Patent Application
20050287280
The present invention relates generally to scraped surface heat exchangers. More particularly, the present invention relates to a method and apparatus for heating product tubes in scraped surface heat exchanger assemblies.
Scraped-surface heat exchangers are commonly utilized in aseptic processing of foodstuffs. These heat exchangers are preferred because of their capability to process heat-sensitive, viscous products, and minimize the extent of burn-on, or fouling on the heat transfer surface. Such heat exchangers are commonly marketed under the trade names, for example, Votator®, Thermutator®, Contherm®, and Terlotherm®. Waukesha Cherry-Burrell, Delavan, Wis., for example, manufactures such heat exchangers.
Scraped surface heat exchangers are particularly suitable for use in the foodstuff industry where they are used for heat treating products such as jellies, jams, peanut butter, sauces and puddings. A heat exchanger of this type may include a cylindrical treatment chamber or product tube and a rotor, also referred to as a mutator shaft, arranged in the chamber. A number of blade rows including a number of successively arranged blade scrapers may also be mounted on the rotor so as to make the blades scrape the inner surface of the chamber or product tube during operation.
The product for receiving heat treatment is generally introduced, in some embodiments, under pressure at one end of the heat exchanger and is generally designed to leave the heat exchanger at its opposite end. The product may generally be designed to flow between an outer surface of the mutator shaft and an inner surface of the product tube as it traverses a length of the scraped surface heat exchanger assembly. In a general design of the scraped surface heat exchanger assembly, the inside of a product tube is preferably scraped with blades mounted on the rotor or mutator shaft which rotates within the product tube. Additionally, the product tubes, along with the mutator shafts, may be manufactured with different lengths to provide various heat exchange areas. Furthermore, these scraped surface heat exchanger assemblies can be installed and operated in either a horizontal or vertical position.
In the heated foodstuff industry, scraped surface heat exchanger assemblies have been typically configured such that a heating medium, e.g., hot water or steam, to provide heat exchange to the product tube in order to heat a treated product. In some embodiments, the heating medium may be generally circulated on the outside of the treatment chamber or product tube in order to provide the heat exchange. Thus, a treatment chamber or product tube is typically heated so that a treated product will undergo a change of temperature as it passes through the scraped surface heat exchanger. The scraping of the product off the inner surface of the chamber during its passage through the heat exchanger, e.g., via the successively arranged blade scrapers mounted on the rotor can, thereby provide a considerably improved heat transmission.
Scraped surface heat exchanger assemblies utilizing heating mediums are typically retrofitted with media connections and additional equipment for performing numerous operations. Such equipment may include piping equipment for delivering the medium to the scraped surface heat exchanger, transferring heat to the product tube, means for transporting the medium away from the scraped surface heat exchanger, boiler equipment for reheating the medium, and additional piping equipment for returning the reheated medium back to the scraped surface heat exchanger for subsequent heating/heat transfer operations.
While the aforementioned designed can provide a certain level of heat transfer to treated products within scraped surface heat exchanger assemblies, numerous difficulties can be attributed to the use thereof. For example, the retrofitted equipment such as the piping equipment utilized to deliver the medium to, from and across the product tube, the boiler plant to reheat the medium, and additional piping equipment to return the reheated medium back to the scraped surface heat exchanger can be expensive to built, operate and maintain. Additionally, due to a possibility for crushing an external surface of the product tube as a result of the media operating under high temporal and pressure constraints, e.g., 250 psi, a heavy walled media jacket is generally required in order to meet ASME code/pressure requirements. Furthermore, the equipment set-up of the aforementioned design typically requires a product tube conducive to high heat transfer efficiency rates in preferred embodiments in order to provide sufficient heat transfer to a treated product. Such product tubes may preferably comprise materials including, for example, Nickel which can provide good heat transfer capabilities and strong corrosive resistant properties. However, a drawback to using product tubes comprising Nickel may include its fairly high expense.
Accordingly, it is desirable to provide a method and apparatus for heating products in a scraped surface heat exchanger that is cost effective, for instance, by reducing requirements for equipment set-up, maintenance, and operating costs. It is further desirable to provide a method and apparatus for heating products in a scraped surface heat exchanger which reduces a possibility for external crushing pressures on the product tube while providing sufficient, and in some cases, improved heat transfer to the product tube for heat treating products.
The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect a method and apparatus is provided that in some embodiments heats products in a scraped surface heat exchanger by induction heating.
In accordance with one aspect of the present invention, a scraped surface heat exchanger assembly is provided that, in some embodiments, includes a product tube, a mutator shaft, an induction blanket, a product feed inlet and a product return outlet.
In accordance with another aspect of the present invention, a method of heating products in a scraped surface heat exchanger assembly is provided, that in some embodiments, includes providing a product tube and assembling a mutator shaft within the inner surface of the product tube. The method may further include feeding a product through the product tube and heating the product via an induction blanket disposed around a longitudinal length of the product tube.
In accordance with yet another aspect of the present invention, a system for heating products in a scraped surface heat exchanger assembly is provided that in some embodiments, includes a means for containing a product, a means for rotating a product, a means for providing heat via induction, and a means for feeding a product.
There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
An embodiment in accordance with the present invention provides a method and apparatus for providing induction heating to a product tube of the type preferably utilized within scraped surface heat exchanger assembly. Preferred embodiments of the invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout.
An embodiment of the present inventive method and apparatus is illustrated in
A plurality of scraper blade mounting pins 16 are preferably located on an outer surface 18 of the mutator shaft 10. The scraper blade mounting pins 16 are preferably welded to the outer surface 18 of the mutator shaft 10. In a preferred design, the scraper blade mounting pins 16 hold and retain inserted scraper blades 19 as provided, for example, by slots 17 shown in
A design of the scraped surface heat exchanger assembly 20 may provide a means for receiving a product for heat treatment processing and further provide additional means for feeding the treated product from the scraped surface heat exchanger assembly 20. In one embodiment, the means for receiving and feeding the product may include a first product connection 30 and a second product connection 32 coupled to the scraped surface heat exchanger assembly 20. The first product connection 30 and the second product connection 32 will provide the means by which the product is delivered to and received from the scraped surface heat exchanger assembly 20.
Each product connection 30, 32 is preferably sealed in relation to the product tube 26 to facilitate an aseptic processing environment. Such sealing may be accomplished using a shaft seal rings 33 which can be inserted, for example, ends 35, 36 of the mutator shaft 10. Materials for the shaft seal rings 33 may include elastomers designed for use in sanitary conditions. Such elastomers may included, for example, floral elastomers such as Viton® manufactured by Dupont. Alternatively the sealing rings may comprise other composite materials such as EPDM. Such materials are conducive to providing a sanitary working environment particularly suitable for use in the foodstuff industry.
In accordance with a preferred embodiment of the invention, an induction heating system comprising an induction heating blanket 34 is substantially wrapped around a longitudinal length of the product tube 26. A main function of the induction heating system includes providing transferred heat to the product tube 26 for heating the product therein. The aforementioned induction heating system essentially replaces the mediajacket and any associated media connections and/or additional equipment including, for example, boiler equipment as sometimes utilized in the prior art. The result of which can provide significant advantages over other industrial heating systems known in the prior art such as those utilizing a media jacket set-up.
A preferred embodiment of the induction heating system further comprises a power source 40, such as an AC power supply, and a plurality of induction heating coils 36. The design of the present invention utilizes the power supply 40 to send alternating current through the plurality of induction heating coils 36 to thereby generate a magnetic field around the product tube 26. Thus, eddy currents are induced within the product tube 26 to generate relatively precise amounts of clean, localized heat.
A protective cover 38 may enclose the induction blanket 34 to serve a variety of purposes including, for examples, sealing the induction blanket 34, providing an aesthetically pleasing finish as an exterior surface of the scraped surface heat exchanger assembly 20, and providing additional protection to the product tube 26. Preferred use of materials for constructing the protective cover 38 include acrylic or plastic.
Advantages of using an induction heating system to heat a scraped surface heat exchanger assembly 20, as described herein, include an ability to generate consistent heating patterns for a given set-up. This may include operating through a series of multiple sequential heating cycles and performing on a daily basis. Hence, the reliability of the scraped surface heat exchanger assembly 20 and the ability to generate a quality treated product may increase and/or become more dependable.
The induction heating system is also capable of developing heat more directly and instantly (>2000° F. in <1 second) inside the product tube 26 which may further allow for quicker startup times for performing heat treatment operations than other industrial heating systems (such as equipment set-ups utilizing media jackets and associated equipment). Since heating process times can be dramatically reduced by the induction heating system of the present invention can be integrated directly into the production line, and production throughput can also be significantly increased.
The properties of the induction heating design may also lend itself to more controlled and directional heating. The aforementioned is further supported by the fact that the power input may be precisely controlled to achieve a precise temperature required for slow or fast heating. The flexibility of utilizing the induction heating system, as described herein, is further indicative of the fact that the induction coils may be located a distance away from the power supply. Hence, usage of the induction heating system in combination with the scraped surface heat exchanger assembly 20 of the present invention may provide greater alternatives to shop-floor set-ups and arrangements of scraped surface heat exchanger assemblies 20.
A further and inherent advantage of induction heating includes the benefits of providing a clean, non-polluting process. Induction heating generally produces no harmful emissions, exhaust gases, smoke, loud noise or waste heat to alter the surrounding environment. Thus, working conditions may be improved with the absence of smoke, fumes, noise and extraneous heat produced by furnaces or other industrial heating systems. Furthermore, the induction heating provided by the induction blanket 34 can be regarded as an energy-efficient process which can, in some instances, convert up to 90% of the energy expended into useful heat to reduce utility costs. Additionally, stand-by losses are reduced to a minimum because the heat is only “on” when actually performing its intended task.
Because of good and, in some cases, improved heat transfer properties provided by the induction blanket 34 design of the present invention may, a concern for the heat transfer capabilities of the product tube 26 can be reduced as would otherwise be required using a media jacket, for example. An inherent property of the induction heating design includes inducing heat directly into the product tube 26 itself. Hence, significant cost reduction may be realized by constructing the product tube 26 of less expensive materials which do not need to characterized as good heat transfer capabilities previously utilized in the prior art such as Nickel. Alternatively, materials such as stainless steel, may be utilized in the induction heating design of the present invention—a material of which is significantly less expensive yet suitable for constructing product tubes 26 of the present design. Additionally, since the induction heating design eliminates outside heating mediums under pressure, a concern for crushing the product tube 26 under such pressure is also eliminated. Thus, the product tube 26, may be made thinner to reduce additional costs in its construction thereof. Other cost benefits of the induction heating design may include eliminating additional sealings and fittings otherwise required in a design, for example, retrofitted with media connections and additional equipment for heating and delivering the media.
The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
