Refrigerator with drying function

Abstract

When drying food in a refrigerator, it is possible to dry it easily, inexpensively, efficiently, and quickly without transferring odors to other foods, while maintaining quality. [Solution] In a drying chamber cooled by a circulating cold air airflow that has been heat-exchanged by a cooler operating at freezing temperatures, a multilayered moisture-permeable membrane that allows only water vapor and moisture to pass through is provided as a partition surface on a portion of the upper ceiling-level shielding wall. Water vapor and moisture from the food to be dried, heated by a heating means at the lower bottom, are actively condensed and captured on the moisture-permeable membrane surface, and the moisture-permeable membrane automatically increases its moisture permeability, releasing water vapor and moisture to the outside of the drying chamber at an appropriate rate.

Description

Technical Field

[0001] The present invention relates to a drying treatment chamber for making dried fruits, dried vegetables, dried foods, etc. at home, or a refrigerator-freezer with a drying function equipped with a drying treatment container or the like.

Background Art

[0002] Conventionally, as techniques for making dried foods, the sun-drying method, the cold-air drying method, the heat-drying method, and the vacuum-freezing drying method have been mainstream. However, each has its own advantages and disadvantages, and the drying method is properly selected depending on the food type, usage, and processing amount.

[0003] The sun-drying method is a drying method that has been used since ancient times as a method for making dried radishes and dried persimmons. It is a method of drying over time using natural environments such as sunlight, temperature, humidity, wind, etc. It does not require a special device for processing, and can dry a large amount of foodstuffs relatively inexpensively. However, it takes a long time to dry, and there is a major problem that the quality fluctuates and lacks stability due to the degree of change in light, temperature, humidity, wind, etc. in the natural environment.

[0004] The cold-air drying method is a drying method widely used for dried products of fresh products. As shown in Patent Document 1, cooled and dried air is circulated to evaporate moisture. It is carried out in a relatively low-temperature space of 5°C to 35°C, preventing rapid deterioration of food, not being affected by the weather like sun-drying, and being relatively inexpensive compared to other drying methods. However, the problem of a long drying treatment time remains. Without an independent cooling system and drying space for drying, the odor of the foodstuffs to be dried spreads in the storage, so it is difficult to share with a household refrigerator-freezer where foodstuffs are mixed. If it becomes an independent household cold-air drying storage, the amount of food consumed by a household in a day is small, and the equipment cost becomes high, making it uneconomical in terms of price.

[0005] The heat drying method is commonly used for drying vegetables and fruits. It involves exposing the food to be dried to a heated space using an electric heater or similar device, forcibly evaporating the moisture within the food, and enabling a quick drying process. While the equipment is relatively inexpensive, it requires a large amount of energy for heating, and the heat can lead to the decomposition of nutrients in the food, oxidative deterioration of the food's structure and components, and changes in color, posing challenges to maintaining initial quality.

[0006] Vacuum freeze-drying, also known as freeze-drying, is a drying method that utilizes sublimation—the transformation of ice into steam—by subtly heating rapidly frozen food under high vacuum. It is commonly used for instant foods. This method minimizes changes in the food's components, maintains food quality, and allows for relatively quick drying of food for long-term storage. Furthermore, because the frozen food is dried under reduced pressure, many pores remain, allowing the dried product to be easily restored by adding water or hot water. However, the specialized machinery and equipment required to create the vacuum are expensive, so it is typically used in industrial production for drying large quantities of food. For small-scale production, the depreciation costs of the equipment impact processing costs, making it unsuitable for home use.

[0007] Furthermore, a recent freeze-drying technology has proposed a freeze-drying method at atmospheric pressure that does not involve reduced pressure or vacuum. Non-patent document 1 introduces the potential of atmospheric pressure freeze-drying as a recent food manufacturing technology. The main points are that the food to be freeze-dried is frozen, and then dry air at a temperature slightly higher than the food temperature is controlled and sent to the surface of the food to be freeze-dried, causing sublimation drying. Drying by sublimation due to the difference in water vapor partial pressure has a sublimation rate close to that of reduced pressure, and since it does not require equipment costs for vacuum or reduced pressure, as well as power consumption for reduced pressure, the processing cost is low. In addition, it is stated that, depending on the degree of drying, the texture may be improved and the taste may be better depending on the food.

[0008] However, whether using vacuum freeze-drying or atmospheric pressure freeze-drying, while the low temperatures of freezing can suppress the decomposition of food components and nutrients, the tissues of fresh vegetables and other foods are inevitably damaged to some extent by freezing. Furthermore, pectin, which connects cells, is also damaged, resulting in a significant softening and change in texture after thawing. Additionally, while freezing and drying suppresses shrinkage, many pores remain after water is removed, and when dry air enters these pores, oxidation is more likely to occur due to the reaction with oxygen. Therefore, freeze-dried foods cannot always be said to have stable quality. Moreover, sublimation drying, due to its inherently low temperature, cannot achieve a large water vapor pressure difference, resulting in long processing times, which remains a challenge.

[0009] In other words, drying methods can be broadly categorized into those that involve exposing ingredients with high moisture content to a low-humidity natural environment or cool air, such as sun drying or cold air drying, utilizing the difference in humidity resulting from the difference in water vapor partial pressure; those that increase the evaporation rate by heating the ingredients to raise the absolute humidity at the ingredient interface above that of the outside air, thereby increasing the rate of evaporation; and those that facilitate the evaporation and sublimation of moisture within the ingredients by reducing the pressure or creating a vacuum in the environment where the ingredients are placed. While there are also methods that utilize osmosis for moisture extraction, these have the drawback of altering the taste of the ingredients depending on the moisture absorbent material they come into contact with. Therefore, it can be said that the general drying process involves using a combination of methods to control humidity differences, temperature differences, and pressure differences.

[0010] In particular, for home food drying devices, the heating and drying method, which directly applies a heat source or hot air to the food, is the simplest and fastest way to produce dried food, and many home heating-type food dehydrators have been commercialized. However, heating at high temperatures of 35°C or higher causes severe oxidative deterioration of food, not only accelerating discoloration and the breakdown of nutrients, but also posing a major problem of food spoilage by microorganisms, and improvements in this area are desired.

[0011] Therefore, various methods have been proposed through trial and error to dry food items inside a refrigerator or freezer by utilizing the dehumidifying function of the evaporator in the refrigeration system, which removes moisture from the refrigerator and creates a low-humidity environment.

[0012] For example, as a drying chamber to be installed in a refrigerator, Patent Document 2 introduces a refrigerator with a drying chamber that has a cooling plate at the top that comes into contact with cold air, a heating device at the bottom, and is mostly covered with insulating material, and is installed in a part of the path through which cold air circulates inside the refrigerator, and the condensed moisture inside the drying chamber that is absorbed by the cooling plate is connected to the passage of cold air that is inside and outside the drying chamber by a desiccant that absorbs water.

[0013] In other words, by removing moisture inside the drying chamber by condensing it on the surface of the cooling plate, the humidity inside the drying chamber is reduced. The moisture condensed on the cooling plate is then absorbed by a desiccant that connects the inside of the drying chamber to the cold air passage outside. The absorbed moisture is then automatically discharged into the cold air circulation path inside the refrigerator, where the humidity is low, allowing for drying. This simple structure enables dehumidification inside the drying chamber, and because it is semi-sealed, odors from the dried food do not transfer from the drying chamber to other parts of the chamber, allowing the food to be stored in a dry state.

[0014] Furthermore, Patent Document 3 describes a refrigerator with a drying chamber that cools the surrounding air by evaporating a refrigerant compressed by a compressor in an evaporation section and circulating the cooled air, comprising: a cooling plate that forms part of the wall of the drying chamber and cools and condenses moisture inside the drying chamber; a moisture-absorbing member that is provided so that one side is in contact with the atmosphere inside the drying chamber and the other side is in contact with the atmosphere outside the drying chamber, has moisture permeability and evaporates the moisture condensed by the cooling plate to the outside of the drying chamber; a heating means for heating the inside of the drying chamber; and a heating control means for controlling the heating of the heating means according to the temperature of the cooled air, or a supply control means for controlling the supply of cold air.

[0015] In other words, as an added benefit to Patent Document 2, a heating control means that controls the heating of the heating means according to the temperature of the cold air, or a supply control means that controls the supply of cold air, is provided, so that the temperature of the drying chamber can be kept almost constant, and by controlling the supply of cold air to the vicinity of the drying chamber, the temperature inside the drying chamber can be kept even more constant.

[0016] Furthermore, Patent Document 4 introduces a refrigerator in which a drying chamber installed in the refrigerator compartment has a damper for the drying chamber that adjusts the airflow of cold air forcibly blown by a blower fan, a humidity sensor that detects the humidity inside the drying chamber, and a heater, and the refrigerator compartment and drying chamber are cooled by cold air forcibly blown by a blower fan, and the humidity of the drying chamber is controlled to a predetermined level by the humidity sensor, the damper for the drying chamber, and the heater.

[0017] In other words, by installing a humidity sensor inside the drying chamber and using forced-air cooling from a fan and a heater, a drying chamber can be created that maintains a constant low humidity level. This allows for drying with minimal deterioration of food components due to the stable temperature and humidity.

[0018] Furthermore, Patent Document 5 describes a refrigerator with a vacuum drying function, which has a freezer compartment and a refrigerator compartment, and includes a drying compartment equipped with a heating source for storing food to be dried, and a steam condensation compartment equipped with a steam condenser, which is integrated with or connected to the drying compartment, located inside the refrigerator compartment, a vacuum pump provided outside the compartment to create a vacuum in the drying compartment and the steam condensation compartment, a vacuum drying cycle that passes through the steam condenser, running in parallel with the freezing and refrigeration cycle that cools the freezer compartment and the refrigerator compartment, and a switch that can switch between freezing and refrigeration mode and vacuum drying mode. When making vacuum-dried food, the food to be dried is stored in the drying compartment, and the switch is turned to vacuum drying mode, which causes the refrigerant to flow to the vacuum drying cycle, drives the vacuum pump, sublimes the ice portion of the food to be dried by the heating source, and removes the water vapor generated by this sublimation by the steam condenser.

[0019] In other words, it involves attaching a vacuum freeze-drying device to a household refrigerator or freezer, and drying frozen food by sublimation while heating it. If it can be put into practical use, it would be an ideal drying method for maintaining food quality. [Prior art documents] [Non-patent literature]

[0020]

Non-Patent Document 1

Patent Documents

[0021]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0022] However, in the drying chamber mounted in the refrigerator disclosed in Patent Document 2, the moisture condensed on the cooling plate is absorbed by a moisture absorbent that communicates the inside of the drying chamber with the passage side of the cold air outside, and the absorbed moisture is automatically discharged to the path where the cold air in the refrigerator with low humidity circulates for drying. However, if the amount of the material to be dried is large and the amount of condensation on the cooling plate is large, the moisture absorbent cannot handle all of it, and a large amount of water will remain inside the drying chamber. Also, if the cooling plate area is reduced and the amount of the moisture absorbent is increased, the temperature inside the drying chamber will rise, so control of the heating device is required, and there is a problem that the drying time becomes long. The material used as the moisture absorbent is formed of a bundle of fibers such as synthetic fiber and cotton, or a hydrophilic resin or a sponge-like substance, etc. Due to capillary action, moisture freely penetrates, but it has a high heat insulation property and is a material through which cold air and warm air cannot flow. Therefore, there is a problem that outside the drying chamber where the cold air in the refrigerator circulates, it may become below 0°C, and the moisture absorbent may freeze, making it impossible to move moisture.

[0023] Also, even if heating control means for controlling heating according to the temperature of cold air or feed control means is provided as in the drying treatment chamber disclosed in Patent Document 3 so that the temperature in the drying chamber can be kept constant, the amount of moisture discharged varies depending on the amount of the food material to be dried stored in the drying chamber. Thus, when the amount of the food material to be dried is large, the amount of moisture discharged increases and water stays in the drying chamber. When the amount of the food material to be dried is small, the influence of the cooling plate becomes large and an excessive amount of heat of the heating control means is required for heating the cooling plate and the drying treatment chamber.

[0024] Also, the material used as the moisture absorbent is the same as that in Patent Document 2 and is formed of a bundle of fibers such as synthetic fiber and cotton, or a hydrophilic resin or sponge-like substance. Moisture can freely penetrate due to capillary action between the fibers, but it has a high heat insulation property and is a material through which cold air or warm air cannot circulate. Therefore, it may be below 0°C outside the drying chamber where the cold air in the refrigerator circulates, and the moisture absorbent may freeze, leaving the problem that moisture movement becomes impossible.

[0025] Also, although it is a problem common to Patent Document 2 and Patent Document 3, the humidity condition in the drying chamber is the water vapor pressure at a dew point temperature of 0°C and a relative humidity of 100%. Even if the food material to be dried is heated to 30°C by heating means, at the same water vapor pressure, the relative humidity value is still quite high and it cannot be said to be sufficient drying conditions, and the drying time also becomes long.

[0026] Also, in the drying chamber installed in the refrigerator disclosed in Patent Document 4, a humidity sensor is attached in the drying chamber, and it becomes a drying chamber that can maintain a certain humidity by cold air forcedly blown by a blower fan and a heater. However, in such a fan cooling type drying chamber, since the refrigerator and the drying chamber are cooled by cold air forcedly blown by the same blower fan, the odor of the food material to be dried generated in the drying chamber spreads into the refrigerator and the freezer, and odor transfer to other foods and ice becomes a major problem.

[0027] Furthermore, the refrigerator-freezer with a vacuum drying function disclosed in Patent Document 5 is equipped with a vacuum pump that creates a vacuum between a drying chamber with a heating source for storing food to be dried and a steam condensation chamber, and sublimes the ice portion of the food to be dried by switching the vacuum drying mode. Since drying is done by sublimation, it can be said to be an ideal drying method for maintaining food quality, but to install it in a general household refrigerator-freezer, a vacuum pump, a mode switching device, and a separate condenser are required, resulting in a complex structure, problems with pump noise, handling when opening and closing the door of the drying chamber which is under reduced pressure, and the fact that drying by sublimation takes a very long time.

[0028] The present invention was made to solve the above problems, and aims to provide a refrigerator with a drying function that increases the drying speed while maintaining the quality of food, by equipping a drying chamber or drying container, etc., that can be attached to a general household refrigerator at low cost and with ease. [Means for solving the problem]

[0029] Therefore, the present invention uses a breathable waterproof material, also used in outdoor leisure clothing, that does not allow water to pass through but does allow water vapor and moisture to pass through—a so-called breathable membrane—as a partition for the cold air shielding wall of a drying chamber. By controlling the temperature, humidity, and the amount of water vapor and moisture passing through the drying chamber, the present invention creates optimal drying conditions for a drying chamber inside a refrigerator. In this text, the terms water vapor, moisture, moisture, condensation water, and water are used, but water vapor and moisture refer to a moist gaseous state, condensation water and water refer to a liquid state, and moisture refers to the molecular state of water. Therefore, the breathable membrane allows water vapor and moisture to pass through, but liquid condensation water and water do not pass through as they are. Permeation amount refers to the amount that passes through as is in a gaseous state, as well as the amount that condenses from water vapor, the condensation water penetrates the breathable membrane to become water molecules, and then those water molecules evaporate again as water vapor on the opposite side.

[0030] Typical moisture-permeable membrane resin materials include hydrophilic urethane-based resin films, which exhibit a significant change in moisture permeability depending on the glass transition temperature (Tg). This is because, in the glass temperature region below the Tg, the molecular structure becomes crystalline and dense, while in the rubbery temperature region above the Tg, the molecular structure loosens, increasing moisture permeability. Since the moisture permeability remains almost the same with good reproducibility even when the temperature is repeatedly fluctuated around the Tg, by designing polymers with appropriate moisture permeability and glass transition temperature (Tg) for refrigeration temperatures, this property of the moisture-permeable membrane can be utilized to create optimal drying conditions inside a refrigerator.

[0031] This hydrophilic urethane resin film, which is the most common type of moisture-permeable membrane, has another important property: in a condensation state, the membrane absorbs a large amount of moisture and promotes evaporation across its entire surface, resulting in a significant increase in moisture permeability. Therefore, when condensation occurs on the inside of the moisture-permeable membrane due to the temperature and humidity difference between the drying chamber and the refrigeration chamber, the amount of moisture movement within the membrane becomes extremely large and is discharged outside the drying chamber as vapor. As a result, condensation water does not drip into the drying chamber, and moisture can be smoothly transferred to the refrigeration chamber. This moisture-permeable membrane is a non-porous membrane; while water molecules can move within the polymer, it is not permeable, and there is no movement of liquid water, air, or odor components.

[0032] Furthermore, a moisture-permeable membrane made of hydrophilic urethane resin film, whose glass transition point Tg (the point at which it changes from a glassy region to a rubbery region) is molecularly designed for the refrigeration temperature range, is laminated as a film onto a nylon or polyester woven or nonwoven base fabric. This membrane is then interposed as a partition at the interface between the inside and outside of the upper ceiling shielding wall of the drying chamber. Heating means such as electric heaters at the lower bottom of the drying chamber actively condense and capture water vapor and moisture from the food being dried on the moisture-permeable membrane surface, causing the membrane to automatically increase its moisture permeability and release an appropriate amount of moisture to the outside of the drying chamber.

[0033] This allows for a sealed drying chamber, preventing odor transfer from the food being dried to other refrigerators. Furthermore, the amount of moisture permeability of the permeable membrane changes with temperature fluctuations in the drying chamber, and the amount of moisture absorbed by condensation ensures that the permeability is at an appropriate level. Additionally, by optimizing the insulation performance of the woven or non-woven base material and the cold air shielding wall, the temperature inside the drying chamber is made uniform at a predetermined temperature, thereby providing a refrigerator-freezer with a drying function that can accelerate drying.

[0034] In other words, in order to solve the above problems, the first aspect of the present invention provides a refrigerator with a drying function, which is provided in a refrigerator compartment that is cooled by a cold air circulation air that has been heat-exchanged by a cooler in the freezing temperature range, and a drying processing chamber that is cooled by the cold air circulation air through a cold air shielding wall, which forms a sealed space surrounded by the cold air shielding wall, and the sealed space has a breathable storage shelf such as a mesh on which food to be dried can be placed, a heating means such as an electric heater that heats the sealed space to a predetermined temperature from the bottom, and a temperature detection control means for the sealed space that controls the heating means, and a part of the cold air shielding wall has an opening and closing mechanism shielding wall that allows the food to be dried or the storage shelf to be put in and taken out, and a humidity control window is provided in a part of the upper top shielding wall of the drying processing chamber, which has a moisture-permeable membrane or a moisture-permeable membrane multilayer as a partition surface that allows only water vapor and moisture to pass through.

[0035] In this refrigerator with a drying function, the circulating cold air, cooled by heat exchange in the refrigeration temperature range cooler, has its moisture removed as condensation or frost on the cooler surface, resulting in a very low humidity environment. For example, if the refrigeration temperature range in the cooler is set to -25°C and the refrigerator compartment is cooled to a refrigeration temperature range of 5°C by the circulating cold air, the relative humidity inside the refrigerator compartment will be approximately 10% according to calculations using Tetens' equation for saturated water vapor partial pressure.

[0036] Furthermore, since the drying chamber, which is cooled through a cold air barrier wall, is a sealed space with a cold air barrier wall, odors will not transfer to food or ice in other refrigerator or freezer compartments during the drying process of food items in the drying chamber.

[0037] Furthermore, by providing an opening and closing mechanism for a shielding wall in part of the cold air shielding wall of the drying chamber, and allowing breathable mesh or similar storage shelves for placing the food to be dried to be freely inserted and removed, the loading and storage of the food to be dried can be made simpler and more efficient. Also, by using a heating means from the lower bottom of the drying chamber, heat can pass directly through the mesh and diffuse, allowing the entire sealed space of the drying chamber to be heated uniformly and efficiently.

[0038] Furthermore, the cold air shielding walls surrounding the drying chamber, excluding the humidity control windows, are made of thick materials such as ceramics or plastics that have appropriate thermal insulation properties. The humidity control windows installed in the cold air shielding walls at the top are made of thin, permeable membranes or multi-layered permeable membranes with poor thermal insulation properties. As a result, water vapor evaporating and diffusing from the surface of the food being dried is preferentially condensed on the partition surface of the humidity control window made of permeable membranes or multi-layered permeable membranes, allowing water vapor to be efficiently released outside the drying chamber through the humidity control windows.

[0039] As mentioned earlier, the hydrophilic urethane resin film used in this moisture-permeable membrane has the property of significantly increasing its moisture permeability when it condenses and absorbs water. Therefore, even if the temperature inside the drying chamber becomes higher than the temperature inside the refrigerator and a large amount of moisture evaporates from the food being dried, the moisture permeability is automatically increased, preventing condensation from dripping into the drying chamber and enabling continuous and stable control of the drying humidity.

[0040] Furthermore, the temperature of the sealed space in the drying chamber is detected by a temperature detection and control means, and the heating means is controlled to continuously adjust the temperature inside the drying chamber to a stable level. This ensures a temperature gradient and humidity gradient with the refrigeration chamber, promoting a stable and smooth drying process.

[0041] Furthermore, a refrigerator with a drying function according to a second aspect of the present invention is characterized in that the moisture-permeable membrane multilayer is formed by laminating a hydrophilic moisture-permeable resin film that forms the moisture-permeable membrane onto a breathable base fabric, or by coating it with a hydrophilic moisture-permeable resin.

[0042] In this refrigerator-freezer with a drying function, the moisture-permeable membrane multilayer structure exhibits high thermal insulation when the base fabric and moisture-permeable membrane are dry, and decreased thermal insulation when the base fabric and moisture-permeable membrane are wet due to increased heat conduction caused by condensation. By utilizing this function of the base fabric's changing thermal insulation properties, when the base fabric is dry, the increased thermal insulation prevents heat from the drying chamber from transferring to the refrigerator chamber, effectively maintaining the temperature inside the drying chamber. When wet, the increased heat conduction promotes condensation on the moisture-permeable membrane inside the drying chamber, accelerating evaporation to the outside of the drying chamber.

[0043] Furthermore, by creating a multi-layer structure, the resin film of the moisture-permeable membrane can be reinforced, increasing its structural strength. It can also be integrally molded with a resin structure that acts as a shielding wall for cold air circulation, making the assembly and maintenance of the drying chamber easier and resulting in a user-friendly and inexpensive structure. The manufacturing method can be either lamination using adhesive or coating without adhesive. However, although the adhesive affects the moisture permeability, lamination of the resin film of the moisture-permeable membrane is recommended to form a stable film thickness.

[0044] Furthermore, in a third aspect of the present invention, the refrigerator with a drying function is characterized in that the resin material of the moisture-permeable membrane is a hydrophilic urethane-based resin film whose glass transition point Tg is set near the refrigeration temperature range of 0°C to 10°C, the base fabric is a breathable woven or nonwoven fabric such as nylon or polyester, and the moisture-permeable membrane multilayer is formed by laminating the base fabric and the moisture-permeable membrane via adhesive layers scattered at appropriate intervals.

[0045] With this refrigerator-freezer with a drying function, the glass transition temperature (Tg) is molecularly designed to be within the refrigerator compartment temperature range. Therefore, when the temperature of the drying chamber becomes higher than the temperature of the refrigerator compartment, and the humidity decreases to the point where condensation does not occur, the thermal insulation of the base fabric facing the refrigerator compartment increases, the temperature of the moisture-permeable membrane rises, and the amount of moisture permeability also increases. As a result, the drying process proceeds relatively smoothly while maintaining the temperature of the drying chamber.

[0046] Furthermore, when the temperature of the drying chamber or moisture-permeable membrane is in the range of 0°C to 10°C, or even lower, and the humidity is below the dew point, the amount of moisture permeation is not large, evaporation to the refrigerator side is suppressed, and the energy from the heating means at the bottom is used only to heat the drying chamber, allowing the heating of the drying chamber to proceed efficiently. If the heating means is stopped, it can be applied as a vegetable compartment where humidity is maintained.

[0047] Furthermore, by laminating adhesive layers at appropriate intervals, a resin film with a stable thickness can be used as the moisture-permeable membrane, and the influence of the adhesive on moisture permeability can be eliminated by widening the spacing between the adhesive layers.

[0048] Furthermore, the refrigerator-freezer with drying function according to the fourth aspect of the present invention is characterized in that the drying chamber is set to have the lowest thermal insulation performance compared to the thermal insulation performance of the cold air shielding wall that forms the sealed space, and the thermal insulation performance of the moisture-permeable membrane or moisture-permeable membrane multilayer that forms the partition surface of the humidity-regulating window is set to the lowest.

[0049] In this refrigerator-freezer with a drying function, the partition surface of the humidity control window has the lowest thermal insulation performance among the wall surfaces that make up the drying chamber, and is set to conduct heat the most easily compared to other cold air shielding wall sections. Therefore, the surface temperature of the inner side of the cold air shielding wall is lowest at the moisture-permeable membrane or moisture-permeable membrane multilayer surface that forms the partition surface of the humidity control window. As a result, condensation concentrates on the moisture-permeable membrane portion of the partition surface of the humidity control window, and the amount of moisture permeable through the moisture-permeable membrane increases, allowing moisture from the inside to move to the outside efficiently. This virtually eliminates condensation on other wall surfaces and prevents food spoilage due to excess moisture, enabling safe and secure drying.

[0050] In a refrigerator-freezer equipped with a drying function that meets the above requirements, simply placing the food to be dried in the drying chamber and pressing the start button for the drying operation will cause the drying chamber to be heated to a predetermined temperature by an efficient heating means from the bottom. The heating from below will cause the moisture in the food to evaporate, and the drying will proceed smoothly by utilizing the temperature difference and water vapor partial pressure difference between the front and back surfaces of the moisture-permeable membrane or moisture-permeable membrane multilayer on the partition surface of the coolest humidity control window. [Effects of the Invention]

[0051] As described above, by using a moisture-permeable membrane to create a sealed drying chamber, there is no transfer of odors from the food being dried to other freezers or refrigerators. Furthermore, instead of drying by forced airflow, the drying process efficiently utilizes the diffusion force of the water vapor partial pressure difference, enveloping the surface of the food being dried in moisture while drying at low temperatures. This suppresses changes in color, nutrients, and tissue components, and provides a freezer with a drying function that can easily, quickly, and inexpensively produce high-quality dried food. [Brief explanation of the drawing]

[0052] [Figure 1] This is a cross-sectional view of a refrigerator with a drying function according to the first embodiment. [Figure 2] This is a plan view from above of a humidity control window having a moisture-permeable membrane multilayer partition surface, which is attached to the upper ceiling shielding wall of the drying chamber according to the first embodiment. [Figure 3] This is a cross-sectional view (a)-(a) of the drying chamber according to the first embodiment. [Figure 4] This is an enlarged cross-sectional view (a)-(a) of the upper ceiling shielding wall of the drying chamber according to the first embodiment, including the humidity control window. [Figure 5] This is a cross-sectional view showing the removal of a storage shelf containing food items to be dried from the drying chamber according to the first embodiment. [Figure 6] This is a cross-sectional view showing the drying chamber after the food to be dried has been placed according to the first embodiment. [Figure 7] This graph shows the change in moisture permeability with temperature between hydrophilic urethane resin films with different glass transition points (Tg) that form the moisture permeable membrane of the moisture permeable membrane multilayer structure according to the first embodiment. [Figure 8] This is a comparison table showing the results of measuring the moisture permeability of hydrophilic urethane resin films with different glass transition points (Tg) that form the moisture permeable membrane of the moisture permeable membrane multilayer structure according to the first embodiment. [Figure 9]This illustration illustrates the function of moisture movement on the surface of the moisture-permeable membrane of a humidity-regulating window provided as a partition surface in the upper ceiling shielding wall of the drying chamber according to the first embodiment. (1) shows the state of the moisture-permeable membrane immediately after storing the food to be dried, or after it has been refrigerated and stabilized. (2) shows the state when water vapor has condensed on the moisture-permeable membrane. (3) is a cross-sectional illustration showing the state when the degree of drying of the food to be dried has progressed, and condensation on the moisture-permeable membrane has disappeared at a humidity below the water activity Aw value. [Figure 10] This is a cross-sectional view of a refrigerator with a drying function according to a second embodiment. [Figure 11] (1) is a plan view of the drying chamber for storing food to be dried according to the second embodiment, and (2) is a cross-sectional view taken along (b)-(b). [Figure 12] This is a cross-sectional view showing the state in which the food to be dried is placed in the drying chamber according to the second embodiment and assembled as a drying chamber. [Figure 13] This is a cross-sectional view of a refrigerator with a drying function when the drying chamber according to the second embodiment has been removed. [Modes for carrying out the invention]

[0053] Hereinafter, specific embodiments of the refrigerator-freezer with drying function of the present invention will be described with reference to Figures 1 to 13. The technical scope of the present invention is not limited to these embodiments, and modifications can be made as appropriate, as long as they do not contradict the spirit of the invention.

[0054] Figure 1 is a cross-sectional view mainly of the drying chamber 11 of a refrigerator-freezer 10 with a drying function according to the first embodiment of the present invention, and Figure 2 is a plan view from above of a humidity control window 16 provided with a moisture-permeable membrane multilayer body 15 consisting of a moisture-permeable membrane 13 and a base fabric 14, which is attached to the upper ceiling shielding wall 12 of the drying chamber 11 according to the first embodiment. Figure 3 is a cross-sectional view of the drying chamber 11 from (a)-(a). Figure 4 is an enlarged cross-sectional view of the drying chamber 11 from (a)-(a) including the humidity control window 16 provided as a partition surface of the upper ceiling shielding wall 12. Figure 5 is a cross-sectional view showing the opening and closing mechanism shielding wall 17 of the drying chamber 11 being opened to remove the storage shelf 18, and Figure 6 is a cross-sectional view showing the storage shelf 18 in its fixed position inside the drying chamber 11 after the food items to be dried 19 have been set.

[0055] Figure 7 is a graph showing the change in moisture permeability with temperature for hydrophilic urethane resin films with different glass transition points Tg, which constitute the moisture permeable membrane 13 of the moisture permeable membrane multilayer 15. Figure 8 is a comparison table showing the results of measuring the moisture permeability of various hydrophilic urethane resin films with different glass transition points Tg, which constitute the moisture permeable membrane 13 of the moisture permeable membrane multilayer 15, using the A-1 and B-1 methods of JIS-L1099.

[0056] Figure 9 is an illustration illustrating the function of moisture movement on the surface of the moisture-permeable membrane 13 of the humidity-regulating window 16, which is provided as a partition surface of the upper ceiling shielding wall 12 of the drying chamber 11. (1) shows the state of the moisture-permeable membrane 13 immediately after storing the food to be dried 19, or when it has stabilized after being refrigerated. (2) shows the state when water vapor has condensed on the moisture-permeable membrane 13. (3) is an illustrated cross-sectional view showing the state when the degree of drying of the food to be dried 19 has progressed and condensation on the moisture-permeable membrane 13 has disappeared at a humidity below the water activity Aw value.

[0057] First, the configuration of the refrigerator-freezer 10 with drying function according to the first embodiment will be described sequentially with reference to Figures 1 to 8.

[0058] The refrigerator-freezer 10 with a drying function consists of a freezer compartment 20, a refrigerator compartment 21, and a drying compartment 11. The freezer compartment 20, the refrigerator compartment 21, and the drying compartment 11 are cooled by a refrigeration system 26 in which a refrigerant consisting of a compressor 22, a condenser 23, an expansion valve 24, and an evaporator 25 circulates, and by a cooling fan 27 that generates a cold air circulation wind 28.

[0059] In other words, the refrigerant flowing through the refrigeration system 26 is first pressurized by adiabatic compression in the compressor 22 as a gaseous refrigerant. The high-temperature gaseous refrigerant is then cooled by the outside air in the condenser 23 and liquefied. Next, as the liquefied refrigerant passes through the expansion valve 24, its pressure decreases and it vaporizes in the evaporator 25, absorbing heat of vaporization from the surroundings and cooling the evaporator 25. The vaporized refrigerant returns to the compressor 22, and the compressed, high-temperature refrigerant is sent to the condenser 23, thus circulating sequentially throughout the refrigeration system 26.

[0060] In the general description of the refrigeration system 26, the evaporator 25 is described as the component through which the refrigerant circulating within the refrigeration system 26 evaporates. However, when the evaporator 25 is cooled by heat exchange between the outer surface of the evaporator 25 and the cold air circulation 28 formed by the cooling fan 27 that flows between the freezer compartment 20 and the refrigerator compartment 21 of the refrigerator-freezer 10, the evaporator 25 shall be referred to as the cooler 25.

[0061] The outer surface temperature of the cooler (evaporator) 25 can be set to the evaporation temperature by the expansion valve 24, and the evaporation temperature of a typical refrigerator is in the range of -25°C to -30°C. When the cooling fan 27 is operated, the cold air circulation air 28 indicated by the arrow flowing inside the refrigerator 10 flows through the evaporator space 29 in which the cooler 23 is installed, and heat exchange occurs between the cold air circulation air 28 and the surface of the cooler 25. Furthermore, the cold air circulation air 28 circulates inside the refrigerator 10 through airflow control by the ductwork 41 and the refrigerator damper thermo 42, etc., cooling the refrigerator compartment 21 to the refrigeration temperature range of approximately 5°C and the freezer compartment 20 to the freezing temperature range of approximately -25°C.

[0062] The cold air circulating within the refrigerator compartment 21 flows around the drying chamber 11, which has a sealed space 35 surrounded by a cold air shielding wall 30 installed within the refrigerator compartment 21. As the cold air comes into contact with the cold air shielding wall 30, the drying chamber 11 is indirectly cooled by wall cooling.

[0063] Furthermore, the material used to form the cold air shielding wall 30 of the drying chamber 11 is hard plastic or ceramic material. To improve insulation, the thickness of the cold air shielding wall 30 may be increased, and foamed plastic material may also be used.

[0064] The drying chamber 11, which has a sealed space 35 surrounded by a cold air shielding wall 30, is a sealed box structure, but the front of the drying chamber 11 has an opening and closing mechanism shielding wall 17, and the cold air shielding wall 30 of the upper ceiling shielding wall 12 of the drying chamber 11 has a humidity control window 16 provided as a partition surface formed by integrally molding a moisture-permeable membrane multilayer body 15 of a moisture-permeable membrane 13 and a base fabric 14.

[0065] Furthermore, a heating means 32, such as an electric heater, is installed on the lower bottom surface 31 of the sealed space 35 of the drying chamber 11, and by coordinating with the temperature detection and control means 33 of the sealed space 35 of the drying chamber 11, the temperature of the sealed space 35 of the drying chamber 11 can be controlled.

[0066] Furthermore, the sealed space 35 of the drying chamber 11 has a ventilated mesh storage shelf 18 for storing the food items to be dried 19. The shelf can be easily removed by opening the opening / closing mechanism shielding wall 17, and when stored in the drying chamber 11, it is set to be located in the center of the upper surface of the electric heater of the heating means 32 on the lower bottom surface 31.

[0067] The moisture-permeable membrane multilayer body 15, which is attached as a partition surface to the humidity control window 16 of the upper ceiling shielding wall 12 of the drying chamber 11, is formed by bonding a moisture-permeable membrane 13 made of a hydrophilic urethane resin film with a partially crystalline molecular structure of a non-porous membrane to a base fabric 14 made of a breathable woven fabric or nonwoven fabric made of breathable nylon or polyester fiber material, via adhesive layers scattered at appropriate intervals.

[0068] This urethane resin film has the function of suppressing water vapor permeability at low temperatures below the glass transition temperature (Tg) because the gaps between resin molecules contract, and improving water vapor permeability at high temperatures above the glass transition temperature (Tg) because the molecular motion of the amorphous phase of the resin becomes more active, causing the gaps between resin molecules to expand and facilitating the diffusion of water vapor molecules.

[0069] To control the glass transition temperature (Tg), it is necessary to synthesize polyurethane by varying the ethylene oxide concentration of the polyurethane, the molecular weight of the polyol, etc., and to create an appropriate moisture permeability and glass transition temperature (Tg) according to the drying conditions. In this invention, a polymer material with a glass transition temperature (Tg) in the refrigeration temperature range of 0°C to 10°C was selected.

[0070] As one example, curve (a) in Figure 7 shows the result of measuring the moisture permeability at a predetermined temperature for a urethane resin film with a glass transition point Tg of 0°C to 10°C, indicating a rapid increase in moisture permeability once the ambient temperature exceeds 10°C. Curve (b) is the moisture permeability curve for a urethane resin film with a glass transition point Tg of -30°C, showing no significant change in moisture permeability even at temperatures above 20°C.

[0071] Furthermore, because the urethane resin film of the moisture-permeable membrane 13 is hydrophilic, the large dissolution of water vapor molecules has a synergistic effect, resulting in a moisture-permeable membrane 13 that exhibits a rapid increase in moisture permeability in condensation environments where the surface of the urethane resin film of the moisture-permeable membrane 13 becomes wet.

[0072] The comparison table in Figure 8 shows the results of measuring the moisture permeability of various urethane resin films through the moisture permeable membrane 13 using the moisture permeability measurement method of JIS-L1099, comparing the results measured using method A-1 and method B-1.

[0073] The main difference between the A-1 and B-1 measurement methods is that the A-1 method measures moisture permeability through a moisture-permeable membrane 13 using 90% atmospheric air and a calcium chloride desiccant at 40°C, while the B-1 method measures moisture through a moisture-permeable membrane 13 using a potassium acetate solution (a desiccant) and water at 23°C. The difference lies in whether the comparison surface of the moisture-permeable membrane 13 is immersed in water or in air.

[0074] The results from the comparison table in Figure 8 show that, regardless of the difference in glass transition temperature (Tg), the moisture-permeable membrane 13 of the hydrophilic urethane resin film shows a 2 to 6 times difference between the results in air and the results when immersed in water, indicating that the moisture permeability of the moisture-permeable membrane 13 increases when wetting occurs. Considering that the measurement temperatures for Method A-1 and Method B-1 were 40°C and 23°C, the moisture permeability is higher in Method B-1 due to the lower temperature, suggesting that temperature does not have an effect.

[0075] It should be noted that Method B-1 uses potassium acetate solution and water at 23°C, and it is thought that this method takes into account the water permeability due to osmotic pressure caused by the difference in potassium acetate concentration. However, in a separate experiment conducted in a 10°C environment, where the temperature of water in a cup was changed from 10°C to 30°C and condensation occurred on the water-permeable membrane 13 covering the cup, the amount of water permeability was measured. At 20°C, the amount of water permeability was 4 to 5 times higher than at 10°C, and at 30°C, it was about 10 times higher. This confirmed that the improvement in water permeability under condensation conditions is an undeniable fact.

[0076] Furthermore, the refrigerator-freezer 10 with drying function consists of an insulated box 38, a freezer door 39, and a refrigerator door 40, which together form the freezer compartment 20 and the refrigerator compartment 21. The control device 37 for controlling the temperature inside the drying compartment 12 is mounted on the front of the refrigerator door 40.

[0077] Furthermore, the cold air circulation air 28 to the refrigerator compartment 21 is supplied by a cooling fan 27 through a ductwork 41 at the back of the refrigerator compartment 21, passing through the outlet of the damper thermo 42, circulating within the refrigerator compartment 21, and returning to the evaporative space 29 through the intake port 43.

[0078] Next, the operation of this refrigerator-freezer 10 with a drying function will be explained, including with reference to Figure 9.

[0079] When the power cord (not shown) of the refrigerator-freezer with drying function 10 is connected to the commercial power supply, the compressor 22 starts operating, and the refrigerant in the refrigeration system 26 is compressed in the compressor 22, becoming high temperature and high pressure, and moves to the condenser 23. The high temperature and high pressure refrigerant transported to the condenser 23 is cooled by the low temperature outside air, its temperature drops, and it liquefies. Next, after passing through the expansion valve 24, the refrigerant vaporizes in the evaporator 25 as its pressure drops rapidly, absorbing heat of vaporization and cooling the evaporator 25. The refrigerant, now at a reduced pressure, returns to the compressor 22, is compressed again, becomes high temperature and high pressure, and circulates within the refrigeration system 26.

[0080] Next, by operating the cooling fan 27, a cold air circulation air 28 is circulated into the evaporator space 29 in which the cooled evaporator 25, i.e., the cooler 25, is housed. This causes heat exchange between the outer surface of the cooler 25 and the cold air circulation air 28, thus cooling it. The cold air circulation air 28 is produced by the cooling fan 27 and flows in a manner indicated by the arrows, with the help of the ductwork 41 and damper thermostat 42 configured on the backs of the freezer compartment 20 and the refrigerator compartment 21, etc., to cool the freezer compartment 20 and the refrigerator compartment 21 uniformly to an appropriate temperature.

[0081] In particular, the circulating cold air 28 that cools the refrigerator compartment 21 flows through the refrigerator compartment 21 and indirectly cools the inside of the drying compartment 11 by coming into contact with the surrounding cold air shielding walls 30, including the upper ceiling shielding wall 12 and the opening / closing mechanism shielding wall 17 of the drying compartment 11 located inside the refrigerator compartment 21. The circulating cold air 28 also comes into contact with the surface of the moisture-permeable membrane multilayer body 15, which is integrally molded as a partition surface for the humidity control window 16 provided in the upper ceiling shielding wall 12.

[0082] The circulating cold air 28 that has flowed inside the refrigerator compartment 21 and around the drying compartment 11 flows again through the evaporator space 29 from the intake port 43, undergoes heat exchange on the surface of the cooler 25, and is circulated by the cooling fan 27 through the ductwork 41 and damper thermo 42, returning to the refrigerator compartment 21.

[0083] On the surface of the cooler 25, not only is heat exchanged, but moisture absorbed as it flows through the refrigerator compartment 21 is also removed. In other words, the surface temperature of the cooler 25 is approximately -25°C, since the evaporation temperature of the refrigerant is set to -25°C to -30°C. Calculating from the absolute humidity (4.91E-04 (kg-water vapor / kg-dry air)) with a dew point of -25°C, the relative humidity at 5°C is less than 10%, so any excess moisture exceeding 10% will condense on the surface of the cooler 25. Therefore, if this cooling by the circulating cold air 28 is performed continuously, the relative humidity inside the refrigerator compartment 21 will theoretically be less than 10%.

[0084] Next, the inside of the drying chamber 11 can be heated by a heating means 32, such as an electric heater, installed on the lower bottom surface 31 of the sealed space 35. Normally, the upper limit of the surface temperature of the electric heater is set to 40°C, and a thermal fuse 34 is installed for safety. The temperature of the sealed space 35 of the drying chamber 11 is controlled by a temperature detection and control means 33, which turns the electric heater, which is the heating means 32, on and off around the set temperature.

[0085] If we estimate the relative humidity inside the drying chamber 11 when the temperature inside the drying chamber 11 is set to 30°C, the moisture-permeable membrane 13 will function smoothly, and since the refrigerator chamber 21 is at 5°C with a relative humidity of 10%, the sealed space 35 of the drying chamber 11 can be dehumidified to the same equilibrium absolute humidity. In other words, when the drying chamber is at 30°C, the relative humidity is calculated to be at equilibrium at 2% or less, and the drying process of the food to be dried 19 will proceed smoothly.

[0086] Next, we will explain how to store the food items to be dried 19 in the refrigerator-freezer 10 with a drying function, the drying process, and its mechanism of action.

[0087] First, confirm that the refrigerator-freezer 10 with drying function is running continuously and that the refrigerator compartment 21 is being cooled stably, then open the front refrigerator compartment insulated door 36. Next, pull the handle of the opening / closing mechanism shielding wall 17 at the front of the drying chamber 11 to open the sealed space 35, pull out the storage shelf 18 which can be easily moved in and out, and arrange the prepared food items to be dried 19 in the multiple storage shelves 18 of the storage shelf 18 with appropriate spacing between them. To complete the drying process quickly, it is best to slice the food items to be dried 19 as thinly as possible, but the thickness should be such that the texture of the food is not compromised.

[0088] The storage shelf 18 on which the food items to be dried 19 are placed is returned to its designated position in the center of the heating means 32, which is the electric heater, etc., on the lower bottom surface 31 of the sealed space 35 of the drying chamber 11, and the opening / closing mechanism shielding wall 17 is closed to seal the sealed space 35 of the drying chamber 11.

[0089] After that, the refrigerator door 36 of the refrigerator compartment 21 of the refrigerator-freezer 10 is closed, and the drying process switch (not shown) on the control device 37 attached to the front of the refrigerator door 36 is pressed to start the drying process.

[0090] When the drying process is started, heating begins first using a heating means 32 such as an electric heater. The electric heater has a heating means 32 that controls the current by increasing the resistance value when it reaches a certain temperature, like a PTC heater, but it is safer to set it up so that the heating means 32 is cut off by a thermal fuse 34 when it reaches about 40°C or higher.

[0091] When the control device 37 is set to perform drying at 30°C, the temperature detection and control means 33 located above the sealed space 35 of the drying chamber 11 detects 30°C and controls the temperature of the sealed space 35 of the drying chamber 11 to 30°C by turning the heating means 32 on and off.

[0092] When the storage shelf 18 is placed in the drying chamber 11, the environment inside the drying chamber 11 will incorporate the standard environment of the outside air, which is approximately 25°C with a humidity of about 60%. This will temporarily cause condensation on the inner wall surface of the cooled drying chamber 11. However, once it stabilizes, both the inner wall surface of the drying chamber 11 and the food to be dried 19 will begin to cool down to about 5°C.

[0093] Regarding the humidity in the sealed space 35 of the drying chamber 11, even at a temperature of 5°C, moisture adhering to the food to be dried 19, and, if fruits and vegetables are used as the food to be dried 19, free water in the food to be dried 19 evaporates due to respiration, etc., causing the humidity to rise to the level of the water activity Aw value specific to the food to be dried 19. When the partial pressure of water vapor in the drying chamber 11 rises and becomes higher than the partial pressure of water vapor in the refrigerator chamber 21, moisture from the drying chamber 11 permeates through the moisture-permeable membrane 13 attached to the humidity-regulating window 16, which is provided as a partition surface in the upper ceiling shielding wall 12, causing the humidity in the sealed space 35 inside the drying chamber 11 to decrease.

[0094] This moisture-permeable membrane 13 material is a urethane resin material with a hydrophilic glass transition temperature Tg in the refrigeration temperature range of 0°C to 10°C. As long as the temperature of the sealed space 35 of the drying chamber 11 is low, the partition surface of the humidity control window 16 is at the same temperature. Therefore, the moisture-permeable membrane 13 is also below its glass transition temperature Tg, resulting in low moisture permeability and suppressed drying. As a result, the relative humidity, which is the water activity Aw value of the food to be dried 19, stabilizes at around 90%.

[0095] When used as a vegetable compartment to store fresh vegetables, the respiration of the vegetables raises the temperature and humidity, and the moisture-permeable membrane 13 performs its moisture-permeable function to regulate humidity, creating a high-humidity environment with a suitable temperature and no condensation, making it a room where fresh vegetables can be stored for a long time.

[0096] Therefore, in order to make the drying chamber 11 function, it is necessary to press the switch in the control device 37 to start the drying process. As the temperature inside the drying chamber 11 rises, the food to be dried 19 is also heated, and the moisture adhering to the food 19 and the free water in the food evaporates. When the drying chamber 11 is at a low temperature, the moisture-permeable membrane 13 is in a glassy state and the amount of water vapor that passes through is low, so for a while, the humidity will rise along with the temperature inside the drying chamber 11.

[0097] However, the cold air shielding wall 30 of the drying chamber 11 is made of a ceramic or plastic material with relatively poor thermal conductivity and a thickness of about 3 mm, providing good insulation. Its inner surface is less affected by the refrigerator 21 and warms up as the temperature of the drying chamber 11 rises. In contrast, the interface between the inner and outer surfaces of the partition of the humidity control window 16 is a moisture-permeable membrane multilayer 15 made of a base fabric 14 laminated with a moisture-permeable membrane 13, with a thickness of less than 1 mm. It has worse insulation properties than other inner wall surfaces and is affected by the refrigerator 21, preferentially causing the inner temperature of the drying chamber 11 to drop and condensation to begin.

[0098] The moisture-permeable membrane 13 of the present invention uses a hydrophilic urethane-based polymer membrane (resin film). When this moisture-permeable membrane 13 becomes wet due to condensation, it has the property of increasing its moisture permeability several times, as shown in the comparison table in Figure 8. In other words, in the initial state, the inside of the drying chamber 11 is cooled to a refrigeration temperature range, so there is no condensation and the moisture permeability is low. However, as soon as condensation begins on the moisture-permeable membrane 13 on the partition surface of the humidity control window 16, the moisture permeability increases, and the condensed moisture moves to the refrigeration chamber 21 side and evaporates.

[0099] Therefore, although moisture condenses on the permeable membrane 13 which forms the partition surface of the humidity control window 16, the permeable membrane 13 itself has properties that cause the amount of moisture to permeate to jump up to about five times, so moisture permeation proceeds smoothly, and water droplets do not drip into the interior of the chamber, and moisture permeation progresses.

[0100] Furthermore, as the temperature inside the drying chamber 11 rises due to the heating means 32 on the lower bottom surface 31, and condensation occurs on the moisture-permeable membrane 13, the moisture-permeable membrane 13 absorbs condensation heat on the side of the sealed space 35 of the drying chamber 11, and absorbs evaporation heat on the base fabric 14 side of the moisture-permeable membrane 13 in the refrigerated chamber 21, thereby maintaining a relatively stable temperature of around 5°C. As a result, moisture from the heated food to be dried 19 evaporates and dehydrates, and the drying process continues.

[0101] However, as the drying of the food 19 progresses and the amount of water evaporating from the food 19 decreases, the partial pressure of water vapor in the drying chamber 11 decreases, reducing condensation on the moisture-permeable membrane 13, and eventually eliminating it. Once condensation is gone, the temperature of the moisture-permeable membrane 13 will rise due to the influence of the temperature inside the drying chamber 11.

[0102] This moisture-permeable membrane 13 material has a glass transition temperature (Tg) in the hydrophilic refrigeration temperature range of 0°C to 10°C, and moisture permeability is suppressed at low temperatures. However, when the temperature of the moisture-permeable membrane 13 rises above 20°C, the molecular structure loosens in the rubbery temperature region above the glass transition temperature (Tg), and moisture permeability increases. As shown in the curve in Figure 7(i), the moisture permeability increases by more than three times at 10°C and 30°C, and moisture permeability is maintained even when the temperature of the moisture-permeable membrane 13 is above the refrigerator temperature, allowing for smooth drying.

[0103] Next, when the refrigerator chamber 21 is stably cooled at the refrigeration temperature range, the function of the moisture-permeable membrane 13 during the process in which the temperature of the sealed space 35 of the drying chamber 11 rises due to the heating means 32 will be explained in detail with reference to Figures 9 (1), (2), and (3).

[0104] First, the state shown in Figure 9(1) is where the food items to be dried 19 are placed on the storage shelf 18 and stored, and then the temperature inside the drying chamber 11 stabilizes at 5°C. That is, the cold air circulation air 28 flowing through the refrigerator chamber 21 is heat-exchanged by the cooler 25 with a surface temperature of -25°C, and moisture is removed at the same time, and the temperature is regulated by the amount of air blown by the damper thermo 42.

[0105] Therefore, the calculation for the cold air circulation wind conditions 28 results in a temperature of 5°C and a relative humidity of 9.2%. At this time, the environment in the sealed space 35 of the drying chamber 11 is estimated to be 5°C, and the humidity is estimated to be around 90% due to the influence of evaporated moisture from the food being dried 19. That is, the partial pressure of water vapor at 5°C and 9.2% humidity is 0.8 hPa, and the partial pressure of water vapor at 5°C and 90% humidity is 7.9 hPa, so the partial pressure difference of water vapor is approximately 7.1 hPa, and this partial pressure difference of water vapor acts as the driving force for drying. However, this moisture-permeable membrane 13 material is a hydrophilic material with a glass transition point Tg in the refrigeration temperature range, and the amount of moisture permeation on the surface of the moisture-permeable membrane 13 is suppressed at low temperatures.

[0106] The relationship between temperature, humidity, and water vapor partial pressure is based on values ​​calculated using Tetens' equation.

[0107] Next, Figure 9(2) shows the process in which the sealed space 35 of the drying chamber 11 is heated and rises from 5°C to 30°C. At this stage, if the temperature of the moisture-permeable membrane 13 surface is maintained at 5°C, the absolute humidity at which condensation occurs is 5.4E-03 (kg-water vapor / kg-dry air), which translates to a relative humidity of 21% at 30°C. In other words, as long as the relative humidity inside the drying chamber 11 is maintained at 21% or higher, condensation water will form on the moisture-permeable membrane 13 surface, and a large amount of moisture permeability will be maintained.

[0108] Normally, the condensation rate is fast, and assuming that the diffusion rate of humidity from the food surface 19 to the moisture-permeable membrane 13 is also relatively fast, the drying rate of moisture escaping from the food surface 19 becomes the rate-limiting factor. The difference in water vapor partial pressure greatly influences this rate. At a temperature of 30°C and 100% relative humidity, the water vapor partial pressure on the food surface 19 is 42.4 hPa, while at a temperature of 5°C and 100% relative humidity, the water vapor partial pressure on the moisture-permeable membrane 13 is 8.7 hPa, resulting in a significant driving force of 33.7 hPa. Therefore, it can be said that the drying rate is equivalent to natural drying at 30°C and 21% humidity.

[0109] It should be added that the amount of water transmitted during condensation is more accurately determined by the penetration force into the moisture-permeable membrane, and hydrophilic urethane resin films have high compatibility with water and penetrate relatively quickly. Figure 8 shows a comparison table of the moisture permeability of hydrophilic urethane resin films measured using JIS-L1099 methods A-1 and B-1. The reason why the result measured using method B-1 was larger can be attributed to the influence of penetration force.

[0110] Next, the moisture that has permeated the moisture-permeable membrane 13 is transferred to the base fabric 14, which is formed as a moisture-permeable membrane multilayer 15. This base fabric 14 is made of a breathable woven or nonwoven fabric composed of breathable nylon or polyester fiber material, bonded to the moisture-permeable membrane via adhesive layers scattered at appropriate intervals. The adhesive layers are scattered at intervals and do not have a significant effect on the amount of moisture permeability, breathability, or permeability, and can be ignored here.

[0111] When condensation water is present in the permeable membrane multilayer body 15, which consists of a permeable membrane 13 and a base fabric 14, the permeable membrane 13 has a large dry surface area. The difference in water vapor pressure between the environmental conditions on the surface of the permeable membrane multilayer body 15 (temperature 5°C, relative humidity 100%, 8.7 hPa) and the conditions of the cold air circulation wind 28 (temperature 5°C, relative humidity 9.2%, water vapor partial pressure 0.8 hPa) results in a water vapor partial pressure difference of 7.9 hPa, which acts as a driving force for drying.

[0112] Next, Figure 9(3) shows a state where heating in the drying chamber 11 has progressed, the temperature has risen to 30°C, the amount of moisture evaporation from the food to be dried 19 has decreased drastically, the relative humidity in the drying chamber 11 has fallen to 21% or less, and condensation on the moisture-permeable membrane 13 has disappeared.

[0113] In this state, both the moisture-permeable membrane 13 and the base fabric 14 are dry, and no improvement in moisture permeability due to water penetration can be expected. However, since the temperature of the moisture-permeable membrane 13 is 30°C, which is above the glass transition temperature Tg, if the material shown in Figure 7(i) is used as the moisture-permeable membrane 13, the moisture permeability will remain high, and the drying process will proceed in an ideal environment where the food to be dried 19 is dried to 2% at 30°C.

[0114] Furthermore, the factor that stabilizes the temperature of the moisture-permeable membrane 13 is the change in the thermal insulation properties of the base fabric 14 attached to the moisture-permeable membrane 13, which forms the moisture-permeable membrane multilayer 15. The base fabric 14 is a woven or nonwoven fabric of nylon or polyester fibers, and the air layers contained within the fibers provide a certain degree of thermal insulation. However, when water is present due to condensation, it absorbs water through capillary action, which improves heat conduction and reduces thermal insulation properties.

[0115] In other words, by placing the urethane resin film of the moisture-permeable membrane 13 on the inner surface of the sealed space 35 of the drying chamber 11 and bonding the base fabric 14 to the side of the refrigerator 21, when condensation occurs, the insulation is poor due to the condensed water, further condensation occurs, and evaporation also progresses. However, when dry, the insulation of the base fabric 14 increases, and the moisture-permeable membrane 13 maintains its moisture permeability due to the temperature of the sealed space 35, and also works to suppress heat exchange between the drying chamber 11 and the refrigerator 13, resulting in an energy-saving drying process.

[0116] Furthermore, the drying method using the moisture-permeable membrane 13 of the present invention does not involve forcibly blowing dried air onto the food to be dried 19, but rather drying is achieved through the difference in water vapor partial pressure. As a result, the cells of the food to be dried 19 are dried while surrounded by a film of water molecules. In particular, the drying conditions are maintained at a water vapor partial pressure difference of approximately 8 hPa from the beginning to the end of drying. This driving force is effective for drying, and the drying force is further increased by the combined effect of rising air currents due to the temperature difference.

[0117] This invention utilizes the difference in water vapor pressure within a refrigerator, resulting in minimal color change and suppressed oxidative degradation of the surface of the food being dried 19. Furthermore, since it does not freeze, it provides a highly advantageous drying process with minimal destruction of cell tissue and nutrients.

[0118] Next, the drying process ends when the heating means 32, which is an electric heater, is stopped by timer control. The sealed space 35 of the drying chamber 11 is gradually cooled by the cold air circulation 28 circulating in the refrigerator chamber 21, and reaches the refrigerator temperature range, so the food to be dried 19 can be left as is, but it is recommended to remove the food to be dried 19 when the drying is finished, place it in an airtight container, and store it in the refrigerator or freezer.

[0119] Dried food ingredients, having lost their moisture after the drying process, retain a suitable texture with minimal cell damage even after freezing. By carefully controlling the degree of drying and the freezing temperature, it is believed that this drying method can also be used to preserve pectin and maintain the crispness of fresh vegetables for extended periods.

[0120] Furthermore, significantly increasing the amount of moisture permeability due to condensation on the moisture-permeable membrane 13 at the start of the drying process allows moisture and free water adhering to fresh ingredients to evaporate quickly, enabling each ingredient to be dried 19 to reach its water activity Aw value quickly. This has the effect of maintaining initial quality and suppressing the growth of bacteria.

[0121] Furthermore, according to the first embodiment of the present invention, the refrigerator-freezer 10 with a drying function, when not used as the drying chamber 11, is naturally cooled indirectly through the opening / closing mechanism shielding wall 17 and the cold air shielding wall 30, etc., maintaining a temperature and humidity range suitable for the vegetable compartment. However, since the structure as the drying chamber 11 would reduce the cooling efficiency for refrigeration, it is also possible to provide a ventilation opening that directly takes in cold air to the drying chamber 13 manually or automatically, and make it part of the refrigerator compartment 21.

[0122] Next, the drying chamber 51 installed in the refrigerator-freezer 50 with drying function of the second embodiment of the present invention will be described sequentially with reference to Figures 10 to 13. Note that the same parts as those in the refrigerator-freezer 10 with drying function of the first embodiment will be omitted or described in a simplified manner.

[0123] Figure 10 is a cross-sectional view showing the state in which the drying chamber 51 is installed in the refrigerator-freezer 50 with a drying function according to the second embodiment of the present invention. Figure 11 is a plan view (1) and a cross-sectional view (2) of the drying chamber 51 according to the second embodiment. Figure 12 is a cross-sectional view showing the state in which the food to be dried 67 is stored in the sealed space 66 of the drying chamber 51 according to the second embodiment and assembled as the drying chamber 51. Figure 13 is a cross-sectional view of the refrigerator-freezer 50 when the drying chamber 51 according to the second embodiment has been removed.

[0124] The refrigerator-freezer 50 with drying function according to the second embodiment consists of a freezer compartment 52, a refrigerator compartment 53, and a drying compartment 51. The refrigeration system 54 through which the refrigerant circulates is the same as in the first embodiment, and the freezer compartment 52, refrigerator compartment 53, and drying compartment 51 are cooled by the cold air circulation wind 57 generated by the cooling fan 56.

[0125] Similarly, the cooler (evaporator) 55 also maintains an external surface temperature in the range of -25°C to -30°C. The operation of the cooling fan 56 creates a cold air circulation 57, indicated by the arrow, that flows inside the refrigerator 50. This air circulation 57 flows through the evaporator space 58 where the cooler 55 is installed, resulting in heat exchange between the cold air circulation 57 and the surface of the cooler 55. Furthermore, the cold air circulation 57 circulates inside the refrigerator 50 through airflow control using ductwork 59 and a refrigerator damper thermostat 60, cooling the refrigerator compartment 53 to approximately 5°C (refrigeration temperature) and the freezer compartment 52 to approximately -25°C (freezing temperature).

[0126] The cold air circulating air 57 in the refrigerator compartment 53 flows over the cold air shielding wall 87 of the drying compartment 51 installed inside the refrigerator compartment 53. As the cold air circulating air 57 comes into contact with the cold air shielding wall 87 of the drying compartment 51, the sealed space 66 of the drying compartment 51 is also cooled indirectly by wall cooling.

[0127] Furthermore, the drying chamber 51 is composed of a bottom container shielding wall 61 and an opening / closing mechanism shielding wall 62. A sealed space 66 is formed by joining the lower flange 63 of the bottom container shielding wall 61 and the upper flange 64 of the opening / closing mechanism shielding wall 62 with a latch mechanism 65. In this sealed space 66, two tiers of breathable mesh storage shelves, a lower storage shelf 68 and an upper storage shelf 69, are set, on which the food items to be dried 67 can be placed.

[0128] A bottom plate 70 made of a thermally conductive aluminum plate or the like is integrally formed with the bottom container shielding wall 61 on the lower surface of the bottom container shielding wall 61, and there are multiple humidity control windows 71 in the upper top shielding wall 88 of the opening and closing mechanism shielding wall 62, and a moisture-permeable membrane multilayer body 72 is attached to the partition surface of the humidity control windows 71, forming the interface between the inside and outside of the drying chamber 51.

[0129] The moisture-permeable membrane multilayer body 72 is formed by bonding a moisture-permeable membrane 73, which is made of a hydrophilic urethane resin film, to a base fabric 74 made of a breathable nylon or polyester fiber material, or a nonwoven fabric, via adhesive layers scattered at appropriate intervals. The moisture-permeable membrane multilayer body 72 is attached to the partition surface of the humidity control window 71 with the base fabric 74 on the outside facing the refrigerator compartment and the moisture-permeable membrane 73 on the inside facing the sealed space 66 of the drying chamber 51.

[0130] The bottom container shielding wall 61 and the opening / closing mechanism shielding wall 62 that form the sealed space 66 of the drying chamber 51 are made of hard plastic or ceramic material, and their thickness is increased to further enhance insulation, and foamed plastic material is sometimes used. The moisture-permeable membrane multilayer 72 that partitions the humidity control window 71 is made of a base fabric 74 laminated with a moisture-permeable membrane 73 and is thin, less than 1 mm thick. It has worse insulation than the other walls and is affected by the temperature of the refrigerator chamber 53, so the side of the moisture-permeable membrane multilayer 72 facing the sealed space 66 is preferentially cooled.

[0131] The aluminum bottom plate 70 on the lower surface of the bottom container shielding wall 61 of the drying chamber 51 has a flat recess 75 on its outer surface. By fitting and attaching this recess to the convex surface 86 of the heating means 76 which is attached to the insulating partition 85 located at the bottom of the refrigerator compartment 53 of the freezer 50, the center of the bottom plate 70 of the drying chamber 51 is set to the center of the heating means 76.

[0132] As the heating means 76, a PTC heater 78 that maintains a constant temperature of approximately 40°C is incorporated together with a central temperature detection and control means 79 to form a convex surface 86 on the surface of a ceramic plate 77 which is rich in heat resistance and heat insulation. By fitting together the convex surface 86 of the PTC heater 78 with the flat recess 75 on the outer surface of the aluminum base plate 70, the temperature of the sealed space 66 can be detected by the temperature detection and control means 79, and the temperature of the sealed space 66 can be controlled by turning the heating means 76 on and off.

[0133] Furthermore, the refrigerator-freezer 50 with drying function consists of an insulated box 80, a freezer door 81, and a refrigerator door 82, which together form a freezer compartment 52 and a refrigerator compartment 53. The control device 83 for controlling the temperature of the sealed space 66 is mounted on the front of the refrigerator door 82.

[0134] Furthermore, the cold air circulating to the refrigerator compartment 53, 57, is supplied by a cooling fan 56 through a ductwork 59 at the back of the refrigerator compartment 53, via the cold air in the evaporator space 58, and is sent out from the exhaust port of the damper thermo 60. This air then circulates in the refrigerator compartment 53 and returns to the evaporator space 58 from the intake port 84.

[0135] The moisture-permeable membrane multilayer body 72 attached to the humidity control window 71 of the upper ceiling shielding wall 88 of the opening / closing mechanism shielding wall 62 of the drying chamber 51 is exactly the same as the moisture-permeable membrane multilayer body 15 in the first embodiment, and its form, structure, performance as a moisture-permeable membrane, and characteristics will not be described here.

[0136] Next, we will explain how to store the food items to be dried 67 in the refrigerator-freezer 50 with a drying function, the drying process, and its mechanism of action.

[0137] First, confirm that the refrigerator-freezer 50 with drying function is running continuously and that the refrigerator compartment 53 is being cooled stably, then open the front refrigerator compartment insulated door 81. Next, remove the drying container which will become the drying compartment 51, remove the latch mechanism 65, and separate the opening / closing mechanism shielding wall 62 and the bottom container shielding wall 61.

[0138] Next, the prepared food items to be dried 67 are placed on the upper storage shelf 68 and the lower storage shelf 69 at appropriate intervals. To complete the drying process quickly, the food items to be dried 67 should be sliced ​​as thinly as possible, but preferably to a thickness that does not impair the chewiness of the food.

[0139] After placing the food items to be dried 67 on the upper storage shelf 68 and the lower storage shelf 69, the storage shelves are returned to the bottom container shielding wall 61, closed from above with the opening / closing mechanism shielding wall 62, and the latch mechanism 65 is closed to form a sealed space 66, creating a drying container that becomes the drying chamber 51. The flat recess 75 at the bottom of the drying container that becomes the drying chamber 51 is fitted into the convex surface 86 formed by the heating means 76 of the PTC heater 78 and the temperature sensing and control means 79, thereby setting the center of the drying chamber 51 to the center of the heating means 76. This operation causes the aluminum bottom plate 70 at the bottom of the bottom container shielding wall 61 to be in close contact with the heating means 76.

[0140] After that, the refrigerator door 82 of the refrigerator compartment 53 of the refrigerator-freezer 50 is closed, and the drying process switch (not shown) on the control device 83 attached to the front of the refrigerator door 82 is pressed to start the drying process.

[0141] When the drying process is started, heating begins first by the heating means 76 of the PTC heater 78 located in the flat recess 75 on the back surface of the bottom container shielding wall 61 of the drying container in the drying chamber 51. When heating by the heating means 76 begins, the convex surface 86 of the PTC heater 78 is in close contact with the flat recess 75, and the bottom plate 70 forming the flat recess 75 is an aluminum plate with good thermal conductivity, so the heating of the bottom plate 70 heats the sealed space 66.

[0142] This PTC heater 78 controls the current by increasing its resistance when the temperature reaches 40°C. When drying the sealed space 66 of the drying chamber 51 at 30°C, the temperature detection and control means 79 located in the center of the PTC heater 78 detects 30°C, and the heating means 76 is turned on and off to control the temperature of the sealed space 66 of the drying chamber 51 to 30°C.

[0143] When the drying container in the drying chamber 51 is closed by the opening / closing mechanism shielding wall 62, the environment in the sealed space 66 incorporates a standard environment with a typical outside temperature and humidity of about 25°C and about 60% humidity. In the cooled sealed space 66 of the drying chamber 51, condensation may form on the inner wall surface. However, once stabilized, both the inner wall surface of the sealed space 66 of the drying chamber 51 and the food being dried 67 are cooled and settle at about 5°C.

[0144] Regarding the humidity in the sealed space 66 of the drying chamber 51, even at a temperature of 5°C, the humidity rises to the level of the water activity Aw value specific to the food being dried 67 because moisture adhering to the food being dried 67 and free water within the food being dried 67 evaporate.

[0145] When the partial pressure of water vapor in the sealed space 66 of the drying chamber 51 rises and becomes higher than the partial pressure of water vapor in the refrigerator chamber 53, the moisture-permeable membrane 73 of the humidity control window 71 installed in the upper ceiling shielding wall 88 of the opening / closing mechanism shielding wall 62 causes the water vapor moisture in the sealed space 66 of the drying chamber 51 to permeate into the refrigerator chamber 52, and the humidity inside the sealed space 66 of the drying chamber 51 decreases.

[0146] The material of this moisture-permeable membrane 73 is a hydrophilic urethane resin with a glass transition temperature (Tg) in the refrigeration temperature range of 0°C to 10°C. As long as the temperature of the sealed space 66 in the drying chamber 51 is as low as 5°C, the temperature on the surface of the humidity control window 71 is the same. Therefore, the moisture-permeable membrane 73 is also below its glass transition temperature (Tg), resulting in low moisture permeability and suppressed drying. As a result, it stabilizes at a relative humidity of about 90%, which is the water activity (Aw) value of the food to be dried 67.

[0147] When used as a vegetable compartment to store fresh vegetables, the respiration of the vegetables raises the temperature and humidity, and the moisture-permeable membrane 73 performs its moisture-permeable function to regulate humidity. This creates a suitable temperature and high humidity environment for vegetables, free from condensation, allowing fresh vegetables to be stored in the room for extended periods.

[0148] When the drying process is started, the food to be dried 67 is heated along with the rising temperature of the sealed space 66 in the drying chamber 51, causing moisture adhering to the food and free water in the food to evaporate. When the sealed space 66 in the drying chamber 51 is at a low temperature, the moisture-permeable membrane 73 is in a glassy state and allows little water vapor to pass through, so for a while, the humidity will rise along with the rising temperature of the sealed space 66 in the drying chamber 51.

[0149] However, the cold air shielding walls 87 of the bottom container shielding wall 61 and the opening / closing mechanism shielding wall 62, which form the sealed space 66 that becomes the drying chamber 51, are made of ceramic or plastic material with a thickness of about 3 mm and have relatively poor thermal conductivity, providing insulation, and the inner surface is less affected by the temperature of the refrigerator 53, so the inner wall surface is also heated as the temperature of the sealed space 66 that becomes the drying chamber 51 rises.

[0150] In this respect, the moisture-permeable membrane multilayer 72 installed at the boundary between the inside and outside of the moisture-regulating window 71 surface of the upper top surface shielding wall 88 of the opening and closing mechanism shielding wall 62 has a thin thickness of less than 1 mm, has worse thermal insulation than the other cold air shielding walls 87, is affected by the temperature of the refrigerator compartment 53, and is colder, so condensation preferentially begins there.

[0151] The moisture-permeable membrane 73 of the present invention is the same as in the first embodiment, and although this explanation will be redundant, when wetting occurs due to condensation, it has the property of increasing its moisture permeability several times over, as shown in the comparison table in Figure 8. That is, in the initial state, the sealed space 66 which becomes the drying chamber 51 is cooled to the refrigeration temperature range, so there is no condensation and the moisture permeability is low. However, as soon as condensation begins on the moisture-permeable membrane 73 of the humidity control window 71, the moisture permeability increases, and the condensed moisture is dispersed into the refrigerator chamber. Therefore, although moisture condenses on the moisture-permeable membrane 73, due to the properties of the moisture-permeable membrane 73 itself, the moisture permeability jumps up to about five times, so moisture permeability proceeds smoothly, and water droplets do not drip into the chamber, and moisture permeation progresses.

[0152] As the sealed space 66 of the drying chamber 51 is heated by the heating means 76 and the temperature rises, and condensation occurs on the moisture-permeable membrane 73, the inside of the moisture-permeable membrane 73 absorbs the heat of condensation and the outside of the moisture-permeable membrane 73 removes the heat of evaporation, allowing the evaporation drying of the food to be dried 67 to continue while maintaining a relatively stable temperature of around 5°C.

[0153] However, as the drying of the food material 67 progresses, the amount of water vapor evaporating from the food material 67 decreases, the water vapor partial pressure value in the sealed space 66 of the drying chamber 51 decreases, and when condensation on the moisture-permeable membrane 73 ceases, the temperature of the moisture-permeable membrane 73 will rise.

[0154] This moisture-permeable membrane 73 material has a glass transition temperature (Tg) in the hydrophilic refrigeration temperature range of 0°C to 10°C. Therefore, moisture permeability is suppressed at low temperatures, and when the temperature of the moisture-permeable membrane 73 rises above 20°C, the permeability of water vapor increases in the rubbery temperature region above the glass transition temperature (Tg). As shown in the curve in Figure 7(a), the moisture permeability increases by more than three times at 30°C compared to 10°C.

[0155] Furthermore, the function of the moisture-permeable membrane 73 when the temperature of the sealed space 66 of the drying chamber 51 rises due to the heating means 76, from a state in which the refrigeration chamber 53 is stably cooled at the refrigeration temperature range, is the same as in the first embodiment and has been explained in detail with reference to Figures 9(1),(2), and(3), so it will be omitted here.

[0156] Furthermore, the factor that stabilizes the temperature of the moisture-permeable membrane 73 is the change in the thermal insulation properties of the base fabric 74 to which the moisture-permeable membrane 73, which forms the moisture-permeable membrane multilayer 72, is attached. Its function and effect are the same as in the first embodiment, and therefore no further explanation is provided.

[0157] Therefore, the drying method using the moisture-permeable membrane 73 of the present invention does not involve forcibly blowing dried air onto the food to be dried 67, but rather drying is achieved by the difference in water vapor partial pressure. As a result, the cells of the food to be dried 67 are dried while surrounded by a film of water molecules. In particular, the drying conditions are maintained at a water vapor partial pressure difference of approximately 8 hPa from the beginning to the end of drying. This driving force is effective for drying, and the drying force is increased by the combination of this and the rising air current due to the temperature difference.

[0158] As described above, this invention does not dry the food to be dried 67 by blowing dry cold or hot air onto it, but rather dries it using the difference in water vapor pressure through a moisture-permeable membrane 73 that can control temperature and humidity. As a result, the surface of the food to be dried 67 shows less color change and oxidative degradation is suppressed, resulting in a groundbreaking drying function that minimizes damage to cell tissue and nutrients.

[0159] Next, the drying process is terminated when the heating means 76 is stopped by timer control. The sealed space 66 of the drying chamber 51 is gradually cooled by the cold air circulation 57 of the refrigerator chamber 53 and reaches the refrigerator temperature range. It is acceptable to leave it as is and store it in the refrigerator, but it is recommended to remove the dried food 67 at the end of the drying process, put it in another sealed container, and store it in the refrigerator or freezer.

[0160] After the drying process is complete and the food is dehydrated, the cell damage caused by freezing is reduced. By carefully controlling the degree of drying and the freezing temperature range, it is believed that this drying method can also be used to preserve pectin and maintain the texture of fresh vegetables for extended periods.

[0161] Furthermore, at the start of the drying process, condensation occurs on the moisture-permeable membrane 73, significantly increasing the amount of moisture that can permeate. This allows moisture and free water adhering to fresh food ingredients to evaporate quickly, enabling each food ingredient 67 to reach its water activity value sooner and thus suppressing the growth of bacteria.

[0162] Furthermore, according to the refrigerator-freezer 50 with drying function of this second embodiment, when the drying chamber 51 is not used as a sealed space 66, as shown in Figure 13, the drying chamber 51 can be removed and expanded to be used as a refrigerator chamber 53. Alternatively, the opening / closing mechanism shielding wall 62 can be turned over and placed on top of the bottom container shielding wall 61, allowing it to be used as a storage shelf without having to remove it. [Industrial applicability]

[0163] As explained above, the moisture-permeable membrane preferentially allows only moisture to pass through, preventing other gases and odor components from passing through. By increasing airtightness, it effectively shuts out odor components and prevents odor transfer to other foods or ice. Since household refrigerators and freezers often need to store various foods together, the effect of suppressing odor transfer is important.

[0164] However, this new drying method, which utilizes a moisture-permeable membrane to temporarily lower the dew point temperature of the food being dried to an intermediate level using the partial pressure of water vapor, can prevent discoloration of the food being dried and prevent oxidation of intracellular components and nutrients. Therefore, it is expected to be effective even in large commercial and industrial freezers and refrigerators, and can be used in those fields as well.

[0165] Furthermore, although a configuration in which the heating means is attached to the refrigerator / freezer side has been described and explained as an embodiment, it is also possible to draw power from an external source, assemble it as a standalone drying chamber with a moisture-permeable membrane specification and a heating means, and then store that drying chamber in the refrigerator of various refrigerator / freezer units for drying. It is also possible to develop a standalone drying chamber product that can be attached as an option to existing household refrigerator / freezer units. [Explanation of Symbols]

[0166] 10, 50... Refrigerator / freezer, 11, 51... Drying chamber, 12, 88... Upper ceiling shielding wall, 13, 73... Moisture-permeable membrane, 14, 74... Base fabric, 15, 72... Moisture-permeable membrane multilayer, 16, 71... Humidity control window, 17, 62... Opening / closing mechanism shielding wall, 18... Storage shelf, 19, 67... Food to be dried, 20, 52... Cold Freezing chamber, 21, 53... Refrigeration chamber, 22... Compressor, 23... Condenser, 24... Expansion valve, 25, 55... Evaporator (cooler), 26, 54... Refrigeration system, 27, 56... Cooling fan, 28, 57... Cold air circulation air, 29, 58... Evaporation space, 30, 87... Cold air shielding wall, 31... Lower bottom surface, 32, 76... Heating means, 33, 79... Temperature detection and control means, 34... Thermal fuse, 35, 66... ​​Sealed space, 36... Insulated door, 37, 83... Control device, 38, 80... Insulated box body, 39, 81... Freezer door, 40, 82... Refrigerator door, 41, 59... Ductwork, 42, 60... Damper thermostat, 43, 84... Air intake, 61... Bottom container shielding wall, 63... Below flange, 64... Above flange, 65... Latch mechanism, 68... Upper storage shelf, 69... Lower storage shelf, 70... Bottom base plate, 75... Flat recess, 77... Ceramic plate, 78... PTC heater, 85... Insulated partition, 86... Convex surface

Claims

1. A refrigerator with a drying function is provided in a refrigerator compartment which is cooled by a circulating cold air that has been heat-exchanged by a cooler in the freezing temperature range, and a drying processing chamber which is cooled by the circulating cold air through a cold air shielding wall, forming a sealed space surrounded by the cold air shielding wall, etc., and the sealed space has a breathable storage shelf such as a mesh on which food to be dried can be placed, a heating means such as an electric heater that heats the sealed space to a predetermined temperature from the bottom, and a temperature detection control means for the sealed space that controls the heating means, and a shielding wall with an opening and closing mechanism that allows the food to be dried or the storage shelf to be put in and taken out in part of the cold air shielding wall, and a humidity control window provided as a partition surface in the upper top shielding wall of the drying processing chamber, through which only water vapor and moisture can pass, a moisture-permeable membrane or a moisture-permeable membrane multilayer body.

2. The refrigerator-freezer with drying function according to claim 1, characterized in that the moisture-permeable membrane multilayer body is made by laminating a hydrophilic moisture-permeable resin film that forms the moisture-permeable membrane onto a breathable base fabric, or by coating it with a hydrophilic moisture-permeable resin.

3. The refrigerator with drying function according to claim 1, characterized in that the moisture-permeable membrane is a hydrophilic urethane-based resin film whose glass transition temperature Tg is set near the refrigeration temperature range of 0°C to 10°C, the base fabric is a breathable woven or nonwoven fabric such as nylon or polyester, and the moisture-permeable membrane multilayer body is formed by bonding the base fabric and the moisture-permeable membrane via adhesive layers scattered at appropriate intervals.

4. The refrigerator-freezer with drying function according to any one of claims 1 to 3, characterized in that the drying chamber is set to have the lowest thermal insulation performance compared to the thermal insulation performance of the cold air shielding wall forming the sealed space, and the thermal insulation performance of the moisture-permeable membrane or moisture-permeable membrane multilayer that forms the partition surface of the humidity-regulating window is set to the lowest.

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