Heat exchange – Radiator core type – Side-by-side tubes traversing fin means
Patent
1996-01-05
1997-12-02
Flanigan, Allen J.
Heat exchange
Radiator core type
Side-by-side tubes traversing fin means
165184, 165DIG525, F28F 132, F28F 140
Patent
active
056925603
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is concerned with tubes which are used for manufacturing heat exchangers in air conditioning equipment and refrigerating equipment, or for any other heating or cooling application, the tubes helping exchange heat between a fluid circulating in the tubes and the atmosphere circulating in said exchangers.
The invention is also concerned with said exchangers which usually comprise an assembly of copper, aluminium or steel tubes, usually in the form of pins (straight portions+bends), and plates known as vanes, made of copper or aluminium, in thermal contact with said tubes, usually being perpendicular to said straight portions of the tubes and offering a large surface area for exchange with said atmosphere.
A very large number of variants of tubes, usually copper and copper alloy tubes, are already known, and means for improving heat exchange between the fluid circulating in the tube and the external atmosphere.
To illustrate these variants, it is possible to cite U.S. Pat. No. 4 480 684 and European Patent Application EP-A-148 609 which describe internally grooved tubes.
In U.S. Pat. No. 4 480 684, the grooves are characterised by a combination of the following features: 16.degree. and 35.degree., 100.degree..
FIGS. 2 and 6 of that patent illustrate respectively an exchanger and a profile portion of the tube along a section which is perpendicular to the tube axis, showing "V"-shaped grooves separated by "V"-shaped ribs of the same angle, termed the apex angle (alpha).
European Application EP-A-148 609 also describes grooved tubes whose helical grooves are trapezoidal in section and whose ribs are triangular in section, which tubes are characterised by a combination of the following features: the internal diameter Di of the tube is between 0.02 and 0.03, depth H is between 0.15 and 0.40 mm,
The skilled person has long been aware of the importance of grooved tubes in increasing heat exchange between a fluid circulating inside the tube and the tube itself.
The skilled person knows that in the case of a typical copper tube of external diameter 9.52 mm it is preferable to have a sufficient number (45 to 65) of helical ribs/grooves (with a helix angle of between 10.degree. and 30.degree.).
However, despite the fact that these features would seem to result from the skilled person analysing the prior art, with respect to many other features relating to the actual form of the ribs and grooves, the prior art does not give a unified picture, a homogeneous teaching, to which the skilled person could turn in order to be certain of obtaining a high performance exchanger tube.
Moreover, when working on realising compact batteries where there is improved thermal contact between tubes and vanes, the Applicant used per se known features to bend prior art grooved tubes and to crimp them with vanes, typically using a mandrel which went around inside the tube so as to cause the tube to expand slightly against the edge of the ends of the vanes, and to thus obtain excellent thermal contact, without the call for costly soldering or brazing techniques.
On examining sections of crimped tubes (standard tube with 60 "V"-shaped ribs), the Applicant noted that ribs became crushed which meant that there was a significant reduction in the depth H of the section S of the groove
______________________________________ before crimping after crimping
______________________________________
H 0.20 mm 0.13 mm
S 0.060 mm.sup.2 0.024
mm.sup.2 (-60%)
______________________________________
As far as the heat exchange was concerned between the fluid circulating in the tube and the tube itself, the measurements taken as comparisons on tube portions before and after crimping confirmed that performance deteriorated after crimping due to a 60% reduction in the section S.
Thus, the Applicant came to the conclusion that it would only be useful to deal with and optimise the performance of a tube if consideration was also taken of the deformation of the ribs/grooves which could happen during assembly of t
REFERENCES:
patent: 4658892 (1987-04-01), Shinohara et al.
patent: 4660630 (1987-04-01), Cunningham et al.
patent: 5010643 (1991-04-01), Zohler
Messant Michel
Pinet Veronique
Predki Rene
Flanigan Allen J.
Trefimetaux
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