IL22389A

IL22389A - Heat exchanger

Info

Publication number: IL22389A
Application number: IL2238964A
Authority: IL
Original assignee: Commissariat Energie Atomique
Priority date: 1963-11-19
Filing date: 1964-11-03
Publication date: 1968-05-30
Also published as: GB1032990A; NL6413455A; ES306123A1; LU47329A1; CH423846A; FR1384012A; BE655554A

Description

'πιηη |Π3 ΐ"ΐιπΐ" ·π PATENT ATTORNEYS ■ O'QIDS DR. RIINHOLD COHN |Π3 ΤϊΙΠΙ'·Ί m OR. MIC HAIL COHN 1 Π 3 1 H 3 « D "Π ISRAEL SHACHTER B.Sc. .0.2 1D3IU IN-ID)' Fit* C / 21528 PATENTS AND DESIGNS ORDINANCE SPECIFICATION MEAT EXCHANGER Bit! q»¾>M9 I (we) COMMISSARIAT A L'ENERO IE ATOM I QUE, OP 29» RUE OE LA FEDERATION, - PARIS 15° - PR ANOE , do hereby declare the nature of this invention and in what manner the same is to he performed, to be particularly described and ascertained in and by the following statement :- The present invention relates to a heat exchanger, especially of the type consisting of a tubular element provided with internal cooling fins.

It is known that, in heat exchangers wherein a gas yields heat to a liquid which serves as a cooling agenti the coefficient of heat transfer between the gas and the metal of which the separating wall of the exchanger is made is much lower than the coefficient of heat transfer between the metal and the liquid „ It is therefore of interest to increase the area of surface which is in contact with the gas by providing said surface with fins formed of a material which has good heat conductivity.

The fins referred-to can be either internal or external. Internal fins, although more difficult to form, are of greater advantage in the structural design of the heat exchanger, above all if the cooling agent employed in said exchanger is a liquefied gas such as boiling freon.

The heat exchanger in that case is similar in design to a boiler with boiler tubes.

In addition, when the gas to be cooled is either dangerous or costly, the volume which is made available for said gas is reduced to a minimum since the circulation is longitudinal, the only pressure losses being due to friction; furthermore, the cross-sectional area of passage is in this case reduced to a minimum. However, when the fins in a heat exchanger of this type join a central tube to a peripheral ring in uninterrupted manner so as to delimit the heat exchanger proper, said fins define in each transverse section zones having a generally triangular shape wherein that portion of each zone which is located in the vicinity of the central tube is made correspondingly thereby achieved is a thickening of the laminar boundary layer of the gas flow in this region, thus unfavorably reducing the coefficient of heat transfer.

The invention is directed to an internally-finned heat exchanger which overcomes the above-noted dis-advantageaby providing a substantial improvement in the heat transfer coefficient.

To this end, the heat exchanger considered, which is of the type comprising a tubular element for the circulation of gas to be cooled which consists of a peripheral ring and a central tube and a first series of radial fins which join the peripheral ring to the central tube in an uninterrupted manner, is characterized in that each fin of the first series is arranged in alternate sequence with a fin of a second series, the fins of said second series extending radially from the peripheral ring towards the central tube and being interrupted at a distance short of the central tube in such a manner that the adjacent fins of both series delimit spaces having widths which remain substantially constant in the vicinity of the peripheral ring and in the vicinity of the central tube .

By virtue of these arrangements, the efficiency of that surface which is in contact with the gas circulating between the fins is accordingly improved from the point of view of heat transfer as compared with heat exchangers of conventional design.

An additional advantage of a heat exchanger of this type from the point of view of overall dimensions lies in the fact that provision can be made for a central bore which has a relatively smaller diameter, and a higher cross- cross-sectional area of passage provided for the gas to the total cross-sectional area of the tubular element.

A better understanding of the invention will in any case be gained from the following description of one example of construction which is given by way of indication only and not by way of limitation.

In the accompanying drawings : - Fig. 1 shows a transverse cross-section of the gas-circulation tube of a heat exchanger of a conventional type - Fig. 2 shows a transverse cross-section of the gas-circulation tube of a heat exchanger as designed in accordance with the invention.

- Fig, 3 illustrates a possible alternative form of the tube of Fig. 2.

There can be seen from Fig. 1 a tubular element for the circulation of gas and designed for a heat exchanger, comprising a central tube 1 and a peripheral ring 2 which are joined together radially by internal fins 3. Said fins form cooling zones in which the gas is circulated, the cooling liquid being circulated in the zone which is located outside the peripheral ring. In the cooling zones 4-, the distance between the walls formed by the fins decreases to a marked extent from the periphery 2 to the central tube 1, thereby creating a laminar boundary layer in the regions adjacent the central tube.

There has been shown in Fig. 2 a tubular element for the circulation of gas and designed for a heat exchanger, as constructed according to the invention.

Said element comprises a central tube 1, a peripheral zone 2 and two series of internal fins, the fins of the first continuous manner, whilst each fin of the second series such as the fin 4- extends from the peripheral zone 2 and is interrupted at a distance short of the central tube 1.

The zone which is delimited by the adjacent fins thus has a U-shaped transverse cross-section owing to the presence of the fin 4-, It can be seen that, in this arrangement, the distances between the walls vary by a fairly small value from the peripheral zone 2 to the central tube 1 and make it possible either to ensure better thermal efficiency of the surfaces which are in contact with the gas or to reduce the dimensions of the central tube while retaining similar cooling efficiency.

Is will be readily understood, the invention is not limited to the form of embodiment which has been described in the foregoing but is intended on the contrary to include within its scope all alternative forms.

Accordingly, and as illustrated in Fi 0 9 the central tube 1 can advantageously be provided with internal fins such as the fin 6 which are located in the line of extension of the fins 3a and 3b „ The purpose of this arrangement is to reduce the hydraulic diameter of the central tube to an appreciable extent and thus to provide a large measure of improvement from the point of view of heat exchange efficienc .

Claims

1. HAVING MOW ASOSftTAINEO OF SAID INVENTION AND IN THE TO Heat exchanger of the type comprising a tubular element for the circulation of gas to he cooled which consists of a peripheral ring and a central tube and a first series of radial fins which the peripheral ring to the central tube in an uninterrupted characterized in that each fin of the first series is arranged in alternate sequence with a fin of a second the fins of said second series extending radially from the peripheral ring towards the central tube and being interrupted at a distance short of said central tube in such a manner that the adjacent fins of both series delimit spaces having widths which remain substantially constant in the vicinity of the peripheral ring and in the vicinity of the central tube Heat exchanger in accordance with Claim characterized in that the central tube is fitted with internal fins located in the line of extension of the uninterrupted radial fins which join said tube to the peripheral Heat substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings OAT OP THB 0 insufficientOCRQuality