EP2981769B1 - Device for preheating fluid, in particular coolant for a combustion engine - Google Patents

Description

Technical area

The invention relates to a device for heating a fluid, more particularly a cooling fluid of a combustion engine. The present invention also relates to a method for heating fluids for multiple applications.

The fluids can be sanitary water, chlorinated water, water / glycol, hydrocarbons (gas oil, gasoline, oil, ...), vegetable oils (rapeseed), liquid gases or water. gaseous state, ...

Examples of heating applications are numerous: industrial, generators, cogeneration units, thermal engines (gasoline, diesel, LPG, ...) swimming pools, spas, sanitary water, aquariums, ponds, ...

Prior art

The engines of emergency power generators (hospitals, companies, ...) must be maintained at a temperature (~ 40 ° C) ideal for the direct start-up of these, to ensure within a few seconds the supply of electricity in the event of a power failure.

The engines of emergency vehicles (ambulances, firefighters, ...) must also be preheated to ensure an immediate start in the best conditions to ensure their interventions.

The engines of private vehicles can also be heated before departure, in order to not only start in good conditions, but also to improve the comfort of the passengers, by a directly hot cockpit and / or by windows demisted and / or defrosted . Many studies demonstrate a beneficial effect on fuel reduction as well as on the reduction of pollution at start-up by using such a heater.

Manufacturers are offering externally powered heaters on the market that operate on the principle of thermosyphon. The heating element is directly immersed in the heating body, or in the water chambers of the engine and therefore directly in contact with the fluid. In order to reduce its bulk, the specific load per cm ² is very high, which makes the devices unreliable over time. The efficiency of these is very low and placement on the circuit is not easy to allow thermo-circulation. For more than a decade, engine manufacturers have significantly changed the design of water chambers in engines and, it becomes difficult to place this type of heating, because this configuration no longer allows to create an efficient circulation by this principle of thermosyphon and thus to heat the engines correctly and uniformly.

Others offer devices with a circulation pump. The heating element (immersion heater) is also immersed directly in the water. The yield is significantly higher compared to the thermosiphon process. However, the size remains too high to allow easy placement on medium vehicles (private vehicles, ambulances, trucks ...). In addition, the pumps generally used must be positioned horizontally, which further reduces the possibilities of integration under the engine hood. The only possibility would be to reduce the size of these devices by decreasing the length of the heating element. This solution would affect the reliability, because one would leave standards usually given by the manufacturers concerning the maximum specific load of the heating elements for this type of fluid. This would cause boiling of the fluid at the heating element which would result in degradation of the shielding thereof, and then continue with premature failure of the element.

The patent document EP 0 899 985 A1 discloses a heating device according to the preamble of claim 1.

Patent documents EP 2 562 016 A1 , US 3,782,456 , WO 2004/038303 A2 and US 6,816,670 B show different types of device for heating a fluid.

The patent document WO 2011/016763 A1 discloses a combustion engine coolant preheating device. It essentially comprises a main body with an interior volume, a an inlet, an outlet, and a heater disposed in the interior volume of the main body. The heating body itself comprises an interior volume in which are arranged one or more electrical resistors of the type of positive temperature coefficient PTC (acronym for "Positive Temperature Coefficient"). This preheating device has the advantage of being fairly simple construction. The thermal connection between the resistors and the fluid is however not optimal. In addition, the main body is subject to significant loss of ambience. The thermal efficiency of this device is therefore not optimal. This device seems to operate on the principle of thermosiphon, which limits the heating performance.

The patent document DE 102 58 257 A1 also discloses a fluid preheating device of a combustion engine, such as for example the fuel, the lubricant or the coolant. It essentially comprises an elongated main body with a mounting flange. The main body is intended to be immersed in the fluid and the flange provides a tight mounting on a wall. The main body includes various elements including a frame, a conductive sheet and PTC positive temperature coefficient type heaters. This preheating device has the same disadvantage as that of the document cited above, namely that the thermal contact between the heating elements and the fluid is not optimized. This device seems to operate on the principle of thermosiphon, which limits the heating performance.

The patent document WO 01/33071 A1 discloses a method of preheating an engine and a device for carrying out the method in question. The method essentially includes providing a heating element such as an electrical resistor in a tank separate from the engine and containing engine coolant. The electrical resistance of the spiral type is in direct contact with the fluid. This direct contact is undesirable for some applications. In addition, the overall size of the device is quite large and may pose integration problems. This device seems to operate on the principle of thermosiphon, which limits the heating performance.

The patent document US 4,371,777 a relates to a fluid heating body, forming a U-shaped circuit and comprising PTC type heating elements. These are arranged in the hollow of the U, the U being formed by a bent pipe provided with two solid elements fitting the pipe and between which the PTC elements are arranged. Alternatively, the heating body may comprise two solid elements arranged against each other via a seal at the fluid passage to ensure a seal. A cap in two parts is planned. The heat exchange power remains limited in this teaching, especially because of the limited diameter of the bent pipe and the limited number of heating elements.

The patent document DE 200 20 347 U shows a heating body with a rectilinear passage for a fluid and a housing for a ceramic heating element. The heat exchange power is very limited.

The patent document GB 2,079,421 A shows a heating body, in particular for hot drink dispensers, inside a mold containing U-shaped channels and electrical resistors arranged outside the U-shaped path. Due to the distance of resistances to the U-shaped channels, the heat exchange power is limited.

The patent document GB 2 014 417 A shows a heating body having a triple U shaped passage with electrical resistors housed in grooves extending into the recesses of the U-shaped profiles of the passage. The electrical resistances extend perpendicular to the main plane of the heating body. In this teaching, the heat exchange between the resistor and the fluid takes place in three different places, thereby increasing the efficiency of the system. However, the heat exchange is mainly in the middle of the path followed by the fluid and a risk of heat loss at the fluid outlet location is present.

The patent document DE 87 01 656 U discloses a heater with a U-shaped passage and an open groove extending along the U-shaped profile, said groove housing an electrical resistance. The passage must have a certain length for the fluid to reach the desired temperature.

Summary of the invention Technical problem

The object of the invention is to propose a fluid heating device that overcomes at least one of the abovementioned disadvantages. More particularly, the invention aims to provide a fluid heating device having improved thermal efficiency and simple and economical construction. More particularly, the invention aims to provide a compact fluid heating device and simple and economical construction.

Technical solution

The invention relates to a device for heating a fluid, according to claim 1.

The cross section of the groove or grooves has a preferentially constant profile over a major part of its length.

According to an advantageous embodiment of the invention, the width of the groove or grooves is greater than its height, and for the majority of its length.

According to an advantageous embodiment of the invention, the ratio between the width and the height of the groove is greater than 2, preferably 3, more preferably 5.

According to an advantageous embodiment of the invention, the resistance or resistors are generally elongated and flat.

According to an advantageous embodiment of the invention, the closing plate (s) extends beyond the electrical resistance (s) and / or beyond the groove (s) so as to bear against the heating element. .

According to an advantageous embodiment of the invention, the closure plate or plates are adapted to be fixed to the heating body by screwing.

According to an advantageous embodiment of the invention, said plate or plates comprise orifices along their edges and the heating body comprises threaded bores intended to receive fastening screws disposed through said orifices.

According to an advantageous embodiment of the invention, the closure plate or plates are in contact with the electrical resistance or resistors. Some pressure between the resistance (s) and the plate (s) can be provided to ensure intimate contact and optimal thermal conduction. This pressure may be greater than or equal to 10 Pa, preferably 100 Pa, more preferably 1000 Pa.

According to an advantageous embodiment of the invention, the passage through the heating body is substantially straight.

According to an advantageous embodiment of the invention, at least one of the longitudinal channels opens on at least one face of the heating body, preferably on two opposite faces, the said face or faces being provided with closure plug (s) of the zones where the or said channels open. Preferably, all the longitudinal channels open on both sides in question.

According to an advantageous embodiment of the invention, the or each of said faces of the heating body on which at least one of the longitudinal channels opens is provided to the areas where the said channel or channels open a hydraulic connection fitting of the device. The device preferably comprises three longitudinal channels, the branch connections being aligned with the central channel and the caps being aligned with two lateral channels. Similarly, the device may comprise five longitudinal channels, the central corresponding to the connections and the side to the plugs.

According to an advantageous embodiment of the invention, the groove and the electrical resistance or resistors extend transversely over all of the longitudinal channels.

According to an advantageous embodiment of the invention, the or at least one of the transverse channels opens on one side of the heating body, said face being provided with closure plug (s) of the zone or zones where the said channel or channels open.

According to an advantageous embodiment of the invention, the transverse channel or channels are made by drilling, spark erosion and / or extrusion.

According to an advantageous embodiment of the invention, the longitudinal channels are made directly during the manufacture of the body by extrusion and the transverse channels are made by removal of material, for example by drilling and / or machining.

According to an advantageous embodiment of the invention, the heating body is a block in one piece generally parallelepipedic.

According to an advantageous embodiment of the invention, the heating body comprises two grooves on opposite faces of said body, the passage extending between said faces and said grooves.

According to an advantageous embodiment of the invention, the electrical resistance or resistors are of the PTC type

The invention also relates to a combustion engine equipped with a cooling fluid heating device, remarkable in that the device is in accordance with the invention.

The invention also relates to a method of preheating the cooling fluid of a combustion engine with a heating device, remarkable in that the device is in accordance with the invention.

Benefits brought

The measures of the invention have the advantage of optimizing the thermal efficiency, more precisely by increasing the efficiency of the heat exchange between the heating resistor (s) and the fluid, and also by reducing the losses to the environment. Indeed, the construction of the heating body and the arrangement of the resistors according to the invention allows an intimate contact between the resistors and the fluid. The heating resistor (s) extend indeed along most of the fluid path because they are placed parallel in the main direction of the passage. The division of the passage into several longitudinal channels makes it possible to increase the heat transfer for a given length of the passage. The electrical resistances can be supplied with 110, 230, 400 or 480 VAC (typically on the home network) when preheating the engine of a stationary vehicle. One or more additional resistors can be supplied with 12 or 24 VDC voltage from the vehicle battery to continue heating when the engine is running. The compact and geometric shape of the heating body makes it easy to isolate it by equipping it with an insulating jacket. The latter can be provided removable, which is made easy again by the optimized shape of the heating body. The heating body can be realized at low cost from a block of material such as aluminum with some conventional machining operations and controlled.

Brief description of the drawings

• The figure 1 is a representation of the transverse face of the heating device according to the invention.
• The figure 2 is a sectional view II-II of the heating device of the figure 1 .
• The figure 3 is a view of the longitudinal side, on the side of the plugs, of the heating device of the Figures 1 and 2 .

Description of the embodiments

The device for heating or preheating a fluid illustrated in FIGS. Figures 1 to 3 essentially comprises a solid element 4 of generally rectangular cross section through which a passage for the fluid. The passage comprises three rectilinear and parallel channels 6 crossing the block from one side to the other. These channels are made by drilling.

The passage also comprises two transverse channels 8, each being close to one of the two ends of the longitudinal channels 6. These channels have the role of providing a communication of the longitudinal channels. These transverse channels are also preferably made by drilling.

The heating body 4 can be made by extrusion. The transverse channels can then be made by machining.

The longitudinal channels 6 open on the front and rear faces of the body 4. The areas of said faces where the lateral channels open are provided with plugs 12, while the areas of said faces where the central channel opens are provided with connectors 16 intended for hydraulic connection. or aeraulic device. These connections may in particular be of the type with corrugated end for cooperating with a flexible hose insertion. The plugs 12 and / or the connectors 16 are preferably of the type with a male thread cooperating with a female thread formed in the body 4.

The transverse channels 8 open only on one of the lateral faces of the body 4. The zones of said face where these channels open are provided with a plug 10. The plugs 10 are preferably of the type with male thread cooperating with a female thread made in the body 4.

The body 4 comprises two grooves 14 on the longitudinal faces of the body 4 extending along the longitudinal channels 6. The grooves 14 have a width substantially greater than their height, for example in a ratio greater than 2, preferably 3, more preferably 5. Each of the grooves houses a generally flat and extended electrical resistance 24. A closure plate 20 covers each of the grooves 14 and the corresponding resistor. Each of the resistors 24 covers, depending on the width of the body, all of the longitudinal channels 6. They also cover them essentially totally along the length of the body 4.

Each of the two plates 20 extends transversely beyond the groove so as to have its lateral edges (corresponding to the longitudinal direction of the device) in contact with the body 4. To do this, holes 22 are made in order to receiving fixing screws (not shown) engaging with corresponding threaded bores 18 of the body 4.

The electrical resistances used are of the PTC (acronym for Positive Temperature Coefficient) type. Depending on the temperature, a balance between the heat flux generated by the PTC resistor and the heat dissipation towards the environment is created. The heat dissipation being made maximum by the arrangement of the electrical resistances along the fluid passage, the temperature of the ceramic component of the PTC resistor will decrease which will make it possible to increase the electrical power via an increase in intensity. current. The power absorbed by the fluid is therefore dependent on the ambient temperature and the temperature of the fluid and the flow rate of the pump circulating the fluid.

PTC resistors can run dry without the risk of breakdown. Without regulation and safety thermostat, they will automatically stabilize at their set temperature. In addition, these resistors can operate by being powered by different voltages (110 - 240 V) and frequencies (50 - 60 Hz).

PTC resistors have the advantage of being able to heat without regulating thermostat without causing breakdown, as it would be the case for standard type shielded electrical resistors. In addition, PTC electrical resistors can withstand both cold and hot electrical insulation tests, while standard electrical resistors are normally cold-tested because they can deteriorate when hot.

PTC resistors are self-regulating resistors, which increases the load per unit area without risk of overheating.

Compared to a standard electrical resistance, and for the same power, the overall size of the electrical resistance PTC is nearly 80% lower. This significant decrease in volume makes it possible to use elongated and flat electrical resistances and to insert them at the level of the solid element of the heating or preheating device described above.

In order to guarantee a minimum heat dissipation, a cap having a thermal insulation can be provided. This can cover the body of the device and is fixed by means of connection which have been arranged on the longitudinal ends of the body.

The heating body is in the shape of a rectangular parallelepiped. It can be made of aluminum, brass, stainless steel or any other heat conducting material depending on the intended application.

The interior volume of the solid element has been shaped so as to accommodate different channels, favoring the passage of the fluid in a predominantly longitudinal direction while maximizing heat exchanges with the electrical resistances PTC via the presence of several longitudinal channels communicating with each other. by transverse channels.

With regard to heat engines and, especially for vehicles and generators, one or more electrical PTC resistors are placed within the body and are powered by the battery in 12 or 24 VDC which allows, according to the application, to continue the heating when the device is no longer supplied with 110-230 V. These engines, or these generators, thus continue the reheating, this which allows the engine to arrive more quickly at the ideal operating temperature.

Depending on the various applications and fluids to be heated, the circulation pump is suitable.

Claims (15)

1. Device for heating a fluid (2), comprising:

   a heating body (4) having a through passageway (6, 8) for the fluid and provided with at least one groove (14) on its outer surface, said passageway comprising a plurality of parallel longitudinal channels (6) formed by drilling;

   at least one electrical resistance (24) housed in the at least one groove (14) of the heating body;

   at least one closure plate (20) of the at least one groove (14) overlying the at least one resistance (24);

   characterized in that
   the passageway (6, 8) passing through the heating body comprises a transverse channel (8) on at least one or both ends of the parallel longitudinal channels (6), ensuring a connection of said channels.
2. Heating device (2) according to claim 1, characterized in that the width of the at least one groove (14) is greater than its height, and this on the majority of its length, preferably the ratio between the width and height of the at least one groove is greater than 2, preferably 3, more preferably 5.
3. Heating device (2) according to one of claims 1 and 2, characterized in that the at least one resistance (24) is generally elongated and flat.
4. Heating device (2) according to one of claims 1 to 3, characterized in that the at least one closing plate (20) extends beyond the at least one electric resistances (24) so as to bear on the heating body (4).
5. Heating device (2) according to one of claims 1 to 4, characterized in that the at least one closing plate (20) is adapted to be fixed to the heating body (4) by screwing, preferably said at least one plate (20) comprises orifices (22) along its edges and the heating body comprises threaded bores (18) for receiving fastening screws arranged through said orifices.
6. Heating device (2) according to one of claims 1 to 5, characterized in that the at least one closing plate (20) is in contact with the at least one electrical resistance (24).
7. Heating device (2) according to one of claims 1 to 6, characterized in that the passageway (6, 8) passing through the heating body is substantially straight.
8. Heating device (2) according to one of claims 1 to 7, characterized in that at least one of the longitudinal channels (6) opens onto at least one face of the heating body (2), preferably on two opposite faces, the said face(s) being provided with plug(s) (12) for closing areas where said channels open, preferably the or each of said faces of the heating body on which at least one of the longitudinal channels (6) opens are provided, at areas where said channel(s) open(s), a connector (16) for hydraulic connection of the device.
9. Heating device (2) according to one of claims 1 to 8, characterized in that the groove (14) and the at least one electric resistance (24) extend transversely over all of the longitudinal channels (6).
10. Heating device (2) according to one of claims 1 to 9, characterized in that the at least one transverse channel (6) opens on a face of the heating body (2), said face being provided with plug(s) (10) for closing the area(s) where said at least one channel opens.
11. Heating device (2) according to one of claims 1 to 10, characterized in that the at least one transverse channel is produced by drilling.
12. Heating device (2) according to one of claims 1 to 11, characterized in that the longitudinal channels and the body are formed by extrusion and the transverse channels are formed by removing material, e.g. by drilling and/or machining.
13. Heating device (2) according to one of claims 1 to 12, characterized in that the heating body (4) is an integral solid block generally parallelepipedic.
14. Heating device (2) according to one of claims 1 to 13, characterized in that the heating body (4) comprises two grooves (14) on opposite sides of said body, the passageway extending between said faces and said grooves.
15. Heating device (2) according to one of claims 1 to 14, characterized in that the at least one electrical resistance (20) is of the PTC type.

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