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
Exhaust assembly for circular radiators
APPLICANTS :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S):
Paramane Sachin and Joshi Kishor, both of Crompton Greaves Ltd, Analytics Centre, C G Global R&D Centre, Kanjurmarg (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 the field of electrical equipment.
Particularly, this invention relates to the field of transformers, radiators and heat exchangers.
Specifically, this invention relates to exhaust assembly for circular radiators in ONAN condition.
BACKGROUND OF THE INVENTION:
A transformer is an electric device which transfers current from one circuit to another with or without affecting its magnitude. It includes electro-mechanical assemblies such as copper windings immersed in oil.
Power transformers rated up to a few KVA can be adequately cooled by natural convective air-cooling, sometimes assisted by fans. Some power transformers are immersed in specialized transformer oil that acts both as a cooling and insulating medium, thereby extending the lifetime of the insulation transformer. The transformers get heated due to iron and copper losses occurring in them. It is necessary to dissipate this heat so that the temperature of the winding is kept below the value at which the insulation begins to deteriorate. For efficient working of the transformer, it is required to maintain the temperature of the oil, which in turn maintains the temperature of the components of the transformer.

Another type of cooling provided for transformers is by means of external associated auxiliary equipment such as heat exchangers, radiators, or the like. There are straight radiators, circular radiators, and the like equipment that may be associated with the transformer cooling.
In the case of a radiator, pipes connect the transformer to an adjacently located radiator. These pipes conduct oil from the transformer to the radiator, where they are cooled, and back again to the transformer.
The radiator may include pipe windings and heat exchange principles to regulate the temperature of oil from its relatively heated state to its relatively optimum working temperature.
The radiator may be equipped with a fan, at its operative base, in order to blow out hot air from its fins. However, it has been observed, in the cases of circular radiators, that hot air is present in the crevices or area adjacent the inner diameter of the radial fins. This results in higher radiator temperature in that area and impedes the heat transfer from radiator to atmosphere resulting in lower thermal performance.
The radiators of the prior art do not provide optimum solutions taking into consideration the parameters relating to fluid flow, pressure drop, and heat transfer.
There is a need to consider radiators and exhaust mechanisms as a single integrated unit and to consider the effect of both on heat transfer.

Hence, there is a need for an external mechanism to provide an exhaust route or aid in heat dissipation, especially at the inner problem areas.
OBJECTS OF THE INVENTION:
An object of the invention is to reduce radiator temperature.
Another object of the invention is to reduce radiator temperature in Oil Natural Air Natural (ONAN) condition.
Yet another object of the invention is to improve heat transfer performance and process of radiator.
Still another object of the invention is to improve the thermal design for radiator.
An additional object of the invention is to provide improved flow distribution over the radiators associated with electrical equipment such as transformers.
SUMMARY OF THE INVENTION:
According to this invention, there is provided an exhaust assembly for circular
radiators having radial fins, said exhaust assembly comprises:
an external fan co-axially located at the operative top of said circular radiator for
aiding heat dissipation at the inner diameter of said radial fins of said circular
radiators.
Typically, said fan is a collector-mounted fan.

Typically, the area demarcated by said inner diameters is within the area defined by said collector ring, thereby mapping the fan on to the operative area within said collector ring.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a straight radiator used in transformer cooling.
The invention will now be described in relation to the accompanying drawings, in which:
Figure 2 illustrates a circular radiator used in transformer cooling;
Figure 3 illustrates a CFD analysis of the circular radiator at a plane passing through;
Figure 4 illustrates a line diagram of an isometric view of a circular radiator with air exhaust assembly; and
Figure 5 illustrates a line diagram of a top view of a circular radiator with air exhaust assembly.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a straight radiator used in transformer cooling. This is represented by reference numeral 100.

According to this invention, there is provided an exhaust assembly for circular radiators in ONAN condition.
Figure 2 illustrates a circular radiator (200) used in transformer cooling. The circular radiators, and its associated cooling / exhaust mechanisms are the subject matter of this invention.
Currently, natural convection of air is used for cooling of radiator in Oil Natural Air Natural (ONAN) configuration. There is hot air at inner diameter of circular radiators which is not removed efficiently in the existing case and impedes the heat transfer process.
Presence of hot air at inner diameter (12) of circular radiators can be best visualized using CFD (Computational Fluid Dynamics) analysis. Reference numeral 14 represents zones of high temperatures in the CFD analysis of the circular radiator of Figure 2.
Reference numeral 16 represents a collector ring which is substantially co-axial with the fins (18) of the circular radiator. The collector ring receives oil that is to be cooled from an associated transformer. Although, radial fans (20) are placed at the operative bottom of each circular radiator, they do not provide for exhaust of hot air from the inner diameters represented by reference numeral 12.
Figure 3 illustrates a CFD analysis of the circular radiator at a plane passing through. It can be seen that there is relatively higher temperature (depicted by red zones - 14) at the inner diameters (12) of the radial fins of the circular radiator.

Figure 4 illustrates a line diagram of an isometric view of a circular radiator (200) with air exhaust assembly (300).
Figure 5 illustrates a line diagram of a top view of a circular radiator (200) with air exhaust assembly (300).
In accordance with an embodiment of this invention, there is provided an external fan (300) co-axially located at the operative top of the circular radiator. Typically, the fan is a collector-mounted fan. i.e. the fan is typically installed on the collector. The area (12) demarcated by the inner diameters is within the area defined by the collector ring. Hence, the operative area of the fan maps on to the operative area within the collector ring.
This external fan is a rotating member and is worked / rotated due to wind velocity and does not use any conventional energy source such as electricity. It sucks out hot air from the zone near the internal diameters of the radial fins which was an earlier avoided and problem zone and releases it to the atmosphere, thereby aiding heat dissipation and improving the thermal design parameters of the circular radiator.
This design and arrangement results in lower top oil temperature results in lower insulation temperature and increases the life of the associated transformer. Further, for same temperature, lesser number of radiator fins can be used and also reduces the weight of the transformer.

It has been observed that even IK reduction in top oil temperature results in 1% extra loading of transformer. Therefore, life of transformer is improved as insulation life can be increased due to lower insulation temperature.
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 exhaust assembly for circular radiators having radial fins, said exhaust
assembly comprising;
an external fan co-axially located at the operative top of said circular radiator for aiding heat dissipation at the inner diameter of said radial fms of said circular radiators.
2. An exhaust assembly for circular radiators as claimed in claim 1 wherein, said fan is a collector-mounted fan.
3. An exhaust assembly for circular radiators having radial fins, said exhaust assembly comprising:
an external fan co-axially located at the operative top of said circular radiator for aiding heat dissipation at the inner diameter of said radial fins of said circular radiators such that the area demarcated by said inner diameters is within the area defined by said collector ring, thereby mapping the fan on to the operative area within said collector ring.