Patent Application
20140284037
This disclosure relates generally to tube-and-fin style heat exchangers. More particularly, this disclosure relates to a tube-and-fin style assembly for use in an aluminum grommetted tube (AGT) radiator.
Large heavy duty machines such as track-type tractors, loaders, off highway trucks and excavators require large radiators for engine cooling. One common radiator design is the tube-and-fin structure, where numerous tube-and-fin assemblies are mounted to coolant manifolds and arranged in columns and rows. One example of a tube-and-fin assembly is disclosed in U.S. Pat. No. 6,357,513 by L&M Radiator, Inc. (“Support for Heat Exchanger Tubes”). The '513 patent discloses fins fitted to a flattened tube . Copper grommetted tube (CGT) radiators, in which copper tube-and-fin assemblies are secured to a coolant manifold or other radiator component, are expensive, which has led to the development of aluminum grommetted tube (AGT) radiators.
Aluminum is less expensive than copper, but copper has better heat transfer performance. Aluminum is also lighter than copper but not as strong. To compensate for aluminum's relative weakness and reduced heat transfer capability compared to copper, an aluminum grommetted tube radiator requires different geometry. The present disclosure is directed toward providing an aluminum tube-and-fin assembly that delivers the same heat transfer performance as a copper tube-and-fin assembly but maintains a similar space claim (and thus fits within the same space) and so can be used either as original equipment or to replace copper tube-and-fin assemblies in the field.
In one aspect of the disclosure, an aluminum tube-and-fin assembly is provided having a geometry that delivers the same heat transfer performance as copper tube-and-fin assemblies but maintains a similar space claim. The aluminum fin-and-tube assembly comprises an aluminum tube having a tube body and a plurality of aluminum fins disposed on the body. The Mokire ratio, i.e., the ratio of fin height, expressed in millimeters, to fin density, expressed in fins per inch of the tube, is greater than about 0.3200.
In another aspect of the disclosure an aluminum tube-and-fin assembly for a heat exchanger is provided comprising a generally cylindrical, elongated aluminum tube having a body with flat sides connected by ends and a plurality of aluminum fins extending outward from one or both sides of the tube, each fin terminating in an apex. The assembly has a fin density of about 16 to about 20 FPI and a fin height of about 6.4 to about 6.6 mm.
While a tube-and fin assembly according to this disclosure may be embodied in many forms, there is shown in the drawings and will herein be described in detail one or more embodiments of a tube-and-fin assembly, with the understanding that this disclosure is to be considered an exemplification of the principles of the tube-and-fin assembly and is not intended to limit the tube-and-fin assembly to the illustrated embodiments.
In the description that follows, the following terms are used:
Turning to the drawings, there is shown in
The tube 12 comprises a generally elliptical, cylindrical and elongated body 16 having flattened sides 18 connected by rounded ends 20 and defining an axis A. The tube 12 may further comprise a generally cylindrical top end 22 and a generally cylindrical bottom end 24 for attachment to coolant manifolds. Each fin 14 extends outward from a side 18 of the body 16. A plastic clip 28 enclosing the fins 14 may connect adjacent tube-and-fin assemblies 10 to each other for improved stability.
The fins 14 may be an indivisible, unitary part of a corrugated sheet 30 affixed to either side 18 of the tube 12. The corrugated sheet 30, and thus the fins 14, may be welded, brazed or otherwise affixed to the sides 18 of the tube 12.
As best shown in
The present disclosure describes an aluminum tube-and-fin assembly for an aluminum grommetted tube (AGT) radiator having a geometry that allows the aluminum tube-and-fin assembly to approximate the heat transfer performance of a copper tube-and-fin assembly while maintaining a substantially similar space claim. This has been accomplished by researching and developing an algorithm for determining the fin thickness T, fin density D and fin height H that allows for the aluminum tube-and-fin assembly to have approximately the same heat transfer performance as a copper tube-and-fin assembly while maintaining a substantially similar space claim, despite the decreased heat transfer efficiency of aluminum as compared to copper.
The relationship between fin height (H) and fin density (D) was deemed critical to the success of an aluminum tube-and-fin assembly, so ratio of fin height (H) to fin density (D) (“Mokire ratio”) was developed from the data that accomplished the dual objectives of achieving approximately the same heat transfer performance as a copper tube-and-fin assembly while maintaining a substantially similar space claim.
The following table summarizes the differences between geometry in a copper tube-and-fin assembly and the aluminum tube-and fin assembly of the present disclosure:
For a typical copper tube-and-fin assembly, fin thickness T is about 0.1 mm, fin density D is about 22 FPI and fin height H is about 6.15 mm.
In an aluminum tube-and-fin assembly according to the present disclosure, the fin thickness (and tube thickness) is increased over that used in a typical copper tube-and-fin assembly because aluminum is weaker than copper and to improve heat transfer performance. Further, to maintain proper airflow around the aluminum fins, fin density is reduced. But since reducing fin density can cause a drop in heat transfer performance, fin height is increased to improve performance.
After research and development, a suitable fin thickness T for an aluminum tube-and-fin assembly was determined to be about 0.2 mm. The fin density D for the aluminum tube-and-fin assembly was determined to be less than or equal to about 20 FPI and as low as about 16 FPI. Fin height H for the aluminum tube-and-fin assembly was determined to be between about 6.4 and about 6.6 mm. The Mokire ratio (MR) was determined to be between about 0.3200 (6.4 mm/20 FPI) and about 0.4125 (6.6 mm/16 FPI). The newly configured aluminum tube-and-fin assembly was determined to come close to matching the heat transfer performance of a copper tube-and-fin assembly while maintaining a substantially similar space claim.
For example, in one example a suitable aluminum tube-and-fin assembly was developed having a fin thickness (T) of 0.2 mm, a fin density (D) of 20 FPI and a fin height (H) of 6.55 mm. The Mokire ration (MR) was 0.3275.
The aluminum tube-and-fin assembly described herein is less expensive than traditional copper tube-and-fin assemblies while maintaining similar heat transfer performance and space claim. The aluminum tube-and-fin assembly may be used as a component of large radiators used in heavy duty machines, especially where cost and performance are design factors. The aluminum tube-and-fin assembly 10 may also be used an after-market, drop-in, replacement for existing copper tube-and-fin assemblies.
It is understood that the embodiments of the disclosure described above are only particular examples which serve to illustrate the principles of the disclosure. Modifications and alternative embodiments of the disclosure are contemplated which do not depart from the scope of the disclosure as defined by the foregoing teachings and appended claims. It is intended that the claims cover all such modifications and alternative embodiments that fall within their scope.
