TECHNICAL FIELD
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The disclosure relates generally to a cooling circuit for a vehicle and, more particularly, to the cooling of vehicle propulsion systems, whether thermal or electric, comprising batteries and a main mover. In particular, the disclosure eliminates the need for an expansion tank at the top of the cooling circuit. The disclosure can be applied in heavy-duty vehicles, such as trucks, buses, and construction equipment. Although the disclosure may be described with respect to a particular vehicle, the disclosure is not restricted to any particular vehicle.
BACKGROUND
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Vehicle propulsion systems, whether thermal or electric, generate heat in addition to mechanical motion. Battery Electric Vehicles, also called BEVs and more frequently called EVs, are fully electric vehicles. BEVs use rechargeable batteries and electric motors instead of internal combustion engines. ICE vehicles ignite and combust fuel within an internal combustion engine (ICE). In both cases, if the generated heat is too high, it can lead to degradation of the systems or, worse still, destruction of the vehicle by fire. The operating temperature must therefore be controlled.
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Most heat control systems use a fluid that exchanges heat with the powertrain and then with the outside environment. The fluid will increase its internal temperature and, given the laws of physics, it will expand. The vehicle cooling circuit must therefore include an expansion tank to manage the expansion of the fluid due to the increase in temperature.
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Although necessary, expansion tanks are bulky components that must be located at the highest point in the cooling circuit. This is a very important constraint in the architecture of the vehicle, particularly for the design of the passenger compartment and the driver's living area.
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An alternative to the expansion tank would be to manage the pressure of the coolant rather than its volume. But as well as being complicated (the circuit has to withstand high pressure), in this case the cooling properties will also be altered, which is not optimal for performance.
SUMMARY
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The invention aims at solving the above problems.
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According to a first aspect of the disclosure, a cooling circuit for a vehicle comprises:
- a main mover,
- a coolant for cooling said main mover, and
- at least one coolant expansion system,
wherein the at least one coolant expansion system is a lyophobic heterogeneous system including a nanoporous material, the coolant being a non-wetting liquid on the porous material at a standard pressure of the coolant (for example at atmospheric pressure) and capable to enter the nanoporous material upon an increase in coolant pressure.
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The first aspect of the disclosure may seek to eliminate the need for an expansion tank at the top of the cooling circuit. Due to the specific coolant expansion system using a lyophobic heterogeneous system, the coolant can reversibly enter/exit the nanoporous material under the effect of pressure increase/decrease. The expansion of coolant under the effect of an increase in temperature and pressure can thus be absorbed elsewhere than at the top of the cooling circuit.
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In some examples, the main mover is an electric motor or a combustion engine.
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In some examples, the main mover is an electric motor, and the cooling circuit further comprises at least one electric battery, the coolant being capable of cooling said main mover and said at least one electric battery.
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In some examples, the nanoporous material is a mesoporous material.
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In some examples, the nanoporous material is selected from MCM-41, zeolites, and Zeolitic imidazolate frameworks (ZIFs).
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In some examples, the nanoporous material is arranged inside a pipe of the cooling circuit.
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In some examples, the coolant comprises water.
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In some examples, the coolant comprises water and an ionic compound.
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In some examples, the ionic compound is lithium chloride.
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In some examples, the cooling circuit has no expansion tank at the top of the cooling circuit.
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In some examples, the cooling circuit comprises a heat exchanger.
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In some examples, the cooling circuit comprises at least one coolant expansion system associated with the heat exchanger.
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In some examples, the heat exchanger is fitted with a gas evacuation valve.
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In some examples, the cooling circuit comprises at least one coolant expansion system associated with the main mover.
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In some examples, the cooling circuit comprises at least one coolant expansion system associated with the at least one electric battery.
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In some examples, a motor vehicle comprises a cooling circuit described above.
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In some examples, the motor vehicle is a truck.
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The above aspects, accompanying claims, and/or examples disclosed herein above and later below may be suitably combined with each other as would be apparent to anyone of ordinary skill in the art.
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Additional features and advantages are disclosed in the following description, claims, and drawings, and in part will be readily apparent therefrom to those skilled in the art or recognized by practicing the disclosure as described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
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With reference to the appended drawings, below follows a more detailed description of aspects of the disclosure cited as examples.
- FIG. 1 is a schematic plan view of a cooling circuit of the invention according to one example.
- FIG. 2 is a schematic cross-sectional view of a coolant expansion system of the cooling circuit.
- FIG. 3 is a perspective view of the coolant expansion system.
- FIG. 4 is a schematic view illustrating different types of wetting of the coolant.
- FIG. 5 is a partial schematic view of a coolant expansion system of the cooling circuit.
- FIG. 6 is a hysteresis cycle illustrating the pressure of the coolant as a function of its volume.
- FIG. 7 is a diagram illustrating the filling and emptying of the coolant expansion system as a function of the type of coolant expansion system material.
DETAILED DESCRIPTION
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Aspects set forth below represent the necessary information to enable those skilled in the art to practice the disclosure.
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FIG. 1 is a schematic plan view of a cooling circuit of the invention according to one example. A vehicle 10, in particular a truck, is shown. It should be appreciated that the vehicle 10 may be an automobile, a heavy-duty vehicle such as a truck, a van or a sport utility vehicle, for example. As used herein, the term vehicle is not limited to just an automobile, a truck a van or a sport utility vehicle, but may also include any self-propelled or towed conveyance suitable for transporting a burden.
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The vehicle 10 comprises a prime mover 11 which, in the example, is an internal combustion engine. Although, in variant, the prime mover 11 could be an electric motor or a hydraulic motor. Therefore, the vehicle can be a Hybrid Electric Vehicle (HEV) or Battery Electric Vehicle (BEV). Hydraulic motors are used for moving constructions equipment and other special vehicles.
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The vehicle 10 also includes a cooling circuit 12. The role of the cooling circuit 12 is to bring the prime mover 11 up to operating temperature quickly and keep it there. In known cooling circuits, the coolant leaves an expansion tank 13 and then passes through a heat exchanger 14 (typically a radiator), where it is cooled by the airflow created by a fan, for example, which is itself driven by a belt or by a hydraulic motor on certain models, which saves energy. A water pump, not shown, is also driven by the belt, circulating the water without pressure. The coolant continues its journey through the prime mover 11 to cool it down. It can then pass through the passenger compartment radiator, and through at least one electric battery 15. A thermostat allows the passage of the coolant to be opened when it reaches the right temperature towards the expansion tank, otherwise it remains closed. The expansion tank 13 absorbs volume variations, since when heated, the coolant expands.
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As described above, the expansion tank has a number of disadvantages. Expansion tanks are bulky components that must be located at the highest point in the cooling circuit. This is a very important constraint in the architecture of the vehicle.
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It is proposed to remove the expansion tank by using at least one lyophobic heterogeneous system (LHS) as a coolant expansion system 16 in the cooling circuit 12, at one ore more points of the cooling circuit 3. LHS is a system comprising a nanoporous solid material and a non-wetting liquid. In this type of combination, the material only becomes porous to the fluid if the fluid pressure conditions are met. If the pressure condition is met, the fluid penetrates the porous material as it would in an empty tank. The pressure will then remain constant in the cooling circuit 12.
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The location of the coolant expansion system 16 will be determined in order to optimize cooling efficiency and reduce pressure variations as close as possible to the point where the temperature rises (and therefore expansion). The coolant expansion system 16 can, for example, be arranged close to the heat exchanger 14, the prime mover 11, and/or the electric batteries 15. Each coolant expansion system 16 is therefore in thermal contact with one of these elements, which absorbs the expansion of coolant under the effect of an increase in temperature and pressure.
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So the expansion system doesn't have to be in a single place, at the top of the circuit, but can be anywhere on the cooling circuit and divided up to improve packaging, performance and durability. This saves a lot of space, particularly near the cab in the case of a truck, and provides an optimized cooling circuit.
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In some situations, the coolant is heated to boiling and the bubbles need to be ejected. A solenoid valve can be added to the filler cap, for example at the top of the heat exchanger 14, to vent the gas. The solenoid valve opens as soon as bubbles are detected. This can be easily achieved using an impedance sensor.
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FIG. 2 is a schematic cross-sectional view of the coolant expansion system 16, whereas FIG. 3 is a perspective view of the coolant expansion system 16.
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The cooling circuit 12 includes pipes 19 through which the coolant 17 circulates. The coolant flow is represented by the arrow 18. Pipes 19 can be cylindrical in shape. Each coolant expansion system 16 is a zone of nanoporous material 20 surrounding the coolant 17 and in contact with the coolant 17. The nanoporous material 20 advantageously has a cylindrical (tubular) shape and is arranged inside an enlarged portion (larger diameter) 19a of the pipe 19.
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Preferably, the diameter of the coolant flow in the coolant expansion system 16 is the same as that of the coolant flow outside the coolant expansion system 16.
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FIG. 4 is a schematic view illustrating different types of wetting of the coolant 17, whereas FIG. 5 is a partial schematic view of the coolant expansion system 16.
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Wetting is the behaviour of a liquid 17 (the coolant) in contact with a solid surface. In the case of total wetting (configuration a)), the liquid spreads until it forms a film. The contact angle is then zero. When the liquid 17 retracts and forms a drop, this is known as partial wetting (configuration b)). The contact angle θ then results from the balance of surface tensions. The limit where the contact angle θ is equal to 180 degrees is called non-wetting (configuration c)).
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In the LHS system 16, at normal temperature and pressure, for example at atmospheric pressure, coolant 17 cannot penetrate the holes (pores) 20a of the nanoporous material 20 because of its non-wetting properties. The coolant 17 does not adhere to the material 20. The material 20 applies a kind of resistance force to the liquid droplet. Thus, the drop cannot enter the hole 20a in the material 20 due to the non-porous behaviour of the material 20.
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When the pressure increases, the interaction between the material 20 and the coolant 17 is different, the wetting condition appears, so the resistance force applied to the droplet is reduced. The material 20 then exhibits porous behaviour and the coolant 17 penetrates the material 20.
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FIG. 6 is a hysteresis cycle illustrating the pressure of the coolant 17 as a function of its volume, more precisely the volume of coolant 17 outside the nanoporous material 20.
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Intrusion and extrusion in LHS involve a pressure-induced process of a liquid penetrating a lyophobic porous matrix and an opposite process of the liquid emptying the pores at lower pressures. The intrusion-extrusion cycle generally exhibits hysteresis: a difference between the intrusion pressure at which the nonwetting liquid enters the nanopores upon compression and the extrusion pressure at which the nonwetting liquid leaves the nanopores upon decompression.
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In a first part 1 of the hysteresis cycle, when the coolant pressure starts to increase (i.e. when the coolant temperature starts to rise), the volume decreases slightly until the coolant 17 penetrates the material 20. A first plateau 2 (the intrusion plateau) is then reached, along which the coolant 17 gradually penetrates the material 20 at a constant pressure value Pint. Once the coolant 17 has completely filled the pores 20a in the material 20, the pressure starts to increase again (part 3).
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When the pressure starts to drop, the cycle follows a part 4 identical to part 3, until the pressure reaches a second pressure value Pext when the coolant 17 begins to withdraw from the pores 20a of the material 20. Along this second plateau 5 (the extrusion plateau), the coolant 17 gradually withdraws from the pores 20a of the material at a constant pressure value Pext. In the last part 6 of the cycle, the coolant 17 has completely withdrawn from the material 20 and the volume slowly increases while the pressure decreases.
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To summarise, when the LHS system is subjected to an external pressure, the non-wetting coolant 17 is forced to enter into the pores (intrusion) till the nanoporous material is saturated. Then, when the pressure is lowered, the coolant 17 goes out of the pores (extrusion) at a pressure that can be lower than the intrusion pressure.
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FIG. 7 is a diagram illustrating the filling (intrusion) and emptying (extrusion) of the coolant expansion system as a function of the type of coolant expansion system material.
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Three types of hysteresis cycle can be envisaged. According to type A, the first pressure value Pint and the second pressure value Pext are identical. The first pressure value Pint and the second pressure value Pext may be different (type B). Lastly, according to type C, the second pressure value Pext is zero. Type B cycle is the most interesting. Indeed, the type A cycle is unstable and in the type C cycle there is a lack of coolant.
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The porous material used in the systems is advantageously a nanoporous material, and more particularly a mesoporous material. A nanomaterial is a material whose structure contains cavities whose size does not exceed 100 nanometers. A mesoporous material is one whose pores have a diameter of between 2 and 50 nm.
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The nanoporous material can be selected from MCM-41, zeolites, and in particular from hydrothermally stable zeolites, and from Zeolitic imidazolate frameworks. MCM-41 (Mobil Composition of Matter No. 41) is a mesoporous material with a hierarchical structure from a family of silicate and alumosilicate solids that were first developed by researchers at Mobil Oil Corporation. Zeolitic imidazolate frameworks (ZIFs) are a class of metal-organic frameworks (MOFs) that are topologically isomorphic with zeolites. ZIFs are composed of tetrahedrally-coordinated transition metal ions (e.g. Fe, Co, Zn) connected by imidazolate linkers. In particular, ZIF-8 can be used. ZIF-8 is a material with a porous structure, used to separate carbon molecules (carbon capture systems from ambient air). Other materials that can be used are hexagonal mesoporous silica (HMS), SBA-15 (Santa Barbara Amorphous-15), and controlled pore glasses (CPG) such as for example CPG-10-500.
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The pore sizes of these materials make them suitable for use with water as a liquid. The addition of salts increases the non-wetting properties of water and generally allows higher pressures to be achieved.
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The material can be chosen according to the temperature (up to 100°C) and pressure range to be used. The lyophobic heterogeneous system can operate at temperatures ranging from -20°C to +1300°C (MCM-41), so the operating conditions of the vehicles are respected.
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The coolant may be water or a mixture of water and lithium chloride (LiCl).
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The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including" when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
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It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the present disclosure.
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Relative terms such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" may be used herein to describe a relationship of one element to another element as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.
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Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
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It is to be understood that the present disclosure is not limited to the aspects described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the present disclosure and appended claims. In the drawings and specification, there have been disclosed aspects for purposes of illustration only and not for purposes of limitation, the scope of the inventive concepts being set forth in the following claims.