Preparation method of high-transmittance ice block

Abstract

The application discloses a preparation method of high-transmittance ice blocks, and belongs to the technical field of industrial ice making. The application adopts the preparation method of high-transmittance ice blocks, realizes high optical quality of ice blocks with transmittance greater than or equal to 95% and internal bubble quantity less than or equal to 0.1 per cm 3 , eliminates structural problems such as cracks and layered defects, greatly reduces production energy consumption and site occupation, and is suitable for high-end ice sculpture, large ice building, commercial catering and other multi-scene requirements, and takes into account product performance, production efficiency and energy saving and environmental protection.

Description

Technical Field

[0001] This invention relates to the field of industrial ice-making technology, and in particular to a method for preparing ice blocks with high light transmittance. Background Technology

[0002] Ice, as an important medium for artistic expression and architectural construction, is widely used in high-end ice sculptures, ice hotels, and winter festival facilities. Its optical quality and structural integrity directly determine the application effect. High-transmittance ice is more favored than opaque ice because it can achieve complex light and shadow refraction, provides a glass-like smooth surface, and has a higher structural density and stronger mechanical strength.

[0003] The mainstream methods for producing high-transmittance ice in the current industrial sector are the bucket ice-making method and the bottom-up method, both of which reduce air bubble retention by simulating the movement of water during natural freezing. However, these two methods have significant drawbacks: First, in the traditional ice-making process, impurities and dissolved gases in the water are difficult to completely remove, easily forming defects such as cavitation and cracks in the ice, causing the ice to easily break and fail under intricate carving or load-bearing conditions; second, they consume enormous amounts of energy, requiring a huge investment to cool a large volume of water and maintain its continuous movement, with the refrigeration compressor running for extended periods further exacerbating the energy burden; third, the production cycle is extremely long, typically requiring three to five days to freeze a standard batch, limiting production capacity and occupying a large amount of space. In addition, ice produced by traditional methods also suffers from insufficient optical clarity and poor structural uniformity, failing to meet the intricate carving requirements of high-end ice sculptures, the load-bearing requirements of large ice buildings, and the aesthetic and quality demands of the commercial catering industry. Therefore, the industrial ice-making industry urgently needs a preparation method that can improve the transmittance of ice while reducing energy consumption and shortening production time. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing high-transmittance ice blocks to solve the problems existing in the traditional industrial ice-making process.

[0005] To achieve the above objectives, the present invention provides a method for preparing high-transmittance ice cubes, comprising the following steps: S1. Pretreatment: The raw water is subjected to reverse osmosis and vacuum degassing to obtain pretreated raw water. S2. Freezing: A low-temperature cooling ring is set around the bottom periphery of the freezing mold, an auxiliary heat source is set above the low-temperature cooling ring, and a refrigerant circulation channel is set inside the low-temperature cooling ring; an ultrasonic transducer is set on the top of the freezing mold, and the freezing mold is equipped with a proportional-integral-derivative (PID) closed-loop control system; the heat of the auxiliary heat source is provided by the waste heat of the refrigeration compressor; The pretreated raw water in S1 is injected into the freezing mold through a sealed pipeline. The low-temperature cooling ring is pre-cooled, and the auxiliary heat source and ultrasonic transducer are started. The low-temperature cooling ring and auxiliary heat source move upward from the bottom of the freezing mold to freeze. S3. Post-processing: After freezing, temper at a constant temperature, demold, and obtain ice blocks with high light transmittance.

[0006] Preferably, in S1, the raw water is selected from pure water or distilled water, the desalination rate of the reverse osmosis treatment is ≥98%, the conductivity of the raw water after reverse osmosis treatment is ≤5μS / cm, the total dissolved solids of the raw water after reverse osmosis treatment is ≤3mg / L, the pressure of vacuum degassing is 0.02~0.08atm, and the vacuum degassing time is 20~40min.

[0007] Preferably, in S2, the distance between the top of the freezing mold and the surface of the pretreated raw water is 5~10cm.

[0008] Preferably, in S2, the height of the freezing mold is 0.33~1.2m, the diameter or side length of the freezing mold is determined according to the ice block specifications, and the inner dimension of the low-temperature cooling ring matches the outer dimension of the freezing mold. This invention does not impose any limitations on this.

[0009] Preferably, in S2, the pre-cooling temperature of the low-temperature cooling ring is -35℃ to -25℃, the moving speed is 1 to 5 mm / h, and the axial temperature gradient is 0.1 to 0.6℃ / cm.

[0010] In an embodiment of the present invention, when the height of the freezing mold is 0.33~0.8m, the moving speed of the low-temperature cooling ring is 1~3mm / h, and the axial temperature gradient is 0.1~0.3℃ / cm; when the height of the freezing mold is 0.8~1.2m, the moving speed of the low-temperature cooling ring is 3~5mm / h, and the axial temperature gradient is 0.3~0.6℃ / cm.

[0011] Preferably, in S2, the distance between the low-temperature cooling ring and the auxiliary heat source is 3~8cm.

[0012] Preferably, in S2, the refrigerant flow rate is 2~3m / s, and the refrigerant can be an environmentally friendly refrigerant known to those skilled in the art.

[0013] Preferably, in S2, the frequency of the ultrasonic transducer is 20~40kHz, and the power of the ultrasonic transducer is 50~150W.

[0014] Preferably, in S3, the isothermal tempering temperature is -8℃ to -2℃, and the isothermal tempering time is 10 to 15 hours.

[0015] Therefore, the present invention employs the above-mentioned method for preparing high-transmittance ice cubes, which has the following beneficial effects: (1) This invention adopts a dual strategy of source purification and dynamic regional refining to solve the problem of bubble and impurity retention from the root. By removing mineral impurities from the raw water through reverse osmosis treatment, crystallization nucleation points are eliminated. Combined with vacuum degassing to promote the overflow of dissolved gas, and with the steep temperature gradient formed by the low temperature cooling ring and auxiliary heat source, as well as the cavitation degassing effect of the ultrasonic transducer, bubbles and impurities are effectively prevented from being frozen in the ice body.

[0016] (2) This invention uses a PID closed-loop control system to precisely synchronize the moving speed of the low-temperature cooling ring with the ice crystal growth rate, avoiding layered defects caused by freezing rate fluctuations; the temperature of the low-temperature cooling ring is dynamically adjusted according to the vertical position, combined with constant-temperature tempering after freezing, significantly reducing thermal stress in the ice and preventing crack formation; ultrasonic vibration destroys the adhesion of bubbles to the mold wall or impurity points, preventing the formation of vertical fine stripes (wormholes). The resulting ice block is free of cracks and internal inclusions, has high compressive strength, and can be used as a load-bearing masonry unit for large ice buildings, and can also withstand the mechanical operations of fine carving.

[0017] (3) The present invention adopts dynamic regional refining technology with local heat removal, which only performs high-intensity heat removal on the 5-10cm high “active freezing zone” covered by the low temperature cooling ring, while the remaining water to be frozen is kept at room temperature or slightly cold, which greatly reduces the heat load of the refrigeration unit; at the same time, the waste heat of the refrigeration compressor is recovered as an auxiliary heat source to replace the additional electric heating, which significantly improves the thermodynamic efficiency of the system, solves the problem of high energy consumption and large environmental footprint of traditional ice making methods, and reduces the cost of industrial production and commercial application.

[0018] (4) The ice blocks prepared by this invention are standardized in size and have high geometric precision, which can be adapted to different scene requirements. They can meet the fine carving requirements of high-end ice sculpture competitions, provide load-bearing structural components for large ice buildings such as ice hotels and ice castles, and can also be used for high-end beverage cooling in commercial catering and brand ice wall display for corporate events. Moreover, the production process parameters are controllable, and the moving speed of the low temperature cooling ring and the temperature gradient can be flexibly adjusted according to the mold size (height 0.33-1.2m). It has strong adaptability and is easy to promote industrially.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 It is the light transmittance of the ice cubes prepared in Examples 1-3 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0021] This invention provides a method for preparing high-transmittance ice cubes, comprising the following steps: S1. Pretreatment: The raw water is subjected to reverse osmosis and vacuum degassing to obtain pretreated raw water. S2. Freezing: A low-temperature cooling ring is set on the outer periphery of the bottom of the freezing mold, and an auxiliary heat source is set above the low-temperature cooling ring. A refrigerant circulation channel is set inside the low-temperature cooling ring. An ultrasonic transducer is set on the top of the freezing mold. The freezing mold is equipped with a proportional-integral-derivative closed-loop control system. The heat of the auxiliary heat source is provided by the waste heat of the refrigeration compressor. The pretreated raw water in S1 is injected into the freezing mold through a sealed pipeline. The low-temperature cooling ring is pre-cooled, and the auxiliary heat source and ultrasonic transducer are started. The low-temperature cooling ring and auxiliary heat source move upward from the bottom of the freezing mold to freeze. S3. Post-processing: After freezing, temper at a constant temperature, demold, and obtain ice blocks with high light transmittance.

[0022] In this invention, in S1, the raw water is selected from pure water or distilled water, the desalination rate of the reverse osmosis treatment is ≥98%, the conductivity of the raw water after reverse osmosis treatment is ≤5μS / cm, the total dissolved solids of the raw water after reverse osmosis treatment is ≤3mg / L, the pressure of vacuum degassing is 0.02~0.08atm, and the vacuum degassing time is 20~40min.

[0023] Pure or distilled water is selected and treated with reverse osmosis to remove impurities at the source, eliminating crystallization nucleation sites caused by suspended minerals. The raw water undergoes vacuum degassing using Henry's Law, placing it in a slightly positive pressure vacuum environment to allow dissolved oxygen and nitrogen to escape. The degassed water is then pumped into the mold through sealed pipelines, completely isolating it from atmospheric contact to prevent gas re-dissolution.

[0024] In this invention, in step S2, the distance between the top of the freezing mold and the surface of the pretreated raw water is 5-10 cm. This space is used to accommodate impurities and gases discharged upwards during the freezing process. After freezing, this portion of water rich in impurities is discharged first before further processing.

[0025] In this invention, in S2, the height of the freezing mold is 0.33~1.2m, the diameter or side length of the freezing mold is determined according to the specifications of the ice block, and the inner dimension of the low-temperature cooling ring matches the outer dimension of the freezing mold. This invention does not impose any limitations on this.

[0026] In this invention, in S2, the pre-cooling temperature of the low-temperature cooling ring is -35℃ to -25℃, the moving speed is 1 to 5 mm / h, and the axial temperature gradient is 0.1 to 0.6℃ / cm.

[0027] In an embodiment of the present invention, when the height of the freezing mold is 0.33~0.8m, the moving speed of the low-temperature cooling ring is 1~3mm / h, and the axial temperature gradient is 0.1~0.3℃ / cm; when the height of the freezing mold is 0.8~1.2m, the moving speed of the low-temperature cooling ring is 3~5mm / h, and the axial temperature gradient is 0.3~0.6℃ / cm.

[0028] The temperature of the cryogenic cooling ring is dynamically adjusted as its vertical position increases. When the cryogenic cooling ring is at the bottom initial stage, a lower cooling temperature is set to initiate rapid nucleation; as the cryogenic cooling ring moves upward and the ice thickness increases, the control system gradually increases the temperature of the cooling ring to reduce the temperature gradient between the newly formed ice and the frozen ice, thereby controlling the internal thermal stress below the material's fracture threshold.

[0029] In this invention, in S2, the distance between the low-temperature cooling ring and the auxiliary heat source is 3~8cm.

[0030] The cryogenic cooling ring performs high-intensity heat removal only on a region within its 5-10cm height. An auxiliary heat source, positioned 3-8cm above the cooling ring, ensures heat coverage of the area to be frozen above it. The cooling ring moves upwards from the bottom of the mold, while the auxiliary heat source establishes a steep temperature gradient above the solid-liquid interface. This temperature gradient forces the ice crystal growth interface to remain flat (planar growth), rather than the traditional dendritic growth (dendritic growth). The flat crystallization front efficiently repels bubbles and impurities into the liquid water above. The water above the cooling ring remains at room temperature or slightly cooled, significantly reducing the heat load on the refrigeration unit.

[0031] In this invention, in step S2, the refrigerant flow rate is 2~3 m / s, and the refrigerant can be an environmentally friendly refrigerant known to those skilled in the art.

[0032] In this invention, in S2, the frequency of the ultrasonic transducer is 20~40kHz, and the power of the ultrasonic transducer is 50~150W.

[0033] To further remove trapped air bubbles at the interface, this invention utilizes an ultrasonic transducer mounted on the top of the mold to generate high-frequency vibrations. The shearing force and cavitation effect of the ultrasound at the solid-liquid interface detach tiny air bubbles adhering to the ice surface and aggregate them into larger bubbles that float to the surface. This achieves continuous cleaning of the boundary layer without requiring a large volume of pumped water to disturb the stagnant water. Furthermore, the ultrasonic vibrations also disrupt the adhesion of air bubbles to the mold wall or impurity points, preventing them from forming continuous air channels.

[0034] In this invention, in step S3, the isothermal tempering temperature is -8℃ to -2℃, and the isothermal tempering time is 10 to 15 hours. After freezing, a period of isothermal tempering is maintained to release the residual stress inside the ice block.

[0035] A proportional-integral-derivative (PID) closed-loop control system can monitor the temperature of the solid-liquid interface and the moving speed of the cryogenic cooling ring in real time. The PID system precisely adjusts the refrigerant flow rate through a variable frequency compressor or proportional valve to ensure that the moving speed of the cryogenic cooling ring and the ice crystal growth rate are always strictly linearly synchronized, avoiding the capture of impurity layers due to sudden rate changes, thereby generating a monolithic ice block with uniform optical properties and no layered defects.

[0036] The refrigeration compressor generates waste heat during operation. This waste heat is collected by a heat exchanger and directed to an auxiliary heat source above the cooling ring. This recovered heat is used to maintain the steep temperature gradient required at the solid-liquid interface, avoiding the energy consumption of additional electric heating and utilizing heat energy that would otherwise be wasted, thus significantly improving the overall thermodynamic efficiency of the system.

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0039] In this invention, unless otherwise specified, the test materials and instruments are all conventional test materials in the field and can be purchased through commercial channels.

[0040] Example 1 A method for preparing high-transmittance ice cubes includes the following steps: S1. Pretreatment: Pure water was selected as the raw water and subjected to reverse osmosis treatment to control the desalination rate ≥98%. The conductivity of the treated raw water was 3μS / cm and the total dissolved solids were 2mg / L. Subsequently, vacuum degassing was performed at a pressure of 0.05atm for 30min to obtain the pretreated raw water. S2. Freezing: A cubic freezing mold with a height of 0.6m and a side length of 40cm is selected. The inner dimensions of the low-temperature cooling ring match the outer dimensions of the mold. The auxiliary heat source is located 5cm above the low-temperature cooling ring. The heat of the auxiliary heat source is provided by the waste heat of the refrigeration compressor. The refrigerant used is environmentally friendly R410A with a flow rate of 2.5m / s. An ultrasonic transducer with a frequency of 30kHz and a power of 100W is installed on the top of the freezing mold. The mold is equipped with a PID closed-loop control system. Pretreated raw water is injected into the mold through a sealed pipeline, leaving an 8cm space between the liquid level and the top of the mold; the low-temperature cooling ring is pre-cooled to -30℃, the auxiliary heat source and ultrasonic transducer are started, and the low-temperature cooling ring moves upward from the bottom of the mold at a speed of 2mm / h, with an axial temperature gradient of 0.2℃ / cm. During the freezing process, the refrigerant flow rate is adjusted in real time through the PID system to match the ice crystal growth rate. S3. Post-processing: After freezing, first drain the water rich in impurities from the top, then temper at a constant temperature of -5℃ for 12 hours, demold, and obtain ice blocks with high light transmittance.

[0041] Example 2 This embodiment operates the same as Embodiment 1, except that in S2, the height of the freezing mold is 1m, the moving speed of the low-temperature cooling ring is 4mm / h, the axial temperature gradient is 0.4℃ / cm, and the distance between the low-temperature cooling ring and the auxiliary heat source is 6cm.

[0042] Example 3 This embodiment operates the same as Embodiment 1, except that: in S1, the vacuum degassing pressure is 0.08 atm and the degassing time is 40 min; in S2, the frequency of the ultrasonic transducer is 40 kHz and the power is 150 W, the constant temperature tempering temperature is -2℃ and the tempering time is 15 h.

[0043] Comparative Example 1 This comparative example operates in the same way as Example 1, except that in S1, the reverse osmosis treatment step is omitted and the pure water is directly degassed under vacuum; in S2, the distance between the low-temperature cooling ring and the auxiliary heat source is 10cm.

[0044] Comparative Example 2 The operation of this comparative example is the same as that of Example 1, except that: in S1, the vacuum degassing step is omitted and only the pure water is subjected to reverse osmosis treatment; in S2, no low-temperature cooling ring and auxiliary heat source are set around the freezing mold, and the ultrasonic transducer at the top is not activated, that is, the traditional overall cooling freezing method is adopted.

[0045] The number of air bubbles in the high-transmittance ice blocks prepared in Examples 1-3 and Comparative Examples 1-2 was observed using a stereomicroscope. The standard sample (20cm×20cm×5cm) was cut into four sub-samples of 10cm×10cm×5cm each. Two observation points were selected in the central and edge regions of each sub-sample. Cross-sectional images of the observation points were captured using a stereomicroscope, and the number of air bubbles was automatically counted using image analysis software. The unit volume (cm³) was calculated. 3 The average number of bubbles within the range is shown in Table 1.

[0046] Table 1 Number of air bubbles inside ice cubes

[0047] As can be seen from Table 1, the number of air bubbles in the ice cubes prepared in Examples 1, 2, and 3 is extremely low, all ≤0.1 bubbles / cm³. 3The ice blocks prepared in Comparative Examples 1-2 had a significantly higher number of bubbles than those in Examples 1-3. In Comparative Example 1, the raw water was not treated with reverse osmosis, making it impossible to effectively remove minerals and other impurities. These impurities act as nucleation points during freezing, making it difficult for bubbles and impurities to be repelled by the crystallization front, ultimately resulting in a large amount remaining inside the ice block. Comparative Example 2 did not employ a dynamic zone refining method (including directional movement of the low-temperature cooling ring, gradient control of the auxiliary heat source, and the cavitation effect of ultrasound), thus failing to continuously and efficiently remove bubbles from the boundary layer during crystallization, causing bubbles to remain inside the ice block.

[0048] The transmittance of high-transmittance ice blocks prepared in Examples 1-3 and Comparative Examples 1-2 was tested using a UV-Vis spectrophotometer. A wavelength of 550 nm was selected. The prepared ice blocks were cut into standard samples of 20cm × 20cm × 5cm, ensuring the sample surface was flat and free of scratches and cracks. Using air as a reference, the sample was placed vertically in the optical path, and the transmittance value displayed by the spectrophotometer was recorded. Three different locations were tested for each sample, and the average value was taken as the final transmittance value. The results are as follows: Figure 1 As shown.

[0049] from Figure 1 As can be seen, the light transmittance of the ice blocks prepared in Examples 1-3 is higher than 95%, which is significantly higher than that of Comparative Examples 1-2. This indicates that the present invention, through the dual strategy of "source purification (reverse osmosis pure water or distilled water + vacuum degassing) and dynamic zone refining (low temperature cooling ring + auxiliary heat source + ultrasound)," suppresses the retention of bubbles and impurities from both the source of impurities and the crystallization process. Traditional methods are difficult to achieve such precise defect control.

[0050] Therefore, this invention employs the aforementioned method for preparing high-transmittance ice cubes. Through a dual strategy of source purification and dynamic regional refining, combined with precise PID closed-loop control, dynamic temperature regulation of the low-temperature cooling loop, and recovery and utilization of refrigeration waste heat, it achieves an ice cube transmittance ≥95% and an internal bubble count ≤0.1 / cm². 3 Its high optical quality eliminates structural problems such as cracks and layered defects, significantly reducing production energy consumption and site occupation. It is suitable for various scenarios such as high-end ice sculptures, large ice buildings, and commercial catering, taking into account product performance, production efficiency, and energy conservation and environmental protection.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing high-transmittance ice cubes, characterized in that: Includes the following steps: S1. Pretreatment: The raw water is subjected to reverse osmosis and vacuum degassing to obtain pretreated raw water. S2. Freezing: A low-temperature cooling ring is set on the outer periphery of the bottom of the freezing mold, and an auxiliary heat source is set above the low-temperature cooling ring. A refrigerant circulation channel is set inside the low-temperature cooling ring. An ultrasonic transducer is set on the top of the freezing mold. The freezing mold is equipped with a proportional-integral-derivative closed-loop control system. The heat of the auxiliary heat source is provided by the waste heat of the refrigeration compressor. The pretreated raw water in S1 is injected into the freezing mold through a sealed pipeline. The low-temperature cooling ring is pre-cooled, and the auxiliary heat source and ultrasonic transducer are started. The low-temperature cooling ring and auxiliary heat source move upward from the bottom of the freezing mold to freeze. S3. Post-processing: After freezing, temper at a constant temperature, demold, and obtain ice blocks with high light transmittance.

2. The method for preparing a high-transmittance ice block according to claim 1, characterized in that: In S1, the raw water is selected from pure water or distilled water, the desalination rate of reverse osmosis treatment is ≥98%, the conductivity of the raw water after reverse osmosis treatment is ≤5μS / cm, the total dissolved solids of the raw water after reverse osmosis treatment is ≤3mg / L, the pressure of vacuum degassing is 0.02~0.08atm, and the vacuum degassing time is 20~40min.

3. The method for preparing a high-transmittance ice block according to claim 1, characterized in that: In S2, the distance between the top of the freezing mold and the surface of the pretreated raw water is 5~10cm.

4. The method for preparing a high-transmittance ice block according to claim 1, characterized in that: In S2, the height of the freezing mold is 0.33~1.2m.

5. The method for preparing a high-transmittance ice block according to claim 1, characterized in that: In S2, the pre-cooling temperature of the low-temperature cooling ring is -35℃ to -25℃, the moving speed is 1 to 5 mm / h, and the axial temperature gradient is 0.1 to 0.6℃ / cm.

6. The method for preparing a high-transmittance ice block according to claim 1, characterized in that: In S2, the distance between the low-temperature cooling ring and the auxiliary heat source is 3~8cm.

7. The method for preparing a high-transmittance ice block according to claim 1, characterized in that: In S2, the frequency of the ultrasonic transducer is 20~40kHz, and the power of the ultrasonic transducer is 50~150W.

8. The method for preparing a high-transmittance ice block according to claim 1, characterized in that: In S3, the isothermal tempering temperature is -8℃ to -2℃, and the isothermal tempering time is 10 to 15 hours.

Images