Subcooled water preparation system and ice making system having the same

Abstract

This invention provides a supercooled water preparation system and an ice-making system thereon. The supercooled water preparation system includes a nonfreezing fluid flow system, a water flow system, and a control system. The nonfreezing fluid flow system is connected via pipelines to form a circulation loop, consisting of a first thermostatic device, a first water pump, a first flow meter, a first pressure gauge, and a compact heat exchanger. The water flow system includes, via pipelines, a second thermostatic device connected to a water source and controlling the water temperature, a second water pump, a second flow meter, a second pressure gauge, and the compact heat exchanger. The control system detects and adjusts the operation of the entire system.

Description

Technical Field

[0001] This invention relates to the field of supercooled water and ice / snow manufacturing technology, specifically to a supercooled water preparation system and an ice-making system having the same. Background Technology

[0002] Water that does not freeze below 0°C is called subcooling water. Utilizing the high latent heat and rapid cooling characteristics of the ice or ice slurry continuously generated from subcooling water, it is used as a cooling medium in dynamic ice storage air conditioning systems. In dynamic ice storage systems, heat exchangers play a crucial role in the continuous generation of subcooling water. Currently, improved coaxial heat exchangers and plate heat exchangers are mainly used to continuously generate subcooling water for ice storage. However, the random occurrence of ice blockage leads to intermittent generation of subcooling water; once ice blockage occurs, subcooling water generation can only occur after the ice melts.

[0003] For supercooled water generation systems, restarting after a shutdown leads to increased energy consumption. In dynamic ice storage systems, supercooled water at -1℃ to -2℃ is often used for cold storage, while the IPF (ice fill factor) of the ice storage tank is generally 30% to 40%, resulting in wasted space. This is mainly because the degree of supercooling is small; after the supercooling is released, only a small portion of the supercooled water converts into ice, requiring continuous circulation and heat exchange in the ice storage tank for further cooling to increase the ice storage capacity. Lower-temperature supercooled water has higher energy and is more easily converted into ice or ice slurry after the supercooling is released, leading to a wider range of applications, such as indoor snowmaking and food preservation.

[0004] Currently, there are research papers on continuously generating supercooled water using plate heat exchangers or other types of heat exchangers for ice storage, but the temperature reached by the supercooled water is limited to -3.3℃, ​​and the duration is about 10 minutes. How to generate supercooled water at even lower temperatures and for a longer duration remains a challenge in the field of supercooled water manufacturing and requires further exploration.

[0005] In view of this, it is necessary to provide an improved supercooled water preparation system and an ice-making system having the same, in order to solve the above-mentioned technical problems. Summary of the Invention

[0006] The purpose of this invention is to provide a supercooled water preparation system and an ice-making system having the same.

[0007] To solve one of the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A supercooled water preparation system includes an antifreeze flow system, a water flow system, and a control system;

[0009] The antifreeze flow system is connected by pipelines to form a circulation loop, including a first thermostatic device, a first water pump, and a compact heat exchanger. The compact heat exchanger includes several water channel plates and several antifreeze channel plates, which are alternately stacked to form alternating water channels and antifreeze channels. Each of the water channel plates and antifreeze channel plates is provided with several microstructures, which are located within the water channels and antifreeze channels.

[0010] The water flow system includes, via pipes, a second thermostatic device connected to a water source and controlling the water temperature, a second water pump, and the compact heat exchanger;

[0011] The control system is communicatively connected to the first thermostatic device, the first water pump, the second thermostatic device, and the second water pump. The control system includes a first inlet temperature sensor connected to the inlet of the antifreeze channel, a first outlet temperature sensor connected to the outlet of the antifreeze channel, a first flow meter and a first pressure gauge connected to the antifreeze flow system, a second inlet temperature sensor connected to the inlet of the water channel, a second outlet temperature sensor connected to the outlet of the water channel, and a second flow meter and a second pressure gauge connected to the water flow system.

[0012] Furthermore, the hydraulic equivalent diameter of the water channel and the antifreeze channel is no greater than 0.4 mm, and the length of the water channel and the antifreeze channel is no greater than 50 mm.

[0013] Furthermore, water flows through the water channel at a flow rate of 0.017 l / s to 0.032 l / s, and the time spent passing through the compact heat exchanger is 0.038 s to 0.072 s.

[0014] Furthermore, both the water channel plate and the antifreeze channel plate include a heat exchange zone, an inlet and an outlet communicating with the heat exchange zone, and a frame surrounding the heat exchange zone, with the microstructure located in the heat exchange zone.

[0015] Furthermore, the compact heat exchanger also includes a diffuser structure connected to the outlet of the water channel.

[0016] Furthermore, the compact microstructure also includes thermal insulation layers located at both ends of the stacking direction.

[0017] Furthermore, the water flow system further includes: a first secondary filter connected between the first thermostat and the compact heat exchanger, and / or a second filter connected between the second thermostat and the compact heat exchanger.

[0018] Furthermore, both the first filter and the second filter are 400-mesh metal meshes.

[0019] Furthermore, the first thermostatic device, the first ball valve, the first water pump, the first filter, the first flow meter, the first pressure gauge, the first inlet temperature sensor, the antifreeze channel, and the first outlet temperature sensor are connected in sequence to form a circulation loop, forming a flow path for the antifreeze; the second thermostatic device, the second ball valve, the second water pump, the second filter, the second flow meter, the second pressure gauge, the second inlet temperature sensor, the water channel, and the second outlet temperature sensor are connected in sequence to form a flow path for the water.

[0020] An ice-making system includes the aforementioned subcooled water ice-making system and an ice-making device located at the outlet of a compact heat exchanger.

[0021] Furthermore, the ice-making device is an ice bucket or an ice pool.

[0022] Furthermore, the ice-making system also includes a discharge port or discharge valve communicating with the bottom of the ice bucket; or, the ice-making system also includes a return pipe communicating with the ice bucket or the ice pool and the second thermostatic device, and a return water pump connected to the return pipe.

[0023] The beneficial effects of the present invention are: the supercooled water preparation system of the present invention uses a compact heat exchanger as the heat exchange unit between the antifreeze and water, which improves the heat exchange performance and reduces the transit time of the working fluid in the compact heat exchanger, thereby mitigating or avoiding the phenomenon of ice blockage. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a subcooling water preparation system according to a preferred embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of an ice-making system according to a preferred embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the compact heat exchanger of the present invention;

[0027] Figure 4 for Figure 3 A schematic diagram of the top or bottom structure of a compact heat exchanger;

[0028] Figure 5 for Figure 3 Schematic diagram of microstructured channel sheets, (a) is a water channel sheet, (b) is a nonfreezing channel sheet;

[0029] Figure 6 This is a schematic diagram of the experimental results of the supercooling water preparation system of the present invention for preparing cooling water. (a) Supercooling water T 2,out (a) Reaching -3.8℃; (b) Duration t reaching 108 min;

[0030] Figure 7 For different outlet water temperatures T 2,out The changes in heat exchange temperature difference ΔT and flow ratio i at time, where (a) the outlet water temperature T is -2.0℃. 2,out (b) -2.5℃ outlet water temperature T 2,out (c) -3.0℃ outlet water temperature T 2,out .

[0031] Figure 8 This is a schematic diagram of ice nucleus formation in the water channels inside a compact heat exchanger. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the scope of protection of the present invention.

[0033] In the various illustrations of this invention, for ease of illustration, certain dimensions of structures or parts are enlarged relative to other structural parts; therefore, only the basic structure of the subject matter of this invention is used to illustrate the invention.

[0034] Supercooled water exists in a metastable state; under homogeneous nucleation conditions, liquid water can reach -38°C. Ice formation involves ice nucleation (i.e., ice nucleus formation) and ice growth. For water below 0°C, the solid phase (ice) is thermodynamically more stable than the liquid phase because the free energy of each molecule in the solid phase is lower than that in the liquid phase. However, when a small ice embryo forms and grows in the liquid phase, the total free energy of the system increases with the growth of the ice embryo due to the increase in interfacial free energy. Therefore, water can be cooled below 0°C and exist in a supercooled state without ice nuclei. Conversely, if the size of the ice embryo exceeds a critical value, depending on the degree of supercooling, the total free energy will decrease with the growth of the ice embryo, thus initiating the ice nucleation process. When ice begins to form, it must be accompanied by the growth of ice nuclei. Ice nucleation is extremely rare in homogeneous liquid water.

[0035] This invention optimizes the design of the supercooling water preparation system 100 and the preparation method.

[0036] Please refer to Figures 1-5As shown, the supercooled water preparation system 100 of the present invention includes a non-freezing liquid flow system 2, a water flow system 3, and a control system. The non-freezing liquid (LLC) in the non-freezing liquid flow system 2 and the water in the water flow system 3 flow through two fluid channels of the same compact heat exchanger 1, where they exchange heat to prepare supercooled water; wherein, the fluid channels can also be understood as heat exchange channels for the fluids. The control system detects and controls the entire system to ensure stable and continuous supercooled water preparation.

[0037] The control system includes a data acquisition unit, a data processing unit, and a command sending unit. The data acquisition unit collects information from the antifreeze flow system 2 and the water flow system 3. After processing by the data processing unit, the command sending unit sends commands to the antifreeze flow system 2 and the water flow system 3 to adjust the system operation in order to obtain cooler subcooling water.

[0038] The acquisition unit includes the following components connected to the antifreeze flow system 2: a first inlet temperature sensor connected to the inlet of the antifreeze channel, a first outlet temperature sensor connected to the outlet of the antifreeze channel, a first flow meter 23 for detecting the flow rate of the antifreeze entering the compact heat exchanger 1, and a first pressure gauge 24 for acquiring the pressure of the antifreeze flow system 2.

[0039] The acquisition unit includes the following components connected to the water flow system 3: a second inlet temperature sensor connected to the inlet of the water channel, a second outlet temperature sensor connected to the outlet of the water channel, a second flow meter 33 for detecting the flow rate of the antifreeze entering the compact heat exchanger 1, and a second pressure gauge 34 for acquiring the pressure of the antifreeze flow system 2.

[0040] For details on how the various components of the acquisition unit are connected to the antifreeze flow system 2 and the water flow system 3, please refer to [reference needed]. Figures 1-2 And the following description.

[0041] The antifreeze flow system 2 includes a first thermostatic device 21, a first water pump 22, and the compact heat exchanger 1 connected by pipelines to form a circulation loop. When the first water pump 22 is started, the antifreeze circulates in the circulation loop.

[0042] The first thermostatic device 21 is used to lower and control the temperature of the antifreeze within a first preset temperature range, so as to provide the supercooling water preparation system 100 with antifreeze at a relatively constant temperature.

[0043] In addition, considering the heat loss of the pipeline, the first constant temperature device 21 reduces the temperature of the antifreeze to -8.0℃ to -10.0℃ through the refrigeration system, ensuring that the inlet temperature of the antifreeze at the inlet of the compact heat exchanger 1 is controlled at -6.0℃ to -8.0℃, providing continuous and stable cooling to the water, so that the outlet water temperature of the compact heat exchanger 1 reaches the expected subcooling requirement.

[0044] The first water pump 22 provides power for the circulation of antifreeze, and is preferably a variable frequency pump, which facilitates the adjustment of flow rate and system pressure.

[0045] Furthermore, the antifreeze flow system 2 also includes a first filter 25, which is used to filter the antifreeze, removing insoluble solid particles and other contaminants to prevent them from affecting heat exchange performance within the antifreeze channels. In one reference embodiment, the first filter 25 is a 400-mesh metal mesh, preferably a stainless steel mesh, to prevent corrosion and contamination of the antifreeze.

[0046] Preferably, along the flow direction of the antifreeze, the first filter 25 is located upstream of the first flow meter 23, the first pressure gauge 24, and the compact heat exchanger 1, where upstream refers to the upstream direction of fluid flow.

[0047] In addition, the antifreeze flow system 2 also includes a first ball valve 26 to improve the precise control of the system.

[0048] To avoid the influence of other components and ensure the accuracy of the collected data, the first water pump 22, the first flow meter 23, the first pressure gauge 24, and the compact heat exchanger 1 are arranged in sequence along the flow direction of the antifreeze.

[0049] In one specific embodiment, the first thermostatic device 21, the first ball valve 26, the first water pump 22, the first filter 25, the first flow meter 23, the first pressure gauge 24, the first inlet temperature sensor, the compact heat exchanger 1, the first outlet temperature sensor, and the first thermostatic device 21 are sequentially connected to form a circulation loop for the antifreeze.

[0050] The water flow system 3 includes the following components connected by pipes: a second thermostat 31 connected to a water source and controlling the water temperature, a second water pump 32, and a compact heat exchanger 1.

[0051] This invention aims to continuously and stably produce subcooled water using tap water as a source without further treatment, and to apply this technology industrially, for example, in ice making, where the ice includes, but is not limited to, ice crystals, ice pellets, and ice blocks. The subcooled water can also be used to produce snow; essentially, the aforementioned ice crystals and ice pellets can be understood as snow. Of course, tap water can also be treated before being used as the water source for the subcooled water preparation system 100; for example, by filtering, treating with an ion exchange column to form deionized water, or distilling to form distilled water, etc., to improve the water purity and further facilitate the preparation of subcooled water.

[0052] The second thermostatic device 31 is used to receive and store a certain amount of water, and to lower and control the temperature of the water within a second preset temperature range, so as to provide water with a relatively constant temperature for the supercooled water preparation system 100. The cooperation between the second thermostatic device 31 and the first thermostatic device 21 makes the temperature of the water and antifreeze entering the compact heat exchanger 1 relatively constant, thus keeping the outlet water temperature stable and preventing ice blockage.

[0053] In addition, the second thermostatic device 31 is used to control the water temperature so that the water entering the compact heat exchanger 1 is at a relatively constant temperature. In this invention, the inlet temperature of the water entering the compact heat exchanger 1 is controlled between 2.5°C and 4°C, for example, around 3°C, and the outlet temperature of the compact heat exchanger 1 is between -2°C and -3.8°C.

[0054] Among them, the first constant temperature device 21 and the second constant temperature device 31 are essentially temperature control devices, and the temperature of the fluid inside them is not constant, but the temperature fluctuation is relatively small.

[0055] The second water pump 32 provides power, preferably a variable frequency pump, for easy adjustment of flow rate and system pressure. The second flow meter 33 is used to detect the flow rate of water entering the compact heat exchanger 1, and the second pressure gauge 34 is used to detect the pressure.

[0056] Furthermore, the water flow system 3 also includes a second filter 35 connected between the second thermostat 31 and the compact heat exchanger 1. The second filter 35 is used to filter the water, remove insoluble solid particles, reduce the risk or probability of ice nucleation, and thus mitigate or avoid ice blockage. In one reference embodiment, the second filter 35 is a 400-mesh metal filter screen connected between the second water pump 32 and the compact heat exchanger 1.

[0057] In addition, the water flow system 3 also includes a second ball valve 36 to improve the precise control of the system.

[0058] Preferably, along the direction of water flow, the second filter 35 is located upstream of the second flow meter 33, the second pressure gauge 34, and the compact heat exchanger 1 to avoid changes in pressure and flow rate when water passes through the second filter 35.

[0059] In one specific embodiment, the second thermostat 31, the second ball valve 36, the second water pump 32, the second filter 35, the second flow meter 33, the second pressure gauge 34, the second inlet temperature sensor, the water channel of the compact heat exchanger 1, and the second outlet temperature sensor are connected in sequence through pipes. The second outlet temperature sensor detects whether the subcooling degree of the subcooled water flowing out from the outlet of the water channel meets the standard.

[0060] The compact heat exchanger 1 is the core component for heat exchange between the two fluid channel systems described above. The inventors discovered that ice nuclei form due to heterogeneous nucleation, and that certain factors, such as impurities in the water, minor energy disturbances, and cooling time, catalyze ice nucleation. In traditional plate heat exchangers used to generate subcooled water, once the water containing insoluble solid particles reaches the subcooling level, ice nuclei formed on the surface of these insoluble solids easily and rapidly freeze upon encountering minor energy disturbances, blocking the heat exchanger channels—a phenomenon commonly known as ice blockage. When ice blockage occurs, subcooled water generation must be stopped until the ice melts; for a subcooled water generation system, stopping and restarting leads to increased energy consumption.

[0061] After considering various factors affecting the continuous generation of subcooling water, it was found that laminar flow conditions are more likely to generate subcooling water, while turbulent flow conditions can improve heat transfer intensity, but wall friction, Reynolds number, and Nusselt number will reduce the degree of subcooling. Considering the influence of uncertainties on the continuous generation time t of subcooling water, such as the longer the heat exchange channel, the longer the water stays in the heat exchanger, and the greater the probability of being affected by uncertainties such as impurities, it is more advisable to reduce the hydraulic diameter of the heat exchange channel proportionally while reducing the length of the heat exchange channel.

[0062] This invention employs a compact heat exchanger for heat exchange. The compact heat exchanger 1 is designed based on a method combining thermal resistance balance with a microstructure 13. It has multiple layers of fluid channels, with water channels and antifreeze channels alternating, and each layer consisting of the same type of fluid channel. Each working fluid enters from its inlet, is separated by multiple layers of channels, and converges and flows out at the outlet.

[0063] Compact heat exchangers involve the concept of high-performance heat exchangers, meaning that the heat exchange area per unit volume should reach 500–700 m² / m. 3The hydraulic diameter should be less than 5 mm. This invention utilizes the high heat transfer coefficient of the compact heat exchanger 1, which can greatly shorten the heat exchange length, reduce the water flow time in the compact heat exchanger 1, and reduce the risk of ice blockage caused by uncertain factors.

[0064] Specifically, the compact heat exchanger 1 includes a plurality of water channel plates 11 and a plurality of antifreeze channel plates 12, which are stacked alternately. The plurality of water channel plates 11 and the plurality of antifreeze channel plates 12 form water channels and antifreeze channels with adjacent channel plates, respectively.

[0065] In this invention, each of the plurality of water channel plates 11 and the plurality of antifreeze channel plates 12 is provided with a microstructure 13. The microstructure 13 is located within the water channel and the antifreeze channel, and water and antifreeze flow through the gaps between the plurality of microstructures 13. The microstructure 13 can also provide support for adjacent channel plates.

[0066] The antifreeze channel and the water channel are collectively referred to as fluid channels. The hydraulic equivalent diameter of the fluid channel is no greater than 0.4 mm, the length of the fluid channel is no greater than 50 mm, and the number of channels is no less than 600. When water flows through the water channel at a flow rate of 0.017 l / s to 0.032 l / s, the time it takes to pass through the compact heat exchanger 1 is 0.038 s to 0.072 s.

[0067] This compact heat exchanger 1, by setting the size and gap of the microstructure 13, results in a smaller hydraulic diameter of the fluid channel, improving heat exchange between water and antifreeze. This significantly reduces the length of the fluid channel, thereby greatly reducing ice blockage. In other words, the compact heat exchanger 1 for continuously generating subcooled water is designed with a small hydraulic diameter and short channels, resulting in an average convective heat transfer coefficient far higher than conventional heat exchangers. Even with a short heat exchange channel length, such as less than 25 mm, heat exchange requirements can be guaranteed.

[0068] This paper describes a compact heat exchanger 1 used for continuous generation of subcooling water, with a heat transfer area of ​​2990 m² per unit volume. 2 / m 3 The fluid channel has a hydraulic diameter of 0.32 mm, a channel length of 21.5 mm, and 720 channels. The channel shape has two bends, making it a high-performance and compact heat exchanger. The compact heat exchanger 1 for continuously generating subcooled water is designed with a small hydraulic diameter and short channels. Its average convective heat transfer coefficient is much higher than that of conventional heat exchangers, ensuring heat exchange requirements even with short heat exchange channel lengths (less than 25 mm).

[0069] Please refer to Figures 3-5As shown, in this invention, the water channel plate 11 and the antifreeze channel plate 12 are collectively referred to as fluid channel plates 11 and 12, which are formed by photolithography using mirror-finished SUS316L sheets. Specifically, the fluid channel plates 11 and 12 include a heat exchange zone 14, an inlet and an outlet communicating with the heat exchange zone 14, and a frame 15 located around the heat exchange zone 14. The microstructure 13 is located in the heat exchange zone 14. The two types of fluid channel plates are alternately stacked between the bottom plate 10 and the top plate and are bonded together by atomic diffusion to form the compact heat exchanger 1.

[0070] Specifically, the heat exchange zone 14 is divided into an inlet zone, a transition zone, a turbulent zone, and an outlet zone. The microstructures 13 in the inlet zone and the outlet zone are elongated, such as elliptical, spindle-shaped, or rhomboid. The microstructures 13 in the transition zone are circular. The microstructures 13 in the turbulent zone are distributed along a sine line, and the connection between two microstructures 13 forms an adjacent crest-trough shape. This can also be understood as follows: on the crest-trough section, the middle part is etched away, and the two ends are retained as the microstructures 13.

[0071] The microstructures 13 in the inlet and outlet regions have low density and serve to guide the flow; the transition region is located in the middle and has a moderate density of microstructures 13, serving as a transition zone; the microstructures 13 in the turbulent region have high density and the best heat exchange performance.

[0072] In addition, in the turbulent region, the water flows in the opposite direction to the antifreeze, that is, they flow in opposite directions, or counter-current heat exchange, which further improves the heat exchange performance.

[0073] In one specific embodiment, the compact heat exchanger includes four units, each unit comprising three layers of water channel plates and four layers of antifreeze channel plates. In each fluid channel plate, the gap between the sinusoidal lines constitutes a channel.

[0074] Compared to other types of heat exchangers, using a compact heat exchanger 1 reduces the transit time of the working fluid in its channels, which is beneficial for improving the subcooling degree and duration of the tap water. However, ice blockage still occurs because after the subcooled water and tap water combine, the subcooled water often freezes instantly due to the formation of ice nuclei caused by certain factors. The greater the subcooling degree, the faster the ice nuclei grow due to the diffusion of latent heat. The subcooled water in the heat exchanger channels is prone to instantaneous freezing after being subjected to small bursts of energy disturbance, resulting in ice blockage.

[0075] In the exploration of increasing subcooling, imperceptible trace amounts of ice sometimes appear on the surface of the heat exchanger and the outer wall of the outlet. This trace ice, as a small form of energy disturbance, may be one of the causes of ice blockage. Whenever the generation of subcooling water stops, the water passages of the heat exchanger freeze almost instantly, and a mixture of ice and water is found at the outlet. It can be inferred that excessive distribution of impurities in the water within a certain time and space creates dense ice nuclei, such as… Figure 8 As shown. Therefore, using a multi-channel system to disperse fine particles in tap water as much as possible and allow them to flow out of the heat exchanger channels before latent heat diffusion is complete, thereby minimizing unnecessary interference from minute energy sources in the heat exchanger channels, may be an effective means of achieving lower-temperature subcooling water and reducing ice blockage.

[0076] Furthermore, the compact heat exchanger 1 also includes insulation layers at both ends in the stacking direction; these layers protect the ends of the compact heat exchanger 1 from excessive condensation or even ice formation, so as to prevent the flow of subcooled water from being affected at the outlet of the water channel.

[0077] In addition, such as Figure 3 As shown, the compact heat exchanger 1 further includes a diffuser structure connected to the outlet of the water channel, the diffuser structure being funnel-shaped or conical. In one embodiment, the diffuser structure is a diffuser tube.

[0078] Table 1 provides an overview and describes the working fluid of the compact heat exchanger 1.

[0079] External dimensions mm 40L×40W×22.6H Working fluid - High temperature: tap water; Low temperature: antifreeze, backflow Rated flow rate L / min 3L / min, room temperature Materials used - SUS316L, Mirror Finish Channel processing - Photoetching Structural processing - Atomic diffusion bonding Performance testing - <![CDATA[Leakage: < 10 -10 Pa·m3 / s; Pressure resistance > 6.9 MPa]]>

[0080] The supercooling water preparation system 100 and preparation method of the present invention are tested using a compact heat exchanger 1, which has better heat exchange performance than a plate heat exchanger and a significantly shorter fluid channel length. By exploring the inlet water temperature, flow rate, and transit time of the compact heat exchanger 1, it is expected to obtain a lower degree of supercooling and a longer duration t.

[0081] Specifically, this invention uses tap water and antifreeze as working fluids, and a compact heat exchanger 1 as described above as a heat exchange unit for continuously generating subcooled water. A first water pump 22 and a second water pump 32 are used to adjust the flow rates q1 and q2 of the antifreeze and water, respectively. A first temperature control device 21 and a second temperature control device 31 are used to adjust the fluid inlet temperature T of the antifreeze and water entering the compact heat exchanger 1, respectively. 1,in T 2,in The minimum achievable subcooling water temperature and duration t are determined; based on the collected basic data, existing problems are analyzed and solutions are proposed.

[0082] When considering the continuous generation conditions of cooling water, based on the principle of energy conservation, when the temperature T of the tap water... 2,inThe inlet temperature T of the antifreeze is set at 3℃, and the flow rate is determined based on the design range of the heat exchanger. 1,in The determination of the flow rate must be matched with the target subcooling degree of the generated tap water. Consequently, the determination of the flow rate generally requires trial and error after considering various uncertainties such as heat leakage from the heat exchanger.

[0083] The supercooled water preparation method of the present invention includes the following steps: S1, turning on the first thermostat 21 of the antifreeze flow system 2 to control the temperature of the antifreeze to a first preset temperature range; S2, turning on the second thermostat 31 of the water flow system 3 to control the temperature of the water to a second preset temperature range; S3, after the water temperature reaches the second preset temperature range, turning on the second water pump 32 of the water flow system 3 to control the inlet temperature T of the water entering the water channel of the compact heat exchanger 1. 2,in The temperature tends to stabilize; the inlet temperature T of the water entering the compact heat exchanger 1 from S4. 2,in After the temperature stabilizes, the first water pump 22 of the antifreeze flow system 2 is turned on, and the antifreeze flows through the antifreeze channel of the compact heat exchanger 1. The flow rate of the antifreeze q1 and the flow rate of the water q2 are adjusted so that the temperature of the water flowing out of the compact heat exchanger 1 reaches the expected subcooling degree.

[0084] S1 to S4 are used for illustrative purposes only and do not represent a fixed order. For example, the opening order of the first thermostat 21 and the second thermostat 31 in steps S1 and S2 is not limited; they can be opened simultaneously or sequentially. However, step S4 is located after step S3.

[0085] In step S3, the effect of water flow fluctuations on the inlet water temperature T is taken into account. 2,in The influence of this effect is adjusted by regulating the frequency of the second water pump 32 and controlling the water flow rate q1, so that the inlet temperature T of the water entering the water channel of the compact heat exchanger 1 is controlled. 2,in It is trending towards stability.

[0086] In step S4, after starting the first water pump 22, the flow rate q1 of the antifreeze is first adjusted to its maximum value, for example, 1.9 L / min; when the inlet temperature T of the antifreeze entering the compact heat exchanger 1 is... 1,in After stabilizing, the water flow rate q2 is further adjusted to achieve an outlet temperature T of the water flowing out of the compact heat exchanger 1. 1,out The desired degree of supercooling was achieved.

[0087] In this invention, the flow rate q1 of the antifreeze is adjusted to its maximum value based on the temperature of the antifreeze; the flow rate q2 of the water is determined by the cooling conditions. In the initial stage of the experiment, the flow rates of both the antifreeze and the water decrease to some extent, eventually stabilizing, with the antifreeze experiencing a larger decrease. This is because the temperature of the circulating antifreeze is lower than that of the tap water, and it suffers greater heat loss (temperature rise of 2-3 K). Therefore, the first temperature control device for the antifreeze needs to be set at a lower temperature to ensure the required inlet temperature.

[0088] The flow rate of the antifreeze should be higher than that of the tap water to increase turbulence intensity and avoid excessive temperature difference between the two sides. The flow ratio i is defined as the ratio of the flow rate of the antifreeze to that of the tap water. The result of the change in temperature difference ΔT between the working fluids in the heat exchanger is as follows: Figure 7 As shown. From Figure 7 It can be seen that by setting the flow ratio i in the range of 1.3 to 1.9, when the subcooling degree of the tap water-to-cooled water increases, the change in i tends to slow down, and the change in the temperature difference ΔT between the working fluid entering and exiting the heat exchanger also slows down. For Figure 7 As shown, the reason why the change in working fluid temperature difference ΔT also slows down due to the slowing change in flow ratio i needs further clarification in the future.

[0089] Preferably, the volumetric flow rate q1 of the antifreeze entering the compact heat exchanger 1 is ≤ 1.90 L / min, and the volumetric flow rate q2 of the water entering the compact heat exchanger 1 is between 1.00 L / min and 1.30 L / min; thus, supercooled water can be prepared stably and for a long time.

[0090] The temperature T of the antifreeze entering the compact heat exchanger 1 1,in The temperature T of the water entering the compact heat exchanger 1 is between -6.0℃ and -8.0℃. 2,in Between 2.5℃ and 4℃, the subcooling degree of the water can be well controlled within the expected range. In one specific embodiment, the temperature T of the tap water... 2,in It remains constant at 3℃, but may fluctuate slightly due to other factors.

[0091] The following detailed description of the supercooling water preparation system 100 and its preparation method according to a specific embodiment of the present invention will be provided below.

[0092] Table 2 Experimental conditions

[0093]

[0094] The water source is tap water from Jinhua City, Zhejiang Province, which is directly connected to the second constant temperature device 31 without treatment.

[0095] At the start of the experiment, the temperatures of the tap water and the antifreeze LLC were first set to the temperatures shown in Table 2 using a thermostat. Once the tap water temperature reached the target value of 3.0℃, the frequency of the second water pump 32 was adjusted to maintain the temperature T of the tap water entering the compact heat exchanger 1. 2,in The flow rate tends to a certain level. Then, the first water pump 22 in the antifreeze circuit is turned on, so that the antifreeze flow rate q1 reaches its maximum value. When the inlet temperature T of the antifreeze entering the compact heat exchanger 1 reaches a certain level... 1,in After stabilizing, further fine-tune the flow rate q2 in the tap water circuit to continuously generate subcooled water at the desired subcooling degree.

[0096] During the preparation process, the sampling frequency for the following parameters was 1 second: the temperature of the antifreeze entering and exiting the compact heat exchanger 1; the temperature of the water entering and exiting the compact heat exchanger 1; the antifreeze flow rate q1; and the water flow rate q2. The sampling time t was until ice blockage occurred in the compact heat exchanger 1. The experimental results are as follows: Figure 6 and Figure 7 As shown.

[0097] like Figure 6 As shown in (a), when the inlet temperature T of the tap water 2,in At 3°C, from the start of the experiment until the supercooling water reaches steady state, there is a non-steady process of temperature change over time, which lasts for about 3 minutes. During the steady-state process, there will be slight temperature changes, which may be caused by fluctuations in the inlet temperature and flow rate of the two fluids in the compact heat exchanger 1.

[0098] When the continuous supercooling water generation time t is greater than 5 min, the results of a total of 88 experiments are classified according to the achieved degree of supercooling. The continuous steady-state times are summarized as follows:

[0099] Of the 46 experiments with a supercooling degree of 2.5K, 21 had a duration t greater than 10 min. Among these 21 experiments, 10 had a duration greater than 16 min, 4 had a duration greater than 25 min, and the longest duration t was greater than 100 min.

[0100] There were 31 instances where the supercooling reached 3K, 18 instances where the duration t was greater than 10 minutes, 8 instances where the duration was greater than 16 minutes, 5 instances where the duration was greater than 25 minutes, and the longest duration t was greater than 46 minutes.

[0101] There were 21 instances where the supercooling reached 3.5 K, 3 of which had a duration t greater than 10 min, with the longest duration t exceeding 28 min. In one experiment with a supercooling of 2.8 K, the duration t exceeded 100 min. Figure 6As shown in (b).

[0102] In the above classification of experimental results, some experiments, even under the same conditions, had different durations. This may be due to the influence of environmental changes, which may have caused the temperature control device to be unable to respond effectively. Furthermore, as the degree of supercooling of tap water increases, the duration of continuous generation, t, decreases. This may be attributed to the rapid diffusion of ice nuclei caused by impurities in tap water due to the increased degree of supercooling. The energy disturbance caused by, for example, the two bends in the shape of the water-side channel of the heat exchanger caused ice blockage in the heat exchanger channel.

[0103] We know that tap water contains solid particles, such as colloidal solids composed of calcium and magnesium ions, or other impurities. Ice nuclei appear on the surface of these insoluble solids and have different properties from the ice nuclei that grow from the ice embryo. With these ice nuclei present, ice in the water will grow along with the diffusion of latent heat. When this growth reaches a certain point, ice blockage will occur in the heat exchanger channels. This differs from continuously generating subcooled water from high-purity water. In high-purity water, at a certain subcooling degree, the ice embryo size exceeds a critical value, and the total free energy decreases as the ice embryo size increases, leading to the formation of ice nuclei. The formation of ice is always accompanied by the growth of ice nuclei.

[0104] Figure 6 (a) and Figure 6 Figure (b) presents the experimental results of the supercooled water reaching -3.8℃ instantaneously after the experimental conditions were adjusted, and the results of maintaining an average supercooling of 2.8K for 108 minutes.

[0105] When the temperature of tap water is T 2,in The temperature of the coolant is 3.1℃, and the flow rate q2 is 1.24 L / min flowing into the heat exchanger; the temperature of the defreezing fluid T is... 1,in When the temperature was adjusted to -8.1℃ and the flow rate q1 was 1.78 L / min entering the compact heat exchanger 1, the inlet and outlet temperatures ΔT2 changed by 6.9 K, and the minimum supercooling degree of the supercooled water was 3.8 K. This result is superior to the experimental results of 3.8 K change in inlet and outlet temperatures ΔT2 and 3.3 K obtained by experimenting with pure water, compared with the results in Kaiyang, Q., Yi, J., 2002. High-performance continuous ice-making system with supercooled water. Acta Solar Energy. 2002(03).

[0106] And when the temperature of tap water T 2,in The temperature of the coolant is 3.2℃, and the flow rate q2 is 1.18 L / min flowing into the heat exchanger; the temperature of the defreezing fluid is T. 1,inWhen the temperature was adjusted to -6.8℃ and the flow rate q1 was 1.82 L / min entering the compact heat exchanger 1, the change in the inlet and outlet temperatures of the tap water ΔT2 was 6.0 K, and the subcooled water at an average temperature of -2.8℃ lasted for 108 min. This result is comparable to an experiment using tap water, where the change in inlet and outlet temperatures ΔT2 was only 2.5 K, and the subcooling degree was 2.0 K.

[0107] Compared to the literature Takahiro, O., Ikuhiro, Y., 2016. Ice making system using supercooled water and ice making method using supercooled water. Patent Gazette. JP 6028248B1 2016.1, which has a duration t of 9h, this invention has a significant advantage in terms of the change in tap water inlet and outlet temperature ΔT2 and the achievement of supercooling degree, although the duration t is not as good as that literature. Table 3 Explanation of symbols used in this invention

[0108]

[0109] Please refer to Figure 2 As shown, the present invention also provides an ice-making system 200, including the above-described supercooled water preparation system 100 and an ice-making device located at the outlet of a compact heat exchanger 1. The supercooled water produced by the above-described supercooled water preparation system 100 and its method is in an unstable state and forms ice crystals / ice particles when subjected to minor external stimuli.

[0110] In one embodiment, the ice-making device is an ice bucket or ice pool 4. After the supercooled water drips into the ice bucket or ice pool 4, it impacts the wall and turns into ice crystals / ice particles. The ice bucket or ice pool 4 is located below the water channel outlet of the compact heat exchanger 1.

[0111] Ideally, the cooling water flowing out of the compact heat exchanger 1 has reached the target supercooling degree and, after dripping into the ice bucket, it impacts the wall of the ice bucket and turns into ice crystals / ice particles. However, in the initial stage of operation of the supercooling water preparation system 100, the water flowing out of the compact heat exchanger 1 is not sufficiently supercooled, and some cold water will remain in the ice bucket. Alternatively, during the process of preparing cooling water, some ice crystals / ice particles will melt into water.

[0112] To drain the water from the ice bucket and prevent it from affecting ice crystals / ice particles, a drain outlet or drain valve can be installed on the ice bucket to drain the cold water as needed. Preferably, this portion of the cold water is recycled to avoid waste. The water flow system 3 of the present invention also includes a return pipe connecting the ice bucket and the second thermostat 31, and a return water pump 5 connected to the return pipe, for returning the cold water in the ice bucket to the second thermostat 31 for repeated recycling and continued participation in the preparation of cooling water, without causing waste of water and cooling capacity.

[0113] Experiments have shown that at supercooling levels of 3K and above, ice crystals form more easily and ice slurry accumulates faster. The greater the supercooling, the easier it is for ice to form, and the longer the time, the more ice is formed.

[0114] The present invention also provides an ice-making method, wherein the above-mentioned supercooled water is formed into ice by means of the ice-making device, and the ice includes, but is not limited to, ice crystals, ice particles, and ice blocks.

[0115] It is feasible to continuously generate supercooled water using tap water, and the resulting ice or ice slurry can be directly used in food engineering, indoor snowmaking, ice storage and other fields.

[0116] In summary, the supercooling water preparation system 100 and its preparation method of the present invention continuously generate supercooling water by exchanging heat between tap water and antifreeze using a compact heat exchanger 1. Compared with other types of heat exchangers, the inlet water temperature T is higher. 2,in Higher supercooling is achieved with lower supercooling, resulting in a longer continuous generation time (t) for lower supercooling. Furthermore, designs such as shortening channel length, eliminating channel shape variations, and increasing the number of channels can achieve even greater supercooling.

[0117] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0118] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A supercooled water preparation system, comprising an antifreeze flow system, a water flow system, and a control system; characterized in that, The antifreeze flow system is connected by pipelines to form a circulation loop, including a first thermostatic device, a first water pump, and a compact heat exchanger. The compact heat exchanger includes several water channel plates and several antifreeze channel plates, which are alternately stacked to form alternating water channels and antifreeze channels. Each of the water channel plates and antifreeze channel plates is provided with several microstructures, which are located within the water channels and antifreeze channels. The water flow system includes, via pipes, a second thermostatic device connected to a water source and controlling the water temperature, a second water pump, and the compact heat exchanger; The control system is communicatively connected to the first thermostatic device, the first water pump, the second thermostatic device, and the second water pump. The control system includes a first inlet temperature sensor connected to the inlet of the antifreeze channel, a first outlet temperature sensor connected to the outlet of the antifreeze channel, a first flow meter and a first pressure gauge connected to the antifreeze flow system, a second inlet temperature sensor connected to the inlet of the water channel, a second outlet temperature sensor connected to the outlet of the water channel, and a second flow meter and a second pressure gauge connected to the water flow system. Both the water channel plate and the antifreeze channel plate include a heat exchange zone, an inlet and an outlet communicating with the heat exchange zone, and a frame surrounding the heat exchange zone. The microstructure is located within the channel formed by the heat exchange zone. The heat exchange zone is divided into an inlet zone, a transition zone, a turbulent zone, and an outlet zone. In the turbulent zone, the flow direction of the water is opposite to that of the antifreeze. The hydraulic equivalent diameter of the water channel and the antifreeze channel is no greater than 0.4 mm, and the length of the water channel and the antifreeze channel is no greater than 50 mm. The compact microstructure also includes thermal insulation layers located at both ends of the stacking direction; The compact heat exchanger also includes a diffuser structure connected to the outlet of the water channel.

2. The supercooled water preparation system according to claim 1, characterized in that: The hydraulic equivalent diameter of the water channel and the antifreeze channel is 0.32 mm, and the length of the water channel and the antifreeze channel is 25 mm.

3. The supercooled water preparation system according to claim 1, characterized in that: Water flows through the water channel at a flow rate of 0.017 l / s to 0.032 l / s, and the time spent in the compact heat exchanger is 0.038 s to 0.072 s.

4. The supercooling water preparation system according to claim 1, characterized in that, The microstructures of the inlet and outlet zones are longitudinally elongated, the microstructures of the transition zone are circular, and the microstructures of the turbulent zone are distributed along a sine curve, with two microstructures forming adjacent crest-trough shapes when connected. The density of the microstructures in the inlet and outlet zones is less than that in the transition zone, which is less than that in the turbulent zone. The two transition zones are located on opposite sides of the turbulent zone, and the inlet and outlet zones are located on the same side of the two transition zones. The arrangement direction of the inlet and transition zones is different from that of the transition zones and the heat exchange zone. The channel has two bends.

5. The supercooling water preparation system according to claim 1, characterized in that, The diffuser structure is trumpet-shaped or cone-shaped.

6. The supercooled water preparation system according to claim 5, characterized in that: The diffuser structure is a diffuser tube.

7. The supercooling water preparation system according to claim 1, characterized in that, The water flow system further includes: a first secondary filter connected between the first thermostat and the compact heat exchanger, and / or a second filter connected between the second thermostat and the compact heat exchanger.

8. The supercooling water preparation system according to claim 7, characterized in that, The first filter is a 400-mesh metal mesh, and the second filter is a 400-mesh metal mesh.

9. The supercooling water preparation system according to claim 7, characterized in that, The first thermostatic device, the first ball valve, the first water pump, the first filter, the first flow meter, the first pressure gauge, the first inlet temperature sensor, the antifreeze channel, and the first outlet temperature sensor are connected in sequence to form a circulation loop, thus forming the flow path of the antifreeze. The second thermostat, the second ball valve, the second water pump, the second filter, the second flow meter, the second pressure gauge, the second inlet temperature sensor, the water channel, and the second outlet temperature sensor are connected in sequence to form a water flow path.

10. An ice-making system, characterized in that, Includes the subcooled water ice-making system as described in any one of claims 1 to 9, and the ice-making device located at the outlet of the compact heat exchanger.

11. The ice-making system according to claim 10, characterized in that, The ice-making device is an ice bucket or ice pool.

12. The ice-making system according to claim 11, characterized in that, The ice-making system also includes a discharge port or discharge valve that communicates with the bottom of the ice bucket; Alternatively, the ice-making system may further include a return pipe connecting the ice bucket or ice pool to the second constant temperature device, and a return water pump connected to the return pipe.

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