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 improved heat exchanger with aerodynamic tubes
APPLICANTS (S)
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company.
INVENTOR (S)
Saxena Amrita; of Crompton Greaves Limited, Machine (M7) Division, D-5 Industrial Area, MPAKVN, Mandideep - 462046, Madhya Pradesh, India; an Indian National.
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 electrical machines and equipment.
Particularly, this invention relates to the field of motors with corresponding heat exchangers.
More particularly, this invention relates to an improved heat exchanger with aerodynamic tubes.
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.
Motors may be Closed Air Circuit Water Cooled (CACW), Closed Air Circuit Air Cooled (CACA) motors, High Tension (HT) motors, or Low Tension (LT) motors. Motors are susceptible to generate heat during its operative configuration. Due to the power it generates, heat output is a byproduct of the motor mechanism.
It is important that this generated heat i.e. hot air is guided appropriately away from the motor. For efficient working of motors, it is imperative that this byproduct of heat does not increase beyond defined thresholds. Hence, a ventilating or cooling system for such motors is necessary.
Heat Exchangers are deployed for efficient heat transfer from one medium to another. A fan is driven to extract relatively colder air from the surrounding

atmosphere into the heat exchanger. Guided through the conduits of the fan cover, the relatively colder air comes into contact with the relatively hotter air of the motor at the tubes, and the heat of the motor in the motor housing is carried out and effective cooling is done. Hence, relatively colder air records an increase in temperature due to transfer of heat. This hot air, now, is then exited through the heat exchanger in the surroundings.
Further, hot air from the motor and its surroundings elevate towards the heat exchangers, and passes through the gaps defined between the heat exchanger tubes. According to the prior art, this internal air encounters the circular or quadrangular cross section of the heat exchanger tubes which provide a certain resistance to the air flow of the internal air. These may not be the most optimum designs in the path of motion of the internal hot air. Due to this resistance, most of the internal air is not able to reach the top of the heat exchanger. Hence, the utilization of the heat exchanger is not up to its expectations.
There is a constant endeavour to improve the heat transfer characteristics in the heat exchanger such that efficient heat transfer occurs in the heat exchanger within the given length of the heat exchanger and the tubes which comprise the heat exchanger. There is a need for an improved profile of heat exchanger tubes in order to alleviate the path of least resistance for internal hot air from the motor towards the heat exchangers.
OBJECTS OF THE INVENTION:
An object of the invention is to provide improved or relatively increased heat dissipation with respect to a motor.

Another object of the invention is to provide a heat exchanger which allows improved cooling or heat transfer characteristics.
Yet another object of the invention is to provide higher ratings for motor due to increased heat dissipation capacity of an associated heat exchanger.
Still another object of the invention is to provide improved ventilation characteristics of a heat exchanger.
An additional object of the invention is to provide enhanced circulation of internal air through heat exchanger tubes.
Yet an additional object of the invention is to alleviate the path of least resistance for internal hot air from the motor towards the heat exchangers.
Still an additional object of the invention is to provide uniform utilization of the heat exchanger.
SUMMARY OF THE INVENTION:
According to this invention, there is provided an improved heat exchanger comprises a plurality of tubes bundled together in a parallel configuration with respect to each other in order to allow entry of air from one end of the tubes and exit of air from the other end, characterised in that, each of said tubes include a sector-shaped or almond-shaped cross-section.
Typically, said sector-shaped or almond-shaped cross-sectioned tubes comprises a pair of adjacent elongate flat surfaces converging at their operative bottom end and

diverging at their operative top ends, in that, the diverged operative top ends are connected by an elongate arced surface.
Typically, the linear edges formed by the convergence of tapering edges of each of said sector-shaped or almond-shaped cross-sectioned tubes are parallel to each other and are parallel to the heat exchanger assembly.
Typically, each of said tubes is made of a metal or other material with a high coefficient of heat transfer.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a heat exchanger tube of a heat exchanger assembly of the prior art;
Figure 2 illustrates a side view of a heat exchanger assembly; and
Figure 3 illustrates an isometric view of a heat exchanger assembly.
The invention will now be described in relation to the accompanying drawings, in which:
Figures 4a and 4b illustrate various views of a heat exchanger tube of a heat exchanger assembly;
Figure 5 illustrates an isometric view of the sector-shaped or almond-shaped tube of the heat exchanger assembly;

Figure 6 illustrates a cross-section view of sector-shaped or almond-shaped tube heat exchanger; and
Figure 7 illustrates the direction of air flow (shown by arrows) aided by the design of the new heat exchanger tubes.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a heat exchanger tube of a heat exchanger assembly of the prior
art.
Figure 2 illustrates a side view of a heat exchanger assembly.
Figure 3 illustrates an isometric view of a heat exchanger assembly.
According to the prior art design, a heat exchanger (as referenced by numeral 150 in Figures 2 and 3 of the accompanying drawings) was comprised of a plurality of uniform or straight parallel aligned tubes (as referenced by numeral 100 in Figure 1 of the accompanying drawings). These tubes, as shown, have a circular cross-section.
Air flowing externally to these tubes, i.e. the internal hot air from the motor is impeded by the tubes of the prior art design. Thus, the heat exchanger is not optimally used. I.e. the lower part of the heat exchanger which is overused is relatively hotter than the upper part which is underused.
According to this invention, there is provided an improved heat exchanger.
Figures 4a and 4b illustrate various views of a heat exchanger tube of a heat exchanger assembly.

Figure 5 illustrates an isometric view of the sector-shaped or almond-shaped tube of the heat exchanger assembly;
In accordance with an embodiment of this invention, there are provided a plurality of tubes (200) with an almond-shaped cross section. The almond-shaped cross-section is formed by two tapering converging sides such that they converge at their operative lower ends and the diverged upper ends are connected by an arc. The almond-shaped cross-section can also be described as a sector of a circle.
From the operative bottom side, the adjacent edges are divergent. The diverging nature provides an aerodynamic pattern for the air flow, and restricts impedance in the path of the air flow. Thus, the throughput of air from the operative bottom side to the operative upper side increases. Relatively more air passes from the bottom to top and the heat exchanger is effectively and optimally utilized.
Due to this formation, turbulence is reduced. And a smooth and laminar air flow is obtained from the operative lower side to the operative upper side.
By introducing these almond-cross-sectioned or sector-cross-sectioned tubes in heat exchanger it is possible to increase heat transfer and achieve better cooling with respect to the internal air rising from the motor towards the heat exchanger.
Also, this results in increase in surface area of the tubes with which the internal air comes into contact while moving in the upward direction. Thus, the heat exchanger saturation point is relatively prolonged.
Figure 6 illustrates a cross-section view of almond-cross-sectioned or sector-cross-sectioned tubes heat exchanger.

Figure 7 illustrates the direction of air flow (shown by arrows) aided by the design of the new heat exchanger tubes.
The technical advancement of this invention lies in provisioning of a cross-section which is in the form of a sector of a circle, due to which the tapering ends provide an aerodynamic air flow (without resistance) from an operative lower direction to an operative upper direction, thereby passing the air, without obtrusion. This results in better heat transfer, ventilation, and cooling through circulation due to creation of turbulence.
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 improved heat exchanger comprising a plurality of tubes bundled together in a parallel configuration with respect to each other in order to allow entry of air from one end of the tubes and exit of air from the other end, characterised in that, each of said tubes include a sector-shaped or almond-shaped cross-section.
2. An improved heat exchanger as claimed in claim 1 wherein, said sector-shaped or almond-shaped cross-sectioned tubes comprising a pair of adjacent elongate flat surfaces converging at their operative bottom end and diverging at their operative top ends, in that, the diverged operative top ends are connected by an elongate arced surface.
3. An improved heat exchanger as claimed in claim 1 wherein, the linear edges formed by the convergence of tapering edges of each of said sector-shaped or almond-shaped cross-sectioned tubes are parallel to each other and are parallel to the heat exchanger assembly.
4. An improved heat exchanger as claimed in claim 1 wherein, each of said tubes is made of a metal or other material with a high coefficient of heat transfer.