US2550935A - Method and system for refrigeration of railroad cars - Google Patents

Description

R. D. PIKE May l, 1951 METHOD AND SYSTEM FOR REFRIGERATION OF' RAILROAD CARS Filed Feb. 18, 194B l f /f /f /f/ f /N/U/ foods4 Patented May 1, 1951 OFFICE METHOD AND SYSTEM EOR REFRIGERA- TION' OF RAILROAD' CARS RobertD; Pike, Greenwich, Conn. ApplicationV February 18, 1.9.48,Serial No. 9,053

3' Claims.

The present inventionelates to` a cooling system for and a method of cooling a refrigerator car, and more particularly to a cooling system and methodlin which refrigeration is providedl by sublimation of solid carbon dioxide, or Dry Ice, inconj unction withwaterice.

An object of the present invention is to provide general vpurpose refrigeration for railroad cars for the' shipment principally of freshy fruits and vegetables wherein a non-freezing refrigerating temperature is desired, and in which the main sourceof 'refrigeration is-derived from the sublimation yof 'DryIce.

Another-object of the invention isto` provide a system for cooling at refrigerator car by which air circulated in the car is cooled by contact with water ice causing the latter tomelt thereby limit,ingthe` v minimuxnair-l temperat'ureto 32 F., and reducing' the normal rate ofl meltingof the-Water icea-by-fthesublimation of solid carbon dioxide', the-.system beingv adapted' tominimize the rate of? sublimation of the solid carbon dioxide,` so thatlsome water ice-.will alwaysmelt and'so that a single icing ofthe refrigerator car will be sufcie-nt. forl seven to ten dayswhile'maintainingY a noir-f"Y ing: refrigeratingz temperature ofthe sfintthecar;

Astillgfurther object of the invention is to provide Aa refrigerati-ng system yutilizing a refrigerat ing `medium comprised off'a l combination of solid carbon-dioxide and water iceand in whichsystem air may-'circulate by gravityfor by force into contact with the` refrigerating medium, the path of the'gravity circulation being substantially solely connedctocontact with thewaterice While' the path of forced circulation is to asubstantially greater degree in heat exchange relation with the solid-#carbondioxideas well as-in heat exchange relation with thewater ice.

Af further-object is lto provide split, or ltwo compartment bunks, on each end ofthe car, the compartmentsof each bunker being separated by an insulated Awall running across the car and utilizing thel two compartments at the ends 0f the car which are most remote from the goods inY the car; for -the'storage of Dry Ice.

Other objects and advantages of my invention will become apparent from the following description of a preferred form of the invention, reference-being made to the accompanying drawings wherein:

Fig. l is a fragmentary, vertical longitudinal section throughthe center line of-'a railway car, only one end of which car is shown;

Fig- Zisaviewinv section-taken-von the line 25T-Former 1;- andi-y;

Fig. 3 is a View in'section taken online'3-3'of Fig. 1'.

In the drawings l0, l-l, lf2 and l'3 represent the end walls, roof, floor and side walls; respectively; ofv aninsulated railroad' car` whichv may" be of standard construction in` this respect: The` structures at oppositeends' of the car are identical and therefore only one such structure is' shown and described. Each end of the caris provided with an icebunker which is formed by a `bulkhead I4 spaced from the end wall ofthe car. The upper portion of the bulkhead is open' for the passage of air and louvers I5V areprovided for distributing the air into theupper portion of the goods storage space, indicatedv at C; The

lower edge of the bulkhead is' spacedfrom the"- car floor to form an air passage therethrough as indicated at I6. A perforatedfooringl I1, which` may be in the form of gratings, is provided 'above floor l2 and extends throughout thev car inter` mediate the bulkheads M and this flooring supi' ports the load in the car and provides an air pas#A Sage beneath the load leading to the openings l 5. The perforations in the flooring permit passage of. air through the-bottomlofthestorage spaces throughout the latter; Afan I8 is disposed at each endof the car beneath-flooringfl'l" for forei4 ing air towards the ends of the-car through open# ing I6. Preferably, the fan'is driven by the car axles through belts, not shown, and operate only'y When the car moves;

The bunkers are each divided into two com` partments Bll and B2v bya vertically extending. wall 20 which extends transversely of the car: Preferably, the wally 20- is-formed`of a steel plate 2l lhavingI two inches of high grade thermal in` sulating` material 22 attached'to the surface.

The -inside side surfaces offcornpartment B1 areV covered Withplywood, asD shown atf23, for protecting the insulating material. The compart-v lice; and-compartment B2, which isl adjacentV to they storage space C is adapted to receive water' ice'. The two ice compartments can loel filled' through a hatch 25 in the top `of the car, the top' of the wall 20 terminating short of 'thehatch to' provide-aecessto both compartments. A screen 26 is hinged to the top Vvof the wall 20 and this screen may be swung from one side to the other" of the hatch for directing ice into eithercom`` partment, as desired. y

The bottom wall 21 ofthe Dry Ice` compartment B1is formed of-'heat-conductingJ material',

such" 'asia '10'l gauge-'steel platewhich maybei'proi vided with heat transfer fins 28. The plate 21 is preferably supported about inches above the floor of the car which is well above flooring H.

A water ice grate 3d of usual well known design, forms the bottom of compartment B2 and it is supported at the same level as bottom plate 21. The load of water ice in the compartment B2 is kept at least about two inches away from the bulkhead by the usual Well known ice screening 3i, which extends vertically from g-rating 30 to the top of the car and transversely of the car and which maintains a minimum vertical air passage between the water ice and the bulkhead I4.

A horizontally extending plate 33 extends from the lower edge of the bulkhead It toward the near end of the car and it projects slightly less than half the distance from bulkhead lil to wall 20 of compartment B2. The plate 33 extends the width of the car and it serves to direct the impelled air from fan i8 toward the end of the car beneath the bottom wall 27 of the Dry Ice compartment B1 and along the bottom of compartment B2 and upwardly between the water ice and bulkhead it. When the air flow is in the reverse direction, the plate 33 will permit substantially all of the air flow to bypass the bottom of coinpartment B1 and flow from the water ice directly into the goods storage space. This occurs because the flow of air is by convection and the velocity is not sufficient to impel the air flow beneath the Dry Ice compartment.

In practice I usually ll the Dry Ice compartment B1 with pulverized Dry Ice, usually about 2,750 pounds per compartment, or 5,500 pounds per car, but I may use less when the average outside temperature falls below the maximum sum mer average, as in the spring and fall. This Dry Ice is pulverized in a manner similar to that sometimes employed with water ice and blown into the compartment. I may then close the compartment with a cover, not shown, which may have a pipe connection to bleed the CO2 out of the car, or merely a vent to allow it to escape into the car, as may be preferred. I then move the screen into place, as shown, for filling line B2 with water ice and then ll this bin to the level of the bottom of the hatch coping with about 3,700 pounds coarse water ice. It will be observed that both the water ice and Dry Ice are loaded r through the top hatches of the car. l I-Iowever, in some cases, I may find it more convenient to iirst load the water ice compartment with water ice at the time the car is loaded, thence moving the car to a Dry Ice depot, filling the Dry Ice compartment and refilling the water ice compartment to its full capacity as may be indicated.

When the car is in transit the fan it is actuated by the axle and it withdraws air from the bottom of the goods storage space and from side wall lues, not shown, if installed and biows it as indicated by the full line arrows underneath baiile 33. The inertia of this air stream causes it to strike the end wall of the car, whence it is diverted upwardly into contact with the heat transfer plate 2l under the Dry Ice compartment, beneath the water ice compartment, upwardly between the water ice surface and bulkhead ls and into the upper part of the goods storage space from where it is drawn downwardly through the goods, cooling the latter.

The plate 2 rapidlybecomes covered with a layer of water ice, or frost, which reduces heat transfer into the Dry Ice, thus tending to reduce its rate of sublimation. This end is further aided by the relatively small area of the plate, which is only about 10 sq. ft. This reduction of the rate of sublimation of the Dry Ice tends to increase the meltage of water ice, thus insuring that the contact surfaces between the circulating air and the water ice shall always be at the true freezing point, or 32 F.

After the car has been in service a few hours, the water ice in compartment B1 becomes tightly frozen against plate 2| by the passage of heat into the Dry Ice through the insulated partition wall 2i), and furthermore, meltage within the water ice becomes frozen to such an extent aided by the deposition of frost that most of the ow of air is constrained to pass between vertical surfaces of the water ice and the inner surface of the bulkhead I4. At rst this flow occurs necessarily in the 2-3" space back of screen 3l, but as meltage proceeds the face of the water ice remains substantially vertical and recedes from the screen, as is illustrated in Fig. 1. Thus most of the meltage of water ice is caused by the passage of the air over this vertical surface of the ice and as all of the air does so pass, it is continually in contact with surfaces which are necessarily at a temperature of about 32 F. The result of this is that the air maintains a minimum temperature in the goods storage space of about 233-35o F. when the fan is operating.

When the fan is shut off for any reason, the direction of the air reverses itself and becomes downstream, flowing by the vertical water ice surface, thence around the baffle 33,r which is made short so that a substantial portion of the air will by-pass the plate 2l, which would otherwise tend to cool it below 32 F. This i'low of air is indicated by the dotted arrows. The transfer of heat from the very small portion of naturally ncwing air which may come into contact with plate 2l is greatly impeded by the layer of frost on this plate. Thus, air entering the goods storage space through the floor by convection will be in the neighborhood of 32 F., but no lower.

Because the major flow of air through the car occurs only with the fan on, the conditions then prevailing are the ones which mainly determine the satisfactory operation of my system. However, I have shown that even when the fan is off, the air which ilows by natural circulation and in relatively Small volume is diverted away from surfaces cooled by Dry Ice.

An example of the operation of my system is outlined hereinafter from conditions which prevail-ed during a test of a refrigerator car embodying my invention.

Speed oi car 30 miles per hour Duration. of time when observations were made 62 hrs. Approximate movement of airv by two fans per car 2200 c. f. m. Maximum temperature of air averet l2 points in the car 35.6 F. Minimum temperature of air average at l2 points in the car 34.7 F. Average temperature of air at l2 points 35.3 F. Water ice meltage, pounds per hour,

per car 6.5 Water ice placed in bunkers at start 7400 lbs. Life of water ice based on 25% consumption 285 hrs. Life of water -ice based on consumption 1140 hrs. Dry Ice placed in bunkers at start 5500 lbs.

Dry Ice sublimation, pounds per hour, per car 27.8 Life of Dry Ice based upon 100% consumption 198 hrs. Water ice equivalent of Dry Ice,

pounds per hour per car 53.1 Total hourly ice consumption,

pounds equivalent water ice, per

hour per car 59.6 Type of car insulation Standard Maximum outside temperature during test 95 F. Minimum outside temperature 59 F. Average outside temperature 74.5 F.

across the continent without re-icing; alsofthe very small difference between maximum and minimum temperatures in the air in the car prove that enough water ice melts to control the temperature at a desired level between 3040 F., neither high enough to cause deterioration of the goods, nor low enough to cause them to freeze.

Although I have described but one form of the invention, it is to be understood that other forms might be adopted, all falling within the scope of the claims which follow.

I claim:

1. A refrigerated car comprising in combination, a compartment providing a food storage space; a bunker at one end of the compartment, said bunker being open to the compartment at top and bottom and having a partition ther-ein di- Viding the bunker into two contiguous ice storage bins, said bins having the bottom walls thereof spaced from the floor of the car, the bottom wall of the bin remote from the compartment being of heat conducting material and adapted to support Dry Ice; a perforated wall spaced from the bunker wall adjacent to the compartment for forming a water ice retaining wall in the bin adjacent to the compartment and providing an air passageway along the side of the last mentioned bin and said bunker wall leading from the bottom of the bin to the upper opening in the bunker; baffle means forming an air passageway leading successively from the bottom of the compartment through the lower opening of the bunker, into heat exchange with said bottom wall of the remote bin, under the bottom wall of `the other of said bins, and to said air passageway; and blower means for forcing air through the passageway in the upward direction. f

2. A refrigerated car comprising in combination, a compartment providing a food storage space; a bunker at one end of the compartment, said bunker being open to the compartment at top and bottom and having a vertical partition therein for dividing the bunker into two ice storage bins, said bins having the bottom walls thereof spaced from the floor of the car, the bottom wall of the bin remote from the compartment being of heat conducting material and adapted to.support Dry Ice; a vertical perforated wall spaced from the wall of the bunker wall adjacent to the compartment for forming a water ice retaining wall in the bin adjacent to the compartment, and for providing a minimum verticalv air passageway along the side of the last mentioned bin and said member leading from the bottom of the bin vto the upper opening in the bunker; a baille plate extending into the bunker from the bottom opening in the bunker and parallel to the bottom of the last mentioned bin and intermediate the floor of the car and said bottom for forming an air passageway leading from the bottom of the compartment to beneath the ice bins and reversing to traverse said bottom wall of the remote bin and the bottom Wall of the other of said bins, and to said vertical air passageway; and blower means for forcing air through the passageway in the upward direction.

3. A refrigerated car comprising in combination, a bulkhead extending transversely of the car adjacent one end thereof for defining a bunker area, said bulkhead being open at the top and bottom thereof; a vertical partition parallel to the bulkhead and dividing the bunker area into two ice refrigerant storage bins extending transversely of the car, said bins having the bottom walls thereof spaced from the floor of the car, the bottom wall of the bin adjacent the end wall of the car being of heat conducting material and adapted to support Dry Ice and the bottom wall of the other bin being perforated to permit passage of air therethrough; a vertical perforated wall spaced from the bulkhead and in the bunker for forming a water ice retaining Wall in said other bin, and for providing a vertical air passageway along the side of the last mentioned bin leading fromk the bottom of the bin to the upper opening in the bulkhead; a baille plate extending into the bunker from the upper edge of the lower opening in the bulkhead and parallel with the ear floor and intermediate the car iloor and the bottom of said other bin; and blower means for forcing air through the lower opening in the bulkhead into the bunker area and beneath said baiiie plate.

ROBERT D. PIKE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,043,163 Goosman June 2, 1936 2,109,310 l Cordrey Feb, 22, 1938 2,180,510 Dietrichson Nov. 21, 1939 2,313,120 Bonsall Mar. 9, 1943

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