Heat exchange – Tubular structure – With discrete heat transfer means
Patent
1994-09-30
1995-08-15
Flanigan, Allen J.
Heat exchange
Tubular structure
With discrete heat transfer means
165177, 29890043, 2989005, F28F 140
Patent
active
054411068
DESCRIPTION:
BRIEF SUMMARY
This invention relates to heat exchanger tubes and in particular to heat exchanger tubes for heat exchangers such as vehicle radiators, condensers, oil coolers, intercoolers and heaters or the like.
Heat exchange tubes are arranged to carry therein a first fluid medium whilst a second fluid medium is in contact with the exterior of the tube. Where a temperature difference exists between the first and second fluid media heat will be transferred between the two via the heat conductive walls of the tube.
It is known to provide corrugated fins or ribs in the interior of heat exchanger tubes to increase the surface area of conductive material available for heat transfer, and/or cause turbulence of the fluid carried in the interior of the tube. In both cases, heat transfer efficiency is increased. In one known construction a roll formed clad aluminium tube is provided with an insert in the form of a sheet of corrugated fins; insertion of the sheet of corrugated fin into the tube is extremely difficult and typically achievable only manually due to required tight dimensional tolerances between the tube and corrugated fin sheet insert. In another known construction, heat exchange tubes are formed by extrusion from aluminium billets. In this construction internal ribs are formed during extrusion, however extruded tubes are formed from aluminium billet and not clad aluminium, which causes problems when attempting to braze the assembled heat exchanger. Furthermore, extruded heat exchange tubes are expensive to produce.
A further heat exchange tube construction is shown in European patent specification 0302232 in which the corrugated insert is formed integrally with the outer wall of the tube by means of deformation of a sheet or strip of metal. The heat exchange tube disclosed in European patent specification 0302232 is however difficult to produce in practice particularly where automated production is required.
An improved heat exchange tube has now been devised which alleviates some of the above-mentioned difficulties.
According to a first aspect of the invention, there is provided a heat exchange tube comprising an outer wall surrounding a plurality of internal fins extending longitudinally of the tube, the fins and outer wall being formed from a unitary portion of sheet or strip material, the fins comprising respective groups of fins each group comprising a respective shaped portion of the sheet or strip material, the groups of fins extending from a common longitudinal seam line in mutually opposed directions which opposed directions are transverse to the longitudinal direction of the tube.
The common longitudinal seam line comprises a line of abutment of respective portions of the wall of the tube which are inverted during forming to position the groups of fins internally of the tube.
Typically the common longitudinal seam line comprises a bonded join, typically a brazed join.
It is preferred that a pair of groups of fins are provided, advantageously extending transversely from the seam line to substantially the same extent such that in transverse cross-section the tube is preferably substantially symmetrical about the seam line.
Desirably, the shaped portions of the strip or sheet material defining each group of fins are preferably separated from one another by interconnecting portions, which interconnecting portions are not provided with fins.
Advantageously, the groups of fins are provided each adjacent a respective longitudinally running peripheral edge of the sheet or strip material.
The tube is required to be heat conductive, and therefore the strip or sheet material from which the tube is formed is typically of metal or alloy. It is preferred that the strip or sheet material comprises clad aluminium to aid in the brazing of the tube and also the brazing of the final heat exchanger assembly. Portions of the fins are typically brazed to respective portions of the outer wall to improve the thermal conductive connection therebetween.
According to a second aspect, the invention therefore comprises a heat exchan
REFERENCES:
patent: 1777782 (1930-10-01), Bundy
patent: 2151540 (1939-03-01), Varga
patent: 2757628 (1956-08-01), Johnston
patent: 5185925 (1993-02-01), Ryan et al.
Bliss McGlynn
Flanigan Allen J.
Llanelli Radiators Limited
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