GB2024401A

GB2024401A - Heat exchanger

Info

Publication number: GB2024401A
Application number: GB7922458A
Authority: GB
Original assignee: FUNKE WAERME APPARATE KG
Current assignee: FUNKE WAERME APPARATE KG
Priority date: 1978-07-03
Filing date: 1979-06-28
Publication date: 1980-01-09
Also published as: FR2430586A1; IT1122007B; JPS5538492A; IT7924052A0; DE2829121A1

Abstract

Heat exchange apparatus comprises a closed casing subdivided by at least one transverse bulkhead 16 into two cylindrical chambers 18,20 each having a fluid inlet (e.g. 22 or 24) and a fluid outlet (e.g. 26 or 28), and heat transfer tubes 40 (e.g. heat pipes) sealed into the bulkhead(s) and extending therefrom into each said chamber, said tubes acting to transfer heat between two fluids (e.g. oil and cooling water) flowing respectively through the chambers 18,20. The bulkhead may comprise an elastic disc sandwiched between two plates each comprising a chamber end-wall. Baffles 36 provide tortuous flow paths for the fluids. <IMAGE>

Description

SPECIFICATION Improved heat exchanger The invention relates to a heat exchanger comprising a cylindrical vessel having two chambers and a series of heat transfer tubes extending between the chambers and containing a heat transfer medium to effect heat exchange between the chambers. This type of exchanger permits heating a liquid in one chamber while cooling another liquid in the second chamber.

Heat exchangers are widely used in technology today for cooling of various types of commercial equipment in order to prevent the heat, which deveiops during operation, from causing damage or destruction to the equipment. Heat exchangers serve also to recover the heat and thereby to conserve energy.

Heat exchangers are subject to wear and deterioration. For instance, heat transfer tubes break because of corrosion or fatigue or aging of the material. When this happens in a two-chamber heat exchanger the materials being treated may mix with each other, which can have serious consequences-a fact that is easily recognizable in the example of water-cooled oil ciroulation. If water gets into the oil system of an installation, sufficient lubrication is no longer guaranteed and the danger of destruction of the installation exists.

Likewise, the danger exists that the liquid to be cooled, in this case oil, may get into the cooling water and thus lead to environmental pollution.

Such a danger exists to an increased degree if the heat exchanger media are corrosive. The use of non-corroding and highly resistant materials for the heat exchanger apparatus is not possible in most cases because such materials are very expensive.

The object of the invention is to provide a heat exchanger of the type mentioned in which the mixing of the heat exchange media is prevented in case the heat transfer tubes break.

The danger that the heat exchanger media may mix in case of a break of one or of several heat transfer tubes is avoided by the design defined in the invention. If such a tube breaks, only that transfer tube is put out of action. This reduces the capacity of the heat exchanger by a measured amount. The mixing of the media is avoided by means of the bulkhead which is designed as a sealed separating wall between the two chambers. The probability is very slight that a break in the transfer tube will take place simultaneously on both sides of the bulkhead. By measuring the drop of the capacity of the exchanger, one can ascertain in a simple manner an indication of the defect and promptly can take care of a replacement. The heat exchanger of the invention can be used very well as a safety cooler.

Various details in the means for sealing the two chambers and the tubes in the bulkhead are described below. In one modification of the invention, in case of leakage around a tube through the bulkhead, the fluid is drained to the outside and not into the other heat exchange chamber of the heat exchanger.

The invention will now be explained in detail by means of the attached drawing in which one embodiment of the invention is illustrated.

The drawing shows a heat exchanger 2 for two liquid media between which interchange of heat is to take place. The heat exchanger 2 consists of two cylindrical parts 4 and 6 each of which consists of a jacket 8, 10, a head 12, 14 and a common bulkhead or bottom 16 which separates the two heat exchanger parts 4 and 6 from each other whereby two chambers 18 and 20 are formed.

The chambers 18 and 20 have short feed pipes 22 and 24 for the inflow and short pipes 26 and 28 for the outflow of the liquids to be treated.

The heat exchanger parts 4 and 6 are connected with each other by means of ring flanges 30 and 32 between which the outer periphery of the bulkhead 1 6 is clamped. On the inside wall of the jackets 8 and 10 of the two heat exchanger parts there are arranged baffle plates 34 and 36 to produce a spiral fluid flow as indicated in broken lines 38. Chamber 18 may serve as a cooling chamber and be connected, for instance, to a line through which hot oil is circulating. Chamber 20 may serve as a heating chamber and can be connected to a source of cold water for absorbing heat transferred from the oil.

In order to carry out the heat transfer between the two chambers 18 and 20 or between the two media present in the chambers, heat transfer tubes 40 are provided which extend from one end of the heat exchanger to the other end through the baffle sheets 34, 36 and through the bulkhead 1 6.

The tubes 40 are sealed in the bulkhead 16 so that a transfer of liquid or fluid from chamber 18 into chamber 20 and vice versa is not possibie.

For the purpose of sealing, the heat tubes can, for instance, be soldered, cemented or rolled into the bulkhead 1 6.

In place of a common bulkhead 16, separate bottoms can be provided for each part 4 and 6 or for each chamber 18 and 20, respectively. In this case, sealing can be carried out, for instance, by means of an elastic disc provided with holes for the tubes 40 and sandwiched between the two bottoms. When the two chamber bottoms are secured together to provide a bulkhead, the disc is compressed tightly to the bottoms and to the tubes whereby secure sealing can be achieved.

The chamber bottoms can also be designed in such a way that the two bottoms are arranged at a distance from each other and that the space between the bottoms is not sealed toward the outside but is open to the outside. Thus, in case of leakage around a tube extending through the bottom or bulkhead, the liquid, which leaks out, can drain off to the outside and does not get into the other heat exchanger chamber.

The casting method can also be used advantageously for the production of the heat exchanger. The tube bottom or bulkhead is cast simultaneously with the tubes so that in one operation there can be achieved a tight and fixed connection between the tubes and the bulkhead.

The heat transfer from one chamber to the other chamber of the heat exchanger takes place by means of a heat transfer medium within the closed heat transfer tubes, and, as a rule, is an evaporating liquid. The tubes may be provided with external fins in order to enlarge the heat transfer surface.

If, as assumed before in the example above, chamber 18 is connected to circulating hot oil and chamber 20 is connected to circulating cold water by means of which cooling of the oil is to be carried out, the zone of the chamber 18 represents the heating zone, i.e., the zone where the heat transfer medium is heated, thereby cooling the oil.

The zone of the chamber 2Arepresents the cooling zone, i.e. where the heat transfer medium is cooled by the water. The medium is evaporated in the left end of the tube. It then flows to the right end of the tube and gives off its heat there to the water, condenses and flows back. The return of the liquid can be improved by the suction effect of a capillary structure on the inside wail of the tubes.

The direction of flow of the heated transfer fluid is indicated by arrows 42 and the direction of the returning cooled transfer fluid is indicated by arrows 44.

If a tube breaks, for instance, in the heat exchanger part 4, the oil enters the broken tube but cannot get into the water in chamber 20. If a tube breaks in the-heat exchanger part 6, the water enters the broken tube, it is true, but it cannot mix with the oil.

The mixing of oil and water is possible only in the case of a simultaneous break of a tube on both sides of the bulkhead. However, such a break is very improbable.

In case of a break of a tube, the capacity of the heat exchanger is reduced. This decrease of capacity can be readily measured by known means to signal a defective tube.

Claims

1. A heat exchanger comprising a hollow cylindrical vessel closed by lids and having short feed pipes for the inflow and short pipes for the outflow, said vessel having at least one tube bulkhead and tubes disposed in the bulkhead in which the heat exchanger comprises at least two cylindrical chambers, that the tube bulkheads are constructed to form a dividing wall intermediate the chambers, and that the tubes are heat transfer tubes sealingly disposed in the tube bulkhead and effecting the heat transfer from one chamber to the other chamber.

2. A heat exchanger according to claim 1, in which a common bulkhead is provided for both chambers.

3. A heat exchanger according to claim 1, in which a flexible sealing disc provided with holes for the heat transfer tubes is disposed intermediate the bulkheads, said sealing discs being compressed tightly to the bulkheads and the tubes when the bulkheads are secured together.

4. A heat exchanger according to claim 1 or 2, in which the seal between the heat transfer tubes and the bulkhead or the bulkheads is provided by welding, soldering, glueing or rolling.

5. A heat exchanger according to any one of the preceding claims, in which the bulkhead or the bulkheads are casted and that the heat transfer tubes are casted simultaneously tight and fixed with the bulkhead or bulkheads.

6. A heat exchanger according to any one of the preceding claims, in which the open facing sides of the chambers are each provided with ring flanges by which the chambers are connected eventually detachably with each other and between which the bulkhead or the bulkheads and eventually additional sealing rings or the sealing discs are clamped.

7. A heat exchanger according to any one of the preceding claims, in which at least two preferably slightly spaced bulkheads are provided and that the space between the bulkheads is at least partly open to the outside.

8. A heat exchanger substantially as herein described with reference to the accompanying drawing.