US20120312515A1

US20120312515A1 - Apparatus for heat dissipation of transforming radiators

Info

Publication number: US20120312515A1
Application number: US13/157,407
Authority: US
Inventors: Jeffrey Nemec; Shirish Mehta; Padma Varanasi
Original assignee: Waukesha Electric Systems Inc
Current assignee: Prolec GE Waukesha Inc
Priority date: 2011-06-10
Filing date: 2011-06-10
Publication date: 2012-12-13

Abstract

In accordance with one embodiment of the present invention, a panel for a transformer radiator includes a pair of substantially-rectangular panel sheets joined together to form a plurality of internal fluid channels, each fluid channel including an inlet and an outlet, and a plurality of pin fins disposed on at least a portion of at least one external surface of the panel sheets.

Description

FIELD OF THE INVENTION

The present invention relates generally to transformers. In particular the present invention relates to heat dissipation for transformers.

BACKGROUND OF THE INVENTION

The power generation industry relies heavily on large transformers. Typically, these large transformers create enormous amounts of heat and require efficient cooling thereof to prevent failure. Generally, a coolant such as oil, is provided in the transformer tank to absorb the heat. The oil is circulated through numerous heat exchangers also known as panels, that are in fluid communication with the transformer tank to cool the transformer. In the past, to provide better heat transfer, the number and size of the heat panels had been increased. However this is not cost effective because of the cost of the oil and the raw materials required to manufacture the panels.
Another manner of cooling the transformers includes ambient air flowing across the panels known as natural convection. However, this type of cooling can be problematic because of seasonal and geographic variations in ambient conditions. To somewhat overcome this challenge, large industrial fans are utilized to force the air to move more quickly across the panels to dissipate the heat faster, known as forced air convection. However, these fans are extremely loud, causing a great majority of the noise associated with substations, require a great deal of energy to operate, and require a great deal of maintenance.
Thus, it is desirable to provide a more efficient manner of cooling transformers. It is also desirable to reduce the size of the transformer panels to reduce the cost of raw materials and as well as the cost of the oil coolant. Lastly, it is also desirable to reduce or eliminate the noise associated with the large fans while lowering manufacturing and maintenance costs.

SUMMARY OF THE INVENTION

The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments reduces the number and size of the panels, reduces noise and effectively cools the transformers.
In accordance with one embodiment of the present invention, a panel for a transformer radiator includes a pair of substantially-rectangular panel sheets joined together to form a plurality of internal fluid channels, each fluid channel including an inlet and an outlet, and a plurality of pin fins disposed on at least a portion of at least one external surface of the panel sheets.
In accordance with another embodiment of the present invention, a transformer radiator, includes a distributor header fluidly-coupled to a transformer, a collector header fluidly-coupled to the transformer, a plurality of panels, each panel having a pair of substantially-rectangular panel sheets joined together to form a plurality of internal fluid channels, each fluid channel including an inlet fluidly-coupled to the distributor header and an outlet fluidly-coupled to the collector header, and a plurality of pin fins disposed on at least a portion of at least one external surface of the panel sheets.
In accordance with yet another embodiment of the present invention, a transformer radiator includes a distributor header fluidly-coupled to a transformer, a collector header fluidly-coupled to the transformer, a plurality of panels, each panel having a pair of substantially-rectangular panel sheets joined together to form a plurality of internal fluid channels, each fluid channel including an inlet fluidly-coupled to the distributor header and an outlet fluidly-coupled to the collector header, and means for radiating heat from at least a portion of at least one external surface of the panel sheets.
There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a transformer tank.

FIG. 2 is a side view of the transformer tank of FIG. 1.

FIG. 3 is a perspective view of a heat exchanger panel.

FIG. 4 is a cross sectional view of the heat exchanger panel of FIG. 3.

FIGS. 5, 6, and 7 are perspective views of portions of heat exchanger panels according to embodiments of the present invention.

FIGS. 8 and 9 are perspective views of fine pin fins, according to embodiments of the present invention.

DETAILED DESCRIPTION

The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. The foregoing needs are met, to a great extent, by the present invention that in some embodiments, reduces the number and size of the panels, reduces noise and effectively cools the transformers. An apparatus and method are provided that increase the natural air convection cooling of a transformer. Further, in an embodiment of the present invention, the size of the transformer panels is reduced, lowering costs of the raw materials.
The effectiveness of heat transfer for this particular application depends on the resistance within the oil, resistance within the metal forming the panels and the resistance of the air flowing over the panels. Because oil and air are in convective motion, their respective resistances are dependent on their respective heat transfer coefficients. The resistance of the metal panels depends on the thickness of the metal wall and the thermal conductivity of the metal. Thus, the total resistance of the panel with the oil flowing inside and the air flowing outside is the sum of the resistances of the oil, the air and the metal.
By reducing the resistance of any or all of these components, the average temperature of the transformer can be reduced, increasing the efficiency of the transformer itself. Because the majority of the total thermal resistance lies within the air phase, lowering the resistance of the air leads to more efficient heat transfer.
FIGS. 1 and 2 illustrate a transformer tank 10 as seen at a sub-station. The transformer tank 10 includes a tank body 12 that encloses the transformer (not shown). External to the tank body 12 are banks of panels 16. The panels 18 are coupled at their tops and bottoms to facilitate fluid communication between the inside of the tank body 12 and the panels 18 through the use of distributor headers 20 and collector headers 22.
The distributor header 20 is located above each set of panels 18 and the collector header 22 is located below each set of panels 18. Oil within the tank body 12 absorbs heat generated from various parts of the transformers such as core and coils, and rises to the top. Once the hot oil rises, it enters a distributor header conduit 24 connected to the distributor header 20. The oil then flows down through the panels 18 and is cooled. The buoyancy driving force developed due to heat dissipation, from radiator panel surfaces, causes the cooler oil to flow down toward the collector header 22 and is returned into the tank body 12 through a collector header conduit 26. The cool oil begins to absorb heat from the transformer, rises and the cycle continues.
Due to the immense heat generated by the transformer, the panels 18 are very large and numerous in order to provide as much surface area as possible for natural and forced convection to remove the heat from the oil. The distributor header 20 and collector header 22 are connected fluidly to each of the panels 18. The panels 18 are spaced a certain distance apart to permit airflow between the panels 18.
FIGS. 3 and 4 are perspective views of a panel 18 and a cross sectional view of a panel 18, respectively. Generally, the panels 18 are substantially rectangular in nature. The panels 18 include a first panel sheet 28 and a second panel sheet 30 joined, as by welding and the like, at their respective perimeters 32. The panels 18 can have openings (not shown) and the like disposed therein for fluid communication with the distributor and collector headers, 20, 22, respectively. When joined together at their perimeters 32, the first and second panel sheets 28, form an interior region 34 for the oil flow. The first and second panel sheets 28, 30 can be “crimped” or have contours or indentations 36 formed thereon to define internal fluid channels for the oil. Here, the indentations constitute the sheets 28, 30 being brought toward each other at various locations, along a length of the panel 18. The panel contours are arcuate or semi-circular in shape. The sheets 28, 30 come together at certain contact points 38. These contact points 38 provide strength and integrity for the panels 18. Adjacent the interior region 34, the indentations 36 do not contact, providing a space between the sheets 28, 30 for the oil to flow through. In this manner of providing indentations, general internal fluid channels are formed for the oil to flow through. Although a general description of panels is provided herein, any conceivable form of channels, indentations, contours and the like can be formed with the panels and is within the scope of this invention. It is also possible to have no indentations, such that the panels 18 are generally rectangular and have a smooth, planar surface.
FIGS. 5, 6, 7 are perspective views of a panel 18 having a plurality of heat exchanger extensions or fine pin fins 40 disposed on the panel. These fine pin fins 40 are generally solid throughout, cylindrical in nature and are coupled to either or both sides of the panels. The fine pin fins 40 may be coupled using any means known, such as welding and the like. However, there must be a very tight tolerance when coupling the fine pin fins 40 to the first and second panel exteriors 28, 30 such that there is very little, if any, gap. Gaps can reduce the heat transfer ability of the fine pin fins 40, thereby reducing the overall efficiency of the panels. The fine pin fins 40 may also be formed integrally with panels 18. Further, the fine pin fins 40 may be hollow tubes to facilitate the oil to enter the fine pin fins 40.
In an embodiment of the present invention, the fine pin fins 40 may be arranged at certain locations on the panels 18. As illustrated in FIG. 5 the fine pin fins 40 may be disposed along an entire surface of a panel 18. As illustrated in FIG. 6, the fine pin fins 40 may be arranged at only a top location of the panels 18. Placing the fine pin fins 40 in this manner is efficient for several reasons. First, the fine pin fins 40 can be expensive to form and couple to the exteriors of the panels 18. Thus, having the fine pin fins 40 at only a portion of the panels 18 reduces costs associated with raw materials, as well as labor. Next, placing the pin fins 40 at the top of the panel 18 makes effective use of the thermal properties of the oil. Because oil and air rise as they absorb heat, the oil and air adjacent the panels 18 is hottest at the top of the panels 18. Thus, greater heat dissipation is required at the top of the panels 18. Therefore, disposing the pins 18 at the top allows for the greatest heat exchange possible. Further, as illustrated in FIG. 7, the pin fins 40 can be disposed along a side of the panels 18. The pin fins 40 can also be formed in rows of at least 3 pin fins 40. The number, pattern, placement, etc., of the pin fins can vary. The external panel contours can alternate having rows of fine pin fins 40, for example. Thus, placement of the pin fins 40 at various locations is contemplated and within the scope of the present invention.
As shown in FIG. 8, the fine pin fins 40 are in a particular pattern such that the pin fins 40 are spaced at a certain distance from each other. However, as shown in FIG. 9 the pin fins 40 are placed in a random fashion and are spaced at varying distances from each other. It is preferred that the fine pin fins 40 are placed over about 5% of the panel 18 surface area to achieve sufficient heat transfer.
The fine pin fins 40 are arranged perpendicular to the surface of the panel 18 to facilitate the greatest heat transfer as the ends of the fine pin fins 40 have the greatest surface area contact with the panels 18. However, it is also possible to have the fine pin fins 40 arranged at various angles and configurations. It is preferred that the pin fins 40 be formed of a highly conductive material such as copper, steel and the like. Pin fin dimensions can be varied to optimize heat transfer. It is preferred to create as large a surface area as possible. For example, it is preferred that the pin fins 40 are cylindrical, oval, rectangular, square, triangular or have a cross-sectional shape that maximizes the surface area, such as a pentagon or star shape and the like. It is also preferred that the pins have a very small diameter, on the order of about 100 microns to about 1 cm. It is preferred that the length “l” of the pins is approximately up to a few cm long, such as from 1 cm to about 10 cm. It is also preferred to place each pin a certain distance from another pin, so as to facilitate air flow between the pins. Thus, it is preferred that each pin be placed from another pin for a distance of approximately 1 to 10 times the diameter θ of the fine pin fins. Thus, if the diameters is θ, the distance “d” is in the range of 10 to 100. This range can be utilized in the stream-wise direction (top or bottom) as well as in the span-wise direction (side to side). Further it is preferred to place the pin fins 40 of opposing panels 18 a particular distance from each other so as not to restrict air flow between the panels 18. Distances are measured from center to center of the pin's cross section.
In an embodiment of the present invention, formation and placement of the pins results in numerous advantages. One advantage is that the panel's dimensions can be reduced leading to lower costs in raw materials and in the amount of oil required to flow through the tank. The number of panels can also be reduced, further reducing cost. Additionally, the average temperature of the oil is reduced, allowing for the transformer to perform for a longer period of time without degradation of the oil and solid insulation inside the transformer. Further, as the drop in temperature as a function of distance along the panel surface from top to bottom is steeper in the case of a panel with pin fins, compared to a panel without the pin fins, overall buoyancy driven driving force responsible for oil flow is enhanced, which leads to faster oil flow and consequently lower oil phase heat transfer resistance. Thus, the pin fins also contribute to lowering the thermal resistance of the oil as well as the air. Yet another advantage is that the need for fans is reduced or eliminated, leading to significant noise reduction. The decreased need for fans also leads to further cost reduction because the need to manufacture, operate and maintain the fans is reduced.
The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Claims

1. A panel for a transformer radiator, comprising:

a pair of substantially-rectangular panel sheets joined together to form a plurality of internal fluid channels, each fluid channel including an inlet and an outlet; and

a plurality of pin fins disposed on at least a portion of at least one external surface of the panel sheets.

2. The radiator panel of claim 1, wherein each fluid channel is defined by a predetermined number of panel sheet contours.

3. The radiator panel of claim 2, wherein the panel sheet contours are semi-circular in shape and the pin fins are cylindrical in shape.

4. The radiator panel of claim 2, wherein the pin fins are disposed along at least a portion of each panel sheet contour.

5. The radiator panel of claim 2, wherein the pin fins are disposed along an upper portion of each panel sheet contour.

6. The radiator panel of claim 2, wherein the pin fins are disposed along the panel sheet contours that define the fluid channel proximate to an edge of the panel sheets.

7. The radiator panel of claim 2, wherein the pin fins are disposed along the entire length of each panel sheet contour.

8. The radiator panel of claim 2, wherein the pin fins are disposed along the entire length of alternating panel sheet contours.

9. The radiator panel of claim 2, wherein the pin fins are disposed in rows along the entire length of each panel sheet contour, each row including at least three pin fins.

10. A transformer radiator, comprising:

a distributor header fluidly-coupled to a transformer;

a collector header fluidly-coupled to the transformer;

a plurality of panels, each panel including:

a pair of substantially-rectangular panel sheets joined together to form a plurality of internal fluid channels, each fluid channel including an inlet fluidly-coupled to the distributor header and an outlet fluidly-coupled to the collector header; and

11. The radiator of claim 10, wherein each fluid channel is defined by a predetermined number of panel sheet contours.

12. The radiator of claim 11, wherein the panel sheet contours are semi-circular in shape and the pin fins are cylindrical in shape.

13. The radiator of claim 11, wherein the pin fins are disposed along at least a portion of each panel sheet contour.

14. The radiator of claim 11, wherein the pin fins are disposed along an upper portion of each panel sheet contour.

15. The radiator of claim 11, wherein the pin fins are disposed along the panel sheet contours that define the fluid channel proximate to an edge of each panel.

16. The radiator of claim 11, wherein the pin fins are disposed along the entire length of each panel sheet contour.

17. The radiator of claim 11, wherein the pin fins are disposed along the entire length of alternating panel sheet contours.

18. The radiator of claim 11, wherein the pin fins are disposed in rows along the entire length of each panel sheet contour, each row including at least three pin fins.

19. The radiator of claim 11, wherein the pin fins are disposed on alternating panels.

20. A transformer radiator, comprising:

a distributor header fluidly-coupled to a transformer;

a collector header fluidly-coupled to the transformer;

a plurality of panels, each panel including:

means for radiating heat from at least a portion of at least one external surface of the panel sheets.