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  1. #1
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    Air cooled condensor sizing



    I have a sitiuation , I recevied one Air cooled Condensing unit of 1.5tr capacity at -1degC evaporating and 54 degc condensing . We feel that the condesor supplied is small . As the unit is tripping frequently in HP . we checked all the other parameter which are correct as per practise.
    Can some one help us in giving following details

    1. What should be the face surface area of condensor ? the condensor supplied has 3.7 sqft of face surface area.

    2. How to decide on correct size of condensor



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    Re: Air cooled condensor sizing

    That is too little data.

    What is evaporator cooling capacity at -1°C or what is evaporator mod no.?
    What is condenser model no.
    What is compressor capacity at that conditions or what compressor model do you have.
    What is refrigerant.

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    Re: Air cooled condensor sizing

    Thanks Nike

    The compressor model is CR 30 Of kirloskar copeland make (India) Hermatic type , the compressor delivers 16000 btu/hr at -1 degC evaporating and 54 degc condensing.

    Refrigerant used - R 22

    Evaporator is of matching capacity

    regards

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    Re: Air cooled condensor sizing

    What are the physical dimensions, no. of tubes, feeds, fin spacing, rows deep, wether it has subcooling circuit or not, if so the no. of tubes, no. of feeds, tube dia. air flow etc. are required to get the capacity of the condenser. The make of condenser. If possible please provide the above, then may be I could help you.

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    Re: Air cooled condensor sizing

    Quote Originally Posted by nambiandy View Post
    Thanks Nike

    The compressor model is CR 30 Of kirloskar copeland make (India) Hermatic type , the compressor delivers 16000 btu/hr at -1 degC evaporating and 54 degc condensing.

    Refrigerant used - R 22

    Evaporator is of matching capacity

    regards
    This is result from Coolpack software!
    Check data to see if they correspond with your case!








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    Re: Air cooled condensor sizing

    Dear nike.

    thanks it is a useful information.


    Dear Mr Sen

    I do not have those details now.I will Try to get it

    Can you suggest some good book on Condesor & evaporator design

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    Re: Air cooled condensor sizing

    If you can get me the details as I had asked for, then I can work out the capacity of your existing condenser. Condenser and Evaporator design is not easy and involves a lot of deep study. The people who can, help are the members of this forum.

    If you go through the threads you will find a number of interesting discussions on this.

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    Re: Air cooled condensor sizing

    Quote Originally Posted by nambiandy View Post
    I have a sitiuation , I recevied one Air cooled Condensing unit of 1.5tr capacity at -1degC evaporating and 54 degc condensing . We feel that the condesor supplied is small . As the unit is tripping frequently in HP . we checked all the other parameter which are correct as per practise.
    Can some one help us in giving following details

    1. What should be the face surface area of condensor ? the condensor supplied has 3.7 sqft of face surface area.

    2. How to decide on correct size of condensor
    Hi,

    It is roughly expected that the face area (length * Height) of the condenser ranges from 0.275 m2 to 0.33 m2. This depends on the air temperture difference and air face velocity. If u can tell me about those parameters May be I could give u the exact sizing. However, to jude on the condenser fits this case or no the Judment should be done on the total surface area not the face "frontal" area.

    Cheers

    Mohamed

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    Re: Air cooled condensor sizing

    Face velocity should be in-between 4.5 - 5.5 m/sec. Condenser design is depend upon size of tube, thickness of tube. ambient temperature. No. of fins. If you can give me the details i can calculate the area for yyou.

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    Re: Air cooled condensor sizing

    What are the condenser entering and leaving air temperatures?

    What is the liquid line temperature at receiver outlet?

    What is the saturated condensing temperature (from pressure/temperature chart)?

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    Re: Air cooled condensor sizing

    It might seem I’m going to over simplify this but, let’s cut to the chase. The Copeland CR30 is a nominal 2.5 HP compressor, R-22 High Temp (0 to 45 F (-18C to +7C). It pumps 16,600 btuh @ +30 F (-1C) SST @ 129F (+54C) CT @ 230-1-50.

    Copelands' 2 through 3-1/4 nominal HP, rated 0 to +45 F SST, condensing units use a condenser sized at 32” x 18”, 10FPI, 3 row, and use 2 fans……… roughly 3.75 SF surface area. They rate their units up to an 110F (+43C) ambient.

    If your condenser is near this size and specifications and the ambient temperature is not extreme, them you have other problems causing the high head pressure.

    Typical causes of high head pressure:
    • Unbalanced system, load in excess of the design conditions
    • Air in the system. If so, then check the low side for a leak.
    • Dirty condenser.
    • Re-circulating of condenser air. This is a common occurrence when an oversized outdoor weather hood has been installed.
    • Air flow is restricted thru the condenser.
    • The ambient temperature surrounding the condenser is too warm. This is common on walk in coolers and freezers when the condensing unit is mounted on the box and closed off by a drop ceiling.
    • Refrigerant overcharge.
    • Liquid refrigerant backed up in the receiver.
    • Restriction in the discharge line due to physical damage or an internal restriction.
    • Incorrect air flow thru the condenser. Has someone previously installed a new fan motor or blade? Check the rotation, horsepower and blade size, compared to the specifications of the unit.
    • Fan cycle control out of calibration.
    • Flooded head pressure control: Receiver too small for summer application.
    • Flooded head pressure control: Bypass port wedged open due to a foreign material lodged in it, or the port is worn.
    • Flooded head pressure control: Field adjustable controls are set incorrectly.
    Regards……………..Powell
    Last edited by powell; 19-02-2008 at 06:47 AM.

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    Re: Air cooled condensor sizing

    I have to agree with Powell. I think that you have a problem with the fundamentals of the system.

    But i am impressed with all the system design software the was applied here. I would like to get my hands on that!!

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    Re: Air cooled condensor sizing

    Quote Originally Posted by allanbaker View Post
    I have to agree with Powell. I think that you have a problem with the fundamentals of the system.

    But i am impressed with all the system design software the was applied here. I would like to get my hands on that!!
    It is free!
    http://tinyurl.com/2hd4av

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    Re: Air cooled condensor sizing

    Hey Nike that is twice today you have given me work......im gonna start to call you boss

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    Re: Air cooled condensor sizing

    Quote Originally Posted by allanbaker View Post
    Hey Nike that is twice today you have given me work......im gonna start to call you boss
    Don't!
    Finally, after 10 years as project manager, nobody calls me "boss" any more (I am self employed, one-man-company now).

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    Re: Air cooled condensor sizing

    Quote Originally Posted by Gary View Post
    What are the condenser entering and leaving air temperatures?

    What is the liquid line temperature at receiver outlet?

    What is the saturated condensing temperature (from pressure/temperature chart)?
    To expand on this a little:

    The difference between entering and leaving air temperature is the condenser delta-T. Excessive dT indicates insufficient airflow.

    The difference between SCT and liquid line temperature is the subcooling. This tells you if liquid is backing up into the condenser (overcharge).

    The difference between liquid line temperature and leaving air temperature is the condenser approach. This tells you if there is efficient heat transfer between the refrigerant and the air (condenser coating).

    The difference between entering air temperature and SCT is the condenser TD. If all else is within normal parameters and given normal heat load, this tells you about the relative condenser sizing.
    Last edited by Gary; 20-02-2008 at 09:46 PM.

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    Re: Air cooled condensor sizing

    nambiandy,

    Do you have any follow up details? There's a lot of good input in this thread.

    I'm sure the other posting members, myself included, are interested in the results.

    Powell

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    Re: Air cooled condensor sizing

    please send me condenser design book in PDF format on sagar_babar45@indiatimes.com

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    Re: Air cooled condensor sizing

    Quote Originally Posted by sagar45 View Post
    please send me condenser design book in PDF format on sagar_babar45@indiatimes.com

    please send me $100 first... doyourownhardwork@freeloader.com
    ...and she said "give it to me you big fridgie"

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    Re: Air cooled condensor sizing

    Yo Sagar, you sound like ABBA, give me give me give me.

    what do we get ???

    Ice

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    Re: Air cooled condensor sizing

    i am desinging a condenser for Danfoss MT100 Compressor At Evaporating temperature 7.2 And 55 Condensing temp.Refriegrant R22 . The toatal heat rejection Is het Load + Compressor Work 23.5 KW+ 8 KW = 31.5 KW
    the FPI for Condenser iS 10
    The Tube Diameter IS 3/8"
    pitch Distance Horizontal Is 25.4 mm
    Please anyone suggest how can i caqlculate the heat transfer are and Air flow

    also how can i select the circuits

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    Re: Air cooled condensor sizing

    Quote Originally Posted by sagar45 View Post
    i am desinging a condenser for Danfoss MT100 Compressor At Evaporating temperature 7.2 And 55 Condensing temp.Refriegrant R22 . The toatal heat rejection Is het Load + Compressor Work 23.5 KW+ 8 KW = 31.5 KW
    the FPI for Condenser iS 10
    The Tube Diameter IS 3/8"
    pitch Distance Horizontal Is 25.4 mm
    Please anyone suggest how can i caqlculate the heat transfer are and Air flow

    also how can i select the circuits

    What is maximum ambient temperature, relative humidity and altitude?

  23. #23
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    Re: Air cooled condensor sizing

    Ambient temperature is About 43 Degc

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    Re: Air cooled condensor sizing

    Air cooled condenser surface area as well as air quantity is important. Normally around 750 to 1000 cfm per TR is required and again depends on the suction and discharge. If the ratio is more Heat rejection factor will be more.

  25. #25
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    Re: Air cooled condensor sizing

    Hi sagar,

    Get the HGM100 condensing unit from danfoss, then start your studies!!!!

    Ravi

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    Re: Air cooled condensor sizing

    Quote Originally Posted by sagar45 View Post
    Ambient temperature is About 43 Degc
    What is maximum ambient temperature, relative humidity and altitude?
    ...............................

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