Abstract:
A device for electrically heating a fluid, in particular for use in an electrically operated motor vehicle, comprising an induction coil, which is integrated in an oscillating circuit and produces an alternating magnetic field, and at least one first inductor, which is positioned within the alternating magnetic field. The inductor can be arranged inside a module, through which a fluid to be heated can flow, and the induction coil is arranged outside the module.

Description:
[0001]    This nonprovisional application is a continuation of International Application No. PCT/EP2013/057681, which was filed on Apr. 12, 2013, and which claims priority to German Patent Application No. 10 2012 206 603.9, which was filed in Germany on Apr. 20, 2012, and which are both herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a device for electrically heating a fluid, particularly for use in an electrically operated motor vehicle, the device has an induction coil, which is integrated in an oscillating circuit and generates an alternating magnetic field, and at least one first inductor, which is positioned within the alternating magnetic field. 
         [0004]    2. Description of the Background Art 
         [0005]    Today, vehicles operated with internal combustion engines are mostly heated by heating a fluid, which is usually a water/glycol mixture. The fluid that is intended first and foremost for cooling the internal combustion engine is passed through a water to air heat exchanger after it has taken up the heat of the internal combustion engine. The air, which as a cooling fluid flows around the water to air heat exchanger, hereby takes up the thermal energy from the cooling fluid. The cooling fluid is cooled in this way and the air is heated. The heated air is then conveyed into the interior of the vehicle and thereby used for controlling the temperature in the interior. 
         [0006]    In vehicles without an internal combustion engine or in high-efficiency diesel engines, there is no waste heat from the engine or it is not sufficient to adequately heat the vehicle cabin according to the driver&#39;s wishes. To circumvent this, electrical heaters are being used currently to convert electrical energy into heat. There are essentially two alternatives here. In the first alternative, the air flowing in the interior is heated directly by an electrical auxiliary heater. Such implementations are known, for instance, from EP 1 935 684 A1. 
         [0007]    For this purpose, the auxiliary heater is positioned in a region of the interior air intake such that before the air is conveyed into the interior it comes into contact with the electrical auxiliary heater and thus takes up heat. The auxiliary heaters are often installed directly in the vicinity of or on the heat exchanger itself that is provided for heating the air stream by means of the heated cooling water from the combustion engine. This creates an additional parts cost and, moreover, the typically used PTC ceramic elements are rather heavy. 
         [0008]    As a second alternative, electrical water heaters are prior in the art that first heat a fluid such as, for instance, the water/glycol mixture used for cooling the internal combustion engine. The heated fluid is then conveyed through an additional water to air heat exchanger, as a result of which the air flowing around the heat exchanger is heated. 
         [0009]    The principle functions similar to the heating of air, as it occurs, for instance, in combustion engine-operated vehicles, with the difference that the water/glycol mixture is heated electrically and not by the waste heat from the combustion engine. 
         [0010]    A particular disadvantage in conventional methods is the required water circuit for the water/glycol mixture and the additional components, such as, for instance, a water pump, pipes, and valves. 
         [0011]    However, a water circuit also provides a relatively simple manner to utilize different waste heat sources, such as an electric motor, battery, or power electronic units that in electric vehicles must be actively cooled, which again suggests the use of cooling water circuits. 
         [0012]    Especially in light of the discussion of ranges in the case of only a limited battery capacity, water heating is a frequently used technique in electric vehicles. Also, a water heater can be installed in the engine compartment without a high-voltage component needing to be installed in the passenger compartment, which for some vehicle manufacturers represents a safety problem. 
         [0013]    Electrical water heaters are currently realized in that one or more heating elements project into the fluid and give off their heat to the fluid. These elements can be simple metal heating coils or also so-called PTC stones/ceramics. The fact that PTC ceramics (PTC=positive temperature coefficient) have a certain intrinsic safety with respect to overheating because of the temperature dependence of their resistance is advantageous with their use. 
         [0014]    A basic disadvantage when using such a water heater is that the employed heating elements must be electrically isolated from the fluid they are to heat. This requirement makes the use of such technology expensive and also has a negative effect on the efficiency and response speed of the heating elements. 
       SUMMARY OF THE INVENTION 
       [0015]    It is therefore an object of the present invention to provide a solution with which a fluid can be heated by direct contact with a heating element, without additional electrical isolation, to increase the efficiency of the heat transfer to the fluid, and to reduce the required parts expenditure and thereby the cost of such a system. 
         [0016]    In an embodiment, a device for electrically heating a fluid is provided, particularly for use in an electrically operated vehicle, whereby at least one first inductor can be heated by means of an alternating magnetic field, said inductor which can be positioned within the alternating magnetic field, whereby the inductor is arranged in the interior of a module through which a fluid to be heated can flow. 
         [0017]    In an embodiment, an induction coil can be electrically integrated into an oscillating circuit and the induction coil is arranged spatially outside the module. 
         [0018]    In an embodiment, the inductor, to generate a turbulent surround-flow and/or through-flow, can have surface elements and/or holes, and/or punches or if the inductor to generate a turbulent surround-flow has a surface made suitable by shaping, particularly by embossing and/or beading, and/or by primary shaping and/or by cutting deformation. The heat transfer between the inductor and the fluid can be increased considerably by a turbulent flow. 
         [0019]    The module can be divided. The production of the module is greatly simplified as a result. 
         [0020]    In a further embodiment of the invention, the bottom housing part and the top housing part in the interior each can have a partition wall which runs centrally and divides the top housing part or the bottom housing part in each case into a first flow channel and a second flow channel, whereby the first flow channel of the top housing part or of the bottom housing part is in fluid communication with the inlet or outlet of the housing and the second flow channel of the top housing part is in fluid communication with the second flow channel of the bottom housing part. The fluid hereby flows around the inductor in a number of regions and thus the contact time between the fluid and the inductor is longer than in the case of a simple surround-flow with only one flow channel. 
         [0021]    The inductor can seal fluid-tight with the walls of the first and second flow channel of the top housing part or of the bottom housing part and can divide the interior of the module into a top and bottom region. This creates a separation into two flow channels in the bottom region and two flow channels in the top region, which again is of benefit for the contact time between the fluid and inductor. 
         [0022]    The inductor can have an opening through which the second flow channel of the top region of the module is in fluid communication with the second flow channel of the bottom region of the module. This allows for the passing of fluid between the top and bottom region, which only then enables a complete flow through the module. 
         [0023]    In a further embodiment of the invention, the first flow channel of the bottom housing part can be in fluid communication via connections with the second flow channel of the bottom housing part, and the first flow channel of the top housing part with the second flow channel of the top housing part. 
         [0024]    In an embodiment, the flow path of the fluid can run via a connector into the module, in the first flow channel of the bottom housing part, in the second flow channel of the bottom housing part through the opening of the inductor, in the second flow channel of the top housing part, in the first flow channel of the top housing part, and finally through a connector out of the module or in the opposite direction. 
         [0025]    At least one turbulence insert can be arranged in the module with the inductor. In case the inductor itself has no component for generating a turbulent flow, or the surface of the inductor is not constructed in a suitable form, an additional turbulence insert helps to generate a turbulent flow in order to produce an improved heat transfer between the inductor and the fluid. 
         [0026]    In an embodiment, an assembly group is provided having at least one first module and at least one second module, each with at least one inductor, whereby one of the modules is arranged above and one of the modules below the induction coil. 
         [0027]    In an embodiment, the flow can pass through the individual modules of the assembly group in series or parallel. 
         [0028]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein: 
           [0030]      FIG. 1  shows a schematic structure of an induction heating system; 
           [0031]      FIG. 2  shows an exploded illustration of an induction heating system of the invention; 
           [0032]      FIG. 3  shows a section through the center plane of one of the modules; 
           [0033]      FIG. 4  shows a section through one of the modules according to the sectional plane A-A of  FIG. 3 ; and 
           [0034]      FIG. 5  shows a further section through one of the modules according to the sectional plane B-B of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0035]      FIG. 1  shows the basic structure of an induction heating system. Shown is induction coil  2  connected to a current circuit  3  that is operated with an alternating voltage. A magnetic field  1  is generated in induction coil  2  by the alternating voltage in current circuit  3 . Because of the alternating current applied to current circuit  3 , magnetic field  1  is an alternating magnetic field that changes its magnetic orientation with the frequency of the alternating current. 
         [0036]    A heating element  4 , comprising an electrically conductive material  6 , is introduced into magnetic field  1 . Eddy currents  5  are induced in heating element  4  due to magnetic field  1 . Because eddy currents  5  work against the specific resistance of heating element  4 , heat is produced in heating element  4 . 
         [0037]    It follows that material  6  which comprises heating element  4  must have a certain specific internal resistance to enable an effective heating of heating element  4 . The lower the internal resistance of material  6 , the lower the heating effect. 
         [0038]    Heating element  4  must be arranged at such a distance to induction coil  2  that it is still located within the forming magnetic field. Other elements made of electrically nonconductive materials can be arranged between heating element  4  and induction coil  2 . 
         [0039]    Induction heating systems are constructed according to this simple principle. In alternative embodiments, heating element  4  can also have different external dimensions and shapes. Thus, in principle, any regular or also irregular arrangement of material  6  of heating element  4  is conceivable. 
         [0040]      FIG. 2  shows a further embodiment of an induction heating system. An induction coil  11  is illustrated. The oscillating circuit to which it is connected for operation, similar to the structure already shown in  FIG. 1 , is not shown here for reasons of clarity. 
         [0041]    Induction coil  11  is positioned between two structurally similar modules  19 . Modules  19  are formed substantially from a top housing part  15 , a bottom housing part  14 , and one or more inductors  12 . Depending on the intended use, a turbulence insert  13  can be arranged in addition in module  19 . 
         [0042]    Above coil  11 , a bottom housing part  14  is arranged, which has an inlet or outlet connection  16  for a fluid. An inductor  12  that is heated by currents induced by coil  11 , is inserted in bottom housing part  14 . Inductor  12  is followed by a turbulence insert  13 , which is used to swirl the fluid flowing around inductor  12  for the purpose of improving the heat transfer from inductor  12  to the fluid flowing around it. 
         [0043]    In further embodiments of the invention, it is advantageous if inductor  12  itself is designed such that it assumes the function of turbulence insert  13 . One part per module  19  can be saved in this way. For the function of the turbulence insert to be taken over by the inductor, the surface structure of the inductor must be designed accordingly. This can be done by using various shaping processes such as, for instance, embossing or the introduction of beading in the inductor. Virtually any surface structures can be produced on the inductor with these two methods. 
         [0044]    Additional shapes according to the invention can be attained by a selective primary shaping, for instance. Surface structures can also be produced by cutting methods. 
         [0045]    Module  19  is closed by a top housing part  15  that has an inlet or outlet connector  17  for supplying or removing a fluid. Bottom housing part  14  and top housing part  15  are identical in the design shown here, further reducing the variety of parts. 
         [0046]    The arrangement of two modules  19 , one above and one below induction coil  11 , is shown in  FIG. 2 . Modules  19  in this case are connected at four places by connecting elements  18 . Connecting elements  18  have a placeholder  20  that creates a free space for induction coil  11  between modules  19 . 
         [0047]    During operation, a fluid flows either through connector  16  into bottom housing part  14  or through connector  17  into top housing part  15 . This depends only on the selected flow direction and in principle is conceivable in both directions. The fluid is then distributed in module  19  and then flows around turbulence insert  13  and inductor  12 , or in the case of a combination component of inductor  12  and turbulence insert  13 , only around this one component. 
         [0048]    The now heated fluid flows through the respective other connector  16 ,  17  out of module  19 . 
         [0049]    In this way, there is no direct contact between the current-carrying coil  11  and inductor  12  in contact with the fluid. Thus, additional isolation can be omitted. The efficiency of the heat transfer can thereby be increased. 
         [0050]    The precise design of module  19  and the geometry of inductor  12  or turbulence insert  13  depend greatly on the underlying intended use. Any desired shape of inductor  12  is conceivable in principle. Inductor  12  can also have elevations and depressions, or conductive fins or other elements that contribute to the swirling of the fluid flow. 
         [0051]    In alternative embodiments, it is also conceivable to arrange a plurality of inductors within a module. Thus, a plurality of closed channels, through which fluid flows and each of which has an inductor, can be formed by the module. It is also conceivable to stack a plurality of planes through which fluid flows, each with an inductor. 
         [0052]    Basically, inductor(s)  12  must be positioned in the magnetic field of coil  11  so that sufficiently strong eddy currents can still be induced in inductor(s)  12 . 
         [0053]    In alternative embodiments of the invention, an arrangement of only one module in the magnetic field of the coil is also conceivable, as well as the arrangement of a plurality of modules. Care must be taken basically that the inductors that are arranged in the modules, are still arranged within the sphere of action of the magnetic field generated by the coil. 
         [0054]    The shaping of the inductor and the induction coil in alternative embodiments may also be different from the design shown in  FIG. 2 . Thus, for example, a plurality of individual inductors, connected together to form an electrically conductive interconnected network, may also be used as an inductor. 
         [0055]    The material selection for module  19  and the tubes surrounding inductor  12  should be made in view of the employed induction method and the other operational requirements. Plastics are advantageously employed here, because no eddy currents can be induced in these, as a result of which unwanted interactions can be reduced. 
         [0056]      FIGS. 3 to 5  each show sections through one of the modules  19 . They thereby provide clearer insight into the interior structure of modules  19 . 
         [0057]      FIG. 3  in this case shows a section through the central plane of one of the modules  19 . Shown are the two connectors  16 ,  17  that are usable as an inlet or outlet, depending on the flow direction. 
         [0058]    Inductor  12  is arranged between top housing part  15  and bottom housing part  14 , thereby dividing module  19  into a top and bottom region. 
         [0059]    A partition wall  21 ,  29 , which in conjunction with inductor  12  divides each housing part  14 ,  15  into a first flow channel  22 ,  30  and a second flow channel  23 ,  31 , runs centrally in top housing part  15  and bottom housing part  14 . First flow channel  22  of bottom housing part  14  is hereby in fluid communication with second flow channel  23  of bottom housing part  14  via a connection  28 . The same applies to top housing part  15  where first flow channel  30  is in fluid communication with second flow channel  31  via connection  27 . 
         [0060]      FIG. 4  shows a section according to sectional plane A-A shown in  FIG. 3 . Additionally shown in the figure is opening  26  of inductor  12 , apart from the elements already shown in  FIG. 3  and described above. Second flow channel  31  of bottom housing part  14  is in fluid communication via this opening  28  with second flow channel  31  of top housing part  15 . 
         [0061]    It can be easily recognized that top partition wall  29  and bottom partition wall  21  is closed with inductor  1  and thus housing parts  14 ,  15  are divided into two flow channels  22 ,  23 ,  30 ,  31 . 
         [0062]    First flow channel  22  of bottom housing part  14  is thus formed by inductor  12 , wall  24 , and partition wall  21 . Second flow channel  23  of bottom housing part  14  is formed by inductor  12 , wall  25 , and partition wall  21 . Similarly, first flow channel  30  of top housing part  15  is formed by inductor  12 , wall  32 , and partition wall  29  and second flow channel  31  of top housing part  15  by inductor  12 , wall  33 , and partition wall  29 . 
         [0063]      FIG. 5  shows a section through one of the modules  19  according to sectional plane B-B shown in  FIG. 3 . 
         [0064]    This section lies within the region of the two connections  27 ,  28 , each of which connect first flow channels  22 ,  30  with second flow channels  23 ,  31 . 
         [0065]    Connectors  16 ,  17  can be used optionally as an inlet or outlet. This depends on the selected flow direction. The flow sequence of a module  19  is described hereafter in case that connector  16  is used as an inlet and connector  17  as an outlet of module  19 . 
         [0066]    The fluid then flows through connector  16  into first flow channel  22  of bottom housing part  14 , subsequently flows through connection  28  into second flow channel  23  of bottom housing part  14 , then through opening  26  into second flow channel  31  of top housing part  15 , through connection  27  into first flow channel  30  of top housing part  15 , and finally through connector  17  out of module  19 . 
         [0067]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.