US3871446A

US3871446A - Mixer cooler

Info

Publication number: US3871446A
Application number: US286949A
Authority: US
Inventors: Hartmut Langenberg
Original assignee: Dierks and Soehne GmbH and Co KG
Current assignee: Dierks and Soehne GmbH and Co KG
Priority date: 1971-09-17
Filing date: 1972-09-07
Publication date: 1975-03-18
Anticipated expiration: 1992-03-18
Also published as: GB1371831A; FR2152597B1; FR2152597A1; DE2146611A1

Abstract

A mixer cooler having a mixing tool operating in a double walled mixing vessel, the cavity between the walls of the mixing vessel being subdivided by guide elements into a coolant duct which extends in labyrinthine fashion between a coolant inlet and a coolant discharge.

Description

llnited States Patent [191 Langenberg 1 Mar. 18, 1975 1 MIXER COOLER [75] Inventor: HartmutLangenberg,Buer,

Germany [73] Assignee: Dierks & Sohne, Osnabruck,

Germany [22] Filed: Sept. 7, 1972 [21] Appl. No.: 286,949

[30] Foreign Application Priority Data Sept. 17, 1971 Germany 2146611 [52] US. Cl 165/109, 165/169, 259/DIG. 18 [51] Int. Cl F28f 13/12 [58] Field of Search 165/109, 169; 259/D1G. 18

[56] References Cited UNITED STATES PATENTS 1,693,249 11/1928 Pauly 165/169 1,922,534 8/1933 Ellsworth et a1 165/169 1,992,988 3/1935 Blahnik 165/109 X 2,214,344 9/1940 Paul 165/169 X 10/1943 Higley 165/109 X 2,545,371 3/1951 Mojonnier et a1. 165/169 X 2,557,622 6/1951 2,602,648 7/1952 3,099,315 7/1963 3,554,274 l/1971 3,565,168 2/1971 Powell et a1. 165/169 X FOREIGN PATENTS OR APPLICATIONS 635,970 9/1936 Germany 165/169 212,607 8/1906 Germany 165/169 703,374 2/1954 United Kingdom 219/535 Primary Examiner-Albert W. Davis, Jr. Assistant Examiner-S. J. Richter [57] ABSTRACT A mixer cooler having a mixing tool operating in a double walled mixing vessel, the cavity between the walls of the mixing vessel being subdivided by guide elements into a coolant duct which extends in labyrinthine fashion between a coolant inlet and a coolant discharge.

10 Claims, 11 Drawing Figures [I 257 if a-mmin 1 8 s SHEET 2 UP 5 fig.)

MIXER COOLER The present invention relates to a mixer-cooler of the kind having a mixing vessel and a mixing tool arranged therein and designed to rotate about a vertical axis coinciding with the vessel axis, the mixing vessel being a double-walled vessel whose internal and external walls define between them a space through which a coolant flows", in said space guide elements being provided to guide the coolant on its passage between a coolant inlet in the base and a coolant discharge means in the neighbourhood of the vessel rim.

In mixer-coolers of this kind that have been proposed heretofore, the guide elements arranged in the cavity of the double wall were employed to form a by-pass flow between the coolant inlet and the coolant discharge and thus cut off parts of the double wall from the coolant flow. The normally solid, e.g., forged and machined, mixer tools extend radially from a hub mounted on a drive shaft, and generally take the form of a multiple beater tool set. As they rotate, they cause the material being mixed to adopt a funnel-shaped flow pattern in the course of which the material, which at the same time is driven with a giratory motion about the vessel axis, rises up the internal wall of the mixing vessel, out of the plane of operation of the mixing tools and, reversing its direction of motion downwards and inwards, returns to the zone of operation of the mixing tools again. Because it moves up overthe cool internal wall of the mixing vessel, the material being mixed gradually dissipates its heat.

The cooling performance of mixer-coolers of this kind with heat transfer through the vessel wall, is unsatisfactory. To improve the cooling performance, therefore, in accordance with an older proposal, a cooling gas is blown into the mixing space to provide direct heat exchange in addition to the existing indirect heat exchange.

The object of the present invention is to improve the cooling performance of mixer-coolers of the kind above described, in terms of their indirect heat exchange, without incurring anyappreciable extra cost of construction.

The present invention is a mixer-cooler, consisting of a mixing vessel and a mixing tool arranged therein and designed to rotate about a vertical axis coinciding with the axis of the vessel, the mixing vessel being a doublewalled vessel whose internal and external walls define between them a jacket or space through which a coolant flows, in said space guide elements being provided to guide the coolant on its passage between a coolant inlet in the base and a coolant discharge means in the neighbourhood of the vessel rim. The guide elements subdivide the jacket into a coolant duct extending in labyrinthine fashion from the coolant inlet to the cool ant discharge. In this context, at least in the radially outermost part of the base cavity of the double wall, the flow duct may consist of concentric duct sections constituted by guide baffles extending substantially concentrically to the vessel axis; each of which duct sections extends over an angle subtended at the centre of around 360 and is connected through a radial transfer orifice with the particular adjacent, radially outer duct section, in a series arrangement. Furthermore, the flow duct may be formed in the side-wall zone of the double wall, by duct sections formed by guide baffles disposed coaxially and at intervals, parallel one above the other in the cavity, each of which duct sections extends through an angle subtended at the centre, of 360, and

communicates through an axial transfer orifice with the particular adjacent axially upper duct section in a series arrangement. With this kind of design, the coolant is made to follow a precisely defined flow path, uniformly involving the entire vessel, as a consequence of which the formation of unwanted temperature differences in certain zones of the internal wall, is effectively avoided. The temperature of the internal wall can be readily and accurately controlled with this kind of flow guidance, and a high degree of uniformity can be attained. Even at relatively low rates of coolant flow it is possible, due

to the effectiveness of the heat transfer which can be achieved between the internal wall of the double wall structure and the coolant, to attain at the internal wall of the vessel comparatively low temperatures, very little in excess of that of the coolant itself.

A further substantial increase in cooling performance on the part of mixer-coolers of this kind can be achieved by designing the mixer tools so that the lead ing face, considered in the direction of rotation of each tool, has an alignment which is tangential to the peripheral surface of the hub. Preferably, in this embodiment, the front side of the mixer tools will be formed by an overall working face made up of working face sections of substantially flat form inclined at different angles to the horizontal underface of the tools. Preferably, it will be arranged that the front side of the mixer tools presents, in the zone adjacent the hub, an internal working face section which makes an angle with the under face of the tools of to this angle being open towards the direction of rotation. Furthermore, the front side of the mixer tools can be provided in the neighbourhood of the external end with an external working face section which makes an angle with the underface of the tools, of about 45, this angle being open towards the direction of rotation. In accordance with yet another embodiment, the mixer tool is further provided with an intermediate working face forming a transition from the internal to the external workingface sections, said intermediate face having an inclination corresponding substantially to that of the external working face section. This kind of design of the mixer tools gives them a substantially better displacement effect coupled with reduced flow resistance, so that the material being mixed, while developing less frictional heat, is given a flow velocity which is relatively high compared with the peripheral speed of the mixer tools. Coupled with reduced drive power for the operation of the mixer tools, the high flow velocity of the material being mixed gives rise to improved heat transfer between it and the internal wall of the mixer vessel, so that overall the mixer achieves a cooling performance which is considerably superior to that of previously known mixers.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a view in a partially cut-away overall side elevation of a mixer-cooler in accordance with the invention;

FIG. 2 is a partially cut-away plan view of the mixercooler of FIG. 1;

FIG. 3 is an overall end elevation of the mixer-cooler shown in FIGS. 1 and 2;

FIG. 4 is a view partially in side elevation and partially in vertical section of the mixing vessel of the mixer cooler shown in FIGS. 1 to 3;

FIG. 5 is a schematic view in horizontal section of the flow duct in the cavity of the double wall of the mixer vessel, in the neighbourhood of the base thereof;

FIG. 6 is a view in plan of a mixer tool set;

FIGS. 7 and 8 are side elevations relating to FIG. 6; and

FIGS. 9 to 11 are simplified sectional illustrations through a mixer tool, the sections being taken respectively on the lines IX, X and XI of FIG. 7.

The mixer illustrated in the drawing consists of a mixing vessel 1 in which a set 2 of mixer tools is designed to rotate. The mixing vessel 1, set up upon a machine bed 3, has a substantially circular cylindrical form. The vessel axis 4 corresponds with the axis of rotation of the set of mixer tools. The top of the mixer vessel 1 is closed off by a cover or the like. To fill the internal cavity 5 of the mixer vessel 1, a closable hatchway 6 is provided. The removal of the cooled mixed material from the interior 5 is carried out through a lateral discharge orifice which can be closed and opened by means of a device 7. A delivery connection 8 of the cooling air blower 9 by means of which cooling air or some other suitable cooling gas is blown into the interior 5 of the vessel 1 during operation opens tangentially into the interior 5 of the mixer vessel 1. On the cover 10, which contains an air vent orifice 11, there is a filter dome 12 where any particles of the material being mixed, which have been entrained by the exiting air, are filtered out and retained. To drive the mixer tool set 2, an electric motor 13 housed in the machine bed 3, is provided, this motor, through a transmission 14 rotating a vertical drive shaft 15 whose top end extends through the vessel base. On the top end of the drive shaft a hub 16 is secured and above this a guide cone or spinner 17. This guide cone 17 serves to prevent deposits of material collecting at the centre of the mixing vessel 1, and rapidly returns material entering the central zone of the vessel, to the field of operation of the mixer tool set 2.

The mixer vessel 1 has a double wall, the outer wall being designated 18 and the inner wall 19. The double wall includes the sidewall and base portions of the mixer vessel 1. The cavity 20 between the walls conducts a coolant, e.g. water, which is injected near to the centre of the base zone and is discharged from the upper cavity level with the rim of the vessel. The coolant discharge is indicated at 21 and comprises a discharge orifice 22 formed in the external wall 18. The coolant inlet (FIG. 4) consists of an inlet connection 23, in the external base wall 18 of the vessel 1. It goes without saying that this coolant inlet connection 23 is connected in an appropriate manner to the coolant source, the injection of the coolant being carried out and controlled by means of a pump, for example, which has not been shown.

The design of the mixing vessel 1 can be seen particularly clearly in FIGS. 4 and 5. In the base of the mixer vessel 1, there is provided first of all a central opening 24 to pass the drive shaft 15. This opening 24 is surrounded by an annular element 25 which closes off the cavity 20 between the base-side internal wall 19 and external wall 18' from the opening 24. The base side internal wall 19' of the mixing vessel 1 seats against a ring-mounting 26 arranged concentrically with the ring element 25, which mounting extends through the base cavity 20' and projects downwards beyond the baseside external wall 18'. By means of this ring mounting 26, the mixer vessel 1 as a whole is supported upon the machine bed 3. In order to connect that zone 20' of the cavity, which is located concentrically inside the ring mounting 26, with that zone 20" of the cavity located concentrically outside, a radical transfer orifice 26' is provided in the ring mounting 26. The cavity 20 between the

ring elements

25 and 26 is subdivided by a guide baffle 27 disposed concentrically vis-a-vis the vessel axis 4. This guide baffle 27, which, like the other guide baffles to be described later, may consist of bar material of round or rectangular (e.g. square) crosssection, and is in sealing contact both with the internal wall and with the external wall of the double-walled vessel, defines a flow duct section 28 in relation to the inner ring element 25, and in relation to the ring mounting 26 defines a flow duct section 29. The two

duct sections

28, 29 communicate with one another through a transfer orifice 30. This transfer orifice 30 is disposed diametrally opposite the inlet connection 23 (considering the vessel axis 4.) That zone 20" of the cavity between internal and external walls of vessel 1, which extends concentrically outside the ring mounting 26 in the base zone of the vessel, is in turn subdivided by guide baffles 31,32,33 into

duct sections

34, 35, 36 and 37. In accordance with a concentric arrangement of the guide baffles 31,32 and 33, the duct sections 34,'

35, 36 and 37 are also disposed concentrically vis-a-vis the vessel axis 4. As FIG. 5 shows more clearly, a racial baffle 38 is provided in the cavity 20" baffle 38 extending from the ring mounting 26 and is connected to one end 31', 32', 33' of each of the guide baffles 31, 32, 33. The other ends 31", 32" and 33" of the concentric guide baffles 31, 32 and 33 respectively, in each case terminate at an interval before the radial guide baffle 38, thus forming

radial transfer orifices

39, 40 and 41 respectively. This kind of design means that each

duct section

34, 35, 36 and 37 extends through a centrally subtended angle of around 360, each duct section communicating with its particular adjacent, radially outer section, through the associated transfer orifice. The

duct sections

34, 35, 36 and 37 are connected in series with one another from the flow point of view so that the coolant, as it passes through the coolant jacket, is forced to follow a labyrinthine path. This flow path of the coolant entering through the transfer orifice 26 in the ring mounting 26, into the duct section 34, has been indicated in FIG. 5, to which express reference is now made, by the curved arrows in such figure. These show how the flow direction is reversed from one duct section to the next, in each case after the coolant has traversed a subtended angle of around 360. The flow is somewhat different in the case of the specially designed vessel base in the zone concentrically within the ring mounting 26, as the arrows in FIG. 5 indicate. In this central, inner zone 20' of the cavity, there is a change in flow direction after a centrally subtended angle of only 180.

After flowing through the

duct sections

28, 29 in the zone 20 of the cavity and then flowing through the

duct sections

34, 35, 36 and 37 in the zone 20" in the cavity, the coolant enters the side wall Zone 20 of the cavity 20 between the external 18 and internal l9 walls of the mixer vessel 1. This cavity 20" is in turn subdivided by horizontal guide baffles arranged coaxially at intervals, one above the other, the baffles being designated 42, 43, 44, 45, 46 and 47 in FIG. 4. These guide baffles define between them

duct sections

48, 49, 50, 51, 52 and 53 of which the duct section 53 is closed off at the top by an element 54 which forms the top closure of the cavity The duct sections 48 to 53 are in turn connected in series with one another so that coolant leaving the duct section 33 and entering the duct section 48 through a transfer orifice (not shown) near the radial guide baffle 38, first of all flows through the duct section 48, then the duct section 49, and so on, until it flows out from duct section 53, at 22. In order also to create a flow pattern in the sidewall of the vessel which fundamentally coincides with that in the external base zone of the vessel, the guide baffles 42 to 47 are likewise in each case connected at one end to an axial guide baffle 55 whilst their particular other ends termi nate at a certain distance short of this. For example, the guide baffle 44 is attached by its end 44, the guide baffle 45 by its end 45', and the guide baffle 46 by its end 46, to the axial guide baffle 55 in the cavity 20". Furthermore, for example the ends 44", 45" and 46" of the guide baffles 44, 45, 46 respectively, are arranged at an interval from the radial guide baffle 55 in order to define in relation thereto transfer

orifices

56, 57 and 58, respectively. The flow pattern is once again indicated by arrows in the cut-away part of FIG. 4.

Through the described design, an overall flow passage constituted by the

duct sections

28, 29 34, 35, 36, 37. 48, 49, 50, SI, 52 and 53 is formed; such flow passage extends from the coolant inlet at 23 to the coolant discharge at 22 and causes the coolant to follow a clearly defined, labyrinthine path which uniformly covers the entire vessel wall. The guide baffles can have a mutual disposition such as to ensure that the flow duct between the inlet at 23 and the discharge at 22 has the same flow cross-sectional area throughout, so that the flow velocity of the coolant remains the same throughout the entire coolant passage. Instead of this, however, it is possible, by suitable choice of the flow crosssectional area in individual duct sections, locally temporarily to increase or comparatively reduce the coolant flow velocities. This is useful at points in the vessel where, because of the incidence of material being mixed, there is particularly intense heat development, since it permits the more effective dissipation of the heat transferred to the internal wall 19 of the vessel. Overall, the flow cross-sectional area of the flow duct is relatively small so that even at relatively low coolant flow rates, relatively high flow velocities can be achieved there. By controlling the coolant pump performance, it is possible furthermore to increase or reduce the heat exchange between the internal wall 19 of the vessel and the coolant.

The set 2

ofmixer tools

59, 60, 61, illustrated in more detail in FIGS. 6 to 11, cooperates in a special way to assist the mixer-cooler to achieve a particularly high cooling performance. The

mixer tools

59, 60, 61 initially have their front side (considered in the direction of rotation) running tangentially into the circumferential surface of the hub 16. Through this disposition on the front side of the mixer tools, the material being mixed is imparted a direct radial component of movement, corresponding with the direction of the centrifugal force, so that in contrast to the case which would obtain with radial alignment of the mixer tools, where the material would simply be given a circumferential component of movement, the radial motion being due entirely to centrifugal force in that case, the material acquires a particularly strong outwardly accelerated flow.

The front side of the mixer tools, furthermore, present a total working face which is made up of individual working face sections. These working face sections have differing inclinations vis-a-vis the horizontal underface of the tools. In the example illustrated, the overall working face at the front side of the tool. is made up of three sections (62, 63 and 64). The steep face 62 includes the zone adjoining the hub 16 and makes an angle of between and with the base 65, which angle is open towards the direction of rotation. By means of the thus relatively steeply angled, substantially flat, internal working face 62, the material being mixed is given a circumferential and outward flow, the upward component being so slight that it is sufficient merely to prevent clogging at the base but does not prevent an effective upward motion on the part of the material.

The face section 64 includes the external end zone of the front side of the mixer tools, and makes an angle of about 45 with the base of the tools, which angle is open in the direction of rotation. This external face sec tion is enlarged scoop fashion and has a dimension in the direction of the axis 4 which is 2 to 3 times the corresponding dimension of the face section 62. The relatively small angle of inclination means that the material being mixed is given a particularly strong upward acceleration. The face section 63 is an intermediate face constituting a transition from the inner face section 62 to the outer face section 64. It is substantially triangular in shape with the apex located at the front edge of the mixer tool at the level of the base and at the transition between internal and external face sections. Its inclination corresponds substantially to that of the external face section 64. As far as the disposition of the lines of intersection or junction edges, between the face section 62 and the face section 64, on the one hand, and the intermediate face 63, on the other, is concerned, reference should be made to FIGS. 6 to 8. I

The face section 64 tapers upwards in width and in that of its zones disposed towards the internal wall of the mixer vessel 1, terminates in a rounded outer edge. Considered in relation to the front side of the mixer tools, the inner working face section extends over about 75 percent of the total tool length, measured at the front edge at the level of the base of the tool. The working face section 63 commences at about the midlength of the mixer tool and, measured at its top terminal edge, extends over about 25 to 30 percent of the total tool length. Measured at the front edge ofthe tool, approximately at the level of the base, the face section 64 occupies about 25 percent of the total length of the tool and reduces, up to its upper terminal edge, to about 20 percent of the total tool length. The radius of the hub 16 has a ratio of about 1:3 to the total length of the tool measured at the latters front side. At the base, the cone or spinner 17 has a diameter corresponding to the diameter of the hub 16. The height of the cone is about twice the axial height of the face section 64.

A particularly cheap embodiment of the mixer tools is one in which these are formed as a hollow welded fabrication, embodying a tube section 66 as the main mounting. This tube section 66, with that of its areas which, in the direction of rotation, is located in the lee,

forms the rearward trailing edge of the mixer tool. The top and base sides of the tool as well as the working face sections, are formed by pieces of plate which are welded both to the tube section 66 and to one another.

It goes without saying that the external surfaces of the tool are machined to form a smooth surface, the weld seams being polished in particular.

I claim:

1. A mixer-cooler, comprising a mixing vessel into which a substance to be mixed may be introduced, a mixing tool arranged therein and designed to rotate about a vertical axis, the mixing vessel having internal and external walls defining between them a cavity through which a coolant flows, the mixing tool being configured to propel the substance radially outwardly along the base of the vessel and thereafter up the internal wall of the vessel, a coolant inlet in the base of the vessel and a coolant discharge near the upper rim of the vessel, guide elements in said space to guide the coolant on its passage between the coolant inlet and the coolant discharge in a direction generally corresponding to the direction of propulsion of the substance, the guide elements subdividing the cavity of the double wall into a coolant duct extending in labyrinthine fashion from the coolant inlet to the coolant discharge in at least the radially outer zone of the base-side cavity of the double wall, the flow duct consisting of concentric duct sections formed by guide baffles extending substantially concentrically to the vessel axis each of which duct sections extends over a centrally subtended angle of around 360 and communicates through a radial transfer orifice with the particular adjacent, radially outer duct section in a series disposition, the flow duct in the side wall zone ofthe double wall being made up of duct sections defined by guide baffles arranged coaxially, at intervals, parallel one above the other in the cavity, each of said duct sections extending over a centrally subtended angle of 360 and communicating through an axial transfer orifice with the particular adjacent, axially upper duct section in a series disposition.

2. A mixer-cooler as claimed in claim 1 in which the flow duct presents a substantially unchanged flow cross-sectional area in the zone between the coolant inlet and the coolant discharge.

3. A mixer-cooler as claimed in claim 1, in which the flow cross-sectional area of the flow duct has locally different dimensions between the coolant inlet and the coolant discharges.

4. A mixer-cooler as claimed in claim 3, in which the guide baffles are made of bar material.

5. A mixer-cooler as claimed in claim 4, comprising a central drive shaft having a hub, and a multiple set of mixer tools identical to one another and attached to the central hub, the front side, considered in the direction of rotation, of the mixer tools having a tangential alignment to the circumference of the hub.

6. A mixer-cooler as claimed in claim 5, in which the front side of the mixer tool has an overall working face made up of working face sections which are substantially flat and inclined at different angles to the horizontal base of the tool; said front side of the mixer tools in the zone adjacent the hub presents an inner face section makingan angle of between and with the base of the tools, which angle is open towards the direction of rotation; and in which the front side of the mixer tools, in the neighborhood of the external end, presents an external face section making an angle of about 45 with the tool base which angle is open towards the direction of rotation.

7. A mixer-cooler as claimed in claim 6 including an intermediate face section forming a transition between the inner and external face sections, which intermediate section has an inclination substantially corresponding tothat of the outer face section.

8. A mixer-cooler as claimed in claim 7, in which the intermediate face section has substantially the shape of a triangle whose apex is located at the front edge of the mixer tool at the level of the base and at the transition between inner and external face sections.

9. A mixer-cooler as claimed in claim 8, in which the external face section has a dimension which substantially exceeds the dimension of the inner face section in the direction of the vessel axis. 4

10. A mixer-cooler as claimed in claim 8, characterised in that the mixer tools take the form of a welded hollow fabrication made up of a tube section as the main mounting, and pieces of plate.

Claims

1. A mixer-cooler, comprising a mixing vessel into which a substance to be mixed may be introduced, a mixing tool arranged therein and designed to rotate about a vertical axis, the mixing vessel having internal and external walls defining between them a cavity through which a coolant flows, the mixing tool being configured to propel the substance radially outwardly along the base of the vessel and thereafter up the internal wall of the vessel, a coolant inlet in the base of the vessel and a coolant discharge near the upper rim of the vessel, guide elements in said space to guide the coolant on its passage between the coolant inlet and the coolant discharge in a direction generally corresponding to the direction of propulsion of the substance, the guide elements subdividing the cavity of the double wall into a coolant duct extending in labyrinthine fashion from the coolant inlet to the coolant discharge in at least the radially Outer zone of the base-side cavity of the double wall, the flow duct consisting of concentric duct sections formed by guide baffles extending substantially concentrically to the vessel axis each of which duct sections extends over a centrally subtended angle of around 360* and communicates through a radial transfer orifice with the particular adjacent, radially outer duct section in a series disposition, the flow duct in the side wall zone of the double wall being made up of duct sections defined by guide baffles arranged coaxially, at intervals, parallel one above the other in the cavity, each of said duct sections extending over a centrally subtended angle of 360* and communicating through an axial transfer orifice with the particular adjacent, axially upper duct section in a series disposition.

6. A mixer-cooler as claimed in claim 5, in which the front side of the mixer tool has an overall working face made up of working face sections which are substantially flat and inclined at different angles to the horizontal base of the tool; said front side of the mixer tools in the zone adjacent the hub presents an inner face section making an angle of between 75* and 85* with the base of the tools, which angle is open towards the direction of rotation; and in which the front side of the mixer tools, in the neighborhood of the external end, presents an external face section making an angle of about 45* with the tool base which angle is open towards the direction of rotation.

7. A mixer-cooler as claimed in claim 6 including an intermediate face section forming a transition between the inner and external face sections, which intermediate section has an inclination substantially corresponding to that of the outer face section.

9. A mixer-cooler as claimed in claim 8, in which the external face section has a dimension which substantially exceeds the dimension of the inner face section in the direction of the vessel axis.