# Thread: what is the water temperature through a cooling tower expected to be

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## what is the water temperature through a cooling tower expected to be

Is it suppose to increase by 20 or decrease by 20 degrees

2. Hmmm.... Cooling tower....

Wonder what that could mean?

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Originally Posted by syndicated
Hmmm.... Cooling tower....

Wonder what that could mean?
I don't do cooling towers. If you don't know cool

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decrease. The delta T will vary depending on environmental conditions.

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Depending on the ambient conditions.

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Well it all depends on the ambient wetbulb and your entering temperature.

In the tropics - where I am located - it always decreases (in temperate,, say winter - it should also decrease as the wetbulb will be lower than summer period). The decrease depends on the ambient wetbulb. I will use the crossflow cooling tower as an example... water enters the cooling tower at the top which is called the hot basin (reminder: I am in the tropics). Air is forced upwards by the rotating fan. both air and water interact and the air picks up the heat from the water through forced evaporation. The forced evaporation cools the water as it falls through the infill. But the final water temperature at the cold basin (at the bottom of the cooling tower) is limited by the ambient wetbulb. Wetbulb is basically the temperature of the air that is already saturated with water. Imagine a closed box and you have a nozzle that sprays fine particles of water inside the box..everything is sealed. The air in the box absorbs all fine water mist until it cannot hold anymore water - it begins to rain inside the box! - the temperature at point when the air is "full" (just before it starts raining) is called the wetbulb.

Usually for good heat transfer rate (but with standard losses) we expect the final (cold basin) water temperature to be 2.2 to 2.5 Deg C above the ambient wetbulb. if the cooling tower was in a perfectly adiabatic room, the final temperature will be equal to the wetbulb. The difference between the water temperature at the cold basin and the ambient is called approach temperature.

So the answer to your question : Ideally it should be as close as the wetbulb. Practically about 2.2 to 2.5 Deg C + ambient wetbulb is good. Higher approach temperature could mean messed up infills, bad airflow, undersized cooling tower.....

Hope the above helps.. and I don't mind being corrected if I am wrong

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Standard was 20 at a min

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Originally Posted by HVAC_MY
Well it all depends on the ambient wetbulb and your entering temperature.

In the tropics - where I am located - it always decreases (in temperate,, say winter - it should also decrease as the wetbulb will be lower than summer period). The decrease depends on the ambient wetbulb. I will use the crossflow cooling tower as an example... water enters the cooling tower at the top which is called the hot basin (reminder: I am in the tropics). Air is forced upwards by the rotating fan. both air and water interact and the air picks up the heat from the water through forced evaporation. The forced evaporation cools the water as it falls through the infill. But the final water temperature at the cold basin (at the bottom of the cooling tower) is limited by the ambient wetbulb. Wetbulb is basically the temperature of the air that is already saturated with water. Imagine a closed box and you have a nozzle that sprays fine particles of water inside the box..everything is sealed. The air in the box absorbs all fine water mist until it cannot hold anymore water - it begins to rain inside the box! - the temperature at point when the air is "full" (just before it starts raining) is called the wetbulb.

Usually for good heat transfer rate (but with standard losses) we expect the final (cold basin) water temperature to be 2.2 to 2.5 Deg C above the ambient wetbulb. if the cooling tower was in a perfectly adiabatic room, the final temperature will be equal to the wetbulb. The difference between the water temperature at the cold basin and the ambient is called approach temperature.

So the answer to your question : Ideally it should be as close as the wetbulb. Practically about 2.2 to 2.5 Deg C + ambient wetbulb is good. Higher approach temperature could mean messed up infills, bad airflow, undersized cooling tower.....

Hope the above helps.. and I don't mind being corrected if I am wrong
Excellent explanation my friend!

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Originally Posted by rupa104
Excellent explanation my friend!
Thank you

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that was a hell of a reply to such a simple question. You a teacher? Teachers have all the patience. I have none.

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Originally Posted by johnqpublic
that was a hell of a reply to such a simple question. You a teacher? Teachers have all the patience. I have none.
I am consultant / contractor on ACMV (HVAC) and compressed air systems. All my jobs are performance based - no savings or performance as promised (sometimes its humidity control for example and not energy), I dont get paid until it is achieved. Hence the need to be precise with my terms and conditions and what i can and cannot achieve - and yes, I do teach in technical workshops

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