US20100162727A1

US20100162727A1 - Freezer with pulse flow generator

Info

Publication number: US20100162727A1
Application number: US12/347,382
Authority: US
Inventors: Michael D. Newman
Original assignee: Linde Inc
Current assignee: Linde GmbH; Messer LLC
Priority date: 2008-12-31
Filing date: 2008-12-31
Publication date: 2010-07-01

Abstract

An apparatus and process for reducing temperature of food products on a conveyor disposed within a chamber including transporting the food products on the conveyor moving in a direction within the chamber; introducing a mixture of a gas and solid or liquid cryogen into the chamber; and pulsing a turbulent flow of the mixture of gas and solid or liquid cryogen alternately back and forth across the conveyor in a direction transverse or perpendicular to the direction of movement of the conveyor.

Description

BACKGROUND

An apparatus and process for cooling, chilling and freezing a substance, such as a food product, which is carried through the apparatus on a conveyer or other moving substrate.
Many of commercial freezers having food freezing tunnels rely on a high velocity gas flow as the means of convective heat transfer from a food product that is to be chilled or frozen. This gas flow can be generated by a number of different means, all of which involve the use of some type of gas moving device. Most often these devices are some type of fan (axial flow or centrifugal are the most common) or blower. Typically, the fan or blower is situated near a conveyer belt upon which the food product is being carried. The food product entering the freezer has a boundary layer of air surrounding it which insulates the food product from the immediate surrounding atmosphere. Known freezers have employed blowers that generate currents of cooling vapor in many directions.
Fans are a very effective means of creating a high velocity convective environment for high heat transfer, however a significant portion of the cooling vapor does not possess sufficient energy to dissipate or substantially reduce the thickness of the boundary layer of air surrounding and insulating the surface of the food product. In addition, such fans require a large amount of power input and hence energy use. This power input decreases the efficiency of the freezing process because heat is added in the form of work to move the gas.
Convective heat transfer can also be accomplished by the use of impingement devices within food freezing tunnels. Gas and solid or liquid cryogen are mixed within an impingement hood located above a conveyor carrying food products. The gas and solid or liquid cryogen is then directed to an impinger, which in turn directs the gas and solid or liquid cryogen through the impingement jets of an impingement plate directly onto food products in a perpendicular manner.
However, impingement freezing generally requires very high volumetric flows and the power requirement may be as high as 12 hp per 10 ft. freezer length.
It is known that turbulence in convective gas flow streams increases the overall effective heat transfer coefficient of the process. One effective way of creating turbulence is with the use of pulsing flow. A flow which is never allowed to reach laminar status will be more effective at transferring heat. Pulsing flows are difficult to create in conventional food freezing systems which utilize fans because additional mechanical devices are required to ‘start and stop’ the flow—creating pressure pulses. These devices are very complex, difficult to clean and add significant cost to the freezing equipment.

SUMMARY

An apparatus is provided for reducing temperature of food products including a chamber disposed between a first baffle, a second baffle, and at least one volume reservoir in fluid communication with the chamber; at least one conveyor extending into the chamber between the first baffle and the second baffle; at least one cryogen supply in communication with at least one of the chamber and the at least one volume reservoir for providing a mixture of gas and solid or liquid cryogen to the chamber and the at least one volume reservoir; and, at least one pulse flow generator in operative communication with the at least one volume reservoir comprising at least one means for pulsing a turbulent flow comprising the mixture of gas and solid or liquid cryogen across the conveyor within the chamber. A first volume reservoir and an opposed second volume reservoir may be disposed on opposite sides of the conveyor within the chamber.
A process is provided for reducing temperature of food products on a conveyor disposed within a chamber including transporting the food products on the conveyor moving in a direction within the chamber; introducing a mixture of a gas and solid or liquid cryogen into the chamber; and pulsing a turbulent flow of the mixture of gas and solid or liquid cryogen alternately back and forth across the conveyor in a direction transverse or perpendicular to the direction of movement of the conveyor. The process may further include sequentially accepting and expelling the mixture of gas and solid or liquid cryogen from at least one volume reservoir in fluid communication with the chamber.
In certain embodiments, the process may include sequentially accepting and expelling the mixture of gas and solid or liquid cryogen from a first volume reservoir in a cycle opposite sequentially accepting and expelling the mixture of gas and solid or liquid cryogen from a second volume reservoir, the first and second volume reservoirs being disposed on opposite sides of the conveyor in fluid communication with the chamber, thereby creating said turbulent flow.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the apparatus and process provided herein and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the apparatus and process provided herein and, together with the description, serve to explain the principles described herein but are not intended to limit the specification or any of the claims.

FIG. 1 is a cross-sectional view of one embodiment of a cooling, chilling or freezing apparatus.

FIG. 2 is a perspective view of the apparatus of FIG. 1.

FIG. 3A and FIG. 3B are cross-sectional views of a pulse flow generator within a volume reservoir of one embodiment of the cooling, chilling or freezing apparatus.

FIG. 4 is a cross-sectional view of the pulse flow generator within the volume reservoir of a second embodiment of the cooling, chilling or freezing apparatus.

FIG. 5A and FIG. 5B are cross-sectional views of the pulse flow generator within the volume reservoir of a third embodiment of the cooling, chilling or freezing apparatus.

DESCRIPTION

Embodiments herein described overcome problems associated with the use of fans and impingement devices in the refrigeration process, by providing a cooling, chilling or freezing apparatus having a conveyor for carrying a substance such as food product, subjected to a cross-flow pulsing action of gas and cryogen. A volume of gas is moved at high velocity back and forth across a surface of the food product, creating an area of high heat transfer. As the food product travels on the conveyor within the apparatus, such as but not limited to a tunnel freezer, the turbulent cross-flow pulsing action of cooling vapor and cryogen oscillates over a period of time per unit length of movement of the conveyor sufficient to reduce the thickness of the boundary layer of air typically surrounding the food product, or to eliminate the boundary layer.
There is provided an apparatus and process for cooling, chilling and/or freezing food products or other substances in which for example a food item is carried on a conveyor, such as a belt or other moving substrate, through a housing chamber in which the food product is cooled, chilled or frozen due to contact with a mixture of gas and liquid or solid phase cryogen, such as nitrogen or carbon dioxide.
The heat transfer resulting in the cooling or freezing of the food products is effected by the back and forth motion (cross-flow pulsing action) of a turbulent flow of cryogenic vapor around and/or over the food item surface.
The apparatus generally includes a chamber disposed between a first baffle and a second baffle, and at least one volume reservoir in fluid communication with the chamber; at least one conveyor extending into the chamber between the first baffle and the second baffle; at least one cryogen supply in communication with at least one of the chamber and the at least one volume reservoir for providing a mixture of gas and solid or liquid cryogen to the chamber and the at least one volume reservoir; and at least one pulse flow generator in operative communication with the at least one volume reservoir comprising at least one means for pulsing a turbulent gas flow comprising the mixture of gas and solid or liquid cryogen across the conveyor within the chamber. A first volume reservoir and an opposed second volume reservoir may be disposed on opposite sides of the conveyor within the chamber. In one embodiment, side walls of the chamber include at least two volume reservoirs at opposite sides of a tunnel freezer housing.
In one embodiment, a food chilling and/or freezing apparatus is provided which includes a volume reservoir, optionally in the form of a module, disposed on at least one lateral side of the conveyor upon which the food product or other item is transported. Alternatively, the volume reservoir may be disposed at least one of above or below the conveyor. Of course, if the reservoir is disposed below the conveyor, the conveyor must contain apertures so that gas and cryogen can flow through the conveyor to contact the product to be refrigerated.
The volume reservoir module may contain at least one pulse flow generator that enables a high velocity flow of gas and cryogen to be sequentially accepted into the reservoir, and then expelled into the chamber of the apparatus, to effect heat transfer in the chamber and provide for cooling of the food product, i.e. pulsing a mixture of cooling gas and solid or liquid cryogen to contact the surfaces of the conveyed product.
In one embodiment, volume reservoirs are located at opposed sides of the chamber. Each volume reservoir may directly oppose a volume reservoir located on the opposite side of the chamber. A pulse flow generator is present within each volume reservoir. The process includes synchronizing pulse flow generators in the opposing first and second volume reservoirs. The first pulse flow generator (the origin) is alternatingly moving to a closed position, forcing a flow of gas and solid or liquid cryogen to be pulsed from the first volume reservoir across the conveyor in the chamber to the second opposing volume reservoir, while the second pulse flow generator in the opposing second volume reservoir is moving to an opening position for receiving the flow of gas and solid or liquid cryogen directed from the closing origin first pulse flow generator across the chamber. After the gas and solid or liquid cryogen is received into the second volume reservoir, the second pulse flow generator re-circulates the gas and solid or liquid cryogen by moving to a closed position and pulsing a return flow of the gas and solid or liquid cryogen previously received and contained therein into the chamber and across the conveyor to be received in the first volume reservoir. The pulse flow generator in the first volume reservoir correspondingly moves to an opening position for receiving the flow of gas and liquid or solid cryogen pulsed from the closing pulse flow generator within the opposing second volume reservoir. This cycle is repetitious as the conveyor containing the product passes through the chamber.
In certain embodiments, each pulse flow generator includes a rotating cam with an open portion and a closed lobed portion, wherein the open portion is adapted to permit the respective volume reservoir to accept the mixture of gas and solid or liquid cryogen, and the closed lobed portion is adapted to expel the mixture of gas and solid or liquid cryogen from the respective volume reservoir in a cycle opposite to a complementary cycle within the other volume reservoir for alternately pulsing the turbulent flow back and forth across the conveyor.
In other embodiments, each pulse flow generator includes a rotating cam in contact with a pivoting baffle adapted alternately to accept the mixture of gas and solid or liquid cryogen into, and to sweep the mixture of gas and solid or liquid cryogen from, the respective volume reservoir in a cycle opposite to a complementary cycle within the other volume reservoir, to pulse the turbulent flow alternately back and forth across the conveyor.
In certain embodiments, the pulse flow generator comprises an oscillating sealed bladder which moves sequentially to accept the mixture of gas and solid or liquid cryogen into, and to sweep the mixture of gas and solid or liquid cryogen from, the respective volume reservoir in a cycle opposite to a complementary cycle within the other volume reservoir, to pulse the turbulent flow alternately back and forth across the conveyor.
The cryogen supply may be external to the apparatus and may include a cryogen supply port opening, allowing for entry of gas and solid or liquid cryogen into the apparatus. The cryogen supply may also be located as part of or within the apparatus. In certain embodiments, the cryogen supply includes an inlet port for entry of gas and solid or liquid cryogen from the external environment and an outlet port for transfer of the gas and solid or liquid cryogen from the cryogen supply to the chamber and/or volume reservoir. In one embodiment, the cryogen supply includes a cryogen supply port within the volume reservoir.
Once introduced into the apparatus, the amount of gas and solid or liquid cryogen may generally remain relatively fixed, flowing between opposed volume reservoirs across the conveyor in the chamber, or may be replenished with fresh gas and cryogen as spent gas is exhausted from the chamber. At least one valve may also be included as a component of the apparatus allowing for the release of vapor pressure from the chamber and/or volume reservoir if desired. Valves may be located on the surface of the apparatus housing and/or the volume reservoir. The valve may be operated manually or electronically.
The pulse flow generators create a turbulent flow of the mixture of gas and solid or liquid cryogen across the conveyor within the chamber. In certain embodiments, more than one volume reservoir is located on each opposite side of the chamber, continuously or semi-continuously along the length of the conveyor with the chamber.
A baffle is a device such as a plate, wall or screen which functions to direct, deflect, check or regulate the flow or passage of gas and solid or liquid cryogen across the conveyor within the chamber. In certain embodiments, a stationary baffle includes the ceiling of the chamber and another stationary baffle includes the floor of the chamber.
There are various devices which may be used as pulse flow generators. Furthermore, the apparatus may include any number and multiple types of pulse flow generators. In one embodiment, the pulse flow generator includes a rotating cam with an open side and a lobed side. The open side position of the cam allows the volume reservoir to collect or receive gas and solid or liquid cryogen that is moving across the conveyor within the chamber. When the cam rotates to its lobed side position, gas and solid or liquid cryogen is directed out of the volume reservoir and back across the conveyor within the chamber. The lobed side position of the cam may temporarily close off the volume reservoir from receiving gas and solid or liquid cryogen.
In one embodiment, the rotating cam is located within each of the volume reservoirs. Thus, the rotating cams are positioned opposite each other in this embodiment. In this embodiment, turbulent gas flow is generated by rotating each cam within the volume reservoirs in synchronization. For example, when one cam is in its open side position, the other cam will be in its closed lobed side position and vice versa. The rotation of the cams in this manner causes the back and forth flow, or oscillation in the turbulent flow of gas and solid or liquid cryogen across the conveyor within chamber, and may repeat itself several times as a food item or other product passes through the chamber on the conveyor.
In another embodiment, the pulse flow generator may include a rotating cam in contact with a pulse flow generating, moving baffle disposed within the volume reservoir. A spring may bias the baffle in a volume reservoir opening position, while the cam periodically, due to its rotation, pushes the baffle into a volume reservoir closing position. The moving baffles provide the force necessary to pulse the gas and solid or liquid cryogen mixture to flow turbulently across the conveyor. The cams in either embodiment are powered and actuated by conventional means in the industry.
In yet another embodiment, the pulse flow generator includes an oscillating scaled bladder which expands and contracts within the volume reservoir to cyclically expel the mixture from and accept the mixture into the volume reservoir while pulsing the turbulent flow back and forth across the conveyor. The oscillating scaled bladder may be made out of an elastomeric material such as polytetrafluoroethylene (PTFE) or any other material which can retain flexibility at ultra low temperatures, and may operate pneumatically or mechanically.
The total heat transfer rate of the cross-flow pulsing action of the cooling vapor is dependent on local heat transfer coefficients. The amount of heat transferred from the food or other products to the cryogen is dependent on the rate of heat transfer locally between the cryogen and the products. Local heat transfer rates can be changed by controlling the distance from the source of flow of cryogen to the product, the velocity of the turbulent gas flow, and the rate of oscillation of turbulent gas flow per product.
The apparatus is able to rapidly cool, chill and/or freeze a food product with the heat transfer to a cryogen, such as CO₂or N₂, while reducing the amount of cryogen needed, by extracting the maximum cooling effect from a given amount of cryogen. The apparatus transports product from an inlet to an outlet without damaging the product. The apparatus controls the throughput of food items and is resistant to the freezing and plugging of its internal components by snow and ice build-up.
A process is provided for cooling, chilling or freezing products within an apparatus having a conveyor disposed within a chamber including transporting the food products on the conveyor moving in a direction within the chamber; introducing a mixture of a gas and solid or liquid cryogen into the chamber; and pulsing a turbulent flow of the mixture of gas and solid or liquid cryogen alternately back and forth across the conveyor in a direction transverse or perpendicular to the direction of movement of the conveyor. This may include sequentially accepting and expelling the mixture of gas and solid or liquid cryogen from at least one volume reservoir in fluid communication with the chamber.
In certain embodiments, the process includes sequentially accepting and expelling the mixture of gas and solid or liquid cryogen from a first volume reservoir in a cycle opposite and complementary to the cycle of sequentially expelling and accepting the mixture of gas and solid or liquid cryogen from a second volume reservoir, the first and second volume reservoirs being disposed at opposite sides of the conveyor and in fluid communication with the chamber, thereby creating said turbulent flow.
In one embodiment, sequentially accepting and expelling the mixture of gas and solid or liquid cryogen includes rotating a cam having an open side and a closed lobed side within each respective volume reservoir, wherein the open portion is adapted to permit the respective volume reservoir to accept the mixture of gas and solid or liquid cryogen, and the closed lobed portion is adapted to expel the mixture of gas and solid or liquid cryogen from the respective volume reservoir in a cycle opposite to a complementary ccle within the other volume reservoir for alternately pulsing the turbulent flow back and forth across the conveyor. The cooling, chilling or freezing process may be controlled by synchronizing the rotation between the opposing cams such that the open side of one cam on one side of the conveyor and the lobed side of the cam on the other side of the conveyor are simultaneously in position proximate to the conveyor.
In another embodiment, sequentially accepting and expelling the mixture of gas and solid or liquid cryogen includes rotating a cam in contact with a pivoting baffle within each respective volume reservoir, adapted alternately to accept the mixture of gas and solid or liquid cryogen into, and to sweep the mixture of gas and solid or liquid cryogen from, the respective volume reservoir in a cycle opposite to a complementary cycle within the other volume reservoir, thereby pulsing the turbulent flow alternately back and forth across the conveyor. The cooling, chilling or freezing process may be controlled by adjusting the speed of rotation of the cams and/or pulse generating baffles, the amount of gas and solid or liquid cryogen introduced into the chamber and/or the speed of the conveyor which carries food product through the tunnel freezer exposing the product to the oscillating turbulent gas flow.
In yet another embodiment, sequentially accepting and expelling the mixture of gas and solid or liquid cryogen includes oscillating a sealed bladder within each respective volume reservoir, which moves sequentially to accept the mixture of gas and solid or liquid cryogen into, and to sweep the mixture of gas and solid or liquid cryogen from, the respective volume reservoir in a cycle opposite to a complementary cycle within the other volume reservoir, thereby pulsing the turbulent flow alternately back and forth across the conveyor. The cooling, chilling or freezing process may be controlled by adjusting the speed of movement of the oscillating sealed bladder, the amount of gas and solid or liquid cryogen introduced into the chamber, and/or the speed of the conveyor which carries food product throughout the tunnel freezer exposing the food product to oscillating turbulent gas flow.
FIGS. 1 and 2 provide exemplary schematic views of an embodiment of the apparatus shown generally at 2. In FIG. 1, chamber 4 of the cooling, chilling or freezing apparatus 2 includes a first baffle 12 above a conveyor 6 and a second baffle 14 below the conveyor 6. Product 16, such as food product, is transported on the conveyor 6 through the chamber 4. The first baffle 12 may be the ceiling of the tunnel freezer and the second baffle 14 may be the floor of a tunnel freezer. Volume reservoirs 8, 10 are disposed at opposed sides of the conveyor 6 and are in fluid communication with the chamber 4. A pulsing flow of gas and solid or liquid cryogen is shown at arrows 18 and travels back and forth from the first volume reservoir 8 across the chamber 4 to the second volume reservoir 10 on the opposite side of the apparatus 2. The conveyor 6 is adapted to carry food products 16 or other items to be cooled, chilled or frozen in a direction represented by arrow 32. The conveyor 6 may be constructed of a permeable material such as a mesh allowing the pulsing gas flow 18 to freely pass through the conveyor for further cooling all surfaces of the product 16. As the pulsing gas flow 18 travels across the conveyor 6, heat is transferred from the food products 16 to the gas and cryogen in the gas flow 18, resulting in cooling, chilling and/or freezing of the food products 16. The conveyor 6 may be permanently or removably mounted to the floor or second baffle 14 of the apparatus 2 by supports 20.
FIGS. 3A and 3B show a schematic view of one embodiment of the apparatus 2 in which the pulse flow generator 3 comprises rotating cams 22, 24. In position A shown in FIG. 3A, rotating cam 22 on the left side is in a lobed position, having directed the pulsing gas flow 18 in direction A towards the rotating cam 24 on the right side, which is in the open position. In position B shown in FIG. 3B, rotating cam 24 on the right side is in the lobed position, having directed the pulsing gas flow 18 in direction B towards rotating cam 22 on the left side, which is in the open position. The cams 22, 24 may be formed in a variety of shapes, such that each is capable of expelling gas and cryogen sequentially from the volume reservoir 8, 10 and pulsing such gas and cryogen across the conveyor 6, in the chamber 4, followed by allowing the return pulse to fill the volume reservoir 10, 8 to complete the cycle.
FIG. 4 shows an alternative embodiment of the pulse flow generator 3 in which the rotating cam 22 is in contact with a pulse generating baffle 26 or pivoting baffle. As the cam 22 rotates from its open and lobed positions, it causes the pulse generating baffle 26 such as a longitudinal member to move or sweep through the volume reservoir 8, directing the pulsing gas flow represented by arrow 18 towards the chamber 4 and across the conveyor 6. The pulse generating baffle 26 returns to its original position by means of a biasing member such as a spring 28 to receive the return pulsing gas flow 18 from the opposed volume reservoir 10 through the chamber 4. The biasing member 28 may oppose the action of the rotating cam 22.
FIGS. 5A and 5B show an alternative embodiment of the pulse flow generator 3 in which an oscillating pressure seal 30 or bladder functions similar to the rotating cam 22, 24. In this embodiment, the oscillating pressure seal 30 moves to position A shown in FIG. 5A to direct the pulsing gas flow 18 out of the volume reservoir 8, into the chamber 4 and across the conveyor 6. To complete the cycle, the pressure seal 30 moves to position B shown in FIG. 5B to permit the volume reservoir to receive the return pulsing gas flow 18 from the chamber 4.
In an alternative embodiment, the cooling, chilling, or freezing apparatus 2 may be retrofitted to an existing tunnel freezer. In a further alternate embodiment, the conveyor 6 may include a transport surface such as an open web or mesh to convey the food products; the baffles 12, 14 may be disposed at each side of the conveyor 6 to at least partially define the chamber 6; and the volume reservoirs 8, 10 may be disposed above and below the conveyor 6.
An apparatus for reducing temperature of a food product is therefore provided including a chamber into which the food product is provided: reservoir means in fluid communication with the chamber and constructed and arranged to provide a cryogen medium to the chamber; and generator means disposed in the reservoir means, the generator means comprising pulse flow means for providing a pulsing flow of the cryogen medium at select intervals to the chamber.
A process for reducing the temperature of a food product is also provided including conveying the food product to an area where a temperature of the food product will be reduced; providing a cryogenic medium to the area; and pulsing a flow of the cryogenic medium across the area and the food product at select intervals.
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.

Claims

1. An apparatus for reducing temperature of food products, comprising:

a chamber disposed between a first baffle, a second baffle, and at least one volume reservoir in fluid communication with the chamber;

at least one conveyor extending into the chamber between the first baffle and the second baffle;

at least one cryogen supply in communication with at least one of the chamber and the at least one volume reservoir for providing a mixture of gas and solid or liquid cryogen to the chamber and the at least one volume reservoir; and

at least one pulse flow generator in operative communication with the at least one volume reservoir comprising at least one means for pulsing a turbulent flow comprising the mixture of gas and solid or liquid cryogen across the conveyor within the chamber.

2. The apparatus of claim 1, wherein a first volume reservoir and a second volume reservoir are disposed on opposite sides of the conveyor within the chamber.

3. The apparatus of claim 2, wherein the first baffle comprises a ceiling and the second baffle comprises a floor of the apparatus.

4. The apparatus of claim 3, wherein the first volume reservoir and the second volume reservoir are adjacent to opposite sides of the conveyor.

5. The apparatus of claim 4, wherein at least one pulse flow generator is disposed within each of the first volume reservoir and the second volume reservoir.

6. The apparatus of claim 5, wherein each of the at least one pulse flow generator comprises a rotating cam with an open portion and a closed lobed portion, wherein the open portion is adapted to permit the respective volume reservoir to accept the mixture of gas and solid or liquid cryogen, and the closed lobed portion is adapted to expel the mixture of gas and solid or liquid cryogen from the respective volume reservoir in a cycle opposite to a complementary circle within the other volume reservoir for alternately pulsing the turbulent flow back and forth across the conveyor.

7. The apparatus of claim 5, wherein each of the at least one pulse flow generator comprises a rotating cam in contact with a pivoting baffle adapted alternately to accept the mixture of gas and solid or liquid cryogen into, and to sweep the mixture of gas and solid or liquid cryogen from, the respective volume reservoir in a cycle opposite to a complementary cycle within the other volume reservoir, to pulse the turbulent flow alternately back and forth across the conveyor.

8. The apparatus of claim 7, wherein the pivoting baffle comprises a longitudinal member within the volume reservoir.

9. The apparatus of claim 7 wherein the pivoting baffle is in contact with a biasing member opposing the action of the rotating cam.

10. The apparatus of claim 5 wherein the at least one pulse flow generator comprises a bladder adapted to move sequentially to accept the mixture of gas and solid or liquid cryogen into, and to sweep the mixture of gas and solid or liquid cryogen from, the respective volume reservoir in a cycle opposite to a complementary cycle within the other volume reservoir, to pulse the turbulent flow alternately back and forth across the conveyor.

11. A process for reducing temperature of food products on a conveyor disposed within a chamber, comprising:

transporting the food products on the conveyor moving within the chamber;

introducing a mixture of a gas and solid or liquid cryogen into the chamber; and

pulsing a turbulent flow of the mixture of gas and solid or liquid cryogen alternately back and forth across the conveyor in a direction transverse or perpendicular to the movement of the conveyor in the chamber.

12. The process of claim 11, further comprising sequentially accepting and expelling the mixture of gas and solid or liquid cryogen from at least one volume reservoir in fluid communication with the chamber.

13. The process of claim 11, further comprising sequentially accepting and expelling the mixture of gas and solid or liquid cryogen from a first volume reservoir in a cycle complementary and opposite to a cycle of sequentially expelling and accepting the mixture of gas and solid or liquid cryogen from a second volume reservoir, the first and second volume reservoirs being disposed on opposite sides of the conveyor in fluid communication with the chamber, thereby creating said turbulent flow.

14. The process of claim 13, wherein said sequentially accepting and expelling comprises rotating a cam having an open side and a closed lobed side within each respective volume reservoir, wherein the open portion is adapted to permit the respective volume reservoir to accept the mixture of gas and solid or liquid cryogen, and the closed lobed portion is adapted to expel the mixture of gas and solid or liquid cryogen from the respective volume reservoir in a cycle opposite to a complementary cycle within the other volume reservoir for alternately pulsing the turbulent flow back and forth across the conveyor.

15. The process of claim 13, wherein said sequentially accepting and expelling the mixture of gas and solid or liquid cryogen comprises rotating a cam in contact with a pivoting baffle within each respective volume reservoir, adapted alternately to accept the mixture of gas and solid or liquid cryogen into, and to sweep the mixture of gas and solid or liquid cryogen from, the respective volume reservoir in a cycle opposite to a complementary cycle within the other volume reservoir, thereby pulsing the turbulent flow alternately back and forth across the conveyor.

16. The process of claim 13, wherein said sequentially accepting and expelling the mixture of gas and solid or liquid cryogen comprises oscillating a sealed bladder within each respective volume reservoir, which moves sequentially to accept the mixture of gas and solid or liquid cryogen into, and to sweep the mixture of gas and solid or liquid cryogen from, the respective volume reservoir in a cycle opposite to a complementary cycle within the other volume reservoir, thereby pulsing the turbulent flow alternately back and forth across the conveyor.

17. An apparatus for reducing temperature of a food product, comprising:

a chamber into which the food product is provided;

reservoir means in fluid communication with the chamber and constructed and arranged to provide a cryogen medium to the chamber; and

generator means disposed in the reservoir means, the generator means comprising pulse flow means for providing a pulsing flow of the cryogen medium at select intervals to the chamber.

18. A process for reducing the temperature of a food product, comprising:

conveying the food product to an area where a temperature of the food product will be reduced;

providing a cryogenic medium to the area; and

pulsing a flow of the cryogenic medium across the area and the food product at select intervals.