Apparatus and method for the ohmic heating of a particulate liquid

Abstract

An electrode for the ohmic heating of a particulate liquid flowing therethrough having an inlet and an outlet that are fluidly connected and are arranged in such a way that there is a change of direction of 60°-120° between the inlet and the outlet. A cell for the ohmic heating of a particulate liquid flowing therethrough may have two such electrodes and a dielectric tube that fluidly connects the two electrodes. An apparatus for the ohmic heating of a particulate liquid flowing therethrough may have six such cells that are fluidly connected in series and are electrically connected to a triphasic power supply, so that the increase of temperature of the liquid at any cell is substantially the same.

Claims

1. An electrode for the ohmic heating of a particulate liquid flowing therethrough, comprising an inlet and an outlet that are fluidly connected and are arranged so that there is a change of direction of 60°-120° between the inlet and the outlet, wherein the inlet is a duct and the outlet is a port or the inlet is a port and the outlet is a duct, and the port and the duct intersect; and wherein the port has an outer opening on an outer surface of the electrode, and said outer surface is concave.

2. The electrode according to claim 1, wherein the change of direction is of 73°-107°.

3. The electrode according to claim 1, wherein the ratio between the width of the duct and the width of the port is bigger than 3.

4. The electrode according to claim 1, which comprises at least six such ports.

5. The electrode according to claim 4, wherein the ports are divergent as viewed from the duct.

6. A cell for the ohmic heating of a particulate liquid flowing therethrough, comprising two electrodes according to claim 1 and a dielectric tube that fluidly connects the two electrodes.

7. An apparatus for the ohmic heating of a particulate liquid flowing therethrough, comprising a group of at least three cells according to claim 6, so that the three cells are fluidly connected in series.

8. The apparatus according to claim 7, wherein the middle cell is arranged higher than another cell and lower than the other cell.

9. The apparatus according to claim 8, wherein any cell is arranged with its dielectric tube in a substantially vertical disposition.

10. The apparatus according to claim 7, comprising at least a subsequent group of three cells that is fluidly connected to the antecedent group of three cells.

11. The apparatus according to claim 10, wherein the passage in the dielectric tube of any cell of the subsequent group is narrower than the passage in the dielectric tube of any cell of the antecedent group.

12. The apparatus according to claim 11, wherein any two consecutive electrodes pertaining to different cells are electrically connected by a conductive element.

13. A method of heating a flowing conductive liquid, comprising the use of an apparatus according to claim 7, and wherein the voltage applied to any cell is substantially the same.

14. The method according to claim 13, wherein the increase of temperature of the liquid at any cell is substantially the same.

15. The electrode according to claim 3, which comprises at least six such ports.

16. The electrode according to claim 15, wherein the ports are divergent as viewed from the duct.

17. The apparatus according to claim 7, wherein any cell is arranged with its dielectric tube in a substantially vertical disposition.

18. The apparatus according to claim 10, wherein any two consecutive electrodes pertaining to different cells are electrically connected by a conductive element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Particular embodiments of the present invention will be described in the following, only by way of non-limiting example, with reference to the appended drawings, in which:

(2) FIG. 1A is a top view of an electrode;

(3) FIG. 1B is a perspective view of the electrode;

(4) FIG. 1C is a side cross-sectional view of the electrode;

(5) FIG. 2 is a side cross-sectional view of a cell with two electrodes;

(6) FIG. 3 is a schematic view of two groups of three cells; and

(7) FIG. 4 is another schematic view of two groups of three cells.

DETAILED DESCRIPTION

(8) With reference to FIG. 1, which is defined inclusively by FIGS. 1A, 1B and 1C, the electrode 10 is generally cylindrical and made of graphite. It comprises a duct 11 and several ports 12 fluidly connected to the duct inside the electrode. There is an angle of about 90° between the duct and the ports, for example of 73°-107°, and the ports are somewhat divergent as viewed from the duct. The outer openings of the ports 12 lie on a concave outer surface 13 of the electrode, which is the surface of the electrode that transmits most current to the conductive liquid that flows through the duct 11 and the ports 12. A peripheral flat surface 14 adjacent to the concave surface 13 is used for sealing abutment against a dielectric tube 20 that joins and fluidly connects two electrodes 10 (see FIG. 2).

(9) The dielectric tube 20 comprises a central passage 21 and two wider ends 22 that, with a tapered configuration, connect the central region 21 to the concave surfaces 13 and the ports 12 of the electrodes 10. This assembly is and/or forms an ohmic-heating cell 50. In operation, one electrode is electrically connected to earth and the other electrode is electrically connected to the power supply, so that there is a current circulation through the liquid (for example fruit juice) that flows between the electrodes and through the dielectric tube 20.

(10) It may be necessary to increase the temperature of the liquid from, for example, 50° C. to 105° C. in a very short time. This can be done with six cells 50 arranged in series, so that the temperature of the liquid is increased about 9° C. at each cell. FIG. 3 shows such an arrangement in the form of a structure 100.

(11) Structure 100 comprises six cells 50 arranged in series. The two electrodes of any cell are at different potentials, but any two consecutive electrodes pertaining two different cells are at the same potential, i.e. electrically connected to the same phase R, S or T (or to the neutral O) of a triphasic power supply. FIG. 3 schematically shows the tubes 60 that connect, both fluidly and electrically, any such pair of consecutive electrodes. The first and the last electrode are connected to the neutral (earth), and thus a perfect electrical equilibrium is achieved among the phases.

(12) It is well known that conductivity increases with temperature and also that is proportional to the cross-section area of the conductor. In the present case, the conductor is the cylinder of conductive liquid that flows through the central passage 21 of the dielectric tube 20. The conductivity of this liquid is higher downstream because the liquid has already been heated. Therefore, the increase of temperature of the liquid in a cell downstream is bigger than in a cell upstream, as long as the dimensions and the voltage are the same. There are basically two ways to achieve the same increase of temperature in all the cells: to decrease the voltage applied to the downstream cells or to decrease the cross-section area of the central passage 21 of the downstream cells as shown in FIG. 4. The latter arrangement would make the resistance of the cylinder of conductive liquid that flows through the central passage 21 of a downstream cell higher than that of an upstream cell if the liquid is at the same temperature; since the temperature of the liquid is progressively increased downstream, the width of the central passages 21 of the successive cells 50 can be suitably narrowed in order to have substantially the same temperature increase in all the cells. For example, the diameter of the central passage of the first cell can be 30 mm and the diameter of the central passage of the last cell can be 25 mm.

(13) The cells are arranged with the dielectric tubes in a vertical disposition, one cell being placed higher than the preceding cell, so that the flow is forced to be upward. This facilitates the upward motion of the air bubbles that might be in the liquid, so that they can be easily extracted through the top of the cells. In order to prevent the structure 100 from being too high, the six cells can be divided in two groups of three cells placed at the same height, as shown in FIG. 3, in which the bold lines represent the pipes for the flow of the liquid and the sense thereof.

(14) Although only particular embodiments of the invention have been shown and described in the present specification, the skilled person will be able to introduce modifications and substitute any technical features thereof with others that are technically equivalent, depending on the particular requirements of each case, without departing from the scope of protection defined by the appended claims.