System Calculator???

Let me start off by telling you that I am not an engineer, I am a tech. Due to my position I am being asked to do some design work. As you can tell from my post I get to work with some oddball equipment, and I love it.

Now to the questions
1: Are there system calculators that give figures for less than -40c?

2: Is there anybody who calculates mixed refrigerants?

3: If anybody wants to enlighten me on how to calculate the effects of different mix ratios, I would like to listen.

4: is there a calculator for captube for less than -40c multi tubes.

I love to learn new things. :D

Thanks for the help

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Originally Posted by ultralo1

Let me start off by telling you that I am not an engineer, I am a tech. Due to my position I am being asked to do some design work. As you can tell from my post I get to work with some oddball equipment, and I love it.

Now to the questions
1: Are there system calculators that give figures for less than -40c?
2: Is there anybody who calculates mixed refrigerants?
3: If anybody wants to enlighten me on how to calculate the effects of different mix ratios, I would like to listen.
4: is there a calculator for captube for less than -40c multi tubes.

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Learning new things can't be done with software in our business. It all starts with thermodynamics which you have to understand.
Especially with the questions you asked, this is almost all trial and error method, you can't just calculate it.
And if there should excist software, then you certainly will have to adopt the results to the real situation.
A refrigeration cycle is not a steady/static system.

It's almost thesame as asking if there's software to calculate how to lay a brick, how to install a cable in a wall.
If you don't know the basics, then software is useless.

If software should excist, what gass will you enter with a mixture?

But I think you want to make a CPU cooler, isn't it?
You have to be more specific with your questions?

Peter1 ,Thank you for the reply.

I repair Ultralow and Cryogenic freezers at the local research University. My back ground started in 1990 in the US army repairing biomedical equipment. In 2002 recieved my state issued refirgeration contractor license. This does not mean that I am an engineer, it only means that the state thinks I know enough that I will not blow anything up.

I have specialized in the ULT and Cryogenics field. Currently I am the only person doing this in a university system with 16 seperate campuses. On my campus we have an estimated 2000-2500 of the ULT freezers alone. My shop is known as the scientific refrigeration shop. This is a university owned shop and I am a Universtiy employee. Also we are a not for profit. We provide low cost repairs for the researchers.

Being labled the "Scientific Refrigeration" shop, we get to work on many different types of refrigerated equipment. Scientific equipment is manufactured from all over the world. Some of the parts we cannot get in a timely fashion. An example would be the Techemshe compressors that are manufactured in France.

Another responsibilty we get is designing custom application systems. An example of that is one I just installed. It had 2 evaps that were installed in a vacuum chamber. Each were installed 18 inches above 8000 watt heaters. The vacuum chamber operates at less than 1 micron of vacuum. How do you calculate heat load? Oh yeah I forgot to mention that the evaps were orginally designed to have water as the fluid flowing through them and that the manufatcurer will not release any of the design specs.

All of the work above has been trial and error. I take pride in my work and I would like to reduce the number of errors in my work when I am called on to do these things.

If you have any suggestions as to where I can start my learning process I would greatly appriciate it. I am to old to start a new career as a full refrigeration engineer, so going back to college is out of the question. I will do the work to be self educated in this feild.

Again, thank you.

PS. Peter, I hope I do not fall into the category of people in your sig line

Ultralo, I should say, you have a dream-job over there, 2000 to 2500 ULT freezers...wow.
I like that.

The cooler you mounted inside the vacuum chamber, was this to cool the chamber or to help achieve the desired vacuum by capturing the water vapor via condensation on a cryocooler, a so called Meissner coil?

We've done some Meissner coolers in vacuum chambers but they didn't have to much the load.

The mix you were talking about is probably for the auto-cascade systems (polycold?)
This mixture is a secret from every manufacturer and is very, very expensive.
But,...you can do some search in the Patent databases to learn about these mixtures.

An autocascade system is something very amazing, a unique piece of high-tech refrigeration technique.
For those who never studied this a little bit deeper: going in 1 stage as low as -120°C (-184°F) and even lower.

The 'Techemshe' is kin fact Tecumseh machine but the headquarters is based in the US. Here in Europe France, they're manufacturing this compressor under the name 'l Unithé Hermétique (I would like to hear the US and UK members pronounce this once :D :p )

I should say, if you encounter a problem, fire your questions in this forum. We will try to help you out.

But don't forget and realize the following: you're working with what I see as one of the most difficult parts or sections of refrigeration techniques/machines, especially because there's almost no literature about it and those who know it keep it for themselves.

But it all comes back to the pure basics.
Many among us never saw an ULT freezer, apart from the fact they even never worked on these systems.

Some posters here are working only on these systems.
I should recommend you to buy a good book about refrigeration and try to understand what's happening. You don't have to go to school for this but take your time to learn it.
A very good start is Dossat Roy, Principles of Refrigeration.
And download also once Coolpack from the Danish University (it's free), once you understand the refrigeration cycle a little bit, you can do some simulations with cascadesytems.

Your specific question about cap tubes: you will have to experiment with this, software is only available for commercial applications.
http://www.danfoss.com/Denmark/Busin...ils/DanCap.htm It's Danish but the software is English.

But that's the good part of it, by searching for the right cap tube diameter and length, you will have to force yourself to understand what's happening in this cap tube and what the consequences are by making it too long and too short

In industrial Refrigeration form Stoecker is a formula for cap tubes but as far as I have read that section, it's only useful for Professors, not in real life situations.

Don't worry about my sig, you're one who's willing to learn this, we see other peoples here.

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The cooler you mounted inside the vacuum chamber, was this to cool the chamber or to help achieve the desired vacuum by capturing the water vapor via condensation on a cryocooler, a so called Meissner coil?

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No the coils were being used as a final condensor for a difussion pump. Diffusion pumps boil a special oil and then condense the oil and this helps achieve a very deep vacuum.

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The mix you were talking about is probably for the auto-cascade systems (polycold?)
This mixture is a secret from every manufacturer and is very, very expensive.

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I use the factory gas and procedures on these regardless of cost or time. Auto-cascades are the one area that I read and follow EVERY STEP. I was refering to regular ULT refrigerants. Example, I had one in the shop that required R407D, which is not easily accessable here. The factory suggested to make my own 30% R410A and 70% R134A. I did the mix and gassed up the system. I did not like the results. My head pressure with no load was 175psig and my bottom out temp was -52C. When I applied the load, started the second stage, my head went to 260psig and I could not maintain a negative temp in my heat exchanger. I ended up evacuating the system and and re mixed another bottle of gas. It worked great.

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The 'Techemshe' is in fact Tecumseh

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Yeah, You will see I cannot spell:D

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'l Unithé Hermétique (I would like to hear the US and UK members pronounce this once :D :p )

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:eek:

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I should say, if you encounter a problem, fire your questions in this forum. We will try to help you out.

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Thank You Very much.

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But it all comes back to the pure basics.

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Luckily the guy I was working with started out at a ULT manufacturer. He also started working when it was simpler, R500 in the 1st stage, and R503 in the 2nd. He taught me the basics and built on them. But his knowledge ended once the manual ended. I like to know more than what the manual tells you. I like to know why it tells you what it does. That is one of the reasons that I am posting here.

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I should recommend you to buy a good book about refrigeration and try to understand what's happening. A very good start is Dossat Roy, Principles of Refrigeration.

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That book is already in my referance library along with the copeland engineering manuals. I have a good foundation in the basic refrigeration cycle. It is moving past the basics that I run into trouble. that is another reason that I am hear.

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But that's the good part of it, by searching for the right cap tube diameter and length, you will have to force yourself to understand what's happening in this cap tube and what the consequences are by making it too long and too short

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The longer the tube the lower the suction pressure and les volume of refrigerant. The shorter the tube the higher the suction pressure and the more volume of refrigerant. Right?
I have no one that I can go to for the answers. That is another reason that I am hear

This site is a huge resource for me. The poeple that I work with are repair people, all that they want to do is change out parts until it works. I do not suscribe to this philosiphy. This is not meant to insult my coworkers it is just a differance of opinions. They also dont work on ULTs. They work on the regular stuff, heating and air, and walkin coolers.

All that being said, I do not expect to be spoon fed all the answers that I ask. If I ask a stupid question I expect a equivelant answer. I have "thick skin". I know that I have a lot to learn and that some of what I ask I will be expected to know already.

Thank you for sharing your Knowledge.

if you require spares for some of this equipement that you are trying to repair try Cornelius they keep techumse in stock depending on what size you want they are actually now made in mexico under a different name but so much cheaper
Regards
Adrian m

Adrian, which Cornelius are you talking about?

If in the UK then not a lot of use to Ultralo1 in his present location.

Hi there ,

Its great to hear that you are into the same field as i am here in INDIA. Ours is a set up for repairing of ULT freezers

The way u said u work without profit to the research people is great and its a great idea of course.

I would definitely share the problems with u regarding
these machines if u please.

Thanks and regards

Anurag Bhatnagar

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Originally Posted by ultralo1

Peter1 ,Thank you for the reply.

I repair Ultralow and Cryogenic freezers at the local research University. My back ground started in 1990 in the US army repairing biomedical equipment. In 2002 recieved my state issued refirgeration contractor license. This does not mean that I am an engineer, it only means that the state thinks I know enough that I will not blow anything up.

I have specialized in the ULT and Cryogenics field. Currently I am the only person doing this in a university system with 16 seperate campuses. On my campus we have an estimated 2000-2500 of the ULT freezers alone. My shop is known as the scientific refrigeration shop. This is a university owned shop and I am a Universtiy employee. Also we are a not for profit. We provide low cost repairs for the researchers.

Being labled the "Scientific Refrigeration" shop, we get to work on many different types of refrigerated equipment. Scientific equipment is manufactured from all over the world. Some of the parts we cannot get in a timely fashion. An example would be the Techemshe compressors that are manufactured in France.

Another responsibilty we get is designing custom application systems. An example of that is one I just installed. It had 2 evaps that were installed in a vacuum chamber. Each were installed 18 inches above 8000 watt heaters. The vacuum chamber operates at less than 1 micron of vacuum. How do you calculate heat load? Oh yeah I forgot to mention that the evaps were orginally designed to have water as the fluid flowing through them and that the manufatcurer will not release any of the design specs.

All of the work above has been trial and error. I take pride in my work and I would like to reduce the number of errors in my work when I am called on to do these things.

If you have any suggestions as to where I can start my learning process I would greatly appriciate it. I am to old to start a new career as a full refrigeration engineer, so going back to college is out of the question. I will do the work to be self educated in this feild.

Again, thank you.

PS. Peter, I hope I do not fall into the category of people in your sig line

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