Electric fluid flow heater with stabilisation brace

Abstract

An electric heater to heat a flow of a fluid having a jacket block comprising a plurality of longitudinal bores to allow the through-flow of a gas phase medium. An elongate heating element extends through each of the bores that together with the jacket block define a heating assembly to heat the gas. The heating assembly is positionally stabilised within the electric heater via at least one brace configured to inhibit undesirable independent axial and/or lateral movement of the heating assembly within the electric heater.

Claims

1. An electric heater to heat a flow of a fluid, comprising: at least one axially elongate jacket element defining an axially elongate jacket block having first and second lengthwise ends; a plurality of longitudinal bores or channels extending internally through the jacket block and being open at each of the respective first and second lengthwise ends; at least one heating element extending axially through the bores or channels, the at least one heating element and the jacket block forming a heating assembly; a casing positioned to at least partially surround the heating assembly, wherein at least one brace is connected to or projecting from the casing to contact the jacket block to inhibit axial and/or lateral movement of the jacket block relative to the casing.

2. The electric heater as claimed in claim 1, wherein the casing comprises an outer sheath that surrounds the heating assembly and the at least one brace extends radially between the sheath and the jacket block.

3. The electric heater as claimed in claim 2, wherein the casing further comprises at least one spacer extending radially from the sheath and towards the jacket block, the brace mounted at or extending from the spacer to contact the jacket block.

4. The electric heater as claimed in claim 3, wherein the brace comprises a plurality of rods extending into and through the jacket block at regions between the longitudinal bores or channels.

5. The electric heater as claimed in claim 4, wherein the brace comprises a shoulder block positioned at or towards a radially inner region of the spacer.

6. The electric heater as claimed in claim 5, wherein the brace comprises at least a pair of the shoulder blocks positioned at opposite lateral sides of the jacket block and the rods are mounted at and extend between the shoulder blocks to extend through the jacket block.

7. The electric heater as claimed in claim 6, comprising: at least a first pair of shoulder blocks positioned at lateral sides of the jacket block; and a first set of the rods extending through and across the jacket block between the shoulder blocks and a second set of the rods extending through the jacket block perpendicular to the first set of the rods.

8. The electric heater as claimed in claim 6, comprising: a first pair of shoulder blocks and a first set of the rods extending through the jacket block; and a second pair of the shoulder blocks and a second set of the rods extending through the jacket block, wherein the second pair of shoulder blocks are positioned at different lateral sides of the jacket block relative to the first pair and the second set of rods extends generally perpendicular to the first set of the rods.

9. The electric heater as claimed in claim 8, wherein the first pair of shoulder blocks and the second pair of shoulder blocks are positioned at different regions along a length of the jacket block between the lengthwise ends.

10. The electric heater as claimed in claim 5, wherein the jacket block comprises a plurality of channels extending generally perpendicular to the longitudinal bores or channels to receive the rods.

11. The electric heater as claimed in claim 1, comprising a plurality of jacket elements assembled together as a unitary body.

12. The electric heater as claimed in claim 10, comprising a plurality of jacket elements assembled together as a unitary body, wherein each of the jacket elements comprise at least a first and second groove indented in external surfaces of the jacket element such that the first and second grooves of neighbouring or adjacent jacket elements align to define one of the respective channels to receive one of the respective rods.

13. The electric heater as claimed in claim 12, wherein each of the jacket elements comprise a projection at a first region and a groove at a second region of at least one external surface, the projection of one of the jacket elements configured to at least partially sit within the groove of an adjacent jacket element to at least partially interlock the jacket elements.

14. The electric heater as claimed in claim 11, wherein each of the jacket elements comprise a polygonal or rectangular outer cross sectional profile.

15. The electric heater as claimed in claim 13, wherein each of the jacket elements comprise a polygonal or rectangular outer cross sectional profile, and wherein the projection and the groove are provided at different side faces of each respective jacket element.

16. The electric heater as claimed in claim 3, wherein the brace comprises a plurality of rods extending into and through the jacket block at regions between the longitudinal bores or channels, and wherein each of the spacers comprises a part-disc shaped member having a central aperture through which a part of the jacket block extends.

17. The electric heater as claimed in claim 16, wherein the casing comprises a generally cylindrical sheath encapsulating the heating assembly.

18. The electric heater as claimed in claim 17, wherein the spacers are attached to a radially inner surface of the sheath.

19. The electric heater as claimed in claim 1, comprising a plurality of the jacket elements assembled together in touching contact with one another to define the elongate jacket block, each of the plurality of longitudinal bores or channels extending respectively through each of the jacket elements; and the brace comprises at least a pair of shoulder blocks positioned at opposite lateral sides of the jacket block and a plurality of rods mounted at and extending between the shoulder blocks to extend through the jacket block.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

(2) FIG. 1 is a perspective view of a part of an electric heater according to one aspect of the present invention;

(3) FIG. 2 is a perspective view of a heating assembly forming a part of the electric heater of FIG. 1;

(4) FIG. 3 is a cross sectional side view of the part of the electric heater of FIG. 1;

(5) FIG. 4 is a cross section through A-A of FIG. 3;

(6) FIG. 5 is a perspective view of a portion of a jacket element and heating element forming part of the heating assembly of FIG. 2;

(7) FIG. 6 is a further perspective view of a pair of jacket elements assembled together in close fitting contact.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

(8) Referring to FIGS. 1, 2 and 3 an electric heater 1 comprises a casing 2 in a form of a cylindrical sheath 3 (having internal and external facing surfaces 3b, 3a respectively) that defines an internal chamber 4 open at both axial ends. A heating assembly indicated generally by reference 5 is mounted within chamber 4. Heating assembly 5 is formed from a plurality of lengthwise elongate jacket elements 6 assembled and held together to form a lengthwise elongate jacket block 7. Each elongate jacket element 6 comprises a lengthwise extending longitudinal internal bore 8 extending the full length of each jacket element 6 so as to be open at a first and second axial end 7a, 7b of the jacket block 7. The jacket element 6 and jacket block 7 are formed as hollow bodies in which the solid mass and volume extends continuously between the first and second axial ends 7a, 7b. That is, the jacket elements 6 and jacket blocks 7 are not discontinuous between respective ends 7a, 7b. Such an arrangement is advantageous to maximise the extent and efficiency of thermal energy transfer within the respective jacket elements 6 as explained in further detail herein.

(9) Jacket block 7 is mounted in position (within casing 2) via a pair of disc-shaped spacers 9a, 9b positioned in a lengthwise direction towards each jacket block axial end 7a, 7b. Sheath 3 and spacers 9a, 9b may be formed from metal such that spacers 9a, 9b are secured to an internal facing surface 3b of sheath 3 via welding. Each spacer 9a, 9b comprises a central aperture 10 having a rectangular shape profile and dimensioned to accommodate jacket block 7 that also comprises an external generally cuboidal shape profile. Accordingly, jacket block 7 is mounted within each spacer aperture 10 so as to be suspended within chamber 4 and spatially separated from sleeve internal facing surface 3b.

(10) A heating element indicated generally by reference 11 is formed as an elongate rod having respective ends 11d, 11e projecting generally from one of the axial ends of jacket block 7. Ends 11d, 11e are illustrated in FIGS. 1 to 3 projecting from the hot end 7b of the jacket block 7 for illustrative purposes. Ends 11d, 11e, preferably extend from the cool end 7a of jacket block 7. Heating element 11 comprises a generally circular cross sectional profile and is dimensioned slightly smaller than the cross sectional area of each jacket element bore 8. The single heating element 11 is adapted to extend sequentially through each elongate bore 8 of the jacket block 7 via respective bent axial end sections 11a and 11b. In particular, heating element 11 emerges from one bore 8 of a first jacket element 6 is bent through 180? (heating element end section 11a) so as to return into an adjacent or neighbouring bore 8 at the jacket block first axial end 7a. This is repeated at the jacket block second axial end 7b via bent end sections 11b. Heating element ends 11d, 11e are capable of being coupled to electrical connections to enable a current to be passed through element 11 as will be appreciated.

(11) Referring to FIG. 6, each jacket element 6 comprises four longitudinal extending side faces 6a, 6b, 6e and 6h that are generally planar such that each jacket element comprises an external generally square cross sectional shape profile adapted to enable the jacket elements to sit together in touching contact to form a rectangular cuboidal unitary body in which the individual side faces of the jacket elements 6 form the external facing surfaces of the jacket block 7. A small gap is provided between each spacer aperture 10 and the external surfaces of jacket block 7 (defined by jacket element side faces 6a, 6b, 6e, 6h). Such gaps accommodated differential thermal expansion of the spacers 9a, 9b (typically formed from metal) and the jacket elements 6 that are preferably formed from a non-electrically conducting refractory material. However, at least some structural support of the jacket block 7 and heating element 11 is provided by spacers 9a, 9b (via apertures 10) that are at least partially in contact with jacket block 7. To inhibit axial and lateral movement of each of the individual jacket elements 6 (relative to a longitudinal axis 20 extending through heater 1), each jacket element 6 comprises a groove 6f and a corresponding rib 6g extending laterally across jacket elements 6 and perpendicular to axis 20. The grooves 6f and ribs 6g of neighbouring jacket elements 6 are adapted to inter-fit one another to provide a part-tessellating jacket block 7 resistant to axial loading forces and lateral shear forces. The groove and rib arrangement (6f, 6g) of FIG. 5 is complementary to the positional holding of the heating assembly 5 via spacers 9a, 9b.

(12) Referring to FIGS. 2, 3 and 4, the present electric heater is specifically configured with at least one brace indicated generally by reference 12 (alternatively termed a heating assembly stabilisation unit) configured to positionally stabilise the heating assembly 5 (that encompasses the jacket block 7 and the heating element 11) within the electric heater 1 and in particular relative to the casing 2. Such an arrangement is advantageous to minimise independent movement of the heating assembly 5 within the heater 1 and with respect to the casing 2.

(13) As will be appreciated, the dimensions of the heating element 11 and bores 8 are carefully controlled to achieve a desired small separation gap between the inward facing surface of each bore 8 and the external surface of heating element 11. Such an arrangement is advantageous to maximise the effectiveness and efficiency of heat energy transfer from element 11 to a flow of a gas phase medium initially introduced as an inlet flow 14a into the chamber 4 at axial end 7a to then flow through each of the bore 8 and exit from the heating assembly 5 at axial end 7b as an exit flow 14b. When the electric heater 1 is suspended vertically in use, undesirable contact between the bent end sections 11a, 11b and the end faces 6c, and in particular the annular edges that define the entry and exit end of each bore 8, contribute to fatigue and damage to the heating element 11 and a corresponding reduction in the service lifetime of the heater 1. To mitigate this, brace 12 is specifically adapted to inhibit and in particular to prevent any independently axial and lateral movement of the jacket block 7 relative to the heating element 11.

(14) Advantageously, brace 12 is positioned at or towards a cool axial end (closer to ambient temperature) of the heating assembly 5 corresponding to the gas inlet flow 14a relative to a hot axial end (at temperatures of up to 1200? C.) for heated gas outflow 14b. The cool first axial end 7a is the region of lower stress (lower temperature differential) relative to the second axial end 7b and therefore stabilisation towards the first axial end 7a is more practical and effective.

(15) Referring to FIGS. 4 and 5, brace 12 comprises a pair of spaced apart shoulder blocks 15 that are secured to a front face 30 of spacer 9a so as to project forwardly into the oncoming gas flow 14 a. Boreholes 17 extend through each shoulder block 15 along axis 16 extending perpendicular to main longitudinal axis 20 of the heater 1. An elongate rod (or bar) 18 is mounted within each borehole 17 to be centred on axis 16 and to extend between each of the opposed shoulder blocks 15 and laterally through jacket block 7. The present invention comprises a plurality of stabilisation rods 18 each extending through jacket block 7, parallel to one another and perpendicular to the main longitudinal axis 20.

(16) Each jacket element 6, in addition to the rib and grooves 6g, 6f of FIG. 6, also comprises an additional pair of grooves 19a, 19b located at a different axial position along the length of each jacket element 6 relative to the rib and grooves 6g, 6f of FIG. 6. Referring to FIG. 5, grooves 19a, 19b are provided at diametrically opposite side faces 6b, 6e at the same axial position along the length of jacket element 6 to extend laterally across jacket element 6 perpendicular to main axis 20. Each groove 19a, 19b comprises a semi-circular cross sectional profile (relative to axis 16) to correspond to a portion of the external surface of a rod 18. Accordingly, when the jacket elements 6 are arranged together to form the array (jacket block 6), as illustrated in FIG. 4, the grooves 19a, 19b of neighbouring jacket elements 6 align so as to define channels 19 (alternatively termed boreholes) of circular cross section. The channels 19 extend laterally through jacket block 7 and are configured to accommodate a respective rod 18. Channels 19 are positioned laterally to the side of the main bores 7 so as to not interfere with the bores 7 and the electrically conducting heating element 11. According to the preferred specific implementation, each rod 18 comprises a metallic core surrounded by a refractory coating. Such an arrangement is advantageous to minimise any differential thermal expansion of the rods 18 and jacket block 7. Accordingly, the present electric heater via shoulder blocks 15 is configured to stabilise the heating assembly 5 at the external surface region 6a, 6b, 6e, 6h and also to provide stabilisation via internal contact of the jacket block 7 via rods 18.

(17) Whilst the electric heater is illustrated and described comprising a single pair of shoulder blocks 15 and a corresponding first set of rods 18, the heater 1 may, according to further specific implementations, comprise multiple pairs of shoulder blocks 15 and sets of rods 18. Such additional pairs and sets may be provided at different regions along the axial length of the heating assembly 5 between axial ends 7a, 7b. Such arrangements would be advantageous to stabilise the heating assembly 5 along its axial length. Alternatively, the multiple pairs and sets of braces 12 may be located towards the cool end (7a) of the gas inlet flow 14a.

(18) The present electric heater having an axially and laterally stabilised heating assembly 5 is configured with an extended operation lifetime via minimised independent movement of the jacket block 7 relative to heating element 11 and casing 2. The effectiveness and efficiency of heat energy transfer within the present electric heater is provided by the heating elements 6 extending continuously lengthwise (axially) between respective ends 7a, 7b. In particular, heating element 11 is entirely and continuously housed, covered and contained by the elongate jacket elements 6 between ends 7a, 7b.

(19) As will be appreciated, whilst the subject invention is described with reference to shoulder blocks 15 and elongate rods 18 inserted through jacket block 7, the same stabilisation may be achieved via alternative components and arrangements in which an external and/or internal region of jacket block 7 is contacted by at least one or more abutment components and/or members that are secured, either directly or indirectly to casing 2 (for example via intermediate spacers 9a, 9b). For example, such abutment components may comprise flanges, projections, eyelets, hook shaped members, plates, sheaths, wires, cables, pins, mesh, grids or washers adapted for abutment contact at the external and/or internal regions of the jacket block 7.