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  1. #1
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    Aug 2000
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    Falling Film Technology Chiller

    Dayummm...
    Just witnessed a new Falling Film chiller that has awesome numbers..Two chillers over 1000 tons each, parallel with each other and identical chw flows and identical output temps. The old 3-stage is pulling almost exactly "Twice" the kw input as the new YK. Over 1000tr capacity and with only a 1700# ref. charge. The motor on the new YK is only 600hp..Talk about raising the bar a little..Damned if they have'nt knocked the ball out of the park with these chillers.
    Ain't "None" of us as smart as "All" of us..

  2. #2
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    Sep 2008
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    Have worked with the falling film evap since 98 and can vouch for the advantages of the design for reduced refrigerant charge and thermal efficiency advantages using HFC 134a. A potential issue of the design is the tendancy to carryover refrigerant if the evaporator oil concentration increases due to any performance problems with the oil management system, for a centrifugal compressor this will be critical as it will not be as tolerant to rerfrigerant carryover as a screw.

    Anyway to throw it out there for debate is the falling film a flooded evaporator or not?
    Necessity is the mother of invention

  3. #3
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    Dec 2011
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    Sebastian, Fl.
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    8

    Falling Film Chillers

    I have to plead ignorant to these chillers can someone explain how they work and some of the operating characteristics. Thanks

  4. #4
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    Mar 2005
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    664
    we are talking about spray nozzle type distribution? definitely flooded
    Keep it simple to keep it cool!

  5. #5
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    Dec 2008
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    Quote Originally Posted by Screwit View Post
    Anyway to throw it out there for debate is the falling film a flooded evaporator or not?
    It's a flooded evaporator that's been turned upside down internally. That's simplistic, but I'm just a simple kinda' guy. I don't have an issue with the technology of falling film, but I do have a problem with a "flooded" barrel being used in an outdoor application such as the RTAC, where the slightest misstep can create problems with ruptured tubes during the winter months.

    As you stated, there's very little room for error when it comes to the natural goings on of a chiller, such as oil circulation. Due to these things, it brings it's own set of problems to the table even though there are certain advantages.

    I haven't seen the test data on this stuff, so although I can understand that the refgt charge can be altered significantly (which could be good or bad, depending on your viewpoint), I have a hard time believing that power consumption goes down just because of this type heat exchanger. A btu is a btu, and it takes XX amount of refgt to carry XX amount of them little buggers, and we're still using a centrifugal or screw compressor to pump that refgt that's only superheated a bare minimum due to evap design, whether flooded or falling film. Maybe I'm missing something.....

  6. #6
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    Dec 2008
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    Dixiana, AL
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    Quote Originally Posted by a/c wizard View Post
    I have to plead ignorant to these chillers can someone explain how they work and some of the operating characteristics. Thanks
    Imagine a flooded barrel turned upside down with the liquid falling out of the distribution area over the tubes. It's sort of like the evaporator in an absorber works, only different. I've never seen the inside of one, so I don't know if they use spray nozzles or flow distribution, but you get the gist of it.

  7. #7
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    Quote Originally Posted by klove View Post
    It's a flooded evaporator that's been turned upside down internally. That's simplistic, but I'm just a simple kinda' guy. I don't have an issue with the technology of falling film, but I do have a problem with a "flooded" barrel being used in an outdoor application such as the RTAC, where the slightest misstep can create problems with ruptured tubes during the winter months.

    As you stated, there's very little room for error when it comes to the natural goings on of a chiller, such as oil circulation. Due to these things, it brings it's own set of problems to the table even though there are certain advantages.

    I haven't seen the test data on this stuff, so although I can understand that the refgt charge can be altered significantly (which could be good or bad, depending on your viewpoint), I have a hard time believing that power consumption goes down just because of this type heat exchanger. A btu is a btu, and it takes XX amount of refgt to carry XX amount of them little buggers, and we're still using a centrifugal or screw compressor to pump that refgt that's only superheated a bare minimum due to evap design, whether flooded or falling film. Maybe I'm missing something.....
    Agree on flooded and simple works best for me, the way I interpret evap terminology is refrigerant in the vessel/water in the tubes = flooded vessel, refrigerant in the tubes/water in the vessel = Direct Expansion

    The key to the efficiency of falling film technology is it allows for improved heat transfer using less refrigerant (compared to a full flooded type evap) and more importantly the refrigerant distribution allows for a lot more copper in the exchanger so smaller approach/better heat exchanger efficiency.

    Anyway as the saying goes a picture is worth a thousand words
    Attached Files Attached Files
    Necessity is the mother of invention

  8. #8
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    Mar 2004
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    ottawa canada
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    The best way to think of it would be a large drain pan above the tubes . The pan is full of holes . The liquid refigerant drains (no pressure or spray) through the holes and coats the tubes with a "falling film " of liquid refrigerant . Thats why the RTAC likes to se 0" of liquid level . Simply put all the liquid evaporated before it reached the bottom of the evap this is the most efficient evap . If liquid makes it to the bottom as liquid you spent money to buy the beer and didnt drink it ,ie- wasted energy making liquid .

    Its not flooded its not DX its a totally different animal. Its a Hybrid .
    The toy chest is officially full ... I got a new toy..... 2007 Aston Martin V8 Vantage
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  9. #9
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    Mar 2005
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    I see, so thats the confusion, there are flooded evaps with that type of distrib , but got ya , falling film distinct , stan
    Keep it simple to keep it cool!

  10. #10
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    Mar 2005
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    Indiana
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    Another thing that might make things more clear for some is that if you look at the end of the tube sheet you would see that the tubes line up vertically with the tube directly above it not two rows above. So as refrigerant falls over one tube it then falls directly onto the next tube below so alot less refrigerant can be used.

  11. #11
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    Quote Originally Posted by graham View Post
    Thats why the RTAC likes to se 0" of liquid level . Simply put all the liquid evaporated before it reached the bottom of the evap this is the most efficient evap . If liquid makes it to the bottom as liquid you spent money to buy the beer and didnt drink it ,ie- wasted energy making liquid .

    Its not flooded its not DX its a totally different animal. Its a Hybrid .
    For the RTAC the 0" level is in reference to the optimum pool height in the bottom of the evaporator which is critical to the performance of the falling film concpt.

    A level below the optimum point indicates the evaporator is not being supplied sufficient refrigerant so the longer vertical tube columns are running dry resulting in a loss of efficiency.

    At the same time if the level is above the optimum height this affects heat transfer to refrigerant pool therefore efficiency as well as effective oil return.
    Necessity is the mother of invention

  12. #12
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    Dec 2011
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    Sebastian, Fl.
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    Smile Falling curtin chiller

    Quote Originally Posted by klove View Post
    Imagine a flooded barrel turned upside down with the liquid falling out of the distribution area over the tubes. It's sort of like the evaporator in an absorber works, only different. I've never seen the inside of one, so I don't know if they use spray nozzles or flow distribution, but you get the gist of it.
    Thanks to all, I have a good understanding of it now.

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