EP4351274A1 - Heating apparatus with inertia heating element - Google Patents

Abstract

The invention relates to a heating appliance (10) comprising: an outer casing (12) and an electric heating element (14) received inside said outer casing, the outer casing comprising a substantially vertical facade (17), the electric heating element comprising: a body (30), formed of a first material with thermal inertia; and an electrical resistance (32) inserted inside said body; the body of the electric heating element comprising a main face (36), substantially facing the facade, and an opposite face (38) substantially parallel to said main face. The main face is inclined by a non-zero angle of inclination (α) relative to the vertical.

Description

The present invention relates to a heating appliance, of the type comprising an outer casing and an electric heating element received inside said outer casing, the outer casing comprising a substantially vertical facade, the electric heating element comprising: a body , made of a material with thermal inertia; and an electrical resistance inserted inside said body; the body of the electric heating element comprising a main face, substantially facing the facade, and an opposite face substantially parallel to said main face

The invention applies particularly to heating devices comprising a dry inertia heating element. Such a device is described in particular in the document FR2991845 in the name of the Applicant.

Typically, such a heating element comprises a body formed of a dense material with high radiative properties, such as cast iron, glass, ceramic or concrete.

In order to limit the weight of the heater, it is preferable to reduce the size of the heating element as much as possible for a given heating power. This results in heating elements reaching very high surface temperatures. For safety reasons, however, it is necessary to contain these temperatures below a threshold.

Conventionally, heaters comprising a dry inertia heating element operate both by convection and by radiation. More specifically, a flow of air circulates from the bottom to the top in the heater, around the heating element. This flow of air which is loaded with calories helps to limit the surface temperature of the heating element.

In addition, the heating element diffuses infrared radiation towards the external envelope of the device, in particular towards the facade, which itself increases in temperature and is then itself able to diffuse infrared radiation.

For better efficiency of radiant heating, it is preferable that the temperature of the facade be as uniform as possible. For this purpose, certain devices are equipped with a specific front heating element, of the screen-printed resistance type.

For safety reasons, it is also necessary to avoid the appearance of areas that are too hot on said facade.

The present invention aims to improve the homogeneity of a surface temperature of the heating element, and possibly of the facade, of such a heating device.

To this end, the subject of the invention is a heating device of the aforementioned type, in which the main face is inclined by a non-zero angle of inclination relative to the vertical.

• la face principale du corps est inclinée de sorte qu'une extrémité inférieure de ladite face principale soit plus proche de la façade qu'une extrémité supérieure de ladite face principale ;
• l'angle d'inclinaison est compris entre 5° et 45°, préférentiellement compris entre 5 et 25°, plus préférentiellement compris entre 10° et 20° ;
• le corps de l'élément chauffant électrique est traversé par une pluralité de perforations reliant la face principale et la face opposée ;
• une perforation représente une surface comprise entre 1% et 5% d'une surface de la face principale ; et la totalité des perforations représente une surface comprise entre 10% et 50% d'une surface de la face principale ;
• le matériau à inertie thermique du corps est choisi parmi la fonte, le verre, la céramique, les polymères inorganiques et le béton ;
• la façade de l'enveloppe externe est formée d'un autre matériau à inertie thermique, préférentiellement choisi parmi : les métaux tels que l'acier, le verre, la céramique, la pierre naturelle et les polymères inorganiques.

According to other advantageous aspects of the invention, the heating appliance comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

• the main face of the body is inclined so that a lower end of said main face is closer to the facade than an upper end of said main face;
• the angle of inclination is between 5° and 45°, preferably between 5 and 25°, more preferably between 10° and 20°;
• the body of the electric heating element is crossed by a plurality of perforations connecting the main face and the opposite face;
• a perforation represents a surface of between 1% and 5% of a surface of the main face; and all of the perforations represent a surface area of between 10% and 50% of a surface area of the main face;
• the thermal inertia material of the body is chosen from cast iron, glass, ceramic, inorganic polymers and concrete;
• the facade of the external envelope is formed of another material with thermal inertia, preferably chosen from: metals such as steel, glass, ceramic, natural stone and inorganic polymers.

• [Fig 1] la figure 1 est une vue schématique, en section, d'un appareil de chauffage selon un mode de réalisation de l'invention, comprenant un élément chauffant électrique ; et
• [Fig 2] la figure 2 est une vue de face de l'élément chauffant électrique de l'appareil de chauffage la figure 1.

The invention will be better understood on reading the description which follows, given solely by way of non-limiting example and made with reference to the drawings in which:

• [ Figure 1 ] there figure 1 is a schematic sectional view of a heating appliance according to one embodiment of the invention, comprising an electric heating element; And
• [ Figure 2 ] there figure 2 is a front view of the electric heating element of the heater figure 1 .

There figure 1 is a schematic view, in section, of a heating device 10 according to one embodiment of the invention.

The apparatus 10 comprises an outer casing 12 and an electric heating element 14, received inside said outer casing. It is considered that the device 10 further comprises a temperature sensor 15 and a thermostat 16.

The outer envelope comprises a front 17 and a rear cover 18 assembled together, defining an internal space 20. In an installed position of the device 10, as shown on the figure 1 , the facade 17 is arranged in a substantially vertical manner.

In the embodiment shown, the facade 17 is substantially flat. Other non-perfectly planar shapes are also possible.

Preferably, the facade 17 is formed of a material with thermal inertia, for example a metal, a glass, a ceramic, a natural stone or an inorganic polymer. For a metal facade 17, the metal chosen is preferably steel.

The rear cover comprises in particular a lower wall 22 and an upper wall 24. In the present description, the terms “lower” and “upper” are understood in relation to the vertical, the device 10 being in the installed position.

Each of the lower and upper walls is pierced with openings 26.

The electric heating element 14 is shown from the front on the figure 2 . The heating element 14 comprises a body 30 and an electrical resistance 32.

The body 30 is formed of a material with thermal inertia, for example cast iron.

The electrical resistance 32, shown in dotted lines on the figures 1 And 2 , is inserted inside the body 30 in thermal contact with said body. The electrical resistance 32 extends between two ends 34, projecting relative to the body 30. The ends 34 are able to be connected to a source of electrical energy.

The body 30 of the electric heating element comprises a main face 36, substantially facing the facade 17 of the envelope 12, as well as an opposite face 38 substantially parallel to the main face.

The body 30 has a substantially constant thickness 40 between the main face 36 and the opposite face 38. Preferably, as in the embodiment shown, the body 30 has a substantially parallelepiped shape, the main 36 and opposite faces 38 being generally planar .

The main face 36 extends between a lower end 42 and an upper end 44.

The heating element 14 is connected to the envelope 12 so that the main face 36 of the body is inclined by a non-zero angle α relative to the vertical, in the installed position.

Preferably, the orientation of the inclination of the heating element 14 is such that the lower end 42 of the main face is closer to the facade 17 than the upper end 44 of said main face. According to a variant not shown, the inclination is such that the upper end 44 is closest to the facade.

Thus, the main face 36 of the body 30 is slightly oriented upwards and the opposite face 38 is slightly oriented downwards. In addition, the axis 48 of each perforation 46 is inclined by the angle α relative to the horizontal.

Preferably, the angle of inclination is between 5° and 45°, more preferably between 5° and 25°, even more preferably between 10° and 20°.

Preferably, as in the embodiment shown, the body 30 comprises a plurality of through perforations 46, extending between the main face 36 and the opposite face 38. More preferentially, the perforations are distributed substantially regularly over a set of the main face 36.

Each perforation extends along an axis 48 substantially perpendicular to the main faces 36 and opposite faces 38.

In the embodiment shown, perpendicular to the axis 48, each perforation 46 has an oval or oblong shape. Other shapes, such as a round, square, rectangle, hexagonal or octagonal shape, can also be used.

Preferably, a perforation 46 represents a surface area of between 1% and 5% of a surface area of the main face 36; and all of the perforations 46 represent a surface area of between 10% and 50% of a surface area of the main face 36.

According to a variant not shown, the body of the heating element is solid and devoid of perforations on the main face and the opposite face.

The temperature sensor 15 is arranged in the lower part of the device 10, for example at the lower wall 22 of the rear cover.

The thermostat 16 is connected to the sensor 15. The thermostat 16 is for example configured to control an electrical supply of the resistance 32 of the heating element 14, so as to interrupt said electrical supply if a temperature measured by the sensor 15 exceeds a temperature setpoint memorized by the thermostat.

A method of operating the apparatus 10 will now be described. We consider that the device 10 is in the installed position, within a room to be heated, and that the ends 34 of the resistance 32 are connected to a source of electrical energy.

The resistance 32 is supplied with electricity, leading to the heating of the body 30 by thermal conduction. The air received in the internal space 20 of the envelope 12 heats up on contact with said body 30, generating a convection phenomenon in which a first flow 50 of air circulates between the openings 26 of the lower wall 22 towards the openings of the upper wall 24.

Compared to a vertical surface, the downward inclination of the opposite face 38 increases the contact surface between said opposite face and the first flow 50 coming from the lower wall 22. The convection phenomenon is thus improved.

In addition, the perforations 46, crossed by said first flow 50, improve the renewal of the air near said opposite face 38, as well as near the main face onto which the perforations 46 open.

The heating element 14, thus effectively cooled over its entire exterior surface by the first flow 50 of air, has a more uniform temperature on said exterior surface than in the absence of inclination or perforations.

In addition, heat transfer by radiation takes place between the main face 36 of the body 30 towards the facade 17. A second 52 and a third 54 air flow are generated by convection along said facade 17, respectively in the internal space 20 and outside the device 10. The facade 17 being vertical, the air arriving in contact with the top of the facade is hotter than the air in contact with the bottom of said facade. The heat transfer from the top of the facade 17 to the air is therefore less efficient than from the bottom.

In the advantageous case where the lower end 42 of the main face is closer to the facade 17 than the upper end 44, the body 30 transfers greater thermal power towards the bottom of the facade 17 than towards the top. This phenomenon compensates for the differences in heat transfer efficiency indicated above with the second 52 and third 54 air flows. The temperature of the facade 17 is therefore more uniform.

EXAMPLE

A comparison was made between four heaters designated by the letters A, B, C and D.

Device A corresponds to device 10 described above, with a heating element 14 comprising perforations 46 and whose main face 36 is inclined at an angle α relative to the vertical.

In the example used, the facade 17 is made of steel, the body 30 is made of cast iron, the angle α is equal to 23°, the perforations 46 have a round shape with a diameter of 18 mm.

Device B is similar to device A, the difference being that the heating element does not have perforations, said heating element however being inclined by the angle α.

Device C is similar to device A, one difference being that the main face of the heating element is arranged vertically, said heating element however comprising the same perforations 46 as that of device A.

Device D - or control device - is similar to devices A, B and C but includes a heating element without perforations and arranged vertically.

The heating elements of devices A, B, C, D are supplied with electricity under similar conditions, with an electrical power of 800 W in each case. After stabilization, a hottest zone is identified on the facade 17 and the corresponding temperature Tf _max is recorded. In addition, an average temperature Tf _avg on the facade is estimated using an infrared detector.

In addition, a hottest zone is identified on the surface of the body 30 and the corresponding temperature Tc _max is recorded. In addition, an average temperature Tc _avg on the body surface is estimated using an infrared detector.

[Table 1] The temperatures obtained are detailed in table 1 below:

Table 1 _Max Tf (°C) _Average Tf (°C) Tc _max (°C) _Average Tc (°C) Device A 55 40 216 205 Device B 66 42 256 235 Device C 41 35 255 240 Device D 44 36 257 239

The comparison of devices B (inclined and non-perforated heating element) and D (vertical and non-perforated heating element) shows that the inclination of the heating element makes it possible to increase the average temperature of the facade of the device, without impact significant on the average and maximum temperatures of the heating element.

On the other hand, the increase in the facade temperature linked to the inclination of the heating element is not uniform, as illustrated by the significant difference between Tf _max and Tf _avg for device B.

The comparison of devices C (vertical and perforated heating element) and D (vertical and non-perforated heating element) shows that the perforation of the heating element alone has no significant influence on the temperatures of said heating element and the facade , the temperatures Tf _max , Tf _avg , Tc _max and Tc _avg being in fact comparable for devices C and D.

Comparison of devices A (inclined and perforated heating element) and D (vertical and non-perforated heating element) shows that the inclination of the heating element combined with its perforation makes it possible to increase the temperature of the facade more evenly, as illustrated by the reduced difference between Tf _max and Tf _avg for device A.

In addition, the combination of the inclination and the perforation of the heating element makes it possible to reduce the temperature of said heating element for the same electrical power supplied, as shown by the comparison of Tc _max and Tc _avg between the device A d on the one hand and devices B, C and D on the other hand.

The configuration of device A therefore makes it possible to obtain a warm facade and a more uniform temperature, without hot spots, with a lower heating element temperature.

In this configuration, it is thus possible to increase the electrical power of the heating element for the same volume of the external envelope of the device, without exceeding the manufacturing constraints.

This configuration also avoids the addition of a screen-printed resistor on the front of the device.

Claims (9)

Heating apparatus (10) comprising an outer casing (12) and an electric heating element (14) received inside said outer casing, the outer casing comprising a substantially vertical facade (17), the electric heating element comprising: a body (30), formed of a first material with thermal inertia; and an electrical resistance (32) inserted inside said body; the body of the electric heating element comprising a main face (36), substantially facing the facade, and an opposite face (38) substantially parallel to said main face; the heating device being characterized in that the main face is inclined by a non-zero angle of inclination (α) relative to the vertical. Heating apparatus according to claim 1, wherein the main face (36) of the body is inclined so that a lower end (42) of said main face is closer to the facade than an upper end (44) of said main face. Heating apparatus according to claim 1 or claim 2, in which the angle of inclination (α) is between 5° and 45°, preferably between 5 and 25°, more preferably between 10° and 20°. Heating apparatus according to one of the preceding claims, in which the body (30) of the electric heating element is crossed by a plurality of perforations (46) connecting the main face and the opposite face. Heating apparatus according to claim 4, in which a perforation (46) represents a surface area of between 1% and 5% of a surface area of the main face (36); and all of the perforations (46) represent a surface area of between 10% and 50% of a surface area of the main face. Heating apparatus according to one of the preceding claims, in which the first material with thermal inertia is chosen from cast iron, glass, ceramics, inorganic polymers and concrete. Heating device according to one of the preceding claims, in which the facade of the external envelope is formed of a second material with thermal inertia. Heating apparatus according to claim 7, wherein the second thermally inert material is chosen from metals, glass, ceramics, natural stone and inorganic polymers. A heating apparatus according to claim 8, wherein the second thermally inert material is steel.

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