Patent Publication Number: US-3880231-A

Title: Heat-exchanger and method for its utilization

Description:
United States Patent Gauthier HEAT-EXCHANGER AND METHOD FOR ITS UTILIZATION [73] Assignee:  
 Inventor:  
 Pierre Gauthier. Antony. France {22] Filed: Sept. 26. 1972 [21] Appl. No.1 292,457  
 [30] Foreign Application Priority Data Oct. I. 1971 France 71.35393 [52] US. Cl. 165/166: 62/11; 165/110 [51] Int. Cl. F28f 3/00 [58] Field of Search 165/166. 167; 62/13 [561 References Cited UNITED STATES PATENTS 2.703.700 3/1955 Simpclaar 165/113 3.282.334 11/1966 Stahlhcbcr.... 165/166 3.310.105 3/1967 Butt.... 165/166 3.380.517 4/1968 Butt 165/166 3.469171 9/1969 lchihara ct 111.... 62/13 3.559.722 2/1971 Schauls ct al..... 165/166 X 3.669.186 6/1972 Schauls 165/166 Primal ExaminerAlbert W. Davis. Jr. Assistant E.\&#39;umincrSheldon Richter Attorney. Agent, or FirmYoung &amp; Thompson [57] ABSTRACT The present invention relates to an improved heat exchanger and an improved method of heat exchange using a plate-type heat-exchanger permitting the exchange of heat between a first fluid in liquid form and a second fluid in gaseous form. joined together and circulating in certain passages of the exchanger. and a third fluid circulating in other adjacent passages of the exchanger. The characteristic improvements of said exchanger include the provision of a third inlet towards the first passage. defined by a first closure means adjacent to a second inlet and to one extremity of the first passage so as to introduce into said first passage the fluid to be received into said second passage; a third distribution means is arranged in the first passage to distribute the fluid to be received in said second passage. from the third inlet towards the interior of said first passage, substantially over the whole dimension of said passage perpendicular to the longitudinal direction. the transfer zone also extending along the longitudinal direction and comprising a plurality of perforations separated from each other. The transfer zone between passages may comprise a plurality of longitudinally elongated slots or a plurality of slots perpendicular to the longitudinal direction or a plurality of orifices distributed in the longitudinal direction of the second plate.  
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 HEAT-EXCHANGER AND METHOD FOR ITS UTILIZATION The present invention relates to a heat-exchangerc. and more particularly to a heat-exchanger of the plate type, permitting the exchange heat between a first fluid in liquid form and a second fluid in gaseous form, combined together and circulating in certain passages of the exchanger, and a third fluid circulating in other adjacent passages of the exchanger. It is also concerned with a method of use of the said exchanger.  
  in numerous processes such as those employed in the liquefaction of natrual gas, it is frequently necessary to exchange heat between a first fluid in liquid form and a second fluid in the gaseous form, constituting respectively the liquid and gaseous phases of a single fluid in the two-phase form, and a third fluid. If a plate exchanger is employed to effect such an exchange. it is essential, after having separated the liquid and gaseous phases of th two-phase fluid, to distribute correctly the first and second fluids as between the various passages and inside a single passage reserved for the two-phase fluid, in order to obtain a fluid in the two-phase form which has substantially the same characteristics from one passage to another and along the whole length of the said passages. It is in fact under this sole condition that it is possible on the one hand to obtain correct operation of the exchanger, and on the other hand finally to attain the performances contemplated during the design of the exchanger.  
  There has recently been described a method of heat exchange and a plate heat-exchanger which makes it possible to explain a homogenous distribution of the first and second fluids in the passages of the exchanger which are reserved for them. See US. Pat. No. 3,559,722.  
  According to this method which utilizes a plate-type heat-exchanger comprising a plurality of substantially flat passages, te heat is thus exchanged between a first fluid in the liquid form and a second fluid in the gaseous form, combined together and circulating in certain passages of the exchanger in a longitudinal direction, and a third fluid circulating in other adjacent passages of the exchanger.  
  For this purpose, one of the first and second fluids is introduced into a first passage of the said exchanger, the fluid introduced into the first passage is distributed substantially in a uniform manner in the interior and along the whole length of the said passage, perpendicular to the longitudinal direction; at least one first portion of member of the said first and second fluids is introduced into at least one second passage of the said exchanger, adjacent to the first passage, the first portion introduced into the second passage is distributed in a substantially uniform manner through the interior and along the whole extent of the said passage perpendicular to the longitudinal direction; at least one portion of the fluid introduced into the first passage and the first portion introduced into the second passage are combined in the said second passage along the whole extent of the first and second passages, perpendicular to te longitudinal direction, so as to constitute at least one part of a substantially homogeneous two-phase fluid distributed in a substantially uniform manner in the second passage along the whole of its extent; the said portion of the two-phase fluid is caused to circulate in thermal exchange with the third fluid.  
  The plate heat-exchanger described, which enables this method to be carried into effect, thus compries a plurality of metal plates having a substantially similar contour, parallel to and spaced apart from each other; a first closure means coupling the said plates to each other along the edge of each plate. the said closure means and the said plates delimiting a plurality of passages, at least three consecutive plates defining respectively a first reception passage for a first fluid in the liquid form and a second fluid in gaseous form, comprised between a first plate and a second plate, and at least one second reception passage for the other of the first and second fluids and for circulating the first and second fluids combined together in a longitudinal direction comprised between the second plate and a third plate; the second plate comprising a transfer zone for at least a portion of the fluid which is to be received in the first passage towards the second passage, the said zone extending along at least all the length of the first and second passages perpendicualr to the longitudinal direction; the first closure means defining respectively a first inlet towards the first passage in order to introduce the fluid which is to be received by the first passage, and at least one second inlet towards the second passage in the vicinity of one extremity of the said passage, in order to introduce the fluid to be received by the said passage, the transfer means being arranged between the first inlet and the second inlet; a first distri bution means arranged in the first passage in order to distribute the fluid to be received by the said passage from the first inlet towards the interior of the first passage substantially along the whole extent of the said passage perpendicular to the longitudinal direction; a second distribution means disposed in the second passage so as to distribute the fluid which is to be received by the said passage from the second inlet towards the interior of the second passage substantially along the whole extent of the said passage perpendicular to the longitudinal direction; the first closure means defining at least one first outlet from the second passage, in the vicinity of the other extremity of the said passage, in order to evacuate the combined first and second fluids; means defining a third passage for a third fluid in heatexchange relation with at least the second passage.  
  In the case of the plate heat-exchanger having the structure previously defined, the only transfer zone described is constituted by a single horizontal slot extending at least along the whole extent of the first and second passages, perpendicular to the longitudinal direction of circulation of the combined first and second fluids.  
  ln all &#39;the present description, the plates of the exchanger which comprise a transfer zone, such as the second plates defined above, will also be referred to by the term partition&#34; in order to differentiate them from the other plates which do not comprise this zone.  
  While the above method and exchanger make it possible to obtain a homogenous two-phase fluid distributed in a uniform manner between the passages which are reserved for it and over the whole width of these latter, it has been found that the flexibility of operation of an exchanger of this kind remains defective.  
  In fact, if the particular shape of the transfer zone previously described in considered (a horizontal slot extending over the whole width of the first and second passages), it is found that this latter is incapable of transferring increasing quantities of one of the first and second fluids without considerably increasing the corresponding loss of pressure. As a consequence, an exchanger of this king is only capable of functioning correctly for specified and constant rates of flow of the first fluid in the gaseous form. This exchanger can therefore not be incorporated in an installation in which the flowrate of the the first fluid and/or the flow-rate of the second fluid are liable to vary in large proportion, especially during the starting-up and stopping phases of the installation.  
  The present invention thus proposes to improve the flexibility of operation of a plate exchanger of the type previously described, in such manner that this latter may work when the flow-rate of the liquid phase and/or the flow rate of the gaseous phase of a two-phase fluid are capable of varying to a considerable extent.  
  An exchanger according to the invention is charac&#39; terized in that it further comprises a third inlet towards the first passage, defined by the first closure means, in the vicinity of the second inlet and of one extremity of the first passage, in order to introduce into the said passage the fluid which is to be received in the second passage. a third distribution means arranged in the first passage to distribute the fluid which is to be received in the second passage from the third inlet towards the interior of the first passage, substantially over the whole extent of the passage perpendicular to the longitudinal direction, and in that the transfer zone also extends in the longitudinal direction and comprises a plurality of perforations separated from each other.  
  The first passage thus plays the part of a separation chamber for the first fluid in the liquid form and the second fluid in the gaseous form, co-operating with the transfer zone in order to vary the active surface of this latter in accordance with the level of liquid obtained in the separation chamber.  
  In fact, by introducing into the first passage through the third inlet, a second portion of the fluid introduced at least into the second passage, by distributing this said portion in a substantially uniform manner in the interior of and along the whole extent of the first passage perpendicular to the longitudinal direction, according to the invention it is possible to establish a level of the first fluid in the liquid form in the first passage. As a consequence, by varying the level of the first fluid in the first passage, it is thus possible to adapt to the relative flow-rate of the first and second fluids, the section of passage necessary for the transfer of one of the first and second fluids introduced into the passage from the first passage towards the second passage.  
  In addition. the invention makes it possible to obtain a homogenous two-phase fluid distributed in a uniform manner between the passages which are reserved for it and over the entire width of these latter, irrespective of the conditions of operation of the exchanger. This was not the case prior to the invention. in particular due to imperfections of construction or to deformations caused in the exchanger during the course of its installation or during its operation.  
  In fact, if consideration is given to the particular form of the transfer zone defined prior to the invention (a horizontal slot extending over the whole width of the first and second passages), it is found that for certain conditions of operation, it is not possible to obtain the desired homogenous distribution of the two-phase fluid. On the one hand, assuming the first place that the slotted partitions of the exchanger are strictly the same and that in particular the slot of one partition is parallel to one side of the said rectangular partition. by construction, it is impossible during the course of brazing, to assemble the plate and partitions of the exchanger in such manner that the slots of the partitions are all in an exactly horizontal plane when the exchanger has once been put into the vertical position. Certain slots will necessarily be higher then others.  
  Secondly. assuming that the slots, when the exchanger has once been built, are in the same horizontal plane, its installation or its operation may cause the exchanger to become slightly inclined with respect to the vertical. The result of this is that certain slots will be higher than others with respect to the same horizontal reference plane.  
  All these disadvantages have the effect that the uniform distribution of the two-phase fluid, expected between the various second passages of the exchanger previously defined, may not be obtained for certain conditions of operation of the exchanger. Thus, if the two-phase fluid is caused to circulate in the vertical downward direction in the secnd passages of the exchanger, the first fluid is introduced in liquid form and the second fluid in gaseous form (constituting respectively the liquid and gaseous phases of the two-phase fluid) respectively in a first passage and an adjacent second passage of the exchanger, and then the first fluid is distributed into the second fluid through the horizontal slot of a partition in a second passage.  
  when the level of the first in liquid form in the first passages substantially reaches the level of the slots in the partitions, certain slots are caused to deliver none or very little liquid into the corresponding second passages, and others much more, in consequence of the differences in height of the various slots with respect to the same horizontal reference plane. The two-phase fluid obtained will thus not have the same proportions of gas or liquid from one second passage of the exchanger to another. Its distribution between the various second passages of the exchanger cannot therefore be uniform.  
  On the other hand, for a given partition, it is in the first place impossible to obtain industrially a slot which is absolutely parallel to one side of the rectangular partition to which it belongs and therefore which is absolutely horizontal when this partition is vertical. In the second place, during the course of the operation or erection of the exchanger in the installation which it belongs, it is inevitable, due to the influence of mechanical or thermal stresses, that certain partitions become slightly tilted with respect to the vertical.  
  All these disadvantages have the result that certain slots are no longer absolutely horizontal but are more or less slightly inclined with respect to the horizontal.  
  The immediate result is that for certain conditions of operation, the two-phase fluid obtained in certain second passages of the exchanger no longer gives the required homogenous and uniform distribution characteristics. Thus, again in the case of a downward vertical circulation of the two-phase fluid assumed in the previous example, when a given slot is slightly inclined with respect to the horizontal, and when the level of the liquid in a first passage comes close to the said slot, 3 part of this slot may deliver very little liquid or no liquid at all while another part delivers much more. In consequence, in the corresponding secnd passage, there will be obtained a two-phase fluid in which the liquid and gaseous phases will be distributed in a non uniform manner over the whole width of the said passage.  
  As a consequence. the plate exchangers which have the structure specified as prior to the present invention do not in practice enable an absolutely homogeneous distribution of the two-phase fluid to be obtained as between the various passages of the exchanger which are reserved for it, and in a given passage. since the practical defects previously indicated act to oppose or even annul the desired homogenous distribution. under certain conditions of operation. This is all the more true since plate exchangers, due to their design, are more subject to mechanical stresses of thermal origin than other types of exchangers.  
  On the contrary. according to the invention. due to the longitudinal extension of the transfer zone, the method of manufacture of the exchanger. its installation. the thermal and mechanical stresses resulting from its operation have no longer any practical effect in preventing the homogeneity of the two-phase fluid distributed and circulating in the exchanger.  
  In a preferred method of construction of the invention. the first fluid and the second fluid are separated on the upstream side of the exchanger along the direction of circulation of the said fluid. and the gas-liquid separation interface is maintained between the level of introduction of the first fluid into the first passage and the level of introduction of the second fluid into the first passage. This may be effected by arranging the separator vessel for the first and second fluids at the side of the exchanger and by fixing its position in height as a function of the desired level of the first fluid in the first passage of the exchanger.  
  There is thus obtained an automatic balancing (to within the pressure losses of the first and second fluids) of the level of the first fluid in the liquid form in the first passages of the exchanger. The level of liquid in the first passages being at any moment in hydrostatic equilibrium with that of the liquid contained in the separator, the variation of the liquid level of the separator thus involves that of the section of passage of one of the first and second fluid towards the second passages. If the flow-rate of the second fluid coming into the sepa rator increases with respect to the flow-rate of the first fluid reaching the separator, the level in the separator falls and correspondingly the section of passage of the second fluid towards the second passage increases, or the section of passage of the first fluid towards the second passage falls, and is therefore adapted to the increase in the flow-rate of the second fluid.  
  If the flow-rate of the second fluid coming into the separator diminishes with respect to the flow-rate of the first fluid coming into the separator, the level in the separator rises, and correspondingly the section of passage of the second fluid towards the second passage falls. or the section of passage of the first fluid towards the second passage increases, and is therefore adapted to the reduction of the flow-rate of the second fluid. According to this particular form of the invention. there is therefore a continuous and automatic adjustment of the section of passage of the first or the second fluid to the relative flow-rate of the said fluids.  
  Two essential forms of the invention may be employed. depending on whether the heat exchange is effected with a two-phase fluid circulating vertically in the upward or downward direction.  
  In the upward direction, the transfer zone is arranged in the lower part of the second plate, the first inlet is reserved for the second fluid, and at least a second inlet and the third inlet are reserved for the first fluid.  
  In the downward direction, the transfer zone is arranged in the upper part of the second plate, the first inlet is reserved for the first fluid, and the second inlet and third inlet are reserved for the second fluid.  
  The present invention will now be described with respect to the accompanying drawings, in which:  
  FIG. I is a front view of a first exchanger according to the invention, associated with a separator for a twophase fluid. enabling heat to be exchanged between this fluid circulating in the upward direction in the exchanger and another fluid circulating in the downward direction;  
  FIG. 2 is a view of the left-hand side of this exchanger, taken in the direction of the arrows lI-ll of FIG. 1&#39;.  
  FIG. 3 is a view in cross-section taken along the line IlI-III of FIG. 1 of this exchanger, associated with the above separator;  
  FIG. 4 is a view in cross-section taken along the line IV-IV of FIG 2 of this exchanger with parts broken FIG. 5 is a view in cross-section of this exchanger. taken along the line V\/ of FIG. 2, with parts broken away;  
  FIG. 6 is a view in perspective of one part of this exchanger. with parts broken away;  
  FIGS. 7, 8 and 9 are views similar to that of Flg. 6, showing three alternative forms of construction of this same exchanger;  
  FIG. 10 is a front view of a second exchanger. according to the invention. associated with a separator for a two-phase fluid, enabling heat to be exchanged between this fluid circulating in an upward direction in the exchanger, and another fluid circulating in a downward direction;  
  FIG. I1 is a view of the left-hand side of the exchanger shown in FIG. [0. taken in the direction of the arrows Xl--XI of FIG. 10;  
  Flg. I2 is a view in cross-section of the exchanger shown in FIG. 10. taken along the line XIIXII of FIG. 10, the exchanger being associated with the above separator;  
  FIG. 13 is a view in cross-section taken along the line XIIIXIII of FIG. 11, of the exchanger shown in FIG. 10, with parts broken away;  
  FIG. 14 is a view in corss-section of the exchanger shown in FIG. [0. taken along the line XIVXIV of FIG. 11. with parts broken away;  
  FIG. 15 relates to a third heat-exchanger according to the invention. similar to that described with reference to FIGS. 1 to 9. This figure represents a view in cross-section of this third exchanger taken along a line identical with the line IIl--III of FIG. 3.  
  In certain figures listed above, the circulation of the first fluid in the liquid form has been shown by full lines. that of the second fluid in the gaseous form by broken lines separated by points. that of the first and second fluids combined together by broken lines separated by crosses and that of the third fluid by broken lines only.  
  There will be described below with reference to FIGS. 1 to 9, a first heat-exchanger l according to the invention. and its operation enabling heat to be exchanged between a first and a second fluids, combined together and circulating in the exchanger 1 in a vertical upward direction, and a third fluid circulating in the exchanger in a vertical downward direction.  
  FIG. I is intended to explain the circulation of the fluids in the exchanger 1. A fluid 3 in two-phase form comes into a separator 2 arranged by the side of the exchanger at a level lower than this latter. It is separated into a liquid phase 4, or first fluid in liquid from. and a gaseous phase 5 or second fluid in gaseous form. The first fluid is sent into the exchanger through the intermediary of the distributor 6 arranged at its lower portion. The second fluid is sent into the exchanger I by means of the distributor 7 arranged on the side of the exchanger 1 in its lower half, on the left hand side looking at FIG. I.  
  The first and second fluids combined are evacuated from the exchanger I by the header or collector 8 after having exchanged heat with the first and second fluids combined together. The collector 8 is arranged in the upper half of the exchanger 1, on the right-hand side of this latter, as shown in FIG. 1. The circulation of the fluids in the interior of the exchanger I will be examined later.  
  Referring more particularly in FIGS. 2 and 3, the heat exchanger 1 comprises a plurality of rectangular metal plates 11 and 12 of identically the same contour, arranged parallel to each other and spaced from each other. For the purposes of the description, these various plates may be grouped together in sets of three. Eachh set comprises for example a first plate such as Ila. a second plate or partition such as 12 comprising a transfer zone 60, and a third plate such as Ilb.  
  A first plate or partition 12 is therefore arranged between a first plate Ila and a seond plate lIb immediately adjacent. A first closure means comprises closure bars I3 coupling each partition I2 to an adjacent plate 11, along the edge of the said plate and the said partition (see particularly FIGS. 4 and 5). The closure bars 13 are coupled in a fluid-tight manner by brazing to the edges of the plates 11 and the partitions I2 and the closure bares l3 define inside the exchanger I a plurality of first elongated passages I4 comprised between a first plate such as 11a and a second plate or partition 12, and a plurality of second elongated passages I5, comprised between a partition or second plate I2 and a third plate such as 11b. These passages are substantially flat.  
  In order to explain the structure ofa first passage 14, reference will now be made to FIG. 4. In the upper portion of a first passage 14, the closure bars 14 form a space which constitutes an inlet 16 permitting the introduction of the second fluid in the gaseous form, from the distributor 7 into the said passage. At the lower extremity of a first passage 14, the closure bars I3 form a space constituting an inlet 17 permitting the introduction of the first fluid in the liquid form from the distributor 6 into the said passage.  
  A distribution means for the first fluid, from an inlet 17 towards the interior of a first passage 14 is arranged in the lower portion of the said passage in order to distribute the first fluid over the whole width of the said passage. The first distribution means comprises a corrugated metal sheet 20 and a corrugated metal sheet 21. A metal sheet 20 has a contour with the form of a rectangular triangle, one side of which corresponds to the inlet 17; it is provided with vertical corrugations. A metal sheet 2I has a contour in the form of a rectangular trapezium, one side of which is adjacent to the metal sheet 20&#39;, it is provided with oblique corrugations. The sheets 20 and 21 are supported on one side on one face of a plate I l and on the other side on one face ofa partition 12. The sheets 20 and 21 are perforated and constitute an assembly having a rectangular contour.  
  Another distribution means for the second fluid, having an inlet 16 towards the interior of a first passage 14 is arranged in the upper part of the said passage in order to distribute the second fluid over the entire width of the said passage. It comprises a corrugated metal sheet 18 and a corrugated metal sheet I9. A sheet 18 has a contour with the form of a rectangular triangle, one side of which correpsonds to the inlet 16; its corrugations are horizontal. A sheet 19 has a contour in the form of a right-angle triangle adjacent to that preceding along its hypotenuse. Its corrugations are vertical. The sheets 18 and I9 are aupported on one side by a face of a partition 12 and on the other side by a face of a plate 11. A rectangular wide metal sheet, supported on a partition I2 and a plate 11, is arranged in the first passage 14 between the distribution means for the first fluid and that of the second fluid.  
  As explained in Flg. 4 by the breaking away of part of the corrugated sheet 22, a second plate or partition I2 comprises at its lower poriton a transfer zone 60 comprising a plurality of holes 23 permitting the second fluid to be transferred into a second passage 15. These holes are distributed in the second plate 12 in vertical rows and thus in the longitudinal direction of the exchanger. The perforated portion or transfer zone 60 of a partition 12 is comprised between an inlet 16 and an inlet 17 and extends subs tantially over the whole length of the sheet 22 and along the whole width of the passages 14 and 15. The holes 23 communicate with the channels defined by the corrugations of the sheets 22.  
  FIGS. 3 and 4 also indicate that the space included between a first plate such as Ila and a partition I2, and one part of which corresponds to a first passage 14, is divided into two by a second closure means. This latter is a horizontal bar 24 coupling together a plate Ila and a partition 12 in a fluid-tight manner in the lower half of the excahnger 1.  
  Along the longitudinal and vertical direction of the exchanger 1, and inlet I6 is arranged between a bar 24 and the transfer zone 60 ofa partition 12. A bar 24 thus defines in the space included between a first plate Ila and a partition 12, in addition to a first passage 14 arranged on one side of the bar 24, a third passage 25 arranged on the other side of the bar 24, extending over the major part of the length of the exchanger, comprised between a first plate Ila and a second plate 12 and reserved for the third heat-exchanger fluid.  
  According to FIG. 4, the closure bars I3 also define in the lower part and in the upper part of the third passage 25, repsectively a space serving as an inlet 26 and another space serving as an outlet 27.  
  An inlet 26 permits the introduction of the third heatexchange fluid from the distributor 9 into a passage 25. An outlet 27 permits the evacuation of a third fluid from a third passage 25 towards the collector I0.  
  A distribution means for the third fluid from an inlet 26 towards the interior of a first passage 25 is arranged in the upper part of the said passage in order to distribute the third fluid over the whole width of the said passage. This means comprises two metal sheets 28 and 29. A sheet 28 has a contour with the form ofa rectangular triangle. one side of which corresponds to the inlet 26&#39;. it has horizontal corrugations A metal sheet 29 has a contour in the from of a rectangular triangle adjacent to that preceding and along its hypotenuse; it has vertical corrugations. The metal sheets and 2] are perforated and from an assembly with a rectangular contour.  
  A collection means for the third from the interior of a first passage towards an outlet 27. is arranged at the lower part of said passage so as to collect the third fluid along the whole width of the said passage. This means comprises two metal sheets and 31. A sheet 30 has a contour in the form of a rectangular triangle. of which one side corresponds to the outlet 27; it has horizontal corrugations. A sheet 3l has a contour with the form of a rectangular triangle adjacent to that preceding and along its hypotenuse. it has vertical corrugations.  
  The sheets 30 and 3l are perforated and form an assembly with a rectangular contour. A corrguated sheet 32 having its corrugaitons vertical in arraged in each third passage 25, between the distribution means and the collection means associated with the said passages. Each sheet 32 extends along the major part of the length of a passage 25. The corrugated sheets 28, 29, 30. 3l and 32 are supported on one side against a second plate or partition 12 and on the other side against a first plate lla.  
  In order to explain the structure of a second passage 15, reference will now be made to FIG. 5. The closure bars 13 form at the lower extremity and the upper extremity of a second passage 15, respectively a space adjacent to an inlet 17, serving as an inlet 33 for the first fluid in the liquid form coming from the distributor 6, and a space serving as an outlet 34 for the fluid formed by the combination of the first and second heat exchange fluids evacuated by the collector 8.  
  A distribution means for the first fluid. from an inlet 33 towards the interior of a second passage 15, is arranged in the lower part of the said passage in order to distribute the first fluid over the whole width of the said passage. This means comprises two corrugated sheets 35 and 36. The sheet 35 has a contour in the form of a rectangular triangle. one side of which corresponsd to the inlet 33; its corrugations are vertical. The sheet 36 has a contour in the form ofa rectangle trapezium adjacent to the preceding triangle; its corrugations are oblique. The sheets 35 and 36 are perforated and constitute an with wit a rectangular contour.  
  A collection means for the fluid corresponding to the combination of the first and second fluids from the interior of the first passage 15 towards an outlet 34, is arranged at the upper part of the said passage in order to collect the said fluid over the whole width of the said passage. This means comprises two corrugated sheets 37 and 38. A sheet 37 has a contour in the form of a rectangular triangle. of which one side corresponds to the outlet 34; it corrugations are vertical. A sheet 38 has a contour in the form of a rectangular trapezium adjacent to the preceding triangle; its corrugations are oblique.  
  The sheets 37 and 38 are perforated and constitute an assembly having a rectangular contour.  
  The major part of a passage 15 is occupied by a corrugated sheet 39. arranged between the collection means and the distribution means of the first fluid, and  
 the corrugations of which are vertical. The sheets 35. 36. 37. 38 and 39 are supported on one side with a second plate or partition 12 and on the other side with a third plate 116.  
  As illustrated by the broken away part of the sheet 39 shown in FIG. 5. the perforations 23 of the transfer zone 60 and of a partition 12 communicate with the channels defined by the corrugations of the sheet 39.  
  In order to describe the operation of the exchanger 1. more particular reference will be made to FIG. 3. In operation. the heat is thus exchanged between the first and second fluids combined together and circulating in the second passages 15 in the vertical and longitudinal direction of the exchanger, and the third fluid circulating in the adjacent third passages 25 of the exchanger.  
  For that purpose. a first part and a second part of the first fluid in the liquid form are introduced respectively through the inlet 33 at the lower level of a second passage 15 and through the inlet 17 at the lower level of a first passage 14. The first fluid received and introduced into all the passages 14 and 15 of the exchanger is distributed in a substantially uniform manner over the entire width of the said passages. by means of the distributors 20, 21 and 35. 36 respectively.  
  Through the inlet 16 there is introduced the second fluid in the gaseous form at the upper level of a first passage 14, above the transfer zone 60. By means of the distributor l8, l9, the second fluid introduced and received in each first passage 14 is distributed from the top to the bottom in a substantially uniform manner over the entire width of the said passage.  
  In each of the first passages 14, playing the part of a separation chamber for the first fluid in liquid form and for the second fluis in gaseous form. there is thus obtained a gas-liquid interface between the first and the second fluids. In view of the vertical relative position of the separator 2 and the exchanger 1, this interface is adjacent to that which is established in the separator 3 between the first and second fluids, but it is slightly less than this latter since the pressure losses of the first fluid and of the second fluis in their respective distributors of the first passages 14 are not equivalent; the first are greater than the second. The gasliquid interface of the separator 2 is thus maintained between the level of introduction of the first fluid and the level of introduction of the second fluid into the first passages 14.  
  The second fluid and the first part of the first fluid introduced into a first passage 14 and the second part of the first fluid introduced into a second passage 15 over the whole width of the first and second passages are joined together through the transfer zone 60 of a partition 12 in a second passage 15. By distribution of the second fluid into the first fluid, there is thus obtained in the second passages 15 a homogeneous two-phase fluid distributed in a uniform manner along the whole width of the said passages. This two-phase fluid then circulates in the upward direction. following the vertical and longitudinal direction of the exchanger. in the second passages 15. It exchanges its heat with the third fluid circulating in the third passages 25 and is then collected by the collector 37, 38 and evacuated from the upper part of the exchanger through the outlet 34.  
  As indicated above. the separation chamber or first passage 14 cooperates with the transfer zone 60 in order to adapt the working surface of this latter in accordance with the level of the liquid in the said passage [4. in fact. the variation of the liquid level in the first passages l4 permits a variation of the section of passage necessary for the transfer of the second fluid towards the second passages 15 by means of the longitudinal distribution of the holes 23. It is thus possible to adapt this section to the relative flow-rate of the first and second fluids.  
  The arrangement described of the separator 2 makes it especially possible to adapt this section automatically to this relative flow-rate. In fact, the liquid level of the passages 14 located in the transfer zone 60 of each partition l2, varies as a function of the variations of the liquid level in the separator 2. In consequence. as the flowrate of the second fluid becomes greater with respect to the flow-rate of the first fluid. the section of passage obtained for the second fluid increases; and as the flow-rate of the second fluid becomes small as compared with the flow-rate of the first fluid, the smaller becomes this section of passage. In this case, there is therefore an automatic regulation of this section of passage.  
  Various modifications may be made to the exchanger 1 described with reference to FIGS. 1 to 6, without thereby departing from the scope of the present invention. In particular. the transfer zone of a second plate or partition 12 may be modified in accordance with FIGS. 7 to 9.  
  According to FIG. 7, the transfer zone comprises a plurality of slots 40, perpendicular to the longitudinal direction of the exchanger. or horizontal, distributed longitudinally in a partition I2.  
  According to FIG. 8, the transfer zone comprises a plurality of oblique slots 41 distributed longitudinally in a partition 12.  
  According to FIG. 9, the transfer zone comprises a plurality of slots 42 elongated in the longitudinal direction of the exchanger, or vertically.  
  There will now be described below with reference to FIGS. 10 to l4, a second heatexchanger 50 according to the invention, and its operation, permitting exchange of heat between a first and a second fluids combined together and circulating in the exchanger 50 in a downward vertical direction. and a third fluid circulating in the exchanger 1 in a vertical upward direction.  
  In order to simplify the description, the elements of this exchanger 50, identical to those already described for the previous exchanger I, have been given the same reference numbers.  
  In FIG. I0, the fluid in a two-phase form is separated in a separator 2 arranged at the side of the exchanger 50 at a higher level than this latter. The first fluid 4 in the liquid form and the second fluid 5 in the gaseous form are sent into the exchanger 50 through the intermediary respectively of a distributor 6 mounted on the side and in the upper half of the exchanger 50, and a distributor 7 mounted above the exchanger 50. The first and second fluids combined are evacuated from the exchanger 50 by a collecter 8 arranged below the exchanger 50. The third fluid which is to exchanger its heat with the first and second fluids combined, is introduced into and evacuated from the exchanger 50 respectively by a distributor 90 located below the exchanger 50 and a collector 10 mounted on the side and in the upper half of the exchanger 50. The circulation of the fluids in the interior of the exchanger 50 will be examined below.  
  Referring now more particularly to FIGS. 12 and 14, it is found that the structure of the exchanger 50 is similar to that of the exchanger 1 previously described. Thus, only the differences as compared with the exchanger 1 will now be enumerated:  
 1. The first closure means comprising the bars 24 is arranged in the upper part of a space comprised between a first plate Ila and a second plate or partition 12. The bars 24 thus respectively delimit, in the upper portion and in the lower portion of a said space, a first passage 14 extending along at least part of the length of the exchanger 50, and a third passage 25 extending along the major part of the length of the exchanger 50.  
 2. The transfer zone 60 of a partition 12 comprising the perforations 23, is arranged in the upperpart of a said partition, between the inlet 17 of the first fluid and the inlet 16 of the second fluid in a first passage 14 and above a bar 24.  
 3. No inlet is provided for the first fluid, from a distributor 6 towards a second passage 15. On the other hand, an inlet 51 corresponding to the space defined by the closure bars 13 at the upper extremity of a second passage 15, enables the second fluid to be introduced from the distributor 7 towards a second passage 15.  
 4. The form of the distribution and collection means for the fluids entering and passing out of the exchanger 50, relative to the various passages 14, I5 and 25 formed in this latter, differs from that described for these same means in the exchanger 1.  
 5. Since the distributor and collectors for the various fluids circulating in the exchanger are arranged at places in this latter different from those of the exchanger 1, the fluid inlets and outlets for the various passages 14, 15 and 25 are modified in a corresponding manner and in accordance with the description referring to FIG. 10.  
  According to FIG. 12, in operation, the first fluid in the liquid form is introduced exclusively at the lower extremity of a first passage 14 through the distributor 6 and an inlet 17. A first part of the second fluid in the gaseous form is introduced into the upper extremity of a second passage 15 adjacent to the first passage 14, through the distributor 7 and an inlet 51. A second part of the second fluid is also introduced into the first passage through the distributor 7 and an inlet 16.  
  In a passage 14 there is thus established a gasliquid interface between the first and second fluids, in hyrostatic equilibrium (to within in the pressure losses) with that of the separator 2. The third fluid is introduced into the lower extremity of a third passage 25 located below a first passage 14, through the distributor 9 and an inlet 26. These fluids are distributed in a substantially uniform manner in the interior of their respective passages. from their respective inlets. along the entire length of the said passages.  
  The first portion of the second fluid and the first fluid are combined in a second passage 15, essentially by transfer and distribution of the first fluid into the first portion of the second fluid, of the first passage 14 towards the second passage 15, through the perforations 23 of the transfer zone of a partition 12.  
  The first and second fluids combined then constitute a homogeneous two-phase fluid along the whole length of the passages 14 and 15, which moves into a second passage 15 in a vertical downward direction. This fluid exchanges its heat with the third fluid circulating in a passage 25 in a vertical upward direction, The first and second fluids combined are collected and evacuated at the lower extremity of the exchanger 50, after having exchanged their heat with the third fluid, through an outlet 34 and the collector 8. The third fluid is collected and evacuated from the exchanger 50 through an outlet 27 and the collector 10.  
  As previously described for the exchanger 1, the sec tion of passage of the first fluid passage 14 towards a second passage 15 is capable of varying by variation of the level of the liquid in a passage 14, and in particular of adapting itself automatically to the relative flowrates of the first and second fluids.  
  The third exchanger, as shown in FIG. 15, only differs from the first exchanger in accordance with FIGS. 1 to 9, by the addition of another second passage adjacent to a first passage 14 and to a third passage 25. In consequence, in an exchanger according to FIG. 15, a first passage 14 and a third passage 25 are comprised between two second passages. Thus, this third exchanger will now be described starting from the structure of the first exchanger previously described.  
  As for the first exchanger. three consecutive plates 61, 62 and 63 respectively define a first passage 14 for the reception of the second fluid in the gaseous form comprised between a first plate 61 and a second plate 62, a second passage 15a for the reception of the first fluid in the liquid form and for circulating the first and second fluids combined along the longitudinal and vertical direction of the exchanger, comprised between the second plate 62 and a third plate 63, and the heatexchange relation with a third passage 25 located above the first passage 14, and also comprised between the first plate 61 and the second plate 62.  
  On the other hand, a fourth plate 64, arranged opposite the first plate 61, defines with this latter another second passage 15b for the reception of the first fluid and for circulating the first and second fluids combined in the longitudinal direction of the exchanger, also in heat-exchange relation with the third passage 25.  
  As in the previous case, the second plate 62 also comprises a transfer zone 60a for the second fluid towards the second passage 15a, extending over the entire width of the first and second passages 14 and 15a, and along the longitudinal direction of the exchanger, and comprising a plurality of perforations 23 separated from each other. However, this is also the case for the first plate 61 which, as shown in FIG. 15, comprises a transfer zone 60b for the second fluid towards the other second passage 15b, identical with the transfer zone 60a of the second plate 62.  
  As previously explained, the first closure means (closure bars 13) defines a first inlet (not shown) towards a first passage 14, located at the upper extremity of this latter, so as to introduce the second fluid in the gaseous form, a second inlet (not shown) towards the second passage 15a adjacent to the lower extremity of the said passage. for the introduction of the first fluid in the liquid form. However, the bars 13 also define another second inlet (not shown) towards the other second passage 15b, in the vicinity of the lower extremity of the said passage, for the introduction of the first fluid.  
  As in the previous embodiment. the transfer zone 60a is arranged between the first inlet and the second inlet, and this is also true for the transfer zone 60b arranged between the first inlet and the other second inlet. As previously, a first distribution means, 18, 19, for the second fluid is arranged in the upper portion of the first passage 14, a second distribution means 350, 36a for the first fluid is provided in the lower part of the second passage 15a. Similarly also, another second distribution means 35b, 36b of the first fluid is arranged in the lower part of the other second passage 15b in order to distribute the first fluid from the other second inlet towards the interior of the other second passage 15b, substantially along the entire width of the said passage.  
  As previously explained, the first closure means (closure bars 13) also defines a first outlet (not shown) from the second passage 15a adjacent to the upper extremity of this latter, in order to evacuate the combined first and second fluids. Similarly, this same means defines another first outlet (not shown) from the other second passage 15b in the vicinity of the upper extremity of the said passage, in order to evacuate the first and second fluids combined.  
  The operation of the third exchanger shown in FIG. 15 is similar to that described in respect of the first exchanger. Through a first inlet previously described, the second fluid is introduced in the gaseous form into a first passage 14 of the third exchanger, and this second fluid is distributed in a substantially uniform manner by means of the distributor 18, 19 in the interior and over the whole width of the first passage 14. Through the second inlet and the other second inlet previously described, there is introduced a first part and a second part of the first fluid into a second passage 15a and another second passage 15b respectively of the exchanger, both adjacent to the first passage 14. The first part and the second part of the first fluid are respectively distributed through the interior and over the whole width of the second passage 15a and the other second passage 15b by means of the distributor 35a, 36a and the distributor 35b, 36b respectively. The re are combined in the second passage 15a, by passing through the transfer zone 60a, and into the other second passage 15b by passing through the transfer zone 60b respectively, a part of the second fluid with the first part of the first fluid, and another part of the second fluid with the second part of the first fluid, this being effected over the whole width of the first, second and other second passages.  
  There is thus formed a part of a homogeneous twophase fluid and another part of this same fluid, distributed in a uniform manner respectively in the second passage 15a and in the other second passage 15b over the whole width of the said passages. The said part and the said other part of this two-phase fluid are circulated in the vertical upward direction, respectively in the second passage 15a and in the other second passage 15b in heat-exchange relation with the third fluid circulating in the vertical downward direction in a third passage 25.  
  A third part of the first fluid is introduced into the first passage 14 through a third inlet located at the lower extremity of this latter, in order to establish a level of the first fluid in the liquid form in the first passage 14.  
  By means of a distributor 20, 21, arranged in the lower part of the passage 14, this third part is distributed in a uniform manner through the interior and along the whole width of the said passage 14. The section of passage necessary for the transfer of the second fluid from the first passage 14 towards the second passage through the transfer zone 60a, and towards the second passage 15b through the transfer zone 60b is adapted to the relative flow-rates of the first and second fluids by varying the level of the first fluid in the first passage 14.  
  The exchangers according to the invention may be utilized with advantage in various sectors for the liquefaction and separation of gases. In particular there may be cited the liquefaction and de-nitrogenation of natural gas. extraction of hydrogen from a furnace gas, etc.  
 What I claim is:  
  1. In a plate-type heat exchanger comprising a plurality of metal plates 1 la. 11b and 12) having a substantially similar contour and being parallel to and spaced apart from each other along a first axis. said exchanger comprising a first closure means (13) coupling said plates to each other along the edge of each plate. said first closure means and said plates delimiting a plurality of passages (14, 15 and 25); at least three consecutive plates defining respectively a first passage (14) for the reception of one portion taken from one of a first fluid in liquid form (4) and a second fluid in gaseous form (5 comprised between a first plate 11a) and a second plate (12). and at least one second passage for receiving another portion taken from the other (4) of said first fluid and said second fluid and for circulating said one portion and said another portion combined together in directions parallel to a second axis extending parallel to said metal plates, comprised between said second plate (12) and a third plate (11b); a transfer zone (60) formed in said second plate (12) for transferring at least part of said one portion from said first passage (14) towards said second passage (15). said zone extending in a direction parallel to a third axis perpendicular to said first and second axes; said first closure means (13) defining respectively a first inlet (16) toward said first passage (14) for introducing said one portion. and at least one second inlet (33) towards said second passage (15). adjacent to one extremity of said second passage, for introducing said another portion, said transfer zone (60) being provided between said first and said second inlets; first distribution means (18, 19) disposed in said first passage (14) for distributing said one portion from said first inlet (16) towards the interior of said first passage (14), over a distance in a direction parallel to said third axis; second distribution means (35, 36) disposed in said second passage (15) for distributing said another portion from the second inlet toward the interior of said second passage, over a distance in a direction parallel to said third axis; said first closure means (13) defining at least one first outlet (34) from said second passage (15) adjacent to the other extremity of said second passage. for evacuating the combined said one portion and said another portion; and means acting in heat exchange relation with at least said second passage (15) for defining a third passage (25) for a third fluid; the improvement comprising a third inlet (17) toward said first passage, defined by said first closure means (13), adjacent to said second inlet (33) and to one extremity of said first passage, for introducing into said first passage (14) a further portion of the fluid (4) from which said another portion is taken. so as to establish a level of said first fluid in liquid form within said first passage; and third distribution means (20, 21) arranged in said first passage for distributing said further portion, from the third inlet 17) toward the interior of said first passage, over a distance in a direction parallel to said third axis, said transfer zone extending also in a direction parallel to said second axis.  
  2. An exchanger as claimed in claim 1, in which said transfer zone comprises a plurality of distinct perforations identical to each other, and uniformly distributed in said zone.  
  3. An exchanger as claimed in claim 2, in which said transfer zone comprises a plurality of slots elongated in a direction parallel to said second axis.  
  4. An exchanger as claimed in claim 2, in which said transfer zone comprises a plurality of orifices distrib uted along directions parallel to said second axis.  
  5. An exchanger as claimed in claim 2, in which said transfer zone comprises a plurality of slots extending in a direction parallel to said third axis, and distributed along directions parallel to said second axis.  
  6. An exchanger as claimed in claim 2, in which said transfer zone comprises a plurality of slots, extending in a direction oblique to said second and third axis, and distributed along directions parallel to said second axis.  
  7. An exchanger as claimed in claim identical and further comprising another second passage (15b) for the reception of the fluid (4) to be received in said second passage (15a) and for the circulation of said combined first and second fluids, in heat exchange relation with said third passage (25). comprised between said first plate (61) and a fourth plate (64) disposed opposite to said first plate (61 said first plate (61) comprising a transfer zone (b) for transferring another part of the fluid to be received in said first passage toward the other second passage (15b), said zone being ideintical with that (600) of said second plate (62); said first closure means (13) defining another second inlet to ward plate other second passage (15b). adjacent to one extremity of said other second passage. for the introduction of the fluid to be received by said other second passage, the transfer zone (60b) of said first plate (61) being disposed between said first inlet (16) and the other second inlet; said first closure means (13) defining another first outlet from the other second passage 15b), adjacent to the other extremity of said other second passage for evacuating said combined first and second fluids; and said exchanger comprising another second distribution means (35b) disposed in the other second passage (15b) for distributing the fluid to be received by said other second passage, from the other second inlet toward the interior of the other second passage. over a distance in a direction parallel to said second axis.  
  8. An exchanger as claimed in claim 1, mounted vertically, in which said transfer zone (60) is disposed in the upper portion of said second plate (12). and in which said first inlet (17) receives only said first fluid (4) while said second inlet (16) and said third inlet (51) receive only said second fluid (5).