Compositions, phase change materials, and methods of making and using the same

Abstract

The application discloses a composition, a phase change material and a preparation method and application thereof, and the composition comprises 35-65 parts by weight of a first organic phase change material, 35-65 parts by weight of a second organic phase change material, 0.1-3 parts by weight of a heat enthalpy enhancer and 1-3 parts by weight of a thickening agent. Therefore, the components are mutually synergistic and compatible, and can be used to prepare the phase change material with high heat enthalpy, low supercooling degree, no phase separation, good stability, a phase change temperature of 28-32 DEG C and being suitable for a multi-connected heat storage defrosting system.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to compositions, phase change materials, their preparation methods and applications. Background Technology

[0002] In low-temperature and humid environments, the outdoor unit of a multi-split air conditioner is prone to frost formation, with a large amount of frost covering the heat exchanger fins. This increases the thermal resistance between the heat exchanger and the air, leading to a decrease in heating performance and thus affecting the actual heating capacity of the multi-split air conditioner.

[0003] Currently, most defrosting methods use reverse circulation defrosting. However, this defrosting method causes a significant drop in indoor temperature, resulting in poor indoor comfort. It also leads to slow pressure differential establishment after defrosting, slower heating speed, longer defrosting time, and poor system reliability. Therefore, new defrosting methods are needed for multi-split air conditioning systems.

[0004] Phase change energy storage is a new type of energy storage technology that uses the two-state change of materials to store latent heat. It has advantages such as high energy storage density and almost constant phase change temperature. Therefore, phase change energy storage devices can be introduced into multi-split air conditioning systems to use phase change for heat storage and defrosting.

[0005] Phase change materials need to be placed in the heat storage defrosting module of multi-split air conditioners. However, existing phase change materials have problems such as low enthalpy, high subcooling, phase separation, and easy corrosion. Summary of the Invention

[0006] The present invention aims to improve at least one of the above-mentioned technical problems to at least some extent.

[0007] This invention provides a composition comprising: 35-65 parts by weight of a first organic phase change material, 35-65 parts by weight of a second organic phase change material, 0.1-3 parts by weight of an enthalpy enhancer, and 1-3 parts by weight of a thickener. Thus, the components synergistically complement each other, enabling the preparation of a phase change material with high enthalpy, low supercooling, no phase separation, good stability, a phase change temperature of 28°C to 32°C, and suitability for multi-split air conditioning systems.

[0008] According to an embodiment of the present invention, the first organic phase change material is different from the second organic phase change material and is independently selected from polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000, and polyethylene glycol 2000.

[0009] According to an embodiment of the present invention, the enthalpy enhancer comprises a fatty acid, wherein the fatty acid comprises at least one of palmitic acid, stearic acid, capric acid, linolenic acid, and linoleic acid.

[0010] According to embodiments of the present invention, the thickener includes at least one of triethanolamine, carbomer, polyvinyl alcohol, fumed silica, hollow glass microspheres, glass fiber, and polyurethane foam.

[0011] This invention also provides a method for preparing phase change materials, the method comprising: mixing the components of the composition described above to obtain the phase change material. That is, the composition described above can be used as a raw material to prepare phase change materials. Furthermore, this method has the advantages of simple operation and low production cost.

[0012] According to an embodiment of the present invention, the method includes: heating and melting a first organic phase change material and a second organic phase change material respectively; mixing the melted first organic phase change material and the melted second organic phase change material to obtain a first mixture; mixing the first mixture with an enthalpy enhancer to obtain a second mixture; and mixing the second mixture with a thickener to obtain a phase change material.

[0013] According to an embodiment of the present invention, after the second mixture is mixed with the thickener, the method further includes: subjecting the mixture of the second mixture and the thickener to vacuum drying, and then naturally cooling it to room temperature after the vacuum drying is completed to obtain a phase change material; the vacuum drying is carried out in a vacuum drying oven, the vacuum degree of the vacuum drying is (-1.5) to (-0.5) bar, the temperature of the vacuum drying is 40 to 60°C, and the time of the vacuum drying is 20 to 40 minutes.

[0014] The present invention also provides phase change materials prepared by the methods described above.

[0015] According to an embodiment of the present invention, the phase change temperature of the phase change material is 28-32℃; the phase change enthalpy of the phase change material is ≥130J / g; and the supercooling of the phase change material is ≤2℃.

[0016] This invention also provides the application of the phase change materials described above in multi-split air conditioning systems. Attached Figure Description

[0017] Figure 1 This is the time-temperature curve of the phase change material prepared in Example 1;

[0018] Figure 2 The DSC curve of the phase change material prepared in Example 1;

[0019] Figure 3 This is the time-temperature curve of the phase change material prepared in Example 2;

[0020] Figure 4 The DSC curve of the phase change material prepared in Example 2;

[0021] Figure 5 This is the time-temperature curve of the phase change material prepared in Example 3;

[0022] Figure 6 The DSC curve of the phase change material prepared in Example 3;

[0023] Figure 7 This is the time-temperature curve of the phase change material prepared in Example 4;

[0024] Figure 8 The DSC curve of the phase change material prepared in Example 4;

[0025] Figure 9 This is the time-temperature curve of the phase change material prepared in Example 5;

[0026] Figure 10 The DSC curve of the phase change material prepared in Example 5;

[0027] Figure 11 The time-temperature curves of the phase change material prepared in Comparative Example 1 are shown.

[0028] Figure 12 The DSC curve of the phase change material prepared in Comparative Example 1;

[0029] Figure 13 The time-temperature curves of the phase change material prepared in Comparative Example 2 are shown.

[0030] Figure 14 The DSC curve of the phase change material prepared in Comparative Example 2;

[0031] Figure 15 The time-temperature curves of the phase change material prepared in Comparative Example 3 are shown.

[0032] Figure 16 The DSC curve of the phase change material prepared in Comparative Example 3 is shown below.

[0033] Figure 17 These are photos of three groups of aluminum sheet samples after a 1000-hour corrosion test;

[0034] Figure 18 It is the thermogravimetric (TGA) curve of the phase change material. Detailed Implementation

[0035] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0036] This invention provides a composition comprising: 35-65 parts by weight of a first organic phase change material, 35-65 parts by weight of a second organic phase change material, 0.1-3 parts by weight of an enthalpy enhancer, and 1-3 parts by weight of a thickener. Thus, the components synergistically complement each other, enabling the preparation of a phase change material with high enthalpy, low supercooling, no phase separation, good stability, a phase change temperature of 28°C to 32°C, and suitability for multi-split air conditioning systems.

[0037] Specifically, the phase change material prepared from the above composition has a phase change temperature of 28°C to 32°C, which matches the temperature of heat storage defrosting in multi-split air conditioners (28°C to 32°C). Therefore, the phase change material of the present invention is suitable for heat storage defrosting in multi-split air conditioners and has the effect of defrosting in a short time.

[0038] The composition contains 35-65 parts by weight of the first organic phase change material (e.g., 35 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 55 parts by weight, 60 parts by weight, and 65 parts by weight), 35-65 parts by weight of the second organic phase change material (e.g., 35 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 55 parts by weight, 60 parts by weight, and 65 parts by weight), 0.1-3 parts by weight of the enthalpy enhancer (e.g., 0.1 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, and 3 parts by weight), and 1-3 parts by weight of the thickener (e.g., 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, and 3 parts by weight). The components within the above-mentioned content range work together to make the phase change material have a phase change temperature of 28°C to 32°C and a high enthalpy. The first and second organic phase change materials (PCCs) form the main system of the PCC, ensuring the phase change temperature and latent heat of phase change. If the content of the first and second organic PCCs is too low or too high, the phase change temperature of the PCC will change, thus failing to meet the defrosting temperature range (28–32°C) of the heat storage defrosting material. If the content of the enthalpy enhancer is too low, it will not significantly enhance the enthalpy of the PCC and will also affect the phase change temperature; if the content of the enthalpy enhancer is too high, it will affect both the phase change temperature and enthalpy value of the PCC. If the content of the thickener is too low, the PCC will have poor gelling properties and high fluidity; if the content of the thickener is too high, the PCC is prone to precipitation, affecting the cycle stability of the PCC.

[0039] According to embodiments of the present invention, the first organic phase change material is different from the second organic phase change material, and is independently selected from polyethylene glycol 200 (PEG200), polyethylene glycol 400 (PEG400), polyethylene glycol 600 (PEG600), polyethylene glycol 800 (PEG800), polyethylene glycol 1000 (PEG1000), and polyethylene glycol 2000 (PEG2000). The phase change temperature of polyethylene glycol (PEG) changes with its molecular weight, and PEG has characteristics such as high latent heat of phase change, low thermal hysteresis, non-toxicity, and non-irritation. By selecting polyethylene glycols with different molecular weights as the first and second organic phase change materials, the phase change temperature of the phase change materials can be adjusted.

[0040] According to some specific embodiments of the present invention, the first organic phase change material can be polyethylene glycol 800, and the second organic phase change material can be polyethylene glycol 1000.

[0041] According to an embodiment of the present invention, the enthalpy enhancer comprises a fatty acid, which includes at least one of palmitic acid (HEA), stearic acid (SEA), decanoic acid (DAA), caprylic acid (CAA), linolenic acid (LOA), and linoleic acid (LEA). Thus, by adding the enthalpy enhancer, the enthalpy of the phase change material can be effectively increased. Furthermore, the above-mentioned materials have the advantages of being widely available and inexpensive.

[0042] According to embodiments of the present invention, the thickener comprises at least one of triethanolamine, carbomer, polyvinyl alcohol, fumed silica, hollow glass microspheres, glass fiber, and polyurethane foam. Therefore, by adding a thickener, the phase change material can be gelled, phase separation can be avoided, and the cycling stability of the phase change material can be improved.

[0043] According to some specific embodiments of the present invention, the thickener may be triethanolamine and carbomer, or, in other embodiments of the present invention, the thickener may be polyvinyl alcohol.

[0044] This invention also provides a method for preparing a phase change material, the method comprising: mixing the components of the composition described above to obtain the phase change material. That is, the composition described above can be used as a raw material to prepare a phase change material. Furthermore, in this method, the types and contents of the components in the composition are the same as those in the composition described above, and will not be repeated here.

[0045] According to an embodiment of the present invention, the method includes:

[0046] S100, The first organic phase change material and the second organic phase change material are heated and melted respectively;

[0047] By heating and melting the first organic phase change material and the second organic phase change material, it is beneficial to achieve a thorough mixing of the first and second organic phase change materials.

[0048] S200: Mix the melted first organic phase change material and the melted second organic phase change material to obtain a first mixture.

[0049] In some embodiments of the present invention, the molten first organic phase change material and the molten second organic phase change material can be mixed in a certain proportion by magnetic stirring and ultrasonic treatment to obtain a first mixture.

[0050] S300. The first mixture is mixed with the enthalpy enhancer to obtain a second mixture;

[0051] Adding an enthalpy enhancer to the first mixture can enhance the enthalpy.

[0052] According to some embodiments of the present invention, in order to achieve uniform mixing, after adding an enthalpy enhancer to the first mixture, it can be initially dispersed by magnetic stirring and ultrasonic treatment, and then emulsified using a high-speed disperser to obtain a second mixture.

[0053] S400. The second mixture is mixed with a thickener to obtain a phase change material.

[0054] Adding a thickener to the second mixture facilitates gelation, prevents phase separation, reduces the decay of phase change enthalpy, and improves the cycle stability of the phase change material.

[0055] According to some embodiments of the present invention, after adding the thickener to the second mixture, the method further includes: using mechanical stirring to fully wet the thickener so that the second mixture and the thickener can be mixed evenly.

[0056] According to an embodiment of the present invention, after the second mixture is mixed with the thickener, the method further includes: subjecting the mixture of the second mixture and the thickener to vacuum drying, and then naturally cooling it to room temperature after the vacuum drying is completed to obtain a phase change material.

[0057] According to some embodiments of the present invention, the vacuum drying process is carried out in a vacuum drying chamber, wherein the vacuum degree of the vacuum drying process is (-1.5) to (-0.5) bar, the temperature of the vacuum drying process is 40 to 60°C, and the time of the vacuum drying process is 20 to 40 min.

[0058] Because thickener materials form a three-dimensional network structure, other components cannot fill the interior of the thickener if the bubbles are not removed. Vacuum drying can remove the air bubbles inside the thickener material during the gelation process, allowing other components to fill the interior of the thickener.

[0059] The present invention also provides phase change materials prepared by the methods described above.

[0060] According to an embodiment of the present invention, the phase change temperature of the phase change material is 28-32℃; the phase change enthalpy of the phase change material is ≥130J / g; and the supercooling of the phase change material is ≤2℃.

[0061] This invention also provides the application of the phase change materials described above in multi-split air conditioning systems.

[0062] Furthermore, the multi-split air conditioner includes a heat storage defrosting module containing phase change material. During heating, the multi-split air conditioner stores some of its heat energy in the heat storage defrosting module; during defrosting, the phase change material releases heat while maintaining heating operation to achieve defrosting, significantly reducing indoor temperature fluctuations and achieving rapid heating.

[0063] Specifically, the defrosting temperature in multi-split air conditioners is 28℃~32℃. If the phase change material's phase change temperature is too high, it will result in a low temperature difference during heat storage, leading to excessively long heat storage time. If the phase change material's phase change temperature is too low, it will cause insufficient defrosting power and excessively long defrosting time. The phase change material of this invention has a phase change temperature of 28℃~32℃, which matches the defrosting temperature (28℃~32℃) in multi-split air conditioners. Therefore, the phase change material of this invention is suitable for the defrosting module of multi-split air conditioners. Moreover, the phase change material of this invention has advantages such as high phase change enthalpy, high stability, no phase separation, and low subcooling, and has the prospect of commercial application.

[0064] When the phase change material of the present invention is used for defrosting in a multi-split air conditioning system, the material's heat storage time does not exceed 30 minutes and its heat release time is about 6 minutes, which can achieve the purpose of efficient defrosting. Specifically, the phase change material of the present invention can meet the heat storage requirements of a 12HP multi-split air conditioning system. The filling amount of the phase change material is relatively small, which is 22-25 kg.

[0065] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0066] Example 1

[0067] The phase change material used in the heat storage defrosting module is made from the following raw materials in the following proportions: 65 parts by weight of polyethylene glycol 800, 35 parts by weight of polyethylene glycol 1000, 0.1 parts by weight of octanoic acid and 2 parts by weight of polyvinyl alcohol.

[0068] The specific steps are as follows:

[0069] Step 1: Melt polyethylene glycol 800 and polyethylene glycol 1000 separately by heating.

[0070] Step 2: Mix the materials melted in Step 1 according to the specified proportions using magnetic stirring and ultrasonic treatment;

[0071] Step 3: Add octanoic acid to the mixed solution obtained in Step 2, perform initial dispersion by magnetic stirring and ultrasonic treatment, and then emulsify using a high-speed disperser to obtain a mixed solution;

[0072] Step 4: Add polyvinyl alcohol to the mixed solution obtained in Step 3, and then mechanically stir to fully wet the polyvinyl alcohol;

[0073] Step 5: Place the mixture from Step 4 into a vacuum drying oven for vacuum drying. The vacuum level during vacuum drying is -1 bar, the temperature is 50°C, and the drying time is 30 minutes. After vacuum drying, allow it to cool naturally to room temperature to obtain the phase change material.

[0074] The time-temperature curve of the phase change material prepared in Example 1 is shown below. Figure 1 As shown, by Figure 1 It can be seen that the phase change temperature of the phase change material in Example 1 is 28.9℃ and the supercooling is 0.05℃.

[0075] The DSC curve of the phase change material prepared in Example 1 is shown below. Figure 2 As shown, by Figure 2 It can be seen that the enthalpy value per unit mass of the phase change material in Example 1 is 132.08 J / g.

[0076] Example 2

[0077] The phase change material used in the heat storage defrosting module is made from the following raw materials in the following proportions: 50 parts by weight of polyethylene glycol 800, 50 parts by weight of polyethylene glycol 1000, 0.1 parts by weight of octanoic acid, and 2 parts by weight of polyvinyl alcohol.

[0078] The specific steps are as follows:

[0079] Step 1: Melt polyethylene glycol 800 and polyethylene glycol 1000 separately by heating.

[0080] Step 2: Mix the materials melted in Step 1 according to the specified proportions using magnetic stirring and ultrasonic treatment;

[0081] Step 3: Add octanoic acid to the mixed solution obtained in Step 2, perform initial dispersion by magnetic stirring and ultrasonic treatment, and then emulsify using a high-speed disperser to obtain a mixed solution;

[0082] Step 4: Add polyvinyl alcohol to the mixed solution obtained in Step 3, and then mechanically stir to fully wet the polyvinyl alcohol;

[0083] Step 5: Place the mixture from Step 4 into a vacuum drying oven for vacuum drying. The vacuum level during vacuum drying is -1 bar, the temperature is 50°C, and the drying time is 30 minutes. After vacuum drying, allow it to cool naturally to room temperature to obtain the phase change material.

[0084] The time-temperature curve of the phase change material prepared in Example 2 is shown below. Figure 3 As shown, by Figure 3 It can be seen that the phase change temperature of the phase change material in Example 2 is 30.6℃ and the supercooling degree is 0.93℃.

[0085] The DSC curve of the phase change material prepared in Example 2 is shown below. Figure 4 As shown, by Figure 4 It can be seen that the enthalpy value per unit mass of the phase change material in Example 2 is 134.99 J / g.

[0086] Example 3

[0087] The phase change material used in the heat storage defrosting module is made from the following raw materials: 35 parts by weight of polyethylene glycol 800, 65 parts by weight of polyethylene glycol 1000, 0.1 parts by weight of octanoic acid, and 2 parts by weight of polyvinyl alcohol.

[0088] The specific steps are as follows:

[0089] Step 1: Melt polyethylene glycol 800 and polyethylene glycol 1000 separately by heating.

[0090] Step 2: Mix the materials melted in Step 1 according to the specified proportions using magnetic stirring and ultrasonic treatment;

[0091] Step 3: Add octanoic acid to the mixed solution obtained in Step 2, perform initial dispersion by magnetic stirring and ultrasonic treatment, and then emulsify using a high-speed disperser to obtain a mixed solution;

[0092] Step 4: Add polyvinyl alcohol to the mixed solution obtained in Step 3, and then mechanically stir to fully wet the polyvinyl alcohol;

[0093] Step 5: Place the mixture from Step 4 into a vacuum drying oven for vacuum drying. The vacuum level during vacuum drying is -1 bar, the temperature is 50°C, and the drying time is 30 minutes. After vacuum drying, allow it to cool naturally to room temperature to obtain the phase change material.

[0094] The time-temperature curve of the phase change material prepared in Example 3 is shown below. Figure 5 As shown, by Figure 5 It can be seen that the phase change temperature of the phase change material in Example 3 is 30.7℃ and the supercooling degree is 1.21℃.

[0095] The DSC curve of the phase change material prepared in Example 3 is shown below. Figure 6 As shown, by Figure 6 It can be seen that the enthalpy value per unit mass of the phase change material in Example 3 is 134.07 J / g.

[0096] Example 4

[0097] The phase change material used in the heat storage defrosting module is made from the following raw materials in the following proportions: 65 parts by weight of polyethylene glycol 800, 35 parts by weight of polyethylene glycol 1000, 1.5 parts by weight of octanoic acid and 2 parts by weight of polyvinyl alcohol.

[0098] The specific steps are as follows:

[0099] Step 1: Melt polyethylene glycol 800 and polyethylene glycol 1000 separately by heating.

[0100] Step 2: Mix the materials melted in Step 1 according to the specified proportions using magnetic stirring and ultrasonic treatment;

[0101] Step 3: Add octanoic acid to the mixed solution obtained in Step 2, perform initial dispersion by magnetic stirring and ultrasonic treatment, and then emulsify using a high-speed disperser to obtain a mixed solution;

[0102] Step 4: Add polyvinyl alcohol to the mixed solution obtained in Step 3, and then mechanically stir to fully wet the polyvinyl alcohol;

[0103] Step 5: Place the mixture from Step 4 into a vacuum drying oven for vacuum drying. The vacuum level during vacuum drying is -1 bar, the temperature is 50°C, and the drying time is 30 minutes. After vacuum drying, allow it to cool naturally to room temperature to obtain the phase change material.

[0104] The time-temperature curve of the phase change material prepared in Example 4 is shown below. Figure 7 As shown, by Figure 7 It can be seen that the phase change temperature of the phase change material in Example 4 is 30.3℃ and the supercooling is 1.05℃.

[0105] The DSC curve of the phase change material prepared in Example 4 is shown below. Figure 8 As shown, by Figure 8 It can be seen that the enthalpy value per unit mass of the phase change material in Example 4 is 149.47 J / g.

[0106] Example 5

[0107] The phase change material used in the heat storage defrosting module is made from the following raw materials in the following proportions: 65 parts by weight of polyethylene glycol 800, 35 parts by weight of polyethylene glycol 1000, 3 parts by weight of octanoic acid and 2 parts by weight of polyvinyl alcohol.

[0108] The specific steps are as follows:

[0109] Step 1: Melt polyethylene glycol 800 and polyethylene glycol 1000 separately by heating.

[0110] Step 2: Mix the materials melted in Step 1 according to the specified proportions using magnetic stirring and ultrasonic treatment;

[0111] Step 3: Add octanoic acid to the mixed solution obtained in Step 2, perform initial dispersion by magnetic stirring and ultrasonic treatment, and then emulsify using a high-speed disperser to obtain a mixed solution;

[0112] Step 4: Add polyvinyl alcohol to the mixed solution obtained in Step 3, and then mechanically stir to fully wet the polyvinyl alcohol;

[0113] Step 5: Place the mixture from Step 4 into a vacuum drying oven for vacuum drying. The vacuum level during vacuum drying is -1 bar, the temperature is 50°C, and the drying time is 30 minutes. After vacuum drying, allow it to cool naturally to room temperature to obtain the phase change material.

[0114] The time-temperature curve of the phase change material prepared in Example 5 is shown below. Figure 9 As shown, by Figure 9 It can be seen that the phase change temperature of the phase change material in Example 5 is 29.1℃ and the supercooling degree is 0.98℃.

[0115] The DSC curve of the phase change material prepared in Example 5 is shown below. Figure 10 As shown, by Figure 10 It can be seen that the enthalpy value per unit mass of the phase change material in Example 5 is 135.24 J / g.

[0116] Comparative Example 1

[0117] The phase change material used in the heat storage defrosting module is made from the following raw materials in the following proportions: 70 parts by weight of polyethylene glycol 800, 30 parts by weight of polyethylene glycol 1000, 0.1 parts by weight of octanoic acid, and 2 parts by weight of polyvinyl alcohol.

[0118] The specific steps are as follows:

[0119] Step 1: Melt polyethylene glycol 800 and polyethylene glycol 1000 separately by heating.

[0120] Step 2: Mix the materials melted in Step 1 according to the specified proportions using magnetic stirring and ultrasonic treatment;

[0121] Step 3: Add octanoic acid to the mixed solution obtained in Step 2, perform initial dispersion by magnetic stirring and ultrasonic treatment, and then emulsify using a high-speed disperser to obtain a mixed solution;

[0122] Step 4: Add polyvinyl alcohol to the mixed solution obtained in Step 3, and then mechanically stir to fully wet the polyvinyl alcohol;

[0123] Step 5: Place the mixture from Step 4 into a vacuum drying oven for vacuum drying. The vacuum level during vacuum drying is -1 bar, the temperature is 50°C, and the drying time is 30 minutes. After vacuum drying, allow it to cool naturally to room temperature to obtain the phase change material.

[0124] The time-temperature curve of the phase change material prepared in Comparative Example 1 is shown below. Figure 11 As shown, by Figure 11 It can be seen that the phase change temperature of the phase change material in Comparative Example 1 is 27.12℃ and the supercooling is 0.96℃.

[0125] The DSC curve of the phase change material prepared in Comparative Example 1 is shown below. Figure 12 As shown, by Figure 12 It can be seen that the enthalpy per unit mass of the phase change material in Comparative Example 1 is 148.39 J / g.

[0126] Comparative Example 2

[0127] The phase change material used in the heat storage defrosting module is made from the following raw materials in weight percentages: 30 parts by weight of polyethylene glycol 800, 70 parts by weight of polyethylene glycol 1000, 0.1 parts by weight of octanoic acid, and 2 parts by weight of polyvinyl alcohol.

[0128] The specific steps are as follows:

[0129] Step 1: Melt polyethylene glycol 800 and polyethylene glycol 1000 separately by heating.

[0130] Step 2: Mix the materials melted in Step 1 according to the specified proportions using magnetic stirring and ultrasonic treatment;

[0131] Step 3: Add octanoic acid to the mixed solution obtained in Step 2, perform initial dispersion by magnetic stirring and ultrasonic treatment, and then emulsify using a high-speed disperser to obtain a mixed solution;

[0132] Step 4: Add polyvinyl alcohol to the mixed solution obtained in Step 3, and then mechanically stir to fully wet the polyvinyl alcohol;

[0133] Step 5: Place the mixture from Step 4 into a vacuum drying oven for vacuum drying. The vacuum level during vacuum drying is -1 bar, the temperature is 50°C, and the drying time is 30 minutes. After vacuum drying, allow it to cool naturally to room temperature to obtain the phase change material.

[0134] The time-temperature curve of the phase change material prepared in Comparative Example 2 is shown below. Figure 13 As shown, by Figure 13 It can be seen that the phase change temperature of the phase change material in Comparative Example 2 is 33.86℃ and the supercooling is 0.13℃.

[0135] The DSC curve of the phase change material prepared in Comparative Example 2 is shown below. Figure 14 As shown, by Figure 14 It can be seen that the enthalpy per unit mass of the phase change material in Comparative Example 2 is 132.18 J / g.

[0136] Comparative Example 3

[0137] The phase change material used in the heat storage defrosting module is made from the following raw materials in weight percentages: 65 parts by weight of polyethylene glycol 800, 35 parts by weight of polyethylene glycol 1000, 5 parts by weight of octanoic acid and 2 parts by weight of polyvinyl alcohol.

[0138] The specific steps are as follows:

[0139] Step 1: Melt polyethylene glycol 800 and polyethylene glycol 1000 separately by heating.

[0140] Step 2: Mix the materials melted in Step 1 according to the specified proportions using magnetic stirring and ultrasonic treatment;

[0141] Step 3: Add octanoic acid to the mixed solution obtained in Step 2, perform initial dispersion by magnetic stirring and ultrasonic treatment, and then emulsify using a high-speed disperser to obtain a mixed solution;

[0142] Step 4: Add polyvinyl alcohol to the mixed solution obtained in Step 3, and then mechanically stir to fully wet the polyvinyl alcohol;

[0143] Step 5: Place the mixture from Step 4 into a vacuum drying oven for vacuum drying. The vacuum level during vacuum drying is -1 bar, the temperature is 50°C, and the drying time is 30 minutes. After vacuum drying, allow it to cool naturally to room temperature to obtain the phase change material.

[0144] The time-temperature curve of the phase change material prepared in Comparative Example 3 is shown below. Figure 15 As shown, by Figure 15 It can be seen that the phase change temperature of the phase change material in Comparative Example 3 is 29.91℃ and the supercooling is 0.87℃.

[0145] The DSC curve of the phase change material prepared in Comparative Example 3 is shown below. Figure 16 As shown, by Figure 16 It can be seen that the enthalpy per unit mass of the phase change material in Comparative Example 3 is 117.78 J / g.

[0146] Performance testing

[0147] The phase change materials prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to performance tests, including phase change temperature, supercooling, corrosion performance, enthalpy per unit mass, and thermal stability.

[0148] The specific test results are shown in Table 1.

[0149] Table 1

[0150]

[0151]

[0152] The enthalpy of phase change per unit mass was measured using a differential scanning calorimeter (DSC). The testing method was as follows: endothermic and exothermic curves were obtained using DSC. 5 mg of phase change material was placed in a crucible, and the temperature was maintained between 0 and 50 °C at a heating rate of 5 °C / min. The area under the curve represents the enthalpy of phase change. The area under the upper curve in the DSC spectrum represents the enthalpy of phase change during solidification, while the area under the lower curve represents the enthalpy of phase change during melting. In this application, the enthalpy of phase change during melting in the lower part of the DSC spectrum is uniformly used as the benchmark for the enthalpy value.

[0153] The method for testing supercooling is as follows: 100g of phase change material is placed in an oven at 50℃, and a thermocouple is placed in the middle of the phase change material. The material is then allowed to cool naturally to 20℃. The time-temperature curve of the phase change material is obtained. The difference between the inflection point of the curve and the highest point after the temperature rise is the supercooling.

[0154] The method for testing phase change temperature is as follows: 100g of phase change material is placed in an oven at 50℃, and a thermocouple is placed in the middle of the phase change material. The material is then allowed to cool naturally to 20℃, and the time-temperature curve of the phase change material is obtained. The inflection point of the curve is the phase change temperature.

[0155] The corrosion test method is as follows:

[0156] 1. Sample preparation: Copper tubes, aluminum sheets, and 304 stainless steel; remove the oxide film from the sample surface with 2000# or higher grit sandpaper, ultrasonically clean with alcohol, and dry. Melt a quantity of the prepared phase change material.

[0157] 2. Testing equipment: electronic balance, EDX, 3D microscope, drying oven + glass cup (preferably oil bath + sealed test tube), ultrasonic cleaner, etc.

[0158] 3. Test method: The phase change material is placed in a glass cup or sealed test tube, and the sample is immersed in the phase change material. The temperature is 70°C. The sample is taken out, cleaned and weighed every 7 days. The surface smoothness and surface corrosion morphology of the sample are observed. The weight loss rate and corrosion depth are calculated to conduct a comprehensive evaluation of corrosion resistance.

[0159] After a 1000-hour corrosion test, the copper tubes, aluminum sheets, and 304 stainless steel samples of this invention still maintained a high degree of surface smoothness. There was no significant change in the sample surface after the corrosion test compared to before the test. (Reference) Figure 17 It can be seen that the three groups of aluminum sheet samples still have a high degree of smoothness after 1000h of corrosion test, indicating that the phase change material of the present invention is non-corrosive.

[0160] The thermal stability of the phase change material was tested using a thermogravimetric analyzer (TGA). The test method was as follows: 18.3125 mg of the phase change material was placed in a crucible, and the temperature was set between 25 and 200 °C at a heating rate of 10 °C / min. The weight of the material was then tested to determine whether it changed within the temperature range.

[0161] Depend on Figure 18 It can be seen that the weight of the phase change material does not change significantly with increasing temperature, indicating that the phase change material of the present invention has high thermal stability.

[0162] The phase change materials prepared by Examples 1-5 of this application have a phase change temperature of 28-32℃, a phase change enthalpy ≥130J / g, a supercooling ≤2℃, and exhibit no phase separation, good thermal stability (no decomposition at 200℃), and no corrosion to metals (corrosion test over 1000h). When the phase change materials prepared by Examples 1-5 are used for defrosting in multi-split air conditioning systems, the material's heat storage time does not exceed 30 minutes, and the heat release time is approximately 6 minutes, achieving efficient defrosting; and the indoor temperature remains stable. The above test results confirm that the phase change material of this invention can meet the heat storage and defrosting requirements of multi-split air conditioning systems.

[0163] In Comparative Examples 1 and 2, the content of the first organic phase change material was not within the range of 35-65 parts by weight, and the content of the second organic phase change material was also not within the range of 35-65 parts by weight. Furthermore, the temperature of the phase change materials in Comparative Examples 1 and 2 was not within the range of 28-32°C, resulting in poor defrosting performance. In Comparative Example 3, the content of the enthalpy enhancer was excessive, and the enthalpy of the phase change material was below 130 J / g, which could not meet the defrosting requirements of multi-split air conditioners, resulting in poor defrosting performance. Examples 1-5, however, showed better defrosting performance. This indicates that only when the content of the first organic phase change material is 35-65 parts by weight, the content of the second organic phase change material is 35-65 parts by weight, the content of the enthalpy enhancer is 0.1-3 parts by weight, and the content of the thickener is 1-3 parts by weight, can the prepared phase change material exhibit good defrosting performance.

[0164] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. Furthermore, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction.

[0165] It should be noted that in this specification, the terms "first" and "second" are used for description only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0166] In the description of this specification, the references to terms such as "one embodiment," "some specific embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0167] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A composition characterized in that, The composition comprises: 35-65 parts by weight of a first organic phase change material, 35-65 parts by weight of a second organic phase change material, 0.1-3 parts by weight of an enthalpy enhancer, and 1-3 parts by weight of a thickener. The first organic phase change material is different from the second organic phase change material, and is independently selected from polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000, and polyethylene glycol 2000. The enthalpy enhancer includes fatty acids; The fatty acids include at least one of palmitic acid, stearic acid, capric acid, linolenic acid, and linoleic acid; The thickener is polyvinyl alcohol.

2. A method of preparing a phase change material, characterized by, The method includes mixing the components of the composition according to claim 1 to obtain a phase change material.

3. The method of claim 2, wherein, The method includes: The first organic phase change material and the second organic phase change material are heated and melted respectively; The molten first organic phase change material and the molten second organic phase change material are mixed to obtain a first mixture. The first mixture is mixed with an enthalpy enhancer to obtain a second mixture; The second mixture is mixed with a thickener to obtain a phase change material.

4. The method of claim 3, wherein, After the second mixture is mixed with the thickener, the method further includes: subjecting the mixture of the second mixture and the thickener to vacuum drying, and then naturally cooling it to room temperature after the vacuum drying is completed to obtain a phase change material; The vacuum drying process is carried out in a vacuum drying chamber, the vacuum degree of the vacuum drying process is (-1.5) to (-0.5) bar, the temperature of the vacuum drying process is 40 to 60°C, and the time of the vacuum drying process is 20 to 40 minutes.

5. A phase change material prepared by the method according to any one of claims 2-4.

6. The phase change material according to claim 5, characterized in that, The phase transition temperature of the phase change material is 28-32℃; The phase change enthalpy of the phase change material is ≥130 J / g; The supercooling degree of the phase change material is ≤2℃.

7. The application of the phase change material as described in claim 5 or 6 in multi-split air conditioning systems.

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