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  1. #1
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    cooling tower capacity



    Hello dears,We have centrifugal chiller 450 ton*2 capacity, and two cooling tower. Each chiller and tower is standby. Last summer (peak time august wet bulb around 88F) chiller was tripped on high discharge pressure when standby cooling tower also working for one chiller. I am from client side and checked the submittals. Found the capacity of cooling tower is 450*2.my question is it the measurement wrong? I heard tower capacity is should be higher than chiller capacity. Consultant submittal says that chiller capacity 450 ton and tower also 450 ton.(still building is not handover being the disput is goin on)Any answer/comments would be appreciated.moideen- dubai
    Last edited by moideen; 26-12-2012 at 03:48 AM.



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    Re: cooling tower capacity

    As a rough rule of thumb, for each 1 KW you put in to a chiller you get 2 out and need to get rid of 3 through the condenser.

    If we apply that to your case then for a chiller with a 450 ton capacity you would need 225 "ton" worth of energy to run it and you would need to get rid of (450+225)= 675 "ton" of heat...



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    Re: cooling tower capacity

    Dear Moideen

    Normally there is confusion regarding cooling tower capacity in TR and refrigeration plant caapcity in TR. Refrigeration TR is equivalent to 3024 Kcal/h or 3.516 kW. However nomical capacity 1 TR of cooling tower is equivalent of heat rejection of 1 TR refrigeration plant. It is assumed that at air conditioning duty 1 TR refrigeration plant consumes power equal to 0.25 TR refrigeration capacity and therefore 1 TR nominal capacity of cooling tower is in fact equal to 1.25 TR heat rejection (3024 x 1.25 =3780 kcal/h or 3.516 x 1.25 = 4.4 kW).
    Therefore it may be 450 TR cooling tower will have heat rejection capacity of 450 x 4.4 = 1980 kW and your water chilling plant is having 450 TR = 1582 kW capacity. In case your power consumption of compressor is 1980-1582 = 398 kW then the cooling tower is so to say matching.

    In reality you will have to check the design parameters of the cooling tower such as design wet bulb temperature, water supply and return temprature and water flow rate, which will give you clear idea of the design capacity of the cooling tower.

    I hope above clarifies your queries.

    Sandybapat

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    Re: cooling tower capacity

    thanks viking,yesterday was meeting with consultant.showd me the selection of cooling tower.as per the selection chart the each cooling tower capacity is 562 ton.formula is 450*1.25.eventhough chiller is tripping when both towers are working.inspection is going on.

    thanks
    moideen-dubai

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    Re: cooling tower capacity

    Quote Originally Posted by sandybapat View Post
    Dear Moideen

    Normally there is confusion regarding cooling tower capacity in TR and refrigeration plant caapcity in TR. Refrigeration TR is equivalent to 3024 Kcal/h or 3.516 kW. However nomical capacity 1 TR of cooling tower is equivalent of heat rejection of 1 TR refrigeration plant. It is assumed that at air conditioning duty 1 TR refrigeration plant consumes power equal to 0.25 TR refrigeration capacity and therefore 1 TR nominal capacity of cooling tower is in fact equal to 1.25 TR heat rejection (3024 x 1.25 =3780 kcal/h or 3.516 x 1.25 = 4.4 kW).
    Therefore it may be 450 TR cooling tower will have heat rejection capacity of 450 x 4.4 = 1980 kW and your water chilling plant is having 450 TR = 1582 kW capacity. In case your power consumption of compressor is 1980-1582 = 398 kW then the cooling tower is so to say matching.

    In reality you will have to check the design parameters of the cooling tower such as design wet bulb temperature, water supply and return temprature and water flow rate, which will give you clear idea of the design capacity of the cooling tower.

    I hope above clarifies your queries.

    Sandybapat
    thanks sandy,
    please find the attached the cooling tower selection
    Attached Files Attached Files

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    Re: cooling tower capacity

    Dear Moideen

    What is the power consumption for 450 Ton chiller it may be around 270 to 275 kW. If it is so then the nominal capacity of cooling tower required will be around 422 TR (528 THR). In other words you might be having 6% margin in cooling tower capacity.

    The design wet bulb temp is 86 F and in summer you say it goes to 88 F. This will reduce the cooling tower capacity by around 17 to 20%. Or your condensing temperature will shoot up by 2 F. This will increase the power required for the chiller and condenser heat rejection.

    Sandybapat

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    Re: cooling tower capacity

    Quote Originally Posted by sandybapat View Post
    Dear Moideen

    What is the power consumption for 450 Ton chiller it may be around 270 to 275 kW. If it is so then the nominal capacity of cooling tower required will be around 422 TR (528 THR). In other words you might be having 6% margin in cooling tower capacity.

    The design wet bulb temp is 86 F and in summer you say it goes to 88 F. This will reduce the cooling tower capacity by around 17 to 20%. Or your condensing temperature will shoot up by 2 F. This will increase the power required for the chiller and condenser heat rejection.

    Sandybapat
    dear , CHILLER COP is .8kw/ton.so the electrical power is 360kw on full load.considering the peak wetbulb temp.shoul be increased 25% higher capacity(450*1.25).

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    Re: cooling tower capacity

    I am sooo happy to live in a country that deals with the ISO standard Joule and Joule/s (Watt) only.
    Forget about horse power, Britisch Termal Units, Calorie, Tons of refrigeration, Tons TNT, all in various kinds for various areas; long live ISO.
    Having that said, even I use the awkward kWh in a weak moment....

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    Re: cooling tower capacity

    Nico

    You are really lucky. In India still older people are using imperical units because of British legasy. Yonger generation studies in SI system ad when two generations are mixed in an industry it becomes lot of confusion. For capacity, power and heat rejection kW is better unit to simplify the calaculations.

    Sandybapat

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    Re: cooling tower capacity

    Dear Sir,

    how much capacity of expansion valve (thermostatic) is required for 110 TR CHILLER (R-22) AT 0 DEG C EVAP.TEMP.

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    Re: cooling tower capacity

    Can anyone explain something about the "approach" of the cooling tower and what is this based on?

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