Heating System for Heating a Fluid Medium

Abstract

The present invention relates to a heating system for heating a fluid medium, said heating system comprises a carrier unit and a heating unit, with the carrier unit having a surface comprising at least a plane portion being at least substantially normal to a longitudinal axis and an at least part-circularly shaped groove extending from said carrier unit and wound about the longitudinal axis, and the heating unit having a heating element at least partially arranged in said groove of said carrier unit. In the inventive heating system, the groove extends at least partially helically about the longitudinal axis. The present invention further relates to a heated conveyor pump for conveying and heating a fluid medium, said pump comprises a drive unit, a pump housing and the inventive heating system. The heating system is coupled to the pump housing with the groove extending into the pump housing in a manner such that the size of the cross-section of the groove decreases in the flow direction of the conveyed fluid medium.

Claims

1. A heating system for heating a fluid medium, said heating system comprising: a disk-like carrier unit and a heating unit; the carrier unit having a central axis, a groove extending at least partially around the central axis and a bottom; and the heating unit having a heating element at least partially arranged in said groove of said carrier unit; characterized in that at least a section of the groove bottom has an inclination with an inclination angle >0.

2. The heating system according to claim 1, characterized in that the gradient of the inclination of the groove bottom is at least partially continuous.

3. The heating system according to claim 1, characterized in that the gradient of the inclination of the groove bottom is at least partially discontinuous.

4. The heating system according to claim 1, characterized in that the bottom of the groove has at least two sections the inclination angles of which are unequal.

5. The heating system according to claim 1, characterized in that the bottom of the groove has at least two sections the inclination angles of which are equal.

6. The heating system according to claim 4, characterized in that the sections follow one after the other.

7. The heating system according to claim 4, characterized in that the sections are separated from each other.

8. The heating system according to claim 1, characterized in that the groove bottom extends at least partially helically around the central axis.

9. The heating system according to any of claim 1, characterized in that the heating element has at least one cranked end.

10. The heating system according to claim 9, characterized in that the heating element has two cranked ends wherein the degree of offsetting of the cranked ends is preferably different.

11. The heating system according to claim 9, characterized in that an inwards direction is defined as the extension direction of the groove from the carrier unit projected onto the central axis and the at least partially part-circularly shaped tubular heating element is arranged in the groove with the cranked end positioned at the largest extension of the groove in the inwards direction.

12. The heating system according to any of claim 1, characterized in that a size of the cross-section of the groove continuously decreases at least partially, wherein the at least partially part-circularly shaped tubular heating element is arranged in the groove with the cranked end positioned at least approximately at the largest cross-section of the groove.

13. The heating system according to any of claim 1, characterized in that the carrier unit is provided with a protective coating, at least at that surface facing away from the heating element.

14. The heating system according to any of claim 1, characterized in that the carrier unit comprises or consists of a heat conducting material, like aluminium or an aluminium alloy.

15. A heated conveyor pump for conveying and heating a fluid medium, said pump comprising: a drive unit, a pump housing and a heating system, characterized in that the heating system is defined according to any of claim 1.

16. The heating system according to claim 5, characterized in that the sections follow one after the other.

17. The heating system according to claim 5, characterized in that the sections are separated from each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1: is a perspective view to a heated conveyor pump according to the present invention;

[0038] FIG. 1a: is an exploded view to the heated conveyor pump according to FIG. 1;

[0039] FIG. 2: is a perspective view to a heating system according FIG. 1;

[0040] FIG. 3: is a plan view to the heating system according to the present invention;

[0041] FIG. 3a: is a sectional view along line A-A in FIG. 3;

[0042] FIG. 3b: is a sectional view along line B-B in FIG. 3;

[0043] FIG. 4: is a plan view to the heating system according to FIG. 3, including the pump housing;

[0044] FIG. 4a: is a sectional view along line P-P in FIG. 4;

[0045] FIG. 5: is a plan view to the heating system according to FIG. 3;

[0046] FIG. 5a: is a sectional view along line D-D in FIG. 5;

[0047] FIG. 5b: is a sectional view along line E-E in FIG. 5;

[0048] FIG. 5c: is a detailed view to a safety device of FIG. 5b;

[0049] FIG. 6: is a further embodiment of a heating system according to the present invention;

[0050] FIG. 7: is a detailed view to a further embodiment of a heating system according to the present invention;

[0051] FIG. 8a: is a plan view to a further embodiment of a heating system according to the invention; and

[0052] FIG. 8b: is a sectional view along line F-F in FIG. 8a.

DETAILED DESCRIPTION

[0053] FIG. 1 shows a heated conveyor pump 1 according to the present invention. Heated conveyor pump 1 includes a drive unit 10, like an electric motor, a pump housing 50 and a heating system 100, which are arranged coaxially along a common central longitudinal axis A.

[0054] As can be seen in FIG. 1a, pump housing 50 has a cylindrical wall 52 with an inlet opening facing towards heating system 100, and an outlet branch 54 extending radially from cylindrical wall 52. The inlet opening is covered by heating system 100. Heating system 100 has a central through hole which forms an inlet branch 56. In pump housing 50, a pump wheel 58 is arranged for conveying the fluid medium from inlet branch 56 to outlet branch 54.

[0055] As shown in FIGS. 1, 1a and 2, heating system 100 has a disk-like carrier unit 120 and a heating unit 130 including a heating element 132, two safety devices B, C and to connecting device D for connecting heating element 132 and safety devices B, C to a power source and a control unit.

[0056] Carrier unit 120, which has the shape of a circular or round blank or disc, respectively, has a circular plane portion 121 surrounded by a rim 122 extending approximately vertically from plane portion 121 towards pump housing 50, for surrounding and sealing the inlet opening in pump housing 50 (cf. FIGS. 3, 3a, 4a). Circular plane 121 of carrier unit 120 has a central through hole arranged coaxially to central longitudinal axis A, which forms inlet branch 56.

[0057] In circular plane portion 121, a ring-shaped groove 140 is arranged, which coaxially surrounds the central through hole in carrier unit 120 and the central longitudinal axis A. Groove 140 extends from circular plane portion 121 towards pump housing 50. In the mounted state of heated conveyor pump 1, groove 140 extends into pump housing 50.

[0058] Groove 140 is approximately V-shaped with straight legs and a preferably rounded groove base or groove bottom 140a with a diameter that at least approximately corresponds to the height of the cross-section of heating element 132 (cf. FIG. 3a). However, the diameter of the groove bottom 140a may also be smaller than the height of the cross-section of heating element 132. Groove 140 has a helical sector, in which the depth of groove 140, and thus, the size of its cross-section, continuously decreases in counter-clockwise direction, or in the direction of rotation of pump wheel 58, and a flat sector of constant depth (cf. FIGS. 4, 4a).

[0059] Heating element 132 is ring-shaped, with a diameter corresponding to the diameter of ring-shaped groove 140, and has a cranked first end 132a and a straight second end 132b. The cross-section of heating element 132 according to FIG. 3 is V-shaped and corresponds to the cross-section of groove 140.

[0060] However, it is also possible to provide a V-shaped groove with a base or bottom 140a having a straight portion to which the legs are coupled by smaller radii. In all cases, it is of importance that the shape of the heating element at least approximately matches the shape of the groove.

[0061] Heating element 132 is not only circularly shaped, but is also formed as a helix along central longitudinal axis A. That means the circular portion of heating element 132 extends along a circular screw line, with a difference in height between the first end 132a and the second end 132b, with the flat upper surface of second end 132b exceeding the flat upper surface of first end 132a about height h. Height h may be selected from zero up to 25 mm (cf. FIGS. 3, 3a, 4a).

[0062] Heating element 132 is arranged in groove 140 such that cranked end 132a is positioned in the deepest portion of the helical sector of groove 140, second end 132b is positioned in the flat sector, and the helical portion of heating element 132 extends through the helical sector of groove 140.

[0063] The flow channel in pump housing 50 extends along the inner surface of pump housing 50 and its size is defined by width B and its height. Due to the helical shape of groove 140 or the groove bottom 140a the height of the flow channel increases from a first height h1 at the beginning of the flow channel, approximately in the region of the largest depth of groove 140, to a second height h2 at its end, in the region of the flat sector.

[0064] The cross-sectional area of the flow channel affects the hydraulic efficiency of a pump. The cross-sectional area of the flow channel of heated pump 1 of the present invention is defined by its approximately constant width B and its height which increases from h1 to h2 in flow direction. Thereby, the cross-sectional area of the flow channel increases in flow direction, whereby the hydraulic efficiency of heated pump 1 may be increased.

[0065] The helical shape of heating element 132, which corresponds to the helical shape of groove 140, together with their matching cross-sectional shapes, provides a maximum contact area between heating element 132 and the contact surfaces of groove 140. Thereby, an optimal heat transfer from heating element 132 via carrier element 120 to the medium to be heated is reached.

[0066] Furthermore, due to the helical shapes of heating element 132 and groove 140, only one end 132a of heating element 132 has to be realized as a cranked end, whereas the second end 132b may be left straight. Thereby, one cranked end, which may form a possible hot spot, may be omitted. It has to be understood that the term straight end also includes a design in which the second end 132b of heating element 132 is circularly shaped, corresponding to the remaining circular portion of heating element 132. With regard to the present invention, straight end means that this end is not cranked.

[0067] Moreover, the cranked first end 132a is arranged in that portion of groove 140 with the maximum extension into pump housing 50. Accordingly, cranked end 132a of heating element 132, which may also be a possible hot spot, is optimally cooled by the fluid medium.

[0068] Heating element 132 may be secured in groove 140 by a suitable joining process, like welding, soldering or gluing. These joining technologies provide a safe connection between heating element 132 and carrier unit 120. Particularly, by using soldering or gluing technologies, the additional material inserted between heating element 132 and the inner surface of groove 140 may fill a possible gap therebetween, and the heat transfer from heating element 132 via carrier unit 120 to the fluid medium may be optimized. With regard to a gluing process, it has to be noted that the glue used should have specific features regarding thermal stability and heat conductivity.

[0069] The connection or joining between the heating element and the groove in the disk-shaped carrier unit should be designed in such a way that, viewed in cross-section, at least 50% of the outer circumference of the heating element is in planar contact with the boundary surface of the groove, preferably this contact should be >50%. Defects, such as air inclusions, which can form between the outer circumferential surface of the heating element in the groove and the boundary surface of the groove during a, for example, soldering process are not taken into account.

[0070] As an alternative to a joining process, it is possible to mount a heating element force fit in the groove 140 of the carrier element 120. The cross-section of the groove may be designed such that it has an approximately rectangular or trapezoid shape with side walls which exert a clamping force to a correspondingly shaped heating element.

[0071] In one case, the distance between the upper ends of the legs of the groove (at the open side) is smaller than the distance between the ends of the legs at the groove base. A heating element that has a width corresponding to the distance between the ends of the legs at the groove base, may be pressed into the groove 140 and is secured therein by a biasing force exerted thereto by the upper ends of the legs of the groove.

[0072] A possible gap between the inner surface of the groove and the heating element may then be filled with a thermal conductive paste or the like.

[0073] Carrier element 120 is preferably made of aluminium or an aluminium alloy, which provide suitable heat conductive features. However, other materials may be used, dependent on the specific application or the medium to be heated. In case of an aggressive medium, stainless steel may be used for the carrier unit. Alternatively, or additionally, carrier unit 120 may be provided with a protective coating. The protective coating may be realized in different ways. In a simple case, it may be sufficient to provide a corrosion resistant layer of plastic. In other cases, a layer of stainless steel may be roll-plated onto a carrier unit of aluminium or an aluminium alloy. Furthermore, the protective coating can be made of an inorganic material, a sol-gel material, a glass-like material etc.

[0074] Heating unit 100 is provided with safety devices B, C and a connecting device D. Safety devices B, C are arranged at respective portions of heating element 132 with safety device B in vicinity to second end 132b of heating element 132 (cf. FIG. 5).

[0075] Safety device B, which may be a temperature sensor, like an NTC thermistor, or an electromechanical switching unit is directly attached to heating element 132 in order to detect the temperature of heating element 132. Safety device C, which may be a second temperature sensor, formed by an NTC thermistor, is arranged in a central region of heating element 132 and with a distance k thereto (cf. FIGS. 5a, 5b, 5c). Safety device C may be arranged at a carrier element that is arranged above heating element 132 with a respective distance thereto. Distance k and the position of safety device C may be selected such that the maximum fluid medium temperature may be limited and that heating system 100 is thermally protected against overheating without activating a thermal fuse. Usually, distance k is selected between 0.3 and 3 mm, in particular 1.5 mm, and may depend on the kind of material of carrier unit 120. In case that the material has a high thermal conductivity, distance k may be less than in the case that the material of carrier unit 120 has a lower thermal conductivity.

[0076] By using safety devices B and/or C, the temperature of the medium to be heated may be adjusted such that a protection against boiling and/or drying can be achieved.

[0077] Safety devices B, C are fixed to heating element 132 or carrier unit 120 in a suitable manner. Safety devices B, C may be soldered, welded, glued or pressed against the respective heating or carrier element by a biasing force, e.g. exerted by an elastic element, like a spring, in order to provide sufficient contact between safety devices B, C and the respective element for correctly detecting the temperature. FIG. 6 shows safety devices B, C which are welded to heating element 132 and carrier unit 120. In FIG. 7, one of safety devices B, C is secured to carrier unit 120 by a clamping element, like a retainer plate E with an elastic element F arranged between retainer plate E and safety devices B, C.

[0078] The cross-section of heating element 132 has been described as being V-shaped, and as corresponding to the cross-sectional shape of groove 140. However, the heating element, and the groove accordingly, may have any suitable shape, like a triangular, rectangular, trapezoid or circular shape. It is essential, that the shape of the heating element at least approximately matches the shape of the groove.

[0079] The described V-shape of heating element 132 is preferred, since the heating wire, which extends longitudinally through the tubular body, is arranged with an approximately equal distance to the V-shaped portion of the tubular body, which corresponds to those portions of the surface via which heat is transferred to the fluid medium to be heated. Thereby, a uniform heat transfer over the length of the heating element may be realized.

[0080] FIGS. 8a and 8b show another embodiment of the inventive heating system 100. Here, the groove bottom 140a has only one section that is inclined in relation to a horizontal plane that intersects the central longitudinal axis A vertically. As can be seen from FIG. 8b, the shape or course of the groove bottom 140b is similar to a so-called Lebus drum. Of course, several such sections can also be provided within the groove bottom 140a. In addition, the transitions from the surface sections of the groove bottom 140a and the slope(s) running parallel to the horizontal plane may be rounded or formed as sharp edges. Furthermore, it is possible that the two horizontal surface sections of the groove bottom 140a itself have an inclination relative to the horizontal plane.