FIELD OF INVENTION:
The present invention relates to an air-cooling arrangement of turbo-generator
operated in a power plant for utility and also for industrial application.
More particularly, the invention relates to Installation of Twin row of cooler
arrangement for improving air-cooled generator efficiency by substitution of a
single row of coolers.
BACK GROUND OF THE INVENTION:
An industry engaged in manufacturing turbo-generator set is required to make
such a plan and specification so as to obtain a maximum output while in operation.
When a turbo-generator is in operation, the heat generated during operation is
dissipated to air to water heat exchangers, called as cooler. These exchanger are
arranged below or at the side of the generator as a row of element. Hot air is
allowed to flow across the row ensuring equal pressure drop while heat is
dissipated to the water following through the subbing assembled in the individual
cooler elements. The cold air is brought back to generator through the duct paths
arranged along side. Fans mounted on the generator rotor impart the necessary
head for the airflow to take place across the coolers and through duct paths.
A prior Art discloses a single row of cooler means with a generator set for cooling.
But the problems arises by the useage of single row cooler is that it requires to be
cleaned periodically to remove fouling. Wire brushes are employed to carry out
cleaning. The coolers are also attended to when any of the partition gaskets fail
leading to water leakage. The repair involves separating the water-boxes and
replacing the damaged gaskets. Many a time, tube failure problem is noticed
where a single tube out the total tube nest punctures. This happens due to
fouling build up. Feed water quality or the water purification plant determines the

frequency to the problem occurrence. Usually such problems are assessed by
simple plugging of the punctured tube when cooler heat load falls slightly.
The coolers are required to be repaired before re-commissioning. The repairs
maintenance of coolers are done while the turbo-generator set is in operation.
During non-supply of water period, there is no heat dissipation takes place through
the cooler and hence load on generator shall be reduced. This is because of hot
air from water isolated cooler mixes with cold air coming from the other cooler in
normal operation. This resulting cold air temperature will be about 15% more
than that in normal operation.
Besides that, the prior Art also discloses a single row closed circuit air cooling
system is designed for a turbo-generator. The cold air is circulated across a row of
air to water heat exchangers, arranged in a row for heat-dissipation and the cold
air is brought back to the generator. The fans mounted on generator rotor
provide the head necessary for the above flow to take place. When a problem
detected in any of the heat exchangers, the machine will have to be shut down for
attending to the problems or for replacing the damaged element with a spare one.
OBJECTS OF THE INVENTION
It is, therefore an object of the present invention to propose an improve twin
cooler arrangement for improving air-cooed generator efficiency, which eliminates
the disadvantages of prior art.
A further Object of the present invention is to propose an Improve twin cooler
arrangement for improving air-cooled generator efficiency that helps the minimize
cold air inlet temperature substantially, when one of the coolers is engaged for in
situ repair.

A still further Object of the present invention is to propose an Improve twin cooler
arrangement for improving air-cooled generator efficiency, which advantageously
accommodates condensers in the available space, earmarked below the generator.
An yet further Object of the present invention is to propose an Improve twin
cooler arrangement for improving air-cooled generator efficiency which aims to
achieve 20 to 25% improvements in generator output.
Another Object of the present invention is to propose an Improved twin cooler
arrangement for improving air-cooled generator efficiency that helps in carrying
out maintenance operative in one row of coolers, while keeping the other row
operative.
A still another Object of the present invention is to propose an Improve twin cooler
arrangement for improving air-cooled generator efficiency, which can well utilized
the restricted space available in power plant by making alternative arrangement.
SUMMARY OF THE PRESENT INVENTION
The present Invention thus envisages arrangement of heat exchangers in two
rows is place of one row. The dimension of cooler element in the direction of flow
is also modified suiting to the available fan head. It was observed that the first
row of elements takes away 67% of heat load, while the second row contributes to
the remaining 33%. When a problem arises in any of the cooler elements, the
damaged element can be repaired by isolating those parts only from water supply.
The hot air coming from generator is cooled by the element placed in the other
row. Thus, the heat load of the twin cooler arrangement, thus will be reduced
from 100% in normal case to 67% of the load as per Invention in contrast to 0%
as per prior Art. As a result hot air to cold air mixture temperature on the
discharge side of coolers as per Invention will be less than that as per prior Art. It

is observed that present invention reduces the cold air temperature by about
8%. As a result, higher load can be drawn from the machine during the period of
cooler maintenance. An estimation of about 7% improvement on the machine
load is achieved by the new invention.
An example of a typical 100 MW load generator, an improvement in the machine
load was observed to an extent of 4.7 MW. In contrast to 67 MW as per prior
Art, up to 71 MW can be achieved when one cooler element is under
maintenance. Hence the present invention allows the improved machine
performance during cooler servicing.
A preventive maintenance plan is carried out by all power plants and a schedule
of periodic maintenance of all the coolers in the circuit is prepared. The time for
maintenance usually takes up about one to two days depending on site
constraints. After periodic maintenance, a gain of 4.7% in load for the generator
can be achieved.
The invention also optimizes the space required for the assembly of the total
cooler rack. This is advantageous when the rack is mounted below the
generator. In a refurbished job, condenser redesign requires additional space
and the intention is especially advantageous from the viewpoint of space.

Accordingly, there is provided a twin cooler arrangement for improving the
efficiency of air-cooled turbo generators, comprising:
a turbo-generator set (T) having two axial fans one each on either side,
one fan for drawing-in cold air from drive end and the other for drawing-in cold
air from non-drive end, the cold air getting heated during its flow across the
generator (T), the turbo-generator set (T) provided with a hot air channel, and
at least two cold air channels configured along the direction of said two axial
fans to form a closed air flow circular circuit; characterized by comprising:
a twin cooler arrangement configured in two rows comprising a plurality of
cooler elements, to cool the ingress hot air from the hot air channel by water and
the exhaust cold gas is allowed to pass through the cold air channels which is
drawn in by two fans, the cooling arrangement enabling reducing the
temperatu4e of the hot and cold air mixture at the discharge side of the
generator by removing heat from the hot air.

BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
A Turbo-generator set (T) comprising a generator stator frame (6) mounted on
two Bearings (5) rigidly fixed up by contrete slab (1) casting and surrounded by
two contrete wails (2) to form a closed path for air passage.
Two axial fans are mounted on the generator set (T) on its either end to drawn-in
cold air (8) from the cooler (4) and force the cold air (8) into the machine (T).
The cold air (8) circulated through the generator (T) internals absorbs the heat
generated there in and air becomes hot. The hot air is brought to the centre of
the generator (T) from which it emerges (7) and flow to flow the hot air (7) is
allowed through a channel covered by two partitioned walls (9). At the rear end of
the hot air (7) channel, two row of coolers (4) are provided, consisting of several
cooler element placed in row mounted on cooler supporting structure (3), which is
fastened to the concrete wall (2). The hot air (10) emerges from generator set (T)
is allowed to pass through cooler element (4) where the hot air dissipates its heat
to cooler tubes through which water flows internally. The exhaust air from the
cooler element is cold enough which is in turn flows through the cold air channel
(8) in the airflow circuit. The cooler assembly when mounted in two rows, the size
of the element in the direction flow is chosen such that the head required to
overcoming the pressure drop in taken care by the generator fans.

WE CLAIM:
1. A twin cooler arrangement for improving the efficiency of air-cooled turbo
generators, comprising:
a turbo-generator set (T) having two axial fans one each on either side,
one fan for drawing-in cold air from drive end and the other for drawing-in cold
air from non-drive end, the cold air getting heated during its flow across the
generator (T), the turbo-generator set (T) provided with a hot air channel, and
at least two cold air channels configured along the direction of said two axial
fans to form a closed air flow circular circuit; characterized by comprising:
a twin cooler arrangement configured in two rows comprising a plurality of
cooler elements, to cool the ingress hot air from the hot air channel by water and
the exhaust cold gas is allowed to pass through the cold air channels which is
drawn in by two fans, the cooling arrangement enabling reducing the
temperature of the hot and cold air mixture at the discharge side of the
generator by removing heat from the hot air.

2. A twin cooler arrangement for improving the efficiency of air-cooled of
turbo generator as substantially described herewith the reference to the
accompanying drawings.