This application claims priority to German Patent Application No. DE 10 2019 217 690.9, filed on Nov. 18, 2019, the contents of which is hereby incorporated by reference in its entirety.
The present invention relates to a heating module, in particular for heat transfer to a fluid, having at least one PTC thermistor element and at least one electric heating element that is different from a PTC thermistor element. The invention furthermore relates to a heating device having such a heating module.
PTC thermistor elements, also known as Positive Temperature Coefficient elements or PTC elements in brief, are increasingly used in heating modules for heating a fluid or an object. This is due in particular to the electrical resistance of PTC thermistor elements which increases with rising temperature, resulting in a maximum temperature of the PTC thermistor element, especially when a constant electric voltage is applied.
Usually, during the operation, such a PTC thermistor element initially passes through a so-called Negative Temperature Coefficient range, hereinafter also referred to as the NTC range. In the NTC range, the electrical resistance of the PTC thermistor element initially decreases with increasing temperature until a minimum electrical resistance of the PTC thermistor element is reached at an initial temperature of the PTC thermistor element. From this minimum electrical resistance, the electrical resistance increases with rising temperature, so that the PTC thermistor element is operated in the PTC range. In the NTC range, therefore, the electric current through the PTC thermistor element initially increases, especially with a constantly applied electric voltage, and then decreases in the PTC range as the temperature rises. The transition between the NTC range and the PTC range is also called the changeover point of the PTC thermistor element. During the transition and at the changeover point, peaks in the electric current and voltage occur, particularly due to the given capacitances and inductances. These peaks can result in damage in the heating module and/or in other components electrically connected to the heating module. As a result, both the heating module and the said components are designed to withstand the said current peaks and voltage peaks. This results in an increased effort and costs in the production of the heating module and/or the said components.
Such heating modules are used in particular in motor vehicles. The heating module can be operated with the mains voltage of the motor vehicle, which for example is in the range of 12V. In an increasing number of motor vehicles, in particular at least partially electrically operated motor vehicles, e.g. hybrid vehicles and/or electric vehicles, electric voltages are present which are many times higher. These voltages are usually above 100V, in particular around several hundred V, for example between 300V and 1,000V, in particular between 400V and 800V. The aim here is to operate the heating module and in particular the PTC thermistor element with the higher voltages, for example in order to increase the output of the heating module and/or simplify the integration of the heating module in the motor vehicle.
However, the increased electric voltage causes the above described current and/or voltage peaks to occur more frequently and can result in increased damage to the heating module or components electrically connected to the heating module. The design of the heating module and the said components to prevent damage therefore becomes more complex and more expensive.
Such heating modules are usually designed to provide a maximum heat output, which is specified. The maximum heat output is usually selected in such a way that the heating module provides sufficient heat or heat output even under extreme conditions. These maximum requirements result in a corresponding design of the PTC thermistor elements of the heating module, which in turn result in an increase of the current peaks and/or voltage peaks described above. This also leads to a complex and expensive production of the heating module and components electrically connected to the heating module.
The current peaks and voltage peaks that occur also result in an increased effort in operating the heating module.
In order to reduce such current peaks, DE 10 2017 218 899A1 proposes to provide several heating stages connected in parallel in a heating device, wherein a PTC thermistor element and an inductive heating element are connected in series in the respective heating stage. The inductive heating element reduces the capacitive inrush current of the PTC thermistor element connected in series with the inductive heating element, so that the capacitively induced current peaks are reduced.
Nevertheless, current peaks do occur in the heating device known from the prior art, especially with increased operating voltage, which render the production and operation of the heating device expensive and complex.
The present invention therefore deals with the object of stating improved or at least other embodiments for a heating module of the type mentioned above and for a heating device having such a heating module, which are characterized in particular by a simplified and/or cost-effective manufacture and/or by a simplified operation.
According to the invention, this problem is solved through the subject matter of the independent claim(s). Advantageous embodiments are subject matter of the dependent claim(s).
The present invention is based on the general idea of connecting the heating element and the PTC thermistor element to one another in a heat-transferring manner electrically in series in a heating module comprising a PTC thermistor element and an electric heating element, different from the PTC thermistor element. The thermal connection between the heating element and the PTC thermistor element is such that the heating element is used to overcome the so-called Negative Temperature Coefficient range, hereinafter also referred to as the NTC range in brief, of the PTC thermistor element, so that during the operation the PTC thermistor element is first heated with the heating element in order to reach a temperature that is equal to or higher than a so-called initial temperature of the PTC thermistor element at which the PTC thermistor element exhibits a minimum electrical resistance. In this way, it is thus avoided that the PTC thermistor element generates electric current peaks and/or voltage peaks during the operation at the transition between the NTC range and the range in which the electrical resistance increases with rising temperature, i.e. the Positive Temperature Coefficient range, hereinafter also referred to as the PTC range. This results in that the heating module can be simplified and/or manufactured more cost-effectively due to the reduced electric loads. In addition, the heating module can be operated in a simplified manner in this way. Furthermore, the electrical series connection of the heating element with the PTC thermistor element means that, particularly with a constant applied electric voltage, the increasing electrical resistance of the PTC thermistor element in the PTC thermistor range leads to a reduction in the electric current flowing through the series connection, so that the heat generated with the heating module is reduced. The reduced heat leads to a reduction of the electrical resistance of the PTC thermistor element, so that, especially at constant electric voltage, the current increases, so that in turn more heat can be generated. In other words, with the series connection, an operating temperature range can be specified by an appropriate design of the PTC thermistor element, within which the heating module is operated in a self-regulating manner, in particular at a constant electric voltage. This substantially simplifies the operation of the heating module.
According to the inventive idea, the heating module comprises the PTC thermistor element and the electric heating element, which is different from a PTC thermistor element. The PTC thermistor element, also called Positive Temperature Coefficient element or PTC element in short, and the heating element are electrically connected in series. According to the invention, the PTC thermistor element and the heating element are thermally connected to one another in a heat-transferring manner. In addition, the PTC thermistor element and the heating element are designed in such a way that during the operation an electric current density through the at least one PTC thermistor element is lower than the electric current density through the at least one heating element. The low electric current density through the PTC thermistor element means that the heat generated with the heating module originates predominantly from the heating element and also means that the PTC thermistor element itself does not generate any or no significant heat, particularly in the NTC region or at the transition between the NTC region and the PTC region. This results in the prevention or at least reduction of the mentioned current and/or voltage peaks.
The heat-transferring connection between the heating element and the PTC thermistor element is practical in such a manner that the temperature of the PTC thermistor element substantially corresponds to the temperature of the heating element. Substantially here means in particular that the equalisation of the temperatures of the PTC thermistor element and of the heating element due to the heat transfer is not instantaneous.
In particular, the PTC thermistor element has a characteristic and temperature-dependent curve of the electrical resistance as shown in
The heating element that is different from a PTC thermistor element means in this case that the heating element does not have the resistance curve through the NTC range and the PTC range that is characteristic for a PTC thermistor element. In particular, the heating element is free of PTC thermistors or free of a PTC thermistor element.
The heating element is for example a resistance heater, a heating wire, a thick-film heater and the like.
The solution according to the invention allows the heating module to be provided in different shapes and/or sizes. The heating module can be designed in particular in the form of a rod, i.e. especially as a heating rod.
The current density through the PTC thermistor element is realised, for example, by appropriate dimensioning of the PTC thermistor element. In particular, the PTC thermistor element can be designed with a larger cross section through which electric current can flow in order to reduce the current density.
Preferred are embodiments in which the PTC thermistor element and the heating element are designed in such a way that the electric current density through the PTC thermistor element is at least ten times lower than the electric current density through the heating element.
Preferred are embodiments, in which a maximum operating temperature is specified for the heating module, wherein the maximum operating temperature lies between an initial temperature and a final temperature of the PTC thermistor element. Thus, the maximum operating temperature of the heating module is achieved by an appropriate design of the PTC thermistor element, so that the heating module can be manufactured and/or operated cost-effectively and easily. The maximum operating temperature is for example a temperature up to which the heating module and/or adjacent components can be operated without damage.
Preferred are embodiments, in which the nominal temperature of the PTC thermistor element is equal to or higher than the maximum operating temperature. In particular, the maximum operating temperature corresponds to the nominal temperature of the PTC thermistor element. At the nominal temperature, there is a sudden increase of the electrical resistance of the PTC thermistor element. It is therefore also possible to operate the heating module reliably and simplified and/or to manufacture it more cost-effectively. Furthermore, it is thus possible to employ the PTC thermistor element between the initial temperature and the nominal temperature to provide a heat output of the heating module.
In principle, the heat-transferring connection between the PTC thermistor element and the heating element can be configured as desired. In particular, the heat-transferring connection between the PTC thermistor element and the heating element is realised by means that are different from a simple electrical connection, for example through a cable, a stranded wire and the like, and/or a pure convection and/or a pure heat radiation.
It is conceivable that the PTC thermistor element and the heating element lie directly against one another and are thus connected to one another both thermally in a heat-transferring manner and also electrically.
Alternatively or additionally, the heating module can comprise a body that is separate from the PTC thermistor element and the heating element for the heat transfer between the heating element and the PTC thermistor element, in the following also referred to as heat transfer body.
The heat transfer device (heat exchanger) is preferentially areally connected to the PTC thermistor element and the heating element in a heat-transferring manner in order to thus interconnect these in a thermally heat-transferring manner. In particular it is conceivable that the heat transfer body lies flat against the PTC thermistor element and/or the heating element.
In principle, the heat transfer body can have any shape and/or extension.
Obviously, the heating module can also comprise two or more heat transfer bodies.
Conceivable are embodiments, in which at least one of the heat transfer bodies is formed as a plate. It is thus possible to produce the heating module in an installation space-saving manner and at the same time with a high heat transfer rate between the PTC thermistor element and the heating element. In particular it is thus possible to arrange the PTC thermistor element and the heating element between two such plates.
Alternatively or additionally it is conceivable that at least one of the heat transfer bodies is designed as a ceramic. In particular it is conceivable that at least one of the at least one heat transfer body is a ceramic plate. Thus, in addition to an advantageous heat-transferring connection between the PTC thermistor element and the heating element, an electrical insulation of the heating module is achieved, in particular to the outside.
Alternatively or additionally it is conceivable to integrate the PTC thermistor element and the heating element in at least one such ceramic plate in such a way that the PTC thermistor module and the heating module are accommodated in the ceramic plate.
It is also conceivable to provide a ceramic body as heat transfer body, in which the PTC thermistor element and the heating element are embedded.
It is conceivable to arrange the PTC thermistor element and the heating element next to one another in one direction of the heating module, hereinafter also referred to as adjacent direction, and to arrange such a plate in a direction transverse to the adjacent direction, which is arranged adjacent to the PTC thermistor element and the heating element. The plate is preferably electrically insulating in order to electrically insulate the PTC thermistor element and the heating element from the outside. The plate may be in particular the said ceramic plate.
It is to be understood that the heating module can also have two or more heating elements, each of which is different from a PTC thermistor element. It is conceivable that the heating module comprises two or more PTC thermistor elements that are different from one another. At least one heating element and at least one PTC thermistor element are connected to one another in a heat-transferring manner and are electrically connected in series. Particularly preferably, all of the at least one PTC thermistor element and all of the at least one PTC thermistor element are connected in series and to one another in a heat-transferring manner.
The heating module can be used to heat any object and/or any fluid. In particular, the heating module is used to heat a fluid, for example air or a coolant.
It is to be understood that beside the heating module a heating device having such a heating module is also part of the subject-matter of this invention.
The heating device can serve for heating a fluid. For this purpose, a flow path of the fluid leads through the heating device, wherein the heating module is heat-transferringly connected to the flow path, so that the heating module heats the fluid during the operation. In particular, the heating module is arranged in the flow path of the fluid.
The heating device can comprise two or more such heating modules, which are each heat-transferringly connected to the flow path, in particular are arranged in the flow path.
It is conceivable to arrange between two such heating modules a structure through which the fluid can flow, for example a grid and/or a fin structure. By way of this, the heat-transferring surface is enlarged. As a consequence, the fluid is heated more efficiently.
Further important features and advantageous of the invention are obtained from the subclaims, from the drawings and from the associated figure description by way of the drawings.
It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated but also in other combinations or by themselves without leaving the scope of the present invention.
Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference characters numbers relate to same or similar or functionally same components.
It shows, in each case schematically
A heating module 14 according to the invention, as is shown in the
The PTC thermistor element 2 and the heating element 15 are thermally connected to one another in a heat-transferring manner such that the temperature of the PTC thermistor element 2 substantially corresponds to the temperature of the heating element 15. In the shown exemplary embodiments, the heat-transferring connection of the PTC thermistor element 2 to the heating element 5 is effected by way of at least one heat transfer body 16 that is separate from the PTC thermistor element 2 and from the heating element 15. In the shown exemplary embodiment, two such heat transfer bodies 16 each are provided, between which the heating element 15 and the PTC thermistor element 2 are arranged. The shown heat transfer bodies 16 are each formed plate-shaped or as a plate 17. In addition, the heat transfer bodies 16 are electrically insulating in the shown exemplary embodiments. In particular, the heat transfer bodies 16 are formed as a ceramic 18, for example as a ceramic plate 19. Thus, the heat transfer bodies 16 connect the PTC thermistor element 2 heat-transferringly with the heating element 15 and insulate the PTC thermistor element 2 and the heating element 15 electrically to the outside. Here, the PTC thermistor element 2 and the heating element 15 are arranged in the shown examples next to one another in a direction 20, in the following also referred to as adjacent direction 20, wherein the respective heat transfer body 16 transversely to the adjacent direction 20 is adjacent to the PTC thermistor element 2 and the heating element 15. Here, the respective heat transfer body 16 in the shown exemplary embodiments lies flat against the PTC thermistor element 2 and against the heating element 15. In the shown exemplary embodiments, the heating module 2 is thus formed in the manner of a rod 30, in the following also referred to as heating rod 30.
In the shown exemplary embodiments, the respective PTC thermistor element 2 is formed rectangular and in the manner of a brick. In particular, the respective PTC thermistor element 2 is formed as a so-called PTC thermistor brick 21, in the following also referred to as PTC brick 21.
In the exemplary embodiments shown in the
Here,
In the shown exemplary embodiments, the respective heating module 2 comprises two electrical connections 26, via which the PTC thermistor element 2 and the heating element 15 are supplied electrically.
In the exemplary embodiment of the
The
When a, in particular constant, electric voltage is applied to the heating module 2, heat is predominantly generated with the heating element 15 because of the low current density through the PTC thermistor element 2. Because of the heat-transferring thermal connection between the heating element 15 and the PTC thermistor element 2, the PTC thermistor element 2 is heated at the same time without the PTC thermistor element 2 generating the said current peaks and/or voltage peaks or these peaks are at least reduced. In other words: the transition or the changeover point of the PTC thermistor element 2 is overcome without the PTC thermistor element 2 causing the peaks in the electric current or the voltage that are typical in the prior art or these peaks are at least reduced. Here, the PTC thermistor element 2 and the heating element 15 are matched to one another and thermally connected to one another in such a manner that the heat generated in the heating module 2, up to a temperature that is equal to or greater than the initial temperature 5 of the PTC thermistor element 2, is predominantly or exclusively generated by the heating element 15. The heating operation within the PTC thermistor element 2 thus commences only when the PTC thermistor element 2 already has a temperature that is above the initial temperature 5, preferably is between the initial temperature 5 and the final temperature 10. Thus, the NTC range 7 of the PTC thermistor element 2 is bridged or skipped.
With increasing heat output of the heating module 2 and thus with increasing temperatures, the resistance of the PTC thermistor element 2 increases so that in particular at a constant applied electric voltage, the electric current flowing through the heating element 15 and the PTC thermistor element 2 decreases. This in turn leads to a reduction of the heat output of the heating element 15 and thus of the temperature. With decreasing temperature, the electrical resistance of the PTC thermistor element 2 and thus of the entire heating module 2 decreases, which leads to an increase of the electric current through the PTC thermistor element 2 and through the heating element 15 and consequently higher temperatures. Thus, a self-regulation of the heating module 2 is achieved.
The initial temperature 5 and the working range 13 of the PTC thermistor element 2 are preferentially selected in such a manner that the maximum permissible operating temperature of the heating module 2 between the initial temperature 5 and the final temperature 10 is preferentially slightly higher than the initial temperature 5 up to the final temperature 10. In particular it can be provided that the maximum operating temperature corresponds to the nominal temperature 8 of the PTC thermistor module.
In the exemplary embodiment shown in the
As shown in
Number | Date | Country | Kind |
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102019217690.9 | Nov 2019 | DE | national |