FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
& The Patents Rules, 2003 As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
A fan enclosure for guiding external air into a heat exchanger of a CACA (closed air circuit air cooled) machine
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Mishra Neetendra Jogendra Nath of Crompton Greaves Ltd, M7, Bhopal, India and Pawar Sumedh Pundlik of Crompton Greaves Ltd, Analytics Department, CG Global R&D Centre, Kanjur (E), Mumbai 400042, Maharashtra, India, both Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to a fan enclosure for guiding external air into a heat exchanger of a CACA (closed air circuit air cooled) machine. BACKGROUND OF THE INVENTION
Heat generated from a CACA (closed air circuit air cooled) machine, such as a motor or generator, is cooled by an air-cooled heat exchanger mounted atop thereof. The hot air in the CACA machine is cooled when it comes in contact with the cool heat exchanger pipes filled with cool (external) air. A cooling fan mounted on the machine shaft sucks external cool air and guides it upstream into the pipes of the heat exchanger mounted atop the machine. Such guiding is by means of a fan enclosure, as shown in Fig 1, which covers the fan and the side of the heat exchanger. The front wall 2 of the fan enclosure facing fan blades is provided with air openings 3 through where it sucks external air. Angular plates 6 & 7 are held between the sidewalls 8 & 9 of the enclosure and projects into the lumen of the enclosure such that the topmost angular plate 6 is closest to the front wall 2 of the enclosure and the bottommost angular plate 7 near the motor is farthest from the front wall 2 of the enclosure. No back wall between side walls 8 & 9 is provided in the enclosure. The side walls 8 & 9 are mounted to the heat exchanger such that the angular plates 6 & 7 remain disposed between the heat exchange and the front wall 2. The back wall 3 of the enclosure disposed below the heat exchanger extends into the enclosure defining a throat portion 10. Because of the above design, external air is distributed non-uniformly in the heat exchanger. The throat section 10 and the positioning of the angular plates 6 & 7 pushes a majority of the external air sucked in the enclosure to the top portion of the enclosure leaving very little external air in the lower portion of the enclosure.

Therefore, heat exchanger pipes opening in the top portion of the enclosure receive more cool air as compared to the pipes opening in lower portion of the enclosure near the motor. Cooling efficiency of the CACA machine is thereby less. OBJECTS OF THE INVENTION
An object of the invention is to provide a fan enclosure in a CACA (closed air circuit air cooled) machine which uniformly distributes external air in the heat exchanger thereof thereby providing better cooling efficiency.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, there is provided a fan enclosure for guiding external air into a heat exchanger of a CACA (closed air circuit air cooled) machine, the heat exchanger mounted atop the machine, the external air sucked in the enclosure by a cooling fan mounted on one end of the machine shaft protruding from the machine, the enclosure comprising a bottom portion, middle portion and a top portion, the bottom and middle portion defined by their corresponding back walls and front walls, the top portion having a front wall and no back wall, the enclosure being disposed over the cooling fan such that the fan blades remaining disposed between the back and front walls of the bottom portion, the back wall of the bottom portion having a hole for receiving the machine shaft there through, the front wall of the bottom portion facing the fan blades and having air openings for receiving external air there through; the front wall of the middle and top portions being common and extending slopingly upwardly from the front wall of the bottom portion to merge with the free ends of the side walls of the top portion, the edges of the side walls mounted to the heat exchanger such that the front wall faces a side wall of heat exchanger having heat exchanger pipe openings; the middle portion remaining disposed below the heat exchanger, the back wall of the middle portion defining a concavity therein, the

middle portion comprising at least one upstanding member held between the front and back walls thereof.
Preferably, the air opening on the front wall of the bottom portion is circular. Three upstanding members are provided in the middle portion. Baffles are provided in the bottom portion in the radial path of the cooling fan. The common front wall of the middle and top portion is elliptical.
These and other aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying drawings and appended claims, in which,
Fig 1 is an isometric view of a prior art fan enclosure for guiding external air into a heat exchanger of a CACA (closed air circuit air cooled) machine.
Fig 2 is an isometric view of a fan enclosure for guiding external air into a heat exchanger of a CACA (closed air circuit air cooled) machine.
Fig 3 is a side view of a fan enclosure for guiding external air into a heat exchanger of a CACA (closed air circuit air cooled) machine.
Fig 4 is a back view of a fan enclosure for guiding external air into a heat exchanger of a CACA (closed air circuit air cooled) machine.
Referring to figures 2-4, the fan enclosure for guiding external air into a heat exchanger of a CACA (closed air circuit air cooled) machine comprises of a bottom portion 15, middle portion 16 and a top portion 17. The bottom and middle portions are defined by their respective back walls 18 & 19 and front walls 21 & 22. The top portion 17 is having a front wall 23 and no back wall,The bottom portion 15 is a substantially circular structure except for the portion connected to the middle portion 16 of the enclosure which has a flat horizontal surface. The back wall 18 of the bottom portion 15 comprises a hole 24 at its centre and is mounted to the machine

(not shown) such that a portion of the CACA machine shaft (not shown) is received in the enclosure through the hole 24. A cooling fan (not shown) of the CACA machine is disposed on the machine shaft in the enclosure such that it remains disposed between back 18 and front 21 walls of the bottom portion 15. The rotating machine shaft rotates the cooling fan which sucks external air axially into the enclosure through the air openings 25 provided on the front wall 21 of the bottom portion 15. Almost all external air sucked in the bottom portion 15 is guided into the middle portion 16 (located below the heat exchanger (not shown) mounted atop the CACA machine) on account of the back wall 18 and the bottom area of the bottom portion 15 provided blocked. Baffles 26 are provided on the radial path of the cooling fan in the bottom portion 15. The size of the middle portion 16 is substantially small compared to the size of the bottom 15 and top 17 portions. The back wall 19 of the middle portion 16 is bulged to provide a concavity 27 in the middle portion 16. Two upstanding members 28 are provided in the middle portion 16 along the width thereof in a spaced apart relationship with each other. The upstanding members 28 are held against the back 19 and front walls 22 of the middle portion 16, therefore dividing the middle portion 16 into three compartments. The front and back edges of the upstanding members 28 are contoured to fit perfectly against the front 22 and back 19 walls of the middle portion 16. The upstanding members 28 aid in uniformingly distributing the external air along the width of the middle portion 16. The front wall 22, 23 of the middle and top portion 16 & 17 is common and elliptical in shape which extends slopingly upwardly from the front wall 21 of the bottom portion 15 to meet with the free ends of the side walls 20a & 20b of the top portion 17. The edges of the side walls 20a & 20b are mounted to the edges of the front and back walls of the heat exchanger respectively such that the front wall 23 faces a side wall of the heat

exchanger having heat exchanger pipe openings (not shown). External air received in the top portion 17 through the bottom 15 and middle 16 portions is guided into the heat exchanger pipes through such pipe openings.
The external air is sucked in the enclosure by the cooling fan. Owing to the absence of any constricted space presence of a large concavity 27 with increased volume therein in the middle section 16, a majority of the sucked air is no further reflected upstream and a good amount thereof flows into the concavity 27 of the middle portion 16. Moreover, the upstanding members 28 aid in distributing the external air equally along the width of the middle portion 16. The velocity of air flowing into the middle portion 16 decreases substantially thereby inhibiting their further upstream movement. Consequently, such air enters the heat exchanger pipes in the top portion 17 just above the middle portion 16. Sufficient flow of external air into the heat exchanger pipes opening in the upper/topmost section of the top portion 17 was never a problem. Therefore, a near uniform distribution of air in the entire heat exchanger is achieved thereby rendering the cooling by the heat exchanger more efficient.
The enclosure may be made up of any material such as plastic, metal etc. The front wall of the middle and top portion may not be necessarily elliptical. The air openings may be of any size and shape. The shape of the bottom portion may not be necessarily circular. The enclosure may or may not be mounted on the shaft. The hole on the back wall of the bottom portion is only for receiving the shaft there through. No air is to be allowed to be leaked there through. Baffles may or may not be provided on the radial path of the fan in the bottom portion. The shape of the upstanding members and the amount of clearance between them may be different that that of shown in the figure.

Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the scope of the invention as defined in the appended claims.

We claim:
1. A fan enclosure for guiding external air into a heat exchanger of a CACA (closed air circuit air cooled) machine, the heat exchanger mounted atop the machine, the external air sucked in the enclosure by a cooling fan mounted on one end of the machine shaft protruding from the machine, the enclosure comprising
a. a bottom portion, middle portion and a top portion, the bottom and middle portion defined by their corresponding back walls and front walls, the top portion having a front wall and no back wall, the enclosure being disposed over the cooling fan such that
i. the fan blades remaining disposed between the back and front
walls of the bottom portion, the back wall of the bottom portion

having a hole for receiving the machine shaft there through, the front wall of the bottom portion facing the fan blades and having air openings for receiving external air there through; the front wall of the middle and top portions being common and extending slopingly upwardly from the front wall of the bottom portion to merge with the free ends of the side walls of the top portion, the edges of the side walls mounted to the heat exchanger such that the front wall faces a side wall of heat exchanger having heat exchanger pipe openings; ii. the middle portion remaining disposed below the heat exchanger, the back wall of the middle portion defining a concavity therein, the middle portion comprising at least one

upstanding member held between the front and back walls thereof.
2. The cooling fan enclosure as claimed in claim 1, wherein baffles are provided in the bottom portion in the radial path of the cooling fan,
3. The cooling fan enclosure as claimed in claim 1, wherein the common front wall of the middle and top portion is elliptical.