EP0882939A1 - Tube chauffant pour absorbeur et procede de fabrication correspondant - Google Patents

Tube chauffant pour absorbeur et procede de fabrication correspondant Download PDF

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Publication number
EP0882939A1
EP0882939A1 EP97947889A EP97947889A EP0882939A1 EP 0882939 A1 EP0882939 A1 EP 0882939A1 EP 97947889 A EP97947889 A EP 97947889A EP 97947889 A EP97947889 A EP 97947889A EP 0882939 A1 EP0882939 A1 EP 0882939A1
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EP
European Patent Office
Prior art keywords
tube
portions
heat exchanger
raised
circumferential
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.)
Granted
Application number
EP97947889A
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German (de)
English (en)
Other versions
EP0882939B1 (fr
EP0882939A4 (fr
Inventor
Shiguma Sanyo Electric Co. Ltd YAMAZAKI
Naoe Sumitomo Light Metal Industries Ltd SASAKI
Akio Sumitomo Light Metal Industries Ltd EGUCHI
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.)
Sanyo Electric Co Ltd
Sumitomo Light Metal Industries Ltd
Original Assignee
Sanyo Electric Co Ltd
Sumitomo Light Metal Industries Ltd
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Publication date
Application filed by Sanyo Electric Co Ltd, Sumitomo Light Metal Industries Ltd filed Critical Sanyo Electric Co Ltd
Publication of EP0882939A1 publication Critical patent/EP0882939A1/fr
Publication of EP0882939A4 publication Critical patent/EP0882939A4/fr
Application granted granted Critical
Publication of EP0882939B1 publication Critical patent/EP0882939B1/fr
Anticipated expiration legal-status Critical
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D15/00—Corrugating tubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
    • B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
    • B21C37/15—Making tubes of special shape; Making tube fittings
    • B21C37/20—Making helical or similar guides in or on tubes without removing material, e.g. by drawing same over mandrels, by pushing same through dies ; Making tubes with angled walls, ribbed tubes and tubes with decorated walls
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B37/00—Absorbers; Adsorbers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D3/00—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium flows in a continuous film, or trickles freely, over the conduits
    • F28D3/02—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium flows in a continuous film, or trickles freely, over the conduits with tubular conduits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F1/00—Tubular elements; Assemblies of tubular elements
    • F28F1/02—Tubular elements of cross-section which is non-circular
    • F28F1/06—Tubular elements of cross-section which is non-circular crimped or corrugated in cross-section
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F1/00—Tubular elements; Assemblies of tubular elements
    • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
    • F28F1/42—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being both outside and inside the tubular element
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F1/00—Tubular elements; Assemblies of tubular elements
    • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
    • F28F1/42—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being both outside and inside the tubular element
    • F28F1/422—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being both outside and inside the tubular element with outside means integral with the tubular element and inside means integral with the tubular element
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F1/00—Tubular elements; Assemblies of tubular elements
    • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
    • F28F1/42—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being both outside and inside the tubular element
    • F28F1/424—Means comprising outside portions integral with inside portions
    • F28F1/426—Means comprising outside portions integral with inside portions the outside portions and the inside portions forming parts of complementary shape, e.g. concave and convex
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2500/00—Problems to be solved
    • F25B2500/01—Geometry problems, e.g. for reducing size

Definitions

  • the present invention relates in general to a heat exchanger tube for an absorber which is horizontally installed in an absorber of an absorption refrigerator, an absorption heat pump and the like, more particularly, to such a heat exchanger tube for the absorber, which exhibits excellent heat exchanging efficiency, and whose mass per unit length is as small as that of a smooth surface tube, and a method of producing such a heat exchanger tube.
  • a smooth surface tube having smooth inner and outer surfaces and a circular shape in cross section.
  • a smooth surface tube cannot meet requirements for improving the performance of and downsizing the absorber, due to its relatively low heat exchangeability.
  • the smooth surface tube has another problem that the width of a layer of an absorbent flowing down in the circumferential direction of the tube decreases as the absorbent flows downwardly, due to the surface tension of the absorbent.
  • the smooth surface tube does not permit the absorbent to contact its outer circumferential surface over an area sufficient for assuring an effective heat exchanging action, and the outer circumferential surface of the tube tends to have a dry area portion, leading to a low vapor absorption efficiency of the absorbent, and consequently low heat exchangeability of the heat exchanger tube.
  • the proposed heat exchanger tubes are constructed such that a plurality of raised portions extending in the axial direction of the tube are formed on the outer circumferential surface of the tube, while recessed portions are formed between adjacent ones of the raised portions.
  • These raised and recessed portions are arranged in the circumferential direction of the tube so as to provide curved surfaces which are continuous in the circumferential direction.
  • the recessed portions have a radius of curvature which is larger than that of the raised portions.
  • Marangoni convections of the absorbent (which arise from a variation of its surface tension caused by uneven distribution of a surface active agent contained in the absorbent, on the surface of the absorbent layer) occur at the raised and recessed portions, respectively, and these Marangoni convections interfere with each other, whereby the absorbent on the outer circumferential surface of the tube has a large degree of turbulence in the longitudinal i.e., in the axial direction of the tube.
  • heat exchanging on the outer surface of the tube is effectively promoted, resulting in improved heat exchanging efficiency of the heat exchanger tube.
  • the heat exchanger tube constructed as described above exhibits improved heat exchangeability.
  • the heat exchanger tube suffers from an inherent problem that further improvement of the heat exchangeability of the tube is basically limited, due to its heating surface area which is substantially the same as that of the smooth surface tube.
  • JP-B-7-111287 a heat exchanger tube for an absorber, which has a plurality of grooves formed on the outer circumferential surface of the tube so as to extend in the longitudinal direction of the tube, and a multiplicity of fins formed between adjacent ones of the grooves at a relatively short interval.
  • the plurality of grooves having a relatively large depth cause rigorous agitation of the absorbent and flows of the absorbent in the axial direction, so that the absorbent is spread over the outer surface of the tube.
  • the multiplicity of fins formed between the adjacent grooves assure an increased heating surface area of the tube and an improved wettability of the surface of the tube with the absorbent, whereby the tube is given a considerably increased effective heating surface area.
  • the heat exchanger tube of the structure described above is prepared by forming the grooves extending in the axial direction of the tube in a known low-fin tube.
  • the heat exchangeability of the heat exchanger tube of this structure is only 1.4 times that of the smooth surface tube, although the heating surface area of the tube is at least several times that of the smooth surface tube.
  • the heat exchanger tube constructed as described above is made from the low-fin tube used as a base tube, so that a mass per unit length of the tube is at least about twice that of the the low-fin tube, leading to an inherent problem that the degree of increase of the cost of material of the heat exchanger tube is higher than that of improvement of the heat exchangeability of the tube.
  • the present invention was developed in view of the above described situation and it is therefore an object of the present invention to provide a heat exchanger tube for an absorber, which has a degree of improvement of heat exchangeability matching the degree of increase of a heating surface area of the tube and whose mass per unit length is as small as that of the smooth surface tube, and which does not increase the material cost.
  • a heat exchanger tube for an absorber having a structure wherein a plurality of raised portions each having an arcuately curved shape in a circumferential direction of the tube, are disposed on an outer circumferential surface so as to extend in an axial direction of the tube, and are arranged in the circumferential direction of the tube such that recessed portions are formed each between adjacent ones of the plurality of raised portions, and an inner circumferential surface of the tube is corrugated corresponding to the raised and recessed portions, and wherein an absorbent is dripped or spread on the outer circumferential surface of the tube, while a cooling fluid flows through an inside of the heat exchanger tube so as to cool the absorbent on the outer circumferential surface of the tube, characterized in that: a plurality of circumferential groove portions are formed in each of the raised portions at an regular interval in the axial direction of the tube, each of the circumferential groove portions extending in the circumferential direction of the tube and having a curved shape at a bottom portion thereof
  • the absorbent such as an aqueous solution of LiBr, which is attached to the outer surface of the tube, effectively flows and spreads in the axial direction of the tube along the recessed portions, while flowing down in the circumferential direction of the tube across the raised portions.
  • Each of the raised portions is formed in the arcuately curved shape.
  • the above described heat exchanger tube permits occurrence of the Marangoni convections of the absorbent in the raised and recessed portions formed in the outer surface of the tube, respectively, which Marangoni convections have different intensities proportional to the thickness values of layers of the absorbent formed on the respective raised and recessed portions.
  • the thickness values of the layers of the absorbent on the raised and recessed portions are remarkably different from each other, leading to a remarkable difference between the intensity of the Marangoni convection occurring on the raised portion and that occurring on the recessed portions.
  • a plurality of circumferential groove portions each extending in the circumferential direction of the tube are formed in the raised portions at a predetermined interval in the axial direction of the tube, and local portions of the raised portions which are interposed between the adjacent circumferential groove portions constitute mutually independent fins, respectively.
  • Each of the circumferential groove portions is formed such that the bottom portion of the circumferential groove portion has a curved shape in cross section in the axial and circumferential directions of the tube, and opposite ends of the circumferential groove portion in the circumferential direction have a width which gradually decreases such that the width is zero at the ends.
  • the unique configuration of the circumferential groove portions as described above restricts flows of the absorbent in the circumferential direction of the tube, while promoting flows of the absorbent in the axial direction of the tube. Accordingly, the absorbent is smoothly spread in the axial direction of the tube in comparison with the conventional tube having fins, so that the absorbent is effectively agitated by the Marangoni convections thereof and the collision thereof with the circumferential groove portions. Thus, heat exchanging operation of the heat exchanger tube can be further promoted.
  • the heat exchanger tube is arranged such that the circumferential groove portions are formed radially outwardly with respect to bottoms of the recessed portions, so as to prevent the circumferential groove portions from communicating with the bottoms of the recessed portions, and the opposite end portions of each of the circumferential groove portions terminate at corresponding side faces of the raised portions.
  • the flows of the absorbent in the axial direction along the recessed portions are more promoted than those in the circumferential direction along the circumferential groove portions between the adjacent fins, assuring the smooth flows of the absorbent in the axial direction of the tube.
  • the raised and recessed portions are formed by a drawing process, while the circumferential groove portions are formed by a rolling process, whereby the heat exchanger tube having a desired shape is advantageously obtained.
  • a heat exchanger tube for an absorber of the present invention there are formed in the bottoms of the recessed portions axial grooves extending in the axial direction of the tube, which are arranged in the circumferential direction of the tube such that surfaces of the axial grooves are non-smoothly contiguous with the bottoms in cross section in the circumferential direction.
  • the axial grooves are formed in the recessed portions, a difference between the thickness of the layers of the absorbent on the raised-portions and that on the recessed portions is further increased.
  • This arrangement is effective not only to induce the Marangoni convections of the absorbent when a suitable amount of absorbent is dripped on the tube, as in a normal operation, but also to give the layer of absorbent with a sufficient thickness on the tube when a small amount of the absorbent is dripped on the tube, as in an operation immediately after starting, so that turbulence of the absorbent is effectively induced due to the Marangoni convections.
  • the axial grooves have a depth which is too small to disturb flows of the absorbent into and from the axial grooves so that the absorbent can rapidly flow on the outer surface of the tube in the circumferential direction of the tube.
  • the circumferential surface of the tube has the concave portions and the convex portions which are arranged in the axial direction of the tube, in the local portions corresponding to the raised portions. This arrangement causes turbulence of the cooling fluid flowing through the inside of the tube, resulting in effective improvement of the overall heat transfer coefficient of the tube.
  • the heat exchanger tube for the absorber according to the present invention as described above may be advantageously produced by a method of producing a heat exchanger tube for an absorber wherein an absorbent is dripped or spread on an outer circumferential surface of the heat exchanger tube, while a cooling fluid flows through an inside of the heat exchanger tube so as to cool the absorbent on the outer circumferential surface of the heat exchanger tube, the method being characterized by comprising: (a) a first step of drawing a cylindrical blank tube into a corrugated tube which is constructed such that a plurality of raised portions each having an arcuately curved shape in a circumferential direction of the tube, are disposed on the outer circumferential surface so as to extend in an axial direction of the tube, and are arranged in the circumferential direction of the tube such that recessed portions are formed between adjacent ones of the plurality of raised portions, and an inner circumferential surfaces of the tube is corrugated corresponding to the raised and recessed portions; and (b) a second step of
  • the cylindrical blank tube is subjected to the drawing process so as to form the axial grooves in the tube (so as to form the corrugated tube) in the first step, and then is subjected to the rolling process so as to form fins on the tube in the second step.
  • the heat exchanger tube having a desired shape can be obtained without suffering from appearance of burrs between the adjacent fins formed in each raised portion.
  • Each of fins produced as described above has a height which gradually decreases toward the opposite ends in the circumferential direction of the tube, while each of the circumferential groove portions formed by the rolling process has a width which gradually decreases toward the opposite ends in the circumferential directions of the tube such that the width is zero at the ends.
  • each of the raised portions extending in the axial direction of the tube is formed on the outer surface of the tube so as to have the arcuately curved shape in the circumferential direction of the tube, and a plurality of the raised portions are arranged in the circumferential direction of the tube.
  • the absorbent dripped on the outer circumferential surface of the tube can easily flow in the circumferential and axial directions of the tube.
  • the numbers of the raised portions arranged in the circumferential direction of the tube is not particularly limited, but may be suitably selected in view of the diameter of the heat exchanger tube or the like. If an excessively small number of the raised portions are arranged on the tube, the tube cannot exhibit sufficient heat exchangeability.
  • each of the raised portion preferably has a radius of curvature of about 0.5-5.0mm.
  • the recessed portions formed between the adjacent raised portions may be formed according to the shape of the raised portions.
  • the recessed portions are constituted, by respective portions of the tube interposed between and contiguous with the corresponding adjacent raised portions.
  • the wall thickness of the tube in the recessed portions is substantially equal to that in the raised portions (so that the concave and convex portions are formed in the inner surface of the tube, which are correspond to the raised and recessed portions, respectively).
  • the recessed portions generally have a thickness of about 0.3-1.2mm, since the recessed portions having an excessively large depth may deteriorate the ease of manufacture of the tube, and reduce the cross sectional area of the fluid passage of the heat exchanger tube, resulting in an increase of the pressure loss within the tube.
  • each of the recessed portions is interpreted to mean a length of a normal line extending from a bottom surface of the recessed portion (a bottom surface of the axial groove if provided) to a straight line which is tangent to the apexes of the adjacent raised portions between which the recessed portion is interposed.
  • the heat exchanger tube for the absorber according to the present invention is also characterized in that the plurality of circumferential groove portions each extending in the circumferential direction of the tube are formed in each of the raised portions at a predetermined interval, in the axial direction of the tube, so that the local portions of the raised portion which are interposed between the adjacent circumferential groove portions constitute independent fins, respectively. That is, the fins have a shape in traverse cross section of the tube, which is similar to that of the raised portions, namely, an arcuately curved shape, since the fins are constituted by the corresponding portions of the raised portion in which no circumferential groove portions are formed. On the other hand, the shape of the fin in longitudinal cross section of the tube is determined by that of the adjacent circumferential groove portions.
  • the circumferential groove portions which determine the shape of the fins in the longitudinal cross section of the tube are formed such that a bottom portion of each of the circumferential groove portions has a curved shape in cross section in the axial and circumferential direction of the tube, and opposite end portions of each of the circumferential groove portions in the circumferential direction of the tube have a width which gradually decreases toward the ends at which the width is zero.
  • the circumferential groove portions are preferably formed to have a curved shape such as a U-shape and an arcuate shape, while meeting the dimensional requirement such as the height of fins, the interval between the adjacent fins and the interval between the opposite ends of the adjacent fins.
  • the fins formed on the raised portions have an excessively small height, an area of contact of heating surface area of the tube with the absorbent is not expected to be sufficiently large.
  • the fins may divide the layer of the absorbent formed on the outer surface of the tube.
  • the fins have a height of about 0.3-1.5mm. It is especially desired that the circumferential groove portions are formed such that the depth of the circumferential groove portions do not reach the bottoms of the recessed portions, in order to promote expansion of the absorbent especially in the axial direction of the tube.
  • each of the fins is interpreted to mean a length of a normal line extending from a bottom surface of the circumferential groove portion interposed between the adjacent fins, to a straight line tangent to the apexes of the adjacent fins.
  • the adjacent fins have an interval of about 0.9-4.0mm. It is not preferable to form the fins with an excessively small interval, since the absorbent hardly flows into the circumferential groove portions disposed between the adjacent fins and tends to stay in the circumferential groove portions if once entered, even if the absorbent has a relatively low concentration. It is also not preferable to form the fins with an excessively large interval, since the heating surface area of the tube is not increased as needed.
  • the interval between the adjacent fins is interpreted to mean a distance in the axial direction of the tube between a selected portion of one of the adjacent fins and the corresponding portion of the other of the adjacent fins.
  • the interval between the top ends of the adjacent fins is preferably about 0.45-3.0mm, so as to facilitate entry into the circumferential groove portions of different absorbents whose concentrations vary in a wide range, and so as to prevent unnecessarily long stay of the absorbent in the circumferential groove portions.
  • This interval between the top ends of the adjacent fins means a length of a straight line between the top ends of the opposite side faces of the adjacent fins.
  • the heat exchanger tube for the absorber of the present invention is preferably characterized in that the local portions of the inner surface of the tube which correspond to the raised portions have a shape which is determined by the shape of the circumferential groove portions in cross section, so that the shape is reverse with respect to the outer surface of the tube in the raised portion, as seen in a cross section in the axial direction of the tube (in the longitudinal cross section of the tube).
  • the circumferential groove portions formed in the outer surface of the tube provide convex or protruding portions on the inner surface of the tube, while the fins interposed between the adjacent circumferential groove portions in the outer surface of the tube constitute concave portions in the inner surface of the tube.
  • each fin formed on the outer surface of the tube takes the form of a bent plate, so that the tube has substantially no increase in the wall thickness at the fin portions, assuring the heat exchanger tube having a mass per unit length which is substantially equal to that of the base tube such as the grooved tube (corrugated tube) and the smooth surface tube.
  • the concave and convex portions formed on the inner surface of the tube permit turbulence of the cooling fluid flowing through the inside of the tube, resulting in an improved overall heat transfer coefficient of the tube.
  • the heat exchanger tube of the present invention preferably has axial grooves formed in the bottoms of the recessed portions, so as to promote the turbulence of the absorbent. These axial grooves are formed in the bottoms of the recessed portions such that the surface of each of the axial grooves is non-smoothly contiguous with the corresponding raised and recessed portions in the circumferential direction of the tube.
  • the outer curved surface of the axial groove is connected to the outer curved surfaces of the corresponding raised and recessed portions in the circumferential direction of the tube, such that the curved surface of the axial groove portion intersect the curved surfaces of the raised and the recessed portions, at points at which there are no common lines tangent to those curbed lines. In this intersections, there is no common tangent.
  • the shape of the axial groove in the traverse cross section is not particularly limited, and various kinds of shapes such as a U-shape, a V-shape, a rectangular shape and a trapezoidal shape may be employed.
  • the axial groove has a depth of about 0.01-0.15mm, so as to prevent an unnecessary stay of the absorbent therein.
  • the heat exchanger tube as described above may be formed of various kinds of materials as well known in the art. For obtaining a heat exchanger tube having excellent heat exchangeability, it is preferable to employ a material exhibiting excellent thermal conductivity, such as copper and alloyed copper. Generally, the formed heat exchanger tube has a diameter of about 6.35-25.4mm.
  • the heat exchanger tube for the absorber according to the present invention is basically produced as follows: Initially, an appropriate corrugated tube used in the present invention is obtained by a known method as disclosed in JP-B-2-89270, JP-A-2-176378 and JP-A-7-24522. Then, the obtained corrugated tube is subjected to the rolling process so as to form the circumferential groove portions only in the raised portions and provide fins constituted by the local portions of the raised portions which are interposed between adjacent ones of the circumferential groove portions, to thereby obtain the desired heat exchanger tube for the absorber.
  • the corrugated tube is obtained by subjecting the cylindrical blank tube to a cold drawing process.
  • the desired corrugated tube may otherwise be obtained by hot extrusion of a copper pipe of a suitable composition.
  • the surfaces of the axial grooves formed in the respective recessed portions are non-smoothly contiguous with the corresponding raised and recessed portions.
  • the heat exchanger tube having such a structure can be easily produced with high stability in shape, by using a technique usually practiced for processing a tube having different diameters in the method of producing the tube as described above.
  • the raised and recessed portions formed on the outer surface of the tube need not extend straightly in the axial direction of the tube, but may extend helically in the axial direction of the tube.
  • the helix angle of the raised and recessed portions is preferably not greater than 15°, since an excessively large helix angle causes reduction of the amount of the absorbent which flows in the circumferential direction across the raised portions, leading to deterioration of heat exchangeability of the tube.
  • the heat exchanger tube having helical raised and recessed portions can be easily produced as follows: Initially, a blank tube is subjected to the drawing process using dies having helical raised and recessed portions, or by drawing the blank tube while rotating the blank tube and the dies relative to each other, so as to obtain a processed tube having helically formed raised and recessed portions. Then, the obtained tube is subjected to the rolling process to form appropriate circumferential groove portions.
  • Fig. 1 is a perspective view showing one embodiment of a heat exchanger tube for an absorber according to the present invention.
  • Fig. 2 is a traverse cross sectional view of the heat exchanger tube shown in Fig. 1.
  • Fig. 3 is an enlarged view in longitudinal cross section of a raised portion of the heat exchanger tube shown in Fig. 1.
  • Fig. 4 is a cross sectional view in cross section perpendicular to an axis of the heat exchanger tube, showing a rolling process for producing the heat exchanger tube shown in Fig. 1.
  • Fig. 5 is a view for explaining the rolling process performed on one of the raised portions, using rolling disks.
  • Fig. 6 is a fragmentary enlarged view showing the details of a shape of the raised portion in traverse cross section before and after the rolling process, and the details of a shape of fins after the rolling process.
  • Figs 7 (a)-(c) are views showing configurations of circumferential groove portions and fins formed by the rolling process at the raised portion, wherein Fig 7(a), Fig. 7(b) and Fig. 7(c) are perspective, top plan, and side views of the raised portion, respectively.
  • Fig. 8 is a view showing one example of arrangement of a plurality of heat exchanger tubes each shown in Fig. 1, which are disposed in an absorber.
  • Fig. 9 is a traverse cross sectional view of the heat exchanger tube disposed in the upper portion of the absorber shown in Fig. 8.
  • Fig. 10 is an enlarged view in longitudinal cross section of the raised portion of the heat exchanger tube for the absorber shown in Fig. 9.
  • Fig. 11 is an enlarged view in longitudinal cross section similar to that of Fig. 3, of the raised portions of the heat exchanger tube, showing another example of configuration of fins of the heat exchanger tube for the absorber of the present invention.
  • Fig. 12 is an enlarged view in longitudinal cross section similar to that of Fig. 3, of one of the raised portions of the heat exchanger tube, showing yet another example of configuration of fins of the heat exchanger tube for the absorber of the present invention.
  • the heat exchanger tube 2 is prepared from a phosphor-deoxidized copper tube (outside diameter: 16mm ⁇ , wall thickness: 0.6mm) made of a material C1220 (JIS H3300), which is provided as a cylindrical blank tube.
  • the blank tube is subjected to a cold drawing operation with a die, so as to form a corrugated tube having raised portions and recessed portions which extend in the axial direction of the tube.
  • the corrugated tube is subjected to a rolling process using rolling disks as used in a rolling process usually employed for producing a finned tube, such that circumferential groove portions each extending in the circumferential direction of the tube are formed in the raised portions at a predetermined interval in the axial direction of the tube.
  • the heat exchanger tube 2 is obtained.
  • the raised portions 4 each having an arcuately curved shape and the recessed portions 6 formed between adjacent ones of the raised portions 4 are arranged alternately in the circumferential direction of the tube.
  • These raised and recessed portions 4, 6 extend straight in the axial direction of the tube.
  • the depth D1 of each of the recessed portions 6 is 0.5mm.
  • there are formed circumferential groove portions 8 each extending in the circumferential direction of the tube are arranged at a predetermined interval in the axial direction of the tube.
  • Local portions of the raised portions 4 interposed between the adjacent ones of the circumferential groove portions 8 constitute mutually independent fins 10, respectively.
  • respective axial grooves 12 having a depth D2 of 0.03mm such that the surfaces of the axial grooves 12 are non-smoothly contiguous with the raised portions 4 and the recessed portions 6.
  • the axial grooves 12 are formed not in the raised portions 4 but in the recessed portions 6. This arrangement further increases a difference between the thickness of a layer of an absorbent on the the raised portions 4 and that on the recessed portions 6, and accordingly increases a difference between intensities of the Marangoni convection occurring in the raised portions 4 and that in the recessed portions.
  • the circumferential groove portions 8 are formed in the raised portion 4 so as to extend at right angles to the raised portions, while the local portions of the raised portion 4 which are disposed between the adjacent ones of the circumferential groove portions 8, constitute fins 10.
  • Each of the fins 10 has a generally curved shape in longitudinal cross section, while having a height F of 0.8mm.
  • the fins 10 are arranged at an interval P of 2.0mm while having a distance W of 0.9mm between the end faces of the adjacent fins 10.
  • the fins 10 having the generally curved shape is less likely to prevent flows of the absorbent in the axial direction of the tube, and facilitate formation of the layers of the absorbent and flows of the absorbent in the circumferential direction of the tube.
  • the heat exchanger tube 2 has an inner circumferential surface which includes local portions corresponding to raised portions 4.
  • protrusions 14 and concave portions 16 which are arranged alternately in the axial direction of the tube. Namely, these protrusions 14 are formed by protrusion of local portions of the inner circumferential surface of the tube which correspond to the circumferential groove portions 8, into the inside of the tube, while the concave portions 16 are formed by local portions of the inner circumferential surface of the tube which correspond to the fins 10 disposed between the adjacent circumferential groove portions 8.
  • protrusions 14 and concave portions 16 constitute a corrugated structure of the inner circumferential surface of the tube, which structure promotes turbulent flows of a cooling fluid through the interior of the tube, resulting in improved heat exchangeability of the heat exchange tube 2. Moreover, an increase in the wall thickness of the heat exchanger tube 2 at the fin portions is effectively restrained, so that the unit weight of the heat exchanger tube 2 of the present invention can be made as small as a smooth surface tube.
  • the heat exchanger tube 2 of this construction can be easily produced from the appropriate cylindrical blank tube, as described above, by successively subjecting the blank tube to a drawing process and a rolling process, which are known in the art. More specifically described, the blank tube is initially subjected to an ordinary cold drawing process to produce a corrugated tube 20 having the plurality of raised portions 4 which are formed on the outer circumferential surface so as to extend in the axial direction of the tube and each of which has an arcuately curbed shape as seen in the circumferential direction of the tube.
  • the raised portions 4 are arranged in the circumferential direction of the tube such that the recessed portions 6 are formed between the adjacent ones of the raised portions 4, which raised and recessed portions 4, 6 have substantially the same wall thickness.
  • the thus obtained corrugated tube 20 is subjected to the rolling process using rolling disks 22 as shown in Fig. 4.
  • three sets of rolling disks 22 are disposed around the corrugated tube 20 that is to be subjected to the rolling process, such that these sets of the rolling disks 22 are equally spaced from each other at an angular interval of 120°.
  • Each of these sets of the rolling disks consists of a plurality of rolling disks 22 which are disposed coaxially with each other and rotated together as a unit. With the sets of rolling disks being rotated, each rolling disk 22 is pressed onto the raised portions 4 of the corrugated tube 20, so that the raised portions 4 of the corrugated tube 20 are subjected to the rolling process.
  • a manner of forming the circumferential groove portions 8 in one of the raised portions 4 by the rolling process that is, a manner of forming the fins 10.
  • the rolling process proceeds beginning with the stage of Fig. 5 (a) and ending with the stage of Fig. 5 (d).
  • the circumferential groove portions 8 are not formed by one rolling disk 22, but are progressively formed by the individual rolling disks 22 which belong to the respective sets of rolling disks 22, such that the rolling disks 22 of the different sets presses each raised portion 4, so that the fins 10 are are also formed between the adjacent rolling disks 22 such that the height of each fin 10 gradually increases in the radially outward direction of the tube as the rolling process progresses, as indicated in the right views.
  • each of the circumferential groove portions 8 formed by the rolling process has a curved shape, more specifically, an arcuately curved shape at its bottom portion, in cross section in both of the axial and circumferential directions of the tube.
  • the opposite end portions of the circumferential groove portion 8 as seen in the circumferential direction of the tube have a width which gradually decreases to zero, as is apparent from Fig.
  • each circumferential groove portion 8 interposed between the adjacent fins 10 has the opposite end portions as seen in the circumferential direction of the tube. These portions have a width which decreases gradually as the end portions extend toward their ends, in other wards, toward the corresponding recessed portions 6, such that the width is zero at the ends of the circumferential groove portion.
  • This arrangement restricts flows of the absorbent in the circumferential direction, while permitting easier flows of the absorbent in the axial direction, than in the conventional finned heat exchanger tube.
  • the heat exchange effect of the heat exchanger tube 2 is further improved due to the turbulence of the absorbent caused by the Marangoni convection of the absorbent, and the collision of the layers of the absorbent with the circumferential groove portions 8.
  • the circumferential groove portions 8 constructed as described above are formed radially outwardly with respect to the bottoms of the recessed portions 6, so as to prevent the circumferential groove portions 8 from communicating with the corresponding recessed portions 6, and that the opposite ends of the circumferential groove portions 8 in the circumferential direction terminate at the corresponding side faces of the raised portions 4.
  • the flows of the absorbent along the recessed portions 6 in the axial direction of the tube are further effectively promoted.
  • a plurality of heat exchanger tubes 2 each constructed as described above are generally disposed in an absorber 30 of an absorption refrigerator, such that the heat exchanger tubes 2 are arranged in the vertical direction, while each heat exchanger tube has a horizontal attitude. Cooling water as a coolant fluid is caused to flow through the inside of the heat exchanger tubes 2, so that the absorbent on the outer surfaces of the heat exchanger tubes 2 is effectively cooled. More specifically described, the absorbent 36, such as an aqueous solution of lithium bromide including a surface active agent, is dripped or dispersed on the heat exchanger tube 2 from spreader nozzles 34 of a spreader 32 which are disposed above the heat exchanger tube 2.
  • the absorbent 36 dispersed on the heat exchanger tubes 2 has a relatively high concentration so that the absorbent flows down smoothly on the outer circumferential surfaces of the heat exchanger tubes 2, while absorbing a vapor which exists inside the absorber 30.
  • the heat generated upon absorption of the vapor is transferred from the absorbent 36 to the cooling water flowing through the inside of the heat exchanger tube 2, so that the absorbent 36 is effectively cooled.
  • the absorbent 36 which is dripped from the spreader nozzles 34 of the spreader 32 disposed above the heat exchanger tube 2 (not shown), initially flows down on the outer circumferential surface of the heat exchanger tube 2 in the circumferential direction of the tube 2 via the raised portions 4 and the recessed portions 6 alternately In the raised and recessed portions 4, 6, Marangoni convections of the absorbent 36 occur, depending upon the thickness values of the layers of the absorbent 36 on the raised and recessed portions 4 and 6. The thickness of the layer of the absorbent on each of the raised portions 4 is considerably smaller than that on each of the recessed portions 6.
  • the Marangoni convection of the absorbent 36 occurring in the raised portion 4 has a relatively low intensity
  • the Marangoni convection of the absorbent 36 occurring in the recessed portion 6 has a relatively high intensity, in the axial direction of the heat exchanger tube 2.
  • the absorbent 36 can enter into the circumferential groove portions 8 interposed between the adjacent fins 10 as also shown in Fig. 10, resulting in an effective increase of the area of contact of the heat exchanger tube 2 with the absorbent 36.
  • the heat exchanger tubes 2 for the absorber constructed according to the present invention exhibits an improved heat exchangeability.
  • the axial grooves 12 are formed in the bottoms of the recessed portions 6 so that the layer of the absorbent 36 on each of the recessed portions 6 has, a relatively large thickness. Accordingly, the Marangoni convection of the absorbent 36 occurs to a great extent when a suitable amount of absorbent 36 is dripped onto the heat exchanger tube 2, as in a normal operation of the absorption system.
  • the absorbent 36 collects in the axial grooves 12 so as to provide the layer of the absorbent 36 having a desired thickness on the recessed portions 6, so that the intensity of the Marangoni convections occurring on the recessed portions 6 is effectively increased, thereby assuring improved heat exchangeability of the heat exchanger tube 2.
  • the axial grooves 12 are configured to have a relatively small depth of 0.03mm, which depth is too small to disturb flows of the absorbent 36 across the recessed portions 6, so that the absorbent 36 dripped on the outer surface of the heat exchanger tube 2 is smoothly moved in the circumferential direction of the tube.
  • the heat exchanger tube 2 constructed as described above can exhibits improved heat exchanging efficiency, as compared with the conventionally used heat exchanger tube, by simply forming the axial grooves 12 in the recessed portions 6 so as to increase the amount of the absorbent 36 on the outer circumferential surface.
  • a heat exchanger tube for an absorber is not limited to the details of the illustrated construction as described above.
  • the fins 10 may be configured to have a shape in the longitudinal cross section as illustrated in Fig. 11 or 12.
  • each of the fins 10 has a flat top surface as seen in the longitudinal cross section.
  • each of the fins 10 has a top having an extremely small width as seen in the longitudinal cross section.
  • the measurement reveals that the heat exchanger tube 2 according to the present invention exhibited an overall heat transfer coefficient which is about 1.2 times that of the corrugated tube 20, which is a base of the heat exchanger tube 2, and about 1.5 times that of the smooth surface tube.
  • the actual heating surface area of the heat exchanger tube 2 was about 1.2 times that of the corrugated tube or the smooth tube. It was confirmed that the degree of increase of the heat exchangeability of the heat exchanger tube 2 was the degree of increase of the heating surface area.
  • the circumferential groove portions disposed between the adjacent fins are formed to have a curbed shape, so that the absorbent effectively flows into the circumferential groove portions irrespective of the concentration of the absorbent, resulting in prevention of unnecessary stay of the absorbent in the circumferential groove portions, whereby the formed layer of the absorbent is given a suitable thickness. Accordingly, the surface area of contact of the heat exchanger tube with the absorbent is advantageously increased, whereby the heat exchangeability of the heat exchanger tube is effectively improved.
  • the circumferential groove portions are configured such that the opposite end portions of each of the circumferential groove portions in the circumferential direction have a gradually decreasing width, so that the width is zero at the opposite ends.
  • the circumferential groove portions hardly prevent the flows of the absorbent in the axial direction of the tube and the Marangoni convections of the absorbent, leading to intensive turbulence of the absorbent, whereby the heat exchangeability of the heat exchanger tube is improved.
  • On each raised portion of the tube there is formed a layer of the absorbent with openings, which layer is continuous with the layers of the absorbant formed on the recessed portions, permitting flows of the absorbent in the axial direction and the Marangoni convection of the absorbent. Accordingly, the Marangoni convections of the absorbent occurring in the respective raised and recessed portions interfere with each other so as to cause relatively strong turbulence of the absorbent, whereby the heat exchangeability of the heat exchanger tube is further improved.
  • the present invention relates to a heat exchanger tube for an absorber, which is horizontally disposed in the absorber for an absorption refrigerator, an absorption heat pump and the like, and a method of producing the heat exchanger tube.
  • the present invention provides the heat exchanger tube which assures an excellent heat exchanging efficiency and whose mass per unit length is as small as that of the the smooth surface tube, and the method according to which the heat exchanger tube can be advantageously produced.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Geometry (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
  • Rigid Pipes And Flexible Pipes (AREA)
EP97947889A 1996-12-13 1997-12-10 Tube chauffant pour absorbeur et procede de fabrication correspondant Expired - Lifetime EP0882939B1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP333319/96 1996-12-13
JP33331996 1996-12-13
JP33331996A JP3769338B2 (ja) 1996-12-13 1996-12-13 吸収器用伝熱管及びその製造方法
PCT/JP1997/004554 WO1998026239A1 (fr) 1996-12-13 1997-12-10 Tube chauffant pour absorbeur et procede de fabrication correspondant

Publications (3)

Publication Number Publication Date
EP0882939A1 true EP0882939A1 (fr) 1998-12-09
EP0882939A4 EP0882939A4 (fr) 2000-01-19
EP0882939B1 EP0882939B1 (fr) 2003-07-09

Family

ID=18264788

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97947889A Expired - Lifetime EP0882939B1 (fr) 1996-12-13 1997-12-10 Tube chauffant pour absorbeur et procede de fabrication correspondant

Country Status (5)

Country Link
EP (1) EP0882939B1 (fr)
JP (1) JP3769338B2 (fr)
KR (1) KR100472526B1 (fr)
CN (1) CN1128331C (fr)
WO (1) WO1998026239A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6488079B2 (en) 2000-12-15 2002-12-03 Packless Metal Hose, Inc. Corrugated heat exchanger element having grooved inner and outer surfaces
US6760972B2 (en) 2000-09-21 2004-07-13 Packless Metal Hose, Inc. Apparatus and methods for forming internally and externally textured tubing
WO2009103281A3 (fr) * 2008-02-21 2009-11-19 Lutz Pasemann Réchauffeur d'un moteur stirling
US7679034B2 (en) 2005-04-20 2010-03-16 Ngk Insulators, Ltd. Power-supplying member and heating apparatus using the same

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US9314802B2 (en) 2010-09-13 2016-04-19 Kawasaki Jukogyo Kabushiki Kaisha Spraying tube device and heat exchanger using the same
CN103175429B (zh) * 2013-04-18 2016-02-03 南京工业大学 多向波纹内翅片管
CN104833257A (zh) * 2014-02-10 2015-08-12 Lg电子株式会社 传热管以及具有该传热管的制冷机
CN104296579A (zh) * 2014-07-29 2015-01-21 无锡塔尔基热交换器科技有限公司 一种换热管及其制造方法和装有该换热管的换热器
KR101708669B1 (ko) * 2014-12-04 2017-03-08 엘지전자 주식회사 스테인리스강 코루게이트 전열관과 그를 갖는 흡수식 냉동기 및 그 제조 방법
CN106075940B (zh) * 2016-08-24 2018-07-24 佛山科学技术学院 中央循环管式蒸发器
KR20180138070A (ko) * 2017-06-20 2018-12-28 엘지전자 주식회사 흡수식 칠러
CN109405354A (zh) * 2018-11-19 2019-03-01 珠海格力电器股份有限公司 降膜式换热器及空调机组
CN112872091B (zh) * 2020-12-31 2023-01-31 浙江海亮股份有限公司 四齿异型管拉伸工艺

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6760972B2 (en) 2000-09-21 2004-07-13 Packless Metal Hose, Inc. Apparatus and methods for forming internally and externally textured tubing
US6968719B2 (en) 2000-09-21 2005-11-29 Packless Metal Hose, Inc. Apparatus and methods for forming internally and externally textured tubing
US6488079B2 (en) 2000-12-15 2002-12-03 Packless Metal Hose, Inc. Corrugated heat exchanger element having grooved inner and outer surfaces
WO2002048631A3 (fr) * 2000-12-15 2002-12-19 Packless Metal Hose Inc Element echangeur thermique cannele, a rainures sur les surfaces interieure et exterieure
US7679034B2 (en) 2005-04-20 2010-03-16 Ngk Insulators, Ltd. Power-supplying member and heating apparatus using the same
WO2009103281A3 (fr) * 2008-02-21 2009-11-19 Lutz Pasemann Réchauffeur d'un moteur stirling
DE112009000938B4 (de) * 2008-02-21 2020-09-03 Lutz Pasemann Erhitzer eines Stirlingmotors

Also Published As

Publication number Publication date
WO1998026239A1 (fr) 1998-06-18
JPH10176893A (ja) 1998-06-30
CN1211312A (zh) 1999-03-17
JP3769338B2 (ja) 2006-04-26
EP0882939B1 (fr) 2003-07-09
CN1128331C (zh) 2003-11-19
KR100472526B1 (ko) 2005-07-07
EP0882939A4 (fr) 2000-01-19
KR19990082278A (ko) 1999-11-25

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