US3898863A - Cryogenic refrigeration apparatus with automatic temperature control and automatic gas balance control - Google Patents

Abstract

Apparatus and method for refrigerating articles comprising a heat insulated tunnel, a conveyor therein for passing articles to be refrigerated through the tunnel, introducing means for a cryogen into the chamber that comprises a cryogen gas therein, circulating means for circulating the gas in a circulation loop including a first reach in direct heat exchange contact with the articles and a second reach out of this direct contact, a gas exhaust for expelling refrigerant gas from the tunnel spaced from the loop and adjacent the tunnel entrance, a flow restrictor between the circulation loop and the exhaust for restricting volumetric flow of gas from the circulation loop to the exhaust and thereby maintaining a rapid gas flow rate in the circulation loop, a gas outlet vent located adjacent to the tunnel exit, temperature control for controlling the rate of introducing the cryogen as a function of the gas temperature in the loop and preferably but not necessarily in the second reach in the loop and gas balance control means for proportioning gas flow between the loop and the vent as a function of the gas temperature at the vent.

Description

United'States Patent Wagner [451 Aug. 12, 1975 Primary ExaminerWilliam F. ODea Assistant ExaminerRonald C. Capossela Attorney, Agent, or Firm-1-1ofgren, Wegner, Allen, Stellman & McCord [57] ABSTRACT Apparatus and method for refrigerating articles comprising a heat insulated tunnel, a conveyor therein for passing articles to be refrigerated through the tunnel, introducing means for a cryogen into the chamber that comprises a cryogen gas therein, circulating means for circulating the gas in a circulation loop including a first reach in direct heat exchange contact with the articles and a second reach out of this direct contact, a gas exhaust for expelling refrigerant gas from the tunnel spaced from the loop and adjacent the tunnel entrance, a flow restrictor between the circulation loop and the exhaust for restricting volumetric flow of gas from the circulation loop to the exhaust and thereby maintaining a rapid gas flow rate in the circulation loop, a gas outlet vent located adjacent to the tunnel exit, temperature control for controlling the rate of introducing the cryogen as a function of the gas temperature in the loop and preferably but not necessarily in the second reach in the loop and gas balance control means for proportioning gas flow between the loop and the vent as a function of the gas temperature at the vent.

16 Claims, 11 Drawing Figures GAS BALANCE CONTROL INSTRUMENT TEMPE RA TURE CONTROL INS TRUME N T [75] lnventor: Richard C. Wagner, Darien, 111.

[73] Assignee: Hollymatic Corporation, Park Forest, 111.

[22] Filed: Dec. 14, 1973 [21] App]. No.: 424,768

Related US. Application Data [63] Continuation-impart of Ser. Nos. 264,133, June 19, 1972, Pat. No. 3,824,806, and Ser. No. 390,755, Aug. 23, 1973, Pat. No. 3,871,186.

[52] US. Cl. 62/208; 62/216; 62/374; 62/380 [51] Int. Cl. F25b 41/06 [58] Field of Search 62/63, 208, 209, 216, 374, 62/375, 380

[56] References Cited UNlTED STATES PATENTS 3,345,828 10/1967 Klee et a1 62/63 3,553,973 l/1971 Moran 62/63 3,605,434 9/1971 Boese.... 62/374 3,613,386 10/1971 Klee 62/208 55 5'2 SPRA VALVE 56 g 57 CON TROL MO TOR LN: SPRAY 62 HEADER THERMOCOUPLE (6A5 BALANCE) GAS BALANCE CONTROL DAMPER 6N2 HIGH VELOCITY FLOW L TE MP. CON TROL THERMO COUPLE PATENTEU mi 2 I975 SHEET PATENTEB AUG! 2M5 SHEET SHEET PAIENTEC PATENTEB AUG 1 21975 mu \muaq qm mqQ 1 CRYOGENIC REFRIGERATION APPARATUS WITH AUTOMATIC TEMPERATURE CONTROL AND AUTOMATIC GAS BALANCE CONTROL Cross-Reference to Related Applications This application is a continuation-in-part of my prior applications Ser. No. 264,133, filed June 19, 1972, now U.S. Pat. No. 3,824,806 dated July 23, 1974, and Ser. No. 390,755, flied Aug. 23, 1973, now U.S. Pat. No. 3,871,186 dated Mar. 18, 1975.

BACKGROUND OF THE INVENTION One of the features of this invention is to provide a refrigerating apparatus for refrigerating articles while they are being transported through an insulated chamber or tunnel and while circulating refrigerant gas in the tunnel in contact with the articles together with temperature and gas control means in which the temperature within the circulation loop is controlled by the flow of cryogenic fluid which provides more refrigerant to the tunnel when desired to maintain a low temperature and a gas balance control for proportioning gas flow between the circulation loop and a vent that is separate from the main exhaust as a function of the temperature at the vent, all of which tends to maintain optimum refrigeration temperature automatically within the interior of the chamber or tunnel.

Another feature of the invention is to provide a method in which the refrigerating method comprises controlling the amount of refrigerant introduced into the tunnel by the temperature in the circulation loop of gas within the tunnel and selectively directing gas either toward the principal gas exhaust or toward a gas vent that are at adjacent ends of the chamber or tunnel by temperature of the gas at the vent.

The most pertinent prior art of which applicant is aware are U.S. Pat. Nos. 3,345,828, 3,403,527, 3,427,820, 3,431,745 and 3,600,901. None of these, however, disclose the features of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. la and 1b combine in a plan view of an apparatus embodying the invention.

FIGS. 2a, 2b and 2c combine in a longitudinal sectional view through the apparatus of FIGS. 1a and lb.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the embodiment shown in the drawings the apparatus for refrigerating articles comprises an elongated freezing tunnel 11 or chamber having top 12, bottom l3 and side 14 and 15 insulated walls. The top insulated walls 12 are in the form of hinged lids 16 which may be raised and lowered by means of hydraulie cylinders 17, in the customary manner, of which only two are illustrated in FIGS. la and lb and which are illustrated in side elevation in FIGS. 3, 4, 6 and 7.

Positioned within the chamber or tunnel l 1 between an entrance l8 and an exit 19 thereto is a customary conveyor 20 for conveying articles in the chamber in a path coinciding with the upper length 21 of the conveyor between the entrance and exit. One such article is illustrated schematically at 22 in FIG. 20.

The fluid cryogen is a liquid of which liquid nitrogen is an excellent example for the illustrated embodiment. Liquid carbon dioxide is another example. The liquid cryogen in either case generates a cryogen gas within the tunnel. The liquid nitrogen of this embodiment is introduced by means of a liquid spray system 23 which as illustrated is an assembly of nozzles 24 arranged in the system 23 and spaced longitudinally and transversely of the chamber.

Thus in the illustrated embodiment of FIG. 4 there are six nozzles spanning the width of the chamber 11 and eight nozzles arranged longitudinally in each row as shown in FIG. 2a. The liquid cryogen is supplied to the nozzle assembly by means of a pipe 25 which communicates with the piping 26 interconnecting the nozzles 24 by means of a flexible hose 27. With this arrangement the entire liquid flow assembly 23 may be elevated for cleaning when the lids 16 are raised without requiring dismantling of the assembly 23.

In order to aid in the heat transfer the cryogen gas is circulated over the articles within the chamber 1 I. This circulation aids the intimate contact of the cryogen gas with the articles particularly where the conveyor 20 is of the preferred open mesh metal construction. The circulating means comprises a horizontal baffle 28 beneath the conveyor 20 and thus beneath the articles 22 conveyed thereon with this baffle 28 having an end 29 adjacent to but short of the entrance end 18 of the tunnel 1 1. The circulation flow which is caused by the rotatable blower 30 is in a path illustrated by the circulation arrows 31 as shown in FIGS. 2b, 2c, 5, 6 and 7.

The circulation path as is illustrated most clearly in FIGS. 2b and 6 includes a duct 32 located externally of the chamber 11. Thus as shown in FIG. 6 this duct is located beneath and to the side of the apparatus 10 and communicates with the bottom of the chamber 11 by means of a vertical fitting 33 that directs gas vertically downwardly into the duct 32 and upwardly at the side through a passage 34 into the blower 30 where the recirculated gas is introduced laterally back into the tunnel where it is deflected by curved spaced vanes 35 for longitudinal flow toward the entrance 18 as illustrated in FIG. 5.

Beneath the spray head assembly 23 there is provided a pan 36 sloped toward the circulation duct 32 to direct by gravity flow refrigerant gas and excess liquid from the spray zone 37 into the duct 32.

Communicating with the tunnel or chamber 11 adjacent the entrance 18 are gas outlet exhaust means 38 for exhausting 39 the cryogen gas from the circulation loop 31. The baffle 28 which is adjacent the entrance 18 to the tunnel and therefore adjacent the gas outlet exhaust means 38 separates the chamber 1 1 into a first or upper reach 40 and a second or lower reach 41 of the loop 31. As illustrated in FIGS. 2b and 2c the reach 40 provides countercurrent direct heat exchange contact with the articles 22. The second reach 41 gas is out of direct Contact with the articles.

Provided in the chamber 11 above the conveyor 20 and in communication with the upper reach 40 are a plurality of gas moving devices 42 here shown as vertical axis fans for providing vertical axial flow illustrated by the arrows 43. These fans 42 are longitudinally spaced from each other and in the illustrated embodiment are six in number although more or less can be used depending upon the size of the apparatus.

As illustrated by the arrows 43 in FIG. 2b the exhaust from the fans is downwardly through the conveyor and over the articles 22 carried thereon and is then directed back upwardly by impingement upon the baffle 28. The fans 42 serve as turbulizers to obtain better heat transfer between the articles conveyed through the tunnel by the conveyor 20 and the gas. This results in the exhaust gases illustrated at 39 in FIG. 2c having a higher temperature caused by greater heat extracted from the entering articles 22. Thus in one embodiment of the apparatus of this invention the temperature of the exhaust gases 39 was not more than 80 less than the temperature of the incoming articles 22. Furthermore, the transverse or in this embodiment vertical exhaust from the axial flow fans 44 is in a direction transverse to the longitudinal circulation flow path 31 with the combination of gas flows at 90 to each other increasing the turbulence with corresponding increases in heat transfer so that a shorter tunnel l 1 may be employed for a given refrigerating capacity.

The apparatus is constructed in separable sections for cleaning. Such a separable arrangement is disclosed in my prior US. Pat. No. 3,580,000.

Provided in the chamber or elongated tunnel 11 are a series of triangular baffles 45 with the apex extending I downwardly as shown in FIG. and with the angle at the apex being about 90. These transverse baffles 45 which extend from side to side across the chamber serve as flow restriction means between the entrance end of the circulation baffle 28 and the exhaust 38 for limiting the volumetric flow 46 of gas from the circulation loop 31 to the exhaust 38. This baffle limitation of the flow thereby serves to increase the volumetric flow in the circulation loop 31 and thus its linear velocity, thereby insuring better heat transfer between the gas in the circulation loop and the moving series of articles 22 being refrigerated.

The top insulated wall 12 of the tunnel is raised in a portion 47 where the right angled turning vanes 35 serve to direct the circulating 31 gas back into the beginning of the upper or first reach 40 of the circulation loop where the gas is directed as indicated by the arrow 31 in FIG. 2c in countercurrent flow with respect to the direction of movement of the articles 22 by the conveyor 20. Located at this entrance 48 to the circulation loop 31 there is provided a gas balance control for proportioning gas flow between the loop 31 and a gas vent 49 that is adjacent the tunnel exit 19.

In the illustrated embodiment this gas balance control comprises a first damper 50 that is hingedly mounted for swinging between a position against the top wall 12 (FIG. 8) and a position at about 90 to the position shown in FIG. 8 for proportioning the gas flow between the circulation loop 31 and thus the exhaust 3 8 at the product entrance 18 of the tunnel and the gas vent 49 at the product exit 19 of the tunnel.

This gas balance control damper 50 also serves to control the velocity of the gas flow in the circulation loop 31 that includes both the upper article contacting first reach '40. and the lower reach 41 as previously described with the two reaches being separated by the circulation baffle 28. Theposition of this velocity and balance control damper 59 is controlled by a thermocouple 51 of the customary type operating a motor control 52 also of the customary type such as illustrated by the motor control 62in my prior US. Pat. No. 3,600,901. i

Gas flow from the gas vent 49 is at least sufficient to prevent ambient air from entering the tunnel during operation thereof under any operating conditions so as to prevent introducing warm air, moisture and the like. The temperature within the tunnel 11 is controlled by controlling the rate of introduction of the cryogen as illustrated by the liquid nitrogen sprays 53. Thus in the illustrated embodiment liquid nitrogen is supplied through a pipe 54 and a variable valve 55 to the spray header or assembly 23. Flow through this valve 55 is automatically controlled by a control motor 56 whose operation is regulated by a temperature control instrument 57 of standard and well known construction which in turn is controlled by a temperature control thermocouple 58 that is positioned in the xternal duct portion 32 of the gas circulation loop. As is illustrated in FIG. 6 this thermocouple 58 is preferably located in the side portion 34 of the duct 32 and adjacent the entrance to the circulation fan or blower 30. Thus the temperature control means for the interior of the tunnel 11 functions in part by controlling the rate of introduction od cryogen as a function of gas temperature in the circulation loop 31 and in the embodiment disclosed specifically by the temperature in the external portion 32 of this loop.

The interior of the tunnel 11 is also provided with a second damper 59 that is located at the entrance 60 to the external duct portion 32 and at the adjacent end 61 of the baffle 28. The second damper 59 is moved be tween nearly closed and completely open position by hand adjustment.

In operation the manual damper 59 is left slightly open as indicated schematically in FIG. 8 and after start-up the balanced condition of a slight outward flow through vent 49 and exhaust flow through 38 is maintained by the temperature controlled gas balance damper 50. If, due to abnormal conditions within the tunnel, this is not sufficient to maintain the desired balance, then the manual damper 59 is adjusted to provide a wider space 60 so that more of the gas is drawn into the recirculation loop directly from .the spray zone thereby decreasing the flow out through the vent 49 and correspondingly increasing flow through the exhaust duct 38. No other adjustments are made on the manual damper 59 unless conditions change so-as to require the re-adjustment. Typical operating conditions that would require such an adjustment of the manual damper 59 are increased restrictions to flow in the recirculation path 31 due to the bulk of the articles 22 being refrigerated or extremely long tunnel structures which would themselves cause flow restrictions in the recirculation path 31 or the like. At a balanced flow there is a slight purge of refrigerant gas outward through the vent 49 which is indicated by the desired temperature of from l0 to +lOF., or about 0F., at the temperature sensitive element or thermocouple 51 so that there is no entrance of ambient air.

Once this condition has been achieved the manual damper 59 is untouched and all adjustments necessary to allow for the various loads and'various heat inputs are accomplished by lowering and raising the first damper 50 in response to temperature fluctuations at the thermocouple 54 located at the gas vent 49. At minimum load when the passage of articles 22 is at a minimum or even temporarily suspended the damper 50 is in its lowered position which is about 90 from the elevated position of FIG. 8.

The liquid spray assembly 23 is located between the circulation baffle 28 and the product exit 19 of the tunnel. The gas generated in the spray zone flows both countercurrently to the articles as indicated by the arrows 62 of FIGS. and 2b and a portion into duct 32 where it enters the circulation loop 31. The temperature within the chamber is then controlled bythe temperature in the circulation loop as sensed by the thermocouple 58 that controls the amount of liquid nitrogen fed to the spray head 23 by the pipe 62.

It has been customary in the past to exhaust gas from the tunnel as at the illustrated exhaust duct 38 to accommodate the incoming fresh gas 62 from the introduced refrigerant. Because the amount of gas that is vaporized from the fresh refrigerant is dependent upon the load of articles being passed through the tunnel and is thus variable the amount of gas withdrawn at the exhaust 38 must be adjusted to meet changing loads. However, it has been found difficult to regulate and balance the refrigerant and particularly the freezing operation by solely adjusting the amount of exhaust gas as at the duct 38. This is true because even the minimum withdrawal of gas from the circulation path 31 at minimum loads is greater than the rate of gas generation and this results in air inflow at the exit end 19 of the tunnel.

With the apparatus and method of this invention there is always at least a minimum amount of outward flow of gas at vent 49 and at 46 to prevent entrance of ambient air in any quantity. Then the amount of fresh refrigerant introduced and thus the amount of gas generated is controlled for varying load conditions by the temperature sensor 58 which as described controls the amount of fresh refrigerant introduced. Actually, the temperature controls as illustrated and described are so sensitive that under all operating conditions the temperature at rhe vent 49 will be approximately 0F. and the temperature at the exhaust duct 38 will be about 80F. colder than the incoming product temperature. This condition is achieved not only by the variable damper 50 and its temperature sensor 51 at the tunnel exit but also by recirculating the gas 31 through the tunnel and countercurrently to the articles passing therethrough with this amount recirculated being controlled at least in part by the previously described baffles 45.

Various parts of the apparatus shown in the drawings are similar to corresponding parts of my earlier copending applications Ser. No. 264,133, filed June 19,

:present application. In the first of these applications there is disclosed an apparatus which uses liquid carbon dioxide as the cryogen and also a circulation baffle similar to the above baffle 28. The controls and balances of this invention are equally applicable to a liquid carbon dioxide system as they are to a liquid nitrogen system.

The second of the above applications or Ser. No. 339,395 now US. Pat. No. 3,855,815 also discloses a system in which a flow restricting member is provided between the gas circulation path and the gas exhaust to serve substantially the same exhaust control and circulation speed up effects as the baffles 45 disclosed herein.

In the last of the above applications there is disclosed a system similar to that disclosed herein but omitting the gas flow restrictor baffles and the temperature and balance controls.

The gas balance control dampers and 59 and the temperature controls -58 are in the prior art.

Having described my invention as related to the embodiment shown in the accompanying drawings, it is my intention that the invention be not limited by any of the details of description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the appended claims.

I claim:

1. Apparatus for refrigerating articles, comprising: means defining a thermally isolated chamber having boundary walls and an entrance and an exit for passage of said articles through said chamber; conveyor means in said chamber for said passage; introducing means for introducing a cryogen means into said chamber for providing cryogen gas in said chamber; circulating means for circulating said gas in a circulation loop including a first reach in direct heat exchange contact with said articles and a second reach out of said direct contact with said articles; gas outlet exhaust means from said chamber spaced from said loop on the side thereof adjacent said chamber entrance; flow restriction means in said chamber between said loop and said exhaust for limiting volumetric gas flow from said loop to said exhaust and thereby maintaining a rapid gas flow rate in said loop; gas outlet vent means from said chamber located adjacent to said chamber exit; temperature responsive control means for automatically controlling the rate of said introducing of cryogen as a function of gas temperature in said loop; and temperature responsive gas balance control means for automatically proportioning gas flow between said loop and said vent means as a function of gas temperature at said vent means.

2. The apparatus of claim 1 wherein said temperature responsive control means includes a temperature sensor sensing the temperature of said gas in said second reach.

3. The apparatus of claim 1 wherein there is provided a manually adjustable second damper between said introducing means and said second reach.

4. The apparatus of claim 1 wherein said introducing means is located between said circulating means and said tunnel exit.

5. The apparatus of claim 1 wherein said temperature responsive gas balance control means comprises a first damper means in said circulation loop movable from fully open position to loop intercepting position for directing gas selectively and proportionally from said loop toward said vent means.

6. The apparatus of claim 5 wherein said loop has an area comprising a common exit from the second reach and entrance to the first reach, and said first damper is located in said area.

7. The apparatus of claim wherein said loop has an area comprising a common exit from the second reach and entrance to the first reach, said first damper is located in said area, and there is provided a manually adjustable second damper between said introducing means and said second reach.

8. The apparatus of claim 7 wherein said chamber comprises a tunnel, said walls comprise a top wall and a bottom wall and said first damper is positioned adjacent to said top wall and said second damper adjacent to said bottom wall.

9. The apparatus of claim 1 wherein said circulating means comprises a baffle in said chamber separating said first and second reaches of said loop.

10. The apparatus of claim 9 wherein said baffle is longitudinal of and between the top and bottom of said chamber with the first reach and said conveyor means being above the bafile and the second reach including the area beneath the baffle.

11. The apparatus of claim 1 wherein said chamber comprises a tunnel, said second reach of said circulation loop includes a duct located externally of the tunnel having a duct entrance for receiving gas from said chamber and a duct exit for delivering gas to said first loop reach.

12. The apparatus of claim 11 wherein said temperature responsive control means includes a temperature sensor sensing the temperature of said gas in said second reach duct.

13. The apparatus of claim 11 wherein there is provided a manually adjustable second damper between said introducing means and said second reach located at said'duct entrance.

14. The apparatus of claim 11 wherein said introducing means is located between said duct and said tunnel exit.

15. The apparatus of claim 1 wherein said chamber comprises an elongated tunnel having a top wall and said means for restricting gas flow comprises a baffle extending downwardly from the top wall and spaced above the conveyor to permit said passage of the articles.

16. The apparatus of claim 15 wherein there is provided a plurality of said baffles spaced along said top wall between said circulation loop and said gas outlet exhaust means.

Claims (16)

1. Apparatus for refrigerating articles, comprising: means defining a thermally isolated chamber having boundary walls and an entrance and an exit for passage of said articles through said chamber; conveyor means in said chamber for said passage; introducing means for introducing a cryogen means into said chamber for providing cryogen gas in said chamber; circulating means for circulating said gas in a circulation loop including a first reach in direct heat exchange contact with said articles and a second reach out of said direct contact with said articles; gas outlet exhaust means from said chamber spaced from said loop on the side thereof adjacent said chamber entrance; flow restriction means in said chamber between said loop and said exhaust for limiting volumetric gas flow from said loop to said exhaust and thereby maintaining a rapid gas flow rate in said loop; gas outlet vent means from said chamber located adjacent to said chamber exit; temperature responsive control means for automatically controlling the rate of said introducing of cryogen as a function of gas temperature in said loop; and temperature responsive gas balance control means for automatically proportioning gas flow between said loop and said vent means as a function of gas temperature at said vent means.

2. The apparatus of claim 1 wherein said temperature responsive control means includes a temperature sensor sensing the temperature of said gas in said second reach.

3. The apparatus of claim 1 wherein there is provided a manually adjustable second damper between said introducing means and said second reach.

4. The apparatus of claim 1 wherein said introducing means is located between said circulating means and said tunnel exit.

5. The apparatus of claim 1 wherein said temperature responsive gas balance control means comprises a first damper means in said circulation loop movable from fully open position to loop intercepting position for directing gas selectively and proportionally from said loop toward said vent means.

6. The apparatus of claim 5 wherein said loop has an area comprising a common exit from the second reach and entrance to the first reach, and said first damper is located in said area.

7. The apparatus of claim 5 wherein said loop has an area comprising a common exit from the second reach and entrance to the first reach, said first damper is located in said area, and there is provided a manually adjustable second damper between said introducing means and said second reach.

8. The apparatus of claim 7 wherein said chamber comprises a tunnel, said walls comprise a top wall and a bottom wall and said first damper is positioned adjacent to said top wall and said second damper adjacent to said bottom wall.

9. The apparatus of claim 1 wherein said circulating means comprises a baffle in said chamber separating said first and second reaches of said loop.

10. The apparatus of claim 9 wherein said baffle is longitudinal of and between the top and bottom of said chamber with the first reach and said conveyor means being above the baffle and the second reach including the area beneath the baffle.

11. The apparatus of claim 1 wherein said chamber comprises a tunnel, said second reach of said circulation loop includes a duct located externally of the tunnel having a duct entrance for receiving gas from said chamber and a duct exit for delivering gas to said first loop reach.

12. The apparatus of claim 11 wherein said temperature responsive control means includes a temperature sensor sensing the temperature of said gas in said second reach duct.

13. The apparatus of claim 11 wherein there is provided a manually adjustable second damper between said introducing means and said second reach located at said duct entrance.

14. The apparatus of clAim 11 wherein said introducing means is located between said duct and said tunnel exit.

15. The apparatus of claim 1 wherein said chamber comprises an elongated tunnel having a top wall and said means for restricting gas flow comprises a baffle extending downwardly from the top wall and spaced above the conveyor to permit said passage of the articles.

16. The apparatus of claim 15 wherein there is provided a plurality of said baffles spaced along said top wall between said circulation loop and said gas outlet exhaust means.

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