WO2012050575A1

WO2012050575A1 - Crossflow spiral heat transfer system with self-stacking spiral conveyor belt

Info

Publication number: WO2012050575A1
Application number: PCT/US2010/052454
Authority: WO
Inventors: Stephen A. Mccormick; Michael D. Newman
Original assignee: Linde Aktiengesellschaft
Priority date: 2010-10-13
Filing date: 2010-10-13
Publication date: 2012-04-19
Also published as: US20110247355A1

Abstract

A refrigeration system includes a housing having a top, a bottom, first and second opposed sides, and containing an atmosphere; a conveyor apparatus including a self- stacking, self-supported, spiral conveyor belt and a drive mechanism, wherein the conveyor belt includes a plurality of tiers and is at least partially disposed within the housing such that the conveyor belt can travel within the housing from the bottom towards the top of the housing or from the top towards the bottom of the housing; and an atmosphere circulation apparatus having at least one blower in communication with the atmosphere for circulating at least a portion of the atmosphere within the housing from proximate the first opposed side to the second opposed side and back towards the first opposed side, wherein the portion of the atmosphere circulated passes over the conveyor belt in a crossflow manner at least once.

Description

SPECIFICATION

CROSSFLOW SPIRAL HEAT TRANSFER SYSTEM WITH SELF- STACKING SPIRAL CONVEYOR BELT

[0001] The present disclosure relates to a heat transfer system for cooling, chilling or otherwise removing heat from, or warming, heating or otherwise supplying heat to products, such as for example food products.

[0002] In certain illustrative refrigeration systems, a line of products to be refrigerated is moved through the refrigeration system, along a spiral or helical pathway through the cold or chilling region. Systems in which products to be refrigerated follow a spiral or helical pathway through the cold region are conventionally termed spiral refrigeration systems. Related systems may be used to supply heat to products.

[0003] One type of refrigeration system used in the industry to remove heat from products is a spiral refrigeration system. Unless otherwise noted, as used herein, "spiral" refers to both spiral and helical forms, as well as any other forms which allow for similar movement of products through the heat transfer system.

[0004] A single pass configuration spiral refrigeration system is one in which a gas, such as a cryogen, is directed by at least one blower, such as at least one fan, to flow past the products to be cooled once. The gas is then returned from the products to the at least one blower through return gas conveyances in the system. The return gas conveyances may, in certain embodiments, consist of ductwork which does not contain products from which it is desirable to remove heat.

[0005] A double pass configuration spiral refrigeration system is one in which a gas, such as a cryogen, is directed by at least one blower, such as at least one fan, to flow past the products to be cooled twice. The gas is circulated past the products once, then passes over the products a second time as it returns to the at least one blower. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Embodiments of the subject matter are disclosed with reference to the accompanying drawings and are for illustrative purposes only. The subject matter is not limited in its application to the details of construction or the arrangement of the components illustrated in the drawings. Like reference numerals are used to indicate like components, unless otherwise indicated.

[0007] FIG. 1 shows a cross-section elevation view of an embodiment of a heat transfer system.

[0008] FIG. 2 shows a top cross-section plan view of the embodiment of FIG. 1.

[0009] FIG. 3 shows a cross-section elevation view of another embodiment of a crossflow spiral heat transfer system.

[0010] FIG. 4 shows a cross-section elevation view of an embodiment of a single pass crossflow heat transfer system for a self-stacking spiral conveyor belt apparatus.

[0011] FIG. 5 shows a cross-section elevation view of another embodiment of a single pass crossflow heat transfer system for a self-stacking spiral conveyor belt apparatus.

[0012] FIG. 6 shows a cross-section elevation view of an embodiment of a double pass crossflow heat transfer system for a self-stacking spiral conveyor belt apparatus.

DESCRIPTION OF THE INVENTION

[0013] Discussion of the heat transfer system embodiments is with respect to cooling and heating a product, and reference to refrigeration systems could similarly include references to a heating system. [0014] Variables defining a spiral pathway include, but are not limited to, diameter, height and pitch. As used herein, a "tier" is the part of a helix corresponding to one full thread of the spiral.

[0015] In certain embodiments, the present system can also be used in a manner of heat transfer to also heat or cook products, such as food products. The higher the velocity of the gas being employed to pass over the products, the greater the heat transfer experienced by the products.

[0016] In certain embodiments, a drum which moves the spiral conveyor belt cooperates with the spiral belt to create a bifurcated pathway for the gas, which pathway has a width equal to the width of the conveyor belt upon which the products are transported so that heat transfer gases are efficiently used.

[0017] In other embodiments, a central drum is not necessary. The spiral conveyor belt is self- stacking, with each tier sitting atop the tier below it. The self-stacking spiral conveyor belt may be driven by a rotating platform on which the bottom tier of the conveyor belt rests, or may be driven by modular drive mechanisms placed along the path of the self-stacking spiral conveyor belt. The self-stacking belt minimizes the height between tiers, and eliminates the necessity for bifurcated gas flow, resulting in efficiencies of size and cooling power consumption.

[0018] In the refrigeration system embodiments herein in which heat is transferred from a product to be refrigerated to a flowing refrigeration fluid, one mode of cooling the product to be refrigerated is forced convection. In forced convection, the heat transfer coefficient is a function of the flow velocity of the refrigeration fluid. Heat transfer for cooling objects also includes a factor that the higher the velocity o gas used to effect heat transfer, the greater the heat transfer rate.

[0019] Certain refrigeration fluids may be called "cryogens". As used in refrigeration, cryogen gas may be as cold as -250°F (-157°C), or as dictated by the minimum temperature at which the gas exists in its gaseous state. [0020] In certain embodiments, in which the spiral refrigeration system includes a double pass configuration, in addition to the efficiency benefits achieved by reducing disused regions, the size of the freezing system may be made significantly smaller because the refrigeration medium, such as a gas, is returned to the main blowers along the product pathway or in the product processing zone. In these embodiments, dedicated external return chambers and related ductwork are not necessary. This results in a savings in overall system cost. In addition, a lower amount of structural material is required to be cooled down which results in a secondary efficiency improvement.

[0021] In certain embodiments, a refrigeration system is provided, which includes: a housing having a top, a bottom, first and second opposed sides, and containing an atmosphere; a conveyor apparatus comprising a self-stacking, self-supported, spiral conveyor belt and a drive mechanism, wherein the conveyor belt includes a plurality of tiers and is at least partially disposed within the housing such that the conveyor belt can travel within the housing from the bottom towards the top of the housing or from the top towards the bottom of the housing; and an atmosphere circulation apparatus having at least one blower in communication with the atmosphere for circulating at least a portion of the atmosphere within the housing from proximate the first opposed side to the second opposed side and back towards the first opposed side, wherein the portion of the atmosphere circulated passes over the conveyor belt in a crossflow manner at least once.

[0022] The term "crossflow" is meant to describe the pattern of flow of the circulated atmosphere across and/or through the self-stacking conveyor belt; the circulated atmosphere passes through the refrigeration system substantially parallel to the top and/or bottom of the refrigeration system, and passes along the length of the refrigeration system at substantially similar speeds across the width of the refrigeration system.

[0023] The self-stacking, self-supported spiral conveyor belt may be operated in a continual state of movement, either ascending or descending, depending on the production line requirements. The following description refers to an ascending conveyor belt for ease of description, but the description should not be construed as limiting the conveyor belt to ascending movement. As the conveyor belt ascends through the heat transfer system, the sidewall typically engages with a conveyor belt structure above it and/or below it. Thus, the entire conveyor belt is stabilized due to the releasable engagement of the tiers of the conveyor belt. As the conveyor belt passes out of the heat transfer system, the uppermost tier of the belt disengages and lifts away from the tier beneath it, thereby leaving the spiral assembly, and continues to a take-up assembly which compensates for overall conveyor belt slack. The conveyor belt proceeds from the take-up assembly to a return section to be reintroduced into the heat transfer system at the bottom of the spiral assembly.

[0024] In certain embodiments, the height between each of the plurality of tiers of the spiral conveyor belt may be from about 3 inches to about 8 inches. In other embodiments, the height between each of the plurality of tiers of the spiral conveyor belt may be from about 3 inches to about 7 inches. In yet other embodiments, the height between each of the plurality of tiers of the spiral conveyor belt may be from about 3 inches to about 6 inches. In further embodiments, the height between each of the plurality of tiers of the spiral conveyor belt may be from about 4 inches to about 4.5 inches. Generally, the height between each tier will depend on the height of the product which is to be transported through the refrigeration system, with consideration being made to adequate gas flow to achieve acceptable heat transfer. A benefit of the present self-stacking conveyor belt is that the height between tiers may be drastically reduced as compared to conventional tiered belt systems traveling on fixed rails, allowing for increased cost- efficiency due to space savings and cooling gas savings.

[0025] In certain embodiments, the refrigeration system may comprise a product carrying component of the conveyor belt which is at least partially gas permeable. The product carrying component may comprise a horizontal surface on which products rest, and which convey the products through the refrigeration system.

[0026] In certain embodiments, the conveyor belt travels from the bottom of the housing towards the top of the housing, and a return channel is provided proximate to the top of the housing, wherein the conveyor belt is not present within the space of the return channel, such that the at least one blower forces the circulated atmosphere in a crossflow manner over the conveyor belt and the circulated atmosphere circulates back to the at least one blower via the return channel.

[0027] In certain embodiments, the conveyor belt travels from the top of the housing towards the bottom of the housing, and a return channel is provided proximate to the bottom of the housing, wherein the conveyor belt is not present within the space of the return channel, such that the at least one blower forces the circulated atmosphere in a crossflow manner over the conveyor belt and the circulated atmosphere circulates back to the at least one blower via the return channel.

[0028] In certain embodiments, the refrigeration system may comprise a product carrying component which is substantially gas impermeable.

[0029] In certain embodiments, the at least one blower forces the circulated atmosphere over the conveyor belt twice in a single cycle, such that the circulated atmosphere passes over upper tiers of the conveyor belt proximate to the top of the housing as the circulated atmosphere passes from the first opposing side to the second opposing side, and passes over lower tiers of the conveyor belt proximate to the bottom of the housing as the atmosphere passes from the second opposing side to the first opposing side, circulating back towards the at least one blower.

[0030] In certain embodiments, the at least one blower forces the circulated atmosphere over the conveyor belt twice in a single cycle, such that the circulated atmosphere passes over lower tiers of the conveyor belt proximate to the bottom of the housing as the circulated atmosphere passes from the first opposing side to the second opposing side, and passes over upper tiers of the conveyor belt proximate to the top of the housing as the atmosphere passes from the second opposing side to the first opposing side, circulating back towards the at least one blower. [0031] In certain embodiments, the driving mechanism may comprise a rotating platform. The rotating platform may be disposed at or within a bottom wall of the housing. Alternatively, the rotating platform may disposed within the housing.

[0032] In certain embodiments, the blower may be adapted to inject a cooling agent into the atmosphere within the housing. The cooling agent may be a cryogen, such as at least one of carbon dioxide, nitrogen, or air.

[0033] Referring to FIGS. 1 and 2, FIG. 1 shows a double pass configuration crossflow spiral heat transfer system 10. The system 10 is used to cool or freeze, or heat or bake products (not shown) such as food products. The system 10 includes a housing 12 with an internal cavity or chamber 14. The housing 12 is constructed of any suitable material, gas or substance for freezing or heating applications. By way of example, cryogenic gas (as low as but not limited to -250°F (-157°C)) from a blower chamber 20 is pressurized and passed around an exterior of a top half of a drum 40 and along and through spiral belt 50 to contact the products. A top portion of the belt 50 includes tiers 51. Gas flow is indicated by arrows 25. A baffle 30 separates upper 16 and lower 18 portions of the chamber 14 and prevents the gas from entering into bottom tiers 53 of the belt 50. The baffle 30 may be made from various materials that are substantially impervious to prevent the flow of gas. The gas 25 flows to a return chamber 60, where it turns and is diverted back through the lower portion 18 of the freezer (bottom tiers 53 of belt) and into an inlet of the blower chamber 20, where the gas 25 is recirculated by blower or fan 22.

[0034] The spiral belt 50 provides for a spiral pathway. The spiral pathway includes an upper pathway 52 of the tiers 51 within the upper portion 16; and a lower pathway 54 of the tiers 53 within the lower portion 18. The product is transported upon the tiers 51, 53 of the belt 50. The drum 40 drives the belt 50 along the spiral or helical path.

[0035] The baffle 30 separates the upper pathway 52 from the lower pathway 54, The baffle 30 works in conjunction with the drum 40 to create the upper pathway 52 and the lower pathway 54 to each have a width equal to a width of the belt 50. This is because gas flow 25 does not flow through the drum 40, but rather is bifurcated by the drum 40 as shown in FIG. 2 into two separate streams (discussed below) flowing about and exterior to the drum 40 and then into the return chamber 60. The baffle 30 is continuous around the drum 40, as shown more clearly in FIG. 2, and extends into the blower chamber 20 and the return chamber 60. In this manner of construction, the gas flow 25 is directed from the blower chamber 20 across and onto the product being transported on the tiers 51 of the belt 50 in the upper pathway 52, through the return chamber 60 and then back in counter flow to the lower pathway 54 for further contact with the product on the conveyor belt 50, whereupon the gas 25 flows to the blower chamber 20 for continuous circulation. Replenishment of fresh cryogen to the system 10 is provided to the blower chamber 20 via conduit 24. The conduit 24 is in communication with a source of cryogen (not shown) such as for example carbon dioxide (C0₂), nitrogen (N₂), etc. The conduit 24 may be disposed at other locations of the system 10 for introduction of cryogen (or heating fluid) thereto.

[0036] FIG. 1 shows the upper pathway 52 to be a helical path comprising a plurality of tiers such as for example three tiers 51 of the belt 50, and the lower pathway 56 to be a helical path comprising a plurality of tiers such as for example three tiers 53 of the belt 50, although the number of tiers is merely illustrative and not intended as a limitation. The upper pathway 52, the return chamber 60, the lower pathway 54, and the blower chamber 20 define a circulation loop for the gas 25. Blower means 22 to induce gas flow is provided, and such can be a fan, blower, compressor or any other suitable means. The blower means 22 is constructed and arranged for operation in or communication with the blower chamber 20.

[0037] In operation, and referring to FIGS. 1 and 2, a cryogen is provided to the blower chamber via conduit 24 and upon sufficient "charging" of the system 10 with the cryogen, the conduit is closed. Blower means, which as shown in FIG. 2 can be a pair of blowers or fans 20A and 20B, provide the necessary force to initiate and sustain a flow of the gas 25 into and along the upper pathway 52 such that the gas flow 25 contacts the tiers 51 of the conveyor belt 50 upon which the product is being transported. The conveyor belt 50 is porous, i.e. can be of mesh construction or grid-like construction, to thereby facilitate the gas 25 flowing between and among the tiers 51 of the conveyor belt 50 in the upper pathway 52. The gas flow in the upper pathway 52 is prevented from communicating with the lower pathway 54 by virtue of the disposition of the baffle 30 in the chamber 14 of the housing 12. The gas flow 25 in the upper pathway 52 is in counter- flow to the gas flow 25 in the lower pathway 54.

[0038] As shown in FIG. 2, the drum 40 is disposed substantially at the center of the chamber 14 with the baffle 30 extending in the chamber 14 around the drum 40. The drum can be hollow or solid, but an exterior wall 57 of the drum 40 is impervious to the gas flow 25. The gas under force exerted by the blowers 20 A, 20B is directed in the return chamber 60 downward away from the upper pathway 52 into the lower pathway 54 to subsequently contact food product on the tiers 53 of the conveyor belt 50. It should be noted that the baffle 30, in an embodiment where the blowers 20A and 20B are disposed at the same side of the housing 12, may be angled slightly downward toward the bottom of the housing 12, as shown in FIG. 1, to facilitate movement of the gas flow to the return chamber 60 and back through the lower pathway 54 to the blower chamber 20.

[0039] In effect, the product is subjected to a double pass flow of the gas 25. The cryogen gas flow 25 is restricted for flow across a width of the tiers 51, 53 of the conveyor belt 50, such that none of the cryogen gas is wasted on heat transfer at unnecessary portions of the freezer system 10.

[0040] The construction and operation of the embodiment shown in FIGS. 1 and 2 uses only approximately 50% of the amount of cryogen flow as a single pass refrigeration system would require, due to the arrangement of the baffle 30 and its cooperation with the drum 40, segregation of the upper pathway 52 and lower pathway 54, and the recirculation of the gas flow 25 between and among the blower chamber 20 and the return chamber 60. This dual-pass configuration of the spiral refrigeration system 10 also requires less power, whereby the power reduction leads to additional operating efficiencies. Initial testing has shown a 35% reduction in overall power necessary in order to power the system 10, with a cryogen efficiency improvement of at least 15% less use of the gas 25 as compared to single pass systems.

[0041] In the crossflow spiral refrigeration system 10 of FIG. 1, the refrigeration medium makes two passes through the product pathway, once in the upper pathway 52, and once in the lower pathway 54. In the system 10 shown, the amount of refrigeration medium that flows through the upper pathway 52 is the same as the amount that flows through the lower pathway 54. The present system 10 provides for an even gas flow and velocity in the upper and lower pathways 52, 54. The system 10 is constructed and arranged to provide for continuous, uniform passes of the cooling medium over the product on the belt 50. Alternatively, system 10 as a heat transfer system provides for the continuous, uniform passing of a heating or cooking gas over the product on the belt 50.

[0042] Thus, the two-pass configuration of the present system 10 may require only about 50% of the conventional airflow used in conventional airflow schemes, such as one-pass flow configurations.

[0043] In addition to the operational efficiency benefits achieved by the system 10, the size of the freezing system 10 may be made significantly smaller because the gas is returned to the blowers 20A, 20B through the upper and lower pathways. Separate gas return chambers and ductwork are not necessary, thereby providing for a smaller "footprint" for the system 10. This results in a significant savings in overall system cost.

[0044] FIG. 2 illustrates a cross-sectional plan view of the embodiment of a crossflow spiral refrigeration system 10 in FIG. 1.

[0045] As shown in FIG. 2, the gas flow 25 enters the upper pathway 52 and is bi urcated by the drum 40 into separate branches 56, 58 of gas flow to flow around the drum 40. Subsequently, the branches 56, 58 reunite and flow into the return chamber 60. This also occurs in the lower pathway 54 as well. That is, the returning gas flow 25 from the return chamber 60 is prevented from returning to the upper pathway 54 by the baffle 30. The gas flow 25 is similarly bifurcated by the drum 40 into separate branches in the lower pathway 54 (which would correspond to the branches 56, 58 in the upper pathway 52) as it is returned to the blower chamber 20. The cross-sectional width of branch 56 is equal to the width of the branch 58, and the sum of the cross-sectional volumes of branch 56 and 58 is equal to the cross- sectional volume of the original upper pathway 52. The width of the branch 56 is equal to the width of the tier 51 of the belt 50, and the width of the branch 58 is equal to the width of the tier 51 of the belt. Similar dimensions exist between and among the tiers 53 of the belt 50 and the related branches in the lower pathway 54.

[0046] FIG. 3 shows another embodiment, wherein a double pass configuration of the present spiral refrigeration system is shown generally at 110 and includes two blower chambers 120, 170. In this configuration, higher velocities along the belt result in higher heat transfer coefficients for the product, whether the product is being heated or cooled.

[0047] The system 110 shown in FIG. 3 includes a housing 112 having an internal space or chamber 114 therein. The system 1 10 has many features similar to the system 10 and operates in a similar manner.

[0048] Disposed within the space 114 is a drum 140 about which a spiral conveyor belt 150 is engaged, the belt 150 being driven along the spiral or helical path by the drum 140. The drum 140 is impervious to fluid flow and bifurcates the gas flow 125 similarly to that which occurs with respect to the embodiment of FIGS. 1 and 2. The conveyor belt 150 transports products (not shown), such as food products along the internal chamber 114 for cooling and/or freezing by the system 110. Similar to the embodiment discussed above with respect to FIGS. 1 and 2, the embodiment in FIG. 3 is also a heat transfer system and can be used to heat and cook products, as well as freeze products.

[0049] The internal chamber 1 14 consists of an upper portion 116 and a lower portion 118. The upper portion 1 16 and lower portion 1 18 are segregated from each other by a baffle 130 which extends along the internal chamber 114 of the housing 1 12. The upper portion 116 of the internal chamber 114 contains the upper pathway 152, while the lower portion 118 of the internal chamber 1 14 contains the lower pathway 154. The conveyor belt and its tiers 151, 153 move between the upper and lower pathways 152, 154. [0050] Disposed in the upper portion 116 of the internal chamber 114 is a blower or fan 122 A, while disposed at the lower portion 118 of the internal chamber 1 14 is another blower or fan 122B. Fans 122A, 122B may be arranged at different sides of the housing 1 12, such as at opposed sides of the housing 112. In addition, one of the fans, such as the fan 122A, is disposed in the upper portion 1 16, while the other blower such as the fan 122B is disposed in the lower portion 118. The baffle 130 surrounds the drum 140 and prevents fluid flow 125 between and among the upper portion 116 and the lower portion 118, except for areas of the baffle 130 shown generally at 131 and 132. The areas 131, 132 are those areas permitting gas flow 125 to occur between the lower portion 118 and the upper portion 116. This can be as a result of the construction of the baffle 130 extending up to only that point in the interior space 114 where the baffle meets the fans 122A, 122B, or apertures (not shown) may be provided in the baffle 130 to enable the gas flow 125 to be drawn from the lower portion into the upper portion via the fan 122 A, and from the upper portion 116 into the lower portion 118 via the fan 122B. In either arrangement there is provided the continuous circulatory effect between and among the upper and lower portions 116, 118.

[0051] The conveyor belt 150 is arranged to extend between the lower portion 118 and the upper portion 1 16. At least one and preferably a plurality of the tiers 151 of the belt 150 are disposed at any given time in the upper portion 1 16. At least one and preferably a plurality of the tiers 153 of the belt 150 are disposed in the lower portion 118 at any given time.

[0052] As shown in FIG. 3, movement of the belt 150 causes the tiers 151, 153 to transport the product between the upper portion 116 and the lower portion 118, but in any event the gas flow 125 assures that the products receive a continuous, uniform dual pass flow of the cryogen gas as the products are transported by the belt 150 between and among the portions 116, 118. [0053] Although the perspective of FIG. 3 shows a pair of fans 122A, 122B, it should be understood that owing to said perspective there may be two or more fans at each opposed side of the housing 1 12.

[0054] Conduits 124, 126 are in communication with the blower chambers 120, 170 to "charge" the system 110 with a cooling or heating fluid as necessary. The conduits 124, 126 are connected to a source (not shown) of cooling or heating fluid and may be in communication with other areas of the chamber 1 14.

[0055] The system 110 shown in FIG. 3, due to the blower arrangement 122 A, 122B, does not necessitate a grade or angle of the conveyor belt 150 to be other than at the horizontal with respect to the housing 112, although such a grade or angle can be employed if required for a particular processing application.

[0056] In the embodiments of FIGS. 1-3, the fans 22, 20A, 20B, 122A, 122B exert a sufficient force of the fluid flow 25, 125 such that same does not displace the products from the tiers 51, 53, 151, 153.

[0057] In the embodiments shown in FIGS. 1-3, the systems 10, 110 function as heat transfer systems. That is, in effect, these heat transfer systems 10, 110 can be employed to heat or cook products, such as food objects, just as the systems 10, 110 can be employed to cool and/or freeze products as discussed above. In other words, instead of the gas flow 25 being a cryogen for example, said gas flow 25 may consist of high temperature air or other gases to warm, heat or cook products, such as food products being transported for processing in the systems 10, 110. Accordingly, the subject matter of the present invention is not limited to cooling and freezing, but rather can be employed to heat or cook products such as food products.

[0058] FIG. 4 shows an embodiment of a single pass crossflow spiral heat transfer system 410 including a housing 412 with an internal chamber 414. At least one blower 422 is disposed within the housing 412 to circulate an atmosphere 425 within the housing 412. The at least one blower 422 is disposed in a blower chamber 420 of the internal chamber 414, and is powered by at least one motor 423 which is disposed external to the housing 412. The atmosphere 425 is circulated by the at least one blower 422 from the blower chamber 420, through product chamber 416, return chamber 460 and recycle chamber 418, after which the circulated atmosphere 425 is recycled by the at least one blower 422. A baffle 430 separates the product chamber 416 from the recycle chamber 418, such that the circulating atmosphere 425 follows the designated path. Recycle chamber 418 is disposed substantially above the product chamber 416.

[0059] A self-stacking, self-supporting spiral conveyor belt 450 is disposed within the product chamber 416, such that the circulating atmosphere 425 passes over products (not shown) disposed on the conveyor belt 450 in order to create a heat transfer relationship between the atmosphere 425 and the products. The conveyor belt 450 rests on a rotating platform 440 which is disposed at the bottom wall of the housing 412. The rotating platform 440 provides the drive force necessary to move the conveyor belt 450 through the system 410. The conveyor belt 450 includes tiers 451 which may be spaced apart from each other according to and to accommodate the product to be processed by the system 410. The self-stacking conveyor belt 450 allows for minimal heights between the tiers 451, which in turn allows for increased efficiency, even in the single-pass arrangement of FIG. 4, as discussed in more detail below.

[0060] FIG. 5 shows another embodiment of a single pass crossflow spiral heat transfer system 510 including a housing 512 with an internal chamber 514. At least one blower 522 is disposed within the housing 512 to circulate an atmosphere 525 within the housing 512. The at least one blower 522 is disposed in a blower chamber 520 of the internal chamber 514, and is powered by at least one motor 523 which is disposed external to the housing 512. The atmosphere 525 is circulated by the at least one blower 522 from the blower chamber 520, through product chamber 516, return chamber 560 and recycle chamber 18, after which the circulated atmosphere 525 is recycled by the at least one blower 522. A baffle 530 separates the product chamber 516 from the recycle chamber 518, such that the circulating atmosphere 525 follows the designated path. Recycle chamber 518 is disposed substantially below the product chamber 516. [0061] A self-stacking, self-supporting spiral conveyor belt 550 is disposed within the product chamber 516, such that the circulating atmosphere 525 passes over products (not shown) disposed on the conveyor belt 550 in order to create a heat transfer relationship between the atmosphere 525 and the products. The conveyor belt 550 rests on a rotating platform 540 have a supporting surface which is disposed for coaction with the baffle 530. The rotating platform 540 provides the drive force necessary to move the conveyor belt 550 through the system 510. The conveyor belt 550 includes tiers 551 which may be spaced apart from each other according to and to accommodate the product to be processed by the system 510. The self-stacking conveyor belt 550 allows for minimal heights between the tiers 551, which in turn allows for increased efficiency, even in the single-pass arrangement of FIG. 5, as discussed in more detail below.

[0062] FIG. 6 shows an embodiment of a double pass crossflow spiral heat transfer system 610 including a housing 612 with an internal chamber 614. At least one blower 622 is disposed within the housing 612 to circulate an atmosphere 625 within the housing 612. The at least one blower 622 is disposed in a blower chamber 620 of the internal chamber 614, and is powered by at least one motor 623 which is disposed external to the housing 612. The atmosphere 625 is circulated by the at least one blower 622 from the blower chamber 620, through upper product chamber 616, return chamber 660 and lower product chamber 618, after which the circulated atmosphere 625 is recycled by the at least one blower 622. A baffle 630 separates the upper product chamber 616 from the lower product chamber 618, such that the circulating atmosphere 625 follows the designated path.

[0063] A self-stacking, self-supporting spiral conveyor belt 650 is disposed within the product chamber 616, such that the circulating atmosphere 625 first passes over products (not shown) disposed on the upper tiers 6 1 of the conveyor belt 650, then passes through return chamber 660 and passes over products disposed on the lower tiers 653 in order to create a double-pass heat transfer relationship between the atmosphere 625 and the products. The conveyor belt 650 rests on a rotating platform 640 which is disposed at the bottom of the housing 612. The rotating platform 640 provides the drive force necessary to move the conveyor belt 650 through the system 610. The tiers 651, 653 may be spaced apart from each other according to and to accommodate the product to be processed by the system 610. The self-stacking conveyor belt 650 allows for minimal heights between the tiers 651. The double-pass arrangement of FIG. 6 allows for even further increases in efficiency compared to the systems 410,510 of FIGS. 4 and 5, respectively, as discussed in more detail below.

[0064] The following examples are set forth merely to further illustrate the subject heat transfer system. The illustrative examples should not be construed as limiting the heat transfer system in any manner.

[0065] A double-pass heat transfer system similar to the system described in FIGS. 1 and

2 has a 7 inch spacing between each tier, with a total of 7 tiers, and utilizes two fans to provide a 2000 ft/min velocity of atmosphere circulation. The system has a total flow width of 86 inches and a total flow height of 73 inches. Therefore, the total flow provided by the system is 43,597 ft /min, and each fan provides 21,799 ft /min. The power required by the system is 4.3 kW.

[0066] A double-pass heat transfer system similar to the system described in FIG 6 has a

3 inch spacing between each tier, with a total of 7 tiers, and utilizes two fans to provide a 2000 ft/min velocity of atmosphere circulation. The system has a total flow width of 86 inches and a total flow height of 45 inches. Therefore, the total flow provided by the system is 26,875 ftVmin, and each fan provides 13,438 ft³/min. The power required by the system is 2.6 kW. Thus, because of the difference in height of the tiers, the power consumption is significantly reduced.

[0067] While the present subject matter has been described above in connection with illustrative embodiments, as shown in the various Figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiments for performing the same function without deviating therefrom. Further, all embodiments disclosed are not necessarily in the alternative, as various embodiments may be combined to provide the desired characteristics. Variations can be made without departing from the spirit and scope of the invention. Therefore, the crossflow spiral heat transfer system should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the attached claims.

Claims

CLAIMS What is claimed is:

1. A refrigeration system, comprising:

a housing having a top, a bottom, first and second opposed sides, and containing an atmosphere;

a conveyor apparatus comprising a self-stacking, self-supported, spiral conveyor belt and a drive mechanism, wherein the conveyor belt comprises a plurality of tiers and is at least partially disposed within the housing such that the conveyor belt can travel within the housing from the bottom towards the top of the housing or from the top towards the bottom of the housing; and

an atmosphere circulation apparatus comprising at least one blower in communication with the atmosphere for circulating at least a portion of the atmosphere within the housing from proximate the first opposed side to the second opposed side and back towards the first opposed side, wherein the portion of the atmosphere circulated passes over the conveyor belt in a crossflow manner at least once.

2. The refrigeration system of claim 1, wherein a height between each one of the plurality of tiers is from about 3 inches to about 8 inches.

3. The refrigeration system of claim 1, wherein the conveyor belt comprises a product carrying surface being at least partially gas permeable.

4. The refrigeration system of claim 3, wherein the conveyor belt is constructed and arranged to travel from the bottom towards the top of the housing, and further comprising a return channel disposed proximate the top of the housing, wherein the conveyor belt does not extend within the return channel, such that the at least one blower forces the atmosphere circulated in a crossflow manner over the conveyor belt and through the return channel back to the at least one blower.

5. The refrigeration system of claim 3, wherein the conveyor belt is constructed and arranged to travel from the top towards the bottom of the housing, and further comprising a return channel disposed proximate the bottom of the housing, wherein the conveyor belt does not extend within the return channel, such that the at least one blower forces the atmosphere circulated in a crossflow manner over the conveyor belt and through the return channel back to the at least one blower.

6. The refrigeration system of claim 1, wherein the conveyor belt comprises a product carrying surface being substantially gas impermeable.

7. The refrigeration system of claim 6, wherein the at least one blower forces the atmosphere circulated over the conveyor belt twice in a single cycle, such that the circulated atmosphere passes over upper tiers of the conveyor belt proximate the top of the housing as the circulated atmosphere passes from the first opposed side to the second opposed side, and passes over lower tiers of the conveyor belt proximate the bottom of the housing as the atmosphere passes from the second opposed side to the first opposed side, circulating back towards the at least one blower.

8. The refrigeration system of claim 6, wherein the at least one blower forces the atmosphere circulated over the conveyor belt twice in a single cycle, such that the circulated atmosphere passes over lower tiers of the conveyor belt proximate the bottom of the housing as the atmosphere circulated passes from the first opposed side to the second opposed side, and passes over upper tiers of the conveyor belt proximate the top of the housing as the atmosphere passes from the second opposed side to the first opposed side, circulating back towards the at least one blower.

9. The refrigeration system of claim 1, wherein the drive mechanism comprises a rotating platform.

10. The refrigeration system of claim 9, wherein the rotating platform is disposed at the bottom of the housing.

11. The refrigeration system of claim 9, wherein the rotating platform is disposed within the housing.

12. The refrigeration system of claim 1, wherein the at least one blower is constructed and arranged to provide a coolmg substance to the atmosphere within the housing.

13. The refrigeration system of claim 12, wherein the cooling substance comprises a cryogen.

14. The refrigeration system of claim 13, wherein the cryogen comprises at least one of carbon dioxide, nitrogen or air.

15. The refrigeration system of claim 1, wherein the at least one blower is disposed within the housing.