Patent Application
20090277611
This invention is directed towards heat exchangers and, more specifically, radiator assemblies for use with fluid sealed electrical apparatuses.
Radiator assemblies for oil-filled electrical apparatuses have been widely used and are available in a number of different shapes and cooling configurations. Radiator assemblies are frequently needed for electrical equipment which use oil to transfer heat from electrical equipment. The oil is directed to an oil-filled radiator which is cooled by the passage of ambient air over the radiator surface.
In one type of oil-filled radiators, such as those marketed by the assignee of this patent application under the Flexoplate® trademark, radiators provide a recirculation loop to cool oil which is in contact with the electrical equipment. As the oil is heated by the electrical equipment, it expands due to the increase in temperature. The volume of oil likewise increases along with a reduction in the oil density. The hot, low-density oil will rise to the top of the electrical equipment and flows through a connecting passage into an upper region of a radiator. The hot oil transfers heat to the radiator which is subsequently transferred into the surrounding ambient air. As the oil cools, the oil flows by gravity to the bottom of the radiator undergoing additional cooling as the oil passes through the radiator. The oil is then directed back into the electrical apparatus.
One deficiency within the prior art is a failure on the part of both the purchasers and some manufacturers of radiator cooling products to fully integrate the specific cooling needs with the end radiator product. At one extreme, purchasers of radiator products may expend resources acquiring a radiator that has excessive cooling capacity and in so doing expend more money than is required to bring about efficient cooling. At the other extreme, a radiator product may be acquired which under performs with respect to the electrical transformer. In such cases, auxiliary fans or oil pumps are utilized to increase air flow or oil flow across or through the radiator at considerable expense that could have been avoided by proper matching of the radiator to the cooling needs. There is a further need in the industry to maximize the heat dissipation capability of a transformer radiator such that the most economical radiator can be provided to achieve the desired cooling.
Accordingly, there remains room for variation and improvement within the art.
It is one aspect of at least one of the present embodiments to provide for an air-cooled radiator for oil-filled electrical equipment in which the oil inlet and the oil outlet for the oil flow have an increased diameter.
It is a further aspect of at least one embodiment of the present invention to provide for a heat exchange plate of the radiator having an increased hydraulic diameter with respect to the same perimeter profile, thereby reducing the friction factor for the oil flow.
It is further aspect of at least one of the present embodiments to provide for a radiator assembly providing a larger neck region of the radiator associated with the inlet header and a similar enlargement of the neck on the exit header of the radiator, thereby reducing the resistance of flow to the circulating oil.
It is yet another aspect of at least one embodiment of the present invention to provide for an optimized plate spacing within the radiator assembly, the optimized plate spacing providing for an increased hydraulic diameter of the plate for a given perimeter while reducing the friction factor for the external flow of air.
It is yet another aspect of at least one of the present embodiments of the present invention to provide for a ripple pattern for a radiator assembly, the ripple pattern providing a greater hydraulic diameter with respect to oil flow and increasing the ability of the exterior of the ripple pattern to dissipate heat to surrounding ambient air.
It is yet a further aspect of at least one of the present embodiments of the present invention to provide for a radiator assembly for cooling heated oil in which for a given size radiator, provides for greater heat dissipation while using less material than radiators of the similar type found in the prior art.
These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims.
A fully enabling disclosure of the present invention, including the best mode thereof to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying drawings.
Reference will now be made in detail to the embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the present invention are disclosed in the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary constructions.
In describing the various figures herein, the same reference numbers are used throughout to describe the same material, apparatus, or process pathway. To avoid redundancy, detailed descriptions of much of the apparatus once described in relation to a figure is not repeated in the descriptions of subsequent figures, although such apparatus or process is labeled with the same reference numbers.
It is to be understood that the ranges mentioned herein include all ranges located within the prescribed range. As such, all ranges mentioned herein include all sub-ranges included in the mentioned ranges. For instance, a range from 100-200 also includes ranges from 110-150, 170-190, and 153-162. Further, all limits mentioned herein include all other limits included in the mentioned limits. For instance, a limit of up to 7 also includes a limit of up to 5, up to 3, and up to 4.5.
A variety of radiators are known to be used for the cooling of transformer oil. Such radiators include the radiator assembly seen in U.S. Pat. No. 4,019,572 assigned to Westinghouse Electric Corporation and U.S. Pat. No. 3,153,447 assigned to Tranter Manufacturing, Inc., and which are incorporated herein by reference.
The equation which governs heat dissipated from a transformer radiator may be expressed as:
Q=U*A*ΔT
where Q is the heat dissipated; U is the heat transfer co-efficient; A is the heat transfer surface area; and ΔT is the effective temperature difference between the oil and the air.
Heretofore, manufacturers have often stressed the heat transfer area value (A) while ignoring other portions of the equation that may also contribute to the most efficient radiator design for a desired purpose. For instance, ignoring that there may be wide variations in ΔT depending upon placement of the radiators, climate factors, as well as subtle influences on radiator design that may affect the heat transfer co-efficient value (U).
Based upon the above formula and factors, the present design may be directed to improvements to a natural convection radiator which can bring about an improvement (increase) of the heat transfer co-efficient for the entire radiator performance. These improvements, combined with a more thorough understanding of the deployment conditions for the radiator, allow for the most efficient pairing of an efficient radiator product to the desired cooling needs of an electrical transformer.
As set forth in
As is known and appreciated in the art, variations in the length 112 or height of a radiator are usually constrained by the design of the associated electrical equipment, such as a transformer, and as such, radiator dimensions are often set within a very narrow range. As is commonly employed, radiator designs typically will use the largest length 112 available given the limitations of the electrical equipment design. As set forth below, given a specific size or footprint limitation for a radiator, it has been found that significant improvements in the amount of heat that can be dissipated can be achieved by altering features of the radiation design. As noted, oftentimes the design modification allows for increased efficiency of the radiator in a same sized space while using less material which contributes to manufacturing efficiency.
As best seen in reference to
The diameters 16 and 18 need not be identical in other exemplary embodiments but may be different from one another. Further, the diameters 16 and 18 need not be only five inches but can be variously sized in other arrangements. For example, the diameters 16 and 18 may each be from 3.5 to 5 inches, from 4 to 6 inches, or from 4.5 to 5.5 inches in accordance with various exemplary embodiments.
Oil may flow from the inlet header 12 into an inlet neck 22 of the plate 20. Oil then flows into a series of ducts defined in the plate 20.
The second panel 28 defines a first duct third ridge 60 that is convex in shape and is located opposite from the first duct first ridge 56 with respect to the lateral centerline 30 of the plate 20. The first duct third ridge 60 may have a radius of 0.1378 inches. However, in another exemplary embodiment the first duct third ridge 60 has a radius that is 0.1377 inches. The second panel 28 additionally defines a first duct third ridge 62 that is located opposite from the first duct second ridge 58 and is convex in shape. The first duct third ridge 62 may have a radius of 0.1377 inches in accordance with one embodiment. A first duct second furrow 66 is disposed between the ridges 60 and 62 and is concave in shape with a radius of 0.0937 inches. The first duct second furrow 66 is located opposite from the first duct first furrow 64 with respect to the lateral centerline 30. The first duct 64 may have a first duct width 68 of 2.25 inches.
The sixth duct 42 can be arranged in a manner identical to the first duct 32. Here, the sixth duct 42 is symmetrical with respect to the first duct 32 about the longitudinal centerline 102. In this regard, the ridge of the sixth duct 42 formed by the first panel 26 that is farthest from the inlet header 12 along the lateral centerline 30 may be arranged in a manner identical to the first duct first ridge 56. Also, the ridge of the sixth duct 42 formed by the first panel 26 closest to the inlet header 12 along the direction of the lateral centerline 30 can be arranged in a manner similar to the first duct second ridge 58 as previously discussed. The furrow formed by the first panel 26 may be made in an identical manner to the first duct first furrow 64 as previously discussed. Additionally, the features of the sixth duct 42 formed by the second panel 28 may be identical and symmetrical to the features of the first duct 32 formed by the second panel 28.
The plate 20 also features a second duct 34 defined by the first panel 26 and the second panel 28. The first panel 26 defines a second duct first ridge 70 that is convex with a radius of 0.2003 inches. A second duct second ridge 72 is also defined by the first panel 26 and may be convex with a radius of 0.1378 inches. A second duct first furrow 86 is defined between the ridges 70 and 72 and is concave in shape and may have a radius of 0.0938 inches. Third and fourth second duct ridges 74 and 76 are likewise defined by the first panel 26 and are convex in shape. The ridge 74 may have a radius of 0.1377 inches in one embodiment, and ridge 76 may have a radius of 0.2002 inches in one embodiment. The first panel 28 defines a second duct second furrow 88 located between the ridges 72 and 74, and the first panel 28 defines a second duct third furrow 90 that is located between the ridges 74 and 76. The furrows 88 and 90 may be concave in shape and can each have a radius of 0.0938 inches in accordance with one embodiment.
The second panel 28 defines additional portions of the second duct 34 such as a second duct fifth ridge 78 that is convex in shape and is located opposite from ridge 70 with respect to the lateral centerline 30. Ridge 78 may have a radius of 0.2003 inches in certain embodiments. A second duct sixth ridge 80 is present and is convex in shape and located opposite to the ridge 72 with respect to the lateral centerline 30. Ridge 80 may have a radius of 0.1378 inches in accordance with certain embodiments. A second duct fourth furrow 92 is located between the ridges 78 and 80 and is located opposite from the furrow 86 with respect to the lateral centerline 30. The furrow 92 may have a radius of 0.0938 and can be concave in shape in accordance with certain exemplary embodiments. A second duct seventh ridge 82 and a second duct eighth ridge 84 may likewise be defined on the second panel 28 and can be located opposite from the ridge 74 and ridge 76 respectively. The ridges 82 and 84 may have a radius of 0.1377 inches and a radius of 0.2002 inches respectively and may both be convex in shape. A second duct fifth furrow 94 and a second duct sixth furrow 96 can be included and may be concave in shape with a radius of 0.0938 inches. The second duct fifth furrow 94 is located opposite from the furrow 88 with respect to the lateral centerline 30, and furrow 96 is located opposite from the furrow 90 with respect to the lateral centerline 30.
The second duct 34 may have a width 98 of 3.19 inches in accordance with certain exemplary embodiments. The second duct 34 thus features eight ridges 70, 72, 74, 76, 78, 80, 82, and 84 that are convex in shape and six furrows 86, 88, 90, 92, 94, and 96 that are concave in shape. The ridges 70, 72, 74, 76, 78, 80, 82, and 84 may be symmetrical about the lateral centerline 30 in certain embodiments. Further, the furrows 86, 88, 90, 92, 94, and 96 may be symmetrical to the opposite furrow 86, 88, 90, 92, 94, or 96 about the lateral centerline 30 in various embodiments.
The fifth duct 40 is provided with four convex ridges on the first panel 26 and four convex ridges oppositely disposed on the second panel 28. Concave furrows are also present on the first panel 26 that are located opposite from concave furrows on the second panel 28. The fifth duct 40 may be identically arranged with respect to the second duct 34 and symmetrical thereto with respect to the longitudinal centerline 102. However, it is to be understood that other embodiments may exist in which the second and fifth ducts 34 and 40 are not symmetrical about longitudinal centerline 102.
The third and fourth ducts 36 and 38 are located the closest to the longitudinal centerline 102 in the distance along the lateral centerline 30 than any of the other ducts. The third and fourth ducts 36 and 38 may each have eight ridges and six furrows that are located opposite to one another about the lateral centerline 30 as discussed above concerning the second duct 34. The third and fourth ducts 36 and 38 may be symmetrical with respect to one another about the longitudinal centerline 102. The ridges and furrows of the third and fourth ducts 36 and 38 may have radii that are different from or the same as the radii of the ridges and furrows of the second duct 34 and/or the fifth duct 40. In one embodiment, the third duct 36 may be constructed in a manner identically to that of the second duct 34, and the fourth duct 38 may be constructed in a manner identical to the fifth duct 40. In this regard, the second duct 34 and third duct 36 may be symmetrical to the fourth and fifth ducts 38 and 40 about the longitudinal centerline 102. Further, in another exemplary embodiment the first duct 56 and the sixth duct 42 may be symmetrical about the longitudinal centerline 102 so that all of the ducts of the plate 20 are symmetrical to another one of the ducts about the longitudinal centerline 102. However, it is to be understood that the ducts can be variously arranged in other exemplary embodiments so that all or none of the ducts of the plate 20 are symmetrical about the longitudinal centerline 102. Further, it is to be understood that each individual duct 32, 34, 36, 38, 40, and 42 may or may not be symmetrical about the lateral centerline 30 in accordance with various exemplary embodiments.
The height of the apexes of the various ridges to the lateral centerline 30 can be different or the same with respect to all of the ridges of the ducts 32, 34, 36, 38, 40 and 42. In one embodiment, the height 100 of the ridge of the fourth duct 38 farthest from the longitudinal centerline 102 may be 0.23 inches as measured from the apex of the ridge to the lateral centerline 30. Any other one or ones of the ridges of ducts 32, 34, 36, 38, 40 and 42 may have a similar height 100. Further, all of the furrows of the ducts 32, 34, 36, 38, 40 and 42 may have the same near point to the lateral center line 30 or may have varying near points to the lateral center line 30 in accordance with various exemplary embodiments.
The plate 20 includes a first section 44 that is located between the first duct 32 and the second duct 34. The first section 44 features engagement between the first panel 26 and the second panel 28 so that oil will not flow through the first section 44. In addition, a second section 46, third section 48, fourth section 50, and fifth section 52 are provided between the ducts 34, 36, 38, 40, and 42. The various sections 46, 48, 50 and 52 are arranged so that the first panel 26 engages the second panel 28 to prevent oil from flowing therethrough. The third section 54 is located at the longitudinal centerline 102 of the plate 20 and has a width 54 of 0.5 inches in accordance with one exemplary embodiment. The various sections 44, 46, 48, 50 and 52 may all have the same width or may have different widths from one another in accordance with different exemplary embodiments.
Since the plate spacing in the embodiment in
The hydraulic diameter is calculated as Dh=4*A/P where Dh is the hydraulic diameter, A is the area normal to the fluid flow, and P is the perimeter of the flow. The inlet and outlet headers 12 and 14 have a hydraulic diameter (Dh) of 5 inches in the exemplary embodiment of
The increase of the diameters 16 and 18 may allow a larger slot or opening to be present between the headers 12 and 18 and the inlet neck 22 and outlet neck 24. The inlet neck 22 and outlet neck 24 may thus be larger in the embodiment in
Applicant conducted various experiments regarding radiator sections 10 discussed herein. Table 1 below illustrates a test that compared a regular radiator built in a manner similar to the
Another experiment was carried out in accordance with a different exemplary embodiment at the original equipment manufacturer for radiators for transformers. The test was conducted between a regular radiator and an enhanced prototype and results thereof are illustrated below in Table 2. The regular radiator was a radiator bank with one radiator having 18 plates 20 and 4 radiators having 23 plates 20 each, and the enhanced prototype radiator was a radiator bank having 1 radiator with 15 plates 20 and 4 radiators with 18 plates 20 each.
The heat transfer area was reduced about 21% in the enhanced prototype radiator, and the heat transfer coefficient was improved about 22%. The difference between the top radiator oil temperature and the bottom radiator oil temperature showed an increase in oil flow of about 22%.
Additional testing was conducted in order to compare the heat dissipation capacity of 4 radiators with 36 plates 20 each and of 3200 mm in length (regular radiator) to 4 radiators with 29 plates 20 each and of 3200 mm in length (prototype radiator). Table 3 below is data of the test run at the original equipment manufacturer with an OA rating, and the results in Table 4 are from the original equipment manufacturer with an FA rating.
Additional tests were conducted in regards to the radiator design set forth in
Although preferred embodiments of the invention have been described using specific terms, devices, and methods, such description is for illustrative purposes only. The words used are words of description rather than of limitation. It is to be understood that changes and variations may be made by those of ordinary skill in the art without departing from the spirit or the scope of the present invention as described. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Therefore, the spirit and scope of the invention should not be limited to the description of the preferred versions contained therein.
This application claims the benefit of U.S. Application Ser. No. 61/124,989 filed on Apr. 21, 2008 and entitled, “Air-Cooled Radiator Assembly for Oil-Filled Electrical Equipment.” U.S. Application Ser. No. 61/124,989, including all incorporated appendices, is incorporated by reference herein in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 61124989 | Apr 2008 | US |
