WO1989012204A1

WO1989012204A1 - Induction heater

Info

Publication number: WO1989012204A1
Application number: PCT/GB1989/000629
Authority: WO
Inventors: John Strothers Curran
Original assignee: Eastern Electricity Board
Priority date: 1988-06-07
Filing date: 1989-06-07
Publication date: 1989-12-14
Also published as: EP0419512A1; GB2219715A; GB2219715B; GB8813437D0

Abstract

This specification discloses an induction heater (1) for heating fluid comprising a chamber (4), such as a pipe, through which fluid passes in use, a primary winding (7) wound around the chamber and a closed secondary (8) arranged inside the chamber and having a portion for heating the fluid configured as a spiral. Such an induction heater provides for even heating of the fluid.

Description

INDUCTION HEATER

The present invention relates to induction heaters and in particular to induction heaters adapted to heat fluids.

Induction heaters which comprise a primary winding wound around a pipe, the pipe itself acting as the secondary, suffer from the disadvantage that temperature distribution is uneven across the cross section of the fluid in the pipe. In particular, overheating of the fluid may occur in the static laminar boundary layer adjacent to the wall. This problem may be particularly severe for some fluids, for instance highly viscous fluids. In additon, fluids susceptible to shear thinning and multiphase materials may also suffer from such problems.

A known solution to overcoming the problem of uneven heat distribution exemplified by overheating at the boundary layer is to provide a static mixing element made up of an arrangement of angled blades. The blades result in transverse fluid flow being superimposed on the axial laminar flow and, consequently, provide for the continuous renewal of material in the boundary layer. Such blade mixing elements are not, however, utilised in induction heated arrangements but normally only in unheated conduits.

It is an object of the present invention to provide an induction heater which provides even heating of fluid.

In accordance with the present invention, an induction heater for heating fluid comprises a chamber, through which fluid passes in use, a primary winding wound around the chamber and a closed secondary arranged inside the chamber and having a portion for heating the fluid configured as a spiral. Conventiently, the chamber may be cylindrical and the spiral substantially co-axial with the chamber and of a uniformly increasing curvature. By providing an internal heating element of such a shape, an induction heater is provided which both heats and mixes thus providing the even heating of the fluid.

In a preferred embodiment, the portion of the secondary is either a spiral wire or a sheet of expanded wire mesh. The flow of fluid across such a sheet is not axial laminer but instead comprises significant transverse components which provide for the continuous replacement of fluid in the boundary layer, adjacent to the chamber walls, as well as continuous radial mixing, throughout the cross-section of the pipe.

An embodiment of the invention will now be described with reference to the accompanying drawing which depicts an induction heater exemplifying the present invention.

Referring now to Figures 1 and 2, an induction heater, indicated generally at 1, comprises a cylindrical pipe section 4 defining a chamber closed by end plates 5 and 6. Fluid is fed into the cylindrical section 4 through an inlet port 2 in the end plate 4 and passes from the chamber via outlet port 3 in the end plate 6. The primary winding 7 of the induction heater is wound around the cylindrical section 4 and is connected to an appropriate power supply source (not shown) .

The secondary of the induction heater is arranged inside the chamber and comprises a spiral portion 8 of uniformly increasing curvature substantially co-axial with the cylindral section 4. A return portion 9 of the secondary connects the outermost and innermost sections of the spiral portion 8 to render the secondary closed. The return portion 9 comprises a cylindrical rod, co-axial with the spiral portion, to which is connected the innermost section of spiral portion 8. A further section of the return portion is connected to the rod 12 and to the outermost section of spiral portion 8. The spiral portion 8 is supported in position in the chamber by a pair of support members 10 and 11 which each comprise a circular plate with a spiral channel into which the edge of the spiral portion 8 may be inserted. The spiral portion 8 of the secondary is preferably a sheet of expanded wire mesh. The structure of such a mesh disrupts the axial laminar flow of fluid and imparts transverse movement to the fluid. It will be appreciated that an appropriately positioned heating element configured as a spiral acts as a uniform heat source across substantially the whole diameter of the cylindrical section 4.

The induction heater 1 is adapted to be connected to a fluid conduit (not shown) via inlet and outlet ports 2 and 3. Further, the induction heater is adapted to be easily disconnected from the fluid conduit and the end plates 5 and 6 easily removable to allow access to the inside of the cylindrical section 4. Spiral support member 10 may also be easily removable to allow the retrieval and disposal of the spiral portion 8 of mesh during routine cleaning operations.

Claims

CLAIMS :

1. An induction heater for heating fluid comprising a chamber through which fluid passes in use, a primary winding wound around the chamber and a closed secondary arranged inside the chamber and having a portion for heating the fluid configured as a spiral.

2. An induction heater as claimed in Claim 1 wherein the chamber is cylindrical and the spiral portion of the secondary is substantially co-axial with the chamber and of a uniformly increasing curvature.

3. An induction heater as claimed in Claim 2 wherein the diameter of the spiral portion is sufficient to provide in use substantially even heating of the viscous fluid.

4. An induction heater as claimed in any preceding claim wherein the portion for heating the fluid is a spiral wire.

5. An induction heater as clained in any of preceding claims 1-3 wherein the portion for heating the fluid is a sheet of expanded wire mesh.

6. An induction heater as claimed in any preceding claim wherein the secondary is shaped to impart transverse flow to fluid passing through the chamber.