EP0555078A1 - Echangeur de chaleur avec surface raclée - Google Patents

Echangeur de chaleur avec surface raclée Download PDF

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Publication number
EP0555078A1
EP0555078A1 EP93300811A EP93300811A EP0555078A1 EP 0555078 A1 EP0555078 A1 EP 0555078A1 EP 93300811 A EP93300811 A EP 93300811A EP 93300811 A EP93300811 A EP 93300811A EP 0555078 A1 EP0555078 A1 EP 0555078A1
Authority
EP
European Patent Office
Prior art keywords
heat exchange
medium
heat exchanger
exchange medium
tubes
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93300811A
Other languages
German (de)
English (en)
Inventor
David George Finch
Nicholas Simon Hall-Taylor
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Chemtech International Ltd
Original Assignee
Chemtech International Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Chemtech International Ltd filed Critical Chemtech International Ltd
Publication of EP0555078A1 publication Critical patent/EP0555078A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
    • F28F19/008—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using scrapers

Definitions

  • This invention relates to scraped surface heat exchangers and more particularly heat exchangers of such type for use in the heating of viscous fluids.
  • a common type of heat exchanger is one comprising a pair of concentric tubes with a medium whose temperature is to be changed passing through the inner tube and a heating or cooling medium passing through the gap between the two tubes.
  • a heat transfer surface i.e. the internal surface of the inner tube
  • one or more scraper blades carried on a central shaft is/are rotated within the inner of the two concentric tubes.
  • any such blade is generally angled to the transfer surface, the rotational movement of the blade is essentially a radial extension of the rotated movement imparted by means of drive means to the central shaft.
  • scraper blades Although termed scraper blades, it is emphasized that the primary function of the blades is as already stated. Heat exchangers with such blades are generally not required to effect any significant removal from the internal surface of the inner tube of scale or other deposits such as may form thereon with continued use of those heat exchangers in which cooling of fluids from which solids may deposit is to be effected. If the medium being heated were scale forming, if anything the design of such scraper blades would be such that they might even cease to function. Indeed there have been devised more satisfactory types of heat exchanger where scale deposit is a particular problem and removal of material which has already undergone heat exchange from the vicinity of the exchanger surface is less of a problem.
  • EP-A-369 851 comprises a helical element mounted in a heat exchanger tube for free rotation therein driven by the introduction of fluid into the chamber for undergoing heat exchange.
  • the surface of the helical blade most remote from the axis of rotation thereof is sharpened to achieve scraping of scale from the internal surface of the heat exchange tube as the blade rotates.
  • a further problem is that, in order to maintain the throughput of viscous fluid through a heat exchanger, it is subjected to a predetermined pressure as it is fed into the heat exchanger. As the viscosity increases through the heat exchanger's length, so does the pressure drop observed within the fluid undergoing heat exchange increase. Consequently the pressure generated by the feed pump has to be increased and as a consequence the designed operating pressure of the scraped surface heat exchanger has to be increased. This necessitates increasing the wall thickness of the inner tube leading, in consequence, to a reduction in the rate of heat transfer.
  • a scraped surface heat exchanger comprising a pair of concentric heat exchanger tubes with a scraper blade-carrying shaft being disposed axially within the inner of the tubes and adapted for connection to rotational drive means, inlet and outlet means being provided to both a chamber defined by the inner tube and to an annular chamber formed between the two tubes, characterised in that a helical scraper blade extends along the length of the shaft within the inner chamber and contacts the internal surface of the inner tube with a contact sufficient to allow the blade to rotate within the inner tube when conveying through the inner tube by means of the helical blade a fluid medium to undergo heat exchange with a heat exchange medium in the outer chamber.
  • a method of effecting heat exchange between a heat exchange medium and a medium which is to undergo heat exchange with such medium in a heat exchanger under conditions such that it will increase in viscosity as it passes through the heat exchanger which comprises conveying the latter medium through the inner of a pair of concentric tubes between which flows a heat exchange medium, characterised in that the conveying taking place under the action of a rotating helical blade making intimate contact with the inner surface of the inner tube.
  • the apparatus used in carrying out the present invention will differ from that conventionally employed mainly in respect of the blade provision within the inner chamber.
  • the conventional essentially flat scraper blades are replaced by a single or preferably a set of multi-start helically wound fins on the rotating shaft within the inner chamber. These are designed so that there is a close contact between the top of the flights of the fins and the inner surface of the inner tube. This maintains the advantage, of the scraped surface action, although at a slightly lower efficiency, while, however, ensuring that the material being conveyed is successfully carried right through the heat exchanger.
  • the consequent advantages of this arrangement are:
  • the heat exchange effect may indeed be enhanced by utilizing a hollow shaft which allows cooling/heating medium to be passed within the shaft close to the material to be cooled or heated as the shaft rotates.
  • This lowered efficiency can nevertheless be improved to some extent by coating the shaft/material interface with a low friction material such as polytetrafluoroethylene.
  • the heat exchanger shown diagrammatically therein is designed for supply of medium to be heated or cooled through an inlet pipe 1 into the interior 2 of the inner tube 3 of a pair of concentric tubes of which the outer tube 4 has a diameter such as to define an annular chamber 5 between the outer tube and the inner tube for throughflow of heat exchange medium to be introduced through inlet pipe 6 to flow in the opposite direction to the material introduced through pipe 1.
  • An outflow pity 7 serves for removal from the interior 2 of the inner tube 3 of material which has undergone heat exchange with the heat exchange medium and a pipe 8 serves for removal of heat exchange medium from the annular chamber 5.
  • a shaft 9 Passing along the axis of the arrangement and more particularly the centre line of inner tube 3 is a shaft 9 connected at its ends to appropriate drive means (not shown) and which carries within the tube 3 a plurality of radial scraper blades 10 of which only one is shown and which have a diameter such as to make contact with the internal surface of tube 3.
  • the drive means for the shaft 9 and closure means for the ends of the respective tubes 3 and 4 may be of conventional design and do not require discussion here.
  • Figure 2 is aligned with the heat exchanger of Figure 1 and shows in a very general manner the temperature change which is experienced by a viscous fluid introduced into the heat exchanger of Figure 1 through pipe 1 to undergo cooling as it travels the length of tube 3.
  • heat exchange initially takes place with the heat exchange medium while the latter is at its highest temperature, with more effective cooling taking place at the right hand end of the heat exchanger where the heat exchange medium, having just been introduced, is at its coolest. This would be expected to mean that the temperature of fluid within the inner tube would decrease at an ever increasing rate along the length of the heat exchanger.
  • the pressure to which the viscous medium is subject as it passes through the heat exchanger should remain constant as represented by curve C.
  • the operating pressure i.e. the feed pressure of the viscous medium has to be increased by an amount E.
  • the shaft 9 is in fact, here shown to be replaced by a composite arrangement comprising a sleeve 20 carrying a helical blade 21 formed integrally therewith and intended to act as a conveyor for the viscous fluid undergoing travel through the interior of the inner tube of a tube heat exchanger whose tube construction is not shown in Figure 3 but will typically be analogous to that in Figure 2.
  • the sleeve 20 is mounted on a compound shaft 23 which is shown in greater detail here than is the shaft 9 in Figure 2 and comprises coupling arrangements 24 and 25 at its respective ends, coupling arrangement 24 being used for coupling the shaft to rotary drive means and coupling means 25 being used for coupling the shaft to a suitable support means.
  • the shaft itself is of double tube construction comprising an inner tube 26 and an outer tube arrangement 27 to one end of which one end of the sleeve 20 is welded. At its other end the sleeve 20 is welded to the coupling arrangement 24.
  • An annular passage 28 exists between inner tube 26 and outer tube arrangement 27 and sleeve 20 and serves for introduction of heat exchange medium to provide additional cooling of viscous fluid conveyed by the helical blade 21 from left to right in the sense of Figure 3 to that achieved by heat exchange medium in the outer of the heat exchange tubes (not shown).
  • This additional heat exchange medium enters the annular passage 28 to pass in counterflow to the viscous medium before entering a cylindrical chamber 30 at the left hand end of the heat exchanger through openings 31 to pass thence into cylindrical passage 29 in the interior of inner tube 26 to flow therethrough and out of the shaft 23 at 32.
  • the portion of tube 26 within sleeve 20 passes through a cylindrical support body 33 to which the sleeve 20 is attached by spot welding as shown at 34.
  • the apparatus of Figure 3 has been described particularly with respect to the enhancing of conveying and cooling of a viscous medium which would normally be expected to undergo viscosity increase and temperature increase as it passes through the heat exchanger, it should be appreciated that variants in the operation and use of the heat exchanger may be contemplated.
  • the internal cooling may be directed into the compound shaft 23 at 32 to pass initially through inner tube 26 to leave the shaft arrangement through annular passage 28.
  • the apparatus can be used conveniently with any medium which is to undergo heat exchange with a heat exchange fluid, whether it is to undergo heating or cooling. It is not limited to the above described use with viscous media.
  • the helical flight of the helical blade shown at 21 in Figure 3 carries a thin strip of metal or plastics material along its length.
  • Such strip can be located in a slot in the helical flight angled in the upstream direction so that one surface of the strip presses against the stationary inner tube surface. Not only is better scraping action then achieved, but material passing over the flight will be reduced or stopped and hence the pump or drive action of the blade will be improved.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
EP93300811A 1992-02-05 1993-02-04 Echangeur de chaleur avec surface raclée Withdrawn EP0555078A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9202409 1992-02-05
GB929202409A GB9202409D0 (en) 1992-02-05 1992-02-05 Scraped surface heat exchanger

Publications (1)

Publication Number Publication Date
EP0555078A1 true EP0555078A1 (fr) 1993-08-11

Family

ID=10709856

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93300811A Withdrawn EP0555078A1 (fr) 1992-02-05 1993-02-04 Echangeur de chaleur avec surface raclée

Country Status (2)

Country Link
EP (1) EP0555078A1 (fr)
GB (1) GB9202409D0 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104351907A (zh) * 2014-10-30 2015-02-18 何隆涛 一种刮板式高粘度流体食品杀菌器
CN109341376A (zh) * 2018-10-29 2019-02-15 湖北君集水处理有限公司 一种粉末活性炭再生设备余热回收装置
US11149940B2 (en) 2010-09-03 2021-10-19 Greg Naterer Heat exchanger using non-pure water for steam generation

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4073339A (en) * 1976-12-06 1978-02-14 The De Laval Separator Company Swept surface heat exchanger
EP0400700A1 (fr) * 1989-05-24 1990-12-05 Unilever N.V. Echangeur de chaleur à surface raclée
DE3939778A1 (de) * 1989-12-01 1991-06-06 Wilhelm Haeberle Einrichtung zur vermeidung der grenzschicht bei waermetauschern

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4073339A (en) * 1976-12-06 1978-02-14 The De Laval Separator Company Swept surface heat exchanger
EP0400700A1 (fr) * 1989-05-24 1990-12-05 Unilever N.V. Echangeur de chaleur à surface raclée
DE3939778A1 (de) * 1989-12-01 1991-06-06 Wilhelm Haeberle Einrichtung zur vermeidung der grenzschicht bei waermetauschern

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11149940B2 (en) 2010-09-03 2021-10-19 Greg Naterer Heat exchanger using non-pure water for steam generation
CN104351907A (zh) * 2014-10-30 2015-02-18 何隆涛 一种刮板式高粘度流体食品杀菌器
CN109341376A (zh) * 2018-10-29 2019-02-15 湖北君集水处理有限公司 一种粉末活性炭再生设备余热回收装置

Also Published As

Publication number Publication date
GB9202409D0 (en) 1992-03-18

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