EP3791117B1

EP3791117B1 - Electric heater

Info

Publication number: EP3791117B1
Application number: EP19729832.6A
Authority: EP
Inventors: Federico ZOPPAS; Giuliano ZANETTE; Maurizio Biasi; Giacomo DURIGON
Original assignee: IRCA SpA Industria Resistenze Corazzate e Affini
Current assignee: IRCA SpA Industria Resistenze Corazzate e Affini
Priority date: 2018-05-07
Filing date: 2019-05-07
Publication date: 2022-07-06
Anticipated expiration: 2039-05-07
Also published as: WO2019215602A1; IT201800005109A1; EP3791117A1

Description

Field of the invention

The present invention relates to an electric heater, in particular to an electric heater for a heat engine, e.g. a heat pump. The invention also relates to a heat engine provided with such a heater.

Background art

Electric heaters often are used to heat a fluid which flows in a pipe which belongs to the hydraulic circuit of a device.
In particular, electric heaters formed by a metal body in which one or two resistors are inserted, are advantageous. The metal body is also provided with a hole, delimited by a substantially continuous wall, in which the pipe to be heated is inserted.
Although this type of heaters has significant advantages, such heaters cannot however be used in the devices in which the hydraulic circuit cannot be opened. For example, such heaters cannot be used for pressurized circuits and circuits operating with fluids which are not to be exposed to the air, such as refrigerating circuits. WO2013170887A1 and WO2013046171 A1 disclose flow through heater devices comprising a tube for a fluid to be heated, a tubular heating element in thermal contact with the tube, wherein the tubular heating element comprises a casing provided with at least one tab portion wrapped around the tube.
DE2903743A1 and DE2942523A1 disclose other examples of flow through heater devices.

Summary of the invention

It is an object of the present invention to provide an electric heater which can be easily assembled with the pipe of a device.
It is an object of the invention in particular to provide such an electric heater for a heat engine, e.g. a heat pump.
These and other objects, which will be apparent in light of the present description, are achieved by means of an electric heater for heating a pipe, in particular a pipe of a heat engine such as e.g. a heat pump, the electric heater comprising at least one first electric resistor and a metal body,
wherein the metal body is provided with

a longitudinal housing, defining a first axis, which is open at the ends thereof and having a longitudinal opening along said first axis for inserting the pipe into the longitudinal housing;
at least one first longitudinal through hole, defining a second axis parallel to the first axis, said first electric resistor being inserted into the first through hole;
a first wall which separates the first electric resistor from the longitudinal housing, whereby the heat generated by the first electric resistor can be transmitted by conduction to the longitudinal housing;

The longitudinal end projections preferably are folded towards the exterior, i.e. they form said angle, also when the longitudinal end projections are moved close to each other, upon the insertion of the pipe.
The longitudinal end projections are folded towards the exterior of said longitudinal housing preferably so as to define a flaring for inserting the pipe into the housing. By providing the longitudinal end projections folded towards the exterior, the longitudinal end projections can advantageously be effectively grasped by a clamping element, in particular when the pipe is inside the longitudinal housing. Therefore, the longitudinal end projections can be retained by the clamping element. The longitudinal end projections preferably diverge towards the exterior of the longitudinal housing, at least in a first configuration. Optionally in a second configuration, the longitudinal projections can for example be diverging or parallel or converging when the longitudinal end projections have been moved close to each other upon the insertion of the pipe.
According to another aspect of the invention, a kit is provided, comprising the electric heater and at least one clamping element comprising two longitudinal clamping portions adapted to grasp the longitudinal end projections of the longitudinal housing when the pipe is inserted in the longitudinal housing. According to a further aspect of the invention, a heat engine is provided, in particular a heat pump, comprising the electric heater and at least one such a clamping element comprising two longitudinal clamping portions; wherein the heat engine comprises a pipe arranged in the longitudinal housing; and wherein the longitudinal clamping portions grasp the longitudinal end projections.
According to a further aspect of the invention, an assembly method is provided for assembling the electric heater with a pipe connected to a heat engine, in particular a heat pump;

wherein at least one clamping element is provided, comprising two longitudinal clamping portions adapted to grasp the longitudinal end projections of the longitudinal housing,
the assembly method comprising the steps of:
1. a) arranging the pipe in the longitudinal housing, causing the pipe to pass through said longitudinal opening;
2. b) moving the longitudinal projections close to each other;
3. c) retaining the longitudinal projections by means of said at least one clamping element.

The electric heater advantageously can be easily assembled with the pipe without removing the pipe from the heat engine to which it belongs. In other words, there is no need to open the hydraulic circuit to which the pipe belongs.
Indeed, the longitudinal housing advantageously is configured to receive the pipe, by passing it through the longitudinal opening.
For example, the longitudinal housing may receive the pipe by means of a movement of the metal body which is transverse to the longitudinal axis of the pipe. The electric heater is particularly adapted to be assembled with the pipe of a pressurized circuit and/or a circuit in which a fluid flows which is not to be exposed to the air, such as e.g. a refrigerating circuit. The fluid flowing in the pipe may in particular be a gas.
In general, the electric heater is particularly adapted to be assembled with the pipe of a heat engine, such as a heat pump.
The heater may for example, be assembled with a pipe which is upstream or downstream of the compressor of a heat pump, for example between the compressor and the condenser.
Further features and advantages of the invention will be more apparent in light of the detailed description of non-limiting embodiments.
The dependent claims describe particular embodiments of the invention.

Brief description of the drawings

Reference is made in the description of the invention to accompanying drawings, which are provided by way of a non-limiting example, in which:

Fig. 1 shows a perspective view of an electric heater according to the invention, in a first configuration;
Fig. 2 shows a front view of a component of the electric heater in Fig. 1;
Fig. 2A shows a part of Fig. 2;
Fig. 3 shows a perspective view of the electric heater according to the invention, in a second configuration;
Fig. 4 shows a front view of part of the electric heater in Fig. 3.

The same references in the drawings identify the same elements or components.

Description of embodiments of the invention

With reference to the figures, an electric heater 1 according to the invention is shown.
The electric heater 1 substantially is of the flow through heater (FTH) type.
The electric heater 1 is particularly adapted to heat a pipe 90, and more in particular a fluid, e.g. a gas, which flows in pipe 90. Pipe 90 may be for example, the pipe of a heat engine, e.g. a heat pump, configured to execute a cooling and/or heating cycle.
The electric heater 1 comprises a metal body 2 and two electric resistors 23, 33 inserted in the metal body 2. Alternatively, only one electric resistor is provided or more than two electric resistors can be provided.
The metal body 2 preferably is made of aluminum or aluminum alloy or of steel. The electric heater 1 can pass from a first configuration to a second configuration. In the first configuration, shown in particular in Fig. 1 and in Fig. 2, the electric heater 1 is configured to receive pipe 90, in particular by passing it through the longitudinal opening which is further described later.
Pipe 90 can for example be arranged in the electric heater 1 by moving the electric heater 1 transversely to the longitudinal axis of pipe 90.
In the second configuration, shown in particular in Fig. 3 and in Fig. 4, pipe 90 is accommodated and clamped, or blocked, in the electric heater 1, in particular in the metal body 2.
The metal body 2 indeed is provided with a longitudinal housing 11, i.e. with a longitudinal seat for pipe 90. Housing 11 substantially is a cavity or recess of the metal body 2. Housing 11 defines an axis X, which is a longitudinal axis of the electric heater 1. Axis X preferably is rectilinear or substantially rectilinear. Housing 11 is open at the ends thereof and has a longitudinal opening along axis X. The longitudinal opening is continuous and allows pipe 90 to be inserted into housing 11.
The longitudinal opening is laterally delimited by longitudinal end projections 12, 14 of the longitudinal housing 11, preferably two longitudinal end projections 12, 14. The longitudinal projections 12, 14 are spaced apart from each other and adapted to be moved close to each other after inserting the pipe 90 into the longitudinal housing 11.
According to the invention, the longitudinal end projections 12,14 are folded towards the exterior of the longitudinal housing 11. In other words, each longitudinal end projection 12, 14 is inclined with respect to the respective portion of wall 27, 37 of the longitudinal housing 11 which is proximal thereto. Each longitudinal end projection 12, 14 preferably forms an angle with the respective portion of wall 27, 37 of the longitudinal housing 11 which is proximal thereto, said angle preferably being other than 180°, preferably greater than or equal to 90°.
The longitudinal end projections 12, 14 preferably are inclined or folded towards the exterior of the longitudinal housing 11 so as to form a flaring to facilitate the insertion of the pipe 90 into the longitudinal housing 11. The longitudinal projections preferably diverge towards the exterior of the longitudinal housing 11, in particular at least or only in the first configuration. For example, the longitudinal projections 12, 14 define a respective plane C, D, and such planes C, D diverge towards the exterior of the longitudinal housing 11.
The longitudinal projections 12, 14 preferably are symmetrical, or substantially symmetrical, with respect to a symmetry plane K which includes the axis X, in particular on which the axis X lies.
The symmetry plane K preferably, but not exclusively, is the symmetry plane of the whole electric heater 1. In other words, it is preferable that the electric heater 1 is symmetrical, or substantially symmetrical, with respect to the symmetry plane K. The metal body 2 is also provided with two longitudinal through holes 21, 31, which define a respective axis A, B, which is parallel to the axis X. The number of longitudinal through holes preferably is equal to the number of electric resistors with which the electric heater is provided. The through holes 21, 31 are delimited by a respective inner surface 20, 30 of the metal body 2. The inner surfaces 20, 30 preferably are cylindrical or substantially cylindrical. The inner surfaces 20, 30 preferably are continuous or substantially continuous.
Each electric resistor 23, 33 is inserted in a respective through hole 21, 31. Each electric resistor 23, 33 preferably has two end portions 24, 34 which come out of the respective through hole 21, 31. Such end portions 24, 34 comprise pins for connecting the electric resistors 23, 33 to a power supply source (not shown). The electric resistors 23, 33 preferably are equal to each other.
Each electric resistor 23, 33 preferably comprises at least one resistive element, for example one or more resistive wires. The at least one resistive element is arranged in an insulating material, e.g. magnesium oxide. The insulating material preferably is directly in contact with the inner surface 20, 30 of the respective through hole 21, 31.
Alternatively, the electric resistors 23, 33 are sheathed resistors, also known as sheathed resistances, i.e. provided with a metal sheath or casing. In this case, the inner surfaces 20, 30 of the metal body 2 are in contact, preferably completely and/or directly in contact, with the outer surface of the metal sheath of the respective electric resistor 23, 33.
The metal body 2 comprises two walls 22, 32, which separate a respective electric resistor 23, 33 from the longitudinal housing 11. Thereby, the heat generated by the electric resistors 23, 33 can be transmitted by conduction to the longitudinal housing 11.
A curved portion 27, 37 extends from each wall 22, 32. Each curved portion 27, 37 is joined with a respective longitudinal projection 12, 14. Each longitudinal projection 12, 14 is inclined with respect to the curved portion 27, 37 which is proximal thereto. The aforesaid curved portions 27, 37 are portions of wall of the longitudinal housing 11 and preferably are concave towards the interior of the longitudinal housing 11. A bottom portion 15, or central portion, of the housing 11 is provided between the walls 22, 32. The bottom portion 15 preferably is opposite to the longitudinal opening of the housing 11. Each wall 22, 32 preferably is joined with the bottom portion 15 by a respective joining portion 26, 36 (Fig. 2A) or joining portion of wall.
The bottom portion 15 preferably has a smaller thickness than the thickness of each wall 22, 32 and preferably also than the thickness of each joining portion 26, 36.
The joining portions 26, 36 preferably have a constant, or substantially constant, thickness (indicated in with reference "F" Fig. 2A). It instead is preferable that the bottom portion 15 has a decreasing thickness from the sides towards axis X or more in particular, towards a middle axis thereof, parallel to axis X and contained within the symmetry plane K. In the first configuration, the bottom portion 15 preferably has a substantially flat inner surface 18 and an outer surface 19 which is convex towards the inner surface 18, i.e. concave towards the exterior of the electric heater 1, in particular towards the exterior of the metal body 2. The inner surface 18 preferably is substantially perpendicular to the symmetry plane K. The outer surface 19 is an outer surface of the metal body 2. The bottom portion 15 preferably has a minimum thickness "E" which is equal, or about equal, to a value between 1/10 and 2/3 of thickness "F" of each joining portion 26, 36. The minimum thickness "E" of the bottom portion 15 for example is equal, or about equal, to 1/2 of thickness "F" of each joining portion 26, 36.
The inner surface 18 of the bottom portion 15 is part of the inner surface 10 (Fig. 2A) of the housing 11, i.e. it is a portion of the inner surface 10 of housing 11.
The inner surface 10 of the housing 11 also comprises two portions of surface 25, 35 between which the portion of surface 18 extends. The portions of surface 25, 35 are concave towards the interior of the housing 11. A part of the portion of surface 25 is opposite to a part of the inner surface 20. Similarly, a part of the portion of surface 35 is opposite to a part of the inner surface 30.
Another portion of surface 28, 38 extends from each portion of surface 25, 35. Each portion of surface 28, 38 has a different concavity from the portion of surface 25, 35 adjacent thereto. In particular, the portions of surface 28, 38 are convex towards the interior of housing 11, i.e. concave towards the exterior of housing 11. The portions of surface 28, 38 join the portions of surface 25, 35 with a respective portion of surface 29, 39. The portions of surface 29, 39 are the inner surfaces of the longitudinal projections 12, 14 and preferably are parallel to plane C and to plane D, respectively.
The heater 1 is designed in function of pipe 90, which is intended to be arranged in the housing 11. The pipe 90 intended to be received in the housing 11 preferably is made of metal, for example made of steel.
The heater 1 preferably is designed to house a pipe 90 having a cylindrical, or substantially cylindrical, outer surface.
The radius of curvature of the portions of surface 25, 35 is substantially equal to the radius of curvature of the outer surface of the pipe 90. Moreover, it is preferable that the minimum distance between the portions of surface 28, 38, which is the minimum width "W" (Fig. 2) of the longitudinal opening, has a value which is equal, or about equal to, a value between twice and 3 times the outer radius of pipe 90. For example, the minimum width "W" of the longitudinal opening may have an extension which is equal, or about equal, to twice or 2.5 times the outer radius of pipe 90.
The longitudinal projections 12, 14 are moved close to each other to pass from the first to the second configuration, as shown in a comparison between Fig. 2 and Fig. 4. The longitudinal projections 12, 14 face each other in the second configuration. Preferably, the longitudinal projections 12, 14 are substantially parallel to each other in the second configuration. In particular, the portions of surface 29, 39 face each other and preferably are parallel, or substantially parallel, to each other. Preferably, the longitudinal projections 12, 14 are spaced apart from each other in the second configuration. In particular, the portions of surface 29, 39 are spaced apart from each other. The minimum distance "G" between the longitudinal projections 12, 14, in particular between the portions of surface 29, 39, preferably is equal to a value between 1/10 and 1 with respect to the outer radius of pipe 90.
There is a deformation of the bottom portion 15 in the switch from the first to the second configuration. In particular, the inner surface 18 takes on a curved shape, concave towards the interior, with substantially the same radius of curvature as the portions of surface 25, 35. Also the outer surface 19 preferably is deformed. For example, the outer surface 19 takes on a flat, or substantially flat, shape. The bottom portion 15 preferably, but not exclusively, is the only part which is deformed. Moreover, there is a rotation of the electric resistors 23, 33 about axis X in the switch from the first to the second configuration. The axes A, B and X preferably are mutually coplanar in the second configuration.
The surfaces 18, 25, 35 advantageously adhere to the outer surface of pipe 90 in the second configuration.
A clamping element 80 (Figures 3 and 4) may grasp the longitudinal projections 12, 14 by means of two longitudinal clamping portions 81, 82 when the electric heater 1 is in the second configuration with the pipe 90 arranged in the housing 11.
In particular, the inner surfaces of the clamping portions 81, 82 are in contact with the outer surfaces 49, 59 of the longitudinal projections 12, 14 in order to retain the longitudinal projections 12, 14. In particular, the outer surfaces 49, 59 of the longitudinal projections 12, 14 are opposite to the portions of surface 29, 39, respectively.
Preferably, the clamping element 80has a length which is equal, or about equal, to the length along axis X of the longitudinal projections 12, 14.
The clamping element 80 preferably is of elastic type, i.e. elastically deformable. For example, the clamping element 80 is made of harmonic steel or other suitable elastic material.
The clamping element 80 preferably comprises an elastically deformable curved portion 83 to move the clamping portions 81, 82 away from each other. Thereby, the longitudinal projections 12, 14 are retained by an elastic return force.
The metal body 2 can advantageously adapt to possible heat expansions of pipe 90 due in particular to the elasticity of the clamping element 80 and given that the longitudinal projections 12, 14 are provided spaced apart from each other.
The clamping element 80 may be part of a kit which also comprises the electric heater 1.
The electric heater 1 may advantageously be assembled with a pipe 90 which is upstream or downstream of the compressor of a heat pump, for example between the compressor and the condenser.
To assemble the electric heater 1 with a pipe 90 connected to a heat engine, i.e. a pipe of a heat engine, in particular a heat pump, an assembly method may be executed, comprising the steps of:

a) arranging the pipe 90 in the longitudinal housing 11, causing pipe 90 to pass through the longitudinal opening of the longitudinal housing 11, i.e. through the longitudinal projections 12, 14;
b) moving the longitudinal projections 12, 14 close to each other;
c) retaining the longitudinal projections 12, 14 by means of the clamping element 80.

The invention also comprises a heat engine, in particular a heat pump, comprising the electric heater 1 and at least one clamping element 80, preferably one clamping element 80, comprising two longitudinal clamping portions 81, 82; wherein the heat engine comprises a pipe 90 arranged in the longitudinal housing 11 and wherein the longitudinal clamping portions 81, 82 grasp the longitudinal end projections 12, 14.

Claims

An electric heater (1) for heating a pipe (90), in particular a pipe of a heat pump, comprising at least a first electric resistor (23) and a metal body (2),
wherein the metal body (2) is provided with
- a longitudinal housing (11), defining a first axis (X), which is open at the ends thereof and having a longitudinal opening along said first axis (X) for inserting the pipe (90) into the longitudinal housing (11);

- at least one first longitudinal through hole (21), defining a second axis (A) parallel to the first axis (X), said first electric resistor (23) being inserted into the first through hole (21);

- a first wall (22) which separates the first electric resistor (23) from the longitudinal housing (11), whereby the heat generated by the first electric resistor (23) can be transmitted by conduction to the longitudinal housing (11);

wherein said longitudinal opening is laterally delimited by longitudinal end projections (12, 14) of the longitudinal housing (11), spaced apart from each other and adapted to be moved close to each other upon inserting the pipe (90) into the longitudinal housing (11);

characterized in that said longitudinal end projections (12, 14) are folded towards the exterior of said longitudinal housing (11).
An electric heater (1) according to claim 1, wherein said longitudinal end projections (12, 14) diverge towards the exterior of said longitudinal housing (11).
An electric heater according to any one of the preceding claims, wherein each longitudinal end projection (12, 14) is inclined with respect to the respective portion of wall (27, 37) of the longitudinal housing (11) which is proximal thereto.
An electric heater (1) according to any one of the preceding claims, wherein said longitudinal end projections (12, 14) are symmetrical with respect to a symmetry plane (K) which includes said first axis (X).
An electric heater (1) according to any one of the preceding claims, wherein the longitudinal housing (11) comprises a bottom portion (15) having a decreasing thickness towards the first axis (X).
An electric heater (1) according to any one of the preceding claims, wherein the bottom portion (15) of the housing (11) has a substantially flat inner surface (18) and/or an outer surface (19) which is convex towards the inner surface (18).
An electric heater (1) according to any one of the preceding claims, wherein the metal body (2) is provided with a second longitudinal through hole (31) defining a third axis (B) which is parallel to the first axis (X);
wherein there is provided a second electric resistor (33) inserted into the second through hole (31);

and wherein a second wall (32) is provided, which separates the second electric resistor (33) from the longitudinal housing (11), whereby the heat generated by said second electric resistor (33) can be transmitted by conduction to said longitudinal housing (11).
An electric heater according to claim 7, wherein a respective portion of wall (27, 37) of the longitudinal housing (11) extends from the first wall (22) and from the second wall (32), each portion of wall (27, 37) preferably being curved;
wherein each portion of wall (27, 37) is joined with a respective longitudinal end projection (12, 14);

and wherein each longitudinal end projection (12, 14) is inclined with respect to the portion of wall (27, 37) which is proximal thereto.
An electric heater (1) according to claim 7 or 8, wherein the bottom portion (15) of the housing (11) is arranged between the first wall (22) and the second wall (32), and preferably wherein the bottom portion (15) has a smaller thickness than the thickness of the first wall (22) and than the thickness of the second wall (32).
An electric heater (1) according to claim 7, 8 or 9, wherein the bottom portion (15) of the housing (11) is arranged between a first joining portion (26) and a second joining portion (36), which are adjacent to the first wall (22) and to the second wall (32), respectively, and preferably wherein the bottom portion (15) has a smaller thickness than the thickness of the first joining portion (26) and than the thickness of the second joining portion (36).
A kit comprising an electric heater (1) according to any one of the preceding claims, and at least one clamping element (80) comprising two longitudinal clamping portions (81, 82) adapted to grasp the longitudinal end projections (12, 14) of the longitudinal housing (11) when the pipe (90) is inserted into the longitudinal housing (11), and preferably wherein said at least one clamping element (80) is elastic.
A heat engine, in particular a heat pump, comprising an electric heater (1) according to any one of claims 1 to 10, and at least one clamping element (80) comprising two longitudinal clamping portions (81, 82),
wherein the heat engine comprises a pipe (90) arranged in the longitudinal housing (11) and wherein the longitudinal clamping portions (81, 82) grasp the longitudinal end projections (12, 14).
An assembly method for assembling the electric heater (1) according to any one of claims 1 to 10, with a pipe (90) connected to a heat engine, in particular a heat pump,
wherein at least one clamping element (80) is provided, comprising two longitudinal clamping portions (81, 82) adapted to grasp the longitudinal end projections (12, 14) of the longitudinal housing (11),

the assembly method comprising the steps of:
a) arranging the pipe (90) in the longitudinal housing (11), causing the pipe (90) to pass through said longitudinal opening;

b) moving the longitudinal projections (12, 14) close to each other;

c) retaining the longitudinal projections (12, 14) by means of said at least one clamping element (80).