A method for improving the latent heat of solid-liquid phase transition in high-purity paraffin

Abstract

The present invention belongs to the technical field of heat storage materials, and specifically relates to a method for increasing the latent heat of solid-liquid phase change of high-purity paraffin, comprising the following steps: preparing an ethanol saturated solution of an inorganic salt at room temperature; heating the high-purity paraffin at 80°C to completely melt it, and obtaining liquid high-purity paraffin; adding the obtained ethanol saturated solution of an inorganic salt to the obtained liquid high-purity paraffin in a certain ratio under 80°C and stirring conditions, and after keeping warm and stirring for a certain period of time, standing and cooling to solid, the high-purity paraffin with increased latent heat of phase change can be obtained. The present invention increases the melting latent heat of the high-purity paraffin by adding an inorganic salt ethanol solution to the high-purity paraffin, further increases the heat absorption and heat storage density of the paraffin, and at the same time, the melting peak temperature of the high-purity paraffin remains basically unchanged; the required amount under the same conditions is smaller, which can further save the internal space of the instrument and increase the effective load of the instrument under the same volume.

Description

Technical Field

[0001] The invention belongs to the technical field of heat storage materials, and in particular relates to a method for increasing the latent heat of solid-liquid phase change of high-purity paraffin. Background Art

[0002] High-purity paraffin wax is a type of material with the largest latent heat among the low-temperature phase change heat storage materials currently available on the market, and is also called high phase change enthalpy paraffin wax. High phase change enthalpy paraffin wax is currently mainly used in the control of ambient temperature during pulsed operation of precision electronic components in aerospace and other aircraft. During operation, the high phase change enthalpy paraffin wax melts within a fixed phase change temperature range to absorb a large amount of heat released by the electronic components during operation, thereby keeping the temperature of the device constant during the working period. Since various aircraft, especially aviation aircraft, are expensive and extremely sensitive to weight, paraffin phase change materials with higher heat absorption density can reduce their use in aircraft while maintaining the same heat absorption effect, which is of great significance for further increasing the payload of aircraft. In a large number of practices, people have found that the latent heat of phase change is highest when the length of the straight-chain alkane molecular chain in paraffin is consistent.

[0003] At present, while keeping the phase change temperature basically unchanged, people mainly improve the latent heat of phase change by increasing the molecular purity of the specified paraffin wax, that is, removing impurities outside the specified linear alkane molecular chain length and alkane molecules whose chain length does not meet the requirements by physical or chemical methods, so that the molecular chain lengths of all linear alkanes are consistent. For example, patent CN202011629314.X mentions a method for obtaining high-quality phase change raw wax by molecular distillation purification; patent CN201210517647.2 mentions that high phase change enthalpy paraffin can be obtained by distilling and purifying the phase change paraffin made by urea complexation. When the purity of high phase change enthalpy paraffin is extremely high, due to the similar properties of linear alkanes with similar chain lengths, the difficulty of further separation and purification will become extremely difficult as the content of alkanes with specified chain lengths increases, which leads to extremely high cost of high phase change enthalpy paraffin. At the same time, it becomes extremely difficult to increase its solid-liquid phase change latent heat by purification, and the room for improvement is extremely limited.

[0004] In addition to the purification method, other methods that can stably increase the latent heat of solid-liquid phase change of paraffin wax and further increase the latent heat of phase change of such high phase change enthalpy paraffin wax through physical or chemical means have basically not been reported. Summary of the invention

[0005] In view of the current situation that the existing technology can only improve the melting latent heat of paraffin wax (solid-liquid phase change latent heat) by purification means, but there is no effective means to further improve the melting latent heat of high-purity paraffin wax (which has been purified). The present invention aims to provide a method for improving the melting latent heat of high-purity paraffin wax, which can further increase the melting latent heat of high-purity paraffin wax, and when it is applied to the ambient temperature control of precision electronic components in aircraft such as aerospace, the required amount is less, which can further save instrument space and increase the payload of the aircraft.

[0006] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0007] A method for increasing the latent heat of solid-liquid phase change of high-purity paraffin wax comprises the following steps:

[0008] 1) Prepare a saturated ethanol solution of an inorganic salt at room temperature;

[0009] 2) heating the high-purity paraffin at 80° C. to completely melt the paraffin to obtain liquid high-purity paraffin;

[0010] 3) At 80° C. and under stirring conditions, the ethanol saturated solution of the inorganic salt obtained in step 1) is added to the liquid high-purity paraffin obtained in step 2) in a certain ratio, and after keeping warm and stirring for a certain period of time, the mixture is allowed to stand and cool to a solid state, thereby obtaining high-purity paraffin with increased latent heat of phase change.

[0011] Furthermore, in the method for increasing the latent heat of solid-liquid phase change of high-purity paraffin as described above, in step 1), the inorganic salt is barium chloride dihydrate.

[0012] Furthermore, in the method for increasing the latent heat of solid-liquid phase change of high-purity paraffin as described above, in step 1), the ethanol is anhydrous ethanol.

[0013] Furthermore, in the method for increasing the latent heat of solid-liquid phase change of high-purity paraffin as described above, in step 3), the mass ratio of the saturated ethanol solution of the inorganic salt to the liquid high-purity paraffin is 1:10-100.

[0014] Furthermore, in the method for increasing the latent heat of solid-liquid phase change of high-purity paraffin as described above, the mass ratio of the saturated ethanol solution of the inorganic salt to the liquid high-purity paraffin is 1:40.

[0015] Furthermore, in the method for increasing the latent heat of solid-liquid phase change of high-purity paraffin wax as described above, in step 3), the specific operation of heat preservation and stirring is: first stirring in a sealed state at 80° C. for a period of time, and then stirring in an open state for a period of time.

[0016] Furthermore, the method for increasing the latent heat of solid-liquid phase change of high-purity paraffin wax as described above, the specific operation of heat preservation and stirring is: first stirring in a sealed state at 80°C for 40 to 80 minutes, and then stirring in an open state for 40 to 80 minutes.

[0017] Furthermore, the method for increasing the latent heat of solid-liquid phase change of high-purity paraffin wax as described above, the specific operation of heat preservation and stirring is: first sealed stirring at 80°C for 60 minutes, and then open stirring for 60 minutes.

[0018] The beneficial effects of the present invention are:

[0019] 1. Compared with untreated high-purity paraffin, the melting latent heat of the high-purity paraffin treated by the technical solution of the present invention increases to a certain extent (the maximum increase can reach 6.97%), which further improves the heat storage density of the high-purity paraffin. At the same time, the melting peak temperature of the high-purity paraffin remains basically unchanged, and the heat absorption and heat preservation performance is better than that of the untreated high-purity paraffin, so that the amount required when it is used for the working environment temperature control of precision electronic components under the same conditions is smaller.

[0020] 2. The present invention takes into account the good solubility of ethanol in liquid alkanes. Therefore, even a very small amount of ethanol can be uniformly dispersed in the liquid alkane under stirring conditions in a short time. Therefore, configuring the inorganic salt into an ethanol saturated solution can make the trace amount of inorganic salt dispersed evenly in the liquid alkane system, ensuring that the physical properties are consistent everywhere in the system.

[0021] 3. The present invention firstly stirs in a sealed state so that the added ethanol cannot evaporate, ensuring that the saturated solution of inorganic salt ethanol is evenly dispersed in the liquid alkane system; then stirs in an open state so that the excess ethanol below the stirring temperature and the trace crystal water brought in by the inorganic salt evaporate or volatilize, while the inorganic salt cannot volatilize in this process and remains in the system, thus finally obtaining a constant temperature eutectic system containing only inorganic salt and alkane / trace ethanol / trace water, so that the melting point of the system can remain basically unchanged. The anions and cations of the trace inorganic salts entering the system affect the curling and crystallization degree of the alkane carbon chain, thereby changing the latent heat of fusion of the system.

[0022] Of course, any product implementing the present invention does not necessarily need to achieve all of the above advantages at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0024] Figure 1 This is a real photo of the product in Example 2;

[0025] Figure 2 This is a real photo of FPC74 high-purity paraffin. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The present invention uses a DSC-500B differential scanning calorimeter produced by Shanghai Yingnuo Precision Instrument Co., Ltd. to measure the latent heat and related temperature of the product. Test conditions: take 10 mg of powdered sample in an aluminum crucible with a cover and seal for measurement; during the test, dry nitrogen is used as the purge gas with a flow rate of 20 mL / min; the test temperature range is from room temperature to 100°C, the temperature is first raised from room temperature to 100°C, and then dropped to room temperature, and the heating and cooling rate is 3.0°C / min.

[0028] All embodiments take FPC74 high-purity paraffin produced by Zhejiang Huangxing Chemical as an example (the peak melting temperature of the high-purity paraffin is 75.9° C. and the latent heat of melting is 182.36 J / g). The actual picture of FPC74 high-purity paraffin is as follows: Figure 2 shown.

[0029] The specific embodiments of the present invention are as follows:

[0030] Example 1

[0031] A method for increasing the latent heat of solid-liquid phase change of high-purity paraffin wax is achieved by adding barium chloride dihydrate and anhydrous ethanol to FPC74 high-purity paraffin wax in a certain proportion and steps. The specific process is carried out according to the following steps:

[0032] 1) Prepare a saturated solution of barium chloride dihydrate in ethanol at room temperature.

[0033] 2) 100 parts by mass of high-purity paraffin wax are heated at 80° C. to completely melt the wax, thereby obtaining liquid high-purity paraffin wax.

[0034] 3) Under stirring conditions at 80°C, add 1.0 part of the saturated solution of barium chloride dihydrate in ethanol obtained in step 1) to the liquid high-purity paraffin obtained in step 2). Seal and heat-insulate and stir for 60 minutes, then stir in an open container for another 60 minutes, and then cool to a solid state to obtain high-purity paraffin with increased melting latent heat.

[0035] The high-purity paraffin obtained after treatment has a melting peak temperature of 75.3°C and a melting latent heat of 183.95 J / g. The melting peak temperature remains basically unchanged, and the melting latent heat increases by 0.87%.

[0036] Example 2

[0037] A method for increasing the latent heat of solid-liquid phase change of high-purity paraffin wax is achieved by adding barium chloride dihydrate and anhydrous ethanol to FPC74 high-purity paraffin wax in a certain proportion and steps. The specific process is carried out according to the following steps:

[0038] 1) Prepare a saturated solution of barium chloride dihydrate in ethanol at room temperature.

[0039] 2) 100 parts by mass of high-purity paraffin wax are heated at 80° C. to completely melt the wax, thereby obtaining liquid high-purity paraffin wax.

[0040] 3) Add 2.5 parts of the saturated solution of barium chloride dihydrate in ethanol obtained in step 1) to the liquid high-purity paraffin obtained in step 2) at 80°C with stirring. Stir for 60 minutes in a sealed container and then stir for 60 minutes in an open container, and then cool to a solid state to obtain high-purity paraffin with increased melting latent heat.

[0041] The high-purity paraffin obtained after the treatment has a melting peak temperature of 75.3° C. and a melting latent heat of 195.07 J / g. The melting peak temperature remains basically unchanged, and the melting latent heat increases by 6.97%.

[0042] Example 3

[0043] A method for increasing the latent heat of solid-liquid phase change of high-purity paraffin wax is achieved by adding barium chloride dihydrate and anhydrous ethanol to FPC74 high-purity paraffin wax in a certain proportion and steps. The specific process is carried out according to the following steps:

[0044] 1) Prepare a saturated solution of barium chloride dihydrate in ethanol at room temperature.

[0045] 2) 100 parts by mass of high-purity paraffin wax are heated at 80° C. to completely melt the wax, thereby obtaining liquid high-purity paraffin wax.

[0046] 3) Add 5.0 parts of the saturated solution of barium chloride dihydrate in ethanol obtained in step 1) to the liquid high-purity paraffin obtained in step 2) at 80°C with stirring. Stir for 60 minutes in a sealed container and then stir for 60 minutes in an open container, and then cool to a solid state to obtain high-purity paraffin with increased melting latent heat.

[0047] The high-purity paraffin obtained after the treatment has a melting peak temperature of 75.4° C. and a melting latent heat of 192.87 J / g. The melting peak temperature remains basically unchanged, and the melting latent heat increases by 5.76%.

[0048] Example 4

[0049] A method for increasing the latent heat of solid-liquid phase change of high-purity paraffin wax is achieved by adding barium chloride dihydrate and anhydrous ethanol to FPC74 high-purity paraffin wax in a certain proportion and steps. The specific process is carried out according to the following steps:

[0050] 1) Prepare a saturated solution of barium chloride dihydrate in ethanol at room temperature.

[0051] 2) 100 parts by mass of high-purity paraffin wax are heated at 80° C. to completely melt the wax, thereby obtaining liquid high-purity paraffin wax.

[0052] 3) Under stirring conditions at 80°C, 7.5 parts of the saturated solution of barium chloride dihydrate in ethanol obtained in step 1) are added to the liquid high-purity paraffin obtained in step 2). The mixture is sealed and stirred for 60 minutes, and then stirred for 60 minutes in an open state, and then cooled to a solid state, thereby obtaining high-purity paraffin with increased melting latent heat. The high-purity paraffin obtained after the treatment has a melting peak temperature of 75.5°C, a melting latent heat of 191.40 J / g, a melting peak temperature that is substantially unchanged, and a melting latent heat that is increased by 4.96%.

[0053] Example 5

[0054] A method for increasing the latent heat of solid-liquid phase change of high-purity paraffin wax is achieved by adding barium chloride dihydrate and anhydrous ethanol to FPC74 high-purity paraffin wax in a certain proportion and steps. The specific process is carried out according to the following steps:

[0055] 1) Prepare a saturated solution of barium chloride dihydrate in ethanol at room temperature.

[0056] 2) 100 parts by mass of high-purity paraffin wax are heated at 80° C. to completely melt the wax, thereby obtaining liquid high-purity paraffin wax.

[0057] 3) Add 10.0 parts of the saturated solution of barium chloride dihydrate in ethanol obtained in step 1) to the liquid high-purity paraffin obtained in step 2) at 80°C with stirring. Stir for 60 minutes in a sealed container and then stir for 60 minutes in an open container, and then cool to a solid state to obtain high-purity paraffin with increased melting latent heat.

[0058] The high-purity paraffin obtained after the treatment has a melting peak temperature of 75.4° C. and a melting latent heat of 183.83 J / g. The melting peak temperature remains basically unchanged, and the melting latent heat increases by 0.81%.

[0059] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for increasing the latent heat of solid-liquid phase change of high-purity paraffin wax, characterized in that: The steps include: 1) Prepare a saturated ethanol solution of an inorganic salt at room temperature; wherein the inorganic salt is barium chloride dihydrate and the ethanol is anhydrous ethanol; 2) The high-purity paraffin is FPC74 high-purity paraffin produced by Zhejiang Huangxing Chemical Industry; the high-purity paraffin is heated at 80° C. to completely melt it, thereby obtaining liquid high-purity paraffin; the mass ratio of the ethanol saturated solution of the inorganic salt to the liquid high-purity paraffin is 1:10-100; 3) At 80° C. and under stirring conditions, the ethanol saturated solution of the inorganic salt obtained in step 1) is added to the liquid high-purity paraffin obtained in step 2) in a certain ratio, and the mixture is first stirred in a sealed state for 40 to 80 min at 80° C., then stirred in an open state for 40 to 80 min, and allowed to stand and cool into a solid, thereby obtaining high-purity paraffin with increased latent heat of phase change.

2. The method for increasing the latent heat of solid-liquid phase change of high-purity paraffin according to claim 1, characterized in that: The mass ratio of the saturated ethanol solution of the inorganic salt to the liquid high-purity paraffin is 1:

40.

3. The method for increasing the latent heat of solid-liquid phase change of high-purity paraffin according to claim 1, characterized in that: The specific operation of heat preservation stirring is: first stir in a sealed state at 80°C for 60 min, and then stir in an open state for 60 min.

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