DE1958348A1 - Method and device for spray cooling - Google Patents

Description

PATENT Attorney DIPL.-INQ. QERHARD SCHWAN 19583 4 I MUNICH I QOERZER STRASSE 15

UNION CARBIDE CORPORATION 270 Park Avenue, New York, NY ₀ 10017, V.St.A.

Method and device for spray cooling

The invention relates to a method and a device for spray cooling what frost-sensitive goods, in particular transport goods, with the help of a low-boiling liquefied gaso

The cooling of perishable goods by spraying a cold cryogenic liquid from a container for liquefied gas into the goods storage chamber is, as can be seen from US Pat. No. 3,287,925, used on a large scale in practice the material is sensitive to frost, this uiie with fresh material, for example, _o lettuce, is the case, it must be kept within a relatively narrow temperature range of about 0.5 ⁰ C to 10.0 ° C, and when it is important, such Cools well for extended periods of about 48 hours. Fresh goods generate their own heat due to respiration, which must be dissipated by the cooling system together with the atmospheric heat, which inevitably passes into the goods storage chamber

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exceed about two days, only to be worried when maintain uniform storage temperatures amrd & n, which are often close to the freezing point of the good. Actual freezing, on the other hand, must be avoided as it usually occurs results in complete spoilage and makes the goods unsaleable «,

One such problem is variations provide Guttamperatur within the Spsichsrkammer represents "For example, let the spray cooling of lettuce Rait using flössigem nitrogen and of an over-head, 11.3 m long spray head with a thermostat setting of 1.7 ° C The regarded in U.S. The system described in patent specification 3,287,925 often results in undesirably large temperature gradients between the top and bottom of the chamber, for example 2.8 ^° C. at the ^{top and 10.0 °} C. at the bottom Spray line, a larger amount of coolant is simply introduced, because this would result in frost damage in the upper part of the cut charge, without the lower parts being adequately cooled The coolant spray jet exiting openings directly hits the upper layer of the the boxes or crates containing the goods on ο The problems cannot be solved by the fact that refrigerants are "• fed" directly into the bottom of the ksaags, because this is Frostechädsn; Good at

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- 3 -sam area resulted.

The invention is based on the object of creating an improved system for spray cooling of frost-sensitive material using a cryogenic liquid. In particular, an improved apparatus for spray-cooling of frostempfindlichem Good to transport mährend be created, the ε for one of the top to the bottom of the product storage chamber relatively uniform temperature with an adjustable Ulert of about 0.5 to 10.0 ° C ensures ^0.

Further objects and advantages of the invention emerge from FIG following disclosure and claims.

The invention relates to a device with a container for receiving a low-boiling liquid refrigerant such. B. liquid nitrogen, an outlet line connected to the container and an overhead line connected to it, the openings, which are preferably distributed in the longitudinal direction, for spraying the coolant into a at a temperature between approximately 0.5 ° C and 10.0 ⁰ C has to be held good storage chamber. According to the invention, a liquid outlet line connected to the container and a liquid evaporator line connected to the liquid outlet line are provided, which in the lower part of the

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Good storage chamber is arranged and extends essentially over the full length thereof. Furthermore, the liquid evaporator line is surrounded by thermal insulation, the quality of which is sufficient to keep the thermal conductivity value (to the refrigerant) at 4.1 to 24.8 kcal / hm line length in the heat transition relationship »The metallic floor extends over at least part of the length and at least part of the width of the material storage chamber _{or the like}

In a preferred embodiment, gas passages extending over its length are also arranged in the lower part of the material storage chamber, which are in heat exchange with the UJärmeisolierung and the thermally conductive metal base and whose opposite ends are in open connection with the gas space of the material storage chamber metallic bottom formed by a flat plate "According to a further embodiment, metal channels extending from end to end are provided in the lower part of the material storage chamber, which are adjacent to the metal bottom." In this embodiment, a first group of channels forms the gas passages and is the liquid evaporator line housed in a second group of channels. The above-mentioned thermal insulation fills the space between the outer wall of the liquid evaporation line and the walls of the second group of channels. A flat metal plate connects the lower ends of the channels and is sufficient as a more heat-conductive one

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** "% j ™

Metal floor over the wool length and width of the storage ■ chamber,

According to the method according to the invention, heat is transferred through solid luarmelsitung from UBT bottom material layer to the above-mentioned metal base and then from this ai? F a Uförffie insulation ^ which extends in the longitudinal direction of the ridge below the bottom layer of material and surrounds the evaporator pipe for the liquid cold carrier Heat insulation does the heat through solid heat transfer on the evaporator line and then through convection on the liquid evaporating in the line. Refrigerant transfer "Dia heat transfer sufficient to u'nterste the layer of material of ends to the end chamber is at a temperature to keep the slide ₉ Kammargastemperatur determined won not more than 2.8 ⁰ C abtuBichto In a preferred embodiment of the process of cold gas within Uiird Dar Gutkammer in Konvaktionsaärme = exchange with the goods constantly around them and then in convection exchange from end to end with the metal base underneath the lowest layer of goods after being heated by convection heat exchange with the warmer material in heat transfer zone with the metal base, this is followed by the previously described * successive heat transfers by solid heat conduction to the heat insulation and the evaporator conduit for

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the liquid coolant. Finally, the heat passes through Convection from the line to the liquid evaporating in it Transfer refrigerant «,

U / is described in detail below, the invention sins decisive l / urping paring of the good temperature- * .ρ-αη @> η the upper imo des? the lower part of the Gut "r achieved Zugleic ·, the device facilitates after Erfindjng DLT control of the cooling temperature to a predetermined ffisr-t over DSRA Gi friarpunkt that heiät a Tatuparatur ziBischsn about ü, ^Cs 5 C and 10.0? ⁰ C

The invention is in the following on the basis of exemplary embodiments explained in more detail in connection with the drawing »It shows; ·

Figure 1 is a schematic sectional elevation of a semi-trailer truck with a cooling device according to an embodiment of the invention,

2 shows in section a schematic elevational view of a modified embodiment with a Eisenbahnufagens UBt cooling device according to the invention _s

Figure 3 is a perspective view of a for the Aus » guide form according to Figure 2 suitable assembly, consisting of a single evaporator formed by channels, a üiärmaisolation and a

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■. - 7 conductive flat plate,

^F igur 4 in section an end view of a for the training

guide farm according to Figure 2 suitable construction ~ pe, consisting of a bottom evaporator with a higher plate and lower flange sections as well as from a thermal insulation, and

FIG. 5 is a graph showing a comparison the performance of the device according to the invention with a known spray cooling system enables.

Figure 1 shows an embodiment in which sin articulated lorries the heat-insulated storage chamber 11 for receiving frost-sensitive items A good 12, for example lettuce boxes stacked on top of one another, forms = the chamber can be used for mobile cooling chambers conventional structures have, for example, reinforced exterior walls clad with aluminum, clad with plywood Inner walls and one between the two walls Have foam insulation. The inner wall of the storage chamber is generally made of a material that does not conduct heat well. «The chamber is open to the outside air. - ^ included, but need not be airtight, uieil Z-J, rode, for example in the form of provided at the rear Doors (not illustrated), required to load and unload the Quv IT ^ i - !.

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OBlGlNAl.

19583 * 8

The storage chamber 11 is associated with a 13 doppeluiandiger _r uiärmeisolierter container for storage of stagnant, low-boiling, liquefied gas under pressure, which at atmospheric pressure a boiling point below about 28.9 ° C has ". The construction of such a container is known and shown for example in U.S. Patent No. 2,951,348 ,, the container 13, which is either cylindrical or rectangular, is shown within the storage chamber 11, but may _o be disposed outside of said chamber of the container 13 has an outer shell which completely encloses an inner storage vessel forming an evacuable insulation space. This space is preferably filled with a high-quality solid insulating material, for example in the form of alternating layers of radio-opaque barriers, such as aluminum foil, which are supported by poorly conductive fiber layers, for example glass fibers, are separated from each other. This particularly effective insulation is described in US Pat. No. 3,007,596. Other suitable insulation materials consist, for example, of layers of aluminum-coated polyethylene terephthalate.

In order to remove gases that collect in the evacuated isolation room, an adsorbent material, for example calcium zeolite A, or a getter material, for example powdered barium, can be "grounded"; this will result in a high

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19.5 a-3 4-8

'- 9 Maintain insulation quality *

Low-boiling, liquefied gases which are suitable for use as a cooling agent for the present invention, are gases whose boiling point at atmospheric pressure below about -28.9 ⁰ C ,, examples of such liquefied gases are liquid air, liquid argon, liquid carbon dioxide, liquid helium and liquid nitrogen. Liquid nitrogen is particularly suitable and is preferably used because of its chemical inertness and relatively easy separability from air. While specific reference is made below to nitrogen, it is to be understood that all of the above-mentioned gases and mixtures of these gases are applicable. Although the main function of the storage chamber-I1 is to cool the material 12, the liquefied gases preferably used, such as nitrogen, also provide the atmosphere within the chamber and provide an inert cover surrounding the material.

The vessel located within the storage container 13 is filled with liquid nitrogen in a known manner, for example by connecting a source of liquid nitrogen stored at atmospheric pressure to the container appropriate pump is used and additional heat is generally added to the pressurized liquid before

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19583A8

- ίο -

it is transferred in dan container 13 _e The filling and storing dea liquid nitrogen in the or "takes place in the container 13 preferably at saturation conditions and at temperatures corresponding to a vapor pressure of more than 0.7 kg / cm pressure, wherein liquid and vapor substantially are in equilibrium »If the high-quality insulation mentioned above is used, essentially no heat penetrates the inner storage vessel of the container 13 and the stored liquid nitrogen is only released through this charge vapor pressure be filled into the container 13 in the supercooled state. In such a case, means must normally be provided to build up sufficient internal pressure when the liquid is to be dispensed. This pressure can be supplied from the outside using a known pressure build-up coil noisy · the ambient air working evaporator and a line that returns the resulting steam to the (not shown) container gas space. According to a further known modification, a less high-quality thermal insulation material can be used, so that sufficient heat penetrates from the ambient air to evaporate so much stored liquid refrigerant that a gas pressure is created which ensures that the liquid is dispensed as required.

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- 11 -

Preferably, the liquid nitrogen cold carrier is at a Overpressure of less than about 7 kg / cm stored because at higher pressures, the openings in the spray line become inexpediently small. In addition, the time delay of known temperature sensors would make the removal of to regulate liquid secondary refrigerant in the required manner, The accumulator pressure is preferably above approximately 0.7 kg / cm to provide sufficient driving force for a substantially uniform distribution of the cold medium to ensure through the overhead spray openings. An overpressure in the storage tank of 1.0 to 1.5 kg / cm was found to be particularly suitable.

One end of a liquid outlet line 14 is connected to the Storage container 13 connected. In the line 14 is a Control valve 15 "The other end of the liquid outlet line 14 is associated with a liquid evaporator heat exchanger 16 connected, which is arranged in the lower part of the material storage chamber 11 and extends essentially over its full length. The heat exchanger 16 preferably comprises at least two sections. The first section 16a extends to the opposite one End of the storage chamber 11 to the area of the access doors, while the second section 16b to the area of the liquid storage container 13 returns lying chamber end «

The lines 16a and 16b are from a UJärmeisola-

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tion 17, the quality of which is sufficient to the UJärmeleitwert (heat conductance) to keep 4.1 to 24.8 kcal / h m line length »A thermally conductive metal base 18 is adjacent to the noise insulation 17 and is in a U / ärmexexchange relationship with it. The metal base 18 extends over at least part of the length and at least part of the width of the material storage chamber below the line 16 and UJärmeisolierung 17 existing assembly; it is illustrated as a flat plate. The cargo area 19 lies above that of the heat exchanger 16, thermal insulation 17 and metal floor 18 existing assembly; The item 12 sits on the loading area.

The vaporized and normally superheated gas that the heat exchanger 16 leaves, passes through an outlet 20, which is preferably is arranged in the upper part of the storage chamber 11, in the storage chamber 11. In this way, the remaining The cold content of this gas is utilized through contact with the stored material 12. To prevent excessive pressure build-up in To avoid the chamber, some of this gas can be discharged to the outside of the chamber 11 via a vent opening 20a. u / earth »The refrigerant gas emerging from line 16 can, instead of being introduced directly via the outlet 20, also upstream of the spray head arranged overhead the spray openings are supplied and through these openings pass through into the chamber 11.

One end of a fluid outlet line 21 is connected to the spa

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container 13 connected for liquid refrigerant. In the illustrated embodiment, the line 21 branches off from FIG Liquid outlet line 14 abj the line 21 can, however also reach into the container 13 separately. The other end of the line 21 is connected to an overhead spray line 22 connected, which extends essentially over the full length of the material chamber 11 and a sequence .von in the longitudinal direction has distributed openings 23, from which exits the coolant located in the spray line. the Openings 23 can be directed either horizontally or slightly downwards on the circumference of the line 22 and are preferred circular shaped to be a uniform symmetrical Ensure exit of the sprayed coolant. If desired, around the outer surface of the spray line 22 around a UJärmeisolierung be provided.

There is a device for regulating the flow of the cold medium. A temperature sensor 24, for example a temperature-sensitive element arranged in the gas space of the storage chamber 11, belongs to this device. The temperature sensor 24 is connected via a signal recording device 25 to a temperature controller 26, which in turn is connected to a control valve 28 in the fluid outlet line 21 via a signal transmission device 27. The device specifying the flow rate can be operated electrically or pneumatically.

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In normal operation, liquid coolant is constantly flowing from the storage tank 13 via the outlet line 14 and the control valve 15 to the bottom evaporator 16. This liquid is at least partially evaporated there by the ambient heat, i.e. by the heat of the surrounding gas inside the material chamber U / poor of the good itself, which is transferred via the solid heat conduction path adjoining the good, and by the heat that penetrates through the floor from the surroundings of the chamber 11. Under normal conditions, the evaporated liquid in the bottom evaporator 16 is at least partially superheated so that the gas released through the outlet 20 has an intermediate temperature between the temperature of the liquid refrigerant and the temperature of the material chamber, e.g. B 'with nitrogen, a temperature of about -23.3 ° C to -9.4 ⁰ Co The remaining cold content KaItgasss this is transmitted to the right, if the gas is circulated within the chamber to the material around and in contact therewith. The discharge vapor pressure in the liquid container 13 should be high enough to provide the necessary gas circulation in the chamber 11, Cold medium, normally in liquid form, is from the storage container 13 for the liquid coolant via the lines 21 and 22 depending on intermittently delivered signals from the temperature sensor 24 and provides in part for the cooling, which is necessary to keep the detected temperature within the predetermined range, e.g., "B ₀ between 0.5 and 10 ⁰ C, ⁰ ° C.

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Figure 2 shows a preferred embodiment in which the outlet 20 of the bottom evaporator is connected to a gas expansion device 30, which is arranged in the upper part of the chamber 11 below the spray line 22 and preferably near one end thereof with an inlet overpressure of approximately 0.7 to 1.8 kg / cm, rotating at a speed of 200 to 1500 rpm or more. "A turbine expansion device can also be used instead. The expansion device 30 is via a Coupling element 31 is connected to a fan 3.2, so that the energy released by the expansion of the pressurized gas from a higher to a lower atmospheric overpressure is used as drive energy for driving the fan. The fan improves the gas circulation within the chamber 11 and reduces temperature differences between the Kam merenden _o If desired, the evaporated refrigerant gas, prior to passing through the expansion device 30 to be further heated by being passed through a arranged outside of the chamber 11 · superheater "

In the case of the bottom evaporator 16 of the embodiment according to FIG. 2 separate passages 16c are provided to allow the circulating ambient gas within the chamber to be in heat exchange with the .evaporating liquid refrigerant and the good 12 from one to the other end of the chamber. The warmed up chamber gas,

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which emerges from the opposite end of the passage 16c, flows upwards behind an intermediate wall 33 and becomes at least partially circulated again by means of the fan 32. The fan also ensures that the expanded gas, which leaves the expansion device 30 via an outlet port 34. If desired, a part the circulated gas via the vent 20a to the Atmosphere.

The ventilator 32 can also be operated by means of a suitable power source, for example a battery or a generator (not illustrated) are electrically driven. With such electrically driven fans you can leave that Gas discharged from the bottom steamer generally in the area of the fan so that it is effectively circulated »The advantage of the gas-driven fan according to the embodiment According to FIG. 2, no externally supplied power is required. The one used to drive the fan 32 required power is taken from the existing pressurized coolant itself.

* i f.

In the embodiment of Figure 2 is also a second temperature-dependent control system for the liquid refrigerant in the outlet line 14 going out from the container 13 available. A temperature sensor 24a, for example a thermostat, is located in the lower part of the chamber 11 in thermal contact with a passage 16c for the circulating surrounding gas. This

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The sensor can be arranged in the gas space of the passage or rest on the Uland of the passage »The sensor 24a is connected via a signal recording device 25a to a temperature controller 26a, which in turn is connected to the control valve 15 in the liquid outlet line 14 via a signal transmission device 27a The flow controller can be operated electrically or pneumatically. The temperature response range of the sensor 24a depends on the product in question; it is in any case between about 0.5 ⁰ C and 10.0 ⁰ C. In lettuce setting is preferably from 1.1 to 1.7 ⁰ C below the temperature setpoint of the temperature sensor 24 'in well with optimum cooling values of 4, 4 ⁰ C to 7.2 ⁰ C the setting would be considerably higher »

FIG. 3 shows one for the embodiment of FIG. for a railroad car, suitable preferred construction of the bottom evaporator 16, which has several Wletallkanäle 35, which are arranged in the lower part of the storage chamber 11 and extend from one end to the other. The construction according to FIG and articulated lorries are intended. A first group of channels 35 are open at opposite ends; these channels form the passages 16c for the circulation of the surrounding gas located in the chamber. However, the channel construction can also be used for heat exchangers 16, slide according to the embodiment of Figure 1 no GaedurchlMeee 16c have "Dia Verdampferleitun-

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gene 16a for the liquid coolant are housed in a second group of channels 35; the thermal insulation 17 essentially completely fills the space between the outer wall of the duct and the duct wall _o Similarly, the superheater ducts 16b are accommodated in a further second group of ducts 35 and a second thermal insulation 17b fills the space between the duct outer wall and the duct wall essentially completely from _o

As already stated above, the thermal insulation 17 and 17b are of sufficient quality to keep the heat conduction to the evaporating liquid coolant at 4.1 to 24.8 kcal / hm line length. The thermal conductivity value required for a specific system depends on various variables away. One of these is the number of lines which extend from one end of the chamber 11 to the other and form the heat exchanger 16. In general, a larger number of lines allows a lower thermal conductivity, because in such a case a larger number of heat transfer paths are available. If, on the other hand, only two lines are provided, e.g. B ₀ the liquid evaporator line 16a and the superheater line 16b, the entire floor cooling required for the material must be taken over by these two lines and a relatively high level of heat conduction must be ensured.

Another variable that affects the thermal conductivity, the is required for the elm aolations 17 and 17b, is the

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UJärmsleitung des Hletallboden 18. If the floor 18 delivers a A larger number of elm transmission lines means that their mutual distance is smaller and the heat conduction is lower. . lie, that is, for example, thinner components or Components are used that are made of a material with lower thermal conductivity. Also the goodness of the for that Thermal insulation used on the walls and bottom of the chamber 11 affects the required thermal conductivity of the thermal insulation 17 and 17b. A low-quality chamber insulation requires that the Badjan heat exchanger 16 provides an overall greater cooling capacity, as a result of which a larger number of refrigerant passages or a metal base with higher thermal conductivity may be required.

The thermal conductivity to be provided for the thermal insulation 17 and 17b is further influenced by the gas passages 16c for the surrounding gas Embodiment is shown according to Figure 3, iat a comparatively higher UIMrmeleitwert appropriate. This is upon it due to the fact that the circulating gas takes over its part of the cooling effect by gas heat conduction and transfers it to the property. As a result, the cooling of the goods due to the conduction of solids is reduced and a higher total temperature can be discharged thermal insulation can be tolerated.

UL conductivity values below approximately 4.1 kcal / h m of conduit

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length would be one for the evaporation of the liquid coolant prevent sufficient heat transfer in the pipe, On the other hand, thermal conductivity values above approximately 24.8 kcal / h m line length weaken such a strong heat transfer allow frost damage to occur in the lowest layer of the stored goods, = that is, when used a cryogenic coolant, for example liquid nitrogen, in a line 16a, which is from a thermal insulation - is surrounded, whose UJConductivity is about approximately 24.8 keal / h m, the outer part of the bottom item would be cooled to almost 0 C or less

If there are 16 gas passages in the heat exchanger through which the surrounding gas circulates from one end to the other, For the reasons mentioned above, the thermal conductivity of the thermal insulation 17 and 17b is preferably 8.3 to 20.6 kcal / h m Line length ο If there are no such gas passages, as is the case, for example, in the embodiment according to the figure is the case, a thermal conductivity of 4.1 to 8.3 kcal / h m line length used «

The thickness of a particular thermal insulation that is required to achieve a desired thermal conductivity depends on on the thermal conductivity of the material. A thin one A layer of relatively effective thermal insulation can have the same UJärmelaitwert as a thicker layer of insulation lead to a less effective material »

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In a proven successful embodiment of the invention, the Verdampferlaitung 16a was made of copper tube with a 7 _r 9 mm Auöendurchmesser and 0.76 mm wall thickness which is arranged in 51 mm deep aluminum channels and won a plastic insulation in place and stable foamed * closed cells forming polyurethane surrounded mar, where the UJärmelaitwert of the insulation was about 12.4 kcal / hm line length ₀ There were no frost spots on the underside of the goods _o In another embodiment, cylindrical sections of nitrile rubber foam insulation with a diameter of 38 mm with longitudinal slots around copper pipes of the same size were used This insulation provided a thermal conductivity value of approximately 18.2 kcal / hm line length; it was satisfactory, although frost spots occasionally occurred on the lowest crop layer or the cargo loading area, from this it can be seen that elm insulation with a thermal conductivity of more than approximately 24.8 kcal / hm would allow excessive cooling, which results in frost damage to the lowest crop layers would have c

It should be emphasized that the appropriate Ulärleitwertbereich from 4.1 to 24.8 kcal / hm line is based on temperature differences that exist between the evaporating liquid refrigerant. B ₀ the circumferential UmgeüurMj ^ yris in the embodiment according to Figure 2, the material itself or the heat penetrating through the chamber floor =

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During normal operation, the evaporating liquid is in the Heat exchanger 16 is also overheated and the temperature difference to / Ischen the refrigerant and the material increases in the refrigerant superheating section compared to the evaporator section aba (for example, the temperature difference is between evaporating liquid nitrogen refrigerant and the good at about 195 ° C, while the temperature difference between the overheated gaseous nitrogen coolant and the good can go down to 8.3 C.) If therefore for the superheater section uses the same thermal insulation the thermal conductivity decreases and the heat transfer would occur unevenly from one end to the other within the material chamber. To avoid this, thermally conductive metal parts can be used be arranged distributed in the longitudinal direction at least in the superheater section of the heat exchanger, these metal parts can be in thermal contact with the coolant line 16b and the heat-conducting metal base 18, as shown in FIG the thermally conductive metal parts of the line 16b comprising IKletallaschen 36 are formed with webs 37, which are in different Longitudinal distances against the heat exchanger walls place. Other means, such as metal disks, can be used in order for certain thermal contacts between the coolant line and to take care of the metal floor »

It will be understood that the required thermal conductivity range from approximately 4.1 to 24.8 kcal / h m line length in the Werdampferabschnitt for the liquid coolant the thermal conductivity

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includes, which is arranged distributed in the longitudinal direction thermally conductive metal parts, if such Parts are provided, in this case the represents Thermal conductivity is the sum of the contributions made by the thermal insulation and the conductive metal parts.

In the embodiment according to FIG. 3, the metal tabs 36-37 are not only used for the above-described specification of heat conduction; rather, they also support the line 16b within the channels and ensure that they are in the correct position. According to a modified embodiment, separate components can also be provided for these two functions. In this case, the supports of the line can be made of a non-conductive material, for example a high-strength plastic, while the heat conductors can be metal disks that enclose the line 16b and have a sufficient diameter to be attached to the walls of the channels 35 to lie on _o The thermally conductive metal base is formed by a flat metal plate 18 which connects the lower ends of the channels 35 and extends over the full length and width of the material storage chamber 11. In this embodiment, the plate 18 is connected to the channels in one piece; it forms a highly effective heat transfer path in the transverse direction of the material chamber 11 that is, heat introduced into the passages 16c by the surrounding gas is transferred by means of the plate 18 and the tabs 36 to the coolant in the lines 16a and 16b. This lateral heat transfer takes place

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in addition to the thermal conduction via the thermal insulation 17 instead of; the latter is essential to the invention

The amount of heat that is transferred in the lateral direction by means of the metal plate 18, of course, depends on the thickness of the plate and their UJärmeleitfähigkeit from _o In a tested with success embodiment, the plate construction channel uses the one-piece of Figure 3, the lower bottom plate of 4.8 mm thick aluminum, "Relatively thick metal floor parts allow the use of thermal insulation with relatively higher thermal conductivity values"

An article carrier part 38 is preferably over the top of the heat-insulated coolant line sections of the heat exchanger 16 arranged to prevent dirt and Waste accumulates in the heat insulation 17 and around the heat exchanger to protect against mechanical damage «The part 38 can be made of any suitable material consist, for example, of light metal sheet or plywood «

Figure 4 shows a further embodiment for the heat exchanger 16 and metal base 18 existing assembly, which is particularly suitable for railroad cars that have a pallet-like Have wooden support structure for the property. The latter consists of longitudinal beams 40 and overlying cross planks 41, which are arranged so that longitudinal spaces

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formed werdem A single Verdampfungsdurchlaß 16a for liquid refrigerant and two superheater passages 16b for the refrigerant vapor are present, each of the passages won a UJärmeisolation 17a or 17b surrounded _o In this embodiment, the same kind is used by Iliärmeisolationsmaterial for both passages, but werdsn different insulation thicknesses used to obtain approximately the same UJärmeleitwert over the full length of the heat exchanger 16.So for the larger Δ T, a relatively thicker insulation layer 17a is provided around the evaporator passage 16a, while in view of the lower ΔΤ between the refrigerant vapor and the material, a comparatively thinner one Insulation layer 17b surrounds the superheater passages 16b. If desired, a larger number of refrigerant passages can be used so that the nominal conductivity of the insulation 17a and 17b is lower.

The assemblies consisting of the refrigerant line and thermal insulation the embodiment of Figure 4 are each through inverted IKluldenteile 42 covered, the lower flange portions 44 and 44b rest on the material chamber floor and run transversely to this. As illustrated, the width is of the lower flange portions 44 and 44b is less than the width of the chamber floor, but for one in the transverse direction running Ulärmeleitwag from the passages I6c for the Ambient gas in the chamber is added to the refrigerant in lines 16a and 16b.

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The device according to Figure 4 makes it possible to provide a modified embodiment of the method according to the invention, in which the circulating ambient gas is circulated after Konvektionsuiärmeaustausch with the warmer material by means of the fan 32 in UJärmeaustausch relationship with the metal base parts 44 and 44b, wherein it is circulated through the gas passages 16c flowing "the heat / recorded in this U else by the ITIetallbodenteilen 44 and 44b is then transmitted through solid heat conduction to the IMrmeisolation 17a and 17b, the Kälteträgerverdampfungs- and superheater lines 16a bziu _o 16b surrounds (Figure 4) ₀ then .If the heat by _o solid heat conduction from the U / ärmeisolation the Laitungen 16a and 16b and from there by convection to the therein refrigerant transferred These! heat transfers are sufficient to maintain the lowermost layer of material 12a from end to end of the chamber 11 at a temperature of the means of the temperature sensor 24 determined not deviate lten chamber gas temperature 2.8 ^0C.

A number of tests were carried out to establish the qualitative Advantages of the invention over a similar nitrogen spray cooling system without a bottom evaporator or an overhead arranged fan. ”In this known system, hereinafter referred to as system A, lettuce in a remote truck from Salinas, California Chicago, Illinois. The tug was 12.2 m long, 2.4 m wide and was means of saturated liquid

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Nitrogen cooled, which emerged from the storage container at a vapor pressure of approximately 1.4 kg / cm through the spray line arranged overhead. The set value of the temperature control was 1.7 ⁰ C _{0 for system A and the following systems}

In the system B, the same kind of tug was used uiie the system A, but a channel bottom evaporator according ^F igur 3 was provided together with a fan, the mar arranged in the upper part of the chamber below the spray head, uiie this is illustrated in Figure 2. " Both centrifugal and axial fans were tested. In any case, the fan was coupled to an air motor which is driven by expanding nitrogen vapor (also see F £ gur 2) _o The bottom reboiler consisted of copper and aluminum tubes of 6.4 and 7.9 mm outer diameter. The pipes were supported by means of spaced brackets made of rustproof steel wire 3.2 mm in diameter within 51 mm deep aluminum floor channels which were about 51 mm apart and which were connected on the underside in one piece to a floor part about 4.8 mm thick were «, the retaining clips initially had a longitudinal distance of about 0.61 m in the coldest part of the evaporator section; the distance gradually decreased down to about 76 mm at the outlet end of the heat exchanger 16.

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foamed polyurethane filled with closed cells. There were used two complete strands of insulated refrigerant pipe, both of which ran in the longitudinal direction of the trailer floor ,, The Ulärmeleitwert was approximately in each case with the passages for liquid nitrogen and vaporized nitrogen 12.4 kcal / hm pipe length _o nitrogen in an amount of about 3.6 kg / h passed through the bottom evaporator in the 12.2 m long and 2.4 m wide trailer Drive of the fan mentioned above is required.

The air motor used in System B was a glide

2 gel motor suitable for an inlet pressure of 0.7 to 7 kg / cm and a rated speed of 1600 rpm with an inlet pressure of 1.4 kg / cm and an outlet pressure corresponding to atmospheric pressure. The centrifugal fan was designed so that he / min caused ₀ The motor working for an air flow of 18.7 m / min against a static pressure of 7.6 mm of water column at 1000 rpm with approximately 225 U / min and was spur gears with the Coupled with a fan that rotated at approximately 500 rpm and provided a gas flow of 8.5 m / min against a head pressure of 1.3 mm of water column. The axial flow propeller fan (which was provided in place of the centrifugal fan) had a diameter of 254 mm, had four wings and could

0 0 9 8 2 3/1372

»7

an air flow of 17m / min against a static pressure of 1.3 mm water column at 1500 rpm deliver «motor and fan were directly coupled to each other and both were running at approximately 1500 rpm. When trying the system B the trailer remained stationary. Lettuce in boxes was used as storage material

The operating behavior of the two systems is shown summarized in the graph in FIG. 5, with the temperature difference (ΔΤ) between dar on the thermostat set temperature in the gas space above the top layer of material and the temperature of the material at a height of approximately 152 mm above the cargo area for various lengthways positions inside the storage chamber is shown «, the temperatures were obtained with the help of thermocouples, which in the goods were placed in the front, middle and rear parts of the chamber. During each experiment, the temperatures were constantly recorded «Although the data is not quantitative Allow comparison because the test conditions and test facilities were not identical, systems A and B can be compared qualitatively with one another. The data of the Systems B are shown as a sin band because the value of AT was also influenced by the rate of circulation of the surrounding gas in the bottom evaporator. In general, the value of ΔΤ lowered when the UmwMlzgeschuiindigkait of approximately B, 5 m / h was increased to 17 m / h »It's too srkermenj that With the help of system B, a decisive connection to form

0098 2 3/1372

a reduced variation in the ratio of ΔΤ between the top and bottom of the chamber and between the ends of the chamber was achieved. For example, in the system B were measured from end to end of the chamber material temperatures all maintained at a Uiert which was only 1.1 to 2.8 ⁰ C above the setting temperature of the temperature sensor "It is also apparent that the value of at ΔΤ system B was much smaller than system A. Mährend the lowest Gutlage was maintained at a temperature, for example, in the system B, which was from 1.1 to 2.8 ⁰ C above the set temperature, as is required in the method of the invention in the system A, the temperature was of the greater part of the lowermost Gutlage to rise to a value which was more than 4.4 ⁰ C above the setting value, while a part of this good even reached a temperature which was 8.3 C above the set temperature, "

fc It is understood that numerous modifications within the scope of the invention possible are. For example, the cooling system described can also be used in stationary systems,

009823/1372

Claims (1)

- 31 claims ζ 1 ο! Device for spray cooling of frost-sensitive goods ^ - ^ with a container for holding a low-boiling liquid refrigerant, a fluid outlet line connected to the container and an overhead line, the openings for spraying the refrigerant into a at a temperature between approximately 0 , 5 ⁰ C and 10.0 C to be held material storage chamber, characterized by a liquid outlet line connected to the container, a liquid evaporator line connected to the liquid outlet line, which is arranged in the lower part of the material storage chamber and extends essentially over its full length, a liquid vapor line Surrounding thermal insulation of sufficient quality to keep the thermal conductivity at 4.1 to 24.8 kcal / hm line length, and thermally conductive metallic floor parts adjacent to the elm insulation, which are in thermal transition zone and which are below the goods for at least a T Part of the length and at least part of the width of the storage chamber are sufficient. V ₃ . Device for spray cooling of frost-sensitive material housed in a storage chamber with a container for receiving a low-boiling liquid coolant, a fluid outlet line connected to the container and 009823/1372 . - 32 - one arranged above the head spray line which in longitudinal direction arranged distributed openings for spraying the cooling agent in comprising at a temperature between about 0.5 ⁰ C and 10.0 ⁰ C-held Gutspeicherkammer, characterized by means connected to the container liquid outlet, one at The liquid evaporation line connected to the liquid outlet line, which is arranged in the lower part of the material storage chamber and extends essentially over its full length, also a heat insulation surrounding the liquid evaporation line of sufficient quality to keep the noise level at 8.3 to 20.6 kcal / hm line length, as well Gas passages arranged in the lower part of the material storage chamber, which extend essentially over the full length of the material storage chamber in U / heat exchange relationship with the thermal insulation and the opposite ends of which are in open connection with the gas space of the material chamber, and to the thermal insulation and the gas diameter Passes adjoining, with these in elm transition relationship, thermally conductive metallic base parts, which extend below the goods over at least part of the length and at least part of the width of the goods storage chamber. 3. Device for spray cooling of frost-sensitive transport goods, characterized by a receiving the goods Storage chamber; a thermally insulated container associated with the storage chamber for a cold, under pressure 009 8 2 3/1372 standing, low-boiling liquefied gas with a boiling point at atmospheric pressure of below approximately -29 ⁰ C; a fluid outlet conduit connected at one end to the container; a spray line connected at one end to the other end of the fluid outlet line, which is housed in the upper part of the storage chamber, extends essentially over its full length and has openings distributed in the longitudinal direction for the exit of separate coolant flows serving to cool the material the storage chamber is provided; a device regulating the flow of the refrigerant with a first temperature sensor housed in the storage chamber and a control valve located in the fluid outlet line which is connected to the first temperature sensor in such a way that it responds to the storage chamber temperature determined by the first temperature sensor and the chamber is at a temperature between holds approximately 0.5 ^° C and 10.0 ^° C; a liquid outlet conduit connected at one end to the container; a liquid vaporizer line accommodated in the lower part of the storage chamber and extending essentially over its entire length, the inlet end of which is connected to the other end of the liquid outlet line; A noise insulation surrounding the liquid evaporator line of sufficient quality to ensure a noise conductivity of 4.1 to 41.3 kcal / hm line length; and thermally conductive 009823/137 2 Oil metal floor parts, dis adjacent to the heat insulation run, are in noisy transitional relationship to this and below the goods over at least part of the length and at least part of the width of the storage chamber are sufficient. Device according to claim 3, characterized in that
that in the lower part of the material storage chamber there are essentially gas passages extending over its full length, which are in heat exchange with the Ufärmeisolation and the HfIetallbodenenteile and their opposite ends are in open connection with the gas space of the material storage chamber, and that the noise insulation is of sufficient quality, to provide for one heat conduction \ / on 8.3 to 20.6 kcal / hm line length. 5. Apparatus according to claim 4, characterized in that
that in the lower part of the storage chamber from the end to
End of the same reaching Ifletallkanäle are provided that a first group of these channels the gas passages
forms that the liquid evaporation line is accommodated in a second group of these channels, that the noise insulation the space between the outer wall of the liquid evaporation line and the walls of the second
Group of channels and that a flat metal plate that connects the lower ends of the channels and 00 9 823/1372 across the full length and width of the storage chamber extends, the thermally conductive (Yletallbodenenteile forms. Device according to claim 3, characterized in that the heat-conducting metal base parts are formed from a flat one Plate are formed. 7. Apparatus according to claim 3, characterized in that the thermally conductive ffletallbodenenteile of several higher-lying plates are formed which have lower flange portions resting against the chamber floor. Β. Device according to claim 4, characterized in that in the upper part of the storage chamber at one end thereof and a fan is arranged below the spray line. 9 "Device according to claim 8, characterized in that the fan is connected to an electric drive. IQ. Device according to claim 3, characterized by a Cold gas superheater line, the inlet end of which is connected to the outlet end of the liquid evaporator line and which is arranged in the lower part of the material storage chamber parallel to the liquid evaporation line, 00 9 823/1372 - 36 - a heat insulation surrounding the superheater line of sufficient quality * to be thermally conductive for a UJ from 4.1 to 24.8 kcal / h m line length to ensure, and second heat-conductive ffletallbodenteile, which are adjacent run to the second Uiärmeisolation, in U / arm transition relationship to this stand and below the goods over at least part of the length and at least part of the width of the storage chamber. 11. The device according to claim 10, characterized by one connected to the outlet end of the cold gas superheater line Gas expansion device in which the vaporized liquid expands and which is only due to this expansion Turning energy ^. delivers, as well as by one with the Gas expansion device in drive connection fan, the chamber in the upper part of the storage one end of which is arranged below the spray line. 12o device according to claim 3, characterized in that the Uiärmeisolation and the Ifletallbodenenteile several heat-conducting metal parts distributed in the longitudinal direction assigned. 13o device according to claim 4, characterized by a device regulating the outlet of the liquid refrigerant with a device in the lower part of the chamber in UIMrme- 00 98 23/1372 contact with the gas passages arranged second tem-. temperature sensor and a control valve located in the liquid outlet line, which is connected to the temperature sensor in such a way that it responds to the gas passage temperature determined by the second temperature sensor and maintains this temperature between approximately 0.5 ^° C. and 10.0 ^° C. ο 14. A method for spray cooling of frost-sensitive transport goods housed in a storage chamber by passing a low-boiling liquid refrigerant taken from a container through openings of a spray line installed above the goods, which are distributed in the longitudinal direction, depending on the determination of the between approximately 0.5 ^° C and 10, O ^{Chamber gas temperature to be maintained 0} C, characterized in that heat is transferred by solid heat conduction from the lowest material layer to lYletallbodenenteile, which extend below the lowest material layer at least over part of the chamber length and at least over part of the chamber width, that the heat by solid heat conduction from the Ifletallbodenenteile is further transferred to a thermal insulation, which extends in the longitudinal direction of the chamber below the lowermost layer of material and surrounds a Ver evaporator line for liquid refrigerant that the warning by solid heat conduction from the heat olation is transferred to the evaporator line and that 009823/1372 the heat is finally transferred by convection from the evaporator line to the liquid coolant evaporating therein, the heat transfers being sufficiently dimensioned to keep the bottom layer of material from end to end of the chamber at a temperature that does not exceed the determined chamber gas temperature, 8 ⁰ C abuieicht. 15. The method according to claim 14, characterized in that cold gas inside the good chamber in convection / heat exchange with the property constantly around it and then in an end-to-end exchange of convections with the metal base parts below the The lowest layer of material is malted. 16o method for spray cooling of frost-sensitive transport goods housed in a storage chamber by passing a low-boiling liquid coolant taken from a container through openings distributed in the longitudinal direction of a spray line installed above the goods, depending on the determination of the between approximately 0.5 ^° C and TO ₁ O ⁰ C to be kept chamber gas temperature above the good, characterized in that cold gas is constantly circulated in Kanvektionsiuärmeaustausch with the warmer good that the eruiärmte gas is circulated in heat exchange with Hfletallbodenenteile, which is below the lowest Gutachicht at least over part of the 009823/1372 Combar length and at least over part of the chamber width enough that the noise is then caused by solid heat conduction from the metal base parts to a thermal insulation, which extends in the longitudinal direction of the chamber below the lowermost layer of material extends and an evaporation line for liquid coolant surrounds that the Heat through solid heat conduction ν, οη the UJärmeisolation is transferred to the evaporator line and that the Heat eventually by convection from the evaporator line on the liquid coolant evaporating in it are transferred, and the heat transfers are sufficient are dimensioned to keep the lowest material layer at a temperature from end to end of the chamber, which does not deviate from the determined chamber gas temperature by more than 2.8 C. 009823/1372 Blank page