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  1. #1
    Join Date
    Dec 2010
    Posts
    59

    [compare] Wet cooling tower vs dry cooler

    Now, i am choosing heat rejection device for water-cooled chiller in hot-humid climate. Many comment say about the superiority of wet cooling tower with more effective and advantage. is it true ?
    Thanks

  2. #2
    Join Date
    Jul 2007
    Location
    The Hot South
    Posts
    1,310
    A wet (evaporative) cooling tower will be able to bring the water temp down below the outside ambient temperature to a few degrees above the dew point. The difference between the dew point and the lowest temperature the tower will be able to cool the water to is called the tower approach. Most newer towers have a very low approach (under 5 degrees). A dry cooler can only bring the water temp down to the outside ambient temp because there is no evaporation. If you are in a hot climate, a dry cooler probably won't work.

  3. #3
    Join Date
    Dec 2010
    Posts
    59
    Quote Originally Posted by R123 View Post
    A wet (evaporative) cooling tower will be able to bring the water temp down below the outside ambient temperature to a few degrees above the dew point. The difference between the dew point and the lowest temperature the tower will be able to cool the water to is called the tower approach. Most newer towers have a very low approach (under 5 degrees). A dry cooler can only bring the water temp down to the outside ambient temp because there is no evaporation. If you are in a hot climate, a dry cooler probably won't work.
    Thanks, both dry cooler and wet cooling tower can run in hot humid climate (make the cooling medium *water" higher the ambient temperature). I want to know about the effectiveness cause wet cooling tower need make-up water and water treatment system when dry cooler have less heat transfer coefficient.

  4. #4
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    2,020
    The question you should be asking is not "what should I buy?", but rather "what does the chiller require?". The chiller should have a maximum design entering condensor water temperature. The chiller doesn't care how you maintain that temperature, just that you do. Choose whatever means of cooling that water that you or your customer wants, but don't be surprised if a wet cooling tower turns out to be best. Step #1 in your quest is to find out what "design entering condensor water temperature" is. Can probably be found from the manufacturer. Design is also determined by location. If you want advice here, we need chiller model# and chiller location and chiller design conditions. But if you have all that, then you should already know what type of tower is needed.

  5. #5
    Join Date
    Mar 2011
    Location
    Louisiana
    Posts
    119
    A cooling tower or a fluid cooler will always be more efficient than a dry cooler.

    The advantages of evaporative cooling over air-cooled heat rejection stem from several key factors.

    First, cooling towers use the ambient wet-bulb temperature of the entering air as a heat sink, which is typically 10F to 30F lower than the dry-bulb temperature, depending on the local climate. The lower the temperature of the heat sink, the more efficient the process.

    Second, the evaporative cooling process involves both latent and sensible heat transfer (primarily latent), where a small portion of the recirculating water is evaporated to cool the remaining water. Air-cooled systems (which involve sensible cooling only) require a much greater volume of air to reject the same heat load, in turn requiring more fan horsepower to do so.

    Third, cooling towers allow direct contact between the air and water in the wet deck, or fill media, increasing the efficiency of heat transfer.

    Fourth, water is a much more efficient heat transfer medium than air which results in smaller equipment sizes for the same capacity both in terms of the condenser tube bundle and the atmospheric heat rejection device.

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