FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
An outer silencer mechanism for heat exchangers.
APPLICANTS :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S):
Pangal Sarvesh and Bhandakkar Parag; both of Crompton Greaves Ltd, Large & Traction Machines Division, D5, Industrial Area MPAKVN, Mandideep, 462046, Madhya Pradesh, 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 the field of mechanical assemblies.
Particularly, this invention relates to the field of heat exchangers and motors.
Still particularly, this invention relates to an outer silencer mechanism for heat
exchangers.
Background of the Invention:
A motor typically includes a rotor, a stator and associated assemblies, which assemblies are heat generating assemblies. There is a need to dissipate the heat for long life of the motor and so that the motor works according to specified standard.
There is, hence, provided a heat exchanger mechanism adapted to receive hot air from the motor. A fan is driven to extract relatively cold air from the surrounding atmosphere into the heat exchanger. Guided through the conduits of the fan cover having intermittent baffles, the relatively cold air comes into contact with the hot air from the motor at the tubes, and effective cooling of the ambient air around the motor and in the motor housing is carried out. The previously relatively cold air, records an increase in temperature due to transfer of heat.
This residual relatively hot air, now, has to be exited through the heat exchanger. During exiting these gases / air, pressure is created which may lead to turbulence and vortex formation due to the rough nature of the exit path. The air flow is not contoured and is abrupt, which leads to misguided exit along with backflow. When the air exits from the tubes the noise that is generated is due to air impinging on the

internal surfaces of the tubes and the fan cover, in addition to the noise generated by the fan. This leads to increase in pressure and noise during air exit. Further, it regurgitates on the continuous flow of air that is supposed to be exited, thus, decreasing throughput of air cooling and heat exchange.
There is a need to obviate the limitations of the prior art.
Prior Art:
JP53037804 discloses a Ventilating Cooler with Mufflers. It discloses the concept of reduction in noise without increasing ventilating resistance by thickening the thickness of sound absorbing material which is sealed on at least a part tithing the exhaust port of a muffler.
However, air guidance is not disclosed leading to ineffective sound absorption in this prior art.
Objects of Invention:
An object of the invention is to provide an improved noise control device (silencer mechanism) in induction air cooled motor for reducing the noise level and temperature rise in the motors.
Another object of the invention is to provide an improved noise control device (silencer mechanism) in induction air cooled motor which saves energy losses during air movement.

Yet another object of the invention is to provide an improved noise control device in induction air cooled motor which noise control device (silencer mechanism) has low maintenance.
Still another object of the invention is to provide an improved noise control device in closed air circuit air cooled motor which noise control device (silencer mechanism) has new aerodynamic baffle to control noise.
An additional object of the invention is to an improved noise control device for exiting the gases from a heat exchanger associated with a motor.
Yet an additional object of the invention is to provide optimum mass air flow through and out of a heat exchanger without compromising on motor life or motor working parameters.
Still another object of the invention is to provide optimum noise reduction while guiding air out of heat exchanger.
Yet another object of the invention is to efficiently guide air out of said heat exchanger.
Summary of the Invention:
According to this invention, there is provided an outlet silencer mechanism for heat exchangers, said mechanism comprises:
a. trapezoidal housing with a front flanged open face adapted to be fitted in line with said heat exchanger, said open face adapted to receive relatively hot air

from said heat exchanger which is guided out into ambient (relatively colder) atmosphere through said housing, each of said side walls being a trapezoidal side wall, thereby providing a protruding path from entry to exit of the air from the heat exchanger, with the entry face of said housing being relatively smaller than the back face of said housing, thereby providing room for air flow;
b. open faced lateral side walls adapted to allow exit of air through said
housing; and
c. curvilinear diffuser barrier adapted to guide air through said side walls in a
streamlined fashion.
Additionally, said housing includes an open faced dorsal wall and an open faced ventral wall to allow exit of air through said housing.
Typically, said housing is an internally foam walled housing.
Preferably, said housing is an internally PU foam walled housing.
Typically, said curvilinear diffuser barrier is a wave shaped curvilinear diffuser barrier with two laterally sloping edges.
Alternatively, said curvilinear diffuser barrier is a wave shaped curvilinear diffuser barrier with four circumferentially placed sloping edges.

Brief Description of the Accompanying Drawings:
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates a schematic motor and heat exchanger along with an outlet silencer mechanism;
Figure 2 illustrates a front view of the outlet silencer mechanism;
Figure 3 illustrates an isometric view of the outlet silencer mechanism;
Figure 4 illustrates a side view of the outlet silencer mechanism;
Figure 5 illustrates a top view of the outlet silencer mechanism; and
Figure 6 illustrates a back view of the outlet silencer mechanism.
Detailed Description of the Accompanying Drawings:
According to this invention, there is provided an outlet silencer mechanism for heat exchangers.
Figure 1 illustrates a schematic motor and heat exchanger along with an outlet silencer mechanism (100).

A motor (12) is associated with a heat exchanger (14) which is placed operatively above it. The relatively hotter air from the motor rises towards the heat exchanger, where it is cooled due to the heat exchanging mechanism, and relatively colder air from the heat exchanger settles downwards towards the motor placed operatively beneath it. This action of rising and rotation of the air is propelled by internal fans (16,18).
The heat exchanger, mentioned and used herein, is an air-cooled heat exchanger.
An external fan (20) which propels the movement of ambient air towards the heat exchanger in order to continuously supply the tubes of the heat exchanger (14) with relatively colder air is placed co-axial to the motor. As the motor works, a common shaft hoisting the rotor of the motor and the external fan rotates, thereby pressing them into action simultaneously.
In the heat exchanger, the ambient relatively colder air cools settles towards the motor, downwards. And the residual relatively hot air needs to be guided out of the heat exchanger. This guiding of air through the outlet (100) creates a point of turbulence. The density of hot air is more, and as it is released to the cold air, its density decreases over a period of time. This change in density causes turbulence and noise at the exit / outlet.
Figure 2 illustrates a front view of the outlet silencer mechanism. Figure 3 illustrates an isometric view of the outlet silencer mechanism. Figure 4 illustrates a side view of the outlet silencer mechanism. Figure 5 illustrates a top view of the

outlet silencer mechanism. Figure 6 illustrates a back view of the outlet silencer mechanism.
In accordance with an embodiment of this invention, there is provided a trapezoidal housing (30) with a front flanged open face (21) adapted to be fitted in line with the heat exchanger (14). The open face receives relatively hot air from the heat exchanger which is to be guided out into the ambient (relatively colder) atmosphere. All the side walls of the trapezoidal housing are trapezoidal in shape, thereby providing a protruding path from entry to exit of the air from the heat exchanger.
The trapezoidal housing is of a pre-determined length, which allows the air to pass through an intermediate channel (housing) where the air assumes its relatively dense state since it tries to lose temperature from the relatively hot heat exchanger to the relatively cold ambient atmosphere. In this change of density, the mass of air also changes, and the trapezoidal housing accommodates the change of mass before it is released to the atmosphere. The entry face of the housing is relatively smaller than the back face, thereby providing room for air flow without causing turbulence or vortices. The change in density reflects in change in velocity. When air exits from the tubes in the heat exchanger, the velocities are quite high (typically, in the order of 15-20 m/s). When this high velocity air impinges to a static structural element, it creates noise, as seen in the prior art, which adds to the overall noise of the motor. By providing a larger surface area for the relatively hot air to recover, the change in velocity is also relatively gradual, thereby preventing a gush of air causing noise to be substantially reduced.

Preferably, the air is allowed to exit from lateral side walls (22, 24) which are open faced.
Alternatively, the dorsal wall (26) and ventral wall (28) may also be opened up to allow exit of air.
The formation of turbulence is a major cause of noise. This silencer mechanism, according to another embodiment of this invention, also includes a curvilinear diffuser barrier (40) adapted to guide air through the side openings (22, 24). The curvilinear barrier spreads the air gradually in a streamlined fashion, so that turbulence is reduced and air flow is laminar. Turbulence, in the air adds to the noise, so avoiding the same helps reducing this effect.
In accordance with yet another embodiment of this invention, all the internal portions of the silencer are lined with a noise damping material. Preferably, said noise damping material is PU foam. According to one embodiment, this foam is 50mm thick and has high noise reduction characteristics. When the air exits the heat exchanger and impinges on the foam, majority of the noise is absorbed by this material. Air escapes smoothly from the silencer since its being guided by the smooth contour of the internal barrier. This helps in a low turbulent air with low noise content.
In an exemplary embodiment, it was observed, that an overall 3 db reduction of noise was achieved due to the introduction of the special outlet silencer.

While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. An outlet silencer mechanism for heat exchangers, said mechanism comprising:
a. trapezoidal housing with a front flanged open face adapted to be fitted in line
with said heat exchanger, said open face adapted to receive relatively hot air
from said heat exchanger which is guided out into ambient (relatively
colder) atmosphere through said housing, each of said side walls being a
trapezoidal side wall, thereby providing a protruding path from entry to exit
of the air from the heat exchanger, with the entry face of said housing being
relatively smaller than the back face of said housing, thereby providing room
for air flow;
b. open faced lateral side walls adapted to allow exit of air through said
housing; and
c. curvilinear diffuser barrier adapted to guide air through said side walls in a
streamlined fashion.
2. A mechanism as claimed in claim 1 wherein, said housing includes an open faced dorsal wall and an open faced ventral wall to allow exit of air through said housing.
3. A mechanism as claimed in claim 1 wherein, said housing is an internally foam walled housing.
4. A mechanism as claimed in claim 1 wherein, said housing is an internally PU foam walled housing.

5. A mechanism as claimed in claim 1 wherein, said curvilinear diffuser barrier is a wave shaped curvilinear diffuser barrier with two laterally sloping edges.
6. A mechanism as claimed in claim 1 wherein, said curvilinear diffuser barrier is a wave shaped curvilinear diffuser barrier with four circumferentially placed sloping edges.