Heat Exchanger for an Air Heating Device and Method for Producing a Heat Exchanger
The invention relates to a heat exchanger (10) for an air heating apparatus (12) for integration into a housing which guides air. The heat exchanger has a heat exchanger body (14) with a longitudinal axis. According to the invention, the heat exchanger body (14) has on its external surface (external side) a plurality of undular ribs (28) which extend essentially along its circumferential dimension, which ribs provide heat transfer surfaces.
The invention relates to a heat exchanger for an air heating apparatus for integration into a housing which guides air. The heat exchanger has a heat exchanger body which has a longitudinal axis.
The invention also relates to various methods of fabricating a heat exchanger for an air heating apparatus for integration into an air-guiding housing, particularly a housing of a heating and air conditioning system of a motor vehicle, wherewith the heat exchanger has a heat exchanger body which has a heat exchanger core which has a longitudinal axis, and said heat exchanger has heat transfer surfaces.
Currently, fuel-driven supplemental heating units for vehicles (particularly trucks or utility vehicles the like) are generally housed separately from the vehicle's inherent onboard heating and air conditioning unit. Such supplemental heating units are provided in the form of, e.g., air heating apparatuses, which are utilized as heaters to provide supplemental heating, and/or to provide heating under stationary circumstances (when the vehicle is parked).
For some time, attempts have been made to integrate air heating devices into the inherent onboard heating and air conditioning apparatus of a vehicle. This would provide savings in space occupied and in component parts (avoids redundancy). An example of such an apparatus is disclosed in DE 10211591 A1.
The quality of the functioning and the economic efficiency of the air heating apparatus, and the safety and reliability of the combination, depend substantially on the location of the apparatus integrated into the inherent onboard heating and air conditioning system, and on the engineering design and construction characteristics of said air heating apparatus. It is important to fully take into account the set of problems associated with the integration of the air heating apparatus into the system of the inherent onboard heating and air conditioning system, and to provide solutions for these problems, in order to achieve a successful integrated system.
Some of the engineering problems concern means of minimizing the ordinarily high weight of the heat exchanger body. Such heat exchanger bodies are customarily fabricated by pressure casting. The greater the weight of the heat exchanger body, the more robust the housing in which it is mounted on the vehicle must be.
Under the design schemes according to the state of the art, air is caused to flow around the heat exchanger in a direction which is perpendicular to the longitudinal direction (axial direction) of the heat exchanger. Such transverse flow results in high creation of vortices and turbulent flow of the air, and thus high energy losses in the flow (high flow pressure drop). If one seeks to address this by increasing the space available around the heat exchanger, one will need more installation space to accommodate the integrated heating and air conditioning system. Accordingly, it is rational to seek solutions which improve the flow behavior and heat transfer with regard to the heat exchanger.
It is also desirable to utilize already present components of the air heating apparatus in the solution by which said apparatus is integrated into the inherent onboard heating and air conditioning system. Accordingly, the heat exchanger employed should have an adaptable design, so as to be utilizable with a variety of types and models of air heating apparatuses. The means of fabrication of the heat exchanger should be similarly adaptable.
There are two heat transfer processes—that from the heat exchanger to the air sought to be heated, which air flows around the exterior of the heat exchanger, and that from the combustion gases to the heat exchanger. By improving the latter heat transfer, one can have greater freedom of design of the structure of the heat exchanger as a whole.
Another important requirement placed on the air heating apparatus is that it be configured so as to avoid any possible penetration of combustion gases into the air which flows around the air heating apparatus. Another requirement is to provide means whereby the combustion air used for the combustion is drawn in from the space outside the motor vehicle, and in particular not from the interior space of the vehicle. Thus it would be advantageous to provide improvements in the arrangement of the various connecting fittings and nipples employed with known air heating apparatuses.
The underlying problem of the present invention was to devise appropriate solutions to solve the above-described problems at least partially, particularly the problems concerning flow behavior and heat transfer.
This underlying problem is solved by the features of the independent claims.
Advantageous embodiments of the invention are set forth in the dependent claims.
According to the invention, improvements are provided in the general type of heat exchanger in that the heat exchanger body has on its external surface (external side) a plurality of undular ribs which extend essentially along its circumferential dimension, which ribs provide heat transfer surfaces. The undular shape of the ribs improves the heat transfer to the air which is to be heated, which air flows through the spaces between the ribs; conceptually this improvement results from increasing of the surface area available for this heat transfer. The undular shape of the ribs also confers stability.
In this connection, it is possible that the heat exchanger body is provided with a heat exchanger core, and that the plurality of undular ribs are at least to some extent applied to the heat exchanger core via separate component parts or as separate components. This possible separate fabrication is advantageous in providing means of reducing the weight and providing variability and versatility in the design of component parts and in the fabrication methods.
Alternatively, the heat exchanger body is provided with a heat exchanger core, wherewith the plurality of undular ribs are at least to some extent integrally formed with said heat exchanger core.
It is advantageous if the plurality of undular ribs are applied to the heat exchanger core by shrink-forming and/or press forming methods. It is desirable to avoid achieving fastening of such heat transfer surface elements to the heat transfer core by screw fastening or the like; more desirable means of fastening heat transfer surface elements (after said elements have been slid over the core) are welding, brazing, shrink-forming, or press forming, wherewith said elements are applied individually or in groups, or in subassemblies comprised of such elements.
According to the invention, improvements are provided in the general type of fabrication process, in that the heat exchanger body has on its external surface (external side) a plurality of undular ribs which extend essentially along its circumferential dimension, which ribs provide heat transfer surfaces, wherewith the heat exchanger core and the undular ribs are at least to some extent separately fabricated. In this way, an advantageous method is provided for realizing the advantages and features of the inventive heat exchanger.
In the inventive method, the plurality of undular ribs may be applied to the heat exchanger core by shrink-forming and/or press-forming methods. The heat exchanger head and heat exchanger base are preferably joined to the heat exchanger core, in gastight joints, by means of welding, brazing, adhesive bonding, and/or screw means; but, for the individual heat transfer elements, which may be applicable initially as sliding elements, the possibility of fixing them by shrink-forming and/or press-forming contributes variability and flexibility in the fabrication process.
The inventive method further improves upon the general type of fabrication process in that the heat exchanger body has on its external surface (external side) a plurality of undular ribs which extend essentially along its circumferential dimension, which ribs provide heat transfer surfaces, wherewith the heat exchanger core and the undular ribs are fabricated so as to have together a unit construction.
The features relating to the configurations of the heat transfer surfaces can be combined with numerous features of the heat exchanger, of air heating apparatuses employing the heat exchanger, and of fabrication methods for heat exchangers, to give rise to advantageous characteristics.
. . . It may be provided that the body of the heat exchanger and the base of the heat exchanger are fabricated separately. This affords flexibility with regard to the various possible structures and configurations, and the various possible fabrication methods. If the heat exchanger base is fabricated separately from the heat exchanger core, variants in fabrication methods and steps for the heat exchanger core may be introduced. The overall weight of the heat exchanger can be reduced by the appropriate choice of fabrication methods.
For similar reasons, it may be advantageous to fabricate the heat exchanger head separately. In particular, such a heat exchanger head may be already available; wherewith separate fabrication is a beneficial choice. Depending on the geometric form of the burner head or of the burner unit, it may even be possible to completely eliminate a heat exchanger head.
It is possible to fabricate the heat exchanger core by pressure casting. In general, such cast parts are somewhat heavy; however, cost savings are achieved.
It is possible to provide the heat exchanger core with an interior profile. This is a means of increasing the interior heat transfer surface area of the heat exchanger, and of decreasing the overall installation space required.
The heat exchanger core may be manufactured by extrusion. Extrusion generally allows for thinner walls in the heat exchanger compared to a core fabricated by pressure casting, in particular since extrusion does not require the configuration to include a mold removal incline; accordingly, reductions in overall weight can be achieved, as well as thinner features (vanes etc.) in the interior profile, and thereby increased heat transfer surface area of the interior surfaces. An extrusion process makes it possible to incorporate geometric features which facilitate attachment of the heat exchanger head, burner, heat exchanger base, etc., e.g. in the form of holes in the core which may be threaded.
It may be provided that the heat exchanger core has a cross sectional geometry which tends to reduce flow resistance.
For example, the cross sectional geometry may be oval or ovaloid.
Alternatively, the cross sectional geometry may resemble that of an airfoil.
Alternatively, it may be advantageous if the cross sectional geometry is generally diamond-shaped.
The heat exchanger body may have a plurality of rods on its exterior surface, which rods provide heat transfer surface. This configuration can contribute a very large surface area for heat transfer to the air which is to be heated.
It may be advantageous for the heat exchanger body to have a heat exchanger core, and for the above-described plurality of rods to be applied to said core at least partially by means of a separate component part (or parts).
The heat exchanger body may have a heat exchanger core wherewith at least part of (some of) the plurality of rods have a unit construction with the heat exchanger core. The provision of the rods on one or more separate component parts, on the one hand, and direct fixing of the rods to the core (in a unit construction or the like), on the other hand, each has its own advantages; e.g. the use of separate component parts provides design flexibility, whereas direct fixing (e.g. unit construction) allows a simple fabrication method.
The heat exchanger body may be comprised of a plurality of heat exchanger body modules.
This arrangement provides variability, as to the configuration and size of the heat exchanger.
It may be particularly advantageous to fabricate the heat exchanger body modules by pressure casting. If it is desired to use a fully customary pressure casting process, modular construction is desirable, because the mold-removal inclines required are short and thereby minimally intrusive.
Regarding modular construction, it may be advantageous if the heat exchanger body modules are at least to some extent identical. This allows for identical tool components, e.g. in the case of pressure molding.
To some extent, at least, the heat exchanger body may be fabricated from two molded pieces in a pressure molding process, wherewith the two pieces are removed from the mold in opposite directions. This is another means of reducing the maximum lateral extent of the mold removal inclines and thereby reducing overall weight.
In connection with an air heating apparatus for integration into an air guiding housing, which heating apparatus has a heat exchanger with a heat exchanger body, the air heating apparatus may be provided with flow-guiding elements wherewith, when combustion is carried out in a combustion space which is at least partly disposed in the interior of the heat exchanger, hot gases which are generated are deflected toward the interior side of the heat exchanger body. In this way, the hot gases produced in the combustion can be more efficiently distributed over the interior side of the heat exchanger.
In this connection it is advantageous if the flow guiding elements are in the form of a helical vane, systems of vanes or the like (which may employ undular geometries or the like), baffle plates, and/or perforated tubes. These and numerous other possibilities improve overall heat transfer.
In the case of an air heating apparatus for integration into an air guiding housing, which apparatus has a heat exchanger, it may be advantageous if the apparatus has a flange plate which provides a seal of the exhaust gas withdrawal means, by means of sealing elements between a mounting location for the air heating apparatus and the flange plate, and between the air heating apparatus and the flange plate, which seal at least prevents penetration of exhaust gases into the interior space of the vehicle. Such a flange plate provides means of minimizing the path of the exhaust gases to the external air, and in so doing makes it less likely that penetration will occur.
In this connection it is further useful that the flange plate provides seal means between the combustion air feed passage and the interior space of the vehicle. This provides assurance that the combustion air will be drawn from outside the vehicle.
It is also advantageous if the flange plate has a pass-through opening for fuel supply. In this way, all fittings and nipples through which gases and liquids are passed are disposed in the region of the flange plate, which is advantageous for integrating the air heating apparatus into the entire system design.
It is an underlying concept of the invention that an air heating apparatus can be integrated into an onboard heating and air conditioning system of a vehicle (particularly a truck or utility vehicle) in an economical and functionally advantageous manner. In implementation of this concept, a heat exchanger has been devised according to the invention which has high variability and adaptability, and has advantageous weight, flow, and heat transfer characteristics.
The invention will now be explained further based on particularly preferred exemplary embodiments, with reference to the accompanying drawings.
In the description of the drawings which follows hereinbelow, like or similar components have been assigned like reference numerals.
The features of the invention disclosed in the preceding description, the drawings, and the claims may be essential elements of the invention individually or in any combination.
LIST OF REFERENCE NUMERALS
- 10 heat exchanger.
- 12 air heating apparatus.
- 14 heat exchanger body.
- 16 heat exchanger base.
- 18 heat exchanger head.
- 20 heat exchanger core.
- 22 heat transfer surface.
- 24 component parts having heat transfer surfaces (disc-shaped).
- 26 component parts having heat transfer surfaces (rod-shaped).
- 28 component parts having heat transfer surfaces (undular ribs).
- 30 interior profile [(FIGS. 5, 7); generally diamond-shaped external profile (
FIG. 9 )]. - 32 oval (or ovaloid) cross sectional geometry.
- 34 airfoil-shaped (lobe-shaped) cross sectional geometry.
- 36 generally diamond-shaped [lit., “shaft-shaped”] cross sectional geometry.
- 38 heat exchanger body module.
- 40 mold removal direction.
- 42 mold removal direction.
- 44 screw thread.
- 46 hole in perforated tube.
- 48 flange plate.
- 54 exhaust gas removal [nipple].
- 56 combustion air supply line.
- 58 fuel supply line.
- 60 burner unit.
- 62 burner head.
- [(End of reference numeral list supplied for translation.)]
Claims
1. A heat exchanger (10) for an air heating apparatus (12) for integration into an air-guiding housing, which heat exchanger has a heat exchanger body (14) with a longitudinal axis; characterized in that the heat exchanger body (14) has on its external surface (external side) a plurality of undular ribs (28) which extend essentially along its circumferential dimension, which ribs provide heat transfer surfaces.
2. A heat exchanger (10) according to claim 1; characterized in that the heat exchanger body (14) has a heat exchanger core (20);
- and in that the plurality of undular ribs (28) are at least to some extent integrally formed with the heat exchanger core (20).
3. A heat exchanger (10) according to claim 1; characterized in that the heat exchanger body (14) has a heat exchanger core (20);
- and in that
- the plurality of undular ribs (28) are at least to some extent applied to the heat exchanger core (20) via separate component parts or as separate components.
4. A heat exchanger (10) according to claim 3; characterized in that the plurality of undular ribs (28) are applied to the heat exchanger core by shrink-forming and/or press-forming methods.
5. A method of fabricating a heat exchanger (10) for an air heating apparatus (12) to be integrated into an air-guiding housing, particularly a housing of an onboard heating and air conditioning system of a motor vehicle, wherewith the heat exchanger has a heat exchanger body (14) which has a heat exchanger core (20) which has a longitudinal axis, and said heat exchanger has heat transfer surfaces; characterized in that the heat exchanger body (14) has on its external surface (external side) a plurality of undular ribs (28) which extend essentially along its circumferential dimension, which ribs provide heat transfer surfaces, wherewith the heat exchanger core (20) and the undular ribs are at least to some extent separately fabricated.
6. A method according to claim 5; characterized in that the plurality of undular ribs (28) are applied to the heat exchanger core by shrink-forming and/or press-forming methods.
7. A method of fabricating a heat exchanger (10) for an air heating apparatus (12) to be integrated into an air-guiding housing, particularly a housing of an onboard heating and air conditioning system of a motor vehicle, wherewith the heat exchanger has a heat exchanger body (14) which has a heat exchanger core (20) which has a longitudinal axis, and said heat exchanger has heat transfer surfaces; characterized in that
- the heat exchanger body (14) has on its external surface (external side) a plurality of undular ribs (28) which extend essentially along its circumferential dimension, which ribs provide heat transfer surfaces, wherewith the heat exchanger core (20) and the undular ribs are fabricated so as to have together a unit construction.
Type: Application
Filed: Nov 23, 2005
Publication Date: Apr 24, 2008
Inventor: Andreas Ludwig (Penzberg)
Application Number: 11/720,260
International Classification: F28F 1/42 (20060101); B21D 53/06 (20060101);