Heat Exchanger for an Air Heating Device
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 longitudinal axis, wherewith air can be forcibly caused to flow around the heat exchanger in a “main flow direction” which is essentially perpendicular to said longitudinal axis. According to the invention, the heat exchanger has a cross sectional geometry [sic] perpendicular to the “main flow direction” which geometry is flattened with respect to a circular cross sectional geometry (32, 34, 36).
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 longitudinal axis, wherewith air can be forcibly caused to flow around the heat exchanger in a “main flow direction” which is essentially perpendicular to said longitudinal axis.
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.
This underlying problem is solved by the features of the independent claim.
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 has a cross sectional geometry [sic] perpendicular to the “main flow direction” which geometry is flattened with respect to a circular cross sectional geometry. Such a flattened cross sectional geometry reduces flow resistance.
A flattened cross sectional geometry according to the invention may be, e.g., 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 specifics of the cross sectional geometry can be combined with numerous other features of the heat exchanger, of the air heating apparatus which is to incorporate the heat exchanger, and of the fabrication processes for the heat exchanger, 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.
According to another preferred embodiment of the invention, the heat exchanger body has a heat exchanger core and heat transfer surfaces, and the heat exchanger core and the component parts which provide the heat transfer surfaces, are at least partially separately fabricated. These possible separate fabrication processes are advantageous as means of weight reduction and means of providing increased variability with regard to the configuration of component parts and with regard to fabrication methods.
In this connection it is particularly useful if the component parts which provide the heat transfer surfaces are applied to the heat exchanger core by press-forming or by a shrink-forming method. In order to join the heat exchanger head and the heat exchanger base to the heat exchanger core with gas-tight joints, preferably welding, brazing, adhesive bonding, and/or screwing (or screw fastening) are employed. There may be, e.g., heat transfer surfaces [sic] of the heat exchanger which generally have a disc-like or flange-like shape, wherewith press-forming or shrink-forming may be advantageous for fixing them to the heat exchanger core. In this way, one has additional opportunities for variability of the fabrication methods.
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.
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 have a plurality of undular ribs on its exterior surface, which ribs contribute heat transfer surface area.
In this connection, it is possible that the heat exchanger body has a heat exchanger core wherewith the plurality of undular ribs are applied to the heat exchanger core via a separate component part or as individual separate parts.
In a configuration in which the heat exchanger body has a heat exchanger core, the plurality of undular ribs may be at least partly (e.g. at least some of them may be) fabricated in a unit construction with the heat exchanger core. It is advantageous if the means of fastening such heat transfer surfaces are not screw means or the like
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.)]
- [(Note that reference numeral 74 has a different meaning in
FIG. 6 than inFIG. 3 ; and that reference numeral 76 has a different meaning inFIG. 7 than inFIG. 3 .)]
Claims
1. A heat exchanger (10) for an air heating apparatus (12) for integration into an air-guiding housing, which heat exchanger has a longitudinal axis, wherewith air can be forcibly caused to flow around the heat exchanger in a “main flow direction” which is essentially perpendicular to said longitudinal axis; characterized in that the heat exchanger has a cross sectional geometry [in a cross sectional plane] perpendicular to the “main flow direction” which geometry is flattened with respect to a circular cross sectional geometry (32, 34, 36).
2. A heat exchanger (10) according to claim 1; characterized in that the cross sectional geometry (32) is oval or ovaloid.
3. A heat exchanger (10) according to claim 1; characterized in that the cross sectional geometry (34) is similar to the cross sectional shape of an airfoil.
4. A heat exchanger (10) according to claim 1; characterized in that the cross sectional geometry (36) resembles a diamond shape.
Type: Application
Filed: Nov 23, 2005
Publication Date: Jan 24, 2008
Inventor: Andreas Ludwig (Penzberg)
Application Number: 11/720,255
International Classification: F28F 7/00 (20060101);