GB1586935A

GB1586935A - Heat exchanger with double wall tubes and three tube sheets

Info

Publication number: GB1586935A
Application number: GB20665/78A
Authority: GB
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1977-06-28
Filing date: 1978-05-19
Publication date: 1981-03-25
Also published as: DE2825549A1; FR2396262B1; FR2396262A1; JPS5947838B2; JPS5411556A

Description

(54) HEAT EXCHANGER WITH DOUBLE WALL TUBES AND THREE TUBE SHEETS.

(71) We, WESTlNGHOUSE ELECTRIC CORPORATION of Westinghouse Building, Gateway Center, Pittsburg, Pennsylvania, United States of America, a corporation organised and existing under the laws of the State of Pennsylvania. United States of America, do hereby declare tlle invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following satement: The present invention relates to heat exchangers and more particularly to heat exchangers having double wall tubes.

It is desirable to ensure the separation of heating and heated fluids in heat exchangers and depending on the compatibility of the fluids involved, the effort and expense expended to ensure the separation of these fluids varies. Double wall tubes with grooves in one of the walls at the interface have been proposed as a highly reliable method of maintaining the separation between the fluids. However, two tube sheet junctures are susceptible to leaks. Double tube sheets on each end of the tubes may be utilized to detect leaks at the tube-to-tube sheet juncture further decreasing the possibility of undetected leaks and admixing of the two fluids. Such arrangements are, however, quite expensive.

It is therefore the principal object of the present invention to provide a double wall heat exchanger which reliably performs the same functions as a heat exchanger with double tube sheets, however at greatly reduced costs.

With this object in view, the present invention resides in a heat exchanger comprising a shell a plurality of double wall tubes having an inner wall portion and an outer wall portion. and mounted in tube sheets supported in said shell at the ends of the tubes, characterized in that said double wall tubes are mounted at one end in a single tube sheet and, at the other end, in a pair of tube sheets disposed in a spaced relationship, with the inner wall portion of the tubes terminating adjacent, and being sealed to, one of said pair and the outer wall portion of said tubes terminating adjacent and being sealed to the other of said pair of tube sheets and that the outer wall portions of the tubes are sealed at their inner and outer junction with the single tube sheet, with the outer wall portion having at least one opening extending therethrough within the single tube sheet, and the inner and outer wall portions being sealed at the end of the double wall tube outside said single wall tube sheet.

The invention will become more readily apparent from the following description of a preferred embodiment thereof shown, by way of example only, in the accompanying drawings, in which: Figure 1 is an elevational view, partially in section; of a heat exchanger made in accordance with this invention; Figure 2 is an enlarged partial sectional view showing the tube-to-tube sheet juncture with the single tube sheet; and, Figure 3 is an enlarged partial sectional view showing the tube-to-tube sheet juncture with the pair of tube sheets.

Referring now to the drawings in detail and in particular to Figure 1, there is shown a heat exchanger 1 having an outer shell 3 and a plurality of double wall tubes 5. A single tube sheet 7 is disposed on one end of the shell 3, the lower end as shown in the drawings, and a pair of tube sheets 9 and 11 are disposed on the other end of the shell 3, the upper end as shown in the drawings. The tube sheets 9 and 11 are disposed in a spaced relationship and cooperate with the shell 3 to form an enclosed space 13 therebetween.

Hemispherical heads 15 and 17 are attached to the tube sheets 7 and 11, respectively, and cooperate therewith to form headers for directing the flow of fluid through the tubes 5. The shell 3 is expanded outwardly adjacent each end thereof to provide controlled flow paths for the influent and effluent shell side fluid.

The tubes 5 are double wall tubes with a gap between the two walls or with one or more grooves 6 at the interface of the two walls.

One end of each tube terminates adjacent the single tube sheet 7 as shown in detail in Figure 2. The end of the double wall tube 5 is sealed by a circumferential weld 19 at the interface of the inner and outer wall 21 and 23, respectively. The tube sheet 7 has a plurality of holes 25 for receiving the tubes 5 (only one is shown). Each hole has a boss 27 disposed at each end thereof to facilitate forming a seal weld 28 between the outer wall 23 and the boss 27 on both sides of the tube sheet 7. The portion of the outer wall 23 between the welds 28 disposed within the holes 25 in the tube sheet 7 has one or more openings 29 which provide communication with the grooves 6 to allow any fluid leaking past either of the seal welds 28 to enter the groove 6 so that it may be detected.

As shown in Figure 3, the tube sheets 9 and 11 are spaced apart and the inner tube sheet 9 has holes 31 for receiving the double wall tubes 5. A boss 27 surrounds each hole to facilitate forming a seal weld 28 between the boss 27 and the outer wall 23 of the tube passing therethrough. The outer wall 23 terminates adjacent the inner tube sheet 9 and the inner wall 21 extends through the space 13 between the tube sheets 9 and 11 and through holes 35 in the outer tube sheet 11. Bosses 27 are formed around the holes 35 in the outer tube sheet 11 and to facilitate the forming of a seal weld 28 with the ends of the inner wall 21 as it extends through the tube sheet 11. The grooves 6 at the interface of the inner and outer wall 21 and 23, respectively, are in communication with the space 13 between the tube sheets 9 and 11.

The space 13 serves as a header for collecting any leakage of either the heating or the heated fluid through either wall 21 or 23 of the tubes or through any of the sealed welds 28 between the tubes and the tube sheet, the occurrence of such leakage giving an indication of a leak before there is contamination of one of the fluids by the other.

The heat exchanger hereinbefore described requires only three tube sheets, yet provides an indication of leakage from any tube-to-tube sheet weld and any wall of the double wall tubes while it assures separation of the heating and heated fluids.

WHAT WE CLAIM IS: 1. A heat exchanger comprising a shell, a plurality of double wall tubes having an inner wall portion and an outer wall portion, and mounted in tube sheets supported in said shell at the ends of the tubes, characterized in that said double wall tubes (5) are mounted at one end in a single tube sheet (7) and, at the other end, in a pair of tube sheets (9,11) disposed in a spaced relationship, with the inner wall portion (21) of the tubes (5) terminating adjacent, and being sealed to, one (11) of said pair and the outer wall portion (23) of said tubes (5) terminating adjacent and being sealed to the other (9) of said pair of tube sheets (9,11) and that the outer wall portions (23) of the tubes (5) are sealed at their inner and outer junction with the single tube sheet (7) with the outer wall portion (23) having at least one opening (29) extending therethrough within the single tube sheet (7), and the inner and outer wall portions being sealed at the end of the double wall tube outside said single wall tube sheet.

2. A heat exchanger as claimed in Claim 1, characterized in that one of the wall portions of the double wall tubes (5) has at least one groove at the interface therebetween and generally extending throughout the length of the tube (5).

3. A heat exchanger as claimed in Claim 1 or 2, characterized in that the seals (28) are formed by welds.

4. A heat exchanger as claimed in Claim 1, characterized in that the single tube sheet (7) has bosses (27) on each side surrounding each tube to facilitate seal welding the tubes to both sides of the tube sheet.

5. A heat exchanger substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. form headers for directing the flow of fluid through the tubes 5. The shell 3 is expanded outwardly adjacent each end thereof to provide controlled flow paths for the influent and effluent shell side fluid. The tubes 5 are double wall tubes with a gap between the two walls or with one or more grooves 6 at the interface of the two walls. One end of each tube terminates adjacent the single tube sheet 7 as shown in detail in Figure 2. The end of the double wall tube 5 is sealed by a circumferential weld 19 at the interface of the inner and outer wall 21 and 23, respectively. The tube sheet 7 has a plurality of holes 25 for receiving the tubes 5 (only one is shown). Each hole has a boss 27 disposed at each end thereof to facilitate forming a seal weld 28 between the outer wall 23 and the boss 27 on both sides of the tube sheet 7. The portion of the outer wall 23 between the welds 28 disposed within the holes 25 in the tube sheet 7 has one or more openings 29 which provide communication with the grooves 6 to allow any fluid leaking past either of the seal welds 28 to enter the groove 6 so that it may be detected. As shown in Figure 3, the tube sheets 9 and 11 are spaced apart and the inner tube sheet 9 has holes 31 for receiving the double wall tubes 5. A boss 27 surrounds each hole to facilitate forming a seal weld 28 between the boss 27 and the outer wall 23 of the tube passing therethrough. The outer wall 23 terminates adjacent the inner tube sheet 9 and the inner wall 21 extends through the space 13 between the tube sheets 9 and 11 and through holes 35 in the outer tube sheet 11. Bosses 27 are formed around the holes 35 in the outer tube sheet 11 and to facilitate the forming of a seal weld 28 with the ends of the inner wall 21 as it extends through the tube sheet 11. The grooves 6 at the interface of the inner and outer wall 21 and 23, respectively, are in communication with the space 13 between the tube sheets 9 and 11. The space 13 serves as a header for collecting any leakage of either the heating or the heated fluid through either wall 21 or 23 of the tubes or through any of the sealed welds 28 between the tubes and the tube sheet, the occurrence of such leakage giving an indication of a leak before there is contamination of one of the fluids by the other. The heat exchanger hereinbefore described requires only three tube sheets, yet provides an indication of leakage from any tube-to-tube sheet weld and any wall of the double wall tubes while it assures separation of the heating and heated fluids. WHAT WE CLAIM IS:

1. A heat exchanger comprising a shell, a plurality of double wall tubes having an inner wall portion and an outer wall portion, and mounted in tube sheets supported in said shell at the ends of the tubes, characterized in that said double wall tubes (5) are mounted at one end in a single tube sheet (7) and, at the other end, in a pair of tube sheets (9,11) disposed in a spaced relationship, with the inner wall portion (21) of the tubes (5) terminating adjacent, and being sealed to, one (11) of said pair and the outer wall portion (23) of said tubes (5) terminating adjacent and being sealed to the other (9) of said pair of tube sheets (9,11) and that the outer wall portions (23) of the tubes (5) are sealed at their inner and outer junction with the single tube sheet (7) with the outer wall portion (23) having at least one opening (29) extending therethrough within the single tube sheet (7), and the inner and outer wall portions being sealed at the end of the double wall tube outside said single wall tube sheet.