form could not be given, because you were blind to your earlier thoughts and practices. (how can a correct answer be given if the raw data is not correct)
So it would seem that you have understood some of the points raised, and taken these on board.
As far as your answer goes, it is on the right direction, but do you not think that things happen before the receiver inlet. Think of the thermal mass of the cond and the speed of the fan control loop. You may find that flow into the receiver stops. But liquid is still be drawn from the reciever at a momentary high rate that the comp inlet mass value. (the thermal mass of the evaps and the TXVs being open for max ref. load)
The equilibrium point is always changing by what degree is where measurement methods become important.
So why do you continue to be rude, mistakes we all make, "so i could understand your frustration" (on what should seem a simple question), you moved on technically, why not move on personally? an opportunity was given for you to teach or be taught. If you think you have nothing to learn, then you are the only one you are fooling.:p
Saturated vapour is what it is.
you have stated that the pressure changes, the liquid boils and conds, so your vapour at the interface will be saturated, and in the slight glass with turbulent mixing will also be saturated, during the process due to velocity and localized pressure differentials, could offer vapour either in a supercooled state or its own micro pressure envelope.
As many do, one of your problems is that you look at parts of a system, instead of understanding that the system is always the whole thing. refrigeration systems are circular, so a change in one area will cause change in all other areas.
So that is what you wanted to know.
If you drop the pressure on liquid that is on or close to its boiling, then it will boil? "yes" upto a point where an external energy source is required to continue the boiling process, the energy source need to be at a higher transmittable level than that of the boiling liquid.
i am sure that dropping pressure is what we try to do in a refrigeration circuit???
So answer your next question, the opposite could be true if the the pressure was increased an a vapour would turn into a liquid.
In both cases there are exceptions, for example "sublimation"
Hello all,
This is my first day on this site, this is my first thread i have read and actually my first post. I have read through this entire post, and must say I have drawn two conclusions.
First- I am completely at ease to post any questions I have here after reading through this. As i can see that, a lot of the "veteran" posters here exhibit extreme patience in the face of ignorance. So i know any discrepancies I may encounter in my logic of things as I pose questions or posts, will be met with the same patience, and that places me at ease.
Secondly- The wealth of knowledge and experience that is possessed here, from all sides of the table is phenomenal, and I look forward to learning from all of you and hopefully being able to provide my two cents and be beneficial to the community.
Plus O.P. ignorance gave me a good laugh, oddly enough the only saying that would repeatedly come to mind when reading the back and forth was "pearls before swine"
Thanks Peter,
Hi American Tech, and welcome. You picked a lively thread to respond to.
Indeed he did, idiots albeit annoying usually do offer the general community an occasional good laugh! and yes we do our best to steer ones in the most practical and accurate way we can.
To the OP: Vague is what you get, you don't grasp the system well enough for me to give a precise answer that and you do not have the tools to allow me do give any precise answer! Believe it or not I value my personal time, so when here I give the best I can with what is offered to work with, if you want me to share well over 15 years of on hand experience and 5 years of study (both where concurrent) learn some simple respect and start listening!
I was born in industry and I do mean literally, this isn't a job but a life style, when I started to get serious about this as a career is about when I started posting here and since listening to the people here and taking their advice advanced me in ways I can not begin to say, I went from a monkey like you to just grasping the system enough to do the work to grasping how to engineer a system from the ground up! You'd be wise to give your head a thorough slap and realign the way you choose your words befor having your rude rear booted off to the street, and that will be a terrible waste for you!
As Mad said, the system is a whole, and when in operation it is a game of nothing more then balance and averages, every tiny change alters the whole model in a dynamic fashion, with my tools I can get very close to real time fluid and gas temps, my tools let me place the probe in the direct flow of the fluid not the pipe and even then they are not precise enough for what you where trying to do! so you need to learn all the talk is just theory but even in theory the pt chart is just a static reference! then you need to factor in fluid dynamics where physics becomes a factor and so fourth.
@American_Tech, this was a nice intro after all this verbal violence. Welcome.
@R.B., i not allways have time to read all posts. It's extremely busy for the moment with my daily job.
Lazy sight glass!
hi ryan welcome to the forum!:D