Patent Application
20120312515
The present invention relates generally to transformers. In particular the present invention relates to heat dissipation for transformers.
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.
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.
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.
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.
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
As shown in
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.
