DE3502116A1 - Shell-and-tube heat exchanger with expansion compensation for heat exchange of gases - Google Patents

Abstract

The invention relates to a shell-and-tube heat exchanger with expansion compensation for heat exchange of gases with high temperature differences and relatively small differences in the operating pressures, where comparatively small gas leaks are not a problem. In this heat exchanger, the tubes of the tube bunch at least are supported in an axially sliding manner in narrow gaps in matched bores in a tube plate, and can move freely in the case of thermal expansion.

Description

Shell and tube heat exchanger with expansion compensation

for the heat exchange of gases The invention relates to a shell and tube heat exchanger with expansion compensation for heat exchange of gases; whose operating pressures differ relatively little.

In shell and tube heat exchangers occur because of thermal expansion the construction materials used and the temperature differences that arise during operation Tensions between the tube bundle, the tube sheets and the jacket, leading to unwanted deformation of the heat exchanger and lead to material damage can.

These tensions are usually present in known heat exchangers thereby reduced or avoided that the structural elements of the heat exchanger are connected with elastic compensators, which are caused by thermal expansion Catch movements of the construction elements. From DE-OS 26 08 977 e.g.

a shell and tube heat exchanger for gases known, both of which tube sheets are connected to the shell of the heat exchanger via elastic compensators, annular elastic thermal expansion permitting elements made of relatively thin material. Such constructions are technically complicated, expensive to manufacture and can lead to undesired vibrations of the tube bundle under certain operating conditions s in the heat exchanger jacket, which can cause material damage.

Elastic expansion joints on the shell of a shell and tube heat exchanger usually only relieve the axial stresses in the tube bundle, but it does arise during operation of the heat exchanger in the radial direction via the tube sheets or the Tube bundles have a different temperature distribution, so result within These components have stresses that lead to plastic deformation and material damage being able to lead.

According to another known embodiment, the Tube of a tube bundle heat exchanger firmly welded to one tube sheet, with the other tube sheet is sealed by means of individual glands for each tube, which allow free expansion of the tubes in the second tube sheet in the axial direction.

The production of a large number of stuffing boxes is expensive and consumes space, so that such heat exchangers are often uneconomical and one take up too much space. Stuffing boxes should be used at high gas temperatures because of the limited temperature resistance of good sliding sealing materials restricted in stuffing boxes.

The invention is based on the object of a simple and economical tube bundle heat exchanger for the heat exchange of gases with to create high temperature differences, the operating pressures of which are proportionate differ little.

This object is achieved in that the tubes of the tube bundle heat exchanger are mounted axially movably in matching bores at least in a tube sheet.

The width of the gap between the pipe outer wall and the bore is in this case 0.1 to 1%, preferably 0.25 to 0.5, of the pipe outer diameter on this Job.

According to a preferred embodiment, the one ends are the tubes firmly connected to one tube sheet, the other ends of the tubes in matching ones Bores of the second tube sheet mounted so as to be axially movable.

To reinforce the throttling effect of the gap between the pipe outer walls and holes in the tube sheet for the passage of gas are in the inner surfaces of the Bores grooves milled in, the width of which is 5 to 25 times the width of the gap amounts to.

When exchanging heat between many technical gases, e.g. between hot flue gas and thus the air to be heated is the complete sealing of the two gas spaces against each other not always necessary, especially if between the Gases a difference in the operating pressures in the heat exchanger of less than 10%, at normal pressure a pressure of less than 100 mbar, preferably less than 50 mbar.

In a preferred embodiment, heating gas flows at a high temperature through the tubes of the heat exchanger, the gas to be heated through the space between the tubes and the jacket of the heat exchanger.

The shell and tube heat exchanger according to the invention is particularly suitable as an air preheater that is heated with flue gas.

The shell and tube heat exchanger according to the invention has in comparison to known heat exchangers with expansion compensation the advantage of the simpler, space-saving and more economical construction.

It is maintenance-free in operation and less susceptible to undesirable effects Vibrations and against delay in the heat exchange of gases with large temperature differences.

An embodiment of the invention is shown in the drawing and is described in more detail below.

1 shows a longitudinal section through the tube bundle heat exchanger with expansion compensation.

2 shows a longitudinal section through a tube end of the tube bundle heat exchanger, which is inserted into a bore in the second tube sheet and there in a narrow Gap is axially movable.

Structure and mode of operation of an embodiment of the shell and tube heat exchanger according to the invention are shown in FIGS. 1 and 2.

Heating gas is fed into the collecting space 8, from where it is distributed on the tubes 5 of the tube bundle 3, flows through them, arrives in the second collecting space 9 and leaves the heat exchanger there.

The gas to be heated passes through the nozzle 10 into the space between the jacket 4 of the heat exchanger and the tubes 5 and leaves this Space through the nozzle 11.

The individual tubes 5 of the heat exchanger are fixed at one end welded to the tube sheet 1 and at the other end in matching holes in the tube sheet 2 introduced and there slidingly mounted in narrow gaps 6. According to the invention can several tube sheets 2 are also provided, in which the tubes 5 are slidably supported are.

There are two grooves 7 in the inner surfaces of the bores in the tube sheet 2 engraved, which reinforce the throttling effect of column 6.

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Claims (5)

Patent claims for shell and tube heat exchangers with expansion compensation for the heat exchange of gases whose operating pressures are relatively low differentiate, characterized in that the tubes <5) of the tube bundle (3) at least in a tube sheet (2) in matching bores axially movably mounted are, the width of the gap (6) between the pipe outer wall and the bore 0.25 to 0.5% of the pipe outside diameter at this point. 2. Shell and tube heat exchanger according to claim 1, characterized in that that one ends of the tubes (5) are firmly connected to the tube sheet (1) and the other ends of the tubes (5) axially in matching bores in the tube sheet (2) are movably mounted. 3. Shell and tube heat exchanger according to claim 1 and 2, characterized in that that grooves (7) are milled into the inner surfaces of the bores in the tube sheet (2), the width of which is 5 to 20 times the width of the gap (6) between the pipe outer wall and bore is. 4. Shell and tube heat exchanger according to claim 1 to. 3 characterized by that between the gases there is a difference in the operating pressures in the heat exchanger of is less than 50 mbar. 5. Shell and tube heat exchanger according to claim 1 to 4, characterized in that that it is operated as an air preheater with heating gas, which through the interior of the Pipes (5) wrd.