CH662644A5

CH662644A5 - CONSTRUCTION TO IMPROVE THE HEAT TRANSFER FACTOR OF LIQUIDS FLOWING IN TUBES OF A HEAT EXCHANGER.

Info

Publication number: CH662644A5
Application number: CH468/84A
Authority: CH
Inventors: Arpad Dr Dipl-Ing Bakay; Gyoergy Dipl-Ing Bergmann; Janos Dipl-Ing Bodas; Gabor Dipl-Ing Csaba; Laszlo Dr Dipl-Ing Forgo
Original assignee: Transelektro Magyar Villamossa
Priority date: 1983-02-01
Filing date: 1984-02-01
Publication date: 1987-10-15
Also published as: DE3401606C2; JPS59191893A; FR2540234A1; GB2135439A; DE3401606A1; GB8402224D0; HU187016B; BE898795A; FR2540234B1; ZA84644B; DE8401350U1; NL8400230A; GB2135439B

Description

Die Erfindung wird anhand vorteilhafter Ausführungsbei-35 spiele, mit Hilfe der beiliegenden Zeichnungen näher erläutert; es zeigen The invention is based on advantageous Ausführungsbei-35 games, explained in more detail with the help of the accompanying drawings; show it

Fig. 1 eine mögliche Ausführungsform der Erfindung, 1 shows a possible embodiment of the invention,

Fig. 2 eine mögliche Ausführungsform eines Lenkele-40 ments, 2 shows a possible embodiment of a steering element,

Fig. 3 eine weitere Ausführungsform der Erfindung. Fig. 3 shows another embodiment of the invention.

Eine mögliche Form der Realisierung der Erfindung ist in Fig. 1 veranschaulicht. Die Figur zeigt ein einziges Kühlrohr 45 1 des Wärmeaustauschers. Im Kühlrohr 1 sind Lenkelemente A possible form of implementing the invention is illustrated in FIG. 1. The figure shows a single cooling tube 45 1 of the heat exchanger. Steering elements are in the cooling tube 1

2 in einer zur Längsachse des Kühlrohrs senkrechten Ebene, im Abstand hintereinander, auf einem Befestigungsdraht 3 befestigt. An beiden Enden des Rohrs 1 wird der Befestigungsdraht 3 durch Befestigungselemente 4 gehalten. Das so Lenkelement 2 lenkt das an den Rohrwand, in der laminären Grenzschicht strömende kalte Öl und das im Mittelteil des Rohres strömende warme Öl in Richtung der Pfeile, so dass das kältere Öl in Richtung des Rohrinneres und das wärmere Öl in Richtung der Rohrwand strömt. In der Fig. 1 ist der 55 Längsschnitt des mit zwei Kanälen ausgestalteten Lenkelements zu sehen. 2 in a plane perpendicular to the longitudinal axis of the cooling tube, one behind the other, fastened on a fastening wire 3. At both ends of the tube 1, the fastening wire 3 is held by fastening elements 4. The steering element 2 thus directs the cold oil flowing on the pipe wall, in the laminar boundary layer and the warm oil flowing in the central part of the pipe in the direction of the arrows, so that the colder oil flows in the direction of the pipe interior and the warmer oil flows in the direction of the pipe wall. 1 shows the longitudinal section of the steering element designed with two channels.

Gemäss einer Variante, ist das Lenkelement 2 im nicht eingebauten Zustand ein wenig grösser, als der Innendurchmesser des Rohrs 1 und wird nach erfolgter Montage infolge 60 seiner Elastizität an die Wand des Rohrs 1 angepresst. Bei einer derartigen Lösung können der Befestigungsdraht 3 und das Befestigungselement 4 weggelassen werden. According to a variant, the steering element 2, when not installed, is a little larger than the inside diameter of the tube 1 and, after assembly, is pressed against the wall of the tube 1 due to its elasticity. With such a solution, the fastening wire 3 and the fastening element 4 can be omitted.

Fig. 2 zeigt eine mögliche Ausführung des Lenkelements 2. Der aus dem Lenkring 5 gepresste Lenkkanal 6 lenkt die zwi-65 sehen die Wand des hier nicht dargestellten Rohrs 1 und den Lenkring 5 strömende Grenzschicht gegen den Mittelteil des Rohrs. Diese Lenktätigkeit wird auch von einem Sperr-Ring 7 gefördert, der gleichzeitig auch zur Anpassung an die Wand Fig. 2 shows a possible embodiment of the steering element 2. The steering channel 6 pressed out of the steering ring 5 steers the between-65 see the wall of the pipe 1 not shown here and the steering ring 5 flowing boundary layer against the central part of the pipe. This steering activity is also promoted by a locking ring 7, which is also used to adapt to the wall

20 20th

3 3rd

662 644 662 644

des Rohrs 1 dient. Zur Sicherung einer konzentrischen Anordnung ist eine Stütze 8 aus dem Material des Lenkringes 5 ausgestaltet. the tube 1 is used. To ensure a concentric arrangement, a support 8 is made of the material of the steering ring 5.

Eine weitere Verbesserung der Wärmeübergabe bringt die in der Fig. 3 veranschaulichte Ausführungsform mit sich. Hier führen die am im Rohre 1 angeordneten Befestigungsdraht 3 befestigten Lenkelemente 2 eine alternierende hin und hergehende Bewegung aus. Die Lenkelemente 2 können auch so in Bewegung gesetzt werden, indem der Befestigungsdraht 3 mit einem äusseren Bewegungsmechanismus periodisch bewegt wird. The embodiment illustrated in FIG. 3 brings about a further improvement in the heat transfer. Here, the steering elements 2 fastened to the fastening wire 3 arranged in the tube 1 execute an alternating reciprocating movement. The steering elements 2 can also be set in motion by periodically moving the fastening wire 3 with an external movement mechanism.

Eine weitere Möglichkeit nach Fig. 3 besteht darin, dass der Strom des zu kühlenden Mediums eine Feder 9 spannt, die am Befestigungselement 4 und am Befestigungsdraht 3 befestigt ist und das Lenkelement 2 in Bewegung setzt. Durch das periodische, in kurzen Intervallen vorgenommene Abstellen der Strömung des zu kühlenden Mediums wird erreicht, dass die Feder 9 den Befestigungsdraht 3 zieht und damit die Lenkelemente 2 in die Grundstellung zurück 5 bringt. Auf diese Weise ziehen die Lenkelemente 2 die kontinuierlich dicker werdende Grenzschicht von der Wand des Rohrs 1 ab und zwingen diese in den mittleren Teil des Rohrquerschnitts, wodurch die Rohrwand für das wärmere Medium freigegeben wird. Das periodische Strömen des zu l» kühlenden Mediums kann durch eine beim Eintritt des Wärmeaustauschers angeordnete, elektrisch betätigte und elektronische gesteuerte Sperrvorrichtung oder jedwelche mechanische Konstruktion erreicht werden. Es ist auch eine Lösung möglich, bei der die Bewegung mit der Energie des is strömenden Mediums durchgeführt wird. Another possibility according to FIG. 3 is that the flow of the medium to be cooled tensions a spring 9 which is fastened to the fastening element 4 and to the fastening wire 3 and sets the steering element 2 in motion. The periodic switching off of the flow of the medium to be cooled, which is carried out at short intervals, ensures that the spring 9 pulls the fastening wire 3 and thus brings the steering elements 2 back into the basic position 5. In this way, the steering elements 2 pull the continuously thicker boundary layer from the wall of the pipe 1 and force it into the central part of the pipe cross section, whereby the pipe wall is released for the warmer medium. The periodic flow of the medium to be cooled can be achieved by an electrically operated and electronically controlled locking device arranged at the entrance of the heat exchanger or by any mechanical construction. A solution is also possible in which the movement is carried out with the energy of the flowing medium.

B B

1 Blatt Zeichnungen 1 sheet of drawings

Claims

662644

2nd

PATENT CLAIMS

1. Construction for improving the heat transfer factor of viscous liquids flowing in pipes of a heat exchanger, which has steering elements, characterized in that the steering elements (2) are provided with steering channels (6) which follow the boundary layer flowing on the wall of the pipe (1) Steer inside and divide the inner space of the pipe (1) into sections perpendicular to the pipe axis.

2. Construction according to claim 1, characterized in that the steering elements (2) are arranged on a central fastening wire (3) which is fastened by fastening elements (4) in the tube (1).

3. Construction according to claim 1, characterized in that the steering elements (2) are connected to a device connected to the fastening wires (3) and suitable for carrying out a periodic movement.

4. Construction according to claim 3, characterized in that the fastening wires (3) are connected to a spring (9) and at the tube inlet there is a device which ensures the periodic flow of the cooling medium.

5. Construction according to claim 4, characterized in that an external energy-using blocking device is provided to ensure the periodic cooling medium flow.

6. Construction according to claim 4, characterized in that a locking device actuated by the energy of the flowing medium is present to ensure the periodic cooling medium flow.

The construction according to the invention serves to improve the heat transfer factor of viscous liquids flowing in pipes of a heat exchanger and having a low thermal conductivity, such as e.g. Transformer or bearing oils.

It is known that the oils used to lubricate and cool the bearings of steam turbines or gas turbines, which have to be cooled in an oil cooler in order to extract the mechanical heat loss generated in the bearings, are poor heat conductors and flow laminarly in the tubes of the heat exchanger.

As a result of the properties mentioned above, the heat transfer factor of the oils is low, which is associated with the disadvantageous consequence that the cooling requires a large-sized and costly heat exchanger.

The unfavorable heat transfer factor of the laminar flowing oils and having a poor heat conduction factor can be explained by the fact that along the pipe surface the cooled boundary layer, which flows at a low speed, acts as a heat insulation layer and blocks the heat flow from the warmer oil towards the pipe wall. While the cooled oil flows forward along the pipe wall at a low speed and thus forms a sealing layer on the pipe wall, the warm oil flows in the central part of the pipe and is hardly cooled. Heat can only flow through heat conduction.

To improve the heat transfer factor, it is customary to use a longitudinally arranged inner rib. This ensures that the heat has to travel a shorter distance in the cross section divided by the ribs, as a result of which the thermal resistance decreases. On the other hand, the disadvantage of the ribs is that the resistance, the weight and thus the production costs increase in this way.

The purpose of the invention is to eliminate the above-mentioned drawbacks with a construction which removes the colder boundary layer resulting from the laminar flow of the oil from the pipe wall and at the same time enables the warmer oil to flow in from the center of the pipe instead of this.

This solution comes with a construction according to claim

1 reached.

io The proposed construction differs significantly from the known inner ribs. While the known inner fins divide the tube space into channels that run parallel or approximately parallel to the longitudinal axis of the tube, the proposed construction 15 divides the tube space into lines that run perpendicular to the tube axis, the boundary layer of the separated sections that arises on the tube wall alternating with that in FIG the middle of the pipe is forced to flow warmer oil. In this way, layers of oil flowing parallel to the longitudinal axis of the tube also arise here. There is no separating surface between them, and as they flow forward in the pipe, there is a repeated change of location.

An essential feature of traditional inner fins is that they have an area similar in size to the inner surface of the tube.

The area of the construction according to the invention, on the other hand, is considerably smaller and plays no role in the heat transfer. The base material of the traditional interior 30 ribs is a metal that conducts heat well. The thermal conductivity of the construction according to the invention is not essential, so that the construction can even be made from a plastic.