GB2490022A - Apparatus and method, particularly for processing flowable food products - Google Patents

Abstract

Apparatus for use in heating and mixing flowable food products or other flowable substances comprises at least one steam injector for injecting or introducing steam into the food product. In the case of an apparatus including a single such steam injector, a duct 6,10 extends between an inlet 8 and an outlet 9. A plenum chamber 12 is disposed adjacent the duct and an inlet 14 is provided for admitting steam to the plenum chamber. An orifice 35 opens from the plenum chamber into the duct and, by virtue of a Coanda surface located in the duct, steam is induced to flow towards the outlet and entrain the food product with it. A downstream end portion 10 of the duct may be outwardly flared or frusto­conical shape and constitutes an expansion chamber in which steam collapses and substantially all of its energy is imparted to the food product.. A plurality of parallel steam injectors may be provided to enhance performance.

Description

ito&pipp&atus, particularly but noLexciusiyjyjjpcessin.g flyable food prochi4s This invention relates to a method and apparatus, particularly for the industrial processing of flowable food products, such apparatus being of

use in other industrial fields as a fluid mover.

It is known to inject steam into an industrial cooking vessel containing a flowable food product in order to cook or partially cook the food product.

i 0 The systems known for this purpose are not altogether satisfactory. For example, the rate at which food may be processed using the system disclosed in GB 2 106 SOQA (Giusti) is limited and a separate arrangement for stirring the contents of a cooking vessel is required. A fluid mover stated to be of use in various industries (including the food industry) is disclosed in US Patent App. Pub. 2004/01414 10 (Fenton) but requires a supersonic shock wave to be generated within a mixing chamber, which may lead to unacceptable vibration and noise.

The present invention seeks to overcome the problems inherent in the prior art, and in particular provide an apparatus and method which may be used to process flowable food products, such as soup or stew, more rapidly and effectively than hitherto. Herein, "processing" a food product comprehends the heating and cooking thereof, as well as mixing, with or without heating. Although the invention will be disclosed in the context of industrial food processing (including using steam as a heat source), it will be found of use in other industries, including the brewing, water treatment and petrochemical industries, for example, with or without heating, and as a fluid mover.

Apparatus in accordance with the invention includes a body through which a duct extends and into which an orifice opens for the introduction of a primary fluid. An inlet for a secondary fluid is provided at an upstream end of the duct and an outlet for the secondary fluid is provided at its downstream end. The orifice is located closely adjacent to the inlet for secondary fluid, and may be recessed or set back into a rim surrounding the inlet on its side facing in the downstream direction. The primary fluid is made to flow through the duct towards the outlet and bring about a reduction in pressure within the duct such as to draw secondary fluid through the inlet into the duct.

The duct may have upstream and downstream sections, the upstream section being elongate and of substantially constant cross-section throughout its length. The cross-sectional area of the downstream section may be greater than the cross-sectional area of the upstream section, at least on average. For convenience of manufacture, the duct may be of circular cross-section so that the average internal diameter of the downstream section of duct is greater referabiy substantially greater) than the internal diameter of the upstream section. Preferably the sections of the duct are of equal length, so that the volume of the downstream section is greater than that of the upstream section.

A plenum chamber for containing the primary fluid may be provided adjacent the upstream section and be arranged to communicate with the orifice, which is preferably constricted and adapted to discharge primary fluid into the duct at high velocity. The primary fluid, if at an elevated temperature, serves to heat the secondary fluid and propel it in the direction of the outlet.

In accordance with a first mode of performing the invention, wherein the primary fluid comprises a vapour, the primary fluid may be arranged to expand and collapse in its entirety within the downstream section of the duct, such that substantially all of the energy contained in the primary fluid is imparted to the secondary fluid, and none of the primary fluid escapes together with the secondary fluid through the outlet.

It will be appreciated that in the case of food processing, a flowable food product constitutes the secondary fluid, and may be heated or cooked using steam as the primary fluid. The downstream duct section may be widened and serve as an expansion chamber in which the steam expands and condenses in accordance with the first mode of operation, such that substantially all of the energy in the steam is imparted to the food product as both fluids flow through the expansion chamber, and substantially all of the steam condenses into water within the expansion chamber without any of the steam escaping from the outlet from the downstream end of the duct. Steam may, of course, be used as the primary fluid in connection with secondary fluids other than food products.

Food product may be contained in a vessel, such as a conventional industrial cooking kettle, in which the ducted body is immersed.

Essentially, therefore, in the context of food processing, steam is injected, discharged or introduced into the flowable food product within the duct, and the effect of steam flowing through the duct is to draw the food product through the inlet, propel it along the duct, and then discharge it through the outlet back into the kettle, wherein it promotes circulation.

The apparatus used to inject steam into the food product (which may be referred to herein as a "steam injector") may be mounted on the end of a lance or conduit, also conventional in the food processing field, and connected directly or indirectly to a source of steam. In operation, the steam injector is positioned such that both the inlet and the outlet open to the interior of the kettle below the level of the food product contained in it. A steam injector in accordance with the invention may therefore be regarded as a nozzle for such a lance or conduit. Although the apparatus used to inject or introduce steam into the duct is for convenience referred to herein as a steam injector, it may be used to introduce or inject primary fluids other than steam into secondary fluids other than flowable food products. It will also be understood that the apparatus may be used with primary fluids otherwise than at an elevated temperature.

The steam employed in connection with the invention may be superheated steam or steam in unsuperheated condition, and is preferably atomised steam, atomisation taking place either prior to its delivery to the steam injector or within the steam injector itself Conveniently atomisation takes place as the steam passes through the orifice, which may be shaped and dimensioned for this purpose.

Steam may be caused to flow towards the outlet from the duct by means of the Coanda effect, a Coanda surface being disposed within the duct in or in the vicinity of the orifice. By "Coanda effect" is meant the phenomenon in which ajet flow attaches itself to an adjacent surface and remains attached even when the surface curves away from the initial direction of the jet. It is found that a jet of fluid subject to the Coanda effect entrains and mixes with a surrounding fluid as it flows away from a nozzle or other outlet. When a surface is brought close to the jet, a pressure difference across the jet results and the jet is deflected closer to the surface, and eventually attaches to it. The jet remains attached to the surface, even if the surface is curved away from the initial direction of the jet. This effect can therefore be used to change the direction of the jet and entrain other fluids. The Coanda effect is to be contrasted with a system in which a jet of fluid is made to flow into and entrain a fluid along a given linear path, without becoming attached to an adjacent surface.

By "Coanda surface" is meant a surface which is so shaped and positioned that a jet of fluid (in the present case, a jet of steam) directed relative to the surface will become attached to and follow it, as described above.

The orifice, which is preferably constricted, may be located at the outlet end of a constricted annular passageway leading from the plenum chamber to the duct, and the passageway and orifice may be referred to herein as constituting a "gap". The gap may be defined between substantially annular surfaces located relatively upstream and is downstream of each other, with respect to the direction of flow through the duct, and the passageway and orifice may be inclined in the general downstream direction relative to the duct axis.

The widened region downstream of the duct which serves as the expansion chamber may be of cylindrical, frusto-conical or flared shape and have a volume greater than that of the upstream section of the duct which is of substantially equivalent length. The apparatus may be operated in the first mode such that steam fed into the expansion chamber under the action of the Coanda effect expands and collapses, and is entirely condensed into water. The expansion chamber may be so shaped and arranged that within it substantially all of the energy (or enthalpy) contained or remaining in the steam fed into it is imparted to food product. In consequence, no steam escapes from the outlet of the injector to rise to the surface of the food product, especially in the form of bubbles, such as to represent wasted heat. In an alternative second mode of operation, steam may be allowed to pass out through the outlet into the vessel and promote circulation therein. The optimum shape and dimensions of the passageway and associated orifice, as well as those of the expansion chamber, may be determined by experiment.

The inclination of the orifice relative to the axis of the duct, as well as the size of the gap, and the provision of surfaces disposed so as to bring about the Coanda effect, may also all be determined in shape and location by experiment, and be so arranged as to lead to optimum performance in most situations, in which the ideal atomised steam releases all or substantially all of its energy into the product being propelled. The noise of the steam, referred to as "steam hammer", which occurs when steam collapses into water is suppressed. Adjusting the above-mentioned gap at the upstream end of the duct leads to different mixing characteristics which may be beneficial in other circumstances. Thus, for example, widening the gap to bring about steam hammer may benefit the processing of certain products.

It is possible to predetermine the throughput of an individual steam injector as described above by selecting its dimensions at the design stage, in particular with regard to the internal cross-sectional area of the duct at various positions along its length, as well as those of the expansion chamber. However, it has been found that there is a limit to the rate at which food product may be processed using apparatus incorporating a single steam injector embodying the invention. In this respect there comes a point at which doubling the cross-sectional area of the duct, for example, does not result in a doubling of throughput.

This problem may be overcome, according to a further aspect of the invention, by the incorporation into the apparatus of two or more steam injectors, each having some or all of the features referred to above.

Each such steam injector may include a respective body through which an associated duct extends, and the apparatus may be provided with means for detachably coupling the bodies together. In the alternative, a plurality of ducts may extend through a body common to both or all ducts. Means other than the Coanda effect may be used to propel steam or other primary fluid through the ducts, as will be described hereinafter.

In the drawings: Figure I is a diagrammatic illustration of apparatus for heating and mixing a flowable food product shown mounted on a lance or conduit, the apparatus being immersed in the food product within a cooking vessel, Figure 2 is an axial section through a first embodiment of apparatus in accordance with the invention, constituted by an individual steam injector, taken on the line il-If in Figure 3, Figure 2A is a view similar to Figure 2 but of a steam injector with a modified expansion chamber, Figure 3 is an end view of the steam injector viewed in the direction of arrow III in Figure 2, Figure 4A is an axial section similar to Figure 2 but showing an outer body component of the steam injector shown in that Figure, Figure 4B is an axial section corresponding to Figure 4A but showing an inner body component of the steam injector, S Figure 5 depicts a fragment of the structure shown in Figure 2, showing to a greatly enlarged scale the components of the steam injector at its upstream end, including an orifice for injecting or introducing steam into a duct extending through the apparatus, JO Figure SA is a view similar to Figure 5 illustrating two possible flow patterns within the steam injector, Figure 6 is an isometric view of a second embodiment of apparatus incorporating two steam injectors,

IS

Figure 7 is a longitudinal section through apparatus shown in Figure 6, Figure 8 shows the detail at "B" in Figure 7 to an enlarged scale, Figure 9 shows to a greatly enlarged scale a fragment ofthestructure shown in Figure 7, including the components of the apparatus at its upstream end, including a passageway leading to an orifice for injecting or introducing steam into ducts extending through the apparatus, Figure 10 is a schematic illustration of a third embodiment of apparatus in which two steam injectors are accommodated in a body common to both, and Figure 11 is a view similar to Figure 7 of a fourth embodiment of apparatus incorporating two steam injectors which do not employ the Coanda effect.

ImcJpiesjfpperation Referring to Figure 1, a vessel A in the form of an industrial cooking kettle contains a quantity of a flowable food product B such as soup or stew. A tubular lance or conduit 4 is connected to a source of steam S which is used as a primary fluid to cook, or at least to heat, the food product, which constitutes a secondary fluid, and promote its circulation within the vessel. To this end, apparatus 2 which incorporates or is constituted by one or more steam injectors is screwed onto or otherwise removably mounted on the end of the lance or conduit 4, such as to serve as a detachable nozzle. The lance or conduit may be a fixture within the Is vessel or movable from a rest position externally of the vessel into an operational position within the vessel.

In a first embodiment of the invention the apparatus 2 consists of or incorporates a single steam injector. A substantially unobstructed rectilinear duet (not shown in Figure 1) extends from an inlet on the right-hand side of the steam injector 2 as viewed in Figure 1 to an outlet at the left-hand side of the steam injector. Steam fed to the steam injector 2 through the lance or conduit is injected or discharged into the duct and draws food product into the duct through the inlet as indicated by arrows C and discharges it through the outlet as indicated by arrows D, the food product being heated as it passes through the duct. In the first mode of operation steam supplied to the duct condenses into water without emerging (as steam) from the outlet. Residual quantities of steam may escape from the apparatus as a result of imperfect or partial operation, but this is to be taken to be de minimis.

in a second mode of operation steam is caused to flow through the steam injector such that a proportion thereof escapes from the outlet and serves to heat the food product within the kettle.

In industrial fields other than food processing, or when it is only a question of mixing (and not heating) the contents of a vessel, or mixing and optionally heating a fluid supplied directly to the inlet, a primary fluid other than steam may be employed. Thus hot or cold gases, vapours or fluids, other than steam may be used to promote the circulation or mixing of other substances. Also, in accordance with another aspect of the invention, the apparatus may be used to mix primary is and secondary fluids together.

in the case of a second embodiment the apparatus incorporates two steam injectors arranged side by side in parallel. Within the scope of the invention more than two such steam injectors arranged in parallel may be incorporated into apparatus for carrying out the invention.

Generally the apparatus is arranged in such a way that the food product is mixed homogenously with the steam, unless there is a specific requirement to the contrary. Non-homogenous processing may result in bubbles of steam emerging from the apparatus and rising to the surface, representing a loss of energy, without benefitting processing.

Unless steps are taken to prevent it, the external surfaces of the steam injector or injectors incorporated into the apparatus become heated and l0 may lead to food product in the kettle being scalded. Prevention of such scalding may be achieved by positioning of thermal insulation chambers within the body or bodies within the apparatus.

The construction and operation of embodiments of apparatus incorporating or consisting of steam injectors will now be described in greater detail, but by way of example, first in relation to apparatus incorporating a single steam injector, and thereafier in relation to apparatus incorporating two or more such injectors.

First emboçjjment A first embodiment of apparatus in accordance with the invention is shown in Figures 2 and 3 and comprises a single steam injector (or nozzle) 2 for injecting or introducing steam into a flowable food product such as soup or stew. The injection, discharge or introduction of steam into the food product takes place wholly within the apparatus. The steam injector has a body of circular cross-section machined from stainless steel, the external surfaces of the body being polished.

An elongate, rectilinear duct, likewise of circular cross-section, extends through the body and has an upstream section indicated at 6, and a downstream section indicated at 10. The duct is unobstructed throughout its entire length. An inlet at the upstream end of the duct is surrounded by a rim 8 and an outlet at the downstream end of the duct is surrounded byarim9.

The upstream section 6 of the duct is delimited by the radially inner surface of a cylindrical peripheral wall 24, such surface being of circular cross-section and of substantially constant diameter throughout its length, save where it is flared outwardly at its upstream end. The wall 24 separates the upstream section 6 of the duct from an annular plenum chamber 12 which surrounds the duct. The downstream section 10 of the duct is delimited by the radially inner surface of a peripheral wall 7 of S flared or frusto-conical shape. Within the scope of the invention the wall 24 may depart from a true cylindrical shape, provided that this does not interfere with operation of the system.

A steam inlet passage 114 extends radially through the body to open into the plenum chamber 12, and a constricted annular orifice 35 opens from the plenum chamber into the duet between the rim 8 and the upstream end of the wall 24 which is flared radially outwardly, as will be described in greater detail below. The wall 24 and hence the upstream section 6 of the duct are shown as having a length Li, measured from the orifice 35 to is an annular wall or surface 58 which defines the downstream end of the plenum chamber, while the radially inner surface of the wall 7, and hence the downstream section 10 of the duct, has a length L2, measured from wall 58 to the rim 9. Throughout its length L2, the inner surface of wall 7 has a diameter which, at least on average, is greater than the internal diameter of the wall 24. As a result, the cross-sectional area of the section 10 of the duct is, on average, greater than the cross-sectional area of the upstream section 6 of the duct.

In the ease of the modification shown in Figure 2A, the radially inner surface of the wall 7 is cylindrical in shape and of constant diameter D2 throughout its length L2, and the radially inner surface of wall 7 has a diameter which is greater than the internal diameter of the wall 24 throughout its length LI. Thus the average internal cross-sectional area of the section 10 of the duct, and hence its volume (the sections being of substantially equal lengths) are greater than those of the upstream section 6 of the duct, in the case of the Figure 2 and 2A constructions.

Disposed within the body, radially outwardly of the plenum chamber, is a $ closed, annular chamber 16 bounded on its radially outer side by a cylindrical cladding ring 18 manufactured from thin sheet stainless steel.

The edges of the cladding ring are received in rebates 17 in the edges of the chamber, and held in place by welding or other suitable means. The outer surface of the cladding ring is polished so as to appear indistinguishable from the apparatus body. The chamber 16 is substantially co-extensive with the plenum chamber, except where the steam inlet passage 14 passes through the apparatus body and opens into the plenum chamber. The steam inlet passage 14 is encircled by a cylindrical cladding tube 20 also of thin sheet stainless steel and forming the radially outer wall of an annular chamber 22. The chambers 16, 22 serve to provide thermal insulation as explained below.

The plenum chamber is bounded on its radially inner side by the radially outer surface of a cylindrical portion of wall 24, and at its upstream end by a radially outwardly flared end portion of that wall, as well as by a substantially radially extending annular surface or wall 25 machined into the rim 8 surrounding the inlet to the duct section 6 (see Figure 5). On its radially outer side the plenum chamber is bounded by the substantially cylindrical outer wall of the steam injector body (save where this is penetrated by the inlet 14 where it opens to the plenum chamber). At its downstream end the plenum chamber is bounded by the before-mentioned annular surface or wall 58.

Figures 5 and 5A each depict a radial section through those surfaces of the steam injector associated with the orifice 35, such that the plane of the paper includes the axis CL of duct section 6. The surfaces referred to below may therefore be considered to be represented by lines drawn on a radial plane through the steam injector. It will be seen that the wall or surface 25 is undercut on its rear or downstream side, in the sense that in the region of its root it has a frusto-conical proximal surface portion 26 inclined in the downstream direction and therefore represented in Figure by a straight line extending at an angle to the axis CL. Surface 26 merges into a concavely curved distal surface portion 30 which is represented by a curved line likewise inclined in the downstream direction. The surface portion 30 terminates where it meets a relatively sharp circular edge 8A on the rim 8 enclosing the inlet to the duct section 6; the edge 8A being represented in Figure 5 by a point, in accordance T5 with the protocol explained above. it will be appreciated that the surface is set-back or recessed into the rim 8, so that the orifice 35 is positioned as close as practicable to the inlet end of the steam injector.

The plenum chamber 12 is separated from the duct section 6 by the substantially cylindrical wall 24 which is of constant diameter, except at its upstream end where it is flared outwardly to form a lip, the convex surface 32 of which terminates adjacent the outlet in a cylindrical outwardly facing annular surface 27, At its other end the surface 32 of the lip is continued in the downstream direction (where it is indicated at 33) to merge into the radially inner surface of wall 24. in Figure 5 the surface 27 is represented by a line parallel to the axis CL and the lip 32, 33 by a convex line facing in the upstream direction.

An annular passageway of substantially constant width throughout its extent is defined between the concavely curved surface portion 30 and lip 32, the passageway terminating in the orifice 35 defined between the edge 8A and that portion of the lip 32 which faces the sharp edge 8A S represented in Figure 5A by a point. The passageway leads from the rearward end of the plenum chamber to the orifice 35 which opens into the duet section 6 immediately to the rear of the rim 8. The orifice 35 extends in an arc around the upstream end of the wall 24, part-way along the lip 32, 33. It will be understood that the orifice 35 need not completely encircle the axis CL of the duct section 6 but may be interrupted at intervals.

The inlet passage 14 is provided at its free end with a screw-threaded connector 42 or other means to enable the apparatus to be mounted on the lance or conduit through which steam is to be supplied to the apparatus.

A peg 44 fixed to the inner side of the connector 42 is received in an opening in the end of the lance or conduit to prevent the connection becoming unscrewed as a result of vibration taking place when the apparatus is in use.

The body of the steam injector constituting the apparatus is assembled from cylindrical outer and inner body components 50 and 52 shown in Figures 4A and 4B, respectively. The inner body component has a relatively large diameter base portion 53 from which projects the cylindrical wall 24 in the form of a tubular extension having a diameter less than that of the base portion. The base portion of the inner body component is formed on its inner side with the outwardly flared or frusto-conical widened surface 7 which serves as an expansion chamber 10.

[he rim 8, and the undercut surtice or wall 25 which delimits the plenum chamber at its upstream end are provided or formed on the outer body component 50, whereas the downstream end wall of the plenum chamber is formed in part by the wall or surface 58 which takes the form of an annular step between the larger diameter base portion 53 and the extension 24 of the inner body component.

The outer body component is formed at its downstream end with an end piece 68. The periphery of the outer body component is cut away at 60 so as to form a cylindrical recess, which is rebated along its edges, and serves as the radially inner region of the chamber 16. The outer body component 50 is provided with a female screw-thread MA on the end piece 68 and the inner body component with a complementary male screw-thread 54B.

The apparatus is assembled by introducing the inner body component 52 into the outer body component 50 and then screwing it into place by an appropriate distance to set the optimum or other desired width of the passageway or gap defined between surface 30 and lip 32, the width of the gap being determined by experiment.

A locking ring 62 shown in Figure 2 is then screwed onto the base portion 53 to maintain the gap at the desired width, the locking ring being provided with flats to facilitate tightening. ft is not essential for the screw-thread 54A to have the length indicated and a shorter screw-thread may be employed instead. To resist unintended rotation of the locking ring 62 relative to the screw-thread 5413, use may be made of an auxiliary ring (not shown) which is annular in shape and has a tab projecting from its inner edge. A shallow, axially extending groove (also not shown) is I6 milled into the screw thread 5413 and the auxiliary ring fitted between the end piece 68 and locking ring 62, The tab is introduced into the groove.

Outer edge portions of the auxiliary ring may then be turned over a flat on the outer body component, and ring 62 tightened, whereby the auxiliary ring locks the ring 62 to the endpiece 68.

the cladding ring 18 is introduced into the rebates 17 and welded or otherwise secured in place, and the cladding tube 20 fitted in place so as to embrace the passage 14. l'he apparatus may then be screwed onto a lance or conduit, the pin 44 entering an opening in a fitting associated with the lance or conduit serving to prevent the screw connection loosening.

It will be seen from Figure 2 that the indicated lengths LI and L2 are substantially equal. Because the section 10 of the duct is enlarged to fOrm the flared or frusto-conical expansion chamber (or, in the case of the modification shown in Figure 2A, an enlarged cylindrical chamber), the volume of section 10 of the duct of length L2 is greater than the volume of section 6 of the duct of length Li. In both instances, diametrically enlarged section 10 of the duct extends as far as the outlet 9.

In the case of section 6 of the duct, the ratio of the length LI of that section to its internal diameter Dl, i.e. Li/Di, is advantageously in the range o 1.00 to 1.40, and preferably substantially 1.20. In the case of' section 10 of the duct, the ratio of the length L2 of that section to the internal diameter 02 of that section, measured at the rim 9, i.e,L2/D2, is advantageously in the range of 0.70 to 1.10, and preferably substantially 0.90. t7

In operation, steam supplied through a lance or conduit to steam inlet 14 flows into the plenum chamber and escapes into the passageway leading to orifice 35, and is thence injected at high velocity into the duct section 6. By virtue of the Coanda effect, the steam attaches to the radially inner surfaces of the lip 32, 33 and radially inner surface of wall 24 and tiows in the downstream direction towards the outlet. A reduction in pressure takes place in the duct and fOod product is drawn towards the inlet to the duct and passes through the inlet and along the duct, being heated and mixed with the steam, and ultimately discharged from outlet. (in being discharged from the apparatus the food product circulates within the kettle.

Herein the term "Coanda surface" will be used to refer to a surface such as the radially inner surfaces of the lip 32, 33 and wall 24 which are so shaped and positioned relative to the orifice to enable the Coanda etlëct to take place as the steam discharged through orifice 35. The steam, flowing in the downstream direction, is substantially attached to the surface of the lip 32, 33 and the radially inner surface of wall 24.

[he steam expands arid collapses into water, or is condensed, within the expansion chamber 10, the frusto-conical or flared shape of which (in the embodiment of Figures 2 and 3) ensures that the size of any remaining globules of steam is controlled, and that in the first mode of operation substantially all of the energy contained in the steam is imparted to the food product.

In the ideal case, all such steam entering the expansion chamber collapses into water, with the result that only water and food product are discharged from the outlet. However, a steam injector in which a c/c minimis Is quantity of steam does not collapse or condense into water within the steam injector but escapes through the outlet, or in which this is contrived deliberately, is to be regarded as tailing within the scope of the invention.

[he optimum shape of an expansion chamber in the case both of the embodiment of Figures 2 and 3 and the modification of Figure 2A may therefore be such as to lead to expansion and collapse of the steam into water, and to be capable of imparting substantially all of the energy remaining in the steam to the food product. the shape and dimensions of the optimum expansion chamber may be determined by experiment, in carrying out such an experiment, it is noted whether, fOr any given shape and dimensions L2, D2, bubbles of steam are emitted from the apparatus and rise to the surtace of a test vessel, or do not do so.

An optimum expansion chamber shape is one in which no bubbles of steam escape in this way, unless intended, or de minim/s1 consistent with achieving maximum throughput of product. Such experiments need to take account of the lengths Li, L2, as well as the diameter and the cone angle of the surface 7. In order to achieve the desired outcome it may be necessary to extend the length L2 of the expansion chamber.

If the downstream end of the duct were to have the same internal cross-sectional diameter as wall 24, turbulence could occur, and globules of steam escape from the apparatus and rise to the surläce of the tood product in the kettle, without the energy in the steam being substantially fully imparted to the fOod product. It will be noted that the radially inner surface of the upstream end of the expansion chamber adjoins, substantially, the downstream end of the radially inner surtáce of wall 24, which is of constant diameter throughout its length. Within the scope of the invention the inner surface 01 the expansion chamber IL) may constitute part of the Coanda surface.

the advantage of undercutting or inclining the wall 23, and giving the section 30 of the wall a concave curvature will be appreciated from tigure)A, where it is shown that by virtue ot such undercutting the steam has a greater tendency to follow the path indicated by arrow X, bemg attached more securely to the lip 32, 33 and the radially inner surface of the wall 24, thereby providing a more effective operation. If, on the other hand, wall 23 is arranged to lie in a plane more precisely normal to the axis of the duct section 6, the steam tends to follow the path indicated by arrow Y and results in less effective operation.

Because the presence of steam within the apparatus or steam injector could result in scalding of the food product contacting the outer surfaces of the body, especially those in line with the plenum chamber, the chambers 16 and 22 serve to thermally insulate the food product relative to hottest zones withm apparatus, and may contain air, a vacuum or partial vacuum, or an insulating material such as a ceramic fibre or Kockwool (trade Mark).

the optimum width of the orifice 35, may be determined by expenment, in which connection the inner and outer body components may be screwed closer together or fOrther apart so as to have different relative positions, the steam injector being tested at intervals. Adjusting the gap between the surfaces 30 and 32 and the width of the orifice can result in different mixing characteristics, so that increasing the gap size results in steam collapsing in larger quantities, and a more vigorous agitation, which could benefit the mixing process in some circumstances. 2U

Setting the optimum gap results in the ideal optimised 110w ot steam through the apparatus, which transfers substantially all of its energy into the tood product. this suppresses the noise 01 the steam (steam hammer as it is termed), which results from steam collapsing into water. Hot gases or vapours, other than steam, may be used in certain alternative circumstances.

Ihe preterred angle at which the expansion chamber is tiared may also be determined by experiment. Although it is preferred for the outlet to open directly trom the expansion chamber, apparatus in which there is a duct portion of constant diameter between the frusto-conical expansion chamber and tne outlet is also intended to tall within the scope ot the invention. For convenience of manufacture, the expansion chamber is circular in cross-section, although it is to be understood that expansion chambers of other cross-sectional shapes (for example, square or elliptical cross-sections) are intended to tat! within the scope 01 the invention.

Within the scope of the invention the expansion chamber may be cylindrical in shape, as depicted m figure 2A, although pertormance will be less controlled than with a flared or frusto-conical expansion chamber.

me toregoing also applies in general terms to the second embodiment, which will now be described It is possible tO vary the throughput 01 the apparatus hereinbelore described by varying its dimensions at the design stage, in particular the internal diameter 01 the duct section 6 and the expansion chamber 10.

However, doubling the internal diameters of the duct, for example, will not necessarily give nse to a doubling or throughput because me intensity of the Coanda effect, or other characteristics of flow through the duct 2i section b, may not be increased in proportion. Iflis problem is overcome by apparatus in accordance with the second embodiment of the invention.

Second embodiment The apparatus according to the second embodiment of the invention shown in Figures b to 9 is in the torm 01 an elongate assembly or structure incorporating and extending transversely of two spaced apart, parallel steam injectors 2L, 2K, each substantially in tne torm 01 the tirst embodiment. The pair of injectors are detachably coupled together. The steam injector 2L is positioned on me ielt-nand side or tigure 1, and steam injector 2R is positioned on the right hand side of Figure 7.

Features or steam injector 2L are suffixed L, and those or steam injector 2R are suffixed R (Figure 9 being referenced for both steam injectors).

1 he steam injectors 2L, 2K are assembled trom outer body components 50L, 50R and inner body components 52R, 52L. The inner body components define respective mlets surrounded by rims L, ?3K, upstream duct sections 6R, 6L and outlets surrounded by rims 9L, 9R.

Downstream sections 01 the ducts constitute expansion chambers H)L, 1 OR, each of flared or frusto-conical shape. A larger diameter cylindrical expansion chamber may be used mstead. Locking rings 02L, 02K are screwed onto the inner body components, and may be reinforced by means or annular auxiliary rings as explained in connection with tne first embodiment.

ZD

The inner body components are also configured to provide walls 24L, 24K which bound the radially inner sides 01 respective plenum chambers 12L, 12R. The upstream end walls of the outer body components are undercut as at 2)L, 2M( with proximal surtaces 20L, 20K and concavely curvec distal surtaces JUL,JIJK, ending in a sharp edge 8L/M(). I ne upstream ends of the walls 24L, 24R are flared radially outwards and terminate in cylindrical edges ilL, 2/K, adjacent to lips.IS2L, 32K racing in the upstream direction. The surfaces 32L, 32R and 30L, 30R define substantially annular passageways terminating in orifices.3 DL, 3)K where the passageways open into the ducts 6L, 6R. The surfaces 32L, 32R and 3JL, 33K serve as (Joanna surtaces, so that the coanda enect comes into play as steam discharges through the passageways and orifices 3 5L, 3 5R.

1 ne way in whicn the steam injectors 2L, 2K operate, including reliance on the Coanda effect to cause steam flow into and through the ducts 6L, bt(, will be understood trom tixe description anu iiiustration or the tirst embodiment, to which reference should be made for a greater understanding or tue second embodiment.

I tie second embodiment differs trom tile tirst with respect to the suppiy of steam to, and its distribution within the apparatus, upstream of orifices 3 DL, .3DK. A single steam inlet passage 14 is provided at one end 01 the structure or apparatus, namely the left hand end (as viewed in Figure 7) ann has associated with it a threaded connector 42 and a peg 44 to enable the apparatus to be secured to a lance without risk of disconnection caused by vibration. I tie passage 14 commumcates with pienum chamber 12L as well as with a tubular passageway 70 which extends to, and communicates with, me plenum chamber 12K. 1 he tubular passageway 70 also serves as a means for coupling steam injector 2L, 2R together.

Kelemng to figures 1 and t, it will ôe seen that, between tiie steam injectors 2L, 2R, the tubular passageway 70 is segmented, being assembled trom a tirsi segment /2 associated with the outer body component 50L and a second segment 74 associated with the outer body component 0K. .1 ne two passageway icngtns may be brought into juxtaposition where their ends abut along line 75 to form the passageway /0. From this position the passageway segments may e drawn apart br cleaning purposes.

Figure ?3 snows, to an enlarged scale the detail at ii'S in Figure 7, comprising a mechanism for bringing the passageway segments into juxtaposition during assembly ana separating them tor disassembly tor cleaning after use. The right hand side edge of passageway segment 72 has an external rim /9 and the iett hand edge 01 the passageway segment 74 has an external rim 78. The rims may be made fast or be integral with tne passageway segments.

n internally tnreaued rmg /0 is provided with an internal screw thread which is screwably engaged with an external screw thread on rim 78.

I he ring /0 is pronie externally see Figure 0) to taciiitate manual rotation and has an annular, radially inwardly projecting shoulder 80 which engages a complementary, radially outwards projecting shoulder 82 on the rim 79 of passageway segment 72.

Rotation ot the nng /0 in a tint direction draws passageway segment /2 towards the right so as to bring the passageway segments into the abutting positions in winch iney are snown. A I'l Ft seai &3 received m a groove in rim 78 of segment 74 engages the rim 79 of passageway segment 72 to prevent leakage ox steam trom between the passageway segments during use. Rotation of the ring in the opposite direction allows shoulder 80 to release tile shoulder 32 so tnat me passageway segment /2 may move to the ien, ultimately mto a position in which the two steam injectors may be separated for cleaning.

tacn 01 tne passageway segments may e assembled Irom a pair or cylindrical components, namely the components 72, 74 which engage each other, anu members 92, 94 whicn are tixecily engagec with outer body components 50L, SOR, respectively.

A cladding rmg 10K bounus a cuamoer I SK provinea tor tnermai Jo insulation purposes where otherwise the radially outer wall of the plenum chamber 12K wouiu be exposed. timer regions or me apparatus are thermally insulated by cladding tubes where shown for example at 96.

I he arrangement uepicteu m t igures b to 9 proviues a convenient approach to incorporating two separate steam injectors into apparatus for injecting or introducing steam into a rood product in order to mcrease throughput of steam and food product, and in such a way that the steam injectors may ne reaaiiy separated tor cleaning. However, other possibilities exist and within the scope of the invention three or more such steam injectors may e grouped togetner, such as in a row or triangular array, and supplied with steam from a common source through an arrangement or passageways. one such alternative arrangement takes the form of the third embodiment to which reference will now be made.

miru embodiment In the case of the third embodiment shown in Figure 10, as viewed from the inlet end, two such steam injectors are incorporateu into a smgie body without any provision for the two steam injectors to be separated one trom the other, as such, although provision is made tor the b0O to be broKen flown tor cieanmg. 10 thiS cnn, the body is manutactured in two pieces, and consists of a base block 2B and a cover block 2C, with mating races tormed with channels or semi-circular cross-section which are mirror images of each other. When the blocks 2B and 2C are brought S together they detine ducts mciuciing expansion chambers or circular cross-section. The blocks may be secured together by fastening means passed through pairs or aligned holes 104. An inlet passage 14 is provided at one end of the base block, and communicates with the left hand duct section 6 (as viewed) and with a passage 102 extendmg through the base block into the right hand duct.

Separate inserts 100 are tuten mto the upstream end or respective ducts.

The inserts are configured so as to contain or cooperate with the body to torm te two pienum chambers, me oritices, and appropriately located Coanda surfaces, all as explained in connection with the first embodiment.

Fourth embodiment The fourth embodiment shown in Figure 11 corresponds generally to that snown in Figures 6 to 9, save that it does not utilise me coanda ettect.

The upstream ends of the plenum chambers 12L, 12R are closed and steam outlets.ibLI, JbK opening through walls 24L, 24K serve to discharge steam at high velocity axially of the ducts in the direction of the outlets. Keterence numerals used in Figure 11 relate to corresponding features found in Figure 7.

Advantages 01 the invention are that the rood product is heated very rapidly with substantially 100% efficiency. Apparatus or steam injectors as described and illustrated may be usen tor reducing starches and as an zG entrainment system tot' starclies and simiiar substances. I tie expansion and collapse of steam which takes place in the expansion chamber gives a mucti mproveci activation. tar tess staren is neeaeo to obtain me same thickening results.

Claims (7)

1. CLAIMS:- 1. Apparatus for processing fluid substances comprising a body through which extends a duct, an orifice opening into the duct for the introduction therein of primary fluid, an inlet for secondary fluid at an upstream end of the duct and an outlet for secondary fluid at a downstream end of the duct, the orifice being located closely adjacent to the inlet for secondary fluid, the duct having upstream and downstream sections, the cross-sectional area of the downstream section being at least on avenge greater than that of the upstream section, and means for causing primary fluid to flow through the duct towards the outlet, such as to entrain secondary fluid.
2. 2. Apparatus as claimed in claim 1, wherein the upstream section of the duct is of substantially constant cross-section throughout its length and the downstream section thereof is in the form of an expansion chamber of cylindrical, or outwardly flared, or frusto-conical shape.
3. 3. Apparatus as claimed in claim 1 or claim 2, wherein a passage opens from a plenum chamber into the orifice, the orifice being bounded by a concave annular surface on its upstream side with respect to the duct and by a convex annular surface on its downstream side with respect to the duct, said concave surface being closely adjacent to a rim surroundng the inlet.
4. 4. Apparatus as claimed in claim 3, wherein the concave surface is recessed or set back into a downstream facing surface of the rim.
5. D. apparatus as ciaimea in any precening ciaim, inciuning a piuranty 01 said bodies, detachably coupled one to another.
6. 6. apparatus as ciaimeo in ctaim 5, wnerein me nornes are arrangea in spaced apart parallel relationship and form a structure extending transverseiy or me axes or me owes, ann wnerem an iniet ror primary fluid is located at one end of the structure.
7. 7. apparatus as ciaimeo in claim o, wnerein me iniet ror primary nuic communicates firstly with a duct adjacent the inlet, and secondly with a tuuiar passageway extenaing iengtnwise or me structure ror suppiying primary fluid to a plenum chamber associated with a duct remote from me miet.i zs. apparatus as ciaimeu in ciaim 7, wnerein me ornes are netacnarny coupled together by the tubular passageway.9. apparatus as ciaimea in ciaim 1 or ciaim 8, wnerein me tuoutar passageway is segmented such that a first segment thereof is associated wan a urst one or sam owes ann a secona, separate segment mereor is associated a second one of said bodies, said segments of the tubular passageway naving operative positions in wnicn tneirjuxtaposeo enos abut each other.n iii apparatus as ciammen in ciaim 9, mciunmg means ror nispiacing tne first segment of tubular passageway relative to the second segment to cause or aiiow juxtaposen enos or me sam segments to come into abutment one with another or to be separated one from another.ii. apparatus as ciaimee in ciaim 5' or ciami lu, inciuamg seanng means positioned to resist leakage of primary fluid from between abutting enus or me segments or me tuouiar passageway.]2. ppararus as ciaimeu in any or ciaims s' to ii, wnerein means ror displacing the first segment of the tubular passageway relative to the secona segment comprises a manuatty rotaraoie ring aisposea oetween the bodies, the ring being screwably associated with one segment of moutar passageway ann arrangeci to cooperate wan me otner segment oi tubular passageway, whereby rotation of the ring in one direction causes inc juxtaposea enas or inc segments to anut eacn orner.i3. apparatus as ciatmea in any or ciaims i to z, wnerein me or eacn body comprises two body components sleeved one over the other and i screwaoiy mterconnectea, respective ooay components or me or eacn body being provided with annular surfaces defining upstream and ciownstream sines or me oririce, a gap oerween sate surraces oeing variable in size by adjusting the relative positions of said components.1 #. apparatus as ciaimea in any or ciaims I to ia, wnerein a uoanoa surface is provided in the or each duet in the region of the orifice.iS, apparatus ror usc in processing fiowaoie rooa procucts comprising a body through which a substantially unobstructed rectilinear duct extends 23 netween an iniet ror roon prociuct at one enu mereor ann an ounet ror food product at the other end thereof, a plenum chamber associated with an upstream section or me auct, means ror aamnung steam into me plenum chamber, an orifice opening from the plenum chamber into the ciuct proximate me inter tnereto, a uoanaa surrace ror causing steam to hOW tnrougn tne auci towarus inc ouuet anu entrain ioou prouuet, a flared or frusto-conical downstream section of the duct constituting an expansion cnamoer witmn wnicn steam conuenses into water anu energy contained in the steam is imparted to food product.16. A method of processing fluids in which a primary fluid is received wnnin a pienum cnamoer anti is uiscnargeu wereirom ny way o an orifice into a duct, the primary fluid being caused to flow through the ouct towarus an ouuet at a uownstream enu inereot anti in so uomg uraw secondary fluid into the duct through an inlet at an upstream end thereof, we seconuary uuio neing propeiieu towarus anti tnrougn inc outlet; a downstream section of the duet having a cross-sectional area sreater on average man mat 01 Inc upstream section.vi. n metnou as ciaimeu in etaim 16, wnerein me oownseam section 01 the duct constitutes an expansion chamber in which substantially all of me energy containea in me primary uuiu is impaneo to seconuary nub.iS. n metnou as ciaimeo in ciaim to or ciaim i7, wnerein me primary fluid is steam, substantially all of which condenses into water within the expansion enamoer.1,. A memoa as ciamteo any of ciaims ibm claim i, wnerein tne primary fluid is steam and the secondary fluid is a flowable food product, 2) me moo proouci oeing neateo oy me steam curing me passage or steam and food product through the duct.20. 1-1 metnou as eiaimeu in any of eiaims to to i9, wnerein we primary fluid is caused to flow through the duct towards the outlet under the action ot we uoanua enect. ii. a mewou as ciatmea in any oi eiaims io to zu, wnerein inc secondary fluid is a flowable food product Zt. apparatus tot processing itutu suostances comprising a oouy through which extends a duct, an orifice opening into the duct for the to tntrooucuon inerein ot primary uuiu, an inlet tor seconuary nuiti at. an upstream end of the duct and an outlet for secondary fluid at a uownstream enu 01 inc uuct, inc uuci naving upstream anti uownstream sections, the cross-sectional area of the downstream section being at least on average greater titan mat ot inc upstream section, anti means tor causing primary fluid to flow through the duct towards the outlet, such as to entrain seconuary nuiu.z.. apparatus as ctaimeu in any ot ciaims i. to i'+, wnerein caviues are provided to thermally insulate the body or bodies. 2v24. A method substantially as hereinbefore described with reference to tue urawings.25'. apparatus suosutnuany as nereinoesore uescrioeu wiui reicrence to and as illustrated in Figures 1 to 5 and 5A, Figures 6 to 9, or Figure 10, or r igure i 1 01 IIIC urawings