cooling tower

Heat transfer cannot take place without a difference in temperature.

it means water is not cooled, In hot region where ambient temp. is 44 degree centgrade & temp of condensor outlet is 44 degree centgrade ,then what is purpose of the colling tower?

what is the cycle of conceration for industrial cooling tower?

coc=?

what is drift losses?

make up water calculation?

The cooling tower's conductivity controller needs to be set to 'blow down' the tower when the water becomes too 'salty'. 2000ppm total dissolved solids, or 3000μS/cm, is a typical figure, though this will vary with local conditions. Circuit volume is maintained by a simple level control; a "Portsmouth Valve" will achieve this.

Drift losses + blowdown losses + evaporation losses = make-up water volume

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

but it can make it feel like it changes temperature by changing the humidity

Heat transfer cannot take place without a difference in temperature.

Interesting discussion point...is it possible to get evapaorative cooling without a temp difference... dry air at say 20^o passing over water at 20^o ? (I don't mean to be a bargumentative astard... it just comes naturally )

Del

<....is it possible to get evapaorative cooling without a temp difference... dry air at say 20^o passing over water at 20^o ?...>

Yes, it is. It happens. The dry air will take up moisture from the water. The heat of evaporation of the water (2453.7kJ/kg at 20degC, from Steam Tables) has to come from somewhere, according to the Laws of Thermodynamics, and the effect is a lowering of the temperature of the water.

In the limit, there will be a balance reached between the water temperature and the humidity in the air; this limit is called the wet-bulb temperature.

<...I don't mean to be a bargumentative astard... it just comes naturally ...>

Oh, come, come, now. Perish the thought. Does it feel nice being stroked?

Wet bulb temp. is the main feature to size a cooling tower. Normally an approach of 3 °C is stated for water outlet temp. For instance, here in Italy, wet bulb in summer conditions (the heaviest ones) is ab. 27 °C, then outlet water is 30 °C, against a return of 40-42 °C. According to the duty, induced-draft towers are equipped with 2 or 3 fans, in order to save energy in winther (only 1 fan running due to lowest wet bulb).

There are cooling units for rooms that you can install in windows as air conditioners.

I laughed a lot!

The comfort level one could achieve bringing the relative humidity to 100% must be execrable!

BTW a fan cooling you down uses the same principle, to evaporate water to cool your skin.

It doesn't, significantly. A water tower is used when hot or warm water is substantially above air temperature. The water is spread as thin for as long and as slow as possible on surfaces or slow dripping for the air fans to blow the cooler air and assume the exchange. However in Mexico, they use air coolers trough a fan spreading atomized water to cool a room. Temperature difference can reach 20 degrees F. cooler.

Hope that answers your question

Issa

If you have a large cooling tower you need

Temperature, Relative Humidity, and Wind Speed (similar to "chill factor" or even "comfort index")

Surface area - Drip distance - Volume Throughput

Salts, Iron, and NPK

as they all affect the evaporation whether the influent water temperature is higher, lower, or equal.

Tom Williams

As previously mentioned evaporation aids in the cooling process. Assuming the cooling tower is supplying a chiller or water source air conditioning units,discharge Water from the chiller when operating will always be hotter than the inlet water. Except for transient states on start up this translates into the water returning to the cooling tower always being above the ambient wet bulb temperature.

So again making the assumption that the cooling tower is supplying a chiller or air conditioner the condition cannot exist that you're talking about. Extreme operating limits for this type of system is in the neighborhood of 120° water temperature. I personally have never seen water temperatures much above 95 ,and that's unusual with a properly sized cooling tower that is functioning correctly.

WET BULB TEMPERATURE IS THE CORRECT NUMBER TO LOOK AT. IF THERE IS NO EVAPORATION BECAUSE THE WET BULB AMBIENT IS THE SAME AS THE WATER TEMPERATURE BEING SPRAYD IN THE TOWER, THE REFRIGERANT HEAD PRESSURE WILL RISE AND ACCORDINGLY THE REFRIGERANT AND CONDENSER WATER TEMPERATURE WILL RISE AND PUT THE ENTERING WATER TEMPERATURE ABOVE THE AMBIENT AND THE EVAPORATIVE COOLING PROCESS WILL CONTINUE. IF THE AMBIENT WET BULB GOES HIGH ENOUGH YOU WILL BEGIN TO LOOSE REFRIGERATION CAPACITY BUT WITH THE EXCEPTION OF LITHIUM BROMIDE ABSORBERS YOU WOULD KEEP RUNNING UNTIL THE HIGH PRESSURE CONTROLLER SHUTS YOU DOWN. IT IS THERFORE TO LOOSE YOUR COOLING UNDER SEVERE CONDITIONS BUT THIS IS VERY INFREQUENT WITH WATERCOOLED EQUIPMENT AND LASTS ONLY A SHORT WHILE. MECHANICAL FAILURE OR OPERATOR ERROR ARE REALLY MUCH MORE COMMON AND IT'S RARELY A MATTER OF LIFE AND DEATH. WHEN WE RUN INTO THIS PROBLEM WE USUALLY FEED AS MUCH MAKE-UP WATER TO THE TOWER SUMP AS POSSIBLE BBECAUSE THE WATER IS COMING IN UNDERGROUND IS ALWAYS COOL ENOUGH TO GET MY CLIENTS OUT OF TROUBLE.

Ambient dry bulb temperature has no significant effect on cooling tower performance. Cooling tower operation is dependant on the ambient wet bulb temperature and the temperature of the hot water entering the tower. Significant temperatures relating to operation of cooling towers are: Hot Water Temperature entiring the cooling tower, required Water Temperature leaving the tower, the Ambeint Wet Bulb Temperature, and the Quanity of hot water to be cooled. Sizing the tower includes the Temperature Range of the water, H.W in - W. out. In most HVAC systems a 10 deg range is used. Approach is Leaving water temperature - Wet Bulb Temperature; again HVAC systems usually 6-7 degrees. The Ambient Wet Bulb Temperature is determined from wet bulb temperature weather records, being the highest recorded W.B.T. or 99% -97% highest, for a given period, say a 10 year period. The coolin tower manufacturer will determine the size of the tower required to meet the conditions of the design, will give the capacity of the tower under various conditions of temperatures and flows, and including the size of the fan and HP, if a forced or induced draft tower is desired.

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When I ponder, I sits and thinks, sometimes, I just sits.

g scott