GB2039020A

GB2039020A - Tubular structure particularly for heat exchangers

Info

Publication number: GB2039020A
Application number: GB7943623A
Authority: GB
Original assignee: HIROSS INT CO
Current assignee: HIROSS INT CO
Priority date: 1978-12-19
Filing date: 1979-12-18
Publication date: 1980-07-30
Also published as: IT7830889V0; DE2949690A1; SE7910326L; ES247913U; FR2444916A1

Abstract

A tubular structure particularly for heat exchangers comprises a first circular cross-section tube 1 and a second multi-lobe cross-section tube 2 forcibly fitted therewithin. The tube 2 is obtained by rolling along the generatrix lines (7, 8, 9) a tube having originally the same cylindrical cross- sectional shape as the tube 1. <IMAGE>

Description

SPECIFICATION Tubular structure, particularly for heat exchangers of the finned core type This invention relates to a tubular structure, particularly for heat exchangers of the finned core type.

As is known, this type of heat exchangers comprise a plurality of parallel tubes, or pipes, supported by plates at their ends, the tubes being sometimes interconnected at such end plates to form one or more circuits in parallel.

Onto the tube outsides, fines are pressure fitted which also form passages through which ventilation air can be circulated.

It is essential, in such exchangers, to maximise the overall rate of thermal exchange between the fluid which is circulated through the tube nest and the environment, and it is a known fact that the overall rate of thermal exchange will depend on both the thermal exchange between the environmental medium and the tube outside surfaces, and the thermal exchange which takes place between the inside surfaces of the tubes and the fluid being circulated through the tubes themselves.

This invention sets out to provide a tubular structure, intended for circulation of a fluid therethrough, which ensures an improved rate of thermal exchange between the fluid and the tubular structure itself.

Within that general aim, it is possible to arrange that the tubular structure according to the invention has component parts which are easily manufactured and assembled, as well as of relatively low cost.

According to one aspect of the present invention, there is provided a tubular structure, particularly for heat exchangers, characterised in that it comprises a first annular cross-section tube and a second multiple-lobe cross-section tube forcibly fitted inside said first tube, and fully immersed in the fluid being circulated therethrough.

Further features and advantages of the invention will become more apparent from a detailed description of a preferred, though not limitative, embodiment thereof, in conjunction with the accompanying drawing, where: Figure 1 is a partly cut-away isometric view of the instant structure; and Figure 2 is a cross-sectional view, as taken in a plane perpendicular to the axis of the instant tubular structure.

With reference to the cited drawing figures, the inventive structure comprises a first tube 1 of circular cross-section, a fluid being caused to flow through the'tube in a conventional manner. Inside the first tube 1, there is inserted a second tube 2, which is fully immersed in the fluid and has a lobed type of cross-section including three lobes, 4, 5, 6 respectively. This three-lobe cross-sectional configuration is preferably obtained by mechanical deformation, as carried out on a rolling machine along generatrix lines 7, 8, 9 of a tube which was originally absolutely identical to the first tube 1.

Said second tube 2 can be nested inside the tube 1 to a pressure fit, because its three-lobe cross-section can be enveloped by a cylindrical surface set to interfere slightly with the inside surface of the first tube 1.

Thus, three areas of contact between the two tubes are created, respectively at 10, 1 1, 12 which form thermal bridges allowing the heat, the second tube 2 picks up from the fluid circulated through it, to be transferred to the first, or outside, tube 1.

When it is considered that the rate of thermal exchange between a fluid flowing through a duct and the duct itself is a linear function of the lapped surface area, it will become apparent that the exchange surface area has now been almost trebled with respect to the surface area to be obtained with an ordinary cylindrical tube. In fact, to the inside surface area of the first tube 1 ,the inside and outside surface areas, which are both lapped by the fluid, of the second tube 2 should be added.

Even when the load drop occurring on account of the reduced useful flow section for the passage of the fluid through the first tube 1 is considered, a substantial increase of the thermal exchange rate is achieved and, by virtue of the simple construction of the instant structure, the efficiency-to-cost ratio is also improved.

It should be further noted that the second tube 2 is produced by cold processing the same type of tube stock as utilised for the first tube 1, thereby it is unnecessary to make different stocks available.

Obviously, the second tube 2 may be formed with any number of lobes, the lobes of different shapes without departing from the scope of the invention.

1. A tubular structure, particularly for heat exchangers, characterised in that it comprises a first annular cross-section tube and a second multiple-lobe crnss-secti6n tube forcibly fitted inside said first tube and fully immersed in the fluid being circulated therethrough.

2. A tubular structure according to Claim 1, characterised in that said second tube is obtained by a rolling process performed along generatrix lines of a tube having originally the same cylindrical cross-sectional shape as said first tube.

3. A tubular structure according to Claim 1 characterised in that said second tube has a threelobe cross-sectional configuration which is envelopable by a cylindrical surface.

4. A tubular structure according to Claim 1, characterised in that said second tube is nested to a pressure fit inside said first tube such as to create, by deformation of said tubes, contact areas constituting thermal bridges allowing the heat picked up by said second tube from the fluid lapping it to be transferred from said second or internal tube to said first or external tube.

5. A tubular structure substantially as herein

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Tubular structure, particularly for heat exchangers of the finned core type This invention relates to a tubular structure, particularly for heat exchangers of the finned core type. As is known, this type of heat exchangers comprise a plurality of parallel tubes, or pipes, supported by plates at their ends, the tubes being sometimes interconnected at such end plates to form one or more circuits in parallel. Onto the tube outsides, fines are pressure fitted which also form passages through which ventilation air can be circulated. It is essential, in such exchangers, to maximise the overall rate of thermal exchange between the fluid which is circulated through the tube nest and the environment, and it is a known fact that the overall rate of thermal exchange will depend on both the thermal exchange between the environmental medium and the tube outside surfaces, and the thermal exchange which takes place between the inside surfaces of the tubes and the fluid being circulated through the tubes themselves. This invention sets out to provide a tubular structure, intended for circulation of a fluid therethrough, which ensures an improved rate of thermal exchange between the fluid and the tubular structure itself. Within that general aim, it is possible to arrange that the tubular structure according to the invention has component parts which are easily manufactured and assembled, as well as of relatively low cost. According to one aspect of the present invention, there is provided a tubular structure, particularly for heat exchangers, characterised in that it comprises a first annular cross-section tube and a second multiple-lobe cross-section tube forcibly fitted inside said first tube, and fully immersed in the fluid being circulated therethrough. Further features and advantages of the invention will become more apparent from a detailed description of a preferred, though not limitative, embodiment thereof, in conjunction with the accompanying drawing, where: Figure 1 is a partly cut-away isometric view of the instant structure; and Figure 2 is a cross-sectional view, as taken in a plane perpendicular to the axis of the instant tubular structure. With reference to the cited drawing figures, the inventive structure comprises a first tube 1 of circular cross-section, a fluid being caused to flow through the'tube in a conventional manner. Inside the first tube 1, there is inserted a second tube 2, which is fully immersed in the fluid and has a lobed type of cross-section including three lobes, 4, 5, 6 respectively. This three-lobe cross-sectional configuration is preferably obtained by mechanical deformation, as carried out on a rolling machine along generatrix lines 7, 8, 9 of a tube which was originally absolutely identical to the first tube 1. Said second tube 2 can be nested inside the tube 1 to a pressure fit, because its three-lobe cross-section can be enveloped by a cylindrical surface set to interfere slightly with the inside surface of the first tube 1. Thus, three areas of contact between the two tubes are created, respectively at 10, 1 1, 12 which form thermal bridges allowing the heat, the second tube 2 picks up from the fluid circulated through it, to be transferred to the first, or outside, tube 1. When it is considered that the rate of thermal exchange between a fluid flowing through a duct and the duct itself is a linear function of the lapped surface area, it will become apparent that the exchange surface area has now been almost trebled with respect to the surface area to be obtained with an ordinary cylindrical tube. In fact, to the inside surface area of the first tube 1 ,the inside and outside surface areas, which are both lapped by the fluid, of the second tube 2 should be added. Even when the load drop occurring on account of the reduced useful flow section for the passage of the fluid through the first tube 1 is considered, a substantial increase of the thermal exchange rate is achieved and, by virtue of the simple construction of the instant structure, the efficiency-to-cost ratio is also improved. It should be further noted that the second tube 2 is produced by cold processing the same type of tube stock as utilised for the first tube 1, thereby it is unnecessary to make different stocks available. Obviously, the second tube 2 may be formed with any number of lobes, the lobes of different shapes without departing from the scope of the invention. CLAIMS

5. A tubular structure substantially as herein described with reference to the accompanying drawing.

6. Any novel element, or combination of elements, herein described and-or shown in the accompanying drawing, irrespective of whether the present claim is within the scope of, or relates to the same invention as, any of the preceding claims.