JP2018503794A - Heat exchanger and temperature control device for motor vehicle equipped with the exchanger - Google Patents

Abstract

It is a heat exchanger designed to work as an evaporator in a heat pump type temperature control device, and is an exchanger (1) having a core (26) through which a refrigerant circulates. The exchanger further comprises at least one heating element (23) placed in the vicinity of the core (26). The heating element (23) is capable of heating the core for deicing purposes.

Description

  The present invention relates to a heat exchanger for a temperature control device, particularly for the interior of a motor vehicle.

  The present invention more particularly finds application in connection with hybrid and electric motor vehicles.

  Currently, automobile manufacturers are developing vehicles that run on new energy sources to supplement or replace internal combustion engines. In particular, vehicles that have been completely electrified (electric vehicles) and vehicles that have been partially electrified (vehicles called hybrid vehicles) have been proposed.

  Since the storage capacity of today's batteries is limited, such vehicle equipment needs to be designed to limit its own electricity consumption. The consumption is at the expense of the distance that the vehicle can travel.

  Therefore, it is necessary to ensure the comfort of the passengers inside the vehicle in terms of temperature, in particular an internal combustion engine that generates heat without this temperature adjustment having an unfavorable influence on the travelable distance of the vehicle. Without it, it is necessary to heat the inside of the vehicle. This in particular limits the reliance on electric radiators to heat the interior of the vehicle.

  In this situation, a conventional air conditioning (air conditioning) loop that can operate as a heat pump to heat the air inside the vehicle using heat energy extracted from the outside air as a device for temperature adjustment inside the vehicle. Is a known practice. Such a loop comprises a heat exchanger at the front of the vehicle, a heat exchanger installed inside the vehicle, and the compressor urges fluid circulation through the loop. In the heat pump mode, the front exchanger functions as an evaporator, and the exchanger inside the vehicle functions as a condenser. In the air conditioning mode, the functions of both exchangers are switched.

  However, when the external temperature is low (below 3 ° C) and the moisture content of the air is high, the air is placed on the heat exchanger installed at the front of the vehicle (at that time acting as an evaporator in heat pump mode) The water contained in the water condenses and turns into ice. The accumulation of ice on the evaporator impedes the passage of air, impairs heat exchange and is accompanied by a reduction in the output of the air conditioner. There is also a risk of damage to this device, associated with the possibility of air entering the circuit. This in turn means that the heat pump must be deactivated and the evaporator must be deiced.

  The object of the present invention is to avoid any interruption of the operation of the heat pump and to minimize the modifications to the air conditioner and the front exchanger, thus minimizing the cost of designing the system. To alleviate these drawbacks by providing a simple solution.

  For this purpose, one subject of the invention is a heat exchanger designed to act as an evaporator in a temperature control device through which the refrigerant passes, the exchange comprising at least one core through which the refrigerant circulates. And is an exchanger with at least one heating element that is arranged in the vicinity of the core and can heat the core.

  In one embodiment of the invention, the core provides heat exchange between the fluid and the incoming air stream.

  As such, when the air conditioner operates as a heat pump and the front exchanger acts as an evaporator, and when the evaporator becomes covered with ice, the heating element heats the evaporator tube and thus Deicing can be performed.

According to various embodiments of the present invention, the following may be considered together or separately:
The heating element comprises at least one electrical resistor;
The electrical resistor is a thermistor with a positive temperature coefficient.
The heating element comprises at least a plurality of resistors mounted in parallel between the two electrical connections to form a strip.
The core comprises a plurality of tubes through which the refrigerant circulates;
The core comprises a plurality of fins placed between the tubes and in thermal contact with the tubes;
At least one of the strips is supported by at least one of the fins;
The exchanger comprises a plurality of strips supported by fins;
A strip is arranged in the core so as to ensure a substantially uniform heating of the core.
-Each strip extends parallel to each tube.
Each strip extends substantially across the width of the core along each tube;
Each strip is distributed between the two halves of the front face of the core in alignment with each other and / or in a staggered arrangement.
-Each strip occupies less than 5% of the front face of the core, or only 1% of the front face.

  The invention also relates to a temperature control device comprising a heat exchanger as described above which can act as an evaporator.

  According to one aspect of the invention, the apparatus comprises a control means for starting the operation of the heating element for controlling the heating element.

  Further features and advantages of the present invention will become apparent from the following detailed description, given by way of indication and depicted by the accompanying drawings.

The schematic diagram of the temperature control apparatus using the exchanger by this invention. The partial front view of one Embodiment of the exchanger by this invention. FIG. 3 is an explanatory diagram illustrating one method of mounting a heating element in a fin of an exchanger according to the present invention. FIG. 3 is an explanatory diagram illustrating one method of mounting a heating element in a fin of an exchanger according to the present invention. FIG. 3 is an explanatory diagram illustrating one method of mounting a heating element in a fin of an exchanger according to the present invention. 1 illustrates an exemplary embodiment of a PTC type resistor mounted as a strip. Various alternative ways of attaching the heating element to the exchanger according to the invention. Various alternative ways of attaching the heating element to the exchanger according to the invention. Various alternative ways of attaching the heating element to the exchanger according to the invention.

  In the rest of the specification, elements having equivalent structure and similar function will be denoted by the same reference numerals.

  FIG. 1 depicts a schematic diagram of a temperature control device, particularly for the interior of a motor vehicle, using an exchanger according to the invention.

  For the sake of simplicity, this device will be described in connection with application to a motor vehicle.

  The adjustment device mainly includes a first heat exchanger 1, a second heat exchanger 7, a compressor 1, and an expansion valve 4. These various elements are connected to the loop by tubes 5 so that the refrigerant circulating through the tubes 5 can pass through them.

  The first heat exchanger 1 is placed at the front part of the vehicle (generally under the hood on the front surface of the vehicle), and allows the refrigerant to pass through the exchanger. The exchanger 1 is intended to maximize the exchange of heat between the outside air stream 3 coming from the front of the vehicle through the vehicle's radiator grille and the refrigerant. In order to increase the air flow, the device may include a fan 2 (eg, a detachable fan) that is activated when the air flow rate 3 becomes insufficient.

  The second exchanger 7 is installed inside the vehicle, generally in a housing 6 known as HVAC (representing heating, ventilation, and air conditioning) and also allows refrigerant to pass through the exchanger. . The exchanger exchanges heat between the air inside the vehicle (which is drawn to enter HVAC 6 by arrow 8 and out of there by arrow 9) and the refrigerant. It is intended to maximize.

  Each of the above elements forms a loop suitable for operating as a conventional air conditioning loop. In this case, the refrigerant passes through the loop in the direction of arrow 12. The exchanger 7 inside the vehicle then acts as an evaporator to evaporate the refrigerant, thereby removing heat energy from the air inside the vehicle, thus cooling the air. The refrigerant in the gaseous state is then compressed in the compressor 10 and then sent to the front exchanger 1. The front exchanger 1 then acts as a condenser to condense the fluid and thereby provide thermal energy to the outside air. Thereafter, the fluid returns to the evaporator 7 via the expansion valve 4.

  The loop described above is also suitable for operation as a heat pump. In its operation, the exchanges 1 and 7 work in the same way as the direction of travel through the loop (arrow 11) changes. The front exchanger 1 works as an evaporator to remove heat energy from the outside air. The heat energy is then passed by the fluid to the air inside the vehicle via the exchanger 7 which acts as a condenser. Specifically, the refrigerant made into a gas state by the front exchanger 1 is compressed by the compressor 10, condensed in the exchanger 7, and then expanded again to return to the exchanger 1.

  The diagram of FIG. 1 is a schematic diagram, and in general there are two different circuits in this type of loop that can have two distinct modes of operation, and the two modes Switching between is accomplished by switching the tubing circuit from one to the other using a control valve (not shown).

  As indicated above, when the loop operates as a heat pump and the front exchanger 1 functions as an evaporator, and the temperature of the outside air 3 is low and the water content is high, the front exchanger 1 is iced. The heat exchange between the air and the refrigerant, and thus the efficiency of the temperature control device.

  FIG. 2 depicts a partial front view of one embodiment of the exchanger according to the present invention.

  In this embodiment, the exchanger 1 includes an assembly of pipes 20 that are substantially parallel to each other, and the refrigerant circulates through the pipes 20. The pipes 20 are, for example, substantially parallel to each other and attached in parallel between the two fluid manifolds to which they are connected (in FIG. 2, only the right manifold referred to by reference numeral 21 is attached). Is visible).

  The surface visible in FIG. 2 is the front surface that is located on the side from which the air 3 arrives (FIG. 1) and is located in the plane referenced by the symbol xOz in the Cartesian coordinate system Oxyz. Each tube 20 is, for example, a tube that is flattened in the plane xOy and extends in the direction Ox. Each manifold extends along the axis Oz.

  In an alternative embodiment, each tube 20 is formed of two plates that are each configured to be fluid tightly joined together. Its configuration is such that it defines an internal space in which the refrigerant can circulate.

  Fixed between the tubes 20 are fins 22 called inserts. Each fin 22 is composed of a thin strip made of a material that is a good heat conductor, for example, and is folded into a concertina (accordion) shape. Each fin 22 is in thermal contact with each adjacent tube 20 and has a function of increasing heat exchange between the outside air flowing along the axis Oy and the fluid circulating through each tube 20.

  The aggregate of the tube 20 and the fins 22 constitutes what is known as an exchanger core that plays a role of heat exchange between air and refrigerant (see reference numeral 26).

  According to the invention, the exchanger 1 further comprises at least one heating element 23 placed in the vicinity of the core. The heating element 23 is intended to heat the core in order to melt the ice that can cover the core.

  The heating element 23 is advantageously a set of electrical resistors, preferably a positive temperature coefficient thermistor, ie a PTC thermistor (ie a thermistor whose resistance increases with temperature).

  FIG. 6 depicts one embodiment of a heating element 23 using a PTC strip, viewed in partial cross section in the plane xOz.

  FIG. 6 thus depicts a PTC assembly 60, for example in the form of a plurality of tiles. The tiles are arranged side by side and are electrically connected in parallel to each other, for example, by conductive bands 61 and 62 placed on both sides of each tile 60. The assembly forms a strip (preferably covered with an electrically insulating material 63).

  In the embodiment of FIG. 2, the PTC strip 23 is placed on the core 26 itself. Specifically, the strip 23 is supported by the fins 22 as shown in FIGS. 3, 4, and 5.

  FIG. 3 is a schematic view of the fin 22 in the plane xOz, where a plurality of cutouts 30 are made in the fin 22 to accept the PTC strip 23.

  FIG. 4 is a diagram similar to FIG. 3, but with a PTC strip 23 disposed in the fin.

  FIG. 5 is a partial cross-sectional view in the plane yOz of the core 26 of FIG. 2 and depicts two tubes 20 with a portion of the fin 22 sandwiched therebetween.

  The fin 22 has a cutout 30 on one side located on the inflowing outside air 3 side of both sides thereof. The strip 23 is placed in the cutout 30.

  In the alternative embodiment depicted in FIG. 5, the fin 22 has a second cutout 31 on the opposite side of the previous one, and the cutout 31 receives the second PTC strip 27. Yes.

  This method of inserting the PTC strip 23 into the fin 22 provides the advantage that it can be easily adapted to existing types of exchangers without having to review the exchanger design.

  FIG. 2 also depicts control means 25 for controlling the PTC strip 23. The means is electrically connected to each connection 24 of the strip 23. For example, conductive bands 61 and 62 shown in FIG. 6 are connected to these connections.

  The control means 25 operates the PTC 23 when the core 26 needs to be deiced. To do so, the control means receives at one input 28 one or more parameters indicating that icing has occurred. The parameter may be a parameter that triggers the operation of the fan 2 when the fan 2 (FIG. 1) is controlled (or may be derived from those parameters). For example, as parameters, it is possible to consider the temperature of the propulsion motor, the air conditioning request set, and the like. They may also be parameters that are involved in the operation of the loop of FIG. 1, in particular parameters that allow a transition from the air conditioning mode to the heat pump mode. It can also be reduced to means for measuring the temperature of the air in the vicinity of the exchanger 1.

  7, 8 and 9 are diagrams illustrating various possible attachments of the PTC strip within the exchanger core.

  In order to best deicing the entire heat exchanger, it is advantageous to heat the exchanger as uniformly as possible, and in order to do so, it is advantageous to use multiple PTC strips such as 23 It is.

  In the first alternative depicted in FIG. 7, six strips 23 are arranged in the core 26 in three lines parallel to the axis Ox as seen in the plane xOz, Is formed by two strips. If L is the dimension of the core along the axis Oz, each line is distributed as follows. That is, the first line (strips 71 and 72) is at L / 6 from the upper edge, and the second line (strips 73 and 74) is at L / 3 from the first line. It seems that the lines (strips 75 and 76) are at L / 3 from the second line and thus at L / 6 from the lower edge.

  In the second alternative depicted in FIG. 8, there is also a three line layout as shown in FIG. 7, but in this case each line is formed by a single strip, 82 and 83 are allocated respectively.

  A third alternative that allows for more uniform heating is shown in FIG. The six PTC strips 91 to 96 are no longer facing each other so as to form a triple line as shown in FIG. 7, but are arranged in a staggered or stepped arrangement.

  In any of the embodiments, the cross-sectional area of the PTC strip 23 in the plane xOz is advantageously limited to about 5% of the total surface area of the core 26, preferably less than 1% of this total surface area. I will.

Claims (10)

A heat exchanger (1) designed to act as an evaporator in a temperature control device through which refrigerant passes, comprising at least one core (26) through which the refrigerant circulates,
An exchanger comprising at least one heating element (23) arranged in the vicinity of the core (26) and capable of heating the core.   The exchanger according to claim 1, characterized in that the heating element (23) comprises at least one electrical resistor (60).   The exchanger according to claim 2, characterized in that the electrical resistor (60) is a thermistor having a positive temperature coefficient.   The heating element (23) comprises at least a plurality of resistors (60) mounted in parallel between two electrical connections (61, 62) to form a strip. The exchanger according to any one of claims 2 and 3.   The core (26) includes a plurality of pipes (20) through which the refrigerant circulates and a plurality of fins (22) placed between the pipes (20) and in thermal contact with the pipes (20). The exchanger according to any one of the preceding claims.   6. Exchanger according to claim 5, characterized in that at least one of the strips (23) is supported by at least one of the fins (22).   The exchanger of claim 6, comprising a plurality of strips supported by the fins (22).   8. Exchanger according to claim 7, characterized in that the strip is arranged in the core (23) so as to ensure a substantially uniform heating of the core.   A temperature control device comprising the heat exchanger according to any one of the preceding claims, which can serve as an evaporator.   10. Device according to claim 9, characterized in that it comprises control means (25) for starting the operation of the heating element for controlling the heating element (23).

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