Single pass continous freezer

Abstract

A system for rapid and efficient cooling and freezing of a product. The system reduces, preferably to one, the number of passes that coolant flow makes over a product before returning to a refrigeration system. In one example, the system includes an enclosed environment including an inlet, an outlet. The system also includes a conveyor system disposed within the enclosed environment and including a conveyor path extending between the inlet and the outlet, the conveyor path defining a helical travel path for the product. The system further includes a refrigeration system configured to generate a cooling airflow that flows from a ducting inlet to a ducting outlet. Additionally, the enclosed environment has a monotonic negative pressure gradient from the ducting inlet to the ducting outlet.

Description

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 63 / 455,123, filed Mar. 28, 2023. The contents of which is hereby incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] The present disclosure generally relates to a cooling environment, and more particularly, to a system for freezing products in a cooling environment.BACKGROUND

[0003] Many products are transported or stored below ambient temperatures. This is generally accomplished by immersing the product in cooled air produced by heat exchange with a compressor-driven refrigeration circuit. Product storage and transport often entail logistical constraints such as access to electrical power, mechanical limitations, and the like. In these situations, an auxiliary thermal mass that undergoes a phase change at a temperature below ambient, such as water ice, is separately frozen and stored with the product to keep it cool through conduction by contact and passive air convection.

[0004] Freezing materials is accomplished by their immersion in chilled air that circulates by passive or forced convection. Freezing products is typically limited by the pace of convective energy transfer with air as the medium, both at the product and at the interface between air and the refrigeration circuit. An object of the present invention is to maximize the rate at which heat is transferred from the product to the chilled air. A second object of the present invention is to reduce the size, weight, and power of a continuous freezer for maximum yield of frozen product per time interval. A third object of the present invention is to maximize the energy efficiency of a continuous freezer system.SUMMARY

[0005] Disclosed herein is a system for cooling a product including an enclosed environment having an inlet, an outlet, a first portion, and a second portion disposed opposite the first portion. Additionally, the system includes a conveyor system disposed within the enclosed environment and including a conveyor path extending between the inlet and the outlet, the conveyor path defining a helical travel path for the product. The system also includes a refrigeration system configured to generate a cooling airflow that flows from a ducting inlet arranged at or immediately proximate the first portion to a ducting outlet arranged at or immediately proximate the second portion. The system may also have a monotonic negative pressure gradient from the first portion to the second portion and the cooling airflow may be configured to cool the product before the product exits the enclosed environment via the outlet.

[0006] In some variations, the monotonic negative pressure gradient is defined by a first pressure proximate to the ducting inlet, a second pressure proximate to the ducting outlet, and a monotonic, approximately linear pressure transition from the first pressure to the second pressure. Additionally or alternatively, the helical travel path defines a constant pitch and / or a constant radius.

[0007] In other variations, the first portion is a top portion of the enclosed environment and the second portion is a bottom portion of the enclosed environment. Alternatively, the first portion can be a first sidewall of the enclosed environment and the second portion can be a second sidewall of the enclosed environment. In either variation, the inlet may be disposed proximately to the first portion and the outlet may be disposed proximately to the second portion. Additionally, the first portion may be a first sidewall of the enclosed environment and the second portion may be a second sidewall of the enclosed environment.

[0008] In other variations, the ducting outlet includes a grate disposed in the second portion of the enclosed environment. Additionally, the enclosed environment is a first enclosed environment, the system further comprising a second enclosed environment, wherein the second enclosed environment in fluid communication with the ducting outlet, the refrigeration system, and the ducting inlet. In some such examples, the refrigeration system pulls cooling airflow from the ducting outlet, cools, the cooling airflow, and passes the cooling airflow through the ducting inlet.

[0009] Also disclosed herein is a system for cooling a product. The system includes an enclosed environment including an inlet, an outlet, a first portion, and a second portion disposed opposite the first portion. The system further includes a conveyor system disposed within the enclosed environment and including a conveyor path extending between the inlet and the outlet, the conveyor path defining a helical travel path for the product. Also, the system includes an insert disposed in a central aperture of the helical travel path, such that the insert creates a monotonic negative pressure gradient from the first portion to the second portion. The system is configured to cool the product before the product exits the enclosed environment via the outlet.

[0010] In some variations, the insert comprises a top surface, a bottom surface, and an outer surface extending between the top surface and the bottom surface, wherein the outer surface is an angled surface. The insert may have cylindrical, conical, or helical symmetry. The insert may have a first diameter at the top surface and a second diameter at the bottom surface, the second diameter being larger than the first diameter. Additionally, the insert may include a fin disposed on at least a portion of an outer surface of the insert between the top surface and the bottom surface.

[0011] In other variations the pressure decreases monotonically from the first portion, over the product, through the second portion to the outlet, resulting in a single pass of cold air from the evaporator, through the first region, over the product, through the second region, and to the outlet where it is returned to the evaporator. In other words, the pressure gradient is negative along streamlines to facilitate a single pass through the first region, over the product, and out of the second region, whence it returns to the evaporator.

[0012] In yet other variations, the first portion is a top portion of the enclosed environment and the second portion is a bottom portion of the enclosed environment. Also the conveyor path has a first height and the insert has a second height larger than the first height.

[0013] Also disclosed herein is system for cooling a product. The system includes an enclosed environment including an inlet, an outlet, a first portion, and a second portion disposed opposite the first portion. Additionally, the system includes a conveyor system disposed within the enclosed environment and including a conveyor path extending between the inlet and the outlet, the conveyor path defining a helical travel path for the product. The system may also include a refrigeration system configured to generate a cooling airflow that flows from a ducting inlet arranged at or immediately proximate the first portion to a ducting outlet arranged at or immediately proximate the second portion. Furthermore, the system includes an insert disposed in a central aperture of the helical travel path, such that the insert creates a uniformly negative pressure gradient (ensuring there is only a single pass of cooling airflow over a product) from the first portion to the second portion. The cooling airflow may be configured to cool the product before the product exits the enclosed environment via the outlet.

[0014] In some variations, the uniformly negative pressure gradient is defined by a first pressure disposed proximately to the ducting inlet, a second pressure proximately to the ducting outlet, and a monotonic or approximately linear pressure transition from the first pressure to the second pressure. The uniformly negative pressure gradient may be a first uniformly negative pressure gradient in an annular passage of the enclosed environment and the insert may create a second uniformly negative pressure gradient in the central aperture from the first portion to the second portion, the second monotonic negative pressure gradient different from the first monotonic negative pressure gradient.

[0015] In other variations, the pressure gradient between the first and second portions over the product is uniformly negative to ensure a single pass of evaporator-cooled air of the product.

[0016] In yet other variations, the insert comprises a frustrum with a top surface, a bottom surface, and an outer surface extending between the top surface and the bottom surface, wherein the outer surface is an angled surface. Additionally, the insert may have a first diameter at the top surface and a second diameter at the bottom surface, the second diameter being larger than the first diameter. Additionally, the insert may include a fin disposed along at least a portion of the outer surface. Additionally, the insert may have curvature while retaining cylindrical or helical symmetry to facilitate optimal pressure gradient distributions over the various turns of the helical conveyor.

[0017] Furthermore, some variations include a system in which the first portion is a top portion of the enclosed environment and the second portion is a bottom portion of the enclosed environment.

[0018] Also disclosed herein is a method of cooling a product. The method may include simulating, using computational flow dynamics, a cooling cycle for the product, the cooling cycle comprises passing a cooling airflow through a conveyor system disposed within an enclosed environment, the conveyor system including a conveyor path extending between an inlet and an outlet of the enclosed environment, and the conveyor path defining a helical travel path for the product. The method may also include determining a flow profile of the cooling airflow during the cooling cycle, and based on the determined flow profile, modifying the conveyor system for the product to minimize recirculation of the cooling airflow back over the helical travel path. The method also includes performing the cooling cycle using the modified conveyor system.

[0019] In some variations, modifying the conveyor system for the product comprises modifying a radius and / or pitch angle of one or more spirals of the helical travel path. Additionally, modifying the conveyor system for the product can include modifying the insert disposed in the central aperture of the helical travel path. Further, determining the flow profile can include evaluating pressure gradients in the enclosed environment, and wherein modifying the conveyor system includes modifying a first pressure gradient in an annular passage outside the helical travel path and a second pressure gradient in a central aperture of the helical travel path.

[0020] Also disclosed herein is a method of cooling a product. The method can include simulating, using computational flow dynamics, a cooling cycle for the product, the cooling cycle comprises passing a cooling airflow through a conveyor system disposed within an enclosed environment, the conveyor system including a conveyor path extending between an inlet and an outlet of the enclosed environment, the conveyor path defining a helical travel path for the product, and an insert having an outer surface disposed in a central aperture of the helical travel path. The method may also include determining a flow profile of the cooling airflow during the cooling cycle. Additionally, based on the determined flow profile, the method includes modifying the conveyor system for the product to minimize recirculation of the cooling airflow back over the helical travel path and, performing the cooling cycle using the modified conveyor system.

[0021] In some variations, modifying the conveyor system for the product includes modifying a pitch angle, which entails changes to the spacing between one or more spirals of the helical travel path. Additionally, modifying the conveyor system for the product can include disposing a radially symmetric, conical, or helical insert in a central aperture of the helical travel path.

[0022] In other variations, determining the flow profile may include evaluating pressure gradients within the enclosed environment, and modifying the conveyor system includes modifying a first pressure gradient in an annular passage outside the helical travel path and a second pressure gradient around the insert in the central aperture. The method may also include minimizing recirculation of the refrigerated airflow by evaluating pressure gradients of the enclosed environment to determine the shape of the outer surface such that the refrigerated airflow passes over the helical travel path only once (avoiding recirculation of the airflow). The method may also include determining the shape of the outer surface of the insert relative to a longitudinal axis of the insert.

[0023] Also disclosed herein is a system for rapidly cooling a product. The system includes a conveyer system that transports product at a first temperature through a region with flowing air at a second temperature, the second temperature lower than the first temperature. The system also includes a refrigeration system that cools the flowing air to the second temperature and a blower situated between the refrigeration system and the product that circulates the flowing air over the product. Additionally, the blower, conveyer, and refrigeration system may be aligned to reduce the number of sequential convective heat transfer contacts between a portion of the flowing air and the product as it proceeds from the refrigeration system to the product and back to the refrigeration system.

[0024] In some variations, the conveyer system has a helical geometry defining a pitch adjusted to be greater than about 2 and fewer than about 5 boundary layer thicknesses based on the velocity, density, viscosity, and density of the flowing air. Fewer than two boundary layer thicknesses impedes heat transfer through contact with the product, and more than about five boundary layer thicknesses permits cold air to flow through the conveyer without contacting the product or otherwise facilitating heat transfer. This permits optimization of the size of the helical conveyer and overall system. The conveyor system may further include a thermally insulating or chilled surface that provides lateral acceleration of the flowing air directed down along a longitudinal axis of the conveyor system to obviate stagnation at the floor and to radially orient the flowing air.

[0025] Also disclosed herein is a method of rapidly cooling a product. The method includes assessing a flow trajectory of air through a conveyor system from a refrigeration system to a product and back to the refrigeration system using computational fluid dynamics. The method further includes adjusting a flow boundary layer thickness and conveyer geometry to reduce the number of convective heat transfer events between the air and the product that occur before the air is returned to the refrigeration system. Additionally, the method may include adjusting the pitch of the helix and / or the flow conditions to ensure that there is only one boundary layer to be at least one boundary layer but not more than approximately 2 boundary layers, 3 boundary layers, 4 boundary layers, 5 boundary layers, etc.

[0026] In some variations, the method also includes assessing the flow trajectory of air redirected by an insert disposed within the conveyor system.BRIEF DESCRIPTION OF DRAWINGS

[0027] The present disclosure is described in the following detailed description in conjunction with the drawings, wherein:

[0028] FIG. 1 illustrates a schematic diagram of a refrigeration system configured for use in the cooling systems of the present application.

[0029] FIG. 2 illustrates a side view of a convective heat transfer system.

[0030] FIG. 3 illustrates a graph of temperature change of a product over time as a function of the convective heat transfer coefficient.

[0031] FIG. 4 illustrates a graph of freezing times of a product for different heat transfer coefficients.

[0032] FIG. 5 is a side view of a flow system corresponding to cooling three products in accordance with prior art as described in the present disclosure.

[0033] FIG. 6 illustrates a graph of cooling dynamics of the products of FIG. 5 for air heat transfer.

[0034] FIG. 7 is a partial view of a conventional helical cooling system.

[0035] FIG. 8 is a perspective view of a second conventional helical cooling system.

[0036] FIG. 9 is a perspective view of the second conventional helical cooling system of FIG. 8.

[0037] FIG. 10 is a side view of the second conventional helical cooling system of FIG. 8.

[0038] FIG. 11 is a top view of the second conventional helical cooling system of FIG. 8.

[0039] FIG. 12 is a side view of example velocity flow data in the second conventional helical cooling system of FIG. 8.

[0040] FIG. 13 a perspective view of the second conventional helical cooling system of FIG. 8 including a plurality of recirculating streamlines.

[0041] FIG. 14 is a side view of an example system for cooling a product in accordance with the present disclosure.

[0042] FIG. 15 is a side view of an insert configured for use in the system of FIG. 14.

[0043] FIG. 16 is a perspective view of a second example system for cooling a product in accordance with the present disclosure.

[0044] FIG. 17 is a perspective view of a third example system for cooling a product in accordance with the present disclosure.

[0045] FIG. 18 is a perspective view of the third example system of FIG. 17 including example cooling air airflow lines.

[0046] FIG. 19 is a side view of the third example system for cooling a product including an example pressure gradient.

[0047] FIG. 20 is a side view of the third example system for cooling a product illustrating example flow streams with the length of the arrows proportional to the common logarithm of the velocity magnitude and the gray scale indicating static pressure in micropascals.

[0048] FIG. 21 is a flowchart illustrating an example method for cooling a product in accordance with the present disclosure.

[0049] FIG. 22 is a flowchart illustrating an example method for simulating a cooling cycle to virtually configure an insert in accordance with the present disclosure.

[0050] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and / or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments. It will further be appreciated that certain actions and / or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.DETAILED DESCRIPTIONDefinitions

[0051] The term convective heat transfer coefficient, as used herein, is the rate of heat transfer between a solid surface and a fluid per unit surface area per unit temperature difference. In symbolic form,h=qΔ⁢T,where h is the heat transfer coefficient in Watts / meter2Kelvin (W / m2K), q is the local heat flux density (W / m2), and ΔT is the temperature difference in Kelvin (K) between the solid and the fluid.The term conductive heat transfer, as used herein, is the flow of heat between two static materials that are in intimate thermal contact, as occurs between two solids or a solid and a liquid or gel that is not immobile.

[0053] The term radiative heat transfer, as used herein, is the flow of heat between two objects by electromagnetic radiation and moderated by wavelength-dependent differential emissivities.

[0054] The term target product, as used herein, is a finite sample of material to be cooled or frozen that is optionally encased in a thermally thin metal or polymer film.

[0055] The term refrigerant, as used herein, is a fluid that cools by evaporation and is subsequently condensed by compression.

[0056] The term coolant, as used herein, is a liquid that transports heat without changing to a gas or solid phase.Commercially Freezing Products

[0057] Freezing products in bulk may be time consuming and costly. For example, freezing a large quantity of products in bulk may take days and even weeks to completely freeze. Additionally, large quantities of product may be bulky and heavy, which increases overall costs. In order to cool such large quantities of product, helical cooling systems can be utilized to provide a consistent process for adequately cooling each product.Example Refrigeration System

[0058] FIG. 1 illustrates the operation of an example refrigeration system 100 for use in the example single pass refrigerators disclosed herein (described in greater detail in connection with FIGS. 7-20). The refrigeration system 100 includes an evaporator 102 and a condenser 104. A refrigerant is passed in a closed fluid system between the evaporator 102 and the condenser 104. The refrigerant changes phase to a vapor within the evaporator 102, absorbing thermal energy from the air (i.e., cooling the air). The refrigerant passes as a vapor along conduit 112 to the condenser 104. Within the condenser 104, the refrigerant changes phase to a liquid and is returned to the evaporator 102 along conduit 114. The conversion of vapor to liquid refrigerant uses compression and subsequent Joule-Thompson expansion. In various examples, the refrigeration system 100 may further include a pump (not shown) to convey the refrigerant through the refrigeration system 100.

[0059] Warm air 132 passes over the evaporator 102 and is cooled down. The cooled down air 134 is passed over an example conveyor system 142 conveying several products 144. As the cooled down air 132 passes over the products 144, the air is warmed up to be warm air 136. In some examples, warm air 136 returns to the evaporator 102 to be cooled again.Convective Cooling

[0060] FIGS. 2 and 3 illustrate an example convection heat transfer system 202 and a graph 302 of representative convection temperature change data. Convection based freezers pass air around the product. As shown in FIG. 2, airflow 204 passes around a product 206. The rate of heat flow between the product 206 and the airflow 204 is governed by convective, rather than conductive heat transfer (discussed in greater detail below). As is well recognized by those practiced in the art of thermal engineering, convective heat transfer depends on the physical properties of the fluid, the solid, and the flow conditions. The ratio of convective heat transfer to temperature difference, also known as the convective heat transfer coefficient h, is not a property of the fluid alone. It is an experimentally determined parameter whose value depends on all the variables influencing convection including the surface geometry, the nature of fluid motion, the properties of the fluid, the temperature, and the bulk fluid velocity. The impact of these variables on the rate of convective heat transfer for specific conditions can be calculated precisely using finite-element computational software as described above.

[0061] Representative ranges for convective heat transfer coefficients are based on the range of achievable solid and fluid properties including thermal conductivity, heat capacity, viscosity, density, and accessible flow velocities and are summarized in Table 1. The convective heat transfer coefficient to or from gases range from about 2 to no more than approximately 300 W / m2K, while that for liquids ranges from about 50 to as much as 10,000 W / m2K.TABLE 1Heat Transfer CoefficientProcess(W / m2K)Free ConvectionGases2-20 Liquids50-1000Forced ConvectionGases25-300 Liquids 100-40,000Convection with PhaseBoiling / Condensation2,500-100,000Change

[0062] The time required to complete the conversion from ambient temperature to the target temperature of the frozen product is a fundamental, rate-limiting unit operation for a continuous freezer. Decreasing this time permits higher throughput for a fixed refrigerant architecture, or a more compact device for specific throughput requirements.Freeze Times for Convective Cooling

[0063] FIG. 4 illustrates graph 400 of time to freeze a product based on different values of the convective heat transfer coefficient (h). A cold room with its air temperature set to −20° F. will freeze a water packet by passive convection (k~30 W / m2K) in just under two hours, whereas forced convection at h=1000 W / m2K reduces this time to 14 minutes, approaching the asymptotic value for conductive cooling of 8 minutes as the convective heat transfer coefficient approaches infinity.

[0064] The time required to complete the conversion from ambient temperature to the target temperature of the frozen product is a fundamental, rate-limiting unit operation for a continuous freezer. Decreasing this time obviously permits higher throughput for a fixed refrigerant architecture, or a more compact device for specific throughput requirements. An aspect of the present invention is to reduce, and preferably minimize, this time by ensuring that airflow is directed from the cooling system to pass over the product only once (single pass) before it is returned to the refrigerant system, which is most commonly an evaporator coil.

[0065] FIG. 5 illustrates a refrigeration experiment 500. A first product 512, a second product 514, and a third product 516 are in a cooling airflow 522. The first, second, and third products 512, 514, 516 are identical polyethylene bladders filled with water and disposed in the environment at an initial temperature of 75 degrees Fahrenheit (° F.). The cooling airflow 522, initially at 35° F., flows over the first, second, and third products 512, 514, 516, sequentially at an average velocity of 10 cm / s. Finite element conjugate heat transfer rates are evaluated using standard computational fluid dynamics methods. After the cooling airflow 522 passes over the first product 512, the first product 512 is cooled and the cooling airflow 522 is warmed. The warmed cooling airflow 522 subsequently cools the second product 514, but not as quickly as the first product 512. The second product 514 cools more slowly because the temperature difference between the warmed cooling airflow 522 and the second product 514 is less than the difference between the cooling airflow 522 and the first product 512. As a result, the first product 512 cools faster than the second product 514 and the third product 516. Similarly, the second product 514 cools faster than the third product 516.

[0066] FIG. 6 illustrates a graph 600 corresponding to cooling data 602 measured in the testing experiment 500. The cooling data 602 includes a first data line 612 (corresponding to the first product 512), a second data line 614 (corresponding to the first product 514), a third data line 616 (corresponding to the first product 516). As shown in the graph 600, the first product 512 cools faster than the second product 514 and the third product. For example, the first product cools from 75° F. to approximately 38° F. in the same time it takes the second product to cool from 75° F. to approximately 42° F. and the third product to cool from 75° F. to approximately 46° F.Prior Art Helical Cooling Systems

[0067] FIG. 7 illustrates one example of a known helical cooling system 700. The helical cooling system 700 includes a conveyor system 702, a refrigeration system 704, and an enclosed environment 706. As shown in FIG. 7, the refrigeration system 704 is disposed above the conveyor system 702, however in various other examples, the refrigeration system 704 could be disposed below the conveyor system 702 or on a side of the conveyor system 702.

[0068] The conveyor system 702 includes a helical travel path 712. The helical travel path 712 includes a plurality of successive levels 714a, 714b, 714c, . . . , 714n. The helical travel path 712 further defines a pitch angle 716 and a helical radius 718. In the illustrated example of FIG. 7, the pitch angle 716 and the helical radius are constant along a height 722 of the conveyor system 702. As a result, the height 724 between successive levels (e.g., between levels 714b and 714c) of the conveyor system 702 is constant. Additionally, the helical radius 718 is constant for each level 714a, 714b, 714c, . . . , 714n. As a result, each successive level 714a, 714b, 714c, . . . , 714n is directly above or below every other layer.

[0069] The conveyor system 702 is disposed in the enclosed environment 706. As illustrated in FIG. 7, the enclosed environment 706 includes four sidewalls 732a, 732b (the other two sidewalls not shown), a bottom wall 734, and a top wall (not shown). The conveyor system 702 includes a conveyor path extending from an inlet 736a to an outlet 736b. As shown, the outlet 736b passes through the sidewall 732a and the inlet 736a passes through a sidewall opposite the sidewall 732a (not shown). The inlet 736a is disposed proximately to the bottom wall 734, while the outlet 736b is disposed proximately to the top wall (not shown). In the illustrated example, the conveyor system 702 and the enclosed environment 706 share the longitudinal axis 740.

[0070] The refrigeration system 704 generates a cooling airflow 752 that is directed into the enclosed environment 706. The cooling airflow 752 passes over and through the conveyor system 702 to cool product being conveyed along the conveyor system. The cooling airflow 752 can recirculate off the sidewalls 732a, 732b and the bottom wall 734. Although the refrigeration system 704 directs the cooling airflow 752 into the enclosed environment 706 horizontally, in various examples, the refrigeration system 704 could directed the cooling airflow 752 at any angle and still cause recirculation off the sidewalls 732a, 732b, and the bottom wall 734.

[0071] In the known helical cooling system 700, when the cooling airflow 752 passes through the conveyor system 702 conveying products to be cooled, the cooling airflow 752 absorbs thermal energy from the products and the cooling airflow 752 is warmed. The warmed cooling airflow 754a, 754b then stagnates against the sidewalls and floor, then recirculates back over the product(s) on the conveyor system 702. For example, after the cooling airflow passes over a first product, the first product is partially cooled and the cooling airflow is partially warmed, but then the (warmer and recirculated) cooling airflow 754a, 754b passes over a second product, and the warmer cooling airflow 754a, 754b will be less effective at cooling the second product. This is because the heat transfer rate from the product to the cooling airflow 752 is directly proportional to the temperature difference between the product and the cooling airflow 752.

[0072] FIGS. 8, 9, 10, 11, 12, and 13 illustrate a second prior art helical cooling system 800 comprising an insulated enclosure 802, a spiral conveyor 804, and a blower 806 for producing a refrigerated airflow. In the illustrated example, the blower 806 directs air from evaporator coils (not shown) onto the spiral conveyer 804. A product is configured to enter the insulated enclosure 802 through entrance port 812. It is conveyed through the blast of cold air from the blower 806 as it traverses the spiral conveyor 804 and is thence conveyed to the exit port 814. The number of turns, the location of the entrance and exit ports and blower, and the position of the return to the coils can be varied based on the particular freezing requirements.

[0073] Referring to FIG. 9, streamlines show air emanating from the blower 806, traversing the helical conveyer at least twice and stagnating at the opposite wall before returning to the outlet. FIGS. 10 and 11 show the streamlines from side and top views, respectively.

[0074] FIG. 12 illustrates a velocity field 1202 corresponding to the blower 806 directing a cooling airflow into the insulated enclosure 802. As can be seen in FIG. 12, the velocity field 1202 is indicative of the cooling airflow passing through the spiral conveyor 804 and recirculating back onto the spiral conveyor 804.

[0075] Freezer geometries, such as are shown in FIGS. 7, 8, 9, 10, 11, 12, and 13, may be evaluated using computational fluid dynamics calculations to establish conditions under which convective or conjugate heat transfer occurs between the product and the flowing air. A typical result of these calculations (COMSOL Multiphysics version 6.1, COMSOL, Burlington, MA) shows the velocity magnitude in the y-z plane where x=0. The average velocity is 0.1 m / s, and the peak velocity of the cold air is 0.18 m / s in this exemplar calculation. Referring to FIGS. 9, 10, and 11, three streamlines for air emanating from the blower 806 are shown in the top view (FIG. 11), the side view (FIG. 10), and the orthographic view (FIG. 9). The streamlines that emanate from the blower 806 impinge directly on the spiral conveyor 804, with heat transfer occurring from warm product to cooler air. This warmed air subsequently traverses an inner region of the spiral conveyor 804 before impinging again on product, but this time since its temperature exceeds that of the air coming directly from the blower 806 it is less able to extract further heat from the posterior product. In other words, the heat transfer coefficient, which is determined in detail by the flow conditions surrounding the product, may not change but the temperature difference between the air and product is reduced after every contact with product.

[0076] FIG. 13 illustrates the second helical cooling system 800 including a plurality of recirculating streamlines 1302. The plurality of recirculating streamlines 1302 illustrate that all of the airflow provided by the blower 806 pass over the spiral conveyor 804 two or more times, at least in part because the cooling airflow recirculates and passes back over the spiral conveyor 804.Example Improved Helical Cooling Systems

[0077] The present disclosure is directed to cooling systems that provide rapid, on-demand solutions for cooling products. Generally speaking, the cooling systems as described herein receive a plurality of products in an unfrozen state and deliver the plurality of products in a refrigerated or frozen state. For simplicity, cooling systems may cool product to arbitrary temperatures including those that cause a phase change to the product.

[0078] In various examples of improved cooling systems described herein, the cooling system is configured to reduce air recirculation in the enclosed environment of the cooling system. By reducing recirculation, the cooling system maximizes the rate of heat transfer between the product and the chilled air. As a result, the overall system is more efficient than known cooling systems such as the known helical cooling system 700 discussed above. Thus, the cooling system is more energy efficient. The cooling systems of the present disclosure improves efficiency by limiting recirculation of the cooling airflow in the cooling system such that only the coldest air passes over the product. In some examples, the cooling system of the present invention has reduced size, weight, and / or power consumption.

[0079] In one example, the airflow from the evaporator coils flows directly down the center of the helical conveyer belt, but with an addition. If the center of the helix is unobstructed the cold air may stagnate on the floor and recirculate inside the helix, resulting in multiple convective heat transfer events with spiraling product. A nominally conical insulating body in the center of the helix provides controlled lateral deflection of the cooled air from within to without the helix in a single pass.

[0080] FIG. 14 illustrates a first example of an improved helical cooling system 1400 for cooling a product in accordance with the present disclosure. The system 1400 includes a conveyor system 1402, a refrigeration system 1404, and an enclosed environment 1406. Additionally, the system 1400 includes a ducting system 1407 and an insert 1408, though in other examples, the system 1400 need not include the ducting system 1407 or the insert 1408.

[0081] As shown in FIG. 14, the conveyor system 1402 is in the enclosed environment 1406 and includes a helical travel path 1412. The helical travel path 1412 includes a plurality of successive levels 1414a, 1414b, 1414c, . . . , 1414n. The helical travel path 1412 further defines a pitch angle 1416 and a helical radius 1418. In the illustrated example of FIG. 14, the pitch angle 1416 is constant along a height 1422 of the conveyor system 1402. As a result, the height 1424 between successive levels (e.g., between levels 1414b and 1414c) of the conveyor system 1402 is constant. Additionally, the helical radius 1418 is constant for each level 1414a, 1414b, 1414c, . . . , 1414n. As a result, each successive level 1414a, 1414b, 1414c, . . . , 1414n is directly above or below every other layer. In various other examples, the pitch angle 1416 and / or the helical radius 1418 may be larger or smaller than illustrated in FIG. 14. Additionally or alternatively, the pitch angle 1416 and / or the helical radius 1418 may be variable. In such examples, the height 1424 between successive layers 1414a, 1414b, 1414c, . . . , 1414n may vary (i.e., not be constant) and / or the successive layers 1414a, 1414b, 1414c, . . . , 1414n may not be disposed directly above and below every other layer in the manner illustrated in FIG. 14. The pitch of the successive layers needs to be at least twice the boundary layer thickness for the flow around the product, whether this is laminar or turbulent, to make efficient use of convective contact with the product.

[0082] The example conveyor system 1402 is in the enclosed environment 1406. As illustrated in FIG. 14, the enclosed environment 1406 in this example includes a cylindrical sidewall 1432, a bottom wall 1434, and a top wall 1436 opposite the bottom wall 1434. In various other examples, the sidewall may be rectangular, as described in connection with the enclosed environment 706 of FIG. 7, or have a different shape. In the illustrated example, the conveyor system 1402 includes a conveyor path extending from an inlet 1436a to an outlet 1436b. The inlet 1436a and the outlet 1436b pass through the sidewall 1432. In the illustrated example, the inlet 1436a is disposed proximately to the bottom wall 1434 and the outlet 1436b is disposed proximately to the top wall 1436, but in other examples, the location of the inlet 1436a and the outlet 1436b could be reversed and the outlet 1436b could instead be disposed proximately to the bottom wall 1434. In the illustrated example, the conveyor system 1402 is centrally disposed in the enclosed environment 1406, such that the conveyor system 1402 and the enclosed environment 1406 share the longitudinal axis 1440 (i.e., the conveyor system 1402 and the enclosed environment are co-axial with one another). However, in various other examples, the conveyor system 1402 may not be centrally disposed in the enclosed environment.

[0083] In the illustrated example of FIG. 14, the enclosed environment 1406 further includes a first portion 1442a at or near the top of the enclosed environment 1406 and a second portion 1442b at or near a bottom of the enclosed environment 1406, the first and second portions 1442a, 1442b disposed opposite each other. The ducting system 1407 is connected to the enclosed environment 1406 such that a ducting inlet 1444 of the ducting system 1407 is arranged at or immediately proximate the first portion 1442a and a ducting outlet 1446 of the ducting system 1407 is arranged at or immediately proximate the second portion 1442b. In other variations, the first portion 1442a and the second portion 1442b may instead be disposed in the sidewall 1432 of the enclosed environment 1406, in which case the ducting inlet 1444 and the ducting outlet 1446 can also be arranged in the sidewall 1432 of the enclosed environment 1406.

[0084] Each of the ducting inlet 1444 and the ducting outlet 1446 is in fluid communication with the enclosed environment 1406 and the refrigeration system 1404. The ducting inlet 1444, the enclosed environment 1406, the ducting outlet 1446, and the refrigeration system 1404 are in fluid communication with one another and together form a loop. The refrigeration system 1404 can be, for example, similar to or substantially identical to the refrigeration system described in connection with FIG. 1. In the example of FIG. 14, the refrigeration system 1404 generates a cooling airflow 1452 which passes through the ducting inlet 1444, into the enclosed environment 1406, and out through the ducting outlet 1446. The cooling airflow 1452, having been warmed (1456) by a single pass over the product then passes through the ducting outlet 1446 back to the refrigeration system 1404. In other words, the enclosed environment 1406 will have a first pressure at the ducting inlet 1444 and a second, lower pressure at the ducting outlet 1446, such that the enclosed environment 1406 has or defines a monotonic negative pressure gradient from the ducting inlet 1444 to the ducting outlet 1446. In some alternative examples, the cooling airflow 1452 could be reversed such that the enclosed environment 1406 has a pressure gradient that causes cooling airflow 1452 to flow from the second portion 1442b to the first portion 1442a. In various examples, the ducting inlet, ducting outlet, and / or refrigeration system may include a fan or other apparatus to generate the pressure gradient (e.g., pump the cooling airflow 1452)

[0085] The inventors of the present disclosure have unexpectedly discovered that the inclusion of the insert 1408 in the system 1404 improves the efficiency of the cooling system 1400. More particularly, the inventors have unexpectedly discovered that disposing the insert 1408 in the conveyor system 1402 and the enclosed environment 1406 improves the efficiency of the cooling system 1400 by altering the negative pressure gradient so that the gradient is more uniform and so that the cooling airflow 1452 passes from the central aperture 1464a to an annular passage 1464b circumscribing the conveyor system 1402 while passing from the first portion 1442a to the second portion 1442b. In the illustrated example of FIG. 14, the insert 1408 is disposed in the conveyor system and the enclosed environment 1406 such that the insert 1408 is also centrally located about the central longitudinal axis 1440 (i.e., the insert 1408 is coaxial with the conveyor system 1402 and the enclosed environment 1406). To this end, at least in this example, the insert 1408 is disposed in a central aperture 1464a of the conveyor system 1402. In other examples, the enclosed environment 1406, the conveyor system 1402, and / or the insert 1408 may not be coaxial. In any event, due to the highly efficient airflow movement of the cooling airflow 1452 through the enclosed environment 1406 and through the conveyor system 1402, the cooling airflow 1452 is configured to cool a product traveling on the conveyor path in the time it takes the product to travel from the inlet 1436a to the outlet 1436b. In various examples, cooling a product could include reducing the temperature of the product until the product is frozen, semi-frozen, or cooled to a desired temperature.

[0086] As illustrated in FIG. 15, the insert 1408 includes a top surface 1512, a bottom surface 1514, and an outer surface 1516 disposed between the top surface 1512 and the bottom surface 1514. In this example, the outer surface 1516 extends, in a straight line, between the top surface 1512 and the bottom surface 1514, but in other examples, the outer surface 1516 can be curved and / or include angled surfaces to control airflow. In preferred examples, the insert 1408 is made from an insulated material, such as, for example, a closed-cell polyurethane foam.

[0087] In the present example, the top surface 1512 and the bottom surface 1514 are both circular. In other examples, the top surface 1512 and the bottom surface 1514 may be a different regular or irregular shape (e.g., a square, triangle, hexagon, etc.). As illustrated, the top surface 1512 has a first diameter 1522 and the bottom surface 1514 has a second diameter 1524 that is larger than the first diameter 1522. The insert 1408 further has an insert height 1526 measured between the top surface 1512 and the bottom surface 1514. In preferred examples, the insert height 1526 is greater than the height 1422 of the conveyor system. The difference in diameter between the top surface 1512 and the bottom surface 1514 causes the outer surface 1516 to be oriented at an angle 1532 (taper angle) relative to a central longitudinal axis 1534. In the present example, the angle 1532 is an acute angle of approximately 10 degrees (°). In various other examples, the angle 1532 could be as little as 0° or as great as 45°.

[0088] As shown in FIG. 15, the insert 1408 is a right conical frustum (i.e., a truncated cone between parallel surfaces), but in some examples, the insert may be shaped more like a conical or other polygonal frustum. In such examples, the diameter 1522 of the top surface 1512 and / or the diameter of the bottom surface 1514 may be reduced to a point. Additionally or alternatively, the outer surface 1516 may have a concavely or convexly curved surface between the top surface 1512 and the bottom surface 1514. Alternative examples of the insert 1408 will be discussed in greater detail in connection with FIGS. 16 and 17.

[0089] When the insert 1408 is disposed in the central aperture 1464a of the conveyor system 1402 as illustrated in FIG. 14, the outer surface 1516 increases the pressure in the central aperture 1464a. The outer surface 1516 increases the pressure in the central aperture 1464a by reducing the cross-sectional area in the central aperture 1464a. Additionally, the insert 1408 uniformly (or substantially uniformly) deflects the cooling airflow 1452 out of the central aperture 1464a by directing the cooling airflow 1452 in the direction of the annular passage 1464b. In other examples, the insert 1408 could be differently shaped, but still reduce recirculation of the cooling airflow 1452 over the conveyor system 1402.

[0090] Additionally, in some examples, the insert may be actively cooled and configured to further reduce the temperature of the cooling airflow before it encounters a product.

[0091] FIG. 16 illustrates a second example of a system 1600 for cooling a product in accordance with the present disclosure. The system 1600 is substantially identical to the cooling system 1400. For example, similar to the cooling system 1400, the cooling system 1600 includes a conveyor system 1602, a refrigeration system 1604, and an enclosed environment 1606 (shown as transparent in FIG. 16). In the present example, the insert 1608 is similar to the insert 1408, but includes a fin 1609, helically wrapped around the insert 1608.

[0092] The example fin 1609 directs cooling airflow across the conveyor system 1602. In the illustrated example, the fin 1609 is disposed at the same height as the conveyor system 1602 radially adjacent to the fin 1609. In other examples, the fin 1609 could be elevated above the conveyor system 1602 radially adjacent to the fin 1609. As used herein, the portion of the conveyor system 1602 radially adjacent to the fin 1609 is the portion of the conveyor system 1602 closest to a given portion of the fin 1609.

[0093] In various examples, the fin 1609 could be disposed on the insert 1608 in any manner to direct a cooling airflow over the conveyor system 1602. For example, the fin 1609 could include a series of segmented fins. In such example, each of the segmented fins could be horizontal, instead of helically angled downwards. If the segmented fins are horizontal, there is less risk the cooling airflow would circulate circumferentially around the insert 1608 and the conveyor system 1602.

[0094] Furthermore, the fin 1609 could be angled relative to the insert 1608. For example, the fin 1609 could be angled towards the conveyor 1602. Further, the radial width of the fin 1609 could be different than shown in FIG. 16. In some examples, the radial width of the fin 1609 could be variable along the length of the fin 1609 (e.g., wider in some areas and narrower in others).

[0095] The enclosed environment 1606 additionally includes a bottom grate 1612. The cooling airflow generated by the refrigeration system 1604 flows through the bottom grate 1612. In some examples, the system 1600 includes ducting (not shown) to recirculate the cooling airflow from the bottom grate back to the refrigeration system 1604. In the various examples, the cooling system 1400 (discussed above) and / or the cooling system 1700 (discussed below) could also include similar bottom grate 1612 to recirculate cooling airflow to the refrigeration system. In various examples, the bottom grate 1612 could be coupled to an air pumping system that creates a low pressure zone along the bottom grate 1612 and further pulls the cooling airflow through the grate and back to the refrigeration system 1604. Additionally, the refrigeration system 1604 could include a blower to push cooling airflow into the enclosed environment 1606.

[0096] FIGS. 17, 18, 19, and 20 illustrate a second example of a system 1700 for cooling a product in accordance with the present disclosure. The system 1700 is substantially identical to the cooling system 1400 and the cooling system 1600. For example, similar to the cooling system 1400, the cooling system 1700 includes a conveyor system 1702, a refrigeration system 1704, and an enclosed environment 1706 (shown as transparent in FIGS. 17 and 18). In the present example, the insert 1708 is similar to the insert 1408, but is conical.

[0097] In the present example, the insert 1708 is conical. As discussed above, the insert 1708 could be any of a variety of shapes. In the present example, the conical shape of the insert 1708 fills an inner space 1712 of the conveyor system and directs cooling airflow from the inner space 1712 to the annular space 1714. The shape and location of the insert serve to prevent stagnation and recirculation of air at the bottom of the interior of the helical conveyer. The conical shape of the insert 1708 is shown by way of example. The insert 1708 could be cylindrical, pyramidal, or a frustum (described in connection with FIGS. 14-15).

[0098] As shown in FIG. 18, the refrigeration system 1704 generates cooling airflow 1802 with streamlines starting at the refrigeration system 1704. The refrigeration system directs the cooling airflow 1802 downward (in some examples, via a blower (not shown)). To direct the cooling airflow 1802 downward, the refrigeration system 1704 could include a fan or blower (not shown). The insert 1708 redirects the cooling airflow 1802 outward from the inner space 1712 toward the annular space 1714 when the cooling airflow 1802 impinges on the insert 1708. In various examples, the shape of the insert 1708 can be adjusted to direct the flow through the conveyor system 1702.

[0099] FIG. 19 illustrates contours of static pressure in microPascals where the pressure is zero at the bottom of the figure. The pressure within the inner space 1712 is substantially higher than the annular space 1714 leading to a single pass of cooled air from the inlet over the product and out the exhaust on the bottom of the figure.

[0100] FIG. 20 further illustrates that a cooling airflow in the enclosed environment 1706 having the insert 1708 does not recirculate over the conveyor system 1702. The grayscale shows static pressure, which is substantially higher within the inner space 1712 than the annular space 1714 the helical conveyor. Arrows indicate local flow direction in the y=0 plane with their length proportional to the common logarithm of the velocity magnitude. In other words, flow is substantially faster within the helix than without. As can be seen in FIG. 20, the cooling airflow 2052 flows downwards into the inner space 1712, laterally from the inner space 1712 to the annular space 1714, and downward through the annular space 1714. As a result, the cooling airflow 2052 does not recirculate back from the annular space 1714 to the inner space 1712.

[0101] FIG. 21 illustrates an example of a method 2100 for cooling a product using, at least in part, a cooling system such as the cooling system 1400 of FIG. 14, the cooling system 1600 of FIG. 16, and / or the cooling system 1700 of FIGS. 17-20. While the method in this example is described as including steps performed once and in a particular order, in various other examples, the steps of the method 2100 can be reordered and / or performed multiple times.

[0102] In various examples, the method 2100 may be entirely or partially performed by a controller communicatively connected to the cooling system (e.g., cooling system 1400, 1600, 1700). The controller may include a microprocessor, a memory, and one or more wired and / or wireless communication links. The controller may be coupled to one or more components of the cooling system via one or more of the communication links. For example, the communication links may couple the controller to the refrigeration system of the cooling system and / or to motors disposed in the conveyor system. In some examples, the controller can be communicatively connected to at least one sensor disposed in or proximately to the enclosed environment via one or more of the communication links. For example, the sensor may be a temperature sense, airflow sensor, pressure sensor, optical sensor, etc. The controller can be configured to receive sensor data from each of the sensors, process the sensor data, and control the cooling system based on the sensor date. Accordingly, the controller can, for example, control the temperature in the enclosed environment and the speed at which product is moved along the conveyor system.

[0103] At step 2102 (shown in greater detail in connection with FIG. 22), the method 2100 includes simulating, using computational fluid dynamics, a cooling cycle for the product, the cooling cycle including passing a cooling airflow (e.g., cooling airflow 1452) through a conveyor system (e.g., conveyor system 1402) disposed within an enclosed environment (e.g., enclosed environment 1406), the conveyor system including a conveyor path extending between an inlet (e.g., inlet 1436a) and an outlet (e.g., outlet 1436b) of the enclosed environment (e.g., enclosed environment 1406), and the conveyor path defining a helical travel path for the product, the simulating will be performed using computational flow dynamics (CFD) software and generally involves analyzing thermodynamics, structural mechanics, and fluid mechanics in the cooling system. Further, the simulation may involve iterative designing and modifying the simulations to obtain an optimized system. In some examples, this simulation includes virtually generating variations of inserts and ducting systems.

[0104] At step 2104, the method 2100 includes determining a flow profile of the cooling airflow during the simulated cooling cycle. The flow profile may, for example, be identical or similar to the flow diagram shown in FIG. 21. Based on the flow profile, at step 2106 the method 2100 includes modifying the conveyor system to adjust the flow profile in order to minimize recirculation of the cooling airflow back over the helical travel path. Adjustments to the conveyor system include, but are not limited to, including an insert (e.g., the insert 1408), adjusting the shape, size, or placement of the insert, adjusting the ducting for the cooling airflow, adjusting a pitch angle and / or a radius of the conveyor system, adjusting the dimensions (e.g., the height) of the conveyor system, and adjusting flow parameters associated with the conveyor system (e.g., the rate at which the conveyor system moves, the duration of the cooling cycle).

[0105] For example, modifying the conveyor system can involve simulating the usage of an insert in the cooling system during the cooling cycle, adjusting the shape and size of the insert, and examining the effect the insert has on the cooling airflow during the subsequent cooling cycle. Adjusting the ducting can, for example, involve adjusting the size of the ducting inlet and / or the ducting outlet, and / or adjusting the location of the ducting inlet and the outlet in the enclosed environment. Also, adjusting the pitch angle of the conveyor system can include adjusting the space between successive layers of the conveyor system to maximize turbulent airflow over the produce and also adjust the time a product spends in the enclosed environment. Lastly, the dimensions of the conveyor system (e.g., cross sectional size of the conveyor system, length of the conveyor system, etc.) can be adjusted to improve cooling airflow movement in the enclosed environment.

[0106] At step 2108, the method 2100 includes evaluating the flow profile to determine if recirculation has been sufficiently minimized following the modification of the conveyor system. Preferably, the CFD software will simulate a cooling cycle performed using the modified conveyor system and then evaluate the flow profile accordingly. In some cases, the CFD software will iteratively perform this process. If evaluation of the flow profile shows that the airflow still has too much recirculation or is otherwise too inefficient, the method 2100 returns to step 2102 to simulate and modify the cooling cycle again. However, if the flow profile shows that the airflow has sufficiently reduced recirculation or is otherwise sufficiently efficient, the method 2100 proceeds to step 2110. At step 2110, the cooling cycle is performed, using the modified conveyor system. In some examples, the method 2100 may also include evaluating the flow profile of the airflow during the actually performed (i.e., non-simulated) cooling cycle to determine if the modifications to the conveyor system sufficiently minimized recirculation (or, if not, whether further modifications are necessary).

[0107] FIG. 22 illustrates an example of how the step 2102 of the method 2200 can be performed. In this example, the step 2102 includes a first sub-step 2202 of virtually generating the conveyor system as disposed in the enclosed environment. After generating the conveyor system and the enclosed environment, the step 2102 includes, optionally, virtually generating the insert (at sub-step 2204) and / or virtually generating the cooling airflow ducting (at sub-step 2206). The virtually generated insert may be disposed in a central aperture of the conveyor system. Sub-step 2204 may also include virtually generating a plurality of variations of the insert (e.g., differently sized and / or shaped inserts).

[0108] Lastly, at sub-step 2208, the step 2102 includes using the computational fluid flow dynamics software to simulate the cooling cycle in which the cooling airflow flows in the enclosed environment and around the conveyor system. In some examples, the simulation may identify regions of drastic pressure differentials or fluid eddies. Additionally, in some examples, the computational fluid dynamics software may analyze the transition of fluid flow between laminar flow and turbulent flow and the ability of a cooling airflow to cool a product. The information generated at step 2208 may then be used to determine the flow profile at step 2104.

[0109] Restriction of the cooling airflow to a single pass over the product before returning to the evaporator reduces the average temperature of the return air. As a result, the heat load on the refrigeration system is minimized resulting in lower energy use. Furthermore, optimization of the flow conditions including the single pass over product may reduce the blower requirements, which in typical prior-art systems use about one third of the freezer system energy.

[0110] Those skilled in the art will recognize that a wide variety of modifications, alterations, and combinations can be made with respect to the above described examples without departing from the spirit and scope of the invention(s) disclosed herein, and that such modifications, alterations, and combinations are to be viewed as being within the ambit of the inventive concept(s).

Examples

Embodiment Construction

Definitions

[0051]The term convective heat transfer coefficient, as used herein, is the rate of heat transfer between a solid surface and a fluid per unit surface area per unit temperature difference. In symbolic form,

h=qΔ⁢T,

where h is the heat transfer coefficient in Watts / meter2Kelvin (W / m2K), q is the local heat flux density (W / m2), and ΔT is the temperature difference in Kelvin (K) between the solid and the fluid.

The term conductive heat transfer, as used herein, is the flow of heat between two static materials that are in intimate thermal contact, as occurs between two solids or a solid and a liquid or gel that is not immobile.

[0053]The term radiative heat transfer, as used herein, is the flow of heat between two objects by electromagnetic radiation and moderated by wavelength-dependent differential emissivities.

[0054]The term target product, as used herein, is a finite sample of material to be cooled or frozen that is optionally encased in a thermally thin metal or polymer film...

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 63 / 455,123, filed Mar. 28, 2023. The contents of which is hereby incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] The present disclosure generally relates to a cooling environment, and more particularly, to a system for freezing products in a cooling environment.BACKGROUND

[0003] Many products are transported or stored below ambient temperatures. This is generally accomplished by immersing the product in cooled air produced by heat exchange with a compressor-driven refrigeration circuit. Product storage and transport often entail logistical constraints such as access to electrical power, mechanical limitations, and the like. In these situations, an auxiliary thermal mass that undergoes a phase change at a temperature below ambient, such as water ice, is separately frozen and stored with the product to keep it cool through conduction by contact and passive air convection.

[0004] Freezing materials is accomplished by their immersion in chilled air that circulates by passive or forced convection. Freezing products is typically limited by the pace of convective energy transfer with air as the medium, both at the product and at the interface between air and the refrigeration circuit. An object of the present invention is to maximize the rate at which heat is transferred from the product to the chilled air. A second object of the present invention is to reduce the size, weight, and power of a continuous freezer for maximum yield of frozen product per time interval. A third object of the present invention is to maximize the energy efficiency of a continuous freezer system.SUMMARY

[0005] Disclosed herein is a system for cooling a product including an enclosed environment having an inlet, an outlet, a first portion, and a second portion disposed opposite the first portion. Additionally, the system includes a conveyor system disposed within the enclosed environment and including a conveyor path extending between the inlet and the outlet, the conveyor path defining a helical travel path for the product. The system also includes a refrigeration system configured to generate a cooling airflow that flows from a ducting inlet arranged at or immediately proximate the first portion to a ducting outlet arranged at or immediately proximate the second portion. The system may also have a monotonic negative pressure gradient from the first portion to the second portion and the cooling airflow may be configured to cool the product before the product exits the enclosed environment via the outlet.

[0006] In some variations, the monotonic negative pressure gradient is defined by a first pressure proximate to the ducting inlet, a second pressure proximate to the ducting outlet, and a monotonic, approximately linear pressure transition from the first pressure to the second pressure. Additionally or alternatively, the helical travel path defines a constant pitch and / or a constant radius.

[0007] In other variations, the first portion is a top portion of the enclosed environment and the second portion is a bottom portion of the enclosed environment. Alternatively, the first portion can be a first sidewall of the enclosed environment and the second portion can be a second sidewall of the enclosed environment. In either variation, the inlet may be disposed proximately to the first portion and the outlet may be disposed proximately to the second portion. Additionally, the first portion may be a first sidewall of the enclosed environment and the second portion may be a second sidewall of the enclosed environment.

[0008] In other variations, the ducting outlet includes a grate disposed in the second portion of the enclosed environment. Additionally, the enclosed environment is a first enclosed environment, the system further comprising a second enclosed environment, wherein the second enclosed environment in fluid communication with the ducting outlet, the refrigeration system, and the ducting inlet. In some such examples, the refrigeration system pulls cooling airflow from the ducting outlet, cools, the cooling airflow, and passes the cooling airflow through the ducting inlet.

[0009] Also disclosed herein is a system for cooling a product. The system includes an enclosed environment including an inlet, an outlet, a first portion, and a second portion disposed opposite the first portion. The system further includes a conveyor system disposed within the enclosed environment and including a conveyor path extending between the inlet and the outlet, the conveyor path defining a helical travel path for the product. Also, the system includes an insert disposed in a central aperture of the helical travel path, such that the insert creates a monotonic negative pressure gradient from the first portion to the second portion. The system is configured to cool the product before the product exits the enclosed environment via the outlet.

[0010] In some variations, the insert comprises a top surface, a bottom surface, and an outer surface extending between the top surface and the bottom surface, wherein the outer surface is an angled surface. The insert may have cylindrical, conical, or helical symmetry. The insert may have a first diameter at the top surface and a second diameter at the bottom surface, the second diameter being larger than the first diameter. Additionally, the insert may include a fin disposed on at least a portion of an outer surface of the insert between the top surface and the bottom surface.

[0011] In other variations the pressure decreases monotonically from the first portion, over the product, through the second portion to the outlet, resulting in a single pass of cold air from the evaporator, through the first region, over the product, through the second region, and to the outlet where it is returned to the evaporator. In other words, the pressure gradient is negative along streamlines to facilitate a single pass through the first region, over the product, and out of the second region, whence it returns to the evaporator.

[0012] In yet other variations, the first portion is a top portion of the enclosed environment and the second portion is a bottom portion of the enclosed environment. Also the conveyor path has a first height and the insert has a second height larger than the first height.

[0013] Also disclosed herein is system for cooling a product. The system includes an enclosed environment including an inlet, an outlet, a first portion, and a second portion disposed opposite the first portion. Additionally, the system includes a conveyor system disposed within the enclosed environment and including a conveyor path extending between the inlet and the outlet, the conveyor path defining a helical travel path for the product. The system may also include a refrigeration system configured to generate a cooling airflow that flows from a ducting inlet arranged at or immediately proximate the first portion to a ducting outlet arranged at or immediately proximate the second portion. Furthermore, the system includes an insert disposed in a central aperture of the helical travel path, such that the insert creates a uniformly negative pressure gradient (ensuring there is only a single pass of cooling airflow over a product) from the first portion to the second portion. The cooling airflow may be configured to cool the product before the product exits the enclosed environment via the outlet.

[0014] In some variations, the uniformly negative pressure gradient is defined by a first pressure disposed proximately to the ducting inlet, a second pressure proximately to the ducting outlet, and a monotonic or approximately linear pressure transition from the first pressure to the second pressure. The uniformly negative pressure gradient may be a first uniformly negative pressure gradient in an annular passage of the enclosed environment and the insert may create a second uniformly negative pressure gradient in the central aperture from the first portion to the second portion, the second monotonic negative pressure gradient different from the first monotonic negative pressure gradient.

[0015] In other variations, the pressure gradient between the first and second portions over the product is uniformly negative to ensure a single pass of evaporator-cooled air of the product.

[0016] In yet other variations, the insert comprises a frustrum with a top surface, a bottom surface, and an outer surface extending between the top surface and the bottom surface, wherein the outer surface is an angled surface. Additionally, the insert may have a first diameter at the top surface and a second diameter at the bottom surface, the second diameter being larger than the first diameter. Additionally, the insert may include a fin disposed along at least a portion of the outer surface. Additionally, the insert may have curvature while retaining cylindrical or helical symmetry to facilitate optimal pressure gradient distributions over the various turns of the helical conveyor.

[0017] Furthermore, some variations include a system in which the first portion is a top portion of the enclosed environment and the second portion is a bottom portion of the enclosed environment.

[0018] Also disclosed herein is a method of cooling a product. The method may include simulating, using computational flow dynamics, a cooling cycle for the product, the cooling cycle comprises passing a cooling airflow through a conveyor system disposed within an enclosed environment, the conveyor system including a conveyor path extending between an inlet and an outlet of the enclosed environment, and the conveyor path defining a helical travel path for the product. The method may also include determining a flow profile of the cooling airflow during the cooling cycle, and based on the determined flow profile, modifying the conveyor system for the product to minimize recirculation of the cooling airflow back over the helical travel path. The method also includes performing the cooling cycle using the modified conveyor system.

[0019] In some variations, modifying the conveyor system for the product comprises modifying a radius and / or pitch angle of one or more spirals of the helical travel path. Additionally, modifying the conveyor system for the product can include modifying the insert disposed in the central aperture of the helical travel path. Further, determining the flow profile can include evaluating pressure gradients in the enclosed environment, and wherein modifying the conveyor system includes modifying a first pressure gradient in an annular passage outside the helical travel path and a second pressure gradient in a central aperture of the helical travel path.

[0020] Also disclosed herein is a method of cooling a product. The method can include simulating, using computational flow dynamics, a cooling cycle for the product, the cooling cycle comprises passing a cooling airflow through a conveyor system disposed within an enclosed environment, the conveyor system including a conveyor path extending between an inlet and an outlet of the enclosed environment, the conveyor path defining a helical travel path for the product, and an insert having an outer surface disposed in a central aperture of the helical travel path. The method may also include determining a flow profile of the cooling airflow during the cooling cycle. Additionally, based on the determined flow profile, the method includes modifying the conveyor system for the product to minimize recirculation of the cooling airflow back over the helical travel path and, performing the cooling cycle using the modified conveyor system.

[0021] In some variations, modifying the conveyor system for the product includes modifying a pitch angle, which entails changes to the spacing between one or more spirals of the helical travel path. Additionally, modifying the conveyor system for the product can include disposing a radially symmetric, conical, or helical insert in a central aperture of the helical travel path.

[0022] In other variations, determining the flow profile may include evaluating pressure gradients within the enclosed environment, and modifying the conveyor system includes modifying a first pressure gradient in an annular passage outside the helical travel path and a second pressure gradient around the insert in the central aperture. The method may also include minimizing recirculation of the refrigerated airflow by evaluating pressure gradients of the enclosed environment to determine the shape of the outer surface such that the refrigerated airflow passes over the helical travel path only once (avoiding recirculation of the airflow). The method may also include determining the shape of the outer surface of the insert relative to a longitudinal axis of the insert.

[0023] Also disclosed herein is a system for rapidly cooling a product. The system includes a conveyer system that transports product at a first temperature through a region with flowing air at a second temperature, the second temperature lower than the first temperature. The system also includes a refrigeration system that cools the flowing air to the second temperature and a blower situated between the refrigeration system and the product that circulates the flowing air over the product. Additionally, the blower, conveyer, and refrigeration system may be aligned to reduce the number of sequential convective heat transfer contacts between a portion of the flowing air and the product as it proceeds from the refrigeration system to the product and back to the refrigeration system.

[0024] In some variations, the conveyer system has a helical geometry defining a pitch adjusted to be greater than about 2 and fewer than about 5 boundary layer thicknesses based on the velocity, density, viscosity, and density of the flowing air. Fewer than two boundary layer thicknesses impedes heat transfer through contact with the product, and more than about five boundary layer thicknesses permits cold air to flow through the conveyer without contacting the product or otherwise facilitating heat transfer. This permits optimization of the size of the helical conveyer and overall system. The conveyor system may further include a thermally insulating or chilled surface that provides lateral acceleration of the flowing air directed down along a longitudinal axis of the conveyor system to obviate stagnation at the floor and to radially orient the flowing air.

[0025] Also disclosed herein is a method of rapidly cooling a product. The method includes assessing a flow trajectory of air through a conveyor system from a refrigeration system to a product and back to the refrigeration system using computational fluid dynamics. The method further includes adjusting a flow boundary layer thickness and conveyer geometry to reduce the number of convective heat transfer events between the air and the product that occur before the air is returned to the refrigeration system. Additionally, the method may include adjusting the pitch of the helix and / or the flow conditions to ensure that there is only one boundary layer to be at least one boundary layer but not more than approximately 2 boundary layers, 3 boundary layers, 4 boundary layers, 5 boundary layers, etc.

[0026] In some variations, the method also includes assessing the flow trajectory of air redirected by an insert disposed within the conveyor system.BRIEF DESCRIPTION OF DRAWINGS

[0027] The present disclosure is described in the following detailed description in conjunction with the drawings, wherein:

[0028] FIG. 1 illustrates a schematic diagram of a refrigeration system configured for use in the cooling systems of the present application.

[0029] FIG. 2 illustrates a side view of a convective heat transfer system.

[0030] FIG. 3 illustrates a graph of temperature change of a product over time as a function of the convective heat transfer coefficient.

[0031] FIG. 4 illustrates a graph of freezing times of a product for different heat transfer coefficients.

[0032] FIG. 5 is a side view of a flow system corresponding to cooling three products in accordance with prior art as described in the present disclosure.

[0033] FIG. 6 illustrates a graph of cooling dynamics of the products of FIG. 5 for air heat transfer.

[0034] FIG. 7 is a partial view of a conventional helical cooling system.

[0035] FIG. 8 is a perspective view of a second conventional helical cooling system.

[0036] FIG. 9 is a perspective view of the second conventional helical cooling system of FIG. 8.

[0037] FIG. 10 is a side view of the second conventional helical cooling system of FIG. 8.

[0038] FIG. 11 is a top view of the second conventional helical cooling system of FIG. 8.

[0039] FIG. 12 is a side view of example velocity flow data in the second conventional helical cooling system of FIG. 8.

[0040] FIG. 13 a perspective view of the second conventional helical cooling system of FIG. 8 including a plurality of recirculating streamlines.

[0041] FIG. 14 is a side view of an example system for cooling a product in accordance with the present disclosure.

[0042] FIG. 15 is a side view of an insert configured for use in the system of FIG. 14.

[0043] FIG. 16 is a perspective view of a second example system for cooling a product in accordance with the present disclosure.

[0044] FIG. 17 is a perspective view of a third example system for cooling a product in accordance with the present disclosure.

[0045] FIG. 18 is a perspective view of the third example system of FIG. 17 including example cooling air airflow lines.

[0046] FIG. 19 is a side view of the third example system for cooling a product including an example pressure gradient.

[0047] FIG. 20 is a side view of the third example system for cooling a product illustrating example flow streams with the length of the arrows proportional to the common logarithm of the velocity magnitude and the gray scale indicating static pressure in micropascals.

[0048] FIG. 21 is a flowchart illustrating an example method for cooling a product in accordance with the present disclosure.

[0049] FIG. 22 is a flowchart illustrating an example method for simulating a cooling cycle to virtually configure an insert in accordance with the present disclosure.

[0050] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and / or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments. It will further be appreciated that certain actions and / or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.DETAILED DESCRIPTIONDefinitions

[0051] The term convective heat transfer coefficient, as used herein, is the rate of heat transfer between a solid surface and a fluid per unit surface area per unit temperature difference. In symbolic form,h=qΔ⁢T,where h is the heat transfer coefficient in Watts / meter2Kelvin (W / m2K), q is the local heat flux density (W / m2), and ΔT is the temperature difference in Kelvin (K) between the solid and the fluid.The term conductive heat transfer, as used herein, is the flow of heat between two static materials that are in intimate thermal contact, as occurs between two solids or a solid and a liquid or gel that is not immobile.

[0053] The term radiative heat transfer, as used herein, is the flow of heat between two objects by electromagnetic radiation and moderated by wavelength-dependent differential emissivities.

[0054] The term target product, as used herein, is a finite sample of material to be cooled or frozen that is optionally encased in a thermally thin metal or polymer film.

[0055] The term refrigerant, as used herein, is a fluid that cools by evaporation and is subsequently condensed by compression.

[0056] The term coolant, as used herein, is a liquid that transports heat without changing to a gas or solid phase.Commercially Freezing Products

[0057] Freezing products in bulk may be time consuming and costly. For example, freezing a large quantity of products in bulk may take days and even weeks to completely freeze. Additionally, large quantities of product may be bulky and heavy, which increases overall costs. In order to cool such large quantities of product, helical cooling systems can be utilized to provide a consistent process for adequately cooling each product.Example Refrigeration System

[0058] FIG. 1 illustrates the operation of an example refrigeration system 100 for use in the example single pass refrigerators disclosed herein (described in greater detail in connection with FIGS. 7-20). The refrigeration system 100 includes an evaporator 102 and a condenser 104. A refrigerant is passed in a closed fluid system between the evaporator 102 and the condenser 104. The refrigerant changes phase to a vapor within the evaporator 102, absorbing thermal energy from the air (i.e., cooling the air). The refrigerant passes as a vapor along conduit 112 to the condenser 104. Within the condenser 104, the refrigerant changes phase to a liquid and is returned to the evaporator 102 along conduit 114. The conversion of vapor to liquid refrigerant uses compression and subsequent Joule-Thompson expansion. In various examples, the refrigeration system 100 may further include a pump (not shown) to convey the refrigerant through the refrigeration system 100.

[0059] Warm air 132 passes over the evaporator 102 and is cooled down. The cooled down air 134 is passed over an example conveyor system 142 conveying several products 144. As the cooled down air 132 passes over the products 144, the air is warmed up to be warm air 136. In some examples, warm air 136 returns to the evaporator 102 to be cooled again.Convective Cooling

[0060] FIGS. 2 and 3 illustrate an example convection heat transfer system 202 and a graph 302 of representative convection temperature change data. Convection based freezers pass air around the product. As shown in FIG. 2, airflow 204 passes around a product 206. The rate of heat flow between the product 206 and the airflow 204 is governed by convective, rather than conductive heat transfer (discussed in greater detail below). As is well recognized by those practiced in the art of thermal engineering, convective heat transfer depends on the physical properties of the fluid, the solid, and the flow conditions. The ratio of convective heat transfer to temperature difference, also known as the convective heat transfer coefficient h, is not a property of the fluid alone. It is an experimentally determined parameter whose value depends on all the variables influencing convection including the surface geometry, the nature of fluid motion, the properties of the fluid, the temperature, and the bulk fluid velocity. The impact of these variables on the rate of convective heat transfer for specific conditions can be calculated precisely using finite-element computational software as described above.

[0061] Representative ranges for convective heat transfer coefficients are based on the range of achievable solid and fluid properties including thermal conductivity, heat capacity, viscosity, density, and accessible flow velocities and are summarized in Table 1. The convective heat transfer coefficient to or from gases range from about 2 to no more than approximately 300 W / m2K, while that for liquids ranges from about 50 to as much as 10,000 W / m2K.TABLE 1Heat Transfer CoefficientProcess(W / m2K)Free ConvectionGases2-20 Liquids50-1000Forced ConvectionGases25-300 Liquids 100-40,000Convection with PhaseBoiling / Condensation2,500-100,000Change

[0062] The time required to complete the conversion from ambient temperature to the target temperature of the frozen product is a fundamental, rate-limiting unit operation for a continuous freezer. Decreasing this time permits higher throughput for a fixed refrigerant architecture, or a more compact device for specific throughput requirements.Freeze Times for Convective Cooling

[0063] FIG. 4 illustrates graph 400 of time to freeze a product based on different values of the convective heat transfer coefficient (h). A cold room with its air temperature set to −20° F. will freeze a water packet by passive convection (k~30 W / m2K) in just under two hours, whereas forced convection at h=1000 W / m2K reduces this time to 14 minutes, approaching the asymptotic value for conductive cooling of 8 minutes as the convective heat transfer coefficient approaches infinity.

[0064] The time required to complete the conversion from ambient temperature to the target temperature of the frozen product is a fundamental, rate-limiting unit operation for a continuous freezer. Decreasing this time obviously permits higher throughput for a fixed refrigerant architecture, or a more compact device for specific throughput requirements. An aspect of the present invention is to reduce, and preferably minimize, this time by ensuring that airflow is directed from the cooling system to pass over the product only once (single pass) before it is returned to the refrigerant system, which is most commonly an evaporator coil.

[0065] FIG. 5 illustrates a refrigeration experiment 500. A first product 512, a second product 514, and a third product 516 are in a cooling airflow 522. The first, second, and third products 512, 514, 516 are identical polyethylene bladders filled with water and disposed in the environment at an initial temperature of 75 degrees Fahrenheit (° F.). The cooling airflow 522, initially at 35° F., flows over the first, second, and third products 512, 514, 516, sequentially at an average velocity of 10 cm / s. Finite element conjugate heat transfer rates are evaluated using standard computational fluid dynamics methods. After the cooling airflow 522 passes over the first product 512, the first product 512 is cooled and the cooling airflow 522 is warmed. The warmed cooling airflow 522 subsequently cools the second product 514, but not as quickly as the first product 512. The second product 514 cools more slowly because the temperature difference between the warmed cooling airflow 522 and the second product 514 is less than the difference between the cooling airflow 522 and the first product 512. As a result, the first product 512 cools faster than the second product 514 and the third product 516. Similarly, the second product 514 cools faster than the third product 516.

[0066] FIG. 6 illustrates a graph 600 corresponding to cooling data 602 measured in the testing experiment 500. The cooling data 602 includes a first data line 612 (corresponding to the first product 512), a second data line 614 (corresponding to the first product 514), a third data line 616 (corresponding to the first product 516). As shown in the graph 600, the first product 512 cools faster than the second product 514 and the third product. For example, the first product cools from 75° F. to approximately 38° F. in the same time it takes the second product to cool from 75° F. to approximately 42° F. and the third product to cool from 75° F. to approximately 46° F.Prior Art Helical Cooling Systems

[0067] FIG. 7 illustrates one example of a known helical cooling system 700. The helical cooling system 700 includes a conveyor system 702, a refrigeration system 704, and an enclosed environment 706. As shown in FIG. 7, the refrigeration system 704 is disposed above the conveyor system 702, however in various other examples, the refrigeration system 704 could be disposed below the conveyor system 702 or on a side of the conveyor system 702.

[0068] The conveyor system 702 includes a helical travel path 712. The helical travel path 712 includes a plurality of successive levels 714a, 714b, 714c, . . . , 714n. The helical travel path 712 further defines a pitch angle 716 and a helical radius 718. In the illustrated example of FIG. 7, the pitch angle 716 and the helical radius are constant along a height 722 of the conveyor system 702. As a result, the height 724 between successive levels (e.g., between levels 714b and 714c) of the conveyor system 702 is constant. Additionally, the helical radius 718 is constant for each level 714a, 714b, 714c, . . . , 714n. As a result, each successive level 714a, 714b, 714c, . . . , 714n is directly above or below every other layer.

[0069] The conveyor system 702 is disposed in the enclosed environment 706. As illustrated in FIG. 7, the enclosed environment 706 includes four sidewalls 732a, 732b (the other two sidewalls not shown), a bottom wall 734, and a top wall (not shown). The conveyor system 702 includes a conveyor path extending from an inlet 736a to an outlet 736b. As shown, the outlet 736b passes through the sidewall 732a and the inlet 736a passes through a sidewall opposite the sidewall 732a (not shown). The inlet 736a is disposed proximately to the bottom wall 734, while the outlet 736b is disposed proximately to the top wall (not shown). In the illustrated example, the conveyor system 702 and the enclosed environment 706 share the longitudinal axis 740.

[0070] The refrigeration system 704 generates a cooling airflow 752 that is directed into the enclosed environment 706. The cooling airflow 752 passes over and through the conveyor system 702 to cool product being conveyed along the conveyor system. The cooling airflow 752 can recirculate off the sidewalls 732a, 732b and the bottom wall 734. Although the refrigeration system 704 directs the cooling airflow 752 into the enclosed environment 706 horizontally, in various examples, the refrigeration system 704 could directed the cooling airflow 752 at any angle and still cause recirculation off the sidewalls 732a, 732b, and the bottom wall 734.

[0071] In the known helical cooling system 700, when the cooling airflow 752 passes through the conveyor system 702 conveying products to be cooled, the cooling airflow 752 absorbs thermal energy from the products and the cooling airflow 752 is warmed. The warmed cooling airflow 754a, 754b then stagnates against the sidewalls and floor, then recirculates back over the product(s) on the conveyor system 702. For example, after the cooling airflow passes over a first product, the first product is partially cooled and the cooling airflow is partially warmed, but then the (warmer and recirculated) cooling airflow 754a, 754b passes over a second product, and the warmer cooling airflow 754a, 754b will be less effective at cooling the second product. This is because the heat transfer rate from the product to the cooling airflow 752 is directly proportional to the temperature difference between the product and the cooling airflow 752.

[0072] FIGS. 8, 9, 10, 11, 12, and 13 illustrate a second prior art helical cooling system 800 comprising an insulated enclosure 802, a spiral conveyor 804, and a blower 806 for producing a refrigerated airflow. In the illustrated example, the blower 806 directs air from evaporator coils (not shown) onto the spiral conveyer 804. A product is configured to enter the insulated enclosure 802 through entrance port 812. It is conveyed through the blast of cold air from the blower 806 as it traverses the spiral conveyor 804 and is thence conveyed to the exit port 814. The number of turns, the location of the entrance and exit ports and blower, and the position of the return to the coils can be varied based on the particular freezing requirements.

[0073] Referring to FIG. 9, streamlines show air emanating from the blower 806, traversing the helical conveyer at least twice and stagnating at the opposite wall before returning to the outlet. FIGS. 10 and 11 show the streamlines from side and top views, respectively.

[0074] FIG. 12 illustrates a velocity field 1202 corresponding to the blower 806 directing a cooling airflow into the insulated enclosure 802. As can be seen in FIG. 12, the velocity field 1202 is indicative of the cooling airflow passing through the spiral conveyor 804 and recirculating back onto the spiral conveyor 804.

[0075] Freezer geometries, such as are shown in FIGS. 7, 8, 9, 10, 11, 12, and 13, may be evaluated using computational fluid dynamics calculations to establish conditions under which convective or conjugate heat transfer occurs between the product and the flowing air. A typical result of these calculations (COMSOL Multiphysics version 6.1, COMSOL, Burlington, MA) shows the velocity magnitude in the y-z plane where x=0. The average velocity is 0.1 m / s, and the peak velocity of the cold air is 0.18 m / s in this exemplar calculation. Referring to FIGS. 9, 10, and 11, three streamlines for air emanating from the blower 806 are shown in the top view (FIG. 11), the side view (FIG. 10), and the orthographic view (FIG. 9). The streamlines that emanate from the blower 806 impinge directly on the spiral conveyor 804, with heat transfer occurring from warm product to cooler air. This warmed air subsequently traverses an inner region of the spiral conveyor 804 before impinging again on product, but this time since its temperature exceeds that of the air coming directly from the blower 806 it is less able to extract further heat from the posterior product. In other words, the heat transfer coefficient, which is determined in detail by the flow conditions surrounding the product, may not change but the temperature difference between the air and product is reduced after every contact with product.

[0076] FIG. 13 illustrates the second helical cooling system 800 including a plurality of recirculating streamlines 1302. The plurality of recirculating streamlines 1302 illustrate that all of the airflow provided by the blower 806 pass over the spiral conveyor 804 two or more times, at least in part because the cooling airflow recirculates and passes back over the spiral conveyor 804.Example Improved Helical Cooling Systems

[0077] The present disclosure is directed to cooling systems that provide rapid, on-demand solutions for cooling products. Generally speaking, the cooling systems as described herein receive a plurality of products in an unfrozen state and deliver the plurality of products in a refrigerated or frozen state. For simplicity, cooling systems may cool product to arbitrary temperatures including those that cause a phase change to the product.

[0078] In various examples of improved cooling systems described herein, the cooling system is configured to reduce air recirculation in the enclosed environment of the cooling system. By reducing recirculation, the cooling system maximizes the rate of heat transfer between the product and the chilled air. As a result, the overall system is more efficient than known cooling systems such as the known helical cooling system 700 discussed above. Thus, the cooling system is more energy efficient. The cooling systems of the present disclosure improves efficiency by limiting recirculation of the cooling airflow in the cooling system such that only the coldest air passes over the product. In some examples, the cooling system of the present invention has reduced size, weight, and / or power consumption.

[0079] In one example, the airflow from the evaporator coils flows directly down the center of the helical conveyer belt, but with an addition. If the center of the helix is unobstructed the cold air may stagnate on the floor and recirculate inside the helix, resulting in multiple convective heat transfer events with spiraling product. A nominally conical insulating body in the center of the helix provides controlled lateral deflection of the cooled air from within to without the helix in a single pass.

[0080] FIG. 14 illustrates a first example of an improved helical cooling system 1400 for cooling a product in accordance with the present disclosure. The system 1400 includes a conveyor system 1402, a refrigeration system 1404, and an enclosed environment 1406. Additionally, the system 1400 includes a ducting system 1407 and an insert 1408, though in other examples, the system 1400 need not include the ducting system 1407 or the insert 1408.

[0081] As shown in FIG. 14, the conveyor system 1402 is in the enclosed environment 1406 and includes a helical travel path 1412. The helical travel path 1412 includes a plurality of successive levels 1414a, 1414b, 1414c, . . . , 1414n. The helical travel path 1412 further defines a pitch angle 1416 and a helical radius 1418. In the illustrated example of FIG. 14, the pitch angle 1416 is constant along a height 1422 of the conveyor system 1402. As a result, the height 1424 between successive levels (e.g., between levels 1414b and 1414c) of the conveyor system 1402 is constant. Additionally, the helical radius 1418 is constant for each level 1414a, 1414b, 1414c, . . . , 1414n. As a result, each successive level 1414a, 1414b, 1414c, . . . , 1414n is directly above or below every other layer. In various other examples, the pitch angle 1416 and / or the helical radius 1418 may be larger or smaller than illustrated in FIG. 14. Additionally or alternatively, the pitch angle 1416 and / or the helical radius 1418 may be variable. In such examples, the height 1424 between successive layers 1414a, 1414b, 1414c, . . . , 1414n may vary (i.e., not be constant) and / or the successive layers 1414a, 1414b, 1414c, . . . , 1414n may not be disposed directly above and below every other layer in the manner illustrated in FIG. 14. The pitch of the successive layers needs to be at least twice the boundary layer thickness for the flow around the product, whether this is laminar or turbulent, to make efficient use of convective contact with the product.

[0082] The example conveyor system 1402 is in the enclosed environment 1406. As illustrated in FIG. 14, the enclosed environment 1406 in this example includes a cylindrical sidewall 1432, a bottom wall 1434, and a top wall 1436 opposite the bottom wall 1434. In various other examples, the sidewall may be rectangular, as described in connection with the enclosed environment 706 of FIG. 7, or have a different shape. In the illustrated example, the conveyor system 1402 includes a conveyor path extending from an inlet 1436a to an outlet 1436b. The inlet 1436a and the outlet 1436b pass through the sidewall 1432. In the illustrated example, the inlet 1436a is disposed proximately to the bottom wall 1434 and the outlet 1436b is disposed proximately to the top wall 1436, but in other examples, the location of the inlet 1436a and the outlet 1436b could be reversed and the outlet 1436b could instead be disposed proximately to the bottom wall 1434. In the illustrated example, the conveyor system 1402 is centrally disposed in the enclosed environment 1406, such that the conveyor system 1402 and the enclosed environment 1406 share the longitudinal axis 1440 (i.e., the conveyor system 1402 and the enclosed environment are co-axial with one another). However, in various other examples, the conveyor system 1402 may not be centrally disposed in the enclosed environment.

[0083] In the illustrated example of FIG. 14, the enclosed environment 1406 further includes a first portion 1442a at or near the top of the enclosed environment 1406 and a second portion 1442b at or near a bottom of the enclosed environment 1406, the first and second portions 1442a, 1442b disposed opposite each other. The ducting system 1407 is connected to the enclosed environment 1406 such that a ducting inlet 1444 of the ducting system 1407 is arranged at or immediately proximate the first portion 1442a and a ducting outlet 1446 of the ducting system 1407 is arranged at or immediately proximate the second portion 1442b. In other variations, the first portion 1442a and the second portion 1442b may instead be disposed in the sidewall 1432 of the enclosed environment 1406, in which case the ducting inlet 1444 and the ducting outlet 1446 can also be arranged in the sidewall 1432 of the enclosed environment 1406.

[0084] Each of the ducting inlet 1444 and the ducting outlet 1446 is in fluid communication with the enclosed environment 1406 and the refrigeration system 1404. The ducting inlet 1444, the enclosed environment 1406, the ducting outlet 1446, and the refrigeration system 1404 are in fluid communication with one another and together form a loop. The refrigeration system 1404 can be, for example, similar to or substantially identical to the refrigeration system described in connection with FIG. 1. In the example of FIG. 14, the refrigeration system 1404 generates a cooling airflow 1452 which passes through the ducting inlet 1444, into the enclosed environment 1406, and out through the ducting outlet 1446. The cooling airflow 1452, having been warmed (1456) by a single pass over the product then passes through the ducting outlet 1446 back to the refrigeration system 1404. In other words, the enclosed environment 1406 will have a first pressure at the ducting inlet 1444 and a second, lower pressure at the ducting outlet 1446, such that the enclosed environment 1406 has or defines a monotonic negative pressure gradient from the ducting inlet 1444 to the ducting outlet 1446. In some alternative examples, the cooling airflow 1452 could be reversed such that the enclosed environment 1406 has a pressure gradient that causes cooling airflow 1452 to flow from the second portion 1442b to the first portion 1442a. In various examples, the ducting inlet, ducting outlet, and / or refrigeration system may include a fan or other apparatus to generate the pressure gradient (e.g., pump the cooling airflow 1452)

[0085] The inventors of the present disclosure have unexpectedly discovered that the inclusion of the insert 1408 in the system 1404 improves the efficiency of the cooling system 1400. More particularly, the inventors have unexpectedly discovered that disposing the insert 1408 in the conveyor system 1402 and the enclosed environment 1406 improves the efficiency of the cooling system 1400 by altering the negative pressure gradient so that the gradient is more uniform and so that the cooling airflow 1452 passes from the central aperture 1464a to an annular passage 1464b circumscribing the conveyor system 1402 while passing from the first portion 1442a to the second portion 1442b. In the illustrated example of FIG. 14, the insert 1408 is disposed in the conveyor system and the enclosed environment 1406 such that the insert 1408 is also centrally located about the central longitudinal axis 1440 (i.e., the insert 1408 is coaxial with the conveyor system 1402 and the enclosed environment 1406). To this end, at least in this example, the insert 1408 is disposed in a central aperture 1464a of the conveyor system 1402. In other examples, the enclosed environment 1406, the conveyor system 1402, and / or the insert 1408 may not be coaxial. In any event, due to the highly efficient airflow movement of the cooling airflow 1452 through the enclosed environment 1406 and through the conveyor system 1402, the cooling airflow 1452 is configured to cool a product traveling on the conveyor path in the time it takes the product to travel from the inlet 1436a to the outlet 1436b. In various examples, cooling a product could include reducing the temperature of the product until the product is frozen, semi-frozen, or cooled to a desired temperature.

[0086] As illustrated in FIG. 15, the insert 1408 includes a top surface 1512, a bottom surface 1514, and an outer surface 1516 disposed between the top surface 1512 and the bottom surface 1514. In this example, the outer surface 1516 extends, in a straight line, between the top surface 1512 and the bottom surface 1514, but in other examples, the outer surface 1516 can be curved and / or include angled surfaces to control airflow. In preferred examples, the insert 1408 is made from an insulated material, such as, for example, a closed-cell polyurethane foam.

[0087] In the present example, the top surface 1512 and the bottom surface 1514 are both circular. In other examples, the top surface 1512 and the bottom surface 1514 may be a different regular or irregular shape (e.g., a square, triangle, hexagon, etc.). As illustrated, the top surface 1512 has a first diameter 1522 and the bottom surface 1514 has a second diameter 1524 that is larger than the first diameter 1522. The insert 1408 further has an insert height 1526 measured between the top surface 1512 and the bottom surface 1514. In preferred examples, the insert height 1526 is greater than the height 1422 of the conveyor system. The difference in diameter between the top surface 1512 and the bottom surface 1514 causes the outer surface 1516 to be oriented at an angle 1532 (taper angle) relative to a central longitudinal axis 1534. In the present example, the angle 1532 is an acute angle of approximately 10 degrees (°). In various other examples, the angle 1532 could be as little as 0° or as great as 45°.

[0088] As shown in FIG. 15, the insert 1408 is a right conical frustum (i.e., a truncated cone between parallel surfaces), but in some examples, the insert may be shaped more like a conical or other polygonal frustum. In such examples, the diameter 1522 of the top surface 1512 and / or the diameter of the bottom surface 1514 may be reduced to a point. Additionally or alternatively, the outer surface 1516 may have a concavely or convexly curved surface between the top surface 1512 and the bottom surface 1514. Alternative examples of the insert 1408 will be discussed in greater detail in connection with FIGS. 16 and 17.

[0089] When the insert 1408 is disposed in the central aperture 1464a of the conveyor system 1402 as illustrated in FIG. 14, the outer surface 1516 increases the pressure in the central aperture 1464a. The outer surface 1516 increases the pressure in the central aperture 1464a by reducing the cross-sectional area in the central aperture 1464a. Additionally, the insert 1408 uniformly (or substantially uniformly) deflects the cooling airflow 1452 out of the central aperture 1464a by directing the cooling airflow 1452 in the direction of the annular passage 1464b. In other examples, the insert 1408 could be differently shaped, but still reduce recirculation of the cooling airflow 1452 over the conveyor system 1402.

[0090] Additionally, in some examples, the insert may be actively cooled and configured to further reduce the temperature of the cooling airflow before it encounters a product.

[0091] FIG. 16 illustrates a second example of a system 1600 for cooling a product in accordance with the present disclosure. The system 1600 is substantially identical to the cooling system 1400. For example, similar to the cooling system 1400, the cooling system 1600 includes a conveyor system 1602, a refrigeration system 1604, and an enclosed environment 1606 (shown as transparent in FIG. 16). In the present example, the insert 1608 is similar to the insert 1408, but includes a fin 1609, helically wrapped around the insert 1608.

[0092] The example fin 1609 directs cooling airflow across the conveyor system 1602. In the illustrated example, the fin 1609 is disposed at the same height as the conveyor system 1602 radially adjacent to the fin 1609. In other examples, the fin 1609 could be elevated above the conveyor system 1602 radially adjacent to the fin 1609. As used herein, the portion of the conveyor system 1602 radially adjacent to the fin 1609 is the portion of the conveyor system 1602 closest to a given portion of the fin 1609.

[0093] In various examples, the fin 1609 could be disposed on the insert 1608 in any manner to direct a cooling airflow over the conveyor system 1602. For example, the fin 1609 could include a series of segmented fins. In such example, each of the segmented fins could be horizontal, instead of helically angled downwards. If the segmented fins are horizontal, there is less risk the cooling airflow would circulate circumferentially around the insert 1608 and the conveyor system 1602.

[0094] Furthermore, the fin 1609 could be angled relative to the insert 1608. For example, the fin 1609 could be angled towards the conveyor 1602. Further, the radial width of the fin 1609 could be different than shown in FIG. 16. In some examples, the radial width of the fin 1609 could be variable along the length of the fin 1609 (e.g., wider in some areas and narrower in others).

[0095] The enclosed environment 1606 additionally includes a bottom grate 1612. The cooling airflow generated by the refrigeration system 1604 flows through the bottom grate 1612. In some examples, the system 1600 includes ducting (not shown) to recirculate the cooling airflow from the bottom grate back to the refrigeration system 1604. In the various examples, the cooling system 1400 (discussed above) and / or the cooling system 1700 (discussed below) could also include similar bottom grate 1612 to recirculate cooling airflow to the refrigeration system. In various examples, the bottom grate 1612 could be coupled to an air pumping system that creates a low pressure zone along the bottom grate 1612 and further pulls the cooling airflow through the grate and back to the refrigeration system 1604. Additionally, the refrigeration system 1604 could include a blower to push cooling airflow into the enclosed environment 1606.

[0096] FIGS. 17, 18, 19, and 20 illustrate a second example of a system 1700 for cooling a product in accordance with the present disclosure. The system 1700 is substantially identical to the cooling system 1400 and the cooling system 1600. For example, similar to the cooling system 1400, the cooling system 1700 includes a conveyor system 1702, a refrigeration system 1704, and an enclosed environment 1706 (shown as transparent in FIGS. 17 and 18). In the present example, the insert 1708 is similar to the insert 1408, but is conical.

[0097] In the present example, the insert 1708 is conical. As discussed above, the insert 1708 could be any of a variety of shapes. In the present example, the conical shape of the insert 1708 fills an inner space 1712 of the conveyor system and directs cooling airflow from the inner space 1712 to the annular space 1714. The shape and location of the insert serve to prevent stagnation and recirculation of air at the bottom of the interior of the helical conveyer. The conical shape of the insert 1708 is shown by way of example. The insert 1708 could be cylindrical, pyramidal, or a frustum (described in connection with FIGS. 14-15).

[0098] As shown in FIG. 18, the refrigeration system 1704 generates cooling airflow 1802 with streamlines starting at the refrigeration system 1704. The refrigeration system directs the cooling airflow 1802 downward (in some examples, via a blower (not shown)). To direct the cooling airflow 1802 downward, the refrigeration system 1704 could include a fan or blower (not shown). The insert 1708 redirects the cooling airflow 1802 outward from the inner space 1712 toward the annular space 1714 when the cooling airflow 1802 impinges on the insert 1708. In various examples, the shape of the insert 1708 can be adjusted to direct the flow through the conveyor system 1702.

[0099] FIG. 19 illustrates contours of static pressure in microPascals where the pressure is zero at the bottom of the figure. The pressure within the inner space 1712 is substantially higher than the annular space 1714 leading to a single pass of cooled air from the inlet over the product and out the exhaust on the bottom of the figure.

[0100] FIG. 20 further illustrates that a cooling airflow in the enclosed environment 1706 having the insert 1708 does not recirculate over the conveyor system 1702. The grayscale shows static pressure, which is substantially higher within the inner space 1712 than the annular space 1714 the helical conveyor. Arrows indicate local flow direction in the y=0 plane with their length proportional to the common logarithm of the velocity magnitude. In other words, flow is substantially faster within the helix than without. As can be seen in FIG. 20, the cooling airflow 2052 flows downwards into the inner space 1712, laterally from the inner space 1712 to the annular space 1714, and downward through the annular space 1714. As a result, the cooling airflow 2052 does not recirculate back from the annular space 1714 to the inner space 1712.

[0101] FIG. 21 illustrates an example of a method 2100 for cooling a product using, at least in part, a cooling system such as the cooling system 1400 of FIG. 14, the cooling system 1600 of FIG. 16, and / or the cooling system 1700 of FIGS. 17-20. While the method in this example is described as including steps performed once and in a particular order, in various other examples, the steps of the method 2100 can be reordered and / or performed multiple times.

[0102] In various examples, the method 2100 may be entirely or partially performed by a controller communicatively connected to the cooling system (e.g., cooling system 1400, 1600, 1700). The controller may include a microprocessor, a memory, and one or more wired and / or wireless communication links. The controller may be coupled to one or more components of the cooling system via one or more of the communication links. For example, the communication links may couple the controller to the refrigeration system of the cooling system and / or to motors disposed in the conveyor system. In some examples, the controller can be communicatively connected to at least one sensor disposed in or proximately to the enclosed environment via one or more of the communication links. For example, the sensor may be a temperature sense, airflow sensor, pressure sensor, optical sensor, etc. The controller can be configured to receive sensor data from each of the sensors, process the sensor data, and control the cooling system based on the sensor date. Accordingly, the controller can, for example, control the temperature in the enclosed environment and the speed at which product is moved along the conveyor system.

[0103] At step 2102 (shown in greater detail in connection with FIG. 22), the method 2100 includes simulating, using computational fluid dynamics, a cooling cycle for the product, the cooling cycle including passing a cooling airflow (e.g., cooling airflow 1452) through a conveyor system (e.g., conveyor system 1402) disposed within an enclosed environment (e.g., enclosed environment 1406), the conveyor system including a conveyor path extending between an inlet (e.g., inlet 1436a) and an outlet (e.g., outlet 1436b) of the enclosed environment (e.g., enclosed environment 1406), and the conveyor path defining a helical travel path for the product, the simulating will be performed using computational flow dynamics (CFD) software and generally involves analyzing thermodynamics, structural mechanics, and fluid mechanics in the cooling system. Further, the simulation may involve iterative designing and modifying the simulations to obtain an optimized system. In some examples, this simulation includes virtually generating variations of inserts and ducting systems.

[0104] At step 2104, the method 2100 includes determining a flow profile of the cooling airflow during the simulated cooling cycle. The flow profile may, for example, be identical or similar to the flow diagram shown in FIG. 21. Based on the flow profile, at step 2106 the method 2100 includes modifying the conveyor system to adjust the flow profile in order to minimize recirculation of the cooling airflow back over the helical travel path. Adjustments to the conveyor system include, but are not limited to, including an insert (e.g., the insert 1408), adjusting the shape, size, or placement of the insert, adjusting the ducting for the cooling airflow, adjusting a pitch angle and / or a radius of the conveyor system, adjusting the dimensions (e.g., the height) of the conveyor system, and adjusting flow parameters associated with the conveyor system (e.g., the rate at which the conveyor system moves, the duration of the cooling cycle).

[0105] For example, modifying the conveyor system can involve simulating the usage of an insert in the cooling system during the cooling cycle, adjusting the shape and size of the insert, and examining the effect the insert has on the cooling airflow during the subsequent cooling cycle. Adjusting the ducting can, for example, involve adjusting the size of the ducting inlet and / or the ducting outlet, and / or adjusting the location of the ducting inlet and the outlet in the enclosed environment. Also, adjusting the pitch angle of the conveyor system can include adjusting the space between successive layers of the conveyor system to maximize turbulent airflow over the produce and also adjust the time a product spends in the enclosed environment. Lastly, the dimensions of the conveyor system (e.g., cross sectional size of the conveyor system, length of the conveyor system, etc.) can be adjusted to improve cooling airflow movement in the enclosed environment.

[0106] At step 2108, the method 2100 includes evaluating the flow profile to determine if recirculation has been sufficiently minimized following the modification of the conveyor system. Preferably, the CFD software will simulate a cooling cycle performed using the modified conveyor system and then evaluate the flow profile accordingly. In some cases, the CFD software will iteratively perform this process. If evaluation of the flow profile shows that the airflow still has too much recirculation or is otherwise too inefficient, the method 2100 returns to step 2102 to simulate and modify the cooling cycle again. However, if the flow profile shows that the airflow has sufficiently reduced recirculation or is otherwise sufficiently efficient, the method 2100 proceeds to step 2110. At step 2110, the cooling cycle is performed, using the modified conveyor system. In some examples, the method 2100 may also include evaluating the flow profile of the airflow during the actually performed (i.e., non-simulated) cooling cycle to determine if the modifications to the conveyor system sufficiently minimized recirculation (or, if not, whether further modifications are necessary).

[0107] FIG. 22 illustrates an example of how the step 2102 of the method 2200 can be performed. In this example, the step 2102 includes a first sub-step 2202 of virtually generating the conveyor system as disposed in the enclosed environment. After generating the conveyor system and the enclosed environment, the step 2102 includes, optionally, virtually generating the insert (at sub-step 2204) and / or virtually generating the cooling airflow ducting (at sub-step 2206). The virtually generated insert may be disposed in a central aperture of the conveyor system. Sub-step 2204 may also include virtually generating a plurality of variations of the insert (e.g., differently sized and / or shaped inserts).

[0108] Lastly, at sub-step 2208, the step 2102 includes using the computational fluid flow dynamics software to simulate the cooling cycle in which the cooling airflow flows in the enclosed environment and around the conveyor system. In some examples, the simulation may identify regions of drastic pressure differentials or fluid eddies. Additionally, in some examples, the computational fluid dynamics software may analyze the transition of fluid flow between laminar flow and turbulent flow and the ability of a cooling airflow to cool a product. The information generated at step 2208 may then be used to determine the flow profile at step 2104.

[0109] Restriction of the cooling airflow to a single pass over the product before returning to the evaporator reduces the average temperature of the return air. As a result, the heat load on the refrigeration system is minimized resulting in lower energy use. Furthermore, optimization of the flow conditions including the single pass over product may reduce the blower requirements, which in typical prior-art systems use about one third of the freezer system energy.

[0110] Those skilled in the art will recognize that a wide variety of modifications, alterations, and combinations can be made with respect to the above described examples without departing from the spirit and scope of the invention(s) disclosed herein, and that such modifications, alterations, and combinations are to be viewed as being within the ambit of the inventive concept(s).

Examples

Embodiment Construction

Definitions

[0051]The term convective heat transfer coefficient, as used herein, is the rate of heat transfer between a solid surface and a fluid per unit surface area per unit temperature difference. In symbolic form,

h=qΔ⁢T,

where h is the heat transfer coefficient in Watts / meter2Kelvin (W / m2K), q is the local heat flux density (W / m2), and ΔT is the temperature difference in Kelvin (K) between the solid and the fluid.

The term conductive heat transfer, as used herein, is the flow of heat between two static materials that are in intimate thermal contact, as occurs between two solids or a solid and a liquid or gel that is not immobile.

[0053]The term radiative heat transfer, as used herein, is the flow of heat between two objects by electromagnetic radiation and moderated by wavelength-dependent differential emissivities.

[0054]The term target product, as used herein, is a finite sample of material to be cooled or frozen that is optionally encased in a thermally thin metal or polymer film...

Claims

1. A system for cooling a product, comprising:an enclosed environment including an inlet, an outlet, a first portion, and a second portion disposed opposite the first portion;a conveyor system disposed within the enclosed environment and including a conveyor path extending between the inlet and the outlet, the conveyor path defining a helical travel path for the product; anda refrigeration system configured to generate a cooling airflow that flows from a ducting inlet arranged at or immediately proximate to the first portion to a ducting outlet arranged at or immediately proximate to the second portion;wherein the enclosed environment has a monotonic negative pressure gradient from the first portion over the product and to the second portion;wherein the cooling airflow is configured to cool the product before the product exits the enclosed environment via the outlet;wherein the helical travel path defines a constant pitch configured to accommodate at least two boundary layers thicknesses of the cooling airflow, andwherein the pitch of the helical travel path is configured to allow at least two, but no more than five, boundary layers between successive helices and thereby minimize a height of a helical conveyer for a given radius.

2. The system of claim 1, wherein the monotonic negative pressure gradient is defined by a first pressure proximate to the ducting inlet, a second pressure proximate to the ducting outlet, and a monotonic pressure transition from the first pressure to the second pressure.3-4. (canceled)5. The system of claim 1, wherein the helical travel path defines a constant radius.

6. The system of claim 1, wherein the first portion is a top portion of the enclosed environment and the second portion is a bottom portion of the enclosed environment.

7. The system of claim 5, wherein the inlet is disposed proximately to the first portion and the outlet is disposed proximately to the second portion.

8. A system for cooling a product, comprising:an enclosed environment including an inlet, an outlet, a first portion, and a second portion disposed opposite the first portion;a conveyor system disposed within the enclosed environment and including a conveyor path extending between the inlet and the outlet, the conveyor path defining a helical travel path for the product; anda refrigeration system configured to generate a cooling airflow that flows from a ducting inlet arranged at or immediately proximate to the first portion to a ducting outlet arranged at or immediately proximate to the second portion,wherein the enclosed environment has a monotonic negative pressure gradient from the first portion over the product and to the second portion,wherein the cooling airflow is configured to cool the product before the product exits the enclosed environment via the outlet, andwherein the ducting outlet comprises a grate disposed in the second portion of the enclosed environment.

9. The system of claim 8, wherein the enclosed environment is a first enclosed environment, the system further comprising a second enclosed environment, wherein the second enclosed environment is in fluid communication with the ducting outlet, the refrigeration system, and the ducting inlet.

10. The system of claim 9, wherein the refrigeration system pulls cooling airflow from the ducting outlet, cools the cooling airflow, and passes the cooling airflow through the ducting inlet.

11. The system of claim 10, wherein the cooling airflow has a first temperature at the ducting inlet and a second temperature at the ducting outlet, the second temperature being higher than the first temperature; andwherein the system minimizes a difference between the second temperature and the first temperature to reduce a power consumption of the refrigeration system.

12. A system for cooling a product, comprising:an enclosed environment including an inlet, an outlet, a first portion, and a second portion disposed opposite the first portion;a conveyor system disposed within the enclosed environment and including a conveyor path extending between the inlet and the outlet, the conveyor path defining a helical travel path for the product;an insert disposed in a central aperture of the helical travel path, such that the insert creates a monotonic negative pressure gradient from the first portion to the second portion;wherein the system is configured to cool the product before the product exits the enclosed environment via the outlet;wherein the insert comprises a top surface, a bottom surface, and an outer surface extending between the top surface and the bottom surface, wherein the outer surface is an angled surface;wherein the insert has a first diameter at a top surface and a second diameter at a bottom surface, the second diameter being larger than the first diameter; andwherein the insert includes a fin disposed on at least a portion of an outer surface of the insert between the top surface and the bottom surface.13-15. (canceled)16. The system of claim 12, wherein the insert is actively cooled.

17. The system of claim 12, wherein the monotonic negative pressure gradient is a first monotonic negative pressure gradient in an annular passage of the enclosed environment and the insert creates a second monotonic negative pressure gradient in the central aperture from the first portion to the second portion, the second monotonic negative pressure gradient different from the first monotonic negative pressure gradient.

18. The system of claim 17, wherein for a given distance from the first portion and the second portion, the first monotonic negative pressure gradient defines a first pressure and the second monotonic negative pressure gradient defines a second pressure, the second pressure greater than the first pressure.

19. The system of claim 12, wherein the first portion is a top portion of the enclosed environment and the second portion is a bottom portion of the enclosed environment.

20. The system of claim 12, wherein the conveyor path has a first height and the insert has a second height larger than the first height.

21. A system for cooling a product, comprising:an enclosed environment including an inlet, an outlet, a first portion, and a second portion disposed opposite the first portion;a conveyor system disposed within the enclosed environment and including a conveyor path extending between the inlet and the outlet, the conveyor path defining a helical travel path for the product;a refrigeration system configured to generate a cooling airflow that flows from a ducting inlet arranged at or immediately proximate to the first portion to a ducting outlet arranged at or immediately proximate to the second portion;an insert disposed in a central aperture of the helical travel path, such that the insert creates a monotonic negative pressure gradient from the first portion to the second portion;wherein the cooling airflow is configured to cool the product before the product exits the enclosed environment via the outlet;wherein the monotonic negative pressure gradient is defined by a first pressure disposed proximately to the ducting inlet, a second pressure proximate to the ducting outlet, and a monotonic pressure transition from the first pressure to the second pressure; andwherein the monotonic pressure gradient is a first monotonic negative pressure gradient in an annular passage of the enclosed environment and the insert creates a second monotonic negative pressure gradient in the central aperture from the first portion to the second portion, the second monotonic negative pressure gradient different from the first monotonic negative pressure gradient.22-23. (canceled)24. The system of claim 21, wherein for a given distance from the first portion and the second portion, the first monotonic negative pressure gradient defines a first pressure and the second monotonic negative pressure gradient defines a second pressure, the second pressure greater than the first pressure.

25. The system of claim 24, wherein the first and second monotonic pressure gradients permit the cooling airflow to pass over the product only once before passing through the ducting outlet and returning to the refrigeration system, thereby reducing a power consumption of the refrigeration system.

26. The system of claim 21, wherein the insert comprises a top surface, a bottom surface, and an outer surface extending between the top surface and the bottom surface, wherein the outer surface is an angled surface.

27. The system of claim 26, wherein the insert has a first diameter at the top surface and a second diameter at the bottom surface, the second diameter being larger than the first diameter.

28. The system of claim 26, wherein the insert includes a fin disposed along at least a portion of the outer surface.

29. The system of claim 26, wherein the insert is actively cooled.

30. The system of claim 21, wherein the first portion is a top portion of the enclosed environment and the second portion is a bottom portion of the enclosed environment.31-44. (canceled)

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