WO2018081664A1

WO2018081664A1 - Liquid metal viscosity control of molten glass

Info

Publication number: WO2018081664A1
Application number: PCT/US2017/058910
Authority: WO
Inventors: Samir Biswas; Bulent Kocatulum; Michael Yoshiya Nishimoto; Yuriy YURKOVSKYY
Original assignee: Corning Incorporated
Priority date: 2016-10-31
Filing date: 2017-10-28
Publication date: 2018-05-03
Also published as: TW201821377A

Abstract

A method and apparatus for controlling the viscosity of a glass melt flowing through a glass processing conduit. The viscosity of the glass melt can be controlled by controlling the temperature and flow rate of a liquid metal, such as tin, flowing through the heat transfer conduit, which extends around at least a portion of the glass processing conduit.

Description

LIQUID METAL VISCOSITY CONTROL OF MOLTEN GLASS

[0001] This application claims the benefit of priority under U. S.C. § 119 of U.S.

Provisional Application Serial No. 62/415,098, filed on October 31, 2016, the content of which is relied upon and incorporated herein by reference in its entirety.

Field

[0002] The present disclosure relates generally to apparatuses and methods for controlling the viscosity of molten glass and more particularly to apparatuses and methods for controlling the viscosity of molten glass using liquid metal as a heat transfer medium.

Background

[0003] In the production of glass articles, such as glass sheets for display applications, including televisions and hand held devices, such as telephones and tablets, there is a continual need to improve the efficiency of glass manufacturing processes, including extending the useful life of capital equipment used in such processes. In glass sheet manufacturing processes, such as the fusion down-draw process, a glass forming body can experience a gradual change in shape during the production campaign. For example, as a result of being exposed to elevated temperatures over extended periods of time, a glass forming body may experience sag. Such sag can be counteracted by, for example, changing the relative mass flow of molten glass over the ends of the glass forming body relative to the mass flow of molten glass over the middle. Such mass flow changes can be achieved by adjusting the viscosity at which the molten glass arrives at the glass forming body.

Accordingly, it would be desirable to have a robust and reliable way to control the viscosity of molten glass during the production of glass articles.

SUMMARY

[0004] Embodiments disclosed herein include a method for controlling a viscosity of a glass melt flowing through a glass processing conduit. The method includes flowing a liquid metal through a heat transfer conduit that extends around at least a portion of the glass melt flowing through the glass processing conduit. The method also includes controlling a temperature and flow rate of the liquid metal flowing through the heat transfer conduit relative to a temperature and flow rate of the glass melt flowing through the glass processing conduit in order to control the viscosity of the glass melt flowing through the glass processing conduit to be within a predetermined range.

[0005] Embodiments disclosed herein also include an apparatus for controlling a viscosity of a glass melt flowing through a glass processing conduit. The apparatus includes a heat transfer conduit extending around at least a portion of a glass processing conduit. The apparatus is configured to control a temperature and flow rate of a liquid metal flowing through the heat transfer conduit relative to a temperature and flow rate of the glass melt flowing through the glass processing conduit in order to control the viscosity of the glass melt flowing through the glass processing conduit to be within a predetermined range.

[0006] Additional features and advantages of the embodiments disclosed herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the disclosed embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0007] It is to be understood that both the foregoing general description and the following detailed description present embodiments intended to provide an overview or framework for understanding the nature and character of the claimed embodiments. The accompanying drawings are included to provide further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description serve to explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a schematic view of an example fusion down draw glass making apparatus and process;

[0009] FIG. 2 is a schematic front view of an example liquid metal system for controlling the viscosity of glass melt flowing through an inlet conduit of a forming apparatus; and

[0010] FIG. 3 is a schematic side view of the embodiment illustrated in FIG. 2.

DETAILED DESCRIPTION

[0011] Reference will now be made in detail to the present preferred embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings.

Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0012] Ranges can be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, for example by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0013] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0014] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0015] As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a" component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0016] Shown in FIG. 1 is an exemplary glass manufacturing apparatus 10. In some examples, the glass manufacturing apparatus 10 can comprise a glass melting furnace 12 that can include a melting vessel 14. In addition to melting vessel 14, glass melting furnace 12 can optionally include one or more additional components such as heating elements (e.g. , combustion burners or electrodes) that heat raw materials and convert the raw materials into molten glass. In further examples, glass melting furnace 12 may include thermal management devices (e.g., insulation components) that reduce heat lost from a vicinity of the melting vessel. In still further examples, glass melting furnace 12 may include electronic devices and/or electromechanical devices that facilitate melting of the raw materials into a glass melt. Still further, glass melting furnace 12 may include support structures (e.g., support chassis, support member, etc.) or other components.

[0017] Glass melting vessel 14 is typically comprised of refractory material, such as a refractory ceramic material, for example a refractory ceramic material comprising alumina or zirconia. In some examples glass melting vessel 14 may be constructed from refractory ceramic bricks. Specific embodiments of glass melting vessel 14 will be described in more detail below.

[0018] In some examples, the glass melting furnace may be incorporated as a component of a glass manufacturing apparatus to fabricate a glass substrate, for example a glass ribbon of a continuous length. In some examples, the glass melting furnace of the disclosure may be incorporated as a component of a glass manufacturing apparatus comprising a slot draw apparatus, a float bath apparatus, a down-draw apparatus such as a fusion process, an up- draw apparatus, a press-rolling apparatus, a tube drawing apparatus or any other glass manufacturing apparatus that would benefit from the aspects disclosed herein. By way of example, FIG. 1 schematically illustrates glass melting furnace 12 as a component of a fusion down-draw glass manufacturing apparatus 10 for fusion drawing a glass ribbon for subsequent processing into individual glass sheets.

[0019] The glass manufacturing apparatus 10 (e.g., fusion down-draw apparatus 10) can optionally include an upstream glass manufacturing apparatus 16 that is positioned upstream relative to glass melting vessel 14. In some examples, a portion of, or the entire upstream glass manufacturing apparatus 16, may be incorporated as part of the glass melting furnace 12.

[0020] As shown in the illustrated example, the upstream glass manufacturing apparatus 16 can include a storage bin 18, a raw material delivery device 20 and a motor 22 connected to the raw material delivery device. Storage bin 18 may be configured to store a quantity of raw materials 24 that can be fed into melting vessel 14 of glass melting furnace 12, as indicated by arrow 26. Raw materials 24 typically comprise one or more glass forming metal oxides and one or more modifying agents. In some examples, raw material delivery device 20 can be powered by motor 22 such that raw material delivery device 20 delivers a predetermined amount of raw materials 24 from the storage bin 18 to melting vessel 14. In further examples, motor 22 can power raw material delivery device 20 to introduce raw materials 24 at a controlled rate based on a level of molten glass sensed downstream from melting vessel 14. Raw materials 24 within melting vessel 14 can thereafter be heated to form molten glass 28.

[0021] Glass manufacturing apparatus 10 can also optionally include a downstream glass manufacturing apparatus 30 positioned downstream relative to glass melting furnace 12. In some examples, a portion of downstream glass manufacturing apparatus 30 may be incorporated as part of glass melting furnace 12. In some instances, first connecting conduit 32 discussed below, or other portions of the downstream glass manufacturing apparatus 30, may be incorporated as part of glass melting furnace 12. Elements of the downstream glass manufacturing apparatus, including first connecting conduit 32, may be formed from a precious metal. Suitable precious metals include platinum group metals selected from the group of metals consisting of platinum, iridium, rhodium, osmium, ruthenium and palladium, or alloys thereof. For example, downstream components of the glass manufacturing apparatus may be formed from a platinum-rhodium alloy including from about 70 to about 90% by weight platinum and about 10% to about 30% by weight rhodium. However, other suitable metals can include molybdenum, palladium, rhenium, tantalum, titanium, tungsten and alloys thereof.

[0022] Downstream glass manufacturing apparatus 30 can include a first conditioning (i.e., processing) vessel, such as fining vessel 34, located downstream from melting vessel 14 and coupled to melting vessel 14 by way of the above-referenced first connecting conduit 32. In some examples, molten glass 28 may be gravity fed from melting vessel 14 to fining vessel 34 by way of first connecting conduit 32. For instance, gravity may cause molten glass 28 to pass through an interior pathway of first connecting conduit 32 from melting vessel 14 to fining vessel 34. It should be understood, however, that other conditioning vessels may be positioned downstream of melting vessel 14, for example between melting vessel 14 and fining vessel 34. In some embodiments, a conditioning vessel may be employed between the melting vessel and the fining vessel wherein molten glass from a primary melting vessel is further heated to continue the melting process, or cooled to a temperature lower than the temperature of the molten glass in the melting vessel before entering the fining vessel.

[0023] Bubbles may be removed from molten glass 28 within fining vessel 34 by various techniques. For example, raw materials 24 may include multivalent compounds (i.e. fining agents) such as tin oxide that, when heated, undergo a chemical reduction reaction and release oxygen. Other suitable fining agents include without limitation arsenic, antimony, iron and cerium. Fining vessel 34 is heated to a temperature greater than the melting vessel temperature, thereby heating the molten glass and the fining agent. Oxygen bubbles produced by the temperature-induced chemical reduction of the fining agent(s) rise through the molten glass within the fining vessel, wherein gases in the molten glass produced in the melting furnace can diffuse or coalesce into the oxygen bubbles produced by the fining agent. The enlarged gas bubbles can then rise to a free surface of the molten glass in the fining vessel and thereafter be vented out of the fining vessel. The oxygen bubbles can further induce mechanical mixing of the molten glass in the fining vessel.

[0024] Downstream glass manufacturing apparatus 30 can further include another conditioning vessel such as a mixing vessel 36 for mixing the molten glass. Mixing vessel 36 may be located downstream from the fining vessel 34. Mixing vessel 36 can be used to provide a homogenous glass melt composition, thereby reducing cords of chemical or thermal inhomogeneity that may otherwise exist within the fined molten glass exiting the fining vessel. As shown, fining vessel 34 may be coupled to mixing vessel 36 by way of a second connecting conduit 38. In some examples, molten glass 28 may be gravity fed from the fining vessel 34 to mixing vessel 36 by way of second connecting conduit 38. For instance, gravity may cause molten glass 28 to pass through an interior pathway of second connecting conduit 38 from fining vessel 34 to mixing vessel 36. It should be noted that while mixing vessel 36 is shown downstream of fining vessel 34, mixing vessel 36 may be positioned upstream from fining vessel 34. In some embodiments, downstream glass manufacturing apparatus 30 may include multiple mixing vessels, for example a mixing vessel upstream from fining vessel 34 and a mixing vessel downstream from fining vessel 34. These multiple mixing vessels may be of the same design, or they may be of different designs.

[0025] Downstream glass manufacturing apparatus 30 can further include another conditioning vessel such as delivery vessel 40 that may be located downstream from mixing vessel 36. Delivery vessel 40 may condition molten glass 28 to be fed into a downstream forming device. For instance, delivery vessel 40 can act as an accumulator and/or flow controller to adjust and/or provide a consistent flow of molten glass 28 to forming body 42 by way of exit conduit 44. As shown, mixing vessel 36 may be coupled to delivery vessel 40 by way of third connecting conduit 46. In some examples, molten glass 28 may be gravity fed from mixing vessel 36 to delivery vessel 40 by way of third connecting conduit 46. For instance, gravity may drive molten glass 28 through an interior pathway of third connecting conduit 46 from mixing vessel 36 to delivery vessel 40.

[0026] Downstream glass manufacturing apparatus 30 can further include forming apparatus 48 comprising the above-referenced forming body 42 and inlet conduit 50. Exit conduit 44 can be positioned to deliver molten glass 28 from delivery vessel 40 to inlet conduit 50 of forming apparatus 48. For example in examples, exit conduit 44 may be nested within and spaced apart from an inner surface of inlet conduit 50, thereby providing a free surface of molten glass positioned between the outer surface of exit conduit 44 and the inner surface of inlet conduit 50. Forming body 42 in a fusion down draw glass making apparatus can comprise a trough 52 positioned in an upper surface of the forming body and converging forming surfaces 54 that converge in a draw direction along a bottom edge 56 of the forming body. Molten glass delivered to the forming body trough via delivery vessel 40, exit conduit 44 and inlet conduit 50 overflows side walls of the trough and descends along the converging forming surfaces 54 as separate flows of molten glass. The separate flows of molten glass join below and along bottom edge 56 to produce a single ribbon of glass 58 that is drawn in a draw direction 60 from bottom edge 56 by applying tension to the glass ribbon, such as by gravity, edge rolls 72 and pulling rolls 82, to control the dimensions of the glass ribbon as the glass cools and a viscosity of the glass increases. Accordingly, glass ribbon 58 goes through a visco-elastic transition and acquires mechanical properties that give the glass ribbon 58 stable dimensional characteristics. Glass ribbon 58 may, in some embodiments, be separated into individual glass sheets 62 by a glass separation apparatus 100 in an elastic region of the glass ribbon. A robot 64 may then transfer the individual glass sheets 62 to a conveyor system using gripping tool 65, whereupon the individual glass sheets may be further processed.

[0027] FIGS. 2 and 3 illustrate, respectively, schematic front and side views of an example liquid metal system 150 for controlling the viscosity of glass melt flowing through an inlet conduit 50 of a forming apparatus 48. In the embodiment illustrated in FIG. 2, a liquid metal, such as liquid tin, flows through a heat transfer conduit 156 in the direction indicated by the arrows in FIGS. 2 and 3. Specifically, heat transfer conduit 156, including container 154, is heated to a temperature of at least about 300°C, such as at least about 350°C, and further such as at least about 400°C, including from about 300°C to about 1500°C by at least one of first heat exchanger 162, second heat exchanger 164, and third heat exchanger 168.

[0028] For example, when tin is used as the liquid metal, heat transfer conduit 156, including container 154, is heated such that the temperature of the tin inside container 154 exceeds its melting point of 232°C, such that the tin reaches a temperature of at least about 250°C, such as at least about 300°C, and further such as at least about 350°C, and yet further such as a temperature of at least about 400°C, and still yet further such as a temperature of at least about 450°C, and even still yet further such as a temperature of at least about 500°C, including from about 250°C to about 1400°C, such as from about 750°C to about 1350°C, and further such as from about 1100°C to about 1300°C. Container 154 may contain at least one stirrer, which can impart greater temperature uniformity of the liquid metal as well as improve its circulation.

[0029] The liquid metal, such as liquid tin, is circulated through heat transfer conduit 156, by, for example, being gravity fed from container 154 to segment 158 of heat transfer conduit 156 that is configured to extend around at least a portion of the glass melt flowing through inlet conduit 50. In the embodiment illustrated in FIGS. 2 and 3, segment 158 of heat transfer conduit 156 extends through a thermally conductive material 160 in a helical configuration, wherein the thermally conductive material 160 is configured to circumferentially surround glass melt flowing through inlet conduit 50. In particular, in the embodiment illustrated in FIGS. 2 and 3, segment 158 of heat transfer conduit 156 is configured to circumferentially surround a substantially horizontal portion of inlet conduit 50 that is in immediate fluid communication with forming body 42. While FIGS. 2 and 3 illustrate heat transfer conduit 156 extending around glass melt in a helical configuration, it is to be understood that embodiments disclosed herein may include other configurations wherein heat transfer conduit 156 is configured to extend around at least a portion of the glass melt.

[0030] Thermally conductive material 160, while not limited, can comprise a material that is chemically and mechanically stable at temperatures above at least about 1000°C, such as above at least about 1100°C, and further such as above at least about 1200°C, and still yet further such as above at least about 1300°C, such as temperatures within the range of about 1000°C to about 1500°C, while still maintaining thermally conductive properties that will enable stable and relatively uniform heat transfer between glass melt and heat transfer conduit 156. Exemplary, thermally conductive materials may include a highly conductive alumina material, such as AD995 alumina (99.5% AI2O₃) available from CoorsTek.

Thermally conductive material may be optionally surrounded by at least one thermally insulative material (not shown) that is chemically and mechanically stable at elevated temperatures.

[0031] In certain exemplary embodiments, heat transfer conduit 156 comprises at least one material selected from the group consisting of platinum and molybdenum. In certain exemplary embodiments, heat transfer conduit 156 comprises molybdenum. For example, heat transfer conduit 156 may consist essentially of molybdenum. Heat transfer conduit 156 may also be coated with an oxidation resistant material, such as SIBOR^® (Si-10B-2C) oxidation resistant coating available from Plansee SE. [0032] Liquid metal can be circulated through heat transfer conduit 156 through operation of pump 166. In certain exemplary embodiments pump 166 is an electromagnetic pump. When an electromagnetic pump is used and tin is used as the liquid metal, it is desirable for the liquid tin flowing through pump 166 to be at a temperature below 861 °C, such as below about 850°C, including between about 250°C and about 850°C. In operation of

electromagnetic pump, a magnetic field is set at right angles to the direction of liquid metal flow and a current is passed through it. This causes an electromagnetic force that moves the liquid metal.

[0033] In certain exemplary embodiments, the maximum temperature of the liquid metal, such as tin, flowing through the heat transfer conduit ranges from about 1100°C to about 1300°C, such as from about 1130°C to about 1270°C, and further such as from about 1170°C to about 1230°C. For example, the temperature of the liquid metal flowing through segment 158 of heat transfer conduit 156 that extends around at least a portion of the glass melt flowing through inlet conduit 50 may range from about 1100°C to about 1300°C, such as from about 1130°C to about 1270°C, and further such as from about 1170°C to about 1230°C. In such embodiments, when an electromagnetic pump is used, liquid metal may be cooled to a temperature below 861°C, such as a temperature below about 850°C, by at least one of first heat exchanger 162 and second heat exchanger 164 prior to liquid metal entering pump 166. After exiting pump 166, liquid metal may be heated to a temperature above about 1100°C, such as a temperature of from about 1100°C to about 1300°C by third heat exchanger 168.

[0034] Pump 166 may also be a mechanical pump. For example, mechanical pump may comprise refractory components, such as components selected from platinum, molybdenum, and refractory ceramic components, such as the ceramic pump for continuous liquid tin pumping available from Georgia Institute of Technology Atomistic Simulation and Energy Research Group. A potential advantage of using a mechanical pump is that such pump may be operable at high temperatures, such as temperatures up to at least about 1350°C, enabling lower energy requirements for heating and cooling liquid metal, such lower amounts of heating and cooling by at least one of first, second, and third heat exchangers 162, 164, and 168.

[0035] The temperature of the liquid metal flowing through heat transfer conduit 156 can be monitored by using at least one temperature measuring device, such as a thermocouple, along the flow pathway of the liquid metal, such as a thermocouple at or near container 154, segment 158, pump 166, and at least one of first, second, and third heat exchangers 162, 164, and 168. The temperature of the glass melt can also be monitored by using at least one temperature measuring device, such as a thermocouple, along the flow pathway of glass melt, such as a thermocouple at or near the entrance and/ or exit of inlet conduit 50.

[0036] A control scheme, including, for example, a control algorithm, can use the measured temperatures of the liquid metal and glass melt to, for example, control the temperature and/or flow rate of the liquid metal in order to control the temperature and viscosity of the glass melt flowing through the glass processing conduit, such as inlet conduit 50. The control scheme can take into account factors such as the temperature of the liquid metal, the temperature of the glass melt, the flow rate of the liquid metal, the flow rate of the glass melt, as well as heat transfer characteristics that are a function of the design and materials of the system.

[0037] For example, if it is desired to decrease the viscosity of glass melt flowing through the glass processing conduit, liquid metal flowing through segment 158 can flow at a higher temperature than the temperature of glass melt, such that heat is transferred from the liquid metal to the glass melt. For example, the temperature of the liquid metal flowing through segment 158 may be at least about 20°C, such as at least about 30°C, and further such as at least about 40°C, and yet further such as at least about 50°C, including from about 20°C to about 200°C higher than the temperature of the glass melt flowing into the glass processing conduit, such as inlet conduit 50.

[0038] For example, in certain exemplary embodiments, the temperature of the glass melt flowing into the glass processing conduit, such as inlet conduit 50, may range from about 1175°C to about 1275°C, such as from about 1200°C to about 1250°C, while the temperature of the liquid metal flowing through the glass processing conduit, such as segment 158, may be at least 50°C higher than the temperature of the glass melt flowing into the glass processing conduit, such that the temperature of the glass melt flowing out of the glass processing conduit is at least 20°C higher than the temperature of the glass melt flowing into the glass processing conduit.

[0039] Conversely, if it is desired to increase the viscosity of glass melt flowing through the glass processing conduit, liquid metal flowing through segment 158 can flow at a lower temperature than the temperature of glass melt, such that heat is transferred from the glass melt to the liquid metal. For example, the temperature of the liquid metal flowing through segment 158 may be at least about 20°C, such as at least about 30°C, and further such as at least about 40°C, and yet further such as at least about 50°C, including from about 20°C to about 200°C lower than the temperature of the glass melt flowing into the glass processing conduit, such as inlet conduit 50.

[0040] For example, in certain exemplary embodiments, the temperature of the glass melt flowing into the glass processing conduit, such as inlet conduit 50, may range from about 1175°C to about 1275°C, such as from about 1200°C to about 1250°C, while the temperature of the liquid metal flowing through the glass processing conduit, such as segment 158, may be at least 50°C lower than the temperature of the glass melt flowing into the glass processing conduit, such that the temperature of the glass melt flowing out of the glass processing conduit is at least 20°C lower than the temperature of the glass melt flowing into the glass processing conduit.

[0041] Embodiments disclosed herein can enable controlling the temperature of a glass melt in a glass processing conduit, such as an inlet conduit of a forming apparatus, to within about 1°C of a predetermined set point in order to control the viscosity of the glass melt flowing through the glass processing conduit to be within a predetermined range. In addition, embodiments disclosed herein can enable controlling the temperature of a glass melt in a glass processing conduit in response to a change of, for example, at least one of the composition of the glass melt, the flow rate of the glass melt, and the predetermined set point. Such embodiments can enable the production of high quality glass articles, such as glass sheets, under a variety of processing conditions without as frequent of a need to replace or repair glass processing system components.

[0042] For example, the predetermined set point for the temperature and/or viscosity of the glass melt flowing out of an inlet conduit of a forming apparatus may change during a production campaign due to, for example, changes in the geometry of a forming body. For example, during a production campaign, a middle region of a forming body may experience at least some degree of sag, which can result in a change in the relative mass flow of molten glass over the ends of the glass forming body relative to the mass flow of molten glass over the middle. Such effects can be counteracted by changing the viscosity of the molten glass flowing out of an inlet conduit of a forming apparatus according to embodiments disclosed herein, which can, in turn, change the relative mass flow of molten glass over the ends of the glass forming body relative to the mass flow of molten glass over the middle to within a desirable range, thereby extending the useful life of the glass forming body.

[0043] While embodiments described and illustrated herein involving flowing a liquid metal, such as liquid tin, through a heat transfer conduit that extends around at least a portion of the glass melt flowing thorough inlet conduit 50, such embodiments can also apply to other conduits in a glass manufacturing apparatus, such as, for example, first connecting conduit 32, second connecting conduit 38, and third connecting conduit 46.

[0044] Moreover, while the above embodiments have been described with reference to a fusion down draw process, it is to be understood that such embodiments are also applicable to other glass forming processes, such as float processes, slot draw processes, up-draw processes, and press-rolling processes.

[0045] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiment of the present disclosure without departing from the spirit and scope of the disclosure. Thus it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A method for controlling a viscosity of a glass melt flowing through a glass processing conduit, the method comprising:

flowing a liquid metal through a heat transfer conduit that extends around at least a portion of the glass melt flowing through the glass processing conduit; and controlling a temperature and flow rate of the liquid metal flowing through the heat transfer conduit relative to a temperature and flow rate of the glass melt flowing through the glass processing conduit in order to control the viscosity of the glass melt flowing through the glass processing conduit to be within a predetermined range.

2. The method of claim 1 , wherein the glass processing conduit is an inlet conduit of a glass forming apparatus.

3. The method of claim 1 , wherein the liquid metal comprises tin.

4. The method of claim 1 , wherein the heat transfer conduit comprises

molybdenum.

5. The method of claim 1 , wherein the heat transfer conduit is coated with an oxidation resistant material.

6. The method of claim 1 , wherein the liquid metal is pumped through the heat transfer conduit through operation of an electromagnetic pump.

7. The method of claim 1 , wherein the liquid metal is pumped through the heat transfer conduit through operation of a mechanical pump.

8. The method of claim 6, wherein the temperature of the liquid metal is

decreased prior to flowing through the electromagnetic pump and increased subsequent to flowing through the electromagnetic pump.

9. The method of claim 3, wherein a maximum temperature of the liquid metal flowing through the heat transfer conduit ranges from about 1100°C to about 1300°C.

10. The method of claim 1 , wherein the heat transfer conduit is heated to at least about 300°C prior to flowing the liquid metal through the heat transfer conduit.

1 1. The method of claim 1 , wherein the temperature of the liquid metal flowing through the heat transfer conduit is lower than the temperature of the glass melt flowing through the glass processing conduit.

12. The method of claim 1 , wherein the temperature of the liquid metal flowing through the heat transfer conduit is higher than the temperature of the glass melt flowing through the glass processing conduit.

13. An apparatus for controlling a viscosity of a glass melt flowing through a glass processing conduit, the apparatus comprising:

a heat transfer conduit extending around at least a portion of a glass processing

conduit;

wherein the apparatus is configured to control a temperature and flow rate of a liquid metal flowing through the heat transfer conduit relative to a temperature and flow rate of the glass melt flowing through the glass processing conduit in order to control the viscosity of the glass melt flowing through the glass processing conduit to be within a predetermined range.

14. The apparatus of claim 13, wherein the glass processing conduit is an inlet conduit of a glass forming apparatus.

15. The apparatus of claim 13, wherein the liquid metal comprises tin.

16. The apparatus of claim 13, wherein the heat transfer conduit comprises

molybdenum.

17. The apparatus of claim 13, wherein the heat transfer conduit is coated with an oxidation resistant material.

18. The apparatus of claim 13, wherein the apparatus comprises an

electromagnetic pump configured to pump the liquid metal through the heat transfer conduit.

19. The apparatus of claim 13, wherein the apparatus comprises a mechanical pump configured to pump the liquid metal through the heat transfer conduit.

20. A glass article made by the method of claim 1.

21. An electronic device comprising the glass article of claim 20.