| Discover some cool connections between cooling tower performance efficiency , myth and reality |
Cooling towers are heart of any chemical industries. The correct sizing of cooling tower and appropriate selection of various components of cooling towers will lead to various benefits like
- Improvement in plant productivity
- Improvement in product quality
- Saving in operational costs
Further to above points, we would like to provide some technical basics of cooling tower in our knowledge sharing platform starting from today
Cooling tower rejects the process heat to the atmosphere and in turn cools the water. The performance of cooling tower depends upon various internal and external parameters like heat load, water flow rate, approach , etc.
Range -ΔT = Inlet temperature (T1) – Outlet temperature (T2)
Range is the difference between inlet temperature and outlet temperature of water from a cooling tower. It is a function of heat load and depends upon the heat generation/ rejection in the system
Approach = Outlet temp (T2) – Wet Bulb temperature (Tw)
Approach is a difference between outlet and wet bulb temperature. It depends upon the requirement, sizing of cooling tower, water flow and range.
Cooling tower efficiency =
(Inlet temperature (T1) – Outlet temperature (T2) ) /
(Inlet temperature (T1) – Wet Bulb temperature (Tw))
Cooling tower efficiency is basically a water efficiency of cooling tower. It is basically a ratio of actual / design range divided by theoretical/ ideal range.
It is experienced at many places while selecting new towers the comparison is made in the form of following table. Unfortunately for the same tower different vendors surprisingly claims different efficiency. We have no intention to make any allegations on any one, however we would like to highlight the science behind the same and remove myth which will help users for better and better evaluation.
It can be seen in above table that the requirement of client is water flow capacity of 100 cu.m/hr with range of 5 deg C and approach 4 deg C at Wet bulb temperature of 28 deg C. Thus logically as per above formula, the water efficiency of cooling tower (designed) will be
Cooling tower efficiency = ( 37 deg C – 32 deg C) /
(37 deg C – 28 deg C)
Cooling tower efficiency = 55.56%
Now this is the correct efficiency. However as seen in above table is observed that efficiency claimed by various vendors is different although all the design data is same for all the vendors. This maybe due to lack of knowledge on both the sides or with an intent to fluke with the data.