True countercurrent heat exchanger with sealing arrangement

Abstract

A heat exchanger has a pass baffle which is formed as an enclosure with two openings, one opening for connection to a shell-side fluid opening and one opening for passing heat exchanger tubes.

Claims

1. A shell and tube heat exchanger comprising: a tube bundle comprising a first end and a second end, said tube bundle being secured at the first end to a tube sheet, an outer shell on a shell side of the tube sheet, surrounding said tube bundle and comprising at least two shell fluid connections: a shell fluid inlet and a shell fluid outlet, the shell fluid inlet and outlet each comprising an opening in the shell, a head member affixed to said shell and disposed on a side of said tube sheet opposite the shell side, the head member having a tube side inlet and a tube side outlet, a longitudinally extending pass baffle disposed within said outer shell and comprising a first end and a second end for dividing shell side fluid into two passes between said shell fluid inlet and shell fluid outlet, wherein said baffle forms an enclosure within the shell having only two openings: a first opening, at a first end of said baffle, sealingly and detachably connected to said shell fluid inlet with a fluid tight, detachable connection disposed in the opening in the outer shell, the first opening of said baffle extending within said shell fluid inlet and being adapted to be sealingly attached to or detached from said shell fluid inlet from the outside of the outer shell, such that, when shell fluid enters the heat exchanger through the shell fluid inlet, all of the shell fluid is forced to pass through the first opening of the baffle and directly into the enclosure of the baffle within the shell, with no shell fluid entering the heat exchanger flowing between the enclosure of the baffle and the shell, and a second opening in the second end of the baffle for passing of the tube bundle.

2. A shell and tube heat exchanger according to claim 1, wherein said first opening is sealingly and detachably connected to the shell fluid inlet.

3. A shell and tube heat exchanger according to claim 1, wherein said first opening is sealingly and detachably connected to the shell fluid outlet.

4. A shell and tube heat exchanger according to claim 1, wherein said baffle is fixed to said tube sheet at its first end.

5. A shell and tube heat exchanger according to claim 4, wherein the baffle is fixed to the tube sheet by means of welding.

6. A shell and tube heat exchanger according to claim 4, wherein the baffle is detachably fixed to the tube sheet.

7. A shell and tube heat exchanger according to claim 1, wherein the baffle is fluid tight fixed to the tube sheet.

8. A shell and tube heat exchanger according to claim 1, wherein said baffle is at least partly insulated to provide thermal insulation between the two passes of the shell side fluid.

9. A shell and tube heat exchanger according to claim 1, wherein said baffle has one flat side and one half circle side, forming a half moon cross sectional shape.

10. A shell and tube heat exchanger according to claim 1, wherein said tube bundle comprises a plurality of U-tubes.

11. A shell and tube heat exchanger according to claim 10, wherein said baffle extends from a first end of the U-tubes at the tube sheet to a location at which the U-tubes begin to bend.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a horizontal cross-section of a heat exchanger according to the state of the art, and

(2) FIG. 2 is a horizontal cross-section of a heat exchanger in accordance with the invention.

(3) It will be understood that the drawings illustrate merely a representative embodiment of the invention and that other embodiments are contemplated within the scope of the claims.

DETAILED DESCRIPTION OF THE INVENTION

(4) The heat exchanger shown in FIG. 1 is a two pass shell and tube unit according to the state of the art in which the tube-side fluid makes two passes through the unit and the shell-side fluid also makes two passes. The exchanger 10 includes an elongated, generally cylindrical outer shell 12 having a shell-side fluid inlet 14 and a shell-side fluid outlet 16. One end of the shell 12 is enclosed by a head 18 while the opposite end is capped with a heat exchanger head generally indicated at 20. The head 20 includes a removable cover 22, an internal stop baffle or pass partition 28, as well as a tube-side inlet 26 and a tube-side outlet 24.

(5) The tube bundle in the exchanger of FIG. 1 comprises a plurality of U shaped tubes 32 attached at their inlet and outlet ends to a tube sheet 30. The tube sheet 30 is securely clamped about its outer periphery between the flanges on the shell 12 and the exchanger head 20. Extending horizontally between the upper and lower passes of each U tube 32 is a horizontal pass baffle indicated at 36. The pass baffle 36 is securely welded at one end to the tube sheet 30. When the head 20 of the exchanger is removed from the tube sheet 30 and the tube sheet 30 and its associated tube bundle is slidably removed from the shell 12, the pass baffle 36 may be withdrawn from the shell 12. Experience shows that there is a potential risk of leak from the inlet side of the shell to the outlet side of the shell, resulting in a part of the shell side fluid will pass the edges of the baffle 36, thus not flowing through the entire length of the shell in a true counter current relative to the tube side fluid.

(6) In an embodiment of the invention according to FIG. 2, the pass baffle 46 is formed as an enclosure with only two openings, one opening 41 adapted to connection with a shell fluid connection, and a second opening 42 in the second end of the pass baffle 46 for passing of the tube bundle 32. There is no sealing between the shell inner side and the pass baffle, and thus no risk of any leak in such a sealing due to for instance damage or incorrect installation. In FIG. 2, the first opening of the pass baffle is connected to the shell-side fluid inlet 14, but it may be understood that the function of the heat exchanger can also be ensured if the first opening of the pass baffle is connected to the shell-side fluid outlet 16. The pass baffle may be in the cross-sectional form of a half moon, with a lower side which is substantially planar and an upper side which has a half circle cross sectional shape. To increase the thermal efficiency of the heat exchanger, at least one side of the pass baffle may be thermally insulated. The first opening of the pass baffle can be fluid tight connected to a shell fluid connection. Easy access to the shell fluid connection can be made by installing a spool piece as known in the art in connection with the shell nozzle.

(7) Attachment or detachment of the first opening of the pass baffle may be done from the outside of the shell, through the shell-side fluid inlet or outlet which the first opening of the pass baffle is connected or is to be connected to. When shell-side fluid enters the shell, it is according to the invention forced to pass through the enclosure formed by the pass baffle when performing one of the passes through the shell and the only source of leak is the connection of the first opening of the pass baffle to the shell-side fluid inlet or outlet and not as previously known in the art, the entire length of the pass baffle.

(8) While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the invention principals, it will be understood that the invention may be embodied otherwise without departing from said principals.