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
A system and a method for designing radiator equipment
APPLICANTS :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S):
Paramane Sachin Bhimarao, of Crompton Greaves Ltd, Analytics Centre, CG Global R&D Centre, Kanjur Marg (East) Mumbai - 400 042, Maharashtra, India; an Indian National, Veken Wim Van der and Landtmeters Nico, both of CG Power Systems, Belgium NV Antwerpsesteenweg 167, B-2800 Mechelen, Belgium, both Belgian Nationals; and Joshi Kishor Uddhav of Crompton Greaves Ltd, Analytics Centre, CG Global R&D Centre, Kanjur Marg (East) Mumbai - 400 042, Maharashtra, 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:
The invention relates to the field of radiator cooling equipment.
Particularly, this invention relates to a system and a method for designing radiator equipment.
BACKGROUND OF THE INVENTION:
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact. They are widely used in refrigeration, air conditioning, power plants, motors, transformers, and the like equipment.
Radiators are heat exchangers used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in automobiles, buildings, and electronics. The radiator is always a source of heat to its environment, although this may be for either the purpose of heating this environment, or for cooling the fluid or coolant supplied to it, as for engine cooling.
In transformers, high temperatures will damage the winding insulation. Small transformers do not generate significant heat and are cooled by air circulation and radiation of heat. Power transformers rated up to several hundred kVA can be adequately cooled by natural convective air-cooling, sometimes assisted by fans. In larger transformers, part of the design problem is removal of heat. Some power transformers are immersed in transformer oil that both cools and insulates the windings. The oil-filled tank often has radiators through which the oil circulates by

natural convection; some large transformers employ forced circulation of the oil by electric pumps, aided by external fans or water-cooled heat exchangers.
For designing such fans and radiators, empirical formulae have been used. This designing methodology has limited capability outside the range they have been derived. However, there are certain pre-defined assumptions that are made during this designing, and hence, the accuracy of designing and subsequent radiator design is relatively less. The design methodology is used for development of correlation for velocity and Nusselt number along the height of radiators of a transformer. [In heat transfer at a boundary (surface) within a fluid, the Nusselt number is the ratio of convective to conductive heat transfer across (normal to) the boundary]. The methodology is adapted to calculate the velocity and the Nusselt number when parameters of radiator and fans are given to a system (using the methodology) as input parameters. As an output, there is obtained an optimised number of fans and radiators for given heat dissipation.
OBJECTS OF THE INVENTION:
An object of the invention is to improve performance of a transformer and radiator by providing relatively better prediction of velocity of air.
Another object of the invention is to improve performance of a transformer and radiator by providing relatively better prediction of Nusselt number.
Yet another object of the invention is to provide optimum selection of radiator-fan configuration.

Still another object of the invention is to have a relatively improved correlation for velocity and heat transfer for selection of right configuration of radiator-fan for particular design of transformer.
An additional object of the invention is to avoid non-conformities in test bay during testing of designed radiators of transformers according to previous systems and methodologies.
Yet an additional object of the invention is to allow transformer-radiator design with smaller safety margins on temperature.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a system for designing radiator equipment, said system comprises:
a. first input means adapted to provide radiator height input;
b. second input means adapted to provide number of segments into which said
radiator height is to be divided;
c. dividing means adapted to divide said first input radiator height into a
plurality of equidistant smaller segments based on said second input, thereby
defining segment height;
d. third input means adapted to input fan speed in relation to said radiator;
e. velocity computation means adapted to compute velocity, at each of said
divided segment heights, based on defined segment height, third input fan
speed and pre-defined mathematical model; and
f. designing means adapted to provide a design of said radiator based on said
computed velocity at each of said divided segment heights depending upon

pre-defined parameters, thereby obtaining an optimum design of said radiator.
Typically, said velocity computation means includes a pre-defined mathematical model based on the formula:

According to this invention, there is also provided a method for designing radiator equipment, said method comprises the steps of: i. inputting a first input of radiator height; ii. inputting a second input of number of segments into which said radiator
height is to be divided; iii. dividing said first input radiator height into a plurality of equidistant smaller
segments based on said second input, thereby defining segment height; iv. inputting a third input of fan speed in relation to said radiator; v. computing velocity, at each of said divided segment heights, based on
defined segment height, third input fan speed and pre-defined mathematical
model; and vi. designing said radiator based on said computed velocity at each of said
divided segment heights depending upon pre-defined parameters, thereby
obtaining an optimum design of said radiator.
Typically, said step of computing velocity includes the step of computing velocity based on a pre-defined mathematical model which is based on the formula:


BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a schematic of a radiator fan on a stand simulating a radiator-single-fan assembly for CFD analysis;
Figure 2 illustrates a CFD analysis of the radiator-single-fan assembly of Figure 1;
Figure 3 illustrates a transformer with side plates and fans;
Figure 4 illustrates a CFD analysis for the transformer - fan assembly of Figure 3, thereby showing velocity contours along different heights of the radiator;
Figure 5a illustrates a CFD analysis depicting velocity contour at pre-defined heights for a one radiator - two fan assembly;
Figure 5b illustrates a CFD analysis depicting velocity contour at pre-defined heights for a three radiator - six fan assembly;
Figure 5c illustrates a CFD analysis depicting velocity contour at pre-defined heights for a five radiator - ten fan assembly;
Figure 6 illustrates Nusselt number variation along the height of a radiator; and

Figure 7 illustrates the differential velocity of air through a radiator in the prior art methodology.
The invention will now be described in relation to the accompanying drawings, in which:
Figure 8 illustrates a schematic block diagram of the system of this invention.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Different radiator fan configurations can be deployed enumerating various permutations and combinations in order to obtain cooling. For optimised calculation and prediction of cooling, in relation to a radiator fan assembly, systems are used, which systems use empirical formulae to test the output of the radiator fan assembly that is selected. Measurements of different configurations are very difficult and expensive. Hence, CFD analysis is used for prediction of air velocity. These empirical formulas have limited accuracy outside the range they have been derived. These inaccuracies lead to the use of higher safety factors in design. These high safety factors lead in overcompensation and thus result in high cost of redundant equipment and increased weight, too.
E.g. it was observed that by way of designing system of the prior art, the calculated top oil temperature was a lot different that the measured value of the top oil, using the same designed parameters and values.
There can be a plurality of permutations and combinations of radiators with multiple fans based on transformer rating.

Figure 1 illustrates a schematic of a radiator fan (12) on a stand (14) simulating a radiator-single-fan assembly for CFD analysis.
Figure 2 illustrates a CFD analysis of the radiator-single-fan assembly of Figure 1.
Prior art systems and methodologies were based on the assumption that velocity of air across the height (H) of the radiator assembly is constant. This constant resulted in larger than required safety margins, thereby requiring additional component cost and a non-optimised radiator-fan design. From the CFD analysis of Figure 2, it can be seen that velocity of air depreciates as it gains height.
Figure 3 illustrates a transformer with side plates (16) and fans (12).
Figure 4 illustrates a CFD analysis for the transformer - fan assembly of Figure 3, thereby showing velocity contours along different heights of the radiator. Reference numeral 18 shows that air escapes from front and rear side.
Figure 5a illustrates a CFD analysis depicting velocity contour at pre-defined
heights for a one radiator - two fan assembly.
Figure 5 b illustrates a CFD analysis depicting velocity contour at pre-defined
heights for a three radiator - six fan assembly.
Figure 5c illustrates a CFD analysis depicting velocity contour at pre-defined
heights for a five radiator - ten fan assembly.
It can be seen from each of these analyses that the velocity of air drops as it gains
height. The distributed velocity can be seen in the horizontal plates which form the
locus of pre-defined height where measurement of velocity occurs.

Figure 6 illustrates Nusselt number variation along the height of a radiator.
Due to large variation in the velocity along the height of radiator, there is also
deviation in the Nusselt number. Hence Nusselt number correlation needs to be
modified.
Figure 7 illustrates the differential velocity of air through a radiator in the prior art methodology. The DesPT value was the constant value taken across all radiator-fan assemblies in computing designs. However, as seen from the figure, there is a large differential drop in velocity as the height increases. This differential was unaccounted for in the prior art designing systems and methodologies.
According to this invention, there is provided a system and a method for designing radiator cooling equipment.
Figure 8 illustrates a schematic block diagram of the system of this invention.
In accordance with an embodiment of this invention, there is provided a first input means (IM1) adapted to provide radiator height (H) input.
In accordance with another embodiment of this invention, there is provided a second input means (IM2) adapted to provide number of segments into which the radiator height is to be divided.
In accordance with yet another embodiment of this invention, there is provided a dividing means (DVM) adapted to divide a given radiator height (H) into a plurality of equidistant smaller segments, thereby defining segment height (h).

In accordance with still another embodiment of this invention, there is provided a third input means (IM3) adapted to input fan speed (N) in relation to the radiator.
In accordance with an additional embodiment of this invention, there is provided a velocity computation (VCM) means adapted to compute velocity (V), at a given segment height, based on the input height (H), input segment height (h), fan speed (N) and pre-defined mathematical model
The formula is given as:

In accordance with yet an additional embodiment of this invention, there is provided a designing means (DGM) adapted to provide a design of radiator - fan assembly based on computed velocity at each of said segment heights depending upon pre-defined empirical parameters. Thus, an optimum design of a radiator assembly can be achieved.
It was observed that with 1°C saving in safety margin, there is approximately 1% saving in transformer cost. It was also observed that standard deviation changed from 5 (prior art) to 2.5 (invention). Results with the system and design of the current invention were found to be in good agreement with the actual measurements.

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. A system for designing radiator equipment, said system comprising:
a. first input means adapted to provide radiator height input;
b. second input means adapted to provide number of segments into which said
radiator height is to be divided;
c. dividing means adapted to divide said first input radiator height into a
plurality of equidistant smaller segments based on said second input, thereby
defining segment height;
d. third input means adapted to input fan speed in relation to said radiator;
e. velocity computation means adapted to compute velocity, at each of said
divided segment heights, based on defined segment height, third input fan
speed and pre-defined mathematical model; and
f designing means adapted to provide a design of said radiator based on said computed velocity at each of said divided segment heights depending upon pre-defined parameters, thereby obtaining an optimum design of said radiator.
2. A system as claimed in claim 1 wherein, said velocity computation means includes a pre-defined mathematical model based on the formula:

3. A method for designing radiator equipment, said method comprising the steps of: i. inputting a first input of radiator height;

ii. inputting a second input of number of segments into which said radiator
height is to be divided; iii. dividing said first input radiator height into a plurality of equidistant smaller
segments based on said second input, thereby defining segment height; iv. inputting a third input of fan speed in relation to said radiator; v. computing velocity, at each of said divided segment heights, based on
defined segment height, third input fan speed and pre-defined mathematical
model; and vi. designing said radiator based on said computed velocity at each of said
divided segment heights depending upon pre-defined parameters, thereby
obtaining an optimum design of said radiator.
4. A method as claimed in claim 1 wherein, said step of computing velocity includes the step of computing velocity based on a pre-defined mathematical model which is based on the formula: