JP4087176B2 - Transparent ice manufacturing apparatus and transparent ice manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transparent ice manufacturing apparatus and a transparent ice manufacturing method for manufacturing transparent ice in a household refrigerator.
[0002]
[Prior art]
Conventionally, ice making of transparent ice in household refrigerators is performed by shaking the ice tray after supplying water to the ice tray to prevent air bubbles generated by freezing from mixing into the ice, and before making ice The method of making ice using the water which deaerated dissolved gas was taken.
[0003]
Moreover, in the commercial ice store, the ice tray for freezing water was turned downward and water was supplied onto the fountain, and gradually frozen from the side of the ice tray. In addition, there was a method of growing single crystal ice following natural ice cubes.
[0004]
[Problems to be solved by the invention]
A major problem in making clear ice is how to prevent bubbles generated during freezing from being taken into the ice. Another object of the present invention is to prevent precipitation of the hardness ion component itself existing in the well water and mineral water having high hardness and bubbles generated by impurities such as the hardness ion component as a nucleus.
[0005]
General tap water contains about 15 to 30 ppm of hardness ion components and about 20 ppm of dissolved gas. When water crystallizes into ice, it becomes transparent ice or opaque ice depending on the balance between the speed at which water crystallizes and the speed at which impurities are discharged from the crystallized ice.
[0006]
In particular, the generation of opaque ice by dissolved air is greatly related to the diffusion of air in water, and the dissolved air is confined in the ice when the interface movement speed of ice and water is high. However, when the interface moving speed is slow, air molecules that cannot enter ice accumulate in the water in the vicinity of the interface, and a region having an excessive air molecule concentration is formed. Such excess air molecular weight gradually increases with the growth of ice, and when it exceeds a certain limit, it becomes a macroscopic air bubble and is confined in the ice which has finally progressed.
[0007]
The method of preventing the bubbles generated when water crystallizes by physically vibrating the ice tray is somewhat transparent, but if the generated bubbles are small, There was a problem that air bubbles were not separated from the interface between ice and water and were closed in the ice.
[0008]
In addition, the method of degassing and removing the gas component in advance before crystallization is effective for producing transparent ice, but it not only leads to a significant increase in cost due to the large scale of the apparatus, but also the time for ice making. When this occurs, air is dissolved again in the degassed water, and bubbles are generated during crystallization, resulting in a problem that ice with high transparency cannot be obtained.
[0009]
Furthermore, there is a method of making single crystal ice with high transparency by dropping water droplets on a flat part without a container, but it is necessary to make ice in the container in a domestic refrigerator or commercial freezer, There was a problem that was not possible.
[0010]
Thus, there is a problem that it is difficult to obtain ice with high transparency.
[0011]
In view of the above problems, an object of the present invention is to provide a transparent ice manufacturing apparatus and a transparent ice manufacturing method capable of obtaining ice with high transparency.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problem, the first aspect of the present invention includes a frozen space,
A container disposed in the frozen space, the bottom being kept at a lower temperature than the top; and
Water supply means for supplying water to the container,
Ice making at an ice making speed of 5 μm / s or less,
The water supply means, such that the portion in contact with the atmosphere of the liquid layer portion of the container is not binding frozen until the completion of ice making is intermittently feed water to permeable Akirakori manufacturing apparatus from the top of the container.
[0013]
Moreover, 2nd this invention is the transparent ice manufacturing apparatus of 1st this invention whose thickness of the liquid layer part of the said container is below the thickness in which a bubble is not formed substantially.
[0014]
The third aspect of the present invention is the transparent ice manufacturing apparatus according to the first or second aspect of the present invention, wherein the ice making speed is 2 μm / s or more.
[0016]
In addition, according to a fourth aspect of the present invention, the water supply means performs the next water supply before the surface of the currently supplied water freezes, and repeats the water supply until the ice to be made has a predetermined thickness,
The transparent ice manufacturing apparatus according to the first aspect of the present invention is such that when the water supply is stopped, a portion of the liquid layer portion in the container that is in contact with the atmosphere does not freeze until the liquid layer portion in the container is frozen.
[0017]
In addition, the fifth aspect of the present invention is the transparent ice manufacturing apparatus according to the first or fourth aspect of the present invention, wherein the interval at which the water supply means supplies water is such that the entire liquid layer in the container is not overcooled. .
[0018]
The sixth aspect of the present invention is the transparent ice manufacturing apparatus according to any one of the first to fifth aspects of the present invention, wherein the side surface temperature of the container is higher than the bottom surface temperature.
[0019]
The seventh aspect of the present invention is a transparent ice manufacturing apparatus comprising: a refrigerated space; a container disposed in the refrigerated space, the bottom portion being kept at a lower temperature than the top; and a water supply means for supplying water to the container. A method for producing transparent ice using transparent ice,
Ice making at an ice making speed of 5 μm / s or less,
It said that portion in contact with the atmosphere of the liquid layer portion of the container is not frozen until the completion of the ice, which is permeable Akirakori manufacturing process intermittently supply water from the top of the container by the water supply means.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The configuration of the embodiment of the present invention will be described below with reference to the drawings together with the operation thereof.
[0021]
In the conventional ice making of transparent ice, the point is how to make the hardness ion component or dissolved air contained in tap water or well water transparent without entering into the ice, but this embodiment is Dissolve air (existing at about 40 ppm at 0 ° C and 1 atm) is not desorbed into ice and does not generate bubble nuclei in the liquid layer. Without removing the impurities, it is confined in ice such as grain boundaries to produce transparent ice.
[0022]
First, a mechanism that can efficiently suppress the generation of bubbles when water is intermittently supplied by a water supply means (not shown) will be described.
[0023]
FIG. 1 shows a state in which a part of the water put in the ice making container 1 is frozen to become ice 3 and a part of the water 2 remains. Although not shown in FIG. 1, in order to keep the bottom of the ice making container 1 at a low temperature, a lot of cold air is applied or a cooling plate is arranged, and a heater or a heat insulating material is arranged to keep the upper part of the ice making container 1 at a high temperature. Then, the bottom temperature of the ice making container 1 is set to −10 ° C., for example, and the top temperature is set to 0 ° C. The water supply means intermittently supplies water from the upper part of the ice making container 1.
[0024]
If the ice-making speed is very high, bubbles are generated at the solid-liquid interface between ice and water, causing white turbidity. However, if the ice-making speed is 5 μm / s or less, the dissolved air is not taken into the ice 3 and is pushed out into the water. 4 does not become bubbles but dissolves in water 3 and is released into the atmosphere.
[0025]
As shown in FIG. 2, air molecules pushed out from ice do not immediately diffuse into the entire liquid layer, but an excessively existing area is formed on the water side of the solid-liquid interface. When the ice making speed is fast, the dissolved air molecules in the excess region exceed the limit concentration to form bubble nuclei, and the air molecules existing in the vicinity flow into bubbles at a stretch, but the freezing speed is 5 μm / s or less. Bubbles are not generated because the dissolved air concentration in the excess region is below the limit concentration.
[0026]
The reason why bubble nuclei are not generated will be described below. It is assumed that dissolved air molecules gather for some reason in the excess region to form a bubble nucleus having a small diameter b. At the moment when bubbles are formed, water forms an interface, the initial molecule releases internal energy and expands at once, and the internal pressure P of the bubbles decreases to a point where it balances with hydrostatic pressure + surface tension, so the following formula 1 is established. To do.
[0027]
[Expression 1]
P = Po + Λ
Where Po: hydrostatic pressure (atmospheric pressure + water weight ≈ 1 atm)
Λ = 4γ / b (γ: surface tension 71 dyn / cm)
Immediately after a bubble nucleus having a diameter b and a surface area s is formed, a small amount of molecule δn mol is additionally flown from the surroundings, the bubble pressure is maintained at P, and the number of molecules is increased by δn mol. Assuming that δb is increased by a small amount, the amount of change δG in the system energy can be obtained as follows.
[0028]
That is, the energy release amount of the inflowing molecules and the surface energy increase amount of the water are expressed by the following formula 2.
[0029]
[Expression 2]
Energy release amount of inflowing molecule = − (δn) RT {ln (Ψ / P)}
Increase in surface energy of water = (δs) γ
The equation of state inside the bubble is PV = nRT, the volume of the bubble is V = πb / 6, the surface area of the bubble is s = πb, and each variation is expressed by the following equation (3).
[0030]
[Equation 3]
δn = (δV) P / RT = (δb) πbP / 2RT
δs = 2πb (δb)
Therefore, the change amount δG of the energy of the system is expressed by the following formula 4.
[0031]
[Expression 4]
δG = − (δb) π (b / 2) PIn (Ψ / P) + 2πbγ (δb)
δG / δb = π (b / 2) [−PIn (Ψ / P) + 4γ / b]
In order for bubbles to grow, the energy decreases as the bubble diameter increases. That is, Formula 5 is established.
[0032]
[Equation 5]
δG / δb ≦ 0
Therefore, the following formula 6 is established.
[0033]
[Formula 6]
PIn (Ψ / P) ≧ 4γ / b = Λ
The minimum pressure Ψmin inside the bubble is as shown in Equation 7.
[0034]
[Expression 7]
Ψmin = Pexp {Λ / P}
FIG. 3 shows the relationship between the bubble diameter b and the pressure Ψmin in the bubble. FIG. 3 shows that in order to generate bubbles with a bubble diameter of about 1 μm for some reason (dissolved silica, hardness ion component, etc.), excess air molecules are required to make the pressure inside the bubble about 7.9 atm. It shows that.
[0035]
That is, an air molecule concentration of about 8 times the saturated air molecule concentration (about 1 atm) is required. However, once bubble nuclei are generated, air molecules flow into the bubble nuclei, reducing the pressure inside the bubbles at once, meaning that they are present as stable bubbles in the liquid layer.
[0036]
Therefore, in order to prevent white turbidity due to bubbles, the ice making speed is preferably as slow as possible. However, if it is too slow, there is a problem that ice making cannot be performed when desired in summer. As a result, it was found that if the ice making speed is 2 to 5 μm / s, clear ice having a volume of 10 ml can be made in 1 to 2 hours.
[0037]
That is, FIG. 6 shows the relationship between ice making speed and transparency. In FIG. 6, the ice making speed was obtained by measuring the thickness of ice made after a predetermined time elapsed from the start of ice making, and dividing the measured ice thickness by a predetermined time. Then, the transparency of the ice made is measured, and the relationship between the ice making speed and the transparency of the ice made is shown in a graph. From FIG. 6, it can be seen that when the ice making speed is 5 μm / s or less, the transparency of the ice made is 90% or more.
[0038]
In addition, the ice produced was visually observed to test how much transparency was obtained. As a result, the following was found. That is, when the ice having a transparency of 90% or more was visually observed, excellent transparency was obtained. On the other hand, it was found that when the transparency of the ice made was lowered from 90%, the visual transparency suddenly decreased.
[0039]
Therefore, it can be said that transparent ice can be made when the ice making speed is 5 μm / s or less.
[0040]
As shown in FIG. 1, the dissolved air pushed out from the ice 3 exists as excess air in the water 2, but if the amount of water supplied at one time is, for example, about 0.2 to 1 ml, the thickness of the water 2 is It is very thin, about 0.1 to 0.5 mm, and excess air is further released from the water 2 to the atmosphere, resulting in the excess air concentration (about 8 times the saturated air concentration) required for generating bubbles. Does not reach.
[0041]
That is, when the thickness of the water 2 is thick, it takes time for the air to move in the water 2, so that the air concentration of the water 2 may increase considerably and bubbles may be generated. On the other hand, if the thickness of the water 2 is very thin, about 0.1 to 0.5 mm, the air is released into the atmosphere before it becomes bubbles.
[0042]
However, if the amount of water supplied at one time is so small, the whole supplied water is likely to be supercooled. Therefore, by performing the next water supply before the whole water 2 is supercooled, the solid-liquid interface While the water 2 in the vicinity is kept supercooled, the temperature of the upper part of the water 2 is increased by the supplied water, and the whole water 2 is prevented from being supercooled and becoming sherbet-like ice instantly. .
[0043]
Further, by intermittently supplying water, there is always a liquid layer surface in contact with the atmosphere above the liquid layer, so excess air molecules are released into the atmosphere through the liquid layer without forming bubble nuclei. The main cause of white turbidity due to air bubbles is that the upper part of the water in the ice making cell freezes and excess air molecules are not released into the atmosphere. However, according to this embodiment, a part of the upper part is always a liquid layer or water. Therefore, excess air molecules are not trapped in ice.
[0044]
Next, in addition to white turbidity due to bubbles, there is white turbidity due to precipitation of hardness ion components. A method for making transparent ice by preventing precipitation of impurities such as hardness ion components contained in tap water and well water will be described. . In general, tap water includes hydrogen ions (H ⁺ ) and hydroxide ions (OH ⁻ ) generated from water (H ₂ O), dissolved air (O ₂ , N ₂ , CO ₂ etc.) and CO ₂ Hydrogen carbonate ions (HCO ₃ ⁻ ) generated by dissolution of sodium chloride, sodium ions (Na ⁺ ), potassium ions (K ⁺ ), calcium ions (Ca ²⁺ ), magnesium ions (Mg ²⁺ ), chloride ions (Cl ⁻⁾ ), Nitrate ions (NO ₃ ⁻ ), sulfate ions (SO ₄ ²⁻ ), hypochlorite ions (OCl ⁻ ), and silicate ions (SiO ₄ ⁴⁻ ).
[0045]
Pure ice is a high-purity crystal consisting only of hydrogen bonds of H ₂ O and containing no impurities, but as mentioned above, there are many impurities in tap water, and cations and some anions are treated with special water treatment. Unless it is removed, the water is frozen and discharged into unfrozen water and concentrated. When it becomes a precipitate and aggregates, it becomes cloudy as a precipitate in ice.
[0046]
Therefore, if the amount of water supplied at one time is, for example, about 0.2 to 1 ml, and the ice making speed is in the range of 2 to 5 μm / s, the impurity ions are not pushed out into the unfrozen water, some are in the state of ions, It was found that some of the precipitates were trapped in ice but could be made into ice having a transparency of 90% or more. That is, even if impurities exist in ice, for example, if the size is 1 μm or less and the particles do not aggregate, the light transmittance is reduced, but the ice cannot be visually observed and becomes transparent ice.
[0047]
Further, as shown in FIG. 4, when the side surface temperature of the ice making container 1 is slightly higher than the bottom surface temperature, the impurities diffuse widely in the side direction of the ice making container. Therefore, even if tap water or well water contains impurities, transparent ice Can make ice.
[0048]
In the past ice making, the water in the ice making cell was frozen by cooling from 6 directions, so the impurities diffused toward the center of the ice and precipitated at the center of the ice, lowering the transparency. Most impurities diffuse in the direction of the surface of the ice, so even if they are deposited, they become inconspicuous and ice with high transparency can be obtained.
[0049]
FIG. 5 shows the relationship between the hardness of the water used and the transparency. According to the present invention, it can be seen that ice having a hardness of about 80 and a transparency of 90% can be obtained.
[0050]
As described above, according to the present embodiment, the following effects can be obtained.
[0051]
In other words, when making ice using a household refrigerator, it took 4 hours or more to make ice with a transparency of 90% or more. In the present invention, the time from water supply to deicing is 1 to 2 hours. It was possible to save a lot of time. In addition, transparency of 90% or more can be secured up to a hardness of about 80, so transparent ice can be easily made at home except in special areas.
[0052]
【The invention's effect】
As is apparent from the above description, the present invention can provide a transparent ice manufacturing apparatus and a transparent ice manufacturing method capable of obtaining ice with high transparency.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a state of ice making in an ice making container in an embodiment of the present invention. FIG. 2 is a graph showing a change in air molecule concentration in the embodiment of the present invention. The figure which shows the graph which shows the relationship between the bubble diameter and bubble internal pressure in embodiment of invention. FIG. 4 is sectional drawing which shows the spreading | diffusion of the impurity in embodiment of this invention. FIG. 5 Hardness in embodiment of this invention FIG. 6 is a graph showing the relationship between the transparency and the transparency. FIG. 6 is a diagram showing the relationship between the ice making speed and the transparency in the embodiment of the present invention.
1 Ice making container 2 Water 3 Ice 4 Extruded dissolved air 5 Dissolved air released into the atmosphere 41 Impurity diffusion direction

Claims (7)

Frozen space,
A container disposed in the frozen space, the bottom being kept at a lower temperature than the top; and
Water supply means for supplying water to the container,
Ice making at an ice making speed of 5 μm / s or less,
The water supply means, such that the portion in contact with the atmosphere of the liquid layer portion of the container is not binding frozen until the completion of ice making, intermittently feed water to permeable Akirakori manufacturing apparatus from the top of the container. The transparent ice manufacturing apparatus according to claim 1, wherein the liquid layer portion of the container has a thickness equal to or less than a thickness at which bubbles are not substantially formed.   The transparent ice manufacturing apparatus according to claim 1, wherein the ice making speed is 2 μm / s or more. The water supply means performs the next water supply before the surface of the currently supplied water freezes, and repeats the water supply until the ice to be made has a predetermined thickness,
The water supply and when stopped, until the liquid layer portion of the container is frozen transparent ice production apparatus according to claim 1, wherein the portion in contact with the atmosphere of the liquid layer portion of the container should not be frozen. The transparent ice manufacturing apparatus according to claim 1 or 4 , wherein an interval at which the water supply means supplies water is an interval such that the entire liquid layer portion in the container is not overcooled. Transparent ice manufacturing apparatus according to any of aspects temperature is higher claim than the bottom temperature 1-5 of the container. Transparent ice for producing transparent ice using a transparent ice production apparatus comprising a freezing space, a container disposed in the freezing space, the bottom of which is kept at a lower temperature than the top, and water supply means for supplying water to the container A manufacturing method,
Ice making at an ice making speed of 5 μm / s or less,
Said that portion in contact with the atmosphere of the liquid layer portion of the container is not frozen until the completion of the ice making, Toru Akirakori manufacturing method intermittently supply water from the top of the container by the water supply means.

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