Patent Publication Number: US-6901996-B2

Title: Coolant/air heat exchanger core assembly

Description:
TECHNICAL FIELD 
   This invention relates to a coolant/air heat exchanger core assembly with at least two plates, between which a coolant passage and an air passage are formed, wherein the coolant passage has a plurality of channels which are bounded at the sides by partitions arranged perpendicular to the plates and fixed to these by soldering and which are so connected together at their ends in serpentine or meandering form by diverting sections that coolant passes through them one after the other. 
   BACKGROUND OF THE INVENTION 
   Heat exchanger devices produced with heat exchanger cores or core assemblies of this kind are needed for example in compressed air installations for extracting the moisture from compressed air created by means of a compressor and under a pressure of e.g. 25 bar, in order to make the air suitable for critical applications, such as in the foodstuffs and paper industries or the medical field. The drying of the air is effected in that the heated air arriving from the compressor is passed—after passage through an after-cooler—through a device which includes an air/air and a coolant/air heat exchanger. While the air/air heat exchanger is mostly manufactured in the form of a plate heat exchanger of conventional construction, the coolant/air heat exchanger mostly consists of a combined tube/plate heat exchanger with a core which has air passages and intervening coolant passages formed by plates and bars holding these spaced apart. The coolant passages each consist for example of tubes of round or square cross-section arranged between two plates, with straight sections and diverting sections connecting these in serpentine or meandering form (EP 0 521 298 A2). 
   The serpentine or meandering disposition of the tubes for the coolant gives the advantage that the coolant is circulated through heat exchanger core instead of, as usual, flooding the core, i.e. the coolant circulates through the straight tube sections one after the other and not in parallel. However, a disadvantage of this construction is that unused spaces result between the individual tube sections, which results in the length of the coolant/air beat exchanger core mostly having to be made greater than the length of the air/air heat exchanger grid. Moreover the curved diverting sections lie as a rule outside the space occupied by the actual core, so that they do not participate in the heat exchange. 
   In addition it has already been proposed (likewise EP 0 521 298 A2) to replace the passages through which the coolant flows by tube and diverting sections, produced in the conventional plate construction in which the tube and diverting sections are bounded by conventional bars running in transverse and longitudinal directions, arranged between the plates. Circulation through the core is indeed likewise achieved with such an arrangement. However, a disadvantage is that either comparatively thick bars have to be provided, in order to provide sufficiently large soldering areas for stable soldered joints, so that reduced flow cross-sections are obtained for given overall dimensions of the core, or narrow bars have to be used, which favour good flow cross-sections, but comparatively small soldering surfaces have to be taken into account. A consequence of this is that overall a compromise always has to be found between the cross-section of the coolant passages and the size of the soldering areas and the strength of the heat exchanger core which can be obtained thereby. In view of the fact that for many applications burst pressures for the core of 100 bar and more have to be provided, it follows that the overall dimensions of the heat exchanger core are affected substantially by the thickness of the bars bounding the channels. 
   In the ligth of the above it is an object of this invention of so forming the coolant/air heat exchanger assembly of the kind above specified that it can be produced with the required strength using cost effective manufacturing processes. 
   A further object of this invention is to design the heat exchanger core assembly mentioned above such that it can be manufactured without remarkable problems by means of usual soldering. 
   Yet another object of this invention is to provide the core assembly mentioned above with comparatively large flow cross-sections for the coolant with given overall dimensions. 
   SUMMARY OF THE INVENTION 
   These and other objects are solved according to this invention in that the partitions are formed by webs and/or flanges of profiles with I and/or U shaped cross-sections arranged between the plates. 
   Because of the use according to the invention of the webs and/or flanges of profiles to form the partitions between the coolant channels, greater flow cross-sections of the coolant passages tan previously can be realised for given dimensions of the heat exchanger core, without having to take into account reduced strength with the use of conventional soldering methods, especially salt bath soldering. 
   Further advantageous features of the invention appear from the dependent claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained below in more detail with reference to embodiments, in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a schematic front view of a combined coolant/air and air/air heat exchanger block for cold driers in compressed air installations; 
       FIGS. 2 and 3  are sections along the lines II—II and III—III in  FIG. 1 ; 
       FIG. 4  is an enlarged front view of the core of the block according to  FIG. 1  provided for the coolant/air heat exchange; 
       FIG. 5  is a section along the line V—V of  FIG. 4 ; 
       FIG. 6  is a further enlarged front view of a portion X of a single coolant passage of the core according to  FIG. 4 ; 
       FIG. 7  is a plan view of the coolant passage according to  FIG. 6  with omission of an upper plate; 
       FIG. 8  is a front view in greater magnification of a single I profile of the coolant passage according to  FIGS. 6 and 7 ; 
       FIG. 9  shows schematically a plate forming a coolant passage, for a heat exchanger core according to  FIGS. 1  to  3 , in a partially broken away, perspective view; 
       FIG. 10  is a section along the line X—X of FIG.  9 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   According to  FIGS. 1  to  3  a heat exchanger device for cold driers in compressed air installations includes a coolant/air heat exchanger in the right part and an air/air heat exchanger in the left part. Only one coolant/air heat exchanger net or core  1  and one adjoining air/air heat exchanger net or core  2  are shown, the two being combined in an integral core assembly and forming a single, unitary block  3 . Naturally it would alternatively be possible to manufacture and operate the two cores  1  and  2  as separate components. 
   The two cores  1  and  2  are mainly formed by plane-parallel, rectangular or square plates  4 , which extend over the whole width and length of the block  3 . According to  FIGS. 1 and 3  a part of the plates  4  are held spaced in pairs on the one hand by bars  5   a  and  5   b  running perpendicular to the longitudinal direction and arranged at ends of the block  3  at the right and left in FIG.  3  and on the other hand by bars  7 ,  8  extending in the longitudinal direction and disposed at the side edges of the plates  4 . Passages  9  thus result between these plates  4 . At the left end in  FIG. 3  the upper bars  7  are somewhat shorter, so that spaces  10  result between their left ends and the bars  5   a , through which air can enter from the side in the direction of an indicated arrow  11 . Correspondingly the upper bars  7  are somewhat shorter at the right end in  FIG. 3 , so that spaces  12  result between their right ends and the bars  5   b , through which the air can emerge to the side in the direction of the indicated arrow  14 . Customary lamellae  15  shown only partially in  FIG. 1  are moreover advantageously fitted in the passages  9  and their passages are diverted along the lines  16 ,  17  by 90° in accordance with FIG.  3 . 
   The other part of the plates  4  are held spaced apart in pairs, according to  FIGS. 1 and 2 , in the part forming the core  2 , by bars  18  and  19  running parallel to the longitudinal direction and arranged at the side edges of the plates  4  and extending up to the left end of the core  1  in  FIGS. 1 and 2 , as well as terminating bars  20   a  and  20   b  running transversely to the former and forming the left and right ends of the core  2 . Accordingly a further passage  21  results between each two plates  4 . At the sides of the terminating bars  20   a  and  20   b  the upper bars  18  in  FIG. 2  are somewhat shorter, so that spaces  22   a ,  22   b  result between them and the two bars  20   a ,  20   b , through which air can enter and leave at the side and be fed in and out in the direction of the indicated arrows  23 ,  24  (FIG.  2 ). The deflection is like in  FIG. 2  preferably effected by suitably formed lamellae  25  provided in the passages  21 . 
   In the core  1  the same plates  4  which bound the passages  21  serve to form serpentine or meandering passages  26 , which comprise straight sections and sections serving for the diversion and which are explained in more detail below. The passages  26  each extend from one of the terminating bars  20   b  to a terminating bar  27 , which is located at the right end in  FIGS. 1 and 2  of the block  3 . Plate pairs with the passages  9  and plate pairs with the passages  21 ,  26  preferably alternate in superimposed planes, where at least one each of the passages  9 ,  21 ,  26  is provided. A coolant is fed into the passages  26  at an inlet denoted by an arrow  28  and can flow out again at an outlet indicated by an arrow  29  and flows through a coolant circuit, not shown. 
   The inlets and outlets denoted by the arrows  11 ,  12 ,  23 ,  24  and  28 ,  29  are connected to inlet nipples, collecting tanks or the like, not shown, known per se. 
   The manner of operation of the described heat exchanger device is essentially as follows: 
   The compressed air arriving from a compressed air installation, heated to about 35-55° C. for example, is fed in in the direction of the arrow  11 , so that it flows through the passages  9 . The air is first cooled to a temperature of 20° C. in the core  2  by the cold air arriving from a water separator, fed in counterflow in the direction of the arrow  23 . In its further travel through the passages  9  the compressed air is gradually cooled to its dew point in the core  1 , since it here interacts with the coolant, which flows into the passages  26  in the direction of the arrow  28  (FIG.  2 ). The compressed air is then taken off at the outlet denoted by the arrow  14  ( FIG. 3 ) and fed to a water separator, not shown, from whence it is fed into the core  2  at the arrow  23  and taken off at the outlet denoted by the arrow  24 , which serves as a tapping point for the compressed air. The arrangement is so designed that the air is again heated to approaching room temperature at the tapping point. 
   Heat exchanger devices of the kind described and their manner of operation are generally known to the man skilled in the art (EP 0 521 298 A2) and therefore do not need to be explained in more detail. 
   In a preferred and so far regarded as the best embodiment of the invention, each coolant passage for the core/part  1  of the coolant/air heat exchanger is formed by a plurality of channels connected for flow one after the other, arranged in each case between two plates  4  and produced with the aid of individual profiles with an I-shaped cross-section arranged parallel alongside one another. As an alternative to this, a second embodiment for the core is shown in  FIG. 9 , in which the channels are formed from I-shaped profiles connected together in one piece and arranged one after the other. 
   As  FIGS. 4 and 5  in particular show, the plates  4  of each associated pair are held spaced apart by bars  30  and  31 , which extend transverse to a longitudinal axis  32  of the core  1  and have a square or rectangular cross-section, in order to form plane parallel hollow spaces therebetween. The bar  30  can correspond to the bar  20   b  according to FIG.  2 . In between the plates  4  of each of these pairs are moreover arranged a plurality of profiles  33  with I-shaped cross-sections, seen especially in  FIGS. 6 and 8 , which comprise webs  33   a  extending perpendicular to the longitudinal axis  32  and to the plates  4  and are arranged parallel to one another. At both ends of each web a strip or flange  33   b ,  33   c  is arranged perpendicular to the webs  33   a . The heights h of the profiles  33  ( FIG. 6 ) correspond to the heights of the bars  30  and  31 , so that outer surfaces  33   d ,  33   e  (Pig.  8 ) of the flanges  33   b ,  33   c  bear against the plates  4  disposed above and below them in the assembled state. Accordingly, a plurality of channels  34  are provided between the plates  4  as  FIG. 6  in particular shows, which channels  34  extend substantially perpendicular to the longitudinal axis  32 . The channels  34  are each bounded at the sides by two webs  33   a  and above and below by the associated flanges  33   b ,  33   c  of the profiles  33 . The spacings a ( FIG. 6 ) of the profiles  33  are preferably made so large that spaces  35  each with a width b remain between the facing edges of their flanges  33   b ,  33   c , so that the channels  34  are bounded there not by the flanges  33   b ,  33   c  but by portions of the plates  4  bridging over the flanges  33   b  and  33   c . Finally the surfaces  33   d ,  33   e  ( FIG. 8 ) are preferably slightly domed convexly outwards for reasons explained below. 
   As  FIGS. 5 and 7  show in plan view, the profiles  33  are preferably of the same length in their longitudinal direction running perpendicular to the longitudinal axis  32  but are alternately offset forwards and rearwards relative to one another. The arrangement is such that the one end of a first profile  33  neighbouring the bar  30  is arranged at a certain spacing from the lower edge in  FIG. 7  of the associated plate  4 , while the other end terminates flush with the upper edge of the plate  4  in FIG.  5 . The same applies to the following third, fifth, etc., profiles  33 . Conversely, the intervening profiles  33 , i.e. the second, fourth, etc., profiles are so offset relative to the profiles with odd numbers that they terminate with their ends flush with the lower edges of the plates  4  in  FIGS. 5 and 7 , while their opposite ends terminate spaced from the respective upper edges of the plates  4 . Accordingly free spaces or diverting sections  36  result alternately at the one and the other plate edges and connect together the parallel channels  34  at their upper and lower ends in  FIG. 5 , into a serpentine or meandering passage for the flow. 
   At the ends of each of the first and last profiles  33  one of the diverting sections  36   a ,  36   b  serves for connection of a connecting nipple, collecting tank or the like, in order to feed the coolant thereby in and out in the direction of the arrows  28 ,  29  (FIG.  5 ). The other diverting sections  36  are bounded or closed to the outside by plugs  37 , which have a height corresponding to the height h ( FIG. 6 ) and a width which is advantageously substantially equal to the difference of twice the spacing a and the width of a web  33   a  in  FIGS. 6 and 7 , or equal to the sum of twice the width of the flanges  33   b ,  33   c  and twice the width b less the width of a web  33   a  and should at least be equal to the sum of the spacing a and the width b of a space  35 . The plugs  37  each lie in a space which is bounded on the one hand by the webs  33   a  and by the plates  4  and on the other hand by the facing ends of the flanges  33   a ,  33   b  of those profiles which adjoin the one or the other edge of the plates  4 . The plugs  37  bear both on the plates  4  and the webs  33   a  as well as on the ends of the flanges  33   b ,  33   c.    
   The fixing, of the various parts to one another is preferably effected by soldering in a salt bath. In order that the flux, salt solutions and solder employed, air and like can flow into the channels  34  unimpeded, penetrate from thence into the gaps between the plates  4 , profiles  33  and plugs  37  and also flow out again without impediment, channel sections present between the plugs  37  and the profiles  33  preferably remain open until completion of the soldering operation. At the conclusion of the soldering operation and complete running out of the fluids, these channel sections are then closed, preferably by a welding operation. This can be carried out without problems in view of the comparatively small space remaining (e.g. a=10 mm, b=2 mm, h=10 mm). 
   The plates  4 , profiles  33  and plugs  37  preferably consist of aluminium. In order to braze these parts to one another, the plates  4  and plugs  37  preferably have layers plated with a suitable solder at the corresponding surfaces, as is generally known in the production of aluminium coolers for example. The soldering operation is moreover facilitated in that the surfaces  33   d ,  33   e  of the flanges  33   b ,  33   c  are slightly arched or rounded, since wedge gaps result from this when they abut the flat plate surfaces, which gaps ensure a large area wetting of the connecting parts. 
   The I-shaped cross-section of the profiles  33  has the substantial advantage that on the one band comparative large surfaces  33   d ,  33   e  ( FIG. 8 ) available for the soldering operation are obtained at the ends of the profiles  33  and on the other hand the cross-sections of the profiles  33  are comparatively small in the middle part and accordingly the cross-sections of the channels  34  bounded thereby are comparatively large. Accordingly there are achieved on the one hand a high pressure tightness of the passages formed by the channels  34  and diverting sections  36  and on the other hand a high efficiency of the heat exchange, because a larger flow cross-section can be provided in a narrow space. On account of the high packing density of the channels  34  the width of the coolant/air heat exchanger core  1  can be substantially shorter that hitherto and thus the complete device of air/air and coolant/air heat exchanger can be made substantially more compact and smaller. 
   The individual parts needed moreover for completion of the cores  1  and  2  are not shown in the drawings, because they are formed in conventional manner. This applies in particular to upper and lower end plates  39  ( FIG. 1 ) and the required connection nipples or collecting tanks. 
   Moreover it follows from  FIGS. 1 and 4  that, in the right part, i.e. in the core assembly  1 , the passages  9  formed from pairs of plates  4 , the bars  5   a ,  5   b ,  7  and  8  and the lamellae  15  alternate with those passages  34  formed from the I profiles  33 , further pairs of plates  4  and the plugs  37 . In the left part however, i.e. in the core assembly  2 , the passages  9  alternate with the passages  21  formed from the same pairs of plates  4 , the bars  18 ,  19 ,  20   a ,  20   b  and the lamellae  25 . How many passages  9 ,  21  and  34  are each present depends on the requirements of the individual case, while in principle one each of the passages  9 ,  21  and  34  suffices to enable the function described with reference to  FIGS. 1  to  3 . 
   According to a second embodiment of the invention shown in  FIG. 9 , the passages  34  ( FIG. 6 ) are not formed from individual I profiles  33  arranged beside each other, with their webs  33   a  forming the side partitions of the individual channels, but from a plurality of rigidly united I profiles  41  arranged one after the other. Webs  41   a  of the profiles  41  form intermediate bottoms while flanges  41   b  having outer surfaces adjoining or merging into each other, form side partitions between channels  42   a  and  42   b  arranged transverse to the longitudinal axis  32  and parallel to one another. As in the embodiment according to  FIGS. 1 and 8  the profiles  41  are offset relative to one another in their longitudinal direction, and the channels  42   a  and  42   b  are connected at their ends on the one and other longitudinal side by diverting sections  43   a  and  43   b  respectively, in meandering or serpentine form the diverting sections  43   a  are bounded on the outside by wall sections  44   a  whereas the diverting sections  43   b  are bounded by wall sections  44   b  which both are connected on each longitudinal side only to each second flange  41   b , while the intervening flanges  41   b  end in front of these wall sections  44   a ,  44   b , for the formation of the diverting sections  43   a ,  43   b , so that the individual partitions are offset from one another by analogy with  FIGS. 1  to  8 , transverse to the longitudinal direction  32  and relative to one another.  FIG. 9  moreover shows that, on account of the special arrangement a plurality of corresponding channels  43   a  and  42   b  result in each case on the two sides of the webs  41   a  or intermediate bottoms, being connected one after the other in terms of flow by the diverting sections  43   a ,  43   b  and forming a passage for the coolant. The channels are covered and closed above and below by the plates  4  by analogy with  FIGS. 1  to  8  (FIG.  10 ), which are connected to the side edges of the flanges  41   b  by soldering. 
   The production of the passages seen in  FIGS. 9 and 10  is effected in accordance with the invention in that a workpiece  45 , e.g. a plane parallel plate, is provided with grooves on its two wide faces, forming the channels  42   a ,  42   b  and diverting sections  43   a ,  43   b . This can be effected in particular by milling, especially track milling, so that the whole passage consisting of channels  42   a ,  42   b  and diverting sections  43   a ,  43   b  is produced in one working step. In this case the flanges  41   b  are obtained as wall sections remaining between the grooves and the webs  41   a  as remaining groove bottoms, where all these bottoms lie in one plane, which forms an intermediate bottom extending over the length and breadth of the workpiece  45 , from which each of the flanges  41   b  extends with a half upwards and with another half downwards respectively. Alternatively it would be possible to form the grooves in only one surface of the workpiece  45 , in which case only an essentially U-shaped profiling would result in a cross-section through the workpiece  45  along the longitudinal axis  32 . The coolant passage could then be thought of as composed of a plurality of adjacent U-shaped profiles, whose side limbs adjoin or merge into one another. In each case the part forming the coolant passage forms a unitary I-shaped or. U-shaped profiled workpiece, which is connected on one or both sides by soldering to the plates  4  in order to close in the channels  42   a ,  42   b  and diverting sections  43 ,  43   b  initially open on the upper and/or lower side. 
   At the places associated with the arrows  28 ,  29  ( FIG. 5 ) the grooves are extended through the wall parts  44   a ,  44   b , as is indicated by a reference numeral  46  in  FIG. 9 , so that collecting chambers or the like, not shown, for the feed and discharge of the coolant can be fitted on their outsides. 
   In order that the soldering can be carried out cost-effectively in a salt bath, as in the embodiment of  FIG. 1 , the wall sections  44   a ,  44   b  are advantageously provided before the soldering operation with slots  47 , which are indicated in broken lines at some places in FIG.  9  and which connect the diverting sections  43   a ,  43   b  with the outside of the wall sections  44   a ,  44   b , i.e. pass through these. Accordingly air and fluids can easily penetrated into the channels  42   a ,  42   b  in the soldering operation, in order to wet the parts to be soldered in the region of the soldering gaps which are foxed, and can also easily flow out of the channels  42   a ,  42   b  after the soldering process. At the end of this the slots  47  are closed by a welding operation. 
   The formation of the core assembly ( FIG. 1 ) described with reference to  FIG. 8  also leads to a high strength construction, which can withstand high burst pressures. 
   The invention is not restricted to the described embodiments, which can be modified in many ways. This applies in particular to the cross-sections shown in the drawings of the I and U profiles, which can have other shapes and can also be provided in combination. The invention is furthermore not limited to the use of aluminium as the material, since numerous other materials suitable for this purpose can be used for the production of the described heat exchanger core assembly. Furthermore it is immaterial in principle whether the cores  1  and  2  form an integral component by use of the continuous plates  4 , are separately produced and then joined together in an integral component or are used as separate components, which are connected together by suitable lines. Moreover it would also be possible to arrange the two cores  1  and  2  one over the another in a manner known per se, instead of alongside each other. Finally it is obvious that the various features can be used in combinations other than those described and illustrated. 
   It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
   While the invention has been illustrated and described as embodied in a heat exchanger core assembly, particularly a coolant/air heat exchanger core assembly, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
   Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.