Abstract:
A method for reducing a temperature of a product in a freezer includes providing a product to a chamber of the freezer; dividing a portion of the chamber disposed between a pair of baffle assemblies in the freezer into an intake zone and an outflow zone; moving each baffle assembly of the pair of baffle assemblies in the chamber 90° degrees out of phase with each other for directing a gas flow in the chamber; oscillating the gas flow within the chamber between the intake zone and the outflow zone during the moving the pair of baffle assemblies; injecting a cryogen substance into the chamber for cooling the gas flow; and contacting the product with the cooling gas flow.

Description:
BACKGROUND 
     The present embodiments relate to apparatus and methods for providing and controlling air flow and heat transfer across products in freezing systems for example, used with food products. 
     Known freezers have a fan or a plurality of fans to provide a convective airflow environment to accelerate the freezing rate of products, such as food products, being processed in the freezer. Fans require electrical energy to operate and contribute the thermal loads to the freezing processes which reduces the overall efficiency of the freezer. Therefore, the use of fewer fans is advantageous. 
     It is also know to pulse or oscillate a flow of gas across the surface of a product for increasing convective surface heat transfer co-efficients. Such a pulsing or oscillating flow of gas can require equipment that is expensive to maintain and more difficult to operate under low temperatures. Sanitation may also be more problematic with such systems. 
     However, using a single fan assembly to create the same oscillating or pulsating flow is not known, would be less expensive to implement and would reduce sanitary problems for which the food industry is particularly concerned. 
     The present inventive embodiments provide a freezer which provides the oscillating or pulsing flow of the gas with a single fan assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present inventive embodiments, reference may be had to the following description of the embodiments taken in conjunction with the drawing figures, of which: 
         FIG. 1  shows a cross-section of a baffle controlled oscillating flow freezer in a first position constructed to provide an oscillating airflow according to the present embodiments; 
         FIG. 2  shows the freezer embodiment along line  2 - 2  in  FIG. 1 ; 
         FIG. 3  shows a cross-section of the baffle controlled oscillating flow freezer in a second position constructed to provide an oscillating airflow according to the present embodiments; 
         FIG. 4  shows the freezer embodiment along line  4 - 4  in  FIG. 3 ; and 
         FIG. 5  shows a cross-section of the oscillating flow provided by the freezer of  FIGS. 1 and 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , a freezer apparatus, such as a tunnel freezer, is shown generally at  10 , which is constructed to provide an oscillating flow of cryogenic gas to products to be chilled or frozen. The oscillating flow may in one embodiment operate repetitiously at high frequency. The cryogenic gas may be carbon dioxide (CO 2 ) or nitrogen (N 2 ), thereby permitting the apparatus  10  to be used with for example food products, as discussed below. 
     As used herein, “oscillating flow” refers to the flow of gas moving or traveling back and forth between two points regardless of the manner, number of repetitions or frequency of repetitions by which the oscillating flow is implemented. 
     The apparatus  10  includes a housing  12  in which a space  14  is provided for providing a chilling or freezing convective gas flow  16  to correspondingly chill or freeze products  18 , such as food products, transported through a processing region  15  of the space  14  in the housing. The space  14 , and the processing region  15  are provided by an interior wall  17  or duct disposed within the housing  12  as shown for example in  FIG. 1 . The housing  12  also includes an inlet  20  and an outlet  22 . An inlet skirt  24  or flap is provided at the inlet  20 , while an outlet skirt  26  or flap is provided at the outlet  22  to retain the gas flow  16  within the region  15 . A transport apparatus  28 , such as a conveyor belt for example, is disposed for operation to transport the products  18  from the net  20  through the region  15  to the outlet  22 . 
     A baffle  30  is disposed in the housing  12  beneath an upper tier  29  or surface of the conveyor belt  28 . The baffle  30  may be of solid construction. An inlet exhaust flue  32  is disposed proximate the inlet  20  of the housing  12 . An outlet exhaust flue  34  is disposed proximate the outlet  22  of the housing  12 . A cross-sectional area of the processing region  15  includes the space of the processing region above the product  18 , and below the upper tier  29  of the conveyor belt  28  and to the sides of the belt as shown also with respect to  FIG. 2 . This cross-sectional area is minimized by a wall portion  19  of the interior wall  17 , and the wall portion  19  position assists to maximize airflow velocity and concurrently minimize volumetric flow through the processing region  15 . The portion  19  of the interior wall  17  and the baffle  30  co-act to prevent “dead space” above and below said portion and the baffle from interfering with and diluting the osculating gas flow  16 . This construction and arrangement provides for a more intense and effective gas flow across the product  18 , and minimizes the cross sectional area of the region  15  to reduce total volumetric flow requirements for the process. A vertical distance “D” or height between the wall portion  19  and the baffle  30  corresponds directly to the cross-sectional air flow area in the freezing chamber. A width “W” of the conveyor belt  28  is therefore fixed. It is most efficient to operate the apparatus  10  with a minimum acceptable height D. The height D is therefore dependent upon a height of the product  18  being transported through the processing region  15 . When the cross-sectional area of the processing region  15  is minimized, a velocity of the gas flow  16  on the surface of the product  18  can be increased with a constant volumetric flow. 
     A pair of baffle assemblies  36 , 38  are disposed in the space  14 . As shown in  FIGS. 1 and 2 , the assemblies  36 , 38  may be disposed at opposed sides of the housing  12 . Each of the assemblies  36 , 38  includes a respective actuator  40 , 42  which may be disposed at an exterior of the housing  12 . The baffle assembly  36  includes a shaft  44  extending from the actuator  40  into the space  14 . A pair of baffles  46 , 48  are mounted to the shaft  44  90° out of phase with each other. That is, the baffle  46 , which can be the upper baffle, is mounted to the shaft  44  90° out of phase from the baffle  48 , which can be the lower baffle. The baffles  46 , 48  rotate in their respective fixed positions with rotation of the shaft  44 . In this manner of construction, the baffles  46 , 48  rotate in unison with each other. The baffles  46 , 48  may be rectangular-shaped for example, or perhaps shaped like paddles, and may be constructed of plastic or stainless steel. When the baffles  46 , 48  are rotated by the shaft  44 , at least one of the baffles will be disposed in the space  14  to block or intercept the gas flow  16  in the space. A bearing  50  is mounted to an end of the shaft  44  opposed to the actuator  40  at the interior wall  17  as shown in  FIG. 1 . 
     The baffle assembly  38  includes a shaft  52  extending from the actuator  42  into the space  14 . A pair of baffles  54 , 56  are mounted to the shaft  52  90° out of phase with each other. That is, the baffle  54 , which can be the upper baffle, is mounted to the shaft  52  90° out of phase from the baffle  56 , which can be the lower baffle. The baffles  54 , 56  rotate in their respective fixed positions with rotation of the shaft  52 . In this manner of construction, the baffles  54 , 56  rotate in unison with each other. The baffles  54 , 56  may be rectangular-shaped for example, or perhaps shaped like paddles, and may be constructed of plastic or stainless steel. When the baffles  54 , 56  are rotated by the shaft  52 , at least one of the baffles will be disposed in the space  14  to block or interrupt the gas flow  16  in the space. A bearing  58  is mounted to an end of the shaft  52  opposed to the actuator  42  at the interior wall  17  as shown in  FIG. 1 . 
     A fan  60  or blower is mounted in the space  14  between the baffle assemblies  36 , 38 . The fan  60  is mounted for rotation on a shaft  61  which is connected to a motor  63  shown disposed external to the housing  12 . 
     A pair of flow divider plates  62 , 64  are mounted in the space  14  between the baffle assemblies  36 , 38  as shown for example in  FIG. 1 . Each of the flow dividers  62 , 64  is constructed as a solid member of plate through which a corresponding one of the shafts  44 , 52  pass. As shown in  FIG. 1 , such construction results in the baffles  46 , 54  being the upper baffles (above the dividers  62 , 64 ), while the baffles  48 , 56  are the lower baffles (below the dividers  62 , 64 ). The dividers  62 , 64  each extend to the blower  60  so that there is provided an intake zone  66  below the dividers  62 , 64 , and an out flow zone  68  above the dividers as shown in  FIG. 1 , for a purpose to be described hereinafter. The baffles  46 , 48  rotate to either impede or allow flow  16 , 21  into the zones  66 , 68 . For example, one hundred percent (100%) of the flow  16  in space  14  is then either negative pressure (baffle  48  open, baffle  46  closed) or positive pressure (baffle  48  closed, baffle  46  open). A corresponding opposite arrangement would occur simultaneously regarding the baffle assembly  38  and the flow  21  with respect to the baffles  54 , 56 . The space  14  is therefore divided into two sections near the blower  60  by the positioning of the flow dividers  62 , 64 , as shown for example in  FIGS. 1 and 3 . 
     The flow dividers  62 , 64  and the interior wall  17  or ductwork may be of solid construction to thereby prevent aft or gas flow therethrough. 
     A liquid cryogen provided, CO 2  or N 2 , will usually phase change into a gaseous-solid phrase when injected into the processing region  15 . A pipe  70  for delivering the cryogen to the apparatus  10  has a first end connected to a manifold  72  from which at least one or a plurality of nozzles  74  are in communication therewith. The manifold  72  may be disposed in the region  15 . The nozzles  74  provide a cryogen spray  76  or jet into the processing region  15  to freeze at least a surface of the products  18 . An opposite end of the pipe  70  is connected to a source  71  of liquid cryogen. The pipe  70  includes a control valve  78  for controlling an amount of the liquid cryogen to be introduced through to the manifold  72 . 
     The wall portion  19  and the baffle  30  coact to provide the processing region  15  within the space  14 . The cross section of the region  15  is kept to as small a volume as possible in order to provide for increased velocity of a cryogen airflow  80  across the products  18 , which in turn provides for increased heat transfer to the products. 
     An exhaust pipe  82  is in communication with the space proximate the outlet  22 . The exhaust pipe includes a flapper  84  disposed therein for movement for a purpose to be described below. 
     The housing  12  may be for example 3-20 meters in length and constructed as a tunnel freezer. The inlet and outlet skirts  24 , 26  can be constructed of rubber, plastic or stainless steel and are adjustable depending upon the dimensions of the products  18  entering and being discharged from the processing region  15 . 
     The apparatus  10  oscillates cold gas across the product  18 , such as a food product, during a freezing process. Referring initially to  FIGS. 1-2 , the conveyor belt  28  transports for example food products  18  from the inlet  20  to the processing region  15  of the apparatus  10 . The cryogenic injection assembly is arranged such that the manifold  72  is located in the processing region  15 , but could for example be disposed more closely to the inlet  20  than to the outlet  22 . The manifold will have at least one or alternatively a plurality of nozzles  74 . The products  18  being transported by the conveyor belt  28  are exposed to the cryogenic spray  76  as they pass in proximity to the nozzles  74 . However, the gas flow  80  provides further heat transfer effect to the products  18  as described below. The products exit the processing region  15  of the apparatus  10  at the outlet  22 . 
     The baffle assemblies  36 , 38  work in unison, and can be rotated in unison approximately 90 degrees out of phase with each other. Referring still to  FIGS. 1-2 , a convective gas flow  16  becomes the cryogen air flow  80  upon exposure to the spray  76  emitted by the at least one nozzle  74 . The food products  18  are contacted by the cryogen spray  76  and at least crust frozen as they proceed along the processing region  15  to the outlet  22 . As shown in FIGS.  1  and  2 , the convective gas flow  16  and the cryogen air flow  80  are in a circuitous path through the space  14  of the apparatus  10 . 
     The baffle assembly  36  is arranged such that the upper baffle  46  blocks a portion of the space  14 , while the lower baffle  48  is positioned such that the convective gas flow  16  is not impeded by the baffle  48  and is drawn into the intake zone  66  by the pull of the fan  60 . The baffle assembly  38  is positioned 90° out of phase from the baffle assembly  36 . That is, the baffle assembly  38  has the upper baffle  54  aligned in the same direction as the baffle  48 , while the lower baffle  56  is aligned in the same direction as the upper baffle  46  of the baffle assembly  36 . Such alignment provides for the convective gas flow  16  to pass by the lower baffle  48  into the intake zone  66  to be drawn by the fan  60  into the outflow zone  68 , and thereafter proceed from the outflow zone  68  to bypass the upper baffle  54  (but blocked by the lower baffle  56 ) into the processing region  15  where it chills the food product  18  and is recharged with the cryogen spray  76 . 
     Referring to  FIGS. 3-4 , the convective gas flow has been reversed by the baffle assemblies  36 , 38  and is shown generally at  21 . The direction of the convective gas flow  21  is counterclockwise to the clockwise direction of gas flow  16  of  FIGS. 1-2 . Such is accomplished by the baffle assemblies  36 , 38  being rotated 90° such that the convective gas flow  21  is drawn past the lower baffle  56 , because the upper baffle  54  blocks the space  14 , and into the intake zone  66  by the fan  60 . The convective gas flow  21  is drawn from the intake zone  66  through the fan and exhausted into the outflow zone  68  where it passes by the upper baffle  46 , because the lower baffle  48  has now been pivoted to close the space  14 . Even though the fan  60  continues to draw the convective gas flow  21  as it would the gas flow  16 , because the baffle assemblies  36 , 38  have been pivoted 90° with respect to each other the circulation of the gas flows  16 , 21  has been reversed, as shown comparing  FIGS. 1 and 3 . 
     The positioning of the flow dividers  62 , 64  defines the distinct zones of the intake zone  66  and the outflow zone  68  so that movement of the baffle assemblies  36 , 38  can effect the circulation in the space  14  without having to change the rotary direction of the fan  60 . 
     The inlet skirt  24  and the outlet skirt  26  are in the closed position as shown in  FIGS. 1 and 3  to contain the chilling or freezing atmosphere within the space  14 . To the extent any of the convective gas flow  16 , 21  escapes through the inlet  20  and/or the outlet  22 , the inlet exhaust flue  32  and the outlet exhaust flue  34  direct the escaping gas away from the apparatus and perhaps to a location remote from the area where the apparatus  10  and operational personnel are located. 
     Referring now to  FIG. 5 , oscillation of the convective gas flow  16 , 21  is shown. That is, periodically pivoting the baffle assemblies  35 , 38  in unison can operate the convective gas flows  16 , 21  in clockwise and counterclockwise directions, respectively. For example, the baffle assemblies  36 , 38  can be maintained in their position for a period of time of for example 0.5-10 seconds, after which the baffle assemblies  36 , 38  are rotated in unison, by for example known timers or controllers (not shown) which will alter the gas flow to be in an opposite direction. 
     Even though the manifold  72  for the spray  76  of cryogen is shown disposed closer to the inlet  20  than the outlet  22 , use of the exhaust pipe  82  can be used to control an overall mass of the cryogen gas in the processing region  15 . That is, as the baffle assemblies  36 , 38  pivot in unison after a select time period, the flapper  84  in the exhaust pipe  82  can be opened at select periods of time to exhaust some of the cryogen airflow  80  in the space  14  such that a colder mass of the cryogen atmosphere in the space  15  is drawn from the inlet  20  to the outlet  22 . In this manner of operation, a specific area of the processing region  15  can retain a large mass of colder cryogen gas flow to freeze the products  18 . 
     In addition, as the overall flow of the gas mass in the processing region  15  is directed to the outlet  22 , the convective gas flows  16 , 21  warm during the freezing process which thereby provides a temperature gradient in the processing region  15 . With the baffle assemblies  36 , 38  being operated by for example electronic controls (not shown), a temperature gradient can be entered into an input for the electronic control system (not shown) for operating the baffle assemblies  36 , 38  at their most efficient setting depending upon the type of products  18 , the amount of the products and the extent to which the products are to be frozen. That is, the temperature gradient is established from the inlet  20  to the outlet  22  by alternating a duration of time that the baffle assemblies  36 , 38  are actuated. For example, a position shown of the apparatus  10  in  FIG. 3  could be retained for a period of time of two (2) seconds, and the position of the apparatus demonstrated in  FIG. 1  can be held for a period of time of 1.5 seconds. This allows for a net positive volumetric flow of gas to be moved from the inlet  20  to the outlet  22 . In certain instances, it may be necessary to reverse the aforementioned process and move a flow of gas to the inlet  20  of the apparatus  10 . In such an instance, the manifold  72  with its at least one nozzle  74  would be positioned closer to the outlet  22  of the apparatus, while another exhaust with a flapper would be added at the inlet  20  of the apparatus. 
     As shown in  FIGS. 1-4 , as the baffle assemblies  36 , 38  are rotated 90° with respect to each other, the baffles  46 , 48  and  54 , 56  coact with the flow dividers  62 , 64  to adjust and control the gas flow  16  through the intake zone  66  and the outflow zone  68 . By operating the baffle assemblies  36 , 38  90° out of phase and always moving same in unison, the intake zone  66  provides a suction area, while the outflow zone  68  provides a discharge area for the space  14 . The baffles  46 , 48  of the baffle assembly  36  and the baffles  54 , 56  of the baffle assembly  38  are shown in broken lines in  FIG. 5  to represent movement of the baffles and also that they are in different opposed positions depending upon operation of the apparatus  10 . 
     A temperature gradient may also be provided by the apparatus  10  and the method employed by the apparatus. To establish the temperature gradient, the stationary position time of the baffle assemblies  36 , 38  is increased, thereby puffing more gas in one direction. When the gas is forced to the outlet  22  it can then be bled from the processing region  15  through the exhaust pipe  82 . 
     The apparatus  10  and method of the present inventive embodiments provides for increased efficiency for using cryogen to chill or freeze the products  18 . The apparatus  10 , being able to operate at specific temperature gradients, will also contribute to increased processing efficiencies. There are fewer moving parts and therefore less maintenance for the apparatus  10 . 
     It will be understood that the embodiments described herein are merely exemplary, and that one skilled in the art may make variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as described and claimed herein. Further, all embodiments disclosed are not necessarily in the alternative, as various embodiments of the invention may be combined to provide the desired result.