cooling tower winter operation

[Lc_shi]

Hi sirs

How to deal with the icing problem while cooling tower need to run at winter time? thx!

rgds
LC

[amitsaxena]

Dear ,

Please let me know what ambient temp you are talking about? Also is there a possibility to recirculate the Water with ambient cooling and bypassing the Cooling tower.

Thanks
Amit

[Lc_shi]

thanks

It's -15C ambient temperature.

[amitsaxena]

What i feel that when you are working in -15C then you need a Heat pump hence to heat the controlled ambient.Now this heat pump is need some heat load, which you want to give through Cooling tower water.
Now there is only possibilty is that you mix some hot water to the water coming from your Heat Pump and then you wont face that prob.

Please reply if u r satisfied.
thanks
amit

[Peter_1]

The few cooling towers we have all have build-in electrical heaters. As soon temperature drops below 1°C, pump is started and no fans. If water temperature of the water measured at the inlet drops below 1°C, the heaters comes up. As soon there's load, water temperature increases and heaters shuts off.
Heaters shut off at 3°C. Second redundant thermostat set at 0°C with a timer and a warning light to warn the user that there's something wrong with the heating.
The outside steel pipes are also traced and wrapped in Armaflex.
Your first step in capacity control is only pumps Lc? Then pumps and first speed of fans and then second speed of fans?
At very low ambients - which we haven't here - you also could control speed of the pump.
As long as the water is circulating, it may go even somewhat below freezing point.

[K.R.Iyer]

This thread is interesting to read...

Is water-to-air heat pump a good option? Because water system cannot run below 0C. Is it a common practice to add glycol or some anti-freeze
agent to take care of low winter temperatures?

[amitsaxena]

Dear I dont know how much i am correct,

But in spite of fixing the heaters on the cooling tower, cant we fix the heaters with eva and make the heat transfer more efficient also the heaters will be controlled based on the cooling requirement and ambient temp.
Reply if it is possible.
thanks
amit

[nike123]

Cooling Tower Operation In Freezing Weather

Cooling towers with malfunctions can freeze during very cold weather. Typically, freezing starts at the corners of a cooling tower with a reduced or absent heat load. Increased freezing conditions can create growing volumes of ice, resulting in increased structural loads. During the winter, some sites continuously operate cooling towers with 40 °F (4 °C) water leaving the tower. Basin heaters, tower draindown, and other freeze protection methods are often employed in cold climates.


Do not operate the tower unattended.



Do not operate the tower without a heat load. This can include basin heaters and heat trace. Basin heaters maintain the temperature of the water in the tower pan at an acceptable level. Heat trace is a resistive element that runs along water pipes located in cold climates to prevent freezing.



Maintain design water flow rate over the fill.



Manipulate airflow to maintain water temperature above freezing point.

http://en.wikipedia.org/wiki/Cooling_tower

http://spxcooling.com/pdf/H-003B.pdf

[K.R.Iyer]

Thanks Nike!

You are amazingly quick with your information and support!

[nike123]

This thread is interesting to read...

Is water-to-air heat pump a good option? Because water system cannot run below 0C. Is it a common practice to add glycol or some anti-freeze
agent to take care of low winter temperatures?


It is common practice, but only on closed loop systems. Water towers could be closed loop (indirect) and open loop (open to atmosphere, direct) systems, and you cannot add glycol to open loop system.

[nike123]

Thanks Nike!

You are amazingly quick with your information and support!

Probably I should start making money of that skill.;)

[wilsoncheung]

I have some suggestions:
(1)You can collect the water indoor, so when the ambient temperature is low, you stop the pump and all the water is indoor, there will not be freeing problem;
(2)You may put heater in your outdoor water collector, when ambient temperature is low, you can turn on the heaters.

[Don Davis]

There are a lot of good suggestions in this thread but I believe there a few misconceptions about sump heaters.
Their sole purpose is to protect the sump against freeze up. Typically sized at 2-3KW each, they don't add much heat. With just the pump on, more heat would likely be removed from the water that a heater would add.
Check the cooling tower manufacturer's wiring diagram- It will show the sump heater interlocked with the pump and fan. Both must be 'off' for the heater to be enabled.
All the heater has to do is prevent basin ice from getting 'solid' thereby protecting the sump from the ice expanding before it freezes.
Bottom line... Don't expect sump heaters to significantly offset the heat rejection of an operating cooling tower.