Classifications

• • C—CHEMISTRY; METALLURGY
  • C13—SUGAR INDUSTRY
  • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
  • C13B25/00—Evaporators or boiling pans specially adapted for sugar juices; Evaporating or boiling sugar juices
  • C13B25/001—Evaporators or boiling pans specially adapted for sugar juices; Evaporating or boiling sugar juices with heating tubes or plates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D1/00—Evaporating
  • B01D1/06—Evaporators with vertical tubes
• • C—CHEMISTRY; METALLURGY
  • C13—SUGAR INDUSTRY
  • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
  • C13B25/00—Evaporators or boiling pans specially adapted for sugar juices; Evaporating or boiling sugar juices
  • C13B25/02—Details, e.g. for preventing foaming or for catching juice
  • C13B25/04—Heating equipment
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
  • F28F13/18—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by applying coatings, e.g. radiation-absorbing, radiation-reflecting; by surface treatment, e.g. polishing
• • 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F2245/00—Coatings; Surface treatments
  • F28F2245/02—Coatings; Surface treatments hydrophilic

Definitions

• Tube that can be used in fluid evaporation techniques, in particular edible fluid.
• the present invention relates to a tube which can be used in fluid evaporation techniques, in particular of edible fluid.
• a food fluid such as a sweet liquid or milk
• the heat exchanges on either side of the evaporator tube are very important because of the high energy balances used in this field.
• a method of manufacturing a so-called fluted tube in which a basic metal strip is corrugated, in the width direction, between two pairs of rollers comprising flutes.
• the corrugated metal strip is then rolled, also in the width direction, to form a tube having a corrugated profile, in section.
• the purpose of the tube thus produced with the corrugated strip is to increase the heat exchange surface for the same nominal tube diameter.
• the production of the corrugations requires the use of a relatively thin sheet metal strip, of the order of 0.5 mm, to ensure shaping of the corrugations.
• the tube produced from a sheet of thin thickness leads to a risk of perforation during pitting corrosion of the tube following successive pickling treatments.
• the corrugation also has the function of stiffener, which allows the use of a thin base plate.
• one of the rollers has a straight generator parallel to its axis of rotation and the other roller has grooves intended to form said grooves on one face of the strip laminated steel
• the tube thus produced, from the laminated strip only has grooves on the outside, said grooves, the purpose of which, also in this case, is to increase the heat exchange surface of the tube for the same diameter nominal
• the function of grooving or corrugation is to increase the heat exchange surface without taking account of the wettability of the fluid.
• the object of the invention is to propose a welded stainless steel tube, usable in evaporators, in particular in the sugar and dairy industry, the tube having an improved surface quality and a structure of its exchange surface ensuring a quality also improved heat exchange
• the subject of the invention is a welded stainless steel tube which can be used in techniques for the evaporation of a fluid, in particular a food fluid which is characterized in that it comprises, on at least one of its external surfaces. or internal heat exchange, mostly smooth, localized means of accumulation and flow of condensations created on the smooth heat exchange surface
• the means of accumulation and flow of condensations are distributed longitudinally to said tube and uniformly, - the means of accumulation and flow of condensations consist of gradients in the form of shoulders extending over the length of said tube and the height of which is less than 0.5 mm and preferably less than 0.2 mm.
• the means of accumulation and flow of condensations consist of hollow imprints distributed over the length of said tube, - the imprints have a width of between 0.2 and 1 mm, occupying in a distributed manner, less than 50% from the periphery of said tube,
• the impressions have a rounded bowl shape
• the means of accumulation and flow of condensations consist of steps, distributed around the periphery of the tube and occupying less than 50% of the periphery of said tube.
• At least the opposite surface of the surface comprising the localized means of accumulation and flow of the condensations of the tube has a roughness of less than 0.2 ⁇ m, of the bright annealing type 2R.
• the invention also relates to a method for improving the heat exchanges in a heat exchanger for the evaporation of a fluid, in particular in the food industry, the exchanger comprising tubes intended for heat exchange, characterized in that:
• the exchanger tubes are produced at least one drop in the form of a shoulder extending over the length of said tube and whose height is less than 0.5 mm, and preferably less than 0.2 mm, difference in height defining a longitudinal imprint the edge of which attracts by capillary action the film of condensed liquid which is deposited uniformly on the predominantly smooth surface of the tube.
• Figures 1 and 2 each show, in section, an example of a stainless steel tube according to the invention.
• the tube shaping line from a strip of steel includes rolling and edge-to-edge welding means of the strip.
• the line comprises a mechanical assembly comprising a so-called upper flat roller and a so-called lower roller.
• the roller for example said to be lower, has equidistant protrusions or grooves of small height providing, between them, smooth surfaces, smooth surfaces occupying mainly the surface of the strip.
• the two rollers are adapted to the width of the starting steel strip, starting strip whose width corresponds to the average perimeter of the tube to be produced.
• the mechanical assembly is placed at the head of an induction, laser or TIG welder.
• Localized means are produced with the mechanical assembly, on at least one of the surfaces of the stainless steel strip, for the accumulation and flow of condensations constituted for example by linear imprints sufficiently spaced apart to release an internal surface. or mostly smooth external of the tube.
• FIG. 1 presents in section a part of tube 1 according to the invention on which, for example, the localized means of accumulation and flow of condensations are produced on the external surface of the tube.
• the means of accumulation and flow of condensations consist, in this embodiment of unevennesses 2 and 3 in the form of shoulders extending over the length of said tube and whose height is less than 0.5 mm and preferably less than 0.2 mm.
• the elevations 2 and 3 in the figure define indentations 4 whose depth is less than 0.5 mm and preferably less than 0.2 mm.
• the capillary effect generated by the edge of the cavity 4 moves the film of condensation of the vapor which forms on the surface 5 of the tube, towards said cavity 4.
• the cavity 4 behaves like a gutter.
• the imprint preferably in the form of a bowl, has the advantage of effectively attracting the film of the fluid distributed over the surface of the tube so as to form droplets which will be channeled and easily eliminated.
• the object of the invention is to remove as quickly as possible the drop of water which forms on the surface comprising the imprints so that it is replaced as quickly as possible by steam which will pass from the vapor phase to the liquid phase.
• the object of the invention avoids this phenomenon of wettability - the surfaces of the stainless steel tube do not undergo any treatment thermal to accentuate the evacuation.
• the redents consist of two elevations 2 and 3 having a height of less than 0.5 mm, preferably less than 0.2 mm, and a width occupying in a distributed manner, less than 50% of the periphery of said tube and preferably between 20 and 25% of the surface of the tube.
• the internal surface of the tube has a roughness of less than 0.2 ⁇ m, of the bright annealing type 2R, surface not disturbed by the making of the impressions.
• the tube is made from a strip of sheet metal with a thickness of between 1.3 and 1.5 mm made of ferritic or austenitic type stainless steel such as AISI 439, 304, 304L, 316L although some steels seem preferable. to others as will be demonstrated later.
• the making of the imprint does not cause, because of the dimensions thereof, no hardening zone of the base steel, no increase in the hardness of the steel.
• the impression practically does not modify the thickness of the wall of the tube, which avoids any risk of premature piercing of the tube if there is a risk of pitting corrosion.
• due to the small disturbance generated by the production of the imprint it is possible to modify the external appearance of a cylindrical tube, to increase the heat exchange capacity of said tube, without modifying excessive surface condition of the inner part of the tube.
• the internal part of the tube offers a surface limiting scaling and facilitating cleaning operations, the external part of said tube offering a practically smooth, cylindrical surface, and which ensures, due to the existence of fingerprints, a increase in heat exchange by draining and eliminating the condensation which forms continuously on the tube in its function of "hot" heat exchanger from steam.
• the tube can comprise the means of accumulation and flow of the fluid on its two external and internal surfaces so as to be able to be used, as desired, in the two functions of "hot" heat exchanger or "cold".
• tubes will be used comprising on their internal surface, the localized means of accumulation and flow of condensations.
• This primer depends on the surface properties of the tube such as micro-roughness, surface chemistry
• Two types of primers can be distinguished, one mineral of the MgO-CaC0 3 -S ⁇ 0 2 type for surfaces of the 2B, 2D type, pickled or not, the other mixed of type CaC0 3 plus organic matter, for type 2R and electro-polished surfaces, - a balance between the kinetics of scaling and the separation of layers
• the composition of the steel of the tube is an important parameter because the thermal and expansion coefficients will play on this balance - a phase where scaling prevails over the separation of the layers of tartar
• the tube according to the invention has the advantage of less scaling compared to the other tubes tested Reduction of the scaling is a factor of 2 to 3, which increases the evaporative flow by almost 25%
• the cleanability of the tubes depends on both the chemistry and the topography of the surface Indeed, according to the surface chemistry of the tube, the initiation of scale deposits differs and therefore, the ruptures caused by pressurized water , in the scale deposit, are more or less easy
• the roughness of the internal surface is an important factor for the elimination of the deposit
• the water consumption measurements clearly confirm the mechanisms governing surface cleanability, namely the surfaces of tubes made of AISI 439 stainless steel enriched in Si oxide and having an average roughness Ra of 0.2 ⁇ m will be scaled by a deposit of CaC0 3 associated with organic matter This deposit is more brittle and therefore more easily eliminated than a completely mineral deposit which preferably forms on the surfaces of a tube made, for example of AISI 304 steel enriched with iron or chromium oxide and having a lower average roughness Ra at 0.4
• the tube according to the invention ensures:

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Biochemistry (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1999
  • 1999-06-22 FR FR9907908A patent/FR2795337B1/fr not_active Expired - Fee Related
• 2000
  • 2000-06-21 WO PCT/FR2000/001702 patent/WO2000079187A1/fr not_active Application Discontinuation
  • 2000-06-21 BR BR0012526-1A patent/BR0012526A/pt not_active Application Discontinuation
  • 2000-06-21 EP EP00951620A patent/EP1188026A1/fr not_active Withdrawn
  • 2000-06-21 AU AU64500/00A patent/AU6450000A/en not_active Abandoned

Non-Patent Citations (1)

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