Reducing Temperature in a Cooling Tower

Khalid,

I had a problem like this years ago and corrected it by cleaning the area where the water begins to drain into the structure and adjusting the inlet flow rate.

Good luck,

Ted

Many years ago an inexperienced engineer at a primary pharmaceutical manufacturing works in Dagenham complained at the high temperatures of the cooling water circuit that occurred during a hot and particularly humid summer. This individual hadn't understood use of psychrometric charts as a guide to the performance of cooling tower systems at different times of the year.

The minimum air temperature in a cooling tower is the wet-bulb temperature of the air passing through it. As the air approaches this temperature, there is less scope for the water to evaporate to absorb the sensible heat. At the wet-bulb temperature, that's it: one cannot go lower.

To go to a lower service temperature than the local wet-bulb, and certainly to maintain a constant cooling medium supply temperature (why?), one must use some form of refrigeration. One might also question the "requirement" for 22degC in the context of the process plant where the cooling service is required.

An excellent reply. Other than a refrigeration system it is impossible to get to lower than the wet bulb temperature.

I have observed that few engineers have a good grasp of use of the psychometric charts. If a tower is properly designed and maintained, it will do what it is engineered to do. Unfortunately, other operators will add on heat loads not initially intended for the system and then wonder what happened.

Khalid

Been a few years since I had a brush with cooling towers. However, puzzles like this are great fun. Just don't take this response too seriously.

Since the calculations for cooling flow are done in advance of the tower construction, I'm in general agreement that a flush, cleanup or overhaul might be indicated to bring the tower back into line. But as these are generally done in the off-season anyway, perhaps you might examine a re-calculation of tower size or some creative modifications.

Hypothetically, the cascade's effectiveness might be enhanced through the provision of a shade canopy or incremental extension of the vanes, producing a greater turbulence and air exposure to the coolant; or the tower might be supplied with a supplemental radiator or titanium heat exchanger cooled by the first circulation of the newly cooled cooloant.

Mark