GE

Oil & Gas

Benefits

Evaporative Cooler

Get more from your 

Gas Turbines

centrifugal

pump

gate valve

demister

water

distribution

pad

evaporative

cooling

medium

FILTERED

AIR FLOW

water flow

meter

water

distribution

manifold

water flow

regulator

FILTERED AND COOLED AIR FLOW

UNFILTERED,WARM AIR FLOW

INLET FILTER

ADDITIONAL

EVAPORATIVE

COOLER SECTION

DUCT ADAPTER

INLET FILTER CHAMBER

WITH EVAPORATIVE COOLERS

BLOW DOWN

CONDUCTIVITY

CONTROLLER

CONDUCTIVITY

PROBE

gate valve

float valve

water supply

drain

Makeup water flow rate (m3/h)

1000

100

10

Inlet air flow rate (kg/s)

0,1 1,0 10,0 100.0

MS7001

MS9001

MS6001 MS5001/2

MS3002

PGT5

PGT10

Figure 1

Increased production 

 Higher efficiency 

  Compliance with environmental regulations

   Availability and Reliability 

   Life extension 

Customer benefits include the following:

• Increase in turbine output

• Increase in turbine efficiency/decrease in heat rate

• No modifications to the gas turbine

The evaporative cooler system installation depends primarily on the

plant where it is to be installed. It must be noted that adding an

evaporative cooler causes an additional pressure drop in the inlet

ducts. This increase is limited however, to approximately 15 mmH2O.

This system requires a supply of suitably treated water, therefore, a

water treatment system must be installed if one is not already

available. At low temperatures, the system must be deactivated and

drained to avoid the risk of icing.

g
What it is

The amount of water required for

evaporative cooling depends on the

inlet air flow, the temperature, pressure

and humidity of the ambient air, and

the hardness of the water. The increase

in power available from a turbine with

an evaporative cooler depends on the

turbine model and ambient conditions

(pressure, temperature and humidity).

As previously mentioned, the greatest

advantages are obtained in hot, dry

climates. Clearly, the temperature drop

realized by the cooler is not only a

function of atmospheric conditions, but

is also related to the cooler design, and

particularly the cooler’s effectiveness,

which is defined as follows:

• Evaporative cooling has the

advantage that it can be installed

without modification of the gas

turbine

• The components it requires and the

control system are also easy to install

Cooler Operation

Water is pumped from a tank at the

bottom of the module to a header

above the heat exchange medium. A

spray system wets the top of the

medium and the water flows through

the channels of the medium, which are

made of corrugated layers of fibrous

material. The layers of channels in the

medium alternately contain water and

air. The water flows down through the

channels by gravity, wetting the

material of the walls where some of it

evaporates into the air.

Excess water is collected in the tank

below together with makeup water.

The level is maintained by a valve that

admits makeup water when the water

drops below a pre-defined level.

Water System

The amount of water which must be

provided as makeup is the sum of

evaporation, carryover and blowdown.

The rate at which the water is evaporated

into the air stream depends on the

ambient temperature, humidity

and pressure, cooler effectiveness, 

and turbine airflow.

A certain amount of water is entrained

in the form of droplets by the air

stream entering the turbine. 

It may either have escaped from the

channels or have dripped from the

medium retainers. To reduce carryover,

mist eliminators are installed on the

downstream side of the medium.

These capture the droplets by

impingement of the air flow and drain

the liquid to the cooler tank. Since the

cooling water recirculates, part of it

must be drained periodically (termed

blowdown) and be made up with new

water. This makes it possible to control

the concentration of substances

present in the water supply that could

cause scaling and corrosion if allowed

to reach excessive concentrations. 

Figure 1 shows the makeup water

requirement for different turbine

models, referring to an 80% effective

evaporative cooler operating at 35°C

and 20% R.H.

The amount of makeup is calculated by

taking into considering the replacement

of enough raw water (high CaCO3

hardness) with treated water (low

CaCO3 hardness) to maintain a level

of 140 PPM of water hardness as CaCO3.

Scope of Supply

This uprate is very customer/site

specific and must be

engineered on an individual basis. 

The scope of supply includes:

• Header

• Medium retainers

• Mist eliminator

• Instrumentation

• Evaporative cooler arrangement

• Control system

• Modification and installation drawings

A demineralized water supply system

can be also supplied upon request.

An evaporative cooling system for

turbine inlet air is a useful option for

installations where high ambient

temperatures and low relative

humidity are common. With an

evaporative cooler, water is added to

the inlet air of a gas turbine. Part of

the water evaporates absorbing

latent heat from the air. As a result,

the air, which gives up sensible heat,

cools and increases in density. This

gives the machine a higher mass flow

rate and pressure ratio resulting in an

increase in turbine output and

efficiency.

For example, considering a dry-bulb

temperature of 40°C with 20%

relative humidity, the output power

can be increased by about 12% if an

80% effective evaporative cooler is

used. Correspondingly, the heat rate

decreases by about 4%. The benefit

of an evaporative cooler system from

an economic point of view is strictly

related to the potential average

annual increase in output. The

Evaporative Cooler can be applied to

all Heavy Duty gas turbines.

How it works

16

14

12

10

8

6

4

2

0

Output increase (%)

Ambient air dry bulb temperature (∞C)

10%

20%

30%

40%

50%

60%

RH

15 20 25 30 35 40

5

4,5

4

3,5

3

2,5

2

1,5

1

0,5

0

Heat rate decrease (%)

Ambient air dry bulb temperature (∞C)

10%

20%

30%

40%

50%

60%

RH

15 20 25 30 35 40

gGE imagination at work

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