This document provides an overview of cooling towers. It begins with introductions and definitions, explaining that cooling towers reject heat from condenser water to the ambient air. It then discusses cooling tower fundamentals, components, performance factors like approach and effectiveness. It outlines the heat transfer process. It describes the two main types of cooling towers: natural draft and mechanical draft. Finally, it lists several parameters for assessing cooling tower performance, such as range, approach, effectiveness, cooling capacity, and cycles of concentration.

1. COOLING TOWERS
 Prepared by:-
ENG/ Mostafa Nassar
 Senior Mechanical Engineer
 Phone:- 00201065749313
 E-mail:- Mostafa.sadek.nassar73@gmail.com

2. COOLING TOWERS
 INTRODUCTION
 COOLING TOWER FUNDAMENTALS
 COOLING TOWER PERFORMANCE FACTORS
 COMPONENTS AND MAIN FEATURES OF COOLING TOWER
 TYPES OF COOLING TOWER
 ASSESSMENT OF COOLING TOWER PERFORMANCE APPLICATIONS
 REFERENCES

3.  INTRODUCTION
 Cooling tower is heat rejection
device, which extracts waste heat to
the atmosphere through the cooling
of a water stream to a lower
temperature.
 It is a device designed to reject heat
from the condenser water to the
ambient air.
 Every cooling tower, no matter how
configured or constructed, must have
the elements shown in Figure 1.

4.  Cooling tower fundamentals
 Every cooling tower, no matter how configured or constructed,
must have the elements shown in Figure 2.
 Fill: Heat transfer media in the cooling tower.
 Hot-water distribution (“wet deck”).
 Pans or basins with metering outlets or spray nozzles
designed to provide an even distribution of the return
condenser water entering the fill.
 Fan(s). All cooling towers used for HVAC applications are
mechanical draft towers that use one or more fans to provide
airflow through the tower.
 Inlet louvers and drift eliminators. Inlet louvers act to force the
air entering the tower into as straight and even flow pattern as
possible.

5. COOLING TOWER HEAT TRANSFER
 Heat is transferred from a water droplet to the
surrounding air by both sensible and latent heat
transfer processes. Figure 3 illustrates a typical
water droplet and the heat transfer mechanisms.
This heat transfer process can generally be
modeled using the Merkel equation:
 The amount of heat removed from the water must
be equal to the heat absorbed by the surrounding
air as shown by the following equation:
L/G =
(𝒉𝟐−𝒉𝟏)
(𝑻𝟏−𝑻𝟐)

6.  Cooling tower performance factors
 there are three factors that define the
requirements for a specific cooling tower
characteristic:
 1. Entering (ambient) air wet bulb temperature
 2. Condenser water flow rate
 3. Approach
 Once a tower is selected, that is, the cooling
tower characteristic is established, changes in
any of these three factors may necessitate a
change in the cooling tower.

7.  Cooling tower performance
factors
 Every HVAC cooling tower has six functional components: (1) fill,
(2) wet deck, (3) basin, (4) fan(s), (5) inlet louvers, and (6) drift
eliminators. To this list we must also add the two structural
elements: the structural frame and the casing.
 FILL
 Fills types:- a) splash fill b) film fill.
 STRUCTURAL FRAME
 CASING
 The wet deck
 BASINS
 INTAKE LOUVERS AND DRIFT ELIMINATORS
 FANS, MOTORS, AND DRIVES

8.  TYPES OF COOLING TOWERS
 Basic HVAC tower configurations are dictated by
 (1) the direction of the air versus water flow through the
tower fill
 (2) the location of the tower fan(s).
 Cooling towers can be classified in two types
1) Natural Draught Cooling Tower
Natural Draught

9.  TYPES OF COOLING TOWERS
 2) Mechanical or Forced Draught
Cooling Tower
Name?
Name?

10.  Assessment of Cooling Tower Performance
 There are several parameters to assess the performance of cooling towers. Note: CT = cooling tower; CW = cooling water
1) Range
 This is the difference between cooling tower inlet and outlet temperature. A high cooling tower range means that cooling tower has
been able to reduce temperature effectively.
CT range (oC) = CW inlet temperature (oC) – CW outlet temperature (oC)
2) Approach
 This is the difference between the cooling tower outlet cold water temperature and ambient wet bulb temperature. The lower the
approach the better the cooling tower performance. The ‘approach’ is a better indicator of cooling tower performance.
3) Effectiveness
 This is the ratio between the range and the ideal range (in percentage), i.e. difference between cooling water inlet temperature and
ambien wet bulb temperature. The higher this ratio, the higher the cooling tower effectiveness.
CT effectiveness (%) = 100 x (CW in temp – CW out temp) / (CW in temp – WB temp)

11.  Assessment of Cooling Tower Performance
4) Cooling Capacity
 This is the heat rejected in kCal/hr, given as product of mass flow rate of water, specific heat and temperature difference.
5) Evaporation Loss
 This is the water quantity evaporated for cooling duty. Theoretically the evaporation quantity works out to 1.8 m3 for
following formula can be used:
Evaporation loss (m3/hr)= 0.00085 x 1.8 x circulation rate (m3/hr) x (CW inlet temperature – CW outlet temperature)
6) Cycles of Concentration
 This is the ratio of dissolved solids in circulating water to the dissolved solids in make up water. Based on the vendor of
usually 5-7.
7) Blow down Losses
 It depends upon cycles of concentration and the evaporation losses and is given by formula:
Blow down = Evaporation loss /(Cycles of concentration -1)

12.  references
 HVAC water chillers and cooling towers fundamentals, application, and
operation by Stanford, Herbert W.
 Wikipedia (images).