US2959034A - Apparatus for chilling foodstuffs and the like for storage and shipment - Google Patents

Description

w. L. MORRISON 2,959,034 APPARATUS FOR CHILLING FOODSTUFFS AND THE LIKE FOR STORAGE AND SHIPMENT Nov. 8, 1960 Filed May 21, 1956 3 Sheets-Sheet 1 Y 49 v 9 49 77/ v Ea 77a Invenior Wz'Z/ardl. Worrz's on Nov. 8, 1960 w, L, MORRISON 2,959,034

APPARATUS FOR CHILLING FOODSTUFFS 'AND THE LIKE FOR STORAGE 'AND SHIPMENT 1 Filed may 21, 1956 3 she ts-sheet 2 INVENTOR. WILLARD L.MORRISON BY PARKER 8. CARTER ATTORNEYS Nov. 8, 1960 v w. MORRISON 2,959,034

APPARATUS FOR CHILLING FOODSTUFFS AND THE LIKE FOR STORAGE AND SHIPMENT Filed May 21, 1956 3 Sheets-Sheet 5 ill. FJz 44419 11/ /r INVENTOR. WILLARD L.MORRISON BY PARKER & CARTER ATTORNEYS United APPARATUS FOR CHILLING FOODSTUFFS AND THE LIKE FOR STORAGE AND SHIPMENT Filed May 21, 1956, Ser. No. 586,205

6 Claims. (Cl. 62-376) My invention relates to improvement in and apparatus for chilling foodstuffs and the like for storage and shipment at temperatures far below zero degrees F. and at approximately atmospheric pressure and has for one object to provide a method and apparatus wherein the foodstuffs or other cargo may be chilled by direct contact with such a non-deleterious refrigerant as liquid nitrogen at atmospheric pressure and wherein the latent heat necessary to boil the liquid nitrogen is removed from the foodstuffs or other cargo and the nitrogen in gaseous phase is immediately discharged from the cooling zone with ,little if any rise in temperature, to be reliquefied and reused.

Another object of my invention is to provide a method and apparatus whereby the cooling, evaporation and reliquefaction cycle may be conducted part of the time in a closed circuit and part of the time in an open circuit at such time as water vapor, or other diluents associated with the material being chilled are added to the nitrogen, the contaminated nitrogen will be discharged to atmosphere. Thus the closed portion of the circuit contains little, if any contamination and cleaning or purging of the contents of the circuit is seldom if ever necessary.

This elimination of contaminated nitrogen can, if desired, take place every time a new chill box is placed in ,series with the liquefaction system. On the other hand, if the material is packed very tightly in the container and there is very little air and moisture entering the system, it can sometimes happen that such purging may be actually dispensed with for long periods of time or only infrequently used because until the dilution of the nitrogen becomes excessive slight contamination will frequently not be importantly deleterious.

In view of the fact that under many circumstances a plurality of vessels will be undergoing chilling at the same time it will be necessary to associate with a single source of cooling liquid and with a single mechanism for recovering and reliquefying the gas, a plurality of channels for separate control of supply of liquid to separate chill boxes, purging separately the chill boxes and separate return to the system of the gas from each chill box.

My invention is illustrated more or less diagrammatic-ab ly in the accompanying drawings, wherein Figure l is a flow diagram of one exemplification of my invention;

Figure 2 illustrates a part of a modified flow sheet;

Figure 3 is a diagrammatic vertical section through the chill box and a bubbling superheat eliminator;

Figure 4 is a section along the line 44 of Figure 3.

Like parts are indicated by like characters throughout the specification and drawings.

In most instances in the drawings, while obviously insulation is required, since we are dealing with exceedingly cold fluids and gases, the insulation has been omitted from the drawings in the interest of clearness.

The chill box which contains foodstuffs or other cargo to be chilled is illustrated at 1. An insulated storage container 2 is adapted to hold a substantial amount of a cold S atom ice boiling liquid such for example as nitrogen in liquid phase, liquid air, or other suitable liquid gas, at a pressure of say 31.8 p.s.i.a., and temperature approximately -300 F. or the saturation temperature of the gas or gas mixtures used. A discharge duct 3 leads from the tank 2 to a coil 4 in a sub-cooler or super-heat suppressor 5 for the return gas. A duct 6 leads from the coil 4 to a manually actuated transfer valve 7 which may be set to open or shut posiiton and which when open will permit discharge of liquid through the duct 8 at a pressure of l p.s.i.g. and temperature of -309 or the saturation temperature of the gas or gas mixtures used to a closed insulated auxiliary tank 9 provided with a filler valve 10 through which additional liquid or liquid from another source may on occasion be supplied to the system.

The vessel 9 discharges through a duct 11 into the container 1 where the cold boiling liquid is brought into contact with the contents thereof, whereby the latent heat of evaporation supplied to boil the liquid is absorbed from the cargo. The resultant gas as it is evolved is discharged from the chill box through the duct 11a to coil 12 in the sub-cooler.

The duct 13 leads from the coil 12 to the coil 14 in the first pre-cool heat exchanger 15. The duct 16 leads to the coil 17 in the second pre-cooler 18 and duct 19 leads thence to the booster pump 20. Because of the pressure drop in the system between the container 1 and the booster pump 20, the pressure of the gas as it reaches the booster pump will be in the order of 6 p.s.i.a. This is the only area in the system where pressure is below atmospheric and it can be controlled to prevent ingress of atmospheric air to the closed system.

The booster pump 20 discharges the gas through the duct 21 to the multi-stage recycle compressor 22 at 15.7 p.s.i.a. A gas holder 23 floats, by duct 24 on the line 21. It may, for example, be of flexible rubberized fabric, be collapsible and have adequate volume at 1 p.s.i.g. for flow stabilizing purposes or a conventional type of expansible gas-holder may be used.

The recycle compressor 22 multi-stage with inter and after coolers not shown discharges gas at a higher pressure, for instance, 2500 p.s.i.g. and approximately 70 F. through the duct 25 to an oil filter 26. Duct 27 leads to coil 28 in the second pre-cooler 18. There the gas is cooled by heat exchange with the cold gas on its way to the booster pump through the coil 17.

Duct 29 leads from the coil 28 to the coil 30 in the refrigeration cooler 31 Where the gas is further cooled by heat exchange with suitable refrigerant in coil 32 supplied through the ducts 33 from a refrigerating system not here illustrated. The gas discharged from the coil 30 through the duct 34 is at a reduced temperature, say --40 F. and approximately 2500 p.s.i.g.

The duct 34' leads to coil 35 in first pre-cooler 15. Duct 36 leads from coil 35 to the Joule-Thompson expansion valve 37 where it expands and is discharged through the duct 38 at 31.8 p.s.i.g. and at saturation temperature for the gas employed say, -300 F. to tank 2. That part of the nitrogen which is liquefied remains inthe storage tank 2, the unliquefied gaseous phase nitrogen passes through the duct 39, controlled by the pressure relief valve 40, through duct 41 to the coil 14. The cold nitrogen in gaseous phase from the tank 2 is there mixed with the nitrogen in gaseous phase from the container on its way to the booster pump 20. The pressure in the tank 2 is maintained at 31.8 p.s.i.a. by the pressure relieve valve 40 set to maintain 31.8 p.s.i.a. in tank 2.

Some of the gas in duct 34 passes through the duct 42 for example at 2500 p.s.i.g. and -40 F. to the expansion engine 43 where it expands to the order of p.s.i.g. and a temperature of 265 F. Exhaust from expansion engine 43 passes through the duct 44 to the parallel Oil.

filters 45 thence through duct 46 to the pressure relief valve 47 set at p.s.i.g., downstream to discharge at atmospheric pressure to the duct 48 whence it joins the stream of gas on the way to the booster pump 20, through the first precooler 15.

A manually controlled valve 49' in the duct 11 immediately upstream from the container 1, may be set at on or off position. 49a is an automatic pressure controlled valve set to maintain the desired pressure within the cold box 1 when the valve 49 is opened. 50 is a three position manually controlled valve tin the duct 11a immediately downstream from the container 1. In one position gas may be conducted from the chill box through the duct 11a to the coil 12 in sub-cooler to enter the system through duct 13. In another position, the duct 11a to the sub-cooler 5 is closed by valve 50 and the gas contaminated nitrogen from the chill box is discharged to atmosphere.

Referring particularly to Figure 2, which shows a modified form of flow sheet, the discharge duct 3 leads to a transfer valve 60 which discharges through the duct 61 to the bubbler 79. The discharge duct 11a controlled by the three position valve 50 leads from the bubbler 79 to a coil 62 in receiver 2, whence a duct 63 leads to duct 41 just as in Figure 1. In this respect the difference is that the heat exchange between the liquid nitrogen on its Way to the chill box and the gas on its way to reliquefaction instead of taking place in the super heat suppressor 5 takes place within the storage container or receiver 2; Aside from that the operation is the same except that make up liquid nitrogen may be added through the line 65 controlled by the manually actuated valve 66 to the receiver 2.

In this arrangement the liquid at pressure for example 31.8 p.s.i.g. in the receiver 2 is discharged through the ducts 3 to the transfer valve 60 and ducts 61 to the food chill box, dropping substantially to atmospheric pressure and temperature for example 320 F. or at the saturation temperature at the pressure specified as it enters the food chill box. In this arrangement it can well happen that the nitrogen from the chill box having passed through the coil 62 will be discharged to duct 41 before it reaches the first pre-cooler at substantially atmospheric pressure and a temperature to the order of -295 F.

In a further modification such as is set out in Figures 3 and 4, I have shown in detail the chill box. The food chill box has an outer wall 70, innerlining 71, insulation 72, is open at the top and adapted to be closed by a removable cover not here illustrated. After the foodstuffs or cargo as indicated at 73 have been placed in the chill box and they may be at room temperature or frozen as the case may be and air and moisture will be found in the chill box, the blanket, mattress or sponge 74 is placed over the filling opening at the top of the container, resting on the food and encompassed by inner container lining 71 and on the contents and leaving a relatively small plenum chamber above the blanket or sponge. Then the filling hood 75 is placed over the open side or mouth of the container and this filling hood carries the grid 76 which overlies the sponge or blanket 74 and carries also the gas pipe 77 enclosing the liquid supply pipe 78 generally concentrictherewith. The liquid supply pipe 61 enters the bubbler box 79 being controlled by a float valve 80 and discharging liquid nitrogen adjacent the bottom of the bubbler box. The gas duct 77 enters the bottom of the box, extends through a goose neck 81 to discharge adjacent the bottom of the box. Thus the discharge end of the gas duct 77 is always immersed beneath the level of the liquid and a supply of liquid is always present within the bubbler box. The liquid duct 78 has a valve and a branch 82 adjacent the bottom of the box and a branch 83 ad jacent but just below the upper level of the box so that by this arrangement when liquid enters through the duct 61 and fills the bubbler box, a liquid bath is provided and the liquid passes through the outlets 82 and 83 for discharge through the grid 76 and thus saturates the blanket and as supply continues, liquid flows from the saturated blanket down along the surfaces within the chill box. The gas evaporated by the heat of the material in the chill box passes back in counter current through the saturated blanket, being in intimate contact with the liquid, passes out through the duct 77, bubbles through the liquid supply in the bubbler 79 and is discharged through the duct 11a controlled by valve 50 for reliquefaction.

The use and operation of my invention are as follows:

Starting with valves 49 and 50 closed, no liquid is discharged from tank 2 and none from intermediate tank 9. No gas enters the system through the duct 11, all the liquid in storage tank 2 stays there and the gas in gaseous phase from storage tank 2 is recirculated.

Ducts 11 and 11a are connected to a chill box 1. Valve 49 is opened to permit liquid to enter the container and valve 50 is set to permit purging if desired to atmosphere. When nitrogen in gaseous phase has filled the chill box, valve 50 is set to permit the gaseous nitrogen to enter the system through duct 11a, coil 12 and duct 13. When sufficient nitrogen has been supplied to the container, and has evaporated and lowered the temperature of the contents to the desired point, valves 49' and 50 are closed so that container may be detached.

The result of this is that a certain amount of nitrogen from the system is bled ofi? to atmosphere and a certain amount of nitrogen in gaseous phase is left in the container after it has been disconnected. This will result in a gradual diminution of the nitrogen in the system and may be compensated for by closing the valves 7 and 49 and opening the supply valve 10 to permit the supply of additional liquid or gaseous nitrogen to tank 9 at atmospheric pressure. Thereafter, valve 10 may be closed, the valves 7 and 49 opened and operation continued.

When the container 1 is out of circuit, the compressors 20, 22 and the expansion engine 43 may continue to operate. Any resultant change in the capacity of the system at any point is adequately compensated for by expansion and contraction of the gas holder 23. The same situation prevails when the auxiliary tank 9' is opened to atmosphere to permit introduction of liquid or gaseous nitrogen to replace the loss.

For illustration I have shown but a single chill box in the system. Such a box may be disconnected therefrom when the contents are chilled and may be replaced by another box. Under other circumstances, a plurality of such boxes may be on the line at any time either starting and stopping their cooling simultaneously or at different times, as the case may be. If but a single container is on the line, the purging valve 50 may be operated at the beginning of the cooling cycle when the liquid begins to enter the box. If a plurality of boxes float on the line a separate purge valve for each will be necessary.

If but a single box is filled at a time the discharge of liquid thereto and the gas therefrom will be discontinued as the change is made and during that time the circulation of liquid and gas reverts to the liquid receiver 2. If a plurality of boxes are being cooled at the same-time and taken on and off the line at different times, the supply of liquid thereto and return of gas therefrom to individual boxes may change the time and amount but there will always be a discharge of liquid to a box or boxes and return of gas from box or boxes. In either event, the demand for liquid nitrogen or other liquid coolant 'will be a variable one and the booster pump and the recompressor will be controlled to vary their output in consonance therewith. The automatic mechanism to bring about such control is not here illustrated in the interest of simplicity but suitable control mechanisms will be in the system. The only result of ceasing the discharge of liquid from tank 2 as chill boxes are being connected or disconnected will be to momentarily increase the amount of liquid retained therein. Any reduction in the amount of gaseous nitrogen between storage tank 2 and compressor 22 will be adequately compensated for by the expansible gas holder 23.

The pressures and temperatures set out above are purely illustrative and pressures and temperatures characteristic of the operation may be varied depending upon design of the system except that the pressure in the container 1 must be always slightly above atmospheric pressure to insure that any leakage from the container or from the removable connections between the container and the system will be out rather than in so that no warm air will be drawn into the system.

When it is desired to renew the supply of liquid nitrogen and valve 7 is closed and valve 10 is opened, the slight loss in pressure downstream from valve 7 will be of no consequence and immediately compensated for or replaced as soon as the system goes back into operation. All the other pressures and temperatures are a matter of design depending upon the capacity of the plant, the speed at which the chilling is to take place and the size of the containers in which chilling is to be accomplished.

Cooling of the contents of the container is accomplished by the vaporization of the cold boiling liquid or nitrogen and the gas evolved as the latent heat is supplied from the food or cargo being cooled, is discharged with maximum rapidity from the container and recycled so that the recycling and liquefaction of the nitrogen is not burdened with the necessity of removing higher boiling point diluents and the real liquefaction begins substantially at the minimum temperature so that what the system has to do is to take gas which is already substantially at the liquefaction point for the pressures involved and reliquefy it.

The operator by manipulating the valve 7 can adjust the rate of flow of liquid nitrogen to the chill box. The rate of flow of gaseous nitrogen from the chill'box for reliquefaction will depend on the rate at which the liquid is supplied to the chill box and the rate. at which the liquid boils. As temperature of the contents of the container falls, the boiling rate may also fall and this may reduce the volume of gaseous nitrogen in the system. This is compensated for by the operation of the gas-holder 23.

Nitrogen is a convenient cold boiling liquid for use in a system such as this but other cold boiling liquids can be used and where I have used the term nitrogen I have used it as illustrative of cold liquids which can be brought in contact with the foodstuffs without deleterious effect and which may be liquefied, evaporated and reliquefied under similar circumstances.

I have from time to time in the specification set out specific temperatures and pressures. These are, of course, entirely illustrative and many combinations of temperature and pressure can be used. There is a definite advantage in operating so far as the food chill box or cargo is concerned at substantially atmospheric pressure. Otherwise the box must be heavy and strong and expensive if it is to stand pressures above atmospheric. If atmospheric pressure is all that is involved, then the box may be designed for stiffness and strength sufiicient to be handled and carry its load only.

Under some circumstances it may be possible to dispense with the bubbling heat exchange between the gas and the liquid designed to minimize or suppress super heat. Theoretically perhaps if the gas could rush out fast enough, there would not be time for any temperature rise after boiling. As a practical proposition this is hardly likely to be brought about and therefore the bubbling arrangement first through the mattress and then through the bubbling tank makes it possible to suppress to a sufficient extent super heat which would otherwise mean a wasteful operation. Obviously only the mattress might be used without the bubble box or under other circumstances the bubble box might be used without the mattress. Under some circumstances only the super heat suppression of Figure 1 or 2 would be sufficient.

I use the word ambient at atmospheric immediately surrounding the box being chilled.

The foodstuffs or other cargo will usually be packed in cartons or wood boxes, the individual packages perhaps being in paper cartons or tins, as the case may be, but always under ordinary circumstances the material which is to be chilled will be enclosed in a porous or absorptive box non-leak proof which may be as above indicated of wood fibre or paper and even though the packages may be packed very closely together the liquid coolant what-' ever it may be will be free to penetrate and be absorbed by this material and passed through to come in very direct contact either with the foodstuffs themselves or any small leak-proof container which may hold them so that the liquid comes into the most intimate chilling contact with the material being chilled, whereby rapid chilling resulting from rapid heat transfer will always take place as a result of the fact that the foodstuffs being chilled immediately supply latent heat of evaporation to the liquid itself.

By my arrangement, it thus becomes possible to charge the cold box with the material to be chilled in a working area exposed to normal ambient temperatures. To chill the material in such an area and later store, ship and unload the material under continued normal atmospheric temperature conditions. Thus the workmen are never exposed to the low temperature and the material after it has been cooled is never exposed to high temperatures until it is unpacked, treatment or other use.

I claim:

1. Means for supplying a cold boiling liquid to an insulated chill box which is apertured for loading including, a liquid pervious absorption pad closing said aperture, a removable cover for the container independent of and above the pad, means for supplying a cold boiling liquid to the pad to saturate it with resultant flow of liquid from the pad across the surfaces of the contents of the container, means for positively withdrawing gas evolved in the container through the pad in counter current constant direct contact with the liquid in the pad.

2. Means for supplying a cold boiling liquid to an insulated chill box which is apertured for loading including, a liquid pervious absorption pad closing said aperture, a removable cover for the container independent of the the pad, means for supplying a cold boiling liquid to the pad to saturate it with resultant flow of liquid from the pad across the surfaces of the contents of the container, means for positively withdrawing gas evolved in the container through the pad in counter current constant direct contact with the liquid, means for reliquifying the gas after such withdrawal for reuse in the container.

3. Means for supplying a cold boiling liquid to an insulated chill box which is apertured for loading including, a liquid pervious absorption pad closing said aperture, a removable cover for the container independent of the the pad, means for supplying a cold boiling liquid to the pad to saturate it with resultant flow of liquid from the pad across the surfaces of the contents of the container, means for positively withdrawing gas evolved in the container through the pad in counter current constant direct contact with the liquid, means for bubbling the gas after it has passed through the pad through a bath of the cold boiling liquid. I

4. In a refrigeration apparatus, a circulation system including in series a receiver adapted to contain a body of a cold boiling liquid, a valve controlled liquid duct discharging from the receiver, a heat exchange coil within the receiver in contact with the liquid therein, a valve controlled gas supply duct communicating with said coil, a portable chill box adapted to contain material to be chilled, means for selectively closing a circuit between the liquid discharge duct and the gas supply duct and any one of a plurality of such chill boxes.

5. In a refrigeration apparatus, a circulation system including in series a receiver adapted to contain a body of a cold boiling liquid, a valve controlledliquid duct discharging from the receiver, a heat'exchange coil within the receiver in contact with the liquid therein, a valve controlled gas supply duct communicating with said coil,

a portable chill box adapted to contain material to. be

chilled, means for selectively closing a circuit between the liquid discharge duct and the gas supply duct and any one of a plurality of such chill boxes, a liquid pervious staurable pad in the chill box interposed between the conections to the two said ducts and the contents of the chill box.

6. In a refrigeration apparatus, a circulation system including in series a receiver adapted to contain a body of a cold boiling liquid, a valve controlled liquid duct discharging from the receiver, a heat exchange coil within the receiver in contact with the liquid therein, a valve controlled gas supply duct communicating with said coil, a portable chill box adapted to containmaterial to be chilled, means for selectively closing a circuitbetween theliquid discharge duct and the gas supply ductand any one of a plurality of such chill boxes, abubble bath interposed between the receiver and'the chill box wherein the gas on its way to the heat exchange coil bubbles through the liquid which is currently flowingto the chill box.

References Cited in the file of this patent UNITED STATES PATENTS 1,933,257 Goosmann Oct. 31, 1933 1,944,857 Atwell Jan. 23, 1934 2,068,677 Higham Ian. 26, 1937 2,137,902 Walter Nov. 22, 1938 2,447,249 Hill Aug. 17, 1948 2,502,527 McFarlan Apr. 4, 1950 2,618,939 Morrison Nov. 25, 1952 2,631,439 Feigenbaurn Mar. 17, 1953 2,715,323 Johnson Aug. 16, 1955 2,812,643 Worschitz Nov. 12, 1957 2,889,689 Morrison June 9, 1959

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