EP0218104A1 - Turbo heat exchanger - Google Patents

Abstract

The heat exchanger WT is a smooth tube heat exchanger whose thin- walled tubes are welded at both end faces gas-tight directly to one another and to the housing. It is built up using a modular construction kit. The heat exchanger WT operates in the low pressure region according to the cross-counterflow principle, and is used both for gas/gas and liquid systems. It offers substantial advantages in the case of aggressive and dirty media with a tendency to form precipitations. The heat exchanger is used in process engineering processes in which thermal energy is to be exchanged or recovered. This applies particularly to combustion processes which operate with large quantities of gas and high exhaust gas temperatures, and for processes in which solvents circulate. <IMAGE>

Description

The invention relates to an apparatus for the intensive exchange of heat between two hermetically separated media, a large surface area being achieved in that a multiplicity of thin-walled tubes are tightly connected in parallel without the use of tube sheets.

The currently known tubular heat exchangers all have in common that the tubes are inserted at both ends in perforated plates, and the tubes can be connected to the base and sealed by rolling, soldering, gluing or welding into the perforated base.

• - Aufwendige Herstellung von Lochböden
• - Lochböden benötigen meist sehr große Wandstärken, um ein Verziehen bei der Bearbeitung und im Betrieb zu vermeiden, damit werden die Apparate sehr schwer.
• - Lochabstand und damit engster Rohrabstand sind begrenzt durch die Bearbeitbarkeit beim Lochen (Bohren, Stanzen) sowie die Stabilität des Bodens
• - Spaltkorrosion kann meistens, insbesondere bei preiswerten Ausführungen, nicht vermieden werden.

This version has a number of disadvantages:

• - Elaborate production of perforated floors
• - Perforated floors usually require very large wall thicknesses to avoid warping during processing and operation, which makes the apparatus very heavy.
• - Hole spacing and thus the narrowest pipe spacing are limited by the machinability when punching (drilling, punching) and the stability of the floor
• - Crevice corrosion can usually not be avoided, especially with inexpensive designs.

The invention has for its object to provide a light and inexpensive tubular heat exchanger made of corrosion-resistant material, in which the two media involved in the heat exchange are hermetically sealed, and in which at least the surfaces in contact with the media are designed so smooth that neither dreaded crevice corrosion can occur, dirt still carried in the medium can adhere to hard-to-clean limbs.

These requirements must be met especially in heat recovery systems in the chemical industry e.g. the dryer exhaust air must be fulfilled.

This object is achieved in that the individual tubes are expanded at their two ends to form an equilateral hexagon, the width across flats of which is just slightly larger than the tube diameter. As a result, these pipes can be placed in parallel so that a honeycomb pattern is created on the front, with the individual pipes only touching each other along straight lines at the ends, while the cylindrical pipe middle parts keep a small distance from each other and so all-round washing of the pipe wall on the outside by one medium allow while the other medium flows through the tubes inside. The tube ends are designed so that the hexagonal cross-section is maintained over several millimeters of tube depth, so that the tubes lie flat against one another on these hexagonal prisms.

The seal between the two media is now very easy to make, e.g. by gluing, soldering or especially welding the pipe ends along the hexagonal contact surfaces.

With electric welding it is possible to work practically without the addition of wire and very thin-walled tubes can be used.

For the heat exchange between two gas flows, the tubes in the middle part can also have an elliptical cross-section instead of a cylindrical one, so that the medium flowing through the tube has a very favorable hydraulic diameter relative to the circumference and thus to the exchange surface, and for the outside Medium flowing around the pipes has a very low flow resistance based on the specific volume flow.

• - Aufbau eines hermetisch dichten Röhrenbündelwärmetauscher nur aus Ruhren ohne vorgelochte Endböden.
• - Verwendung sehr dünnwandiger Rohre
• - Sehr leichte Apparate zur Verwendung in Lufttechnischen Anlagen.
• - Sehr steifer Aufbau eines Bündels
• - Einfache Schweißtechnik beim Schweißen der Rohre.
• - Auf der Stirnfläche und den Rohrinnenseiten sind äußerst glatte Oberflächen erzielbar
  • dadurch : - keine Spaltkorrosion
  • - geringe Verschmutzungsgefahr
  • - leichte Abreinigung auch während des Betriebes durch Wasser- oder Dampfstrahl
• - Auf den Rohraußenseiten hat man bei elliptischem Rohrquerschnitt :
  • - geringe Strömungswiderstände
  • - wirbelarme Strömung und damit geringe Verschmutzungsanfälligkeit
• - Der Sechskant-Querschnitt der Rohre erlauben ein Verdrehen der Rohre beim Zusammensetzen jeweils um 60°. D.h. bei elliptischen Rohrmittelteil können die außenliegenden Strömungskanäle beliebig gelenkt werden.
• - Bei rundem Rohrmittelquerschnitt lassen sich große Röhreninnenvolumina bei kleinen Rohraußenvolumina eines Rohrbündels verifizieren; das ist wichtig bei Wärmetausch zwischen sehr unterschiedlichen Medien.

The following important advantages can be achieved with the present invention:

• - Construction of a hermetically sealed tube bundle heat exchanger only from Ruhr without pre-perforated end plates.
• - Use of very thin-walled pipes
• - Very light apparatus for use in ventilation systems.
• - Very rigid structure of a bundle
• - Simple welding technique when welding the pipes.
• - Extremely smooth surfaces can be achieved on the end face and the inside of the pipe
  • thereby: - no crevice corrosion
  • - low risk of contamination
  • - Easy cleaning even during operation by water or steam jet
• - With an elliptical tube cross-section, one has on the outside of the tube:
  • - low flow resistance
  • - Low vortex flow and thus low susceptibility to pollution
• - The hexagonal cross-section of the tubes allows the tubes to be rotated by 60 ° each time they are assembled. This means that in the case of an elliptical pipe center part, the external flow channels can be directed as desired.
• - With a round pipe center cross-section, large inner tube volumes can be verified with small outer tube volumes of a tube bundle; this is important when exchanging heat between very different media.

Claims (4)

1.) Pipe bundle - heat exchange apparatus with two hermetically separated media rooms, characterized in that the individual pipes are expanded at both ends over a depth of several millimeters to form a hexagonal cross-sectional profile, the outer width of which is slightly larger than the outer pipe diameter, and which without Hole end plates are assembled into a tube bundle with honeycomb-shaped end faces and are tightly connected to one another by welding, soldering or gluing the hexagonal contact surfaces or lines. 2.) Tube bundle - heat exchanger - Apparatus according to claim 1, characterized in that the individual tubes in the middle part (about 90% of the tube length between the hexagon ends are pressed to an elliptical cross section. 3.) Pipe bundle - heat exchanger - Apparatus according to claim 1 and 2, characterized in that the longitudinal axis of the ellipse can be arranged rotated in a 60 ° grid, so that any flow control behavior can be produced from quasi linear to constantly deflected flow. 4.) Pipe bundle - heat exchanger - apparatus according to claim 1, characterized in that the outer border of the end faces are supplemented by welding pre-cut sheets to rectangular, hexagonal or round apparatus end faces.

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