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  1. #1
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    chiller performance

    19 dk photos 013.jpg19 dk photos 012.jpg19 dk photos 010.jpg19 dk photos 011.jpg

    Carrier model 19dk61126AF

    When conducting a performance evaluation should I have the heat recovery pump running regardless of outdoor conditions?

    Should the condenser tonnage equal the Evap. tonnage plus the energy required to power the motor converted to BTU?

    Notice in the picture of the design specs it does not list the condenser rated tonnage, why is that?

  2. #2
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    Man that looks like a nice clean environment to work in not like the tight dirty attics I work in! look at all the pretty colors haha.

  3. #3
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    That is amazing. Sorry can't help with your question, but that mech room is awesome!!!

  4. #4
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    Having worked for a factory for most of my life I will tell you what I was told by the factory people. Conducting a field performance test is as close to impossible as you can get. Producing a constant load...nearly impossible. Having calibrated and accurate thermometers placed in the exact places...nearly impossible. Maintaining precise flows...nearly impossible. When a factory does performance verification and testing they do so under almost laboratory conditions. Conditions that are almost impossible to replicate in the field. But go ahead and knock yourself out...you may get close but it won't be exact by any stretch. Are the tubes absolutely "as new". A 19DK is no spring chicken, so any fouling of even minimal amounts is going to skewed the results.

  5. #5
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    Good looking mech room.
    RTFM!!!

  6. #6
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    Your cooling tonnage is 171 tons, condenser tonnage is 212 tons, motor cooling figures to be 31 tons. Your high temp condenser (heat recovery) is not figure in the overall heat balance unless the condenser flow is restricted to compensate for the heat removed from the aux. condenser which is 125 tons. All these are design data you need to get your pretty machines to operate at full load or existing operating conditions and take all the pressure drops and temperatures entering and leaving the vessels, compute your actual GPMs to Delta "T"s and do your heat balance to create your performance. You will need your existing power factor and input KW. GEO
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

  7. #7
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    Quote Originally Posted by ga1279
    Your cooling tonnage is 171 tons, condenser tonnage is 212 tons, motor cooling figures to be 31 tons.
    Your figures aren't accurate. Condenser tonnage is (GPM X Delta T)/30. Evaporator tonnage is (GPM X Delta T)/24. The condenser tonnage has to match the evaporator tonnage. The reason the flow rates through the condenser are greater and the formula for determining tonnage is different is due to heat of compression, not motor cooling. The flow rates or formulas don't change for chillers that are open drive. True some loss is associated with motor cooling, but certainly not 18% of full load capacity.

  8. #8
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    Motor cooling is an additional load, as is the oil cooler in this case. Carrier actually spec 29 to compensate for adiabatic heat of compression + motor cooling in one constant number. Just as 24 is the constant for evap tons, it can be used as a constant for condenser tonnage as long as you add in .2844 X mtr KW. This you will find in the Trane service manuals as the formula for heat balance Evaporator tons + Motor cooling = Condenser tonnage +/- 2%. Provided all your measurements are accurate. This has been the formula professional engineers have used since day one. Remember these are used at full load. In the application in question the KW will have a slight increase due to heat recovery bundle. -GEO
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

  9. #9
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    Quote Originally Posted by ga1279
    Carrier actually spec 29 to compensate for adiabatic heat of compression + motor cooling in one constant number.
    From this statement it appears that you are saying that motor cooling isn't 31 tons at full load. That's what I was getting at. Interestingly enough, at ARI standard 550/590-98 chilled water flow is calculated at 2.4 GPM/ton and condenser water is calculated at 3.0 GPM/ton. The reason is that the calculated load of the heat of compression is 25%. There is no provision in the ARI standard for motor cooling since some manufacturers employ an open design. The motor cooling part of the equation will affect the kW of the system, but I disagree that it's part of the heat transfer equation between the condenser and the evaporator. If that was true then could York use a different equation because they primarily use open drive motors? I agree motor cooling is an additional load to the overall system, but it isn't a factor in the standard by which all centrifugal chillers are rated.

  10. #10
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    While I will agree with your statements, an open drive will still use a higher constant for the condenser as we would still have the additional heat load caused by compression. All I can say is you know what works for you.-GEO
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

  11. #11
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    the tonnage calculation is: (DeltaT x GPM x Specific Heat x Specific Gravity) / 24 = Tons

    this is for evaporator AND condenser water flows. the tonnage calculation doesn't care whether it is evaporator or condenser and it doesn't know the difference anyway.

    using a different constant is a shortcut way of ASSUMING all of the other heat loads (heat of compressor, oil cooler, motor cooling, lazy technician leaning against the barrel, etc). and we all know that these heat loads change from day to day and hour to hour so using a shortcut, in my opinion, is inaccurate. on units where the motor (or starter) is cooled by the condenser (refrigerant or water), these other tonnage constants assume what those motor kW and efficiency values are.

    the evaporator tonnage is listed on this OP's chiller as 170.83 tons and the condenser is listed as 212.50 tons...this also assumes that the fluid is water. if the fluid isn't water, then to accurately calculate the tonnage would require the fluids specific gravity and specific heat.

    the fluid is listed as 'FW' which i am unaware what that means. a listed fouling factor of 0.0005 seems rather high to me. this might indicate a glycol of some kind. poor heat transfer in the tubes requires a higher lift which would indicate why the difference between the evaporator and condenser tonnage is so high. this is also an excellent reason why the constant factor in the tonnage equation should also always be 24.
    my 1st time jumping out of a plane...http://youtu.be/Kv38G0MHsGo

  12. #12
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    Well jayguy, if we are assuming as you suggest then I would have to say FW is Carrier speak for fresh water. Also if you don't mind please quit taking pictures of me holding down a centrifugal chiller by sitting on the evaporator, no one is supposed to know about that.-GEO
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

  13. #13
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    Quote Originally Posted by ga1279 View Post
    ...Also if you don't mind please quit taking pictures of me holding down a centrifugal chiller by sitting on the evaporator, no one is supposed to know about that.-GEO
    all incriminating photos are available for purchase...the negatives are priced a bit higher!
    my 1st time jumping out of a plane...http://youtu.be/Kv38G0MHsGo

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