JP2007112865A - Slurry for transportation of latent heat - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slurry for transportation of latent heat absorbing heat of fusion at high temperature zone and suppressing recrystallization at low temperature zone in minimum by reducing solubility of an inorganic hydrate to a solvent at the high temperature zone. <P>SOLUTION: The slurry for transportation of latent heat comprises a latent heat absorbing inorganic hydrate, a mixed solvent comprising a solvent with a poor solubility to the latent heat absorbing inorganic hydrate and water. The slurry has a predetermined range of solubility difference to the latent heat absorbing inorganic hydrate at a latent heat absorbing temperature with the solubility to the latent heat absorbing inorganic hydrate at 5-25°C, and the solid content to the total system is less than 30%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a latent heat transport slurry used as a latent heat transport medium used in a thermal apparatus or a heat engine.

  Thermal equipment and heat engines have a cooling facility in order to suppress temperature rise during operation. Some of them require high-performance cooling equipment, but this can be done by increasing the amount of cooling medium transported to achieve high heat transfer or using a cooling medium with a large latent heat. is doing.

  Examples of the cooling medium having a large latent heat include organic and inorganic hydrates as disclosed in Patent Document 1 below. In general, organic hydrates are those in which water molecules are coordinated in a cage form with respect to organic substances having a hydrating group as a guest substance, and are also called clathrate hydrates because of their shapes. Such organic hydrates are considered as useful latent heat transport materials because they have relatively large latent heat, stably produce hydrates, and have low supercooling. However, organic hydrates are generally expensive, have a low phase transition temperature, and are unsuitable for some thermal equipment and heat engines. In contrast, inorganic hydrates are substances in which water molecules are incorporated into crystals as crystallization water, and generally there are substances that are inexpensive and have high latent heat. Therefore, inorganic hydrates are often used in general thermal equipment and heat engines.

JP 2005-29591 A

  However, inorganic hydrates may not be able to absorb heat of fusion at the phase transition point because of their relatively high solubility in solvents at high temperatures such as when operating thermal equipment and heat engines. As a countermeasure, it is conceivable that an inorganic hydrate in an amount exceeding the solubility in a solvent in a high temperature range is added to the solvent so as not to be completely dissolved and the heat of fusion is absorbed. However, such a cooling medium, for example, when the operation of the thermal equipment or the heat engine is stopped and cooled, excess inorganic hydrates precipitate (recrystallize) at low temperatures, The viscosity becomes higher than necessary. As a result, the flow rate of the cooling medium is reduced, and there is a possibility that the cooling medium cannot be transported below a predetermined temperature.

  Accordingly, an object of the present invention is to reduce the solubility of the inorganic hydrate in the solvent in the high temperature range, thereby absorbing the heat of fusion in the high temperature range and suppressing the recrystallization in the low temperature range to a minimum. It is to provide a slurry for transportation.

  The slurry for transporting latent heat of the present invention includes a latent heat-absorbing inorganic hydrate, and a mixed solvent composed of a solvent in which the latent heat-absorbing inorganic hydrate is hardly soluble and water. “Slightly soluble” here means that the solubility (the amount of solute with respect to 100 g of solvent) is 0.5 or less.

  In the slurry for transporting latent heat of the present invention, the difference between the solubility of the latent heat absorbing inorganic hydrate in the mixed solvent at the latent heat absorption temperature and the solubility of the absorbing inorganic hydrate in the mixed solvent at 5 to 25 ° C. is 0. Further, it is preferably 40 or less, and more preferably the ratio of the solid content to the whole at 5 to 25 ° C. is 30% or less. At this time, in the slurry for latent heat transport of the present invention, the latent heat absorbing inorganic hydrate is potassium aluminum sulfate dodecahydrate (also called potassium alum), aluminum sulfate 14 to 18 hydrate, or aluminum sulfate. Preferably, it is ammonium dodecahydrate, and the solvent is a dihydric alcohol having 2 or 3 carbon atoms.

  From another point of view, the slurry for latent heat transport of the present invention has a solubility in the mixed solvent of the latent heat absorbing inorganic hydrate at a latent heat absorption temperature, and a solubility of the absorbed inorganic hydrate in the mixed solvent at 5 to 20 ° C. Is preferably 40 or less above 0, more preferably 30% or less of the solid content with respect to the whole at 5 to 20 ° C. At this time, the slurry for transporting latent heat of the present invention is preferably sodium dihydrogen phosphate dodecahydrate, and the solvent is a dihydric alcohol having 2 or 3 carbon atoms. Alternatively, the latent heat absorbing inorganic hydrate may be sodium acetate trihydrate, and the solvent may be a monohydric alcohol having 3 to 5 carbon atoms.

  With the above configuration, the solubility of inorganic hydrates in solvents at high temperatures can be reduced, so that heat of fusion at high temperatures can be absorbed and recrystallization of hydrates at low temperatures is minimized. It is possible to provide a slurry for transporting latent heat having high fluidity even in a low temperature range.

BEST MODE FOR CARRYING OUT THE INVENTION

  The latent heat transport slurry according to the embodiment of the present invention will be described below. The slurry for transporting latent heat according to the present embodiment is a mixture comprising a latent heat-absorbing inorganic hydrate, a solvent in which the latent heat-absorbing inorganic hydrate exhibits poor solubility (hereinafter referred to as a poorly soluble solvent), and water (pure water). And a solvent.

  The combination of inorganic hydrate and sparingly soluble solvent is (1) potassium aluminum sulfate dodecahydrate (latent heat absorption at 92.5 ° C., latent heat 238 kJ / kg · K), aluminum sulfate 14 to 18 hydrate Latent heat absorption at 112 ° C., latent heat 182 kJ / kg · K), ammonium ammonium sulfate dodecahydrate (latent heat absorption at 93.5 ° C., latent heat 269 kJ / kg · K), or sodium dihydrogen phosphate dodecahydrate Product (latent heat absorption at 35 ° C., latent heat 281 kJ / kg · K) and dihydric alcohol with 2 or 3 carbon atoms, (2) sodium acetate trihydrate (latent heat absorption at 58 ° C., latent heat 264 kJ / kg · K) And a monohydric alcohol having 3 to 5 carbon atoms.

  In addition, regarding potassium aluminum sulfate dodecahydrate, aluminum sulfate fourteen to eighteen hydrate, aluminum ammonium sulfate dodecahydrate, the latent heat absorption inorganic hydrate at the latent heat absorption temperature with respect to the mixed solvent. The difference between the solubility and the solubility of the absorbed inorganic hydrate at 5 to 25 ° C. in the mixed solvent is set to be 40 or less above 0. Thereby, since it does not partition by melting, latent heat transport is possible. Furthermore, the ratio of the solid content with respect to the whole in 5-25 degreeC shall be 30% or less. Thereby, the fluidity | liquidity in 5-25 degreeC is securable.

  Next, in the case of sodium dihydrogen phosphate dodecahydrate, the solubility of the latent heat absorbing inorganic hydrate at the latent heat absorption temperature in the mixed solvent and the mixing of the absorbed inorganic hydrate at 5 to 20 ° C. The difference from the solubility in the solvent is 40 or less above 0, and the ratio of the solid content to the whole at 5 to 20 ° C. is 30% or less. In the case of sodium acetate trihydrate, the difference between the solubility of the latent heat absorption inorganic hydrate at the latent heat absorption temperature in the mixed solvent and the solubility of the absorption inorganic hydrate at 5 to 20 ° C. in the mixed solvent is It is 40 or less above 0, and the ratio of the solid content to the whole at 5 to 20 ° C. is 30% or less. As in the case of using the above-described potassium aluminum sulfate dodecahydrate, these are adjusted to enable latent heat transport and to ensure fluidity at low temperatures.

  Here, examples of the dihydric alcohol having 2 or 3 carbon atoms include ethylene glycol and propylene glycol. Examples of the monohydric alcohol having 3 to 5 carbon atoms include 1-butyl alcohol and propyl alcohol.

  With the above configuration, the solubility of inorganic hydrates in high-temperature mixed solvents can be reduced, so that heat of fusion can be absorbed at high temperatures and recrystallization of hydrates at low temperatures can be minimized. It is possible to provide a slurry for transporting latent heat having high fluidity even in a low temperature range.

  Next, the latent heat transport slurry according to the present invention will be described with reference to examples. Here, in the combination of Examples 1 to 5 shown in Table 1 below, the solubility and latent heat of the inorganic hydrate in the mixed solvent were measured using the method described later. Moreover, about Examples 1-3, the mixing ratio of water and ethylene glycol is (1) 10: 0 (comparative example), (2) 7: 3, (3) 5: 5, (4) 3: 7. For Example 4 adjusted to be, (1) 10: 0 (Comparative Example), (2) 7: 3, and (3) 5: 5 were measured. About Example 5, what adjusted so that the mixing ratio of water and 1-butyl alcohol might be set to (1) 10: 0 (comparative example), (2) 7: 3, (3) 5: 5 was measured. did.

(Measurement method of solubility)
100 ml of the mixed solution of each Example was collected in a beaker, and the temperature was controlled by immersing the beaker together with the thermostatic bath. 1 g of each inorganic hydrate was added to this and stirred, and the amount that did not dissolve at each predetermined temperature was defined as solubility.

(Measurement results of solubility in each example)
The graph which shows the measurement result of the solubility of the said Examples 1-5 is shown in FIGS. In addition, the curve in each figure is a solubility curve estimated from a measurement result. As shown in FIG. 1, when ethylene glycol is not added (water: ethylene glycol = 10: 0), the solubility is 250 or more near the phase transition point (92.5 ° C.) of potassium aluminum sulfate dodecahydrate. It can be seen that the solubility is only 20 or less at room temperature (around 5 ° C. to 25 ° C.). In order for the latent heat fine particles made of potassium aluminum sulfate to be present near the phase transition point (92.5 ° C.), potassium aluminum sulfate dodecahydrate having a solubility higher than this is required. Therefore, in the case where 250 g or more of potassium aluminum sulfate dodecahydrate is dissolved in 100 g of pure water in order to make the latent heat fine particles exist at the phase transition point, the potassium aluminum sulfate dodecahydrate is cooled to room temperature. 200 g or more of the Japanese precipitate is precipitated, and fluidization cannot be expected at room temperature. On the other hand, when ethylene glycol is added, the solubility at high temperatures can be suppressed as shown in FIG. 1, so that the amount of potassium aluminum sulfate dodecahydrate dissolved can be suppressed accordingly. I understand. This becomes more pronounced as the amount of ethylene glycol added increases. As a result, in the slurry for transporting latent heat of Example 1 according to the present invention, even when potassium aluminum sulfate dodecahydrate is included at a solubility higher than the phase transition point, when cooled to room temperature, potassium aluminum sulfate It can be seen that fluidization can be expected even at room temperature because the amount of twelve hydrate precipitated can be suppressed.

  Also in Examples 2 to 5, as shown in FIGS. 2 to 5, it can be seen that although the solubility differs depending on the substance used, results showing the same effect as Example 1 are obtained.

(Measurement method of latent heat)
Next, a method for measuring the latent heat of the slurry for latent heat transportation according to each example will be described. Here, using a differential scanning calorimeter (Shimadzu DSC-60), DSC (Differential Scanning Calorimetry) was performed to measure latent heat.

(Measurement results of latent heat in each example)
The graph which shows the measurement result of the latent heat of the said Examples 1-5 is shown to FIGS. Since it is endothermic, the differential scanning calorimeter 100 originally displays a negative value, but here it is replaced with a positive value. The integrated value of this DSC curve is the latent heat.

  In FIG. 6, it can be seen that the DSC curve in the case of only the powder of potassium aluminum sulfate dodecahydrate starts to rise rapidly in the vicinity of the phase transition temperature (88 ° C.) and decreases rapidly in a narrow temperature range. The latent heat obtained from the integration is 229 kJ / kg · K, which is almost the same as the literature value (edited by Nobuhiro Seki, Thermal Storage Engineering 1 Basics, Morikita Publishing 1995). On the other hand, in the case of water: ethylene glycol = 3: 7, the temperature gradually changes around 70 ° C., the endotherm continues to around 85 ° C., and the latent heat absorption temperature decreases to 79.8 ° C. The integrated value of the DSC curve in this case is 32.1 kJ / kg · K from FIG. 6, and FIG. 1 shows that the solid weight ratio of the potassium aluminum sulfate dodecahydrate fine particles is 14 wt%. That is, it is understood that when a solvent in which water and ethylene glycol are mixed is used, the solid weight ratio sufficient for heat transport can be maintained at the latent heat absorption temperature. This is the same when water: ethylene glycol is 5: 5, 7: 3. However, latent heat could not be obtained when water: ethylene glycol was 2: 8, 0:10. Therefore, in FIG. 6, the lines representing the results of water: ethylene glycol 2: 8, 0:10 coincide with the temperature axis.

  Also in Examples 2 to 5, as shown in FIGS. 7 to 10, it can be seen that although the latent heat and the latent heat absorption temperature are different depending on the substance used, results showing the same effects as Example 1 are obtained.

  The present invention can be changed in design without departing from the scope of the claims, and is not limited to the above-described embodiments and examples.

It is a graph which shows the measurement result of the solubility of the inorganic hydrate in the slurry for latent heat transportation of Example 1 which concerns on this invention. It is a graph which shows the measurement result of the solubility of the inorganic hydrate in the slurry for latent heat transportation of Example 2 which concerns on this invention. It is a graph which shows the measurement result of the solubility of the inorganic hydrate in the slurry for latent heat transportation of Example 3 which concerns on this invention. It is a graph which shows the measurement result of the solubility of the inorganic hydrate in the slurry for latent heat transportation of Example 4 which concerns on this invention. It is a graph which shows the measurement result of the solubility of the inorganic hydrate in the slurry for latent heat transportation of Example 5 which concerns on this invention. It is a graph which shows the measurement result of the latent heat in the slurry for latent heat transport of Example 1 which concerns on this invention. It is a graph which shows the measurement result of the latent heat in the slurry for latent heat transport of Example 2 which concerns on this invention. It is a graph which shows the measurement result of the latent heat in the slurry for latent heat transport of Example 3 which concerns on this invention. It is a graph which shows the measurement result of the latent heat in the slurry for latent heat transport of Example 4 which concerns on this invention. It is a graph which shows the measurement result of the latent heat in the slurry for latent heat transport of Example 5 which concerns on this invention.

Claims (6)

  A slurry for latent heat transport comprising a latent heat absorbing inorganic hydrate, and a mixed solvent comprising water and a solvent in which the latent heat absorbing inorganic hydrate is sparingly soluble.   The difference between the solubility of the latent heat-absorbing inorganic hydrate in the mixed solvent at the latent heat absorption temperature and the solubility of the absorbed inorganic hydrate in the mixed solvent at 5 to 25 ° C. is from 40 to 40 inclusive. The slurry for transporting latent heat according to claim 1, wherein the slurry is a latent heat transport slurry.   The difference between the solubility of the latent heat-absorbing inorganic hydrate at the latent heat absorption temperature in the mixed solvent and the solubility of the absorbed inorganic hydrate at 5 to 20 ° C. in the mixed solvent is from 0 to 40 or less. The slurry for transporting latent heat according to claim 1, wherein the slurry is a latent heat transport slurry. The latent heat absorbing inorganic hydrate is potassium aluminum sulfate dodecahydrate, aluminum sulfate 14 to 18 hydrate, or aluminum ammonium sulfate dodecahydrate,
The slurry for latent heat transportation according to claim 2, wherein the solvent is a dihydric alcohol having 2 or 3 carbon atoms.   4. The latent heat transport slurry according to claim 3, wherein the latent heat absorbing inorganic hydrate is sodium dihydrogen phosphate dodecahydrate and the solvent is a dihydric alcohol having 2 or 3 carbon atoms. . The latent heat transporting slurry according to claim 3, wherein the latent heat absorbing inorganic hydrate is sodium acetate trihydrate, and the solvent is a monohydric alcohol having 3 to 5 carbon atoms.

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