2013



Page 1 of 2 12 LastLast
Results 1 to 50 of 73
  1. #1
    Join Date
    Jun 2005
    Location
    Madison
    Age
    52
    Posts
    32
    Rep Power
    0

    Cascade Refrigeration System


    Hello everyone,

    I am trying to design a refrigeration system which has about 20 Watts cooling capacity at -140 degree Celsius. The ambient temperature is 25 degree Celsius. I think it should be a three-stage cascade system. What I am concerning is the last stage. Does someone have any experience on such a low temperature application? Which company provides suitable compressors for this application? What kind of refrigerant I should use? What kind of compressor oil I could use in such a low temperature?

    Any comments and suggestions are appreciated.

    Thanks
    Vincent



  2. #2
    Join Date
    Jan 2005
    Location
    UK
    Age
    36
    Posts
    14
    Rep Power
    0

    Re: Cascade Refrigeration System

    Take a look here http://www.copeland-corp.com/cp_rf/p...croll_cryo.htm
    Copeland cryoscroll compressors operate with helium.

  3. #3
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,340
    Rep Power
    16

    Re: Cascade Refrigeration System

    Hi Vincent,

    There is quite a bit to be concerned with on a cascade system. The lowest stage normally uses a very high-pressure refrigerant (at ambient temperatures) to allow the system to operate in a positive pressure at the ultra low temperatures.

    Oil and refrigerant compatability and also solubility and miscibilty are some of the issues to be concerned with. The high-pressure refrigerants require a fade-out (expansion) drum so that the mass of refrigerant in the cascade system (low temp. system) can expand in volume without exceeding the system design pressure.

    The suction gas coming from the low-temperature evaporator can contain a lot of suction superheat that increases the specific volume of the refrigerant. The superheat is a combination of the evaporator superheat (the normal expected) plus all of the parasitic heat gain through the suction line, etc.

    Most of this superheat is not useful, therefore you need higher mass flows to produce the same capacity.

    If the system is to be started and run continously at low temperature this one operational concern. If the system is required to do frequent hot starts and pulldowns that can be another issue (high suction pressure pull-down conditions and overloading).

    If this is for a single use (medical storage, research test, etc.) I would recommend you look into buying one from a manufacturer who specializes in this type of work. If it is for a production item you are selling, the design and research effort may be worth your time.

    I have seen more problems with cascade systems than any other type of system. Even those built by the manufacturers. This a highly specialized and engineered system. They are also very expensive.

    It can be done however.

    Some systems I have seen use ethane, ethylene, R-23, and others. Some of these refrigerants are flammable, so this raises another level of requirements (explosion-proof electrical design- NEMA 7, Group D, Div. 1 or 2). Sometimes you can use NEMA 4nitrogen purged panels, but only with the insurers blessing.

    I hope this information is useful to you for your initial reviews.

    Best Regards,
    US Iceman

  4. #4
    Join Date
    Dec 2004
    Location
    Weihai,China
    Posts
    808
    Rep Power
    10

    Re: Cascade Refrigeration System

    Hi Vincent
    you can refer to http://www.helixtechnology.com. It's difficult to use normal vapor compression to reach to -140 Celius. pls share your progress .

    rgds
    LC

  5. #5
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    53
    Posts
    5,510
    Rep Power
    23

    Re: Cascade Refrigeration System

    We service some Polycold machines, those which Helix sells also I see.
    There working principle is the autocascade system.
    Theory is rather simple but to build it yourself is very difficult.
    But a 3 cascade sytem, yes why not.
    But like US Iceman said, be ware of the high pressures.
    Do a serach on this forum, there were some posts in the past of it.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  6. #6
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,340
    Rep Power
    16

    Re: Cascade Refrigeration System

    Vincent,

    Another idea for you to consider: using liquid nitrogen as an expendable refrigerant. If this application you have is only used periodically, an expendable refrigerant may be a much easier system to design and use.

    A gas supplier should like BOC should be able to provide additional information on costs, etc.
    Last edited by US Iceman; 20-08-2005 at 03:38 AM. Reason: spelling error - my fault, not the spellchecker

  7. #7
    Join Date
    Mar 2005
    Location
    USA
    Age
    67
    Posts
    641
    Rep Power
    10

    Re: Cascade Refrigeration System

    As suggested above, using liquid N2 is the easy way if you are doing this project short term. Other wise you are looking at a 3-step cascade. Since this is a relatively small load, equipment maybe hard to source.

    Just recently Bitzer has introduced to the US market a high pressure CO2 recip which you may be able to use. Part of the problem with compressors at such low temperatures is the casings are not designed for such low temperatures and you will need to superheat the gas to an acceptable level for the compressor. A lot of the compressors are limited to -50 to -70 dF suction.

    Also as pointed out, you will have problems with system stand by pressure so you will have to allow for an expansion tank or fade-out drum to allow the entire refrigerant charge to go to vapor state in order to stay below you system DWP when shut down. Another issue is oil return from the evaporator at such low temps.

    Designing such a low temp system is a highly specialized field and you wil find most refrigeration engineers do not have a clue as to how to approach the design.

    I can put you intouch with a consultant that can handle the design spec if you need some help. (He does not work for free.)

    Just remember the old "Buyer beware."

    Ken

  8. #8
    Join Date
    Dec 2004
    Location
    Weihai,China
    Posts
    808
    Rep Power
    10

    Re: Cascade Refrigeration System

    Hi Dear all,
    is there any useful website for low temp refrigeration design?

    rgds
    LC

  9. #9
    Join Date
    Aug 2005
    Location
    USA
    Posts
    5,340
    Rep Power
    16

    Re: Cascade Refrigeration System

    Most of the web resources you will find are from specialty manufacturers for this type of equipment. Mostly small systems and storage requirements for medical or product testing. The refrigeration design is guarded as a closely held secret, in my experience.

    You will find general specifications and performance data, but not refrigeration system details.

    Larger systems for oxygen, or other gas separation (air plants, or gas processing) are custom engineered. Usually by the larger industrial refrigeration manufacturers.

    This is not an area for casual experimentation, unless you are looking for upset customers.

    You may find some casual references in some of the better refrigeration books, but in-depth design knowledge is not commonly documented for the general public.

    The last one of these I worked on (about 10 years ago) required 50 Tons of cooling. System cost was about $2.5 million US at that time. You cannot afford to guess too many times when the system costs are this expensive.

    Regards,
    US Iceman
    Last edited by US Iceman; 22-08-2005 at 04:18 AM. Reason: spelling

  10. #10
    Join Date
    Dec 2004
    Location
    Weihai,China
    Posts
    808
    Rep Power
    10

    Re: Cascade Refrigeration System

    Hi Iceman
    Right. You can't get the system details by searching website. I believe it's more useful by communicating with the experienced guys. Low temperatue refrigeration is a not widely used field and there are not so many engineer as normal AC&refrigeration ones.
    http://www.xtremesystems.org/forums/
    It's a forum related to cooling issue,may helpful for us.

    rgds
    LC

  11. #11
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    53
    Posts
    5,510
    Rep Power
    23

    Re: Cascade Refrigeration System

    Lc
    Some of the posters here only do this kind of work.
    Forgot their names but one of them works at Revco www.revco-sci.com

    You can also search through the patent databases on the net to learn how others solved it. I have maps full of printed material of these databases, also on cryogenics.

    The autocascade is a wonderfully piece of technique. We service at a client some units from Polycold (-110C with a 10 HP Carlyle compressor in it which cools only +/- 15 m of 5/8 copper tube)
    I know and understand the great lines how this system is working (+/- the same principle how they liquefy nitrogen, this can be found in the ASHRAE books) but to build it yourselves is not that easy at all. All the HE and capillary tubes must match very precisely.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  12. #12
    Join Date
    Jun 2005
    Location
    Madison
    Age
    52
    Posts
    32
    Rep Power
    0

    Re: Cascade Refrigeration System

    Thank everyone for the valuable suggestions. Currently our company builds 2-stage cascade systems. Normally they are used in vacuum chamber and testing chamber. Two HP compressors are used. The system can reach -100 degree Celsius. We do have some experience to design and manufacture two-stage cascade systems.

    Recently, a customer has an application which needs the temperature goes down to -130 degree Celsius. We plan to develop a 3-stage system based on our current 2-stage systems. Following is an outline of my design. Please give me your opinions:

    Three HP compressors are used. For two stage systems, it is a good choice to use 2 compressors having the same power. I am not sure if this principle still works for three stage systems.

    First Stage: condensing temperature: 35C; evaporating temperature: -30C. Refrigerant: R404A or ISCEON89. A fined tube air cooled condenser is used.

    Second Stage: condensing temperature: -25C; evaporating temperature: -75C. Refrigerant: R23 or (R508 + R14).

    Third Stage: condensing temperature: -70C; evaporating temperature: -140C. Refrigerant: R14.

    By my rough calculation, if the refrigerants are selected as above, the condensing and evaporating temperatures in each stage should be the values I give. But I am not sure if the system is optimal in these conditions. It is very difficult to get the optimal solution just by calculation. I will adjust the system based on test result.

    Plate heat exchangers (WTT) are used between first and second stage, and second and third stage. Five degree temperature difference is enough for efficient heat transfer.

    The metering device in first stage is a thermal expansion valve. Capillary tubes are used in second and third stages.

    Cylinders are used as fade-out drums in second and third stages. They are place in the low side between the evaporator and the compressor. The size of the tank will be determined by experiments. There is no harm that the fade-out drum is a little bit oversize. Is it correct?

    Coalescent oil separators (Temprite) are used in second and third stages for oil separation.

    The principle of cascade system is very simple. But to select parts and build it is very challenge. I start to test the performance of the first and second stages, and hope it can provide about 300 ~ 350 watts cooling capacity at -80C for the third stage.

    Now I still have trouble to find a suitable compressor for the third stage. And I also need to confirm that R14 is the best choice for the third stage. Any information and suggestions about the compressor and the refrigerant for the third stage are welcome.

    Ken, Could you give me more information about the consultant you talked about? If he is really very professional in cascade system design, and if we really have trouble to develop it by ourselves, maybe my boss is willing to pay him for his help.

    Thanks again. I am willing to share all the information with you, and will report you guys my work on this project regularly.
    Last edited by Vincent Yu; 06-09-2005 at 01:55 PM.

  13. #13
    Join Date
    Dec 2004
    Location
    Weihai,China
    Posts
    808
    Rep Power
    10

    Re: Cascade Refrigeration System

    Hi Vincent,
    It's a website i just encountered which provide supercooler down to -150C degree,may be of some help for you.

    http://www.qdrive.com/index.php?page_id=61

    rgds
    LC

  14. #14
    Join Date
    Jun 2005
    Location
    UK
    Posts
    13
    Rep Power
    0

    Re: Cascade Refrigeration System

    Hi Vincent,
    We started using British built 3-stage cascade systems (RSS of Worthing) capable of -126 Deg. C. in the late 70's. We also tried the Harris (USA) and Lada 2-stage units but now use the autocascade systems built by Polycold and systems previously made by S-10 Technology. The autocascades are by far the most efficient and most reliable although the mixed refrigerant charges they use are also the most expensive ! The oil used for the low temperature stages was Zerol 150, this is less prone to waxing at temperatures below 70 Deg. C. but there are Polyolester equivelants available these days. Your local supplier should be able to point you in the right direction with these.

  15. #15
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    53
    Posts
    5,510
    Rep Power
    23

    Re: Cascade Refrigeration System

    Were these machines also used for a vacuum chamber/cold trap application?

    I service also Polycold at a client and the gas costs indeed a fortune. Theyu have special top-off cilinders but even then, filled with small gold particles I think.

    We once had serious troubles with a Polycold machine and a technician from Germany had to come.
    He had a book with him with sevral pictures while they're were building a Polycold machine in the factory.
    The gas mixs consists of 5 different refrigerants. Helium was the final ne, R114, I forgot the others.
    But I found several autocascade gas-mixes on the net (patent databases)
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  16. #16
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    53
    Posts
    5,510
    Rep Power
    23

    Re: Cascade Refrigeration System

    Were these machines also used for a vacuum chamber/cold trap application?

    I service also Polycold at a client and the gas costs indeed a fortune. Theyu have special top-off cilinders but even then, filled with small gold particles I think.

    We once had serious troubles with a Polycold machine and a technician from Germany had to come.
    He had a book with him with sevral pictures while they're were building a Polycold machine in the factory.
    The gas mixs consists of 5 different refrigerants. Helium was the final ne, R114, I forgot the others.
    But I found several autocascade gas-mixes on the net (patent databases)
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  17. #17
    Join Date
    Jul 2005
    Location
    shanghai
    Age
    36
    Posts
    3
    Rep Power
    0

    Re: Cascade Refrigeration System

    FOR more informations,you can go to US PATENT。BUT IT'S NOT TOO DETAILed
    http://www.uspto.gov/
    Last edited by brightfu1; 02-09-2005 at 05:02 PM.

  18. #18
    Join Date
    Aug 2005
    Location
    India
    Age
    44
    Posts
    17
    Rep Power
    0

    Re: Cascade Refrigeration System

    i from electrolux , i would like to hnad over all ultracold medical cascade refirgeration system data
    regards

    vinod,india

  19. #19
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    53
    Posts
    5,510
    Rep Power
    23

    Re: Cascade Refrigeration System

    Well, I should say, post as lmuch information as possible.
    Do you have experience with larger autocascade systems?
    Experience with a 3 stage system?
    What gasses used?
    Brand of compressors?
    Brand of oil?
    Special modification made on the compressors?
    Expansion tanks?
    ....
    ....
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  20. #20
    Join Date
    Jun 2005
    Location
    UK
    Posts
    13
    Rep Power
    0

    Re: Cascade Refrigeration System

    Vincent, Pete_1
    The compressors used for cascades and autocascades are standard units. The oil used needs to be capable of surviving the low temperatures of the final stages (Zerol 150 for example). A typical set of refrigerants used for a standard 3-stage cascade could be R404A, R23 & R14. An expansion tank for the R14 stage would be useful in keeping the static pressure down (it also helps during the defrost stage too) but is not essential ! There is an expert on autocascades within RE. His member name is JTSTEN, he has a website: http://s-10tech.com which gives his contact details. If you are serious about designing a low temperature system, he could be your man. The autocascade systems we use are capable of driving relatively large meisner coils (cryo coils) in our vacuum chambers. These reduce the temperature from ambient to >100 Deg. C. within a few minutes and can also defrost the coil in a similar time.

  21. #21
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    53
    Posts
    5,510
    Rep Power
    23

    Re: Cascade Refrigeration System

    Perhaps Jsten uses less gold particles in his gass mixes.
    An address to remember, especially we buy sometimes gasses for Polycold machines (we have to buy it in Germany, Ferrotec..)

    Polypete, what about the very low temperatures encountered when cooling to such a low temperatures: motor windings, the changing of the molecular structure of the cast iron body (justified comment of TXIceman...)
    Last edited by Peter_1; 08-09-2005 at 09:47 PM.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  22. #22
    Join Date
    Jun 2005
    Location
    UK
    Posts
    13
    Rep Power
    0

    Re: Cascade Refrigeration System

    I have not seen the suction end of the compressors used for cascades and autocascades cooled to temperatures much below -30 Deg C.. In the cascade systems we used, the R14 TEV was mounted on the outside of the vacuum chamber, usually more than 3 metres away from the cascade unit. By the time the vapour got back to the compressor, low temperatures were not a problem, sure we had frost on the suction valves and sometimes (if a TEV stuck open) frost starting to appear on the compressor body, but this did not cause any longer term problems. In the autocascade the return line in the unit is basically one long heat exchanger all the way back to the suction side of the compressor, so the high pressure refrigerant gases on the other side of this heat exchanger supply enough heat to ensure all liquid refrigerant is boiled off and by the time it reaches the compressor suction valve, the low boilers are sufficiently superheated not to cause a problem. As you can observe on your Polycold compressors Pete, a light frost on the suction valve with some condensation on the compressor back plate is about as cold as they get. In fact the rear of the compressor gets coldest during the defrost cycle when the liquid in the cryocoil is being pushed through ahead of the defrost gas. The biggest problem with both types of cascade, for us, has been oil. If it gets up to the cool solenoid valve where temperatures are probably around -90 or lower, it causes the valve to stick. Sometimes to stick open, sometimes to stick shut. The other problem with the oil is ensuring it gets returned from the colder areas in the stack and the cryocoil, back to the compressor. Oils are not always miscible with the low boilers, but the people who developed these units (including the cascades) took account of this. You will find that one component of the refigerant charge is purely for transporting the oil through the systems colder reaches.
    Last edited by Polypete; 03-09-2005 at 09:23 PM.

  23. #23
    Join Date
    Jun 2005
    Location
    Madison
    Age
    52
    Posts
    32
    Rep Power
    0

    Re: Cascade Refrigeration System

    Polypete,

    Thank you for your information. Comparing with traditional cascade systems, autocascade systems have many advantages. Only one compressor is needed. It does not work at very low temperature. Standard units can be used. The system is also more reliable. For low temperature applications, I feel this is the way to go. Now I am thinking about the possibility to design the unit as an autocascade.

    Normally, there is an oil separator between the compressor and the condenser. It separates oil from refrigerant in the 99% efficiency range. Why do we still have oil problem at lowest stage?

    In an autocascade system, all stages share one suction line. How do we control the evaporating pressure in different stages? Do we need to set the evaporating pressures at different stages to be the same value? If the evaporating pressures are different, I think cap tubes are needed between the evaporator outlet and the suction line to balance the pressure. Is it correct?

    For autocascade systems, I think to mix the refrigerant is the key. Do you have any idea about selecting refrigerants? In my project, I need about 15 watts cooling capacity at -140 degree C.

    Any information about Autocascade systems is appreciated.

    Regards,
    Vincent

  24. #24
    Join Date
    Sep 2005
    Location
    NY
    Age
    44
    Posts
    4
    Rep Power
    0

    Re: Cascade Refrigeration System

    Dumb Question? Have you looked at already made products yet? Like Revco or Sanyo Scientific? They have various -150C chest and reach in freezers. or are you looking to make something larger.

  25. #25
    Join Date
    Jun 2005
    Location
    UK
    Posts
    13
    Rep Power
    0

    Re: Cascade Refrigeration System

    Vincent
    I can only comment on what I have seen of autocascades. The oil only becomes a problem when the condensing water temperature rises above around 28 Deg. C. I believe most of the oil in the discharged mixture would be condensed with the first stage (high boiling point) refrigerant in the (water-cooled) condenser, therefore too high a condensing water temperature could allow more oil vapour to move into the colder stages of the system. Having too much of the first stage refrigerant in the system has similar consequences when it reaches the colder sections in that it causes partial blockages or the cool solenoid valve to stick. I would imagine the ideal condition would be that all of the discharged compressor oil and all of the discharged first stage refrigerant are fully condensed in the first stage condenser and then fed into the first stage evaporator and back to the compressor.
    With regard to different evaporating pressures, I have never considered this to be an issue. If evaporating pressures are the same throughout the unit, just apply the evaporating temperatures of the different components at that given pressure. The capillary tubes would then only be needed to control the flow of the liquids from the high pressure side heat exchangers (condensers) to the low pressure evaporators. The trick, I imagine and as you suspect, is in selecting the refrigerants with the desired temperature steps between them. The refrigerants we used in the 3-stage cascades may be be a good starting point - R502/R13/R14 (modern equivalents R404A/R23/R14) although with 404A being a blend, you may want to consider something else for the high end boilers. I believe the aim with the autocascade refrigerant mix is to produce a mixture which will separate out at each stage rather than a blend of refrigerants working at similar temperatures. Although achieving -140 Deg. C. with R14 alone may be a challenge if a negative evaporating pressure is to be avoided....
    Did you think about contacting JTSTEN ? He designed some of the low temperature (-120 Deg. C.) autocascades we are currently using.
    Regards, Pete
    Last edited by Polypete; 08-09-2005 at 11:44 PM.

  26. #26
    Join Date
    Jun 2005
    Location
    Madison
    Age
    52
    Posts
    32
    Rep Power
    0

    Re: Cascade Refrigeration System

    Pete,

    Thank you for your comments. I will pay more attention to separating the oil in my design. I am trying to contacting JTSTEN now. Recently I found two US patents about autocascade system (Patent No: US 6631625 B1 and 5408848). They come from the same inventor. One focuses on non-HCFC refrigerant mixture, the other one focuses on the system. Some technical details are given. Please take a look when you get a chance.

    http://patft.uspto.gov/netacgi/nph-P...S=PN/6,631,625

    http://patft.uspto.gov/netacgi/nph-P...+refrigeration)

    About the refrigerant mixture, for -140 degree C application, the refrigerant mixture is composed of five gases: R142b or R600 (25.5%), R134a (23.2%), R23 (12.8%), R14 (23.7%), and R740 (14.8%). If the system does not need to work at such a low temperature, R740 is not needed.

    About the system, the schematic diagram is very complicated. It takes me more than 2 hours to understand it. If no-CHFC refrigerants are used, the compressor is very hot. In order to avoid overheating of the compressor, the system should bypass some liquid first-stage refrigerant to reduce suction temperature.

    Peter, for autocascade system, we do not need to worry about the low compressor temperature. Actually what we need to do is to avoid overheating of the compressor. I have just learned about it. Based on the data from the patents, the suction temperature is about -5 degree C. The discharge temperature is about 120 degree C. I am interested in the idea you mentioned about adding gold particles in the refrigerant. What is the purpose to add it? Increasing the specific heat, improve the heat transfer or other purposes? The specific heat of the gold is only 128J/(kgK).

    Regards,
    Vincent

  27. #27
    Join Date
    Dec 2004
    Location
    Weihai,China
    Posts
    808
    Rep Power
    10

    Re: Cascade Refrigeration System

    Hi Vincent
    Any update for your project?
    Hope you make much progress on it-:)

    rgds
    LC

  28. #28
    Join Date
    Jun 2005
    Location
    Madison
    Age
    52
    Posts
    32
    Rep Power
    0

    Re: Cascade Refrigeration System

    Hello LC,

    Based on theoretical analyze and the information I got, An autocascade system is more efficient than a 3-stage cascade system in my application. I am thinking about designing the unit as an autocascade system. Now I am trying to collect information about autocascade systems and select components.

    Regards,
    Vincent

  29. #29
    Join Date
    Jul 2006
    Location
    India
    Posts
    2
    Rep Power
    0

    Re: Cascade Refrigeration System

    Hi everybody,
    Eventhough I recently joined, I have been visiting this site for quite some time. I am in the process of designing a cascade refrigetation system for -80 deg. C chamber. I think R-23 in the low stage and R-404a in the high stage is a good solution. In this regard I need somebody to through some light on the following.
    1) What exactly is gliding problem associated with R-404a?
    2)Why some manufacturer use few circuits in the aircooled condenser of R-404a (whose disch temperature is about +70 deg C) for low stage (R-23) discharge whose discharge temperature is +20 deg C( I hope this is correct)
    3) Is copper coil with aluminium fins evaporator OK for -80 deg.C
    4) What fans to be used for -80 deg.C.
    5)Is there any special precaution to be taken for oil return for R-23 and R-404a.
    6) I remeber somebody suggesting capillary tubes instead of Thermostatic expansion valve. How to size capillary for these refrigerants.
    7) How to calculate the refrigerant charge needed. I think this is needed to design expansion tank.
    8) The refrigeration load is around 3 Kw. Can somebody suggest the size of compressors and other equipments needed?

    (The ambient temperature in our part of the country is +40 deg.C)
    Regds,
    Jingle
    Last edited by Jingle; 26-07-2006 at 10:03 AM.

  30. #30
    Join Date
    Feb 2006
    Location
    WA, USA
    Posts
    62
    Rep Power
    9

    Re: Cascade Refrigeration System

    Jingle with a 3KW load...
    I suggest you look for a chamber with two 7.5HP compressors.
    Will melt ice for $101/hr

  31. #31
    Join Date
    Aug 2007
    Location
    MALAYSIA
    Age
    34
    Posts
    6
    Rep Power
    0

    Re: Cascade Refrigeration System

    hihi.. i m new ppl join refrigeration. i was very interesting in this sector. like cascade system unit, if we want the servicing in this system. anyway we can buy the equipment like manifold. any brand is good.

    thanks,

  32. #32
    Join Date
    Nov 2007
    Location
    yafa
    Age
    31
    Posts
    3
    Rep Power
    0

    Re: Cascade Refrigeration System

    pleas send tom pleasssssssssssss
    shadi842008@yahoo.com

  33. #33
    Join Date
    Nov 2007
    Location
    yafa
    Age
    31
    Posts
    3
    Rep Power
    0

    Re: Cascade Refrigeration System

    Hi
    im asking if any body can help us how to determine heat transfere convection coffecint in refrigerated space @-65c



    how to select components

  34. #34
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    53
    Posts
    5,510
    Rep Power
    23

    Re: Cascade Refrigeration System

    Quote Originally Posted by shadi View Post
    Hi
    im asking if any body can help us how to determine heat transfere convection coffecint in refrigerated space @-65c
    It depends if it's a cast iron, a glass or a wooden enclosure.
    That's the first thing we need to know to answer your question.
    how to select components
    You haven't said which gas you want to use, NH3, sulfurdioxide, glycol, ... so once again, to less information.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  35. #35
    Join Date
    Jun 2008
    Location
    Tuscon/
    Age
    63
    Posts
    1
    Rep Power
    0

    Re: Cascade Refrigeration System

    Question, It was mentioned in an earlier quote regarding reaching -100c in minutes from ambient and also the ability to defrost the same coils in the similar amount of time. I would be very interested to know how your achieving this. We have a -80c box with redundant systems and are using pressureized dry air -100 dew point to limit moisture. Our product storage will not stand temperature rise for defrost. What is it your doing to prohibit temperature loss and still be able to clear a coil?

  36. #36
    Join Date
    Jun 2008
    Location
    India
    Posts
    37
    Rep Power
    0

    Re: Cascade Refrigeration System

    Quote Originally Posted by ksvinod View Post
    i from electrolux , i would like to hnad over all ultracold medical cascade refirgeration system data
    regards

    vinod,india
    is it [-140c] ?

  37. #37
    Join Date
    May 2006
    Location
    Porto - Gaia
    Age
    38
    Posts
    10
    Rep Power
    0

    Re: Cascade Refrigeration System

    Quote Originally Posted by Charles Hambly View Post
    Question, It was mentioned in an earlier quote regarding reaching -100c in minutes from ambient and also the ability to defrost the same coils in the similar amount of time. I would be very interested to know how your achieving this. We have a -80c box with redundant systems and are using pressureized dry air -100 dew point to limit moisture. Our product storage will not stand temperature rise for defrost. What is it your doing to prohibit temperature loss and still be able to clear a coil?

    The way to do it is by a hot gas bypass

  38. #38
    Join Date
    Mar 2005
    Location
    USA
    Age
    67
    Posts
    641
    Rep Power
    10

    Re: Cascade Refrigeration System

    To prevent the defrost heat gain from much impact on the space is to use insulated doors on the coil inlet and outlet. Close the doors and defrost away. Chill the coil before opening to the space.

    Food industry has done this for years.

    ken

  39. #39
    Join Date
    Oct 2003
    Location
    Belgium
    Age
    53
    Posts
    5,510
    Rep Power
    23

    Re: Cascade Refrigeration System

    Quote Originally Posted by shadi View Post
    Hi
    im asking if any body can help us how to determine heat transfere convection coffecint in refrigerated space @-65c



    how to select components
    Already selected your system? Or will you stay with this one post?
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  40. #40
    Join Date
    May 2008
    Location
    Belgium
    Age
    57
    Posts
    805
    Rep Power
    7

    Re: Cascade Refrigeration System

    Yep Peter,

    die zie je nooit meer ....terug.

    Ice

  41. #41
    Join Date
    May 2008
    Location
    Belgium
    Age
    57
    Posts
    805
    Rep Power
    7

    Re: Cascade Refrigeration System

    its pity, because its a nice tread. i love to read about other opinions, and done some calculations of mi one.
    i can not build mi outcomes because the lack of money and time.
    O, and extremesystems is wonderfull to browse around to.

    hope we get more of this cind to follow.

    Ice

  42. #42
    Join Date
    Dec 2008
    Location
    usa
    Age
    69
    Posts
    3
    Rep Power
    0

    Re: Cascade Refrigeration System

    Ken
    good afternoon
    i am intrested in the low tempture cascading system that i found on this site.
    you refer to a consulant who is knowable. can you forward how to contact this person.

    thanks in advance
    chuckw

  43. #43
    Join Date
    Mar 2005
    Location
    USA
    Age
    67
    Posts
    641
    Rep Power
    10

    Re: Cascade Refrigeration System

    Chcukw, send me a PM and I can send you the name of a good consultant.

    Ken

  44. #44
    Join Date
    Dec 2008
    Location
    usa
    Age
    69
    Posts
    3
    Rep Power
    0

    Re: Cascade Refrigeration System

    Quote Originally Posted by Vincent Yu View Post
    Thank everyone for the valuable suggestions. Currently our company builds 2-stage cascade systems. Normally they are used in vacuum chamber and testing chamber. Two HP compressors are used. The system can reach -100 degree Celsius. We do have some experience to design and manufacture two-stage cascade systems.

    Recently, a customer has an application which needs the temperature goes down to -130 degree Celsius. We plan to develop a 3-stage system based on our current 2-stage systems. Following is an outline of my design. Please give me your opinions:

    Three HP compressors are used. For two stage systems, it is a good choice to use 2 compressors having the same power. I am not sure if this principle still works for three stage systems.

    First Stage: condensing temperature: 35C; evaporating temperature: -30C. Refrigerant: R404A or ISCEON89. A fined tube air cooled condenser is used.

    Second Stage: condensing temperature: -25C; evaporating temperature: -75C. Refrigerant: R23 or (R508 + R14).

    Third Stage: condensing temperature: -70C; evaporating temperature: -140C. Refrigerant: R14.

    By my rough calculation, if the refrigerants are selected as above, the condensing and evaporating temperatures in each stage should be the values I give. But I am not sure if the system is optimal in these conditions. It is very difficult to get the optimal solution just by calculation. I will adjust the system based on test result.

    Plate heat exchangers (WTT) are used between first and second stage, and second and third stage. Five degree temperature difference is enough for efficient heat transfer.

    The metering device in first stage is a thermal expansion valve. Capillary tubes are used in second and third stages.

    Cylinders are used as fade-out drums in second and third stages. They are place in the low side between the evaporator and the compressor. The size of the tank will be determined by experiments. There is no harm that the fade-out drum is a little bit oversize. Is it correct?

    Coalescent oil separators (Temprite) are used in second and third stages for oil separation.

    The principle of cascade system is very simple. But to select parts and build it is very challenge. I start to test the performance of the first and second stages, and hope it can provide about 300 ~ 350 watts cooling capacity at -80C for the third stage.

    Now I still have trouble to find a suitable compressor for the third stage. And I also need to confirm that R14 is the best choice for the third stage. Any information and suggestions about the compressor and the refrigerant for the third stage are welcome.

    Ken, Could you give me more information about the consultant you talked about? If he is really very professional in cascade system design, and if we really have trouble to develop it by ourselves, maybe my boss is willing to pay him for his help.

    Thanks again. I am willing to share all the information with you, and will report you guys my work on this project regularly.
    Vincent
    good morning
    i have been enjoying this site about the low tempture cascading systems.
    have you had any sucess with your efforts.
    i would appreciate any info that you are able to share.
    it sound like your idea has some merit.
    chuck Wiedemann

  45. #45
    Join Date
    Dec 2008
    Location
    usa
    Age
    69
    Posts
    3
    Rep Power
    0

    Re: Cascade Refrigeration System

    Quote Originally Posted by TXiceman View Post
    Chcukw, send me a PM and I can send you the name of a good consultant.

    Ken
    Ken

    good morning
    my contact info is
    Cwiedemann@space.nrl.navy.mil
    202-404-2592

    thanks in advance
    c

  46. #46
    Join Date
    Jan 2009
    Location
    Bangkok
    Age
    39
    Posts
    21
    Rep Power
    0

    Re: Cascade Refrigeration System

    Hi.Everybody I had used a cascade system at -80 c with Bock compressor . Who have been use bock.pleses advise.because I not sure the HA compressor run with R 23 can use longtime.

  47. #47
    Join Date
    Apr 2009
    Location
    Turkey
    Age
    31
    Posts
    4
    Rep Power
    0

    Re: Cascade Refrigeration System

    Hi everyone,
    I have a graudation project that is a blood storage. The blood storages are cascade system, thay works about -40 degree celcius.
    But I dont know that How I can design it after calculating cooling load.
    Please help me about design a two satge cascade refrigerator. where I will start?

  48. #48
    Join Date
    Apr 2009
    Location
    United States
    Age
    53
    Posts
    2
    Rep Power
    0

    Re: Cascade Refrigeration System

    Depending on the capacity you need at -40 you may not need a cascade a compound single stage could be used.

  49. #49
    Join Date
    Apr 2009
    Location
    Turkey
    Age
    31
    Posts
    4
    Rep Power
    0

    Re: Cascade Refrigeration System

    For blood storage cascde systems are used. I need design procedure of cascade system. You know that is is a graduation project so that it has a small capacity. It may be for 10 lt blood.

  50. #50
    Join Date
    Apr 2009
    Location
    Turkey
    Age
    31
    Posts
    4
    Rep Power
    0

    Re: Cascade Refrigeration System

    are there anyone for help me?

Page 1 of 2 12 LastLast

Similar Threads

  1. problem in Auto Refrigeration Cascade System
    By ernestlin in forum Trouble Shooting
    Replies: 17
    Last Post: 01-07-2009, 12:41 PM
  2. Refrigeration system proposal; comments please.
    By DaBit in forum Technical Speculations
    Replies: 13
    Last Post: 01-01-2003, 04:42 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •