Certain embodiments of the present invention relate to freezer and oven stacks in a food processing system for freezing or heating food product. More particularly, certain embodiments of the present invention relate to enhancing airflow through a freezer or oven stack to improve the quality of the heated or frozen food product and to improve throughput and efficiency of the food processing system.
Industrial food processing systems exist to both cook (i.e., heat) and freeze (i.e., cool) various types of food products before packaging and shipping the food products to distributors. In large-scale industrial applications, it is desirable to process (i.e., heat or cool) large quantities of food product in a short period of time while trying to maintain a high quality, uniformity, and yield of the food product.
During operation, the fan 30 pulls air into the heat exchanger 20 and through the coil 25 which may be cooled or heated. As a result, the air passing over the coil 25 is cooled or heated and passes out of the heat exchanger 20 and into one end of the stack 40. The heated or cooled air passes through the multiple tiers of the conveyer belt within the stack 40 and out the other end of the stack 40 and towards the fan 30. As a result, the food product within the stack 40 is heated or cooled (e.g., cooked or frozen).
The circulation fan 30 is responsible to circulate the air within the system 10 through the heat exchanger 20 and the stack 40. However, as the air comes out of the fan 30 and passes through the heat exchanger 20, the air loses velocity. Also, as the air is pulled through the stack 40, it further loses velocity. The loss in velocity of air through the system 10 can contribute to reduced efficiencies in heating or cooling the food product within the stack 40 and result in poor quality control of the food product. For example, the air flowing through the stack 40 may become non-uniform creating hot spots and cool spots within the stack 40.
Other food processing systems and methods are described below in the following patents.
Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.
An embodiment of the present invention provides a system to enhance airflow through a vertically oriented spiral freezer or oven stack. The system comprises a vertically oriented spiral stack assembly and at least one high-static fan assembly mounted above the spiral stack assembly to accelerate and direct air vertically through the spiral stack assembly.
An embodiment of the present invention provides a method to enhance airflow through a vertically oriented spiral freezer or oven stack. The method comprises directing air through a heat exchanger via at least one circulation fan, cooling or heating the air via a heat exchanger, and vertically accelerating the cooled or heated air through a vertically oriented spiral stack assembly via at least one high-static fan assembly mounted above the spiral stack assembly.
An embodiment of the present invention provides a method to retrofit a system having a vertically oriented spiral freezer or oven stack to enhance airflow through the stack. The method comprises mounting at least one high-static fan assembly above a vertically oriented spiral stack assembly to force air downward through the stack assembly, mounting at least one control panel in proximity to the system, electrically connecting the at least one control panel to the at least one high-static fan assembly to operationally control the at least one high-static fan assembly, installing a baffle approximately mid-way up the spiral stack assembly to help pressurize an upper side of the spiral stack assembly, and lining the baffle with a gasket to reduce an amount of air by-passing the spiral stack assembly.
These and other advantages and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings.
In accordance with an embodiment of the present invention, the circulation fan or blower 120 may be mounted to an input of the heat exchanger 110. Alternatively, the circulation fan or blower 120 may be mounted to infrastructure just outside an input of the heat exchanger 110. In accordance with an embodiment of the present invention, the at least one high-static fan assembly 140 may be mounted to the vertically oriented spiral stack assembly 130. Alternatively, the at least one high-static fan assembly 140 may be mounted to infrastructure above the stack assembly 130. The at least one control panel 150 may be mounted, for example, to a wall of the system 100.
During operation, the circulation fan 120 pulls air (as indicated by the arrows in
However, the high-static fan assembly 140 boosts the velocity of the air as the air exits the heat exchanger 110 and approaches the input to the stack 130. As a result, the airflow through the stack 130 is accelerated through the stack 130 by the high-static fan assembly 140 resulting in a more uniform, higher velocity, and higher volume airflow moving vertically through the stack 130 from top to bottom. Such an increased airflow results in improved efficiencies in heating or cooling the food product within the stack 130 and results in improved quality control of the food product. By using a high-static fan assembly, the air velocity is not changed dramatically when product load is varied as, for example, when surges in product load occur.
The heated or cooled air passes through the multiple tiers of the conveyer belt within the stack 130 and out the bottom end of the stack 130 and towards the circulation fan 120 to complete the cycle of airflow. As a result, the food product within the stack 130 is heated or cooled (e.g., cooked or frozen).
For example, referring to
For example, referring to the system 100 of
A detailed embodiment of a food processing freezer system with enhanced airflow is described below. The food processing system includes a self-stacking belt averaging 1000 feet when installed and has 22 tiers of retention for food product. The system includes two 30-horse power circulation fans each having the capacity to produce 24,000 cubic feet per minute (CFM) of air or a total of 48,000 CFM at a velocity of 2900 feet per minute (FPM) at the inlet port to a heat exchanger. The air is directed through a coil mounted directly above the discharge of both fans within the heat exchanger. The air pressurizes the bottom side of the coil and is distributed through the coil for heat exchange to take place.
The coil has a 3-panel lid at the top or exit side of the heat exchanger and covers the entire exit area. The lid rises when the fans are energized, creating a backpressure to distribute the air across the coil face at a predetermined velocity. The air leaves the heat exchanger area being directed by the 3-panel lid towards the stack. The velocity of the air, due to an increase in area and resistance created by the stack, would drop to an average velocity of 290 FPM if not for the high-static fan assemblies mounted above the stack. This velocity establishes the rate at which heat is displaced from the food product on the belt. The rate of displacement of heat establishes a dwell time for each product, which varies from incoming and exiting temperatures relating to product specifications.
Seven high-static fan assemblies are mounted above the stack. Each high-static fan assembly is able to develop a volume of air of 10,500 CFM at a velocity of 3000 FPM. The blower housing and framing of each high-static fan assembly are 304 stainless steel with aluminum-extruded blades. A control panel, having variable speed drives, is able to power several high static fan assemblies. The support system for the blower housing and framing is also 304 stainless steel. The system is designed for each high-static fan assembly to pivot from the run position to the clean position for cleaning purposes via the support system. The seven high-static fan assemblies are placed over the stack and cover 305 degrees of the stack's circumference. The blower dimensions are 27.75 inches in diameter with an 11-inch housing assembly. These dimensions will change as a function of the width of the belt. Each high-static fan assembly includes 3-horse power, 3-phase 460 volt motors rated at 1725 revolutions per minute (RPM).
Seven high-static fan assemblies are mounted above the stack. Each high-static fan assembly is able to develop a volume of air of 10,500 CFM at a velocity of 3000 FPM. The blower housing and framing of each high-static fan assembly are 304 stainless steel with aluminum extruded blades. A control panel, having variable speed drives, is able to power several high-static fan assemblies. The support system for the blower housing and framing is also 304 stainless steel. The system is designed for each high-static fan assembly to pivot from the run position to the clean position for cleaning purposes via the support system. The seven high-static fan assemblies are placed over the stack and cover a predetermined portion of the stack's circumference, such as 305 degrees of the stack's circumference in this embodiment. The particular amount of coverage will depend on factors such as overall stack size, the type of products to be processed, the belt loading characteristics, the fan characteristics and other aspects of a particular system. In this embodiment, the blower dimensions are 27.75 inches in diameter with an 11 inch housing assembly. These dimensions may change as a function of the width of the belt. Each high-static fan assembly may be configured using 3 horse power, 3-phase 460 volt motors rated at 1725 revolutions per minute (RPM), but again other configurations are contemplated to provide the desired operational characteristics.
When energized, the air-enhanced system grabs air from the exit of the heat exchanger and boosts the air through the product zone within the stack. The increase in air volume is possible due to the decrease in static resistance within the product zone and the pressurization to the inlet port of the high-static fan assemblies. The high-static fan assemblies essentially feed each other to create a vortex of air that assists in maintaining the airflow. This is critical in extracting heat from the product. The system includes AC drives that allow a user to control and balance the air to varying products. The system is designed to improve the airflow through the stack, taking the air of a conventional system at 290 FPM to a level of 1500 FPM with the seven high-static fan assemblies. The increase of airflow substantially reduces freezing time, allowing a user to speed up the product conveyer belt. By increasing the belt speed, the separation between product pieces also increases and allows the system to maintain the desired airflow while adding more product to the process. The increase is a minimum of 15% more product when the speed of the product belt is increased by 20%.
Ideally, the high-static fan assembly design is to span as much of the belt width and circumference as possible while containing the air in the product area for maximum extraction potential. By using a high-static blade, the air velocity is not changed as dramatically by varying product load or surges which occur during most processes. The variable drives are used to balance the air within the product zone which improves the extraction process throughout the process.
Also, by increasing the volume of air throughout the process, the enhanced system will improve performance of the coil in the heat exchanger. With increased product separation on the belt and with higher velocities established through the coil, ice and snow crystals are blown out and do not built up on the coil as fast. This equates to longer run periods between defrosting of the coil.
The enhanced system may also increase the yield of certain products. For example, the faster a meat or poultry product is frozen, the smaller the ice crystals that are produced within the muscle of the product. The more crystals retained in a given piece of product, the more weight is retained. In the event that a product is being produced at a temperature that has it displacing moisture before entering the freezer, the addition of a higher velocity airflow at a cold temperature will stop the displacement of moisture more quickly. The product will also crust over faster trapping the moisture inside of the product.
In summary, a system and method are disclosed for enhancing airflow through a vertically oriented spiral freezer or oven stack used for freezing or heating food product. At least one high-static fan assembly is mounted above a spiral stack assembly of the system to accelerate and direct air vertically through the spiral stack assembly. Air is directed through a heat exchanger via at least one circulation fan, cooling or heating the air via the heat exchanger. The cooled or heated air is vertically accelerated through the vertically oriented spiral stack assembly via at least one high-static fan assembly mounted above the spiral stack assembly. A method is also disclosed to retrofit a system having a vertically oriented spiral freezer or oven stack to enhance airflow through the stack.
While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
A. 35 U.S.C. §119(e) This application claims the benefit of U.S. Provisional Application No. APPLICATION NO. FILING DATE 60/527,910 Dec. 8, 2003.
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Number | Date | Country | |
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20050138953 A1 | Jun 2005 | US |
Number | Date | Country | |
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60527910 | Dec 2003 | US |