A composite phase change cold storage material for refrigerators and its preparation method

Abstract

This invention relates to a composite phase change cold storage material for refrigerators and its preparation method. To address the technical shortcomings of existing cold storage materials, such as strong corrosivity, insufficient energy storage, and severe phase separation, this invention employs a method of mixing organic phase change materials with water to obtain a composite phase change material. This material contains no inorganic salts, thus solving the corrosion problem on metal packaging materials such as stainless steel and aluminum alloys. During material cycling, there is no phase separation problem, resulting in a long service life. It also solves the problem of low unit cold storage energy when using organic materials such as fatty acids, fatty alcohols, and alkanes, as well as the safety risks of low unit cold storage energy and potential high-temperature flammability associated with organic phase change cold storage materials.

Description

Technical Field

[0001] This invention relates to the field of phase change cold storage, and in particular to a cold storage material for refrigerators and its preparation method. Technical Field

[0002] With the improvement of people's living standards and the increasing demand for cold chain storage, household refrigerators and commercial refrigeration and freezing equipment have become essential appliances in daily life and food preservation. Currently, traditional refrigerators rely on frequent compressor starts and stops to regulate the internal temperature, which suffers from problems such as large temperature fluctuations, low temperature control accuracy, high energy consumption during compressor start-stop, and rapid temperature rise after power outages. Furthermore, when the refrigerator door is opened to take out or put in items, a large amount of hot outside air enters, easily causing a sudden rise in internal temperature, shortening the food preservation period, increasing the load on the refrigeration system, and exacerbating energy waste. Existing phase change cold storage products mostly use inorganic salt solutions, mixtures of organic substances, or composites of organic and inorganic substances to achieve phase change cold storage.

[0003] Existing refrigerators rely on frequent compressor starts and stops for temperature control. This not only results in high energy consumption during start-stop cycles, poor overall energy efficiency, and loud operating noise, but also leads to significant temperature fluctuations within the refrigerator, severely impacting the storage quality and shelf life of food. To improve refrigerator temperature control stability and further enhance refrigeration system efficiency, the industry is increasingly adopting phase change energy storage materials to achieve cold storage and stable release. These materials leverage the advantages of high latent heat of phase change and excellent temperature control to reduce internal temperature fluctuations and minimize frequent compressor starts and stops, thereby achieving the goals of improved preservation, enhanced quality, and energy savings.

[0004] Patent CN202510856380.7 reports the use of sodium formate and potassium sulfate aqueous solution as the main cold storage material; patent CN202410896491.6 reports the use of ammonium chloride and polyethylene glycol aqueous solution as the main cold storage material. Both use inorganic salt-based phase change materials, and their encapsulation materials, made of traditional stainless steel and aluminum alloys, suffer from corrosion and phase separation issues, affecting material lifespan and hindering application and promotion. Patent CN202410505551.7 reports the use of a mixture of octanoic acid and lauric acid to achieve cold storage, while patent CN202410929236.7 reports the preparation of a phase change cold storage material using a mixture of alkanes and fatty alcohols. However, while the use of organic phase change materials extends corrosion and lifespan, the low energy storage per unit, high cost, and flammability further limit their application development.

[0005] To address the technical challenges of existing cold storage materials, such as high corrosivity, insufficient energy storage, and severe phase separation, a special phase change cold storage material for refrigerators with suitable phase change temperature, high latent heat of cold storage, and excellent cycle stability is to be developed. This material has significant practical implications and application value for achieving constant temperature control inside the refrigerator, extending the cold preservation time during power outages, reducing overall energy consumption, and improving the quality of food preservation. Summary of the Invention

[0006] This invention uses a method of mixing organic phase change materials with water to obtain a composite phase change material. This material contains no inorganic salts, thus solving the problem of corrosion on metal packaging materials such as stainless steel and aluminum alloys. During the material cycle, there is no phase separation problem, resulting in a long service life. It also solves the problem of low unit cold storage energy when using organic materials such as organic fatty acids, fatty alcohols, and alkanes. Furthermore, it addresses the safety risks of low unit cold storage energy and potential high-temperature flammability associated with using organic phase change cold storage materials.

[0007] This invention first provides a composite phase change cold storage material for refrigerators, the material comprising: 1. The main materials are 1,6-hexanediol, neopentyl glycol, or imidazole, wherein the solid-liquid phase transition point of 1,6-hexanediol is 43℃, that of neopentyl glycol is 42℃, and that of imidazole is 88~91℃. All three can be used individually as phase change materials: 10~40 wt%. 2. Thickener: One or two of sodium carboxymethyl cellulose, sodium alginate, sodium polyacrylate, and polyvinyl alcohol, in a content of 0.1~1 wt%; 3. The balance is deionized water, and the solid-liquid phase transition point of water is 0℃; the total mass percentage of all components is 100%.

[0008] This invention also provides a method for preparing a composite phase change cold storage material for refrigerators, the method comprising the following steps: Step 1: Add the weighed deionized water or distilled water to the reaction vessel and start stirring; Step 2: Add the thickener slowly in batches to the water from Step 1, stirring to form a homogeneous phase; Step 3: Add the main material to the solution from step 2 in batches, turn on the heating, set the temperature to 25-70℃, stir until it becomes homogeneous, then stop stirring to obtain the composite phase change material.

[0009] Compared with existing technologies, the inorganic-organic composite material prepared by this method avoids phase separation, has a long cycle life, does not corrode metal materials such as aluminum alloys and stainless steel, has high energy storage, and has a phase change temperature of about -6℃ to -3℃, making it more suitable for the application and promotion of refrigeration equipment such as refrigerators. Attached Figure Description

[0010] Figure 1 The time-temperature change curve for Example 1; Figure 2 The time-temperature change curve for Example 2; Figure 3 The time-temperature change curve for Example 3; Figure 4The time-temperature change curve for Example 4; Figure 5 The time-temperature change curve for Example 5; Figure 6 The time-temperature change curve for Example 6; Figure 7 The time-temperature change curve for Example 7; Figure 8 The time-temperature change curve for Example 8; Figure 9 The time-temperature change curve for Example 9; Figure 10 The time-temperature change curve for Example 10; Figure 11 This is the time-temperature change curve for Example 10. Detailed Implementation

[0011] Example 1 (1) First step: Add 890 kg of deionized water or distilled water to the reaction vessel and start stirring; (2) Second step: Slowly add 5 kg of sodium carboxymethyl cellulose and 5 kg of polyvinyl alcohol to the water in the first step in batches, and stir to form a homogeneous phase; (3) Third step: Add 100 kg of 1,6-hexanediol in batches to the solution in the second step, turn on the heating, maintain the temperature at 25℃, stir until it becomes homogeneous, then stop stirring, discharge the material, and obtain the composite phase change material. The initial cooling temperature of the phase change material is -0.58℃, and the heating temperature is -3.3~-0.89℃. Figure 1 The phase transition enthalpy is 287 KJ / Kg. When aluminum alloy 5052 is placed in the composite material and kept at a constant temperature of 50℃ for 14 days, the corrosion mass loss is <0.14%. After 1000 cycles at -30℃ to 40℃, the enthalpy decay rate is <1%.

[0012] Example 2 (1) Step 1: Add 799 kg of deionized water or distilled water to the reaction vessel and start stirring; (2) Second step: Slowly add 0.5 kg of sodium carboxymethyl cellulose and 0.5 kg of sodium polyacrylate to the water in the first step in batches, and stir to form a homogeneous phase; (3) Third step: Add 200 kg of 1,6-hexanediol in batches to the solution from the second step, turn on the heater, maintain the temperature at 40℃, stir until homogeneous, then stop stirring and heating to obtain the composite phase change material. The initial cooling temperature of the phase change material is -0.58℃, the heating temperature is -3.3~-0.89℃, and the phase change enthalpy is 287 KJ / Kg. Figure 2When aluminum alloy 5052 is placed in the composite material and kept at a constant temperature of 50℃ for 14 days, the corrosion mass loss is <0.2%. After 1000 cycles at -30℃ to 40℃, the enthalpy decay rate is <1%.

[0013] Example 3 (1) Step 1: Add 695 kg of deionized water or distilled water to the reaction vessel and start stirring; (2) Second step: Slowly add 3 kg of sodium carboxymethyl cellulose and 2 kg of polyvinyl alcohol to the water in the first step in batches, and stir to form a homogeneous phase; (3) Third step: Add 300 kg of 1,6-hexanediol in batches to the solution from the second step, turn on the heater, maintain the temperature at 50°C, stir until a homogeneous phase is formed, then stop stirring and heating to obtain the composite phase change material. The cooling temperature of the composite phase change material is -4°C, and the heating temperature is -2.9°C. Figure 3 The phase change enthalpy is 231 KJ / Kg. When aluminum alloy 5052 is placed in the composite material and kept at a constant temperature of 50℃ for 14 days, the corrosion mass loss is <0.2%. After 1000 cycles at -30℃ to 40℃, the enthalpy decay rate is <1%.

[0014] Example 4 (1) Step 1: Add 592 kg of deionized water or distilled water to the reaction vessel and start stirring; (2) Second step: Add 4 kg of sodium alginate and 4 kg of sodium polyacrylate to the water in the first step in batches and stir to form a homogeneous phase; (3) Third step: Add 400 kg of 1,6-hexanediol in batches to the solution from the second step, turn on the heater, maintain the temperature at 50°C, stir until a homogeneous phase is formed, then stop stirring and heating, and discharge the material to obtain the composite phase change material. The initial cooling temperature of the phase change material is -3.3°C, and the heating temperature is -2.8°C. Figure 4 With a phase change enthalpy of 200 KJ / Kg, aluminum alloy 5052 was placed in the composite material and kept at a constant temperature of 50℃ for 14 days. The corrosion mass loss was <0.2%. After 1000 cycles at -30℃ to 40℃, the enthalpy decay rate was <1%.

[0015] Example 5 (1) First step: Add 890 kg of deionized water or distilled water to the reaction vessel and start stirring; (2) Second step: Slowly add 8 kg of sodium carboxymethyl cellulose and 2 kg of sodium polyacrylate to the water in the first step in batches, and stir to form a homogeneous phase; (3) Third step: Add 100 kg of neopentyl glycol to the solution in the second step in batches, turn on the heating, maintain the temperature at 40℃, stir until it becomes homogeneous, stop stirring, discharge the material, and obtain the composite phase change material. The cooling temperature of the composite phase change material is -1.1℃, and the heating temperature is -4.1~-2℃. Figure 5 The phase change enthalpy is 288 KJ / Kg. When aluminum alloy 5052 is placed in the composite material and kept at a constant temperature of 50℃ for 14 days, the corrosion mass loss is <0.2%. After 1000 cycles at -30℃ to 40℃, the enthalpy decay rate is <1%.

[0016] Example 6 (1) Step 1: Add 795 kg of deionized water or distilled water to the reaction vessel and start stirring; (2) Second step: Slowly add 2.5 kg of polyvinyl alcohol and 2.5 kg of sodium alginate to the water in the first step in batches, and stir to form a homogeneous phase; (3) Third step: Add 200 kg of neopentyl glycol to the solution from the second step in batches, turn on the heating, maintain the temperature at 40℃, stir until homogeneous, then stop stirring and heating, discharge the material to obtain the composite phase change material. The cooling temperature of the composite phase change material is -4 to -7℃, the heating temperature is -4.5℃, and the phase change enthalpy is 263 KJ / Kg. Figure 6 When aluminum alloy 5052 is placed in the composite material and kept at a constant temperature of 50℃ for 14 days, the corrosion mass loss is <0.2%. After 1000 cycles at -30℃ to 40℃, the enthalpy decay rate is <1%.

[0017] Example 7 (1) Step 1: Add 697 kg of deionized water or distilled water to the reaction vessel and start stirring; (2) Second step: Slowly add 2 kg of sodium alginate and 1 kg of sodium polyacrylate to the water in the first step in batches, and stir to form a homogeneous phase; (3) Third step: Add 300 kg of neopentyl glycol to the solution in the second step in batches, turn on the heating, maintain the temperature at 60℃, stir to form a homogeneous phase, then stop stirring and heating to obtain the composite phase change material. The cooling temperature of the phase change material is -3.1~-6℃, and the heating temperature is about -4.5℃. Figure 7 The phase change enthalpy is 232 KJ / Kg. When aluminum alloy 5052 is placed in the composite material and kept at a constant temperature of 50℃ for 14 days, the corrosion mass loss is <0.2%. After 1000 cycles at -30℃ to 40℃, the enthalpy decay rate is <1%.

[0018] Example 8 (1) First step: Add 890 kg of deionized water or distilled water to the reaction vessel and start stirring; (2) Second step: Slowly add 5 kg of sodium carboxymethyl cellulose and 5 kg of sodium alginate to the water in the first step in batches, and stir to form a homogeneous phase; (3) Third step: Add 100 kg of imidazole in batches to the solution in the second step, turn on the heating, maintain the temperature at 35℃, stir until it becomes homogeneous, then stop heating and stirring, discharge the material, and obtain the composite phase change material. The cooling temperature of the composite phase change material is -2.8℃ to -6.8℃, and the heating temperature is -6℃ to -3℃. Figure 8 The phase change enthalpy is 287 KJ / Kg. When aluminum alloy 5052 is placed in the composite phase change material and kept at a constant temperature of 50℃ for 14 days, the mass loss before and after corrosion is <0.4%. After 1000 cycles at -30℃ to 40℃, the enthalpy decay rate is <1%.

[0019] Example 9 (1) Step 1: Add 797 kg of deionized water or distilled water to the reaction vessel and start stirring; (2) Second step: Slowly add 1.5 kg of sodium carboxymethyl cellulose and 1.5 kg of sodium polyacrylate to the water in the first step in batches, and stir to form a homogeneous phase; (3) Third step: Add 200 kg of imidazole in batches to the solution from the second step, turn on the heater, maintain the temperature at 40℃, stir until homogeneous, then stop stirring and heating, discharge the material to obtain the composite phase change material. The cooling temperature of the composite phase change material is -3 to -7℃, the heating temperature is -5.9℃, and the phase change enthalpy is 265 KJ / Kg. Figure 9 When aluminum alloy 5052 is placed in the composite material and kept at a constant temperature of 50℃ for 14 days, the corrosion mass loss is <0.2%. After 1000 cycles at -30℃ to 40℃, the enthalpy decay rate is <1%.

[0020] Example 10 (1) Step 1: Add 693 kg of deionized water or distilled water to the reaction vessel and start stirring; (2) Second step: Slowly add 4 kg of sodium alginate and 3 kg of polyvinyl alcohol to the water in the first step in batches, and stir to form a homogeneous phase; (3) Third step: Add 300 kg of imidazole in batches to the solution from the second step, turn on the heater, maintain the temperature at 45°C, stir until a homogeneous phase is formed, then stop stirring and heating, discharge the material, and obtain the composite phase change material. The initial cooling temperature of the composite phase change material is -5.7~-6.8°C, and the heating temperature is approximately -6.1°C. Figure 10 The phase transition enthalpy is 229 KJ / Kg. When aluminum alloy 5052 is placed in the composite material and kept at a constant temperature of 50℃ for 14 days, the corrosion mass loss is <0.2%. After 1000 cycles at -30℃ to 40℃, the enthalpy decay rate is <1%.

[0021] Example 11 (1) Step 1: Add 599 kg of deionized water or distilled water to the reaction vessel and start stirring; (2) Second step: Slowly add 1 kg of sodium polyacrylate to the water from the first step in batches and stir to form a homogeneous phase; (3) Third step: Add 400 kg of imidazole in batches to the solution in the second step, turn on the heater, maintain the temperature at 55℃, stir to form a homogeneous phase, then stop stirring and heating, discharge the material, and obtain the composite phase change material. The cooling temperature of the composite phase change material is -6.6~-7.5℃, and the heating temperature is about -6.3℃. Figure 11 The phase change enthalpy is 202 KJ / Kg. When aluminum alloy 5052 is placed in the composite material and kept at a constant temperature of 50℃ for 14 days, the corrosion mass loss is <0.2%. After 1000 cycles at -30℃ to 40℃, the enthalpy decay rate is <1%.

[0022] The composite phase change cold storage materials obtained in Examples 1-11 were tested. The corrosion test procedure was as follows: Before the test, aluminum alloy sheet 5052 (length × width × height 50mm*25mm*1mm) was cleaned with water and placed in a beaker containing ethanol. The beaker was placed in an ultrasonic device and ultrasonically cleaned for 10 minutes. After rinsing with water, the aluminum alloy sheet was placed in a beaker of deionized water and ultrasonically cleaned for another 10 minutes. After drying at 40℃ for 2 hours, it was removed, weighed, and placed in a blue-capped temperature-resistant and pressure-resistant glass bottle containing the above-mentioned phase change cold storage liquid. The cold storage liquid was ensured to completely submerge the aluminum alloy sheet. The glass bottle was then placed in a constant temperature oil bath and heated at 50℃ for 14 days. After the corrosion test, the sheet was cleaned and dried according to the above steps, weighed, and the corrosion mass loss was calculated (Table 1).

[0023] .

[0024] Life cycle test: Take 25 mL of cold storage phase change material, pour it into a thickened pressure-resistant glass tube, place it in a test tube rack, and put it in a high and low temperature cycling device. Set the temperature program to -30℃~40℃ and cycle 1000 times. After the cycle, calculate the enthalpy decay rate.

Claims

1. A composite phase change cold storage material for refrigerators, characterized in that, The materials mentioned include: Main ingredients: 1,6-hexanediol, neopentyl glycol and / or imidazole, 10~40 wt%; Thickener: one or more of sodium carboxymethyl cellulose, sodium alginate, sodium polyacrylate, and polyvinyl alcohol, 0.1~1 wt%; The remainder is water.

2. A composite phase change cold storage material for refrigerators, characterized in that, The water mentioned is deionized water or distilled water.

3. A method for preparing a composite phase change cold storage material for refrigerators as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: Step 1: Add deionized water or distilled water to the reaction vessel and start stirring; Step 2: Add the thickener slowly in batches to the water from Step 1, stirring to form a homogeneous phase; Step 3: Add the main material to the solution from step 2 in batches, turn on the heating, set the temperature to 25-70℃, stir until it becomes homogeneous, then stop stirring to obtain the composite phase change material.

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