The invention relates to a heat exchanger with which fluids can be very rapidly and uniformly cooled or heated.
Heat exchangers are required in numerous industrial applications. Here, the trend is increasing towards ever higher heat transfer performance in the smallest possible space. These requirements are met particularly well by micro heat exchangers. In process technology, it is moreover desirable for very uniform heat transfer to take place, that is, to avoid so-called hot spots arising which could result in product damage due to an uncontrolled temperature increase.
A microstructure heat exchanger made up of small pipes or hollow fibres located in a graphite matrix is known from DE 100 22 972 A1.
Further, micro heat exchangers are constructed of multi-ply microstructured layers, wherein the individual layers each have a number of microchannels. The layers are arranged such that the microchannels of adjacent layers are aligned in simple cross-flow construction, parallel flow construction or counter flow construction. Such a micro heat exchanger is known from DE 196 08 824 A1.
Counter flow heat exchangers achieve the highest heat exchange performance per exchange surface. However, the possibility cannot be excluded that inadmissibly high temperature differences occur at the inlet of the warmer fluid, leading to damaged heating fluid.
In the parallel flow heat exchanger, on the other hand, the wall temperatures remain in a middle range at all positions on the heating surface. However, due to the rapidly decreasing temperature difference between the adjacent fluids, the heat exchange performance is relatively poor.
In simple cross flow heat exchangers for micro heat exchangers as currently known, the heat exchange performance is between that of the parallel flow heat exchanger and the counter flow heat exchanger. However, the full heat exchange surface is not used efficiently here, as the temperature differences in a quadrant of the heat exchange surface become extremely small or cease to exist.
Further, known micro heat exchangers have either insufficient or no heat insulation from the surrounding ambient, which has a particularly disadvantageous effect on modular micro reaction systems, as known for example from DE 202 01 753 U1, as it results in very intensive heat exchange with adjacent modules.
The invention is based on the object of providing the highest possible heat transfer performance, that is, a large heat transfer surface, while achieving extremely small pressure loss both for the process fluid and for the heat transfer fluid.
According to the invention, this is achieved in that the heat exchanger is constructed from a stack of films or plates in which channels for the fluids are embodied each lying adjacent one another, wherein the channels of the films or plates lying over one another intersect. Here, the heat transfer fluid flows into the channels of a film or plate lying adjacent one another in antiparallel branch flows, while in the film or plate lying thereabove and therebelow, the process fluid flows transverse to the heat transfer fluid and parallel in the channels lying adjacent one another. Due to the linear channelling in each case, the pressure loss in the heat exchanger is minimized.
At each crossing point of heat transfer fluid and process fluid, for each branch flow of the process fluid over the whole volume of the heat exchanger, the device according to the invention leads to the inlet conditions of a counter flow heat exchanger having the known high temperature differences between heat transfer fluid and process fluid. Due to the numerous crossing points of heat transfer fluid and process fluid, an optimum temperature difference between heat transfer fluid and process fluid and thus an extremely high heat transfer performance per unit of volume and simultaneously absolutely uniform heat transfer over the whole volume of the heat exchanger, is hereby obtained over the whole volume of the heat exchanger.
The present invention combines the advantages of a counter flow heat exchanger with the advantages of a cross flow heat exchanger.
An exemplary embodiment of the invention is explained in more detail below with reference to the drawing, in which
FIG. 1 shows a schematic cross section through a stack of films,
FIG. 2 shows a section along the line A-A in FIG. 1,
FIG. 3 shows a section along the line C-C in FIG. 1 and FIG. 2,
FIG. 4 shows a section along the line B-B in FIG. 1,
FIG. 5 schematically shows the flow pattern in two plies of flow channels lying over one another,
FIG. 6 shows a schematic perspective view of the arrangement of channels and pipes of the heat exchanger,
FIG. 7 shows an exploded view of distributor plates,
FIG. 8 shows a housing with a micro heat exchanger from a stack of films in a perspective cut-away representation, and
FIG. 9 schematically shows an arrangement of a plurality of heat exchanger units according to FIG. 6, which form a heat exchanger of greater capacity.
FIGS. 1 to 4 schematically show the construction of a micro heat exchanger 1, wherein FIG. 1 represents a stack of films or thin plates F as indicated by dashed lines in FIG. 1. In the individual films or plates, channels and throughholes are embodied, wherein the channels extending horizontally can be embodied in a film F for example by recesses which are covered by the surfaces of adjacent film F, so that a closed channel results. In the embodiment according to FIG. 1, the lowest film of the stack of films is merely shown as a cover film for the bottom row of channels 3. However, another shape of channel formation in the individual films or plates F is also possible, for example in that a division extends between two adjacent films F in each case along the middle of the horizontally extending channels 2 and 3.
FIG. 1 shows as an example a flow pattern in which a process fluid P flows through the channels 2 and a heat transfer fluid W flows through the channels 3 extending transversely thereto. The channels 3 lie adjacent one another in a film F and form a row 30 of channels in each second film F. In the same way, the channels 2 for the process fluid P are each formed lying adjacent one another in a row 20, as FIG. 2 shows, which represents a section along the line A-A in FIG. 1. The process fluid P flows parallel through the adjacent channels 2 in each case, while the heat transfer fluid W flows antiparallel in two branch flows W1 and W2 through the adjacent channels 3, as the flow pattern in FIG. 5 shows schematically. The antiparallel flow of the branch flows of the heat transfer fluid can also be seen in FIG. 4, which represents a section along the line B-B in FIG. 1, wherein FIG. 4 only represents a partial sectional view, and the upper and lower edge areas of the heat exchanger unit 1 are not represented.
The supplying of the heat transfer fluid W takes place via throughholes 4 in the films F, which in FIG. 2 form a pipe 4 from bottom to top, extending transverse to the horizontally extending channels 2 and 3 at an angle of approximately 90°. The discharging of the heat transfer fluid W takes place on the opposite side through a pipe 4a, which is embodied by corresponding throughholes in the films F lying over one another and likewise extends in the plane of the drawing of FIG. 2 from top to bottom or vice versa, transverse to each of the channels 2 and 3. The adjacent channels 3 in FIG. 2, through which the branch flows W2 flow from right to left, are fed by a pipe formed by throughholes 5, which lies before and behind the pipe 4a. The discharging of the branch flows W2 takes place through pipes 5a before and behind the pipe 4 in FIG. 2, as can also be seen from FIG. 6.
FIG. 1 shows pipes 7 and 8, embodied in the same way by throughholes, on the opposite sides of the intersecting channels 2 and 3, wherein in the embodiment shown the process fluid P is supplied from above through pipe 7 and discharged through pipe 8.
To clarify the course of flow, in FIGS. 1 to 4 the direction of flow away from the observer is represented by an X and the direction of flow towards the observer by a dot.
FIG. 5 schematically shows the flow pattern in the core portion of the heat exchanger with intersecting channels 2 and 3, wherein the heat transfer fluid W is represented in the first upper row 30 of channels 3 in FIG. 1 and the process fluid P in the row 20 of channels 2 therebelow in FIG. 1, without the channels themselves being represented. FIG. 5 therefore only shows by means of arrows the flow in the core portion of the heat exchanger, wherein the process fluid P flows parallel through each of the channels 2 arranged in rows, and the heat transfer fluid W flows transverse thereto in antiparallel flow to the branch flows W1 and W2 in each case.
FIG. 6 shows in a schematic perspective view a heat exchanger unit 1. The core of the heat exchanger is formed by the intersecting channels 2 and 3, which are each arranged in rows 20 and 30, wherein the heat transfer fluid W is guided antiparallel or in counter flow in adjacent channels 3, while the process fluid P flows in parallel flow through the adjacent channels 2. The supply and discharge of fluid takes place in each case on the outsides of the block-shaped arrangement of the intersecting channels 2, 3 through pipes embodied by the throughholes 4, 5 and 7, 8 in the films F. Thus the heat exchange takes place in the inner block of intersecting channels 2, 3, while the supply and discharge pipes 4, 5 and 7, 8 are arranged on the outside of the block.
In FIG. 6, the pipes 6 on opposite outsides of the heat exchanger 1 represented in FIGS. 1 and 3 are not shown.
If, in an alternative embodiment, the micro heat exchanger 1 is used for cooling a process fluid P, then the heat transfer fluid W at first flows through throughholes 6, embodied in FIG. 1 on the outside of the supply and discharge pipes 7 and 8 for the process fluid P, so that efficient heat insulation of the warm process fluid P in channels 7 and 8 in relation to the surrounding ambient is achieved through these pipes 6 with cold heat transfer fluid W. Following this, through a conduit (not shown) on the upper and lower side in FIG. 1, the heat transfer fluid W is supplied via the throughholes 4 to the channels 3 extending out of the plane of the drawing in FIG. 2, whereupon the heat transfer fluid emerges via the pipes embodied by the throughholes 8. In this embodiment, the block of intersecting channels 2 and 3 is insulated from the surrounding ambient on the four outsides in each case by a row of pipes 6, wherein in FIG. 1 only two outsides are represented. The outsides of the heat exchanger core lying at the top and bottom in FIGS. 1 and 2 are also formed by rows 30 of channels 3, through which heat transfer fluid W flows. In this way, the cooling process fluid P in the channels 2, 7 and 8 is effectively protected from the surrounding ambient.
When the micro heat exchanger 1 is used for heating a process fluid P or as an evaporator, then the supply pipes of the heat transfer fluid W and of the process fluid P can be exchanged, so that in this case too, the cooler fluid flows into the outer pipes 6, 7 and 8, so that heat insulation from the surrounding ambient is provided. Hereby, the design is selected such that cooler fluid likewise flows through the rows 30 of channels arranged on the outsides.
The described construction allows a plurality of adaptations, by changing the number of films F and of channels 2, 3 and adapting it to the flow rates desired in each case. By enlarging the stack of films or thin plates F, the capacity of the micro heat exchanger 1 can be corresponding enlarged.
It is also possible to have both the process fluid P and the heat transfer fluid W flow antiparallel through the respective rows 20, 30 of channels 2, 3. Likewise, it can be advantageous only to have the process fluid P flow antiparallel or in counter flow through the adjacent channels 2, while the heat transfer fluid W flows transverse thereto in one direction in the channels 3.
The channels 2, 3 and the pipes 4 to 8 can be embodied such that they have the same cross section for their whole length. Hereby, a minimum pressure loss occurs during throughflow through the heat exchanger. However, it is also possible to embody the pipes 4 to 8 with a larger cross section than the channels 2 and 3.
FIG. 8 schematically shows a stack of films FS in a housing 100 in which pipes are embodied for the supply and discharge of process fluid P and heat transfer fluid W. As shown, the housing 100 is constructed as a module which can be combined with other modules for the treatment of a process fluid P. However, the heat exchanger 1 described by means of FIGS. 1 to 4 can also be used without a housing 100, wherein in FIG. 1 on the upper and lower side in each case a conduit device is provided which has the connections for the pipes 4, 5, 6, 7 and 8.
FIG. 7 shows in an embodiment distributor plates or films F1 to F3 in an exploded view, which represents the supplying of the heat transfer fluid W from the lower side of a stack of films and the distribution into branch flows W1 and W2. In the lowest film F1, a throughhole 10 is formed through which the heat transfer fluid W is supplied. From the throughhole 10, a channel 10a extends in the film plane, which branches into two channels 10b, which in turn branch into two channels 10c and so forth, until on the right-hand side in FIG. 7 the number of pipes 10e is available which is required for the supplying of the channels 3 of a row 30 for the heat transfer fluid in the core portion of the heat exchanger. In the film F2 lying thereabove, throughholes 5 are embodied in a row, which lie opposite the ends of the individual pipes 10e, so that the heat transfer fluid W, as indicated by dashed lines, can flow upward through the throughholes 5. In film F2, at alternate throughholes 5 a pipe 11 is formed branching off, which leads in the film plane to the opposite side of the core portion of the heat exchanger unit 1. In the film F3 lying thereabove, a row of throughholes 4 is embodied which lie opposite the ends of the pipes 11, so that a branch flow W1 of the heat transfer fluid can flow upwards through the throughholes 4. The opposite row of throughholes 5 in the film F3 lies opposite the holes 5 in the film F2, from which no pipes 11 branch off, so that a branch flow W2 flows upwards through the throughholes 5.
Above the film F3, a channel arrangement corresponding to FIG. 4 can be embodied in the next film plane, in which the two branch flows W1 and W2 flow in counter flow through the channels 3. To simplify the representation, in the films F1 to F3 the return pipes 4a and 5a are not shown. They can be embodied by corresponding throughholes in the films, wherein corresponding to the films F1 and F2, the returning heat transfer fluid W is collected and discharged through a common outlet corresponding to the throughhole 10.
The supplying of the process fluid P in the embodiment shown takes place from above by an arrangement of distributor plates corresponding to that in FIG. 7, wherein the lowest plate F1 in FIG. 7 forms the uppermost plate for the guiding of the process fluid. As the process fluid P flows in parallel flow through the channels 2, it is not necessary to provide a distributor plate corresponding to the distributor plate F2. Rather, at the uppermost film corresponding to the film F1, a film with throughholes corresponding to film F3 can be joined, in which rows of throughholes 7 and 8 are embodied, instead of the row of throughholes 4 and 5 shown in FIG. 7.
In the representation in FIG. 7, to simplify the representation, the pipes 6 lying outside in FIGS. 1 and 3 are not shown, which are also embodied by throughholes in the individual films F.
In FIG. 7, the films F1 to F3 are shown discoidally, while in FIGS. 1 to 4 and 6, in each case only one block-shaped arrangement of channels 2, 3 and pipes 4 to 8 is represented. In the same way, the channels and pipes shown in these Figures can be embodied in discoidal films, so that a round stack FS of films F results, as shown in FIG. 8.
In the heat exchanger shown in FIG. 8, the heat transfer fluid W is supplied from below and discharged from above, so that any air contained in the heat exchanger is displaced out upwards. The process fluid can be supplied from above and discharged on the lower side. However, another flow direction of the fluids P and W is also possible. For example, the heat transfer fluid W can be supplied from above and also discharged from above, while the process fluid P is supplied from below and discharged from below.
FIG. 9 schematically shows an arrangement of individual heat exchanger units 1, of which one is shown in FIG. 6. For very great heat transfer performance or large fluid flows, a plurality of such heat exchanger units 1 can be arranged adjacent and over one another, as FIG. 9 shows, wherein above a lower ply of heat exchanger units la a further ply of heat exchanger units 1b and 1c is arranged. Hereby, the heat transfer performance can be multiplied without substantially increasing the overall pressure loss, in that the individual heat exchanger units 1 are fed fluidically in a parallel manner. In other words, each individual heat exchanger unit 1 can be supplied with fluid by means of distributor plates corresponding to FIG. 7, wherein the different distributor plates can be supplied with fluid centrally by an additional distributor plate. Between the individual plies of heat exchanger units 1a, 1b and 1c, distributor plates can be provided in which throughholes are embodied for forming pipes leading vertically upwards between the heat exchanger units 1a, through which pipes the heat exchanger units 1b and 1c are supplied with the fluids W or P. In the same way, distributor plates can be provided on the upper side of the block of a plurality of heat exchanger units.
According to a simpler embodiment, for increasing the heat transfer performance only one group of heat exchanger units 1a can be supplied parallel, which corresponds to the lower ply in FIG. 9. In such an embodiment, additionally to the distributor plates shown on the upper and lower side in FIG. 7, a further distributor plate can be provided from which the individual throughholes 10 are supplied with fluid, wherein this additional distributor plate has a central fluid supply from which channels lead off to the individual throughholes 10 of the individual heat exchanger units 1a, corresponding to the film F1 shown in FIG. 7.
To determine the temperature of the fluids, advantageously temperature sensors can be integrated directly adjacent the microstructured films or thin plates.
The term fluid or process fluid is to be understood broadly according to the invention and comprises liquids and gases as well as emulsions, dispersions and aerosols. The device can be used both for cooling and for heating.
Microstructured channels means structures which are smaller than 1 mm in at least one spatial dimension. The walls between the microstructured channels are preferably between 10 μm and 500 μm thick.
Advantageously, the films or thin plates with which the micro heat exchangers are joined together, are composed of sufficient inert material, preferably metals, semiconductors, alloys, high-quality steels, composite materials, glass, quartz glass, ceramic or polymer materials, or of combinations of these materials.
Methods which can be considered as suitable for fluidically leak-proof joining of the films or thin plates are for example pressing, riveting, bonding, soldering, welding, diffusion soldering, diffusion welding, and anodic or eutectic bonding.
The structuring of the films or thin plates can take place for example by milling, laser ablation, etching, the LIGA method, galvanic casting, sintering, die-cutting or deformation.
For the relevant person skilled in the art, it can easily be understood that the device can be used not only as a micro heat exchanger but that, for example, an application as an evaporator or condenser of a combination thereof (rectification) is also possible.
Further, the construction of a heat exchanger according to the invention is not only suitable for micro construction. It can also be used for larger-dimensioned heat exchangers. These can be constructed for example, from thicker plates in which channels are stamped, milled or imprinted and bores are embodied instead of throughholes. Such structures can also be formed on the plates by spark erosion.
The material of the plates or films F preferably consists of inert material or material which is sufficiently inert in relation to the fluids used.
Patent Application
20080190594
