Reefer container and method for preserving fruits and vegetables using said reefer container

Abstract

[Problem] To provide a reefer container that, in addition to having a high cooling efficiency, has a low running cost and is easy to maintain. [Solution] A reefer container 1 has: a container body 2 for storing and preserving fruits and vegetables or the like; a cooling device 3 for cooling the inside of the container body 2; a water recovery means 4 for recovering water that has condensed inside the container body 2; and a curing unit 5 for subjecting the storage contents that are stored inside the container body 2 to a curing process. The cooling device 3 is configured so as to cool the inside of the container body 2 by causing air which has been taken in inside the container body 2 to pass upward from below, through the interior of a heat exchange member 10 which has accumulated cooled moisture, to result in low-temperature high-humidity air, and causing said low-temperature high-humidity air to flow downward from above.

Description

Reefer container and method for preserving fruits and vegetables using the reefer container

[0001] The present invention relates to a reefer container (cooling container) for storing and refrigerating vegetables, flowers, etc., and a method for preserving vegetables (particularly root vegetables such as sweet potatoes and radishes, leafy stem vegetables such as onions and cabbage, and fruit vegetables such as pumpkins and cucumbers) using the reefer container.

[0002] Refrigerators that cool and circulate the air inside using a heat exchanger in a cooling device have been widely used as devices for storing fruits and vegetables in a chilled state. However, when using such refrigerators, if the temperature of the air inside the refrigerator drops, the amount of saturated water vapor in the air decreases, which can cause the moisture in the fruits and vegetables to evaporate, resulting in a loss of the fruit and vegetables' weight or even a loss of freshness. For this reason, as disclosed in Patent Document 1, a cooling container has been developed that, when air is drawn into the cooling chamber of the cooling device from below and moved upward, moves around a heat exchanger that stores cooled water, thereby converting the air into low-temperature, high-humidity air (air containing water vapor), and then circulates the low-temperature, high-humidity air.

[0003] Utility Model Registration No. 3199521

[0004] However, conventional cooling containers such as those described in Patent Document 1 suffer from the drawback that low-temperature, high-humidity air condenses as it circulates through the storage space containing the fruits and vegetables, causing it to fall to the bottom of the storage space, necessitating the need to supply water to the heat exchanger from outside, resulting in high running costs. Furthermore, because the condensed water that accumulates at the bottom of the storage space after the fruits and vegetables are cooled is not removed periodically, there is a risk of bacterial growth. Furthermore, as the operating time increases, calcium ions, magnesium ions, and the like contained in the water used precipitate and adhere to the heat exchanger, reducing heat exchange efficiency and making it impossible to obtain the desired temperature.

[0005] The object of the present invention is to provide a reefer container (refrigerated container) that solves the above-mentioned problems of refrigerated containers, has high cooling efficiency, low running costs, and is easy to maintain, and also to provide a method for preserving fruits and vegetables (particularly root vegetables, leafy vegetables, and fruit vegetables) that utilizes such a reefer container and can maintain their freshness at a high level.

[0006] A first aspect of the present invention is a movable reefer container comprising a hollow container body covered with a thermal insulator and a cooling device for cooling the inside of the container body, wherein the cooling device cools the inside of the container body by passing air drawn up inside the container body from bottom to top through a porous structure that stores cooled moisture, thereby making the air low-temperature and humid, and then allowing the low-temperature and humid air to flow downward from top to bottom, and wherein the cooling device is provided with water recovery means that collects moisture condensed inside the container body, filters the moisture, and then uses the collected moisture as moisture to be stored in the porous structure.

[0007] The invention described in claim 2 is characterized in that in the invention described in claim 1, a curing unit is provided for heating the water stored in the porous structure.

[0008] The invention described in claim 3 is characterized in that, in the invention described in claim 1, the water recovery means is provided with a filter consisting of a structure in which a large number of curved fibers made of synthetic resin are bonded together in a scattered pattern.

[0009] The invention described in claim 4 is a method for preserving sweet potatoes, characterized in that the inside of the container body containing sweet potatoes is cured for 48 hours or more using the reefer container described in claim 2 or 3 in an atmosphere of 30 to 40°C and 85 to 99% RH, and then cooled and maintained in an atmosphere of 12 to 16°C and 85 to 99% RH. Note that a curing time of 96 hours or less is preferable because it can reduce the cost required for preservation, and similarly, a cooled and maintained time of 168 hours or more is preferable because it causes saccharification of the starch contained in the sweet potatoes, improving their sweetness and flavor.

[0010] The invention described in claim 5 is characterized in that, in the invention described in claim 4, the sweet potatoes are washed within 96 hours after harvest before being placed in the container. The soil attached to the sweet potatoes at the time of harvest may contain bacteria, and during harvesting, these bacteria may invade through wounds on the sweet potatoes before the cork layer is formed by curing, resulting in a decrease in the quality of the sweet potatoes. To prevent this situation, it is preferable that the sweet potatoes be washed within 96 hours after harvest before being placed in the container. Furthermore, since a large amount of soil or other foreign matter attached to the sweet potatoes reduces the filtration efficiency during water recovery, it is preferable to remove the soil by washing in advance.

[0011] The reefer container described in claim 1 cools the inside of the container body as low-temperature steam, and then recovers the condensed water to reuse it as cooling water, so it has high cooling efficiency and can keep running costs low.In addition, since condensed water does not accumulate at the bottom of the part that stores fruits and vegetables, maintenance is easy.

[0012] The reefer container according to claim 2 is provided with a curing unit for heating water stored in the porous structure that functions as a heat exchanger, and therefore can be suitably used for preserving fruits and vegetables (root vegetables, leafy vegetables, fruit vegetables, etc.) whose freshness can be maintained at a high level by curing treatment.

[0013] In the reefer container described in claim 3, the water recovery means is provided with a filter made of a structure in which a large number of bent fibers made of polyvinylidene chloride are bonded together in a scattered pattern, and since mud and foreign matter can be effectively filtered out when recovering water condensed inside the container body, the reefer container can perform its cooling function for a long period of time without being damaged.

[0014] According to the method for preserving sweet potatoes using a reefer container as set forth in claim 4, it is possible to maintain the freshness of sweet potatoes at a high level and improve their sweetness and flavor at a low cost.

[0015] According to the method for preserving sweet potatoes using a reefer container as set forth in claim 5, the curing effect of the sweet potatoes can be further improved, the freshness of the sweet potatoes can be maintained at a high level, and the efficiency of water recovery can be improved.

[0016] Fig. 1 is an explanatory diagram (conceptual diagram) showing the inside of a reefer container. Fig. 2 is an explanatory diagram (conceptual diagram) showing the installation portion of a cooling device. Fig. 3 is an explanatory diagram showing a heat exchange member (a is a front view, b is a plan view, c is a cross-sectional view taken along line A-A in b, d is a cross-sectional view taken along line B-B in b, and e is an enlarged view of part α in c). Fig. 4 is an explanatory diagram (conceptual diagram) showing the operation of a reefer container.

[0017] Hereinafter, an embodiment of a reefer container and a method for preserving fruits and vegetables (sweet potatoes) using the reefer container according to the present invention will be described in detail with reference to the drawings.

[0018] 1 is a conceptual diagram showing the inside of a reefer container, and the reefer container 1 comprises a container body 2 for storing and preserving fruits and vegetables, a cooling device 3 for cooling the inside of the container body 2, water recovery means 4 for recovering water that has condensed inside the container body 2, and a curing unit 5 for curing the contents stored inside the container body 2. The cooling device 3 and the curing unit 5 are connected to a control device (not shown), and their operations can be controlled by the control device.

[0019] The container body 2 is a hollow, rectangular parallelepiped made of metal, and its interior surface is covered with a heat insulating material. A storage section (storage space) 6 capable of storing fruits and vegetables F, F... is formed inside the container body 2, and a storage shelf 7 is installed on which the fruits and vegetables F, F... are placed. The shelves (bottom plates) of the storage shelf 7 are mesh-like. A door member (not shown) that can swing open like a double door is provided at one longitudinal end (the left end in FIG. 1 ) of the container body 2 for loading and unloading the fruits and vegetables F, F.... A cooling device 3 is installed at the other longitudinal end (the right end in FIG. 1 ) of the container body 2 (a part of the container body 2 is partitioned off as the cooling device 3).

[0020] In addition, a temperature / humidity sensor 23 is provided in the storage section 6 of the container body 2, and this temperature / humidity sensor 23 detects the temperature and humidity inside the storage section 6 and feeds back this data to a control device (not shown), thereby enabling the temperature and humidity inside the storage section 6 to be precisely controlled to predetermined values.

[0021] 2 shows the installation portion of the cooling device 3, which is composed of a water storage tank 8 capable of storing cooling water, a chiller unit 9 for cooling the water stored in the water storage tank 8, a heat exchange member 10 which is a porous structure that functions as a heat exchanger, a discharge pipe 11 for causing the water stored in the water storage tank 8 to fall evenly and uniformly into the heat exchange member 10, a circulation pump 12 for drawing the water stored in the water storage tank 8 up to the drain pipe 11, a first water lift pipe 13 connecting the water storage tank 8 and the discharge pipe 11, and a circulation fan 14 for drawing air in the storage section 6 into the cooling device 3. The cooling device 3 is separated from the storage section 6 by a case 15, and a discharge window 16 and an intake window 17 are formed in the upper and lower parts of the case 15, respectively.

[0022] Meanwhile, the chiller unit 9 includes a heat exchanger, a compressor, and a pressure reducer, and is capable of cooling the water stored in the water storage tank 8 by heat exchange using a refrigerant. In addition, the chiller unit 9 is capable of controlling the cooling temperature of the water stored in the water storage tank 8 by changing the compression ratio of the refrigerant by the compressor and the decompression ratio of the refrigerant by the pressure reducer using a control device (not shown). The discharge pipe 16 also has a large number of spray holes, which enable the water drawn up through the first water lift pipe 13 to fall (spray) evenly and uniformly onto the upper surface of the heat exchange element 10.

[0023] 3 shows a heat exchange element 10, in which a porous structure 10a is housed inside a case 10b. The porous structure 10a is made by stacking a predetermined number of rectangular plate members 10p, 10p... made by pressing a synthetic resin (polypropylene) plate material having a predetermined thickness (approximately 1.5 mm) into a predetermined shape and joining (adhering or fusing) them in a scattered manner at predetermined positions.

[0024] Each plate member 10p, 10p... has a shape (i.e., a corrugated slate shape) in the middle part in the height direction (excluding the parts of a constant width (approximately 100 mm) at the top and bottom edges) in which linear mountain folds of a constant width (mountain folds with a cross section perpendicular to the longitudinal direction that is approximately U-shaped) inclined to a predetermined angle (approximately 45°) with respect to the vertical direction and linear valley folds of approximately the same width (valley folds with a cross section perpendicular to the longitudinal direction that is approximately U-shaped) are continuously arranged in the plane. Also, in the parts of a constant width (approximately 100 mm) at the top and bottom edges, the mountain folds of the constant width and the valley folds of the approximately same width are curved and arranged vertically. The ridge lines (fold lines) L of these mountain folds １ , L １ ...and the ridge line L of the valley fold portion ２ , L ２In addition, numerous grooves V, V... are provided at equal intervals in each mountain fold and each valley fold, perpendicular to the longitudinal direction and having a predetermined depth (a depth sufficiently shallower than the thickness of the plate member 10p, i.e., approximately 0.5 mm).

[0025] In the structure 10a, the predetermined number of plate members 10p, 10p... are aligned along the ridge line L １ , L １ ...and the ridge line L of the valley fold portion ２ , L ２ The plate members 10p are stacked alternately in the opposite directions so that the edges of the plate members 10p are perpendicular to each other. １ , L １ ...and ridge line L ２ , L ２ The plates are stacked so that they are perpendicular to each other) and are assembled together by joining them in a scattered manner at predetermined locations.

[0026] On the other hand, the water recovery means 4 is composed of a tray 18 laid so as to cover the bottom surface of the storage section 6, a water pump 19 for lifting (returning) the condensed water stored in the tray 18 to the water storage tank 8, a second water pumping pipe 20 connecting the tray 18 and the water storage tank 8, and a filter 21 for filtering the condensed water stored in the tray 18 when lifting it up to the water storage tank 8. The filter 21 is made of a large number of bent fibers (average thickness = approximately 0.5 mm) made of synthetic resin (polyvinylidene chloride) bonded together in a scattered pattern, and has a thickness of approximately 50 mm.

[0027] Similarly to the chiller unit 9, the curing unit 5 is equipped with a heat exchanger, heater, compressor, and pressure reducer, and is capable of heating the water stored in the water storage tank 8 by heat exchange using a refrigerant. In addition, the curing unit 5 is capable of controlling the temperature of the water stored in the water storage tank 8 by changing the compression ratio of the refrigerant by the compressor and the decompression ratio of the refrigerant by the pressure reducer using a control device (not shown). The water stored in the water storage tank 8 can also be heated using the heater.

[0028] In addition, a storage information management device 22 equipped with a storage means and an information transmission means is attached to the outside of the container body 2, and is capable of storing information such as the type, place of origin, quantity, storage period, delivery destination, storage history regarding storage period and atmosphere of the fruits and vegetables etc. stored in the container body 2, and transmitting this information based on commands from outside.

[0029] <Operation of Reefer Container> Figure 4 shows the operation of the reefer container 1 configured as described above, and the reefer container 1 can accommodate and store fruits and vegetables F, F..., flowers, etc., in the container body 2, with them placed on the shelves of the storage shelves 7. When the cooling device 3 is driven with fruits and vegetables F, F..., etc. accommodated and stored in the container body 2 in this manner, the air inside is sucked up by the circulation fan 14 at the bottom of the cooling device 3, flows into the inside of the cooling device 3 (cooling chamber) through the suction window 17, and forms an ascending air current that passes through the inside of the heat exchange element 10.

[0030] On the other hand, when the cooling device 3 is driven, the water stored in the water storage tank 8 is cooled by the chiller unit 9, and the cooling water is raised by the circulation pump 12 through the first water lift pipe 13 to the upper drain pipe 11. The cooling water raised to the drain pipe 11 is then sprayed out at a constant pressure from a large number of spray holes drilled in the drain pipe 11, falls onto the upper surface of the heat exchange element 10, and flows down inside the heat exchange element 10 (inside the porous structure 10a).

[0031] Inside the heat exchange member 10, heat is exchanged between the air rising from below and the cooling water flowing down from above, cooling the rising air and generating low-temperature water vapor from the evaporated cooling water. The low-temperature air and water vapor are then ejected from the upper exhaust window 16 toward the top of the storage unit 6 by the airflow of the circulation fan 14. The entire storage unit 6 is efficiently cooled by the low-temperature air and water vapor ejected from the top in this manner.

[0032] The low-temperature air and water vapor sprayed out from the top of the storage section 6 flows downward, cooling the fruits and vegetables F, F... placed on the storage shelves 7 (i.e., exchanging heat with the fruits and vegetables F, F...). The water vapor that has cooled the fruits and vegetables F, F... condenses as its temperature rises and falls to the bottom of the storage shelves 7. The condensed water that falls in this way is collected in a tray 18 installed below the storage shelves 7. When the water vapor that has cooled the fruits and vegetables F, F... condenses, any dirt or other particles adhering to the fruits and vegetables F, F... will mix with the condensed water and fall into the tray 18.

[0033] The water (condensed water) stored in the tray 18 as described above is drawn up by a water pump 19 installed at one end (the right end in FIG. 1 ) of the tray 18 via a second water pumping pipe 20 and discharged (returned) into the water storage tank 8. When the water stored in the tray 18 is drawn up by the water pumping pump 19, the water is filtered by a filter 21 installed below the water pumping pump 19, and mud and foreign matter in the water are removed.

[0034] Meanwhile, in the reefer container 1, the fruits and vegetables F, F... stored in the container body 2 can also be cured to prevent the growth of microorganisms. For example, when curing sweet potatoes, instead of driving the chiller unit 9 of the cooling device 3, the curing unit 5 is operated to heat the water stored in the water storage tank 8. When the water stored in the water storage tank 8 is heated in this manner, the circulation pump 12 draws the heated water up to the upper drain pipe 11. The heated water then sprays out from the spray holes drilled in the drain pipe 11, falls onto the upper surface of the heat exchange element 10, and flows down inside the heat exchange element 10 (inside the porous structure 10a). When the water stored in the water storage tank 8 is heated, the evaporated heated water generates water vapor.

[0035] Then, inside the heat exchange member 10, heat exchange occurs between the air rising from below and the warm water flowing down from above, warming the rising air. The heated air and warm water vapor evaporated from the water storage tank 8 are then blown out from the upper exhaust window 16 to the top of the storage section 6 by the airflow of the circulation fan 14. The entire storage section 6 is heated by the warm air and water vapor blown out from above. Note that if condensation from the ceiling of the storage section drips onto the sweet potatoes during the curing process, causing problems, it is possible to reverse the rotation of the circulation fan and change the flow of warm air inside the storage section from bottom to top.

[0036] <Sweet Potato Preservation Test> A sweet potato freshness preservation experiment was conducted using the reefer container 1 described above. Specifically, 500 g of sweet potatoes were placed on the storage shelf 7 of the container body 2 of the reefer container 1, and the interior of the container body 2 was maintained in an atmosphere of 33°C and 95% RH for 72 hours, and then in an atmosphere of 14°C and 90% RH for 168 hours. The freshness of the sweet potatoes stored in the reefer container 1 in this manner was compared with the freshness of sweet potatoes stored in an atmosphere of 25°C and 65% RH for 240 hours in terms of mold growth, wilting, odor, and sweetness. As a result, it was found that the sweet potatoes stored in the reefer container 1 had better freshness in terms of both wilting and odor.

[0037] <Effects of the Reefer Container> As described above, the reefer container 1 cools the inside of the container body 2 by the cooling device 3 passing the air drawn up inside the container body 2 from bottom to top through the heat exchange member (porous structure) 10 that stores cooled moisture, turning it into low-temperature, humid air, and then allowing this low-temperature, humid air to flow downward from top to bottom. The reefer container 1 is also provided with a water recovery means 4 that collects moisture that condenses inside the container body 2, filters the moisture, and then uses it as moisture to be stored in the heat exchange member (porous structure) 10. Therefore, the reefer container 1 has high cooling efficiency and can keep running costs low. In addition, the reefer container 1 is easy to maintain because condensed water does not accumulate at the bottom of the part that stores fruits and vegetables.

[0038] Furthermore, the reefer container 1 is provided with a curing unit 5 for heating the water stored in the heat exchange member (porous structure) 10, and therefore can be suitably used for preserving fruits and vegetables such as root vegetables, leafy vegetables, and fruit vegetables (especially sweet potatoes, onions, and pumpkins) whose freshness can be maintained at a high level by curing treatment.

[0039] Furthermore, the reefer container 1 is equipped with a filter 21, whose water recovery means 4 is made of a structure in which a large number of bent fibers made of synthetic resin are bonded together in a scattered pattern, and since it can effectively filter out mud and foreign matter when recovering water that has condensed inside the container body 2, it can perform its cooling function for a long period of time without being damaged.

[0040] In addition, since the reefer container 1 has the heat exchange member (porous structure) 10 having the specially shaped porous structure as described above, it has good heat conversion efficiency and can cool fruits and vegetables very efficiently.

[0041] <Modifications to Reefer Container> The reefer container according to the present invention is not limited to the above-described embodiments, and the materials, sizes, shapes, structures, and other configurations of the container body, cooling device, water recovery means, curing unit, heat exchanger, filter, etc. can be appropriately modified as needed without departing from the spirit of the present invention, and a water supply tank, etc. can be installed when more water is consumed than is recovered. Furthermore, when storing fruits and vegetables whose freshness deteriorates due to carbon dioxide damage, it is possible to reduce the carbon dioxide concentration in the storage section by separately providing a device for removing carbon dioxide dissolved in low-temperature, humid air.

[0042] For example, the reefer container according to the present invention is not limited to one in which the chiller unit and the curing unit 5 are provided separately as in the above embodiment, but may be one in which the chiller unit and the curing unit are integrated. Furthermore, the reefer container according to the present invention is not limited to a stationary type as in the above embodiment, but may be one configured to be transportable by a trailer or the like. Furthermore, the porous structure of the cooling device is not limited to one configured by a single porous structure as in the above embodiment, but may be one in which multiple types of porous structures are stacked one on top of the other. Meanwhile, the filter of the water recovery means is not limited to one in which a large number of curved fibers made of synthetic resin are bonded together in a scattered manner, but may be changed to one made of woven fabric or nonwoven fabric, and may be used in combination with other filtering devices such as a sand filtering device.

[0043] Furthermore, the porous structure used as the heat exchange element is not limited to the above embodiment, in which a predetermined number of rectangular plate members folded so that the mountain folds and valley folds are continuous are stacked so that the fold lines intersect alternately at right angles, and then joined in a scattered manner at predetermined positions. It is also possible to change the structure to one in which multiple corrugated sheets (such as those with a sinusoidal cross section or a cross section shaped like a series of trapezoids and inverted trapezoids) are stacked and joined in the same direction (glued or fused), or one in which multiple corrugated sheets are stacked and joined so that the directions of their grooves intersect at a predetermined angle (10 to 80°) in a staggered manner.

[0044] Since the reefer container according to the present invention has the excellent effects as described above, it can be suitably used as a device for storing and preserving fruits and vegetables, flowers, and the like.

[0045] DESCRIPTION OF SYMBOLS 1. Reefer container 2. Container body 3. Cooling device 4. Water recovery means 5. Curing unit 6. Storage section 7. Storage shelf 8. Water storage tank 9. Chiller unit 10. Heat exchange member (porous structure) 10a. Porous structure 10b. Case 10p. Plate member 11. Drain pipe 12. Circulation pump 13. First water lift pipe 14. Circulation fan 15. Case 16. Discharge window 17. Intake window 18. Receptacle 19. Water lift pump 20. Second water lift pipe 21. Filter 22. Stored information management device 23. Temperature and humidity sensor

Claims

1. A movable reefer container comprising a hollow container body covered with a heat insulating material and a cooling device for cooling the inside of the container body, wherein the cooling device cools the inside of the container body by passing air drawn up inside the container body from bottom to top through a porous structure that stores cooled moisture, turning it into low-temperature, humid air, and allowing the low-temperature, humid air to flow downward from top to bottom, and wherein the reefer container is also provided with a water recovery means that collects moisture that has condensed inside the container body, filters the moisture, and then uses it as moisture to be stored in the porous structure.

2. The reefer container according to claim 1, further comprising a curing unit for heating the water stored in the porous structure.

3. A reefer container as described in claim 1, characterized in that the water recovery means is provided with a filter made of a structure in which a large number of bent fibers made of synthetic resin are bonded together in a scattered manner.

4. A method for preserving sweet potatoes, comprising using the reefer container according to claim 2 or 3, curing the inside of the container body containing the sweet potatoes in an atmosphere of 30-40°C and 85-99% RH for 48 hours or more, and then cooling and maintaining the container in an atmosphere of 12-16°C and 85-99% RH.

5. The method for preserving sweet potatoes according to claim 4, wherein the sweet potatoes before storage are washed within 96 hours after harvest.

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