METHOD FOR OBTAINING NITRATE-BASED EUTETIC MIXTURES TO THERMAL STORAGE IN SOLAR COOLING SYSTEMS AND SUCH EUTETIC MIXTURES
20230040088 · 2023-02-09
Inventors
- Svetlana Nikolaevna USHAK DE GRAGEDA (Antofagasta, CL)
- Mario Sandro GRAGEDA ZEGARRA (Antofagasta, CL)
- Jorge Alfredo LOVERA COPA (Antofagasta, CL)
- Mariela Cecilia VEGA PANOZO (Antofagasta, CL)
Cpc classification
Y02E60/14
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
C09K5/12
CHEMISTRY; METALLURGY
C09K5/06
CHEMISTRY; METALLURGY
C09K5/00
CHEMISTRY; METALLURGY
International classification
Abstract
The present invention is related to a method for obtaining nitrate-based eutectic mixtures based on a BET model to thermal storage of solar refrigeration systems within the range of temperature from 0 to 15° C. Mixtures based on the following hydrate salts: LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O, having melting points of 10.8, −1.1, 13.1, 12.0 and 7.1° C., respectively. Thermal and physical properties were established such as the heat of crystallization/melting, calorific capacity to solid and liquid phases, viscosity, density and change of volume during the mixture of eutectic mixtures. The results of energy storing density (esd) varied from 238.3 to 304.5 MJ.Math.m.sup.−3. The phase changing material (PCM) being more potent to be used in solar energy-assisted air conditioning systems (AC) is LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O.
Claims
1. Method for preparing a quaternary eutectic salt LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O comprising mixing LiNO.sub.3.3H.sub.2O:NaNO.sub.3:Mn(NO.sub.3).sub.2.6H.sub.2O at a mass ratio 24.2:3.0:72.8 into water, adding firstly LiNO.sub.3.3H.sub.2O into water, then NaNO.sub.3 and after Mn(NO.sub.3).sub.2.6H.sub.2O under constant stirring and at a temperature of 30° C. up to achieving a total dissolution and then allowing the salt formation.
2. A quaternary eutectic salt LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O prepared by the method of claim 1.
3. Use of the salt of claim 2 as phase changing material (PCM) to short-term thermal storing units in a solar cooling/heating system.
4. Method for preparing a quaternary eutectic salt LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O comprising mixing LiNO.sub.3.3H.sub.2O:NH.sub.4NO.sub.3:Mn(NO.sub.3).sub.2.6H.sub.2O at a mass ratio 21.4:13.9:64.7 into water, firstly adding LiNO.sub.3.3H.sub.2O into water, then NH.sub.4NO.sub.3 and after Mn(NO.sub.3).sub.2.6H.sub.2O under constant stirring and at a temperature of 30° C. up to achieving total dissolution and then allowing the salt formation.
5. A quaternary eutectic salt LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O prepared by the method of claim 4.
6. Use of the salt of claim 5 as phase changing material (PCM) to short-term thermal storing units in a solar cooling/heating system.
7. Method for preparing a quaternary eutectic LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O comprising mixing LiNO.sub.3.3H.sub.2O:Mn(NO.sub.3).sub.2.6H.sub.2O:Mg(NO.sub.3).sub.2.6H.sub.2O at a mass ratio 22.9:68.6:8.5 into water, adding firstly LiNO.sub.3.3H.sub.2O into water, then Mn(NO.sub.3).sub.2.6H.sub.2O and after Mg(NO.sub.3).sub.2.6H.sub.2O under constant stirring and at a temperature of 30° C. up to achieving total dissolution and then allowing the salt formation.
8. A quaternary eutectic salt LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O prepared by the method of claim 7.
9. Use of the salt of claim 8 as phase changing (PCM) to short-term thermal storing units in a solar cooling/heating system.
10. Method for preparing a quaternary eutectic salt LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O comprising mixing LiNO.sub.3.3H.sub.2O:NH.sub.4NO.sub.3:Mg(NO.sub.3).sub.2.6H.sub.2O at a mass ratio 55.8:27.8:16.4 into water, adding firstly LiNO.sub.3.3H.sub.2O into water, then NH.sub.4NO.sub.3 and after Mg(NO.sub.3).sub.2.6H.sub.2O under constant stirring and at a temperature of 30° C. up to achieving total dissolution and then allowing the salt formation.
11. A quaternary eutectic salt LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O prepared by the method of claim 10.
12. Use of the salt of claim 11 as phase changing material (PCM) to short-term thermal storing units in a solar cooling/heating system.
13. Method for preparing a quaternary eutectic salt LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O comprising mixing LiNO.sub.3.3H.sub.2O:Mn(NO.sub.3).sub.2.6H.sub.2O:Ca(NO.sub.3).sub.2.4H.sub.2O at a mass ratio 17.7:55.3:27.0 into water, adding firstly LiNO.sub.3.3H.sub.2O into water, then Mn(NO.sub.3).sub.2.6H.sub.2O and after Ca(NO.sub.3).sub.2.4H.sub.2O under constant stirring and at a temperature of 30° C. up to achieving total dissolution, and the allowing the salt formation.
14. A quaternary eutectic salt prepared by the method of claim 13.
15. Use of the salt of claim as phase changing material (PCM) to short-term thermal storing units in a solar cooling/heating system.
Description
BRIEF DESCRIPTION OF FIGURES
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[0083] , A, B y C composition to compare. Upper vertex: Mn(NO.sub.3).sub.2.6H.sub.2O. Right lower vertex: NaNO.sub.3 and Left lower vertex: LiNO.sub.3.3H.sub.2O.
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[0085] , A, B and C composition to compare.
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DETAILED DESCRIPTION OF THE INVENTION
[0107] It is an objective of the present invention to provide alternative phase change materials (PCM) can be integrated to short-term thermal storage units (STES), as part of a solar refrigeration/heater system (SCH) to improve energetic efficiency in the building area.
[0108] In this way, the need to use heat or cold in the absence of the source that generates this heat or cold is solved, through its storage and subsequent release, in materials designed for this purpose. Phase Change Materials (PCM) operate at a fixed temperature corresponding to their melting temperature. PCMs change from a solid to a liquid state or vice versa and in this transition they can absorb or release a large amount of thermal energy, accumulating energy in the form of latent heat of fusion. The final application of these PCMs is defined by their melting temperature. PCMs are applied in passive air conditioning of buildings, heating/cooling systems, in electronic devices, optimization of hot/cold water tanks and even in solar plants. They cover a wide range of temperatures: from −40° C. to 500° C.
[0109] Then, alternative phase change materials (PCM) to the known ones were developed, using mixtures of inorganic nitrate salts as a base, which can be integrated into short-term thermal energy storage units (STES), as part of a solar cooling/heating system (SCH), to improve energy efficiency in the construction sector, in food transport, and in general, in any industrial/residential application that requires heat or cold to the phase transition temperature of PCMs. The eutectic mixtures developed have been tested at the laboratory level with no scaling data to any other semi-industrial level.
[0110] PCMs are used on a real scale in the air conditioning of buildings, both as a passive system with the integration of these in the envelopes (application range T=18-24° C.), as an active system, for example, in water storage ponds cold or hot (T=7-12° C. or 40 60° C.). Also, they are used in the transport sector with the need for cold, to transfer perishable substances/objects (food, vaccines). There are references to its patenting and use in solar systems.
[0111] The eutectic mixtures of table 5 and their use as PMC in AC systems is an objective of the present invention.
TABLE-US-00005 TABLE 5 T melt Components of inorganic “onset” ΔH Cp solid, Cp liq No salts mixtures + H.sub.2O (° C.) kJ .Math. kg−1 J .Math. g−1 .Math. K−1 J .Math. g−1 .Math. K−1 PCM 1 LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2 11 158 1.538 (0° C.) 2.500 (17° C.) PCM 2 LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2 −2 136 2.000 (−26° C.) 2.892 (12° C.) PCM 3 LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2 13 133 1.227 (0° C.) 2.600 (30° C.) PCM 4 NaNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2 22 not measured not measured not measured PCM 5 LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2 12 163 1.790 (−23° C.) 2.961 (25° C.) PCM 6 LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2 7 108 2.304 (−26° C.) 2.536 (12° C.)
[0112] The modified BET model for calculating the activity of salts and water in a multicomponent system was formulated from statistical mechanics by Ally and Braunstein (Ally M R, Braunstein J. Statistical mechanics of multilayer adsorption: electrolyte and water activities in concentrated solutions. J Chem Thermodyn 1998; 30(1):49-58. https://doi.org/10.1006/icht.1997.0278) Recently, a new version of this model has been published, where the system is considered as a regular solution and an empirical mixture parameter denoted by Ωij which represents the extra salt interactions i-sal j. Considering this modification, mathematical expressions of the activities of the system components were developed. The model parameters are given for various inorganic salts in the literature usually as a linear correlation with temperature, this is because the parameters do not vary strongly with temperature. Table 6 shows the data collected from the literature the parameters r.sub.i and ΔE.sub.i for the salts that form the quaternary systems and with which the calculations were carried out in the mathematical equations proposed by the literature to propose 10 quaternary mixtures. Table 7 shows the interaction parameters of Ωij as used.
[0113] Table 6 shows the data collected from the literature the parameters r.sub.i and ΔE.sub.i
TABLE-US-00006 r = a + bT ΔE = c + dT/(J .Math. mol.sup.−1) Salt a B C D Range Source LiCl 4.732 −0.00378 −8166.6 3.526 273-373 Zeng D, Ming J, Voigt W. Thermodynamic study of the system (LiCl + LiNO.sub.3 + H.sub.2O). J Chem. Thermodyn. 2008; 40(2): 232- 239. https://doi.org/10.1016/j.jct.2007.06.018 LiClO.sub.4 3.167 0 −7501 0 298 (Zeng D, Voigt W. Phase diagram calculation of molten salt hydrates using the modified BET equation. Calphad 2003; 27(3): 243-251. https://doi.org/10.1016/j.calphad.2003.09.004; Zeng D, Ming J, Voigt W. Thermodynamic study of the system (LiCl + LiNO.sub.3 + H.sub.2O). J Chem Thermodyn 2008; 40(2): 232-239. https://doi.org/10.1016/j.jct.2007.06.018) LiNO.sub.3 2.766 0.000143 −6583.6 5.495 293-373 (Zeng D, Ming J, Voigt W. Thermodynamic study of the system (LiCl + LiNO.sub.3 + H.sub.2O). J Chem Thermodyn 2008; 40(2): 232-239. https://doi.org/10.1016/j.jct.2007.06.018) NaNO.sub.3 1.8 0 −1000 0 373 (Zeng D, Ming J, Voigt W. Thermodynamic study of the system (LiCl + LiNO3 + H2O). J Chem Thermodyn 2008; 40(2): 232-239. https://doi.org/10.1016/j.jct.2007.06.018) NH.sub.4NO.sub.3 1.63 0 890 0 — (Zeng D, Ming J, Voigt W. Thermodynamic study of the system (LiCl + LiNO.sub.3 + H.sub.2O). J Chem Thermodyn 2008; 40(2): 232-239. https://doi.org/10.1016/j.jct.2007.06.018/ 01496390600743045 Mg(NO.sub.3).sub.2 5.579 0 0 −31.348 303-358 (Zeng D, Ming J, Voigt W. Thermodynamic study of the system (LiCl + LiNO.sub.3 + H.sub.2O). J Chem Thermodyn 2008; 40(2): 232-239. https://doi.org/10.1016/j.jct.2007.06.018/ 01496390600743045 Ca(NO.sub.3).sub.2 5.032 −0.0042 −4183 −4.88 298-373 Zeng D, Voigt W. Phase diagram calculation of molten salt hydrates using the modified BET equation. Calphad 2003; 27(3): 243-251. https://doi.org/10.1016/j.calphad.2003.09.004. Mn(NO.sub.3).sub.2 5.0 0 −7160 0 298 Zeng DW, Fan SS, Chen SH. Phase diagram prediction of system Mn(NO.sub.3).sub.2 —M(NO.sub.3).sub.n—H.sub.2O (M = Ca, Mg and Li) with modified BET model. Trans Nonferrous Met Soc China 2004; 6:1192-1198
TABLE-US-00007 TABLE 7 the interaction parameters of Ωij. Ωij = A + BT/(J .Math. mol.sup.−1) Salt i-Salt j A B Range Source LiCl—LiNO.sub.3 2231.5 10 273-323 Zeng D, Ming J, Voigt W. Thermodynamic study of the system (LiCl + LiNO.sub.3 + H.sub.2O). J Chem Thermodyn 2008; 40(2): 232-239. https://doi.org/10.1016/j.jct.2007.06.018 LiNO.sub.3—NH.sub.4NO.sub.3 2759.3 −14.286 273-363 Zeng D, Ming J, Voigt W. Thermodynamic study of the system (LiCl + LiNO.sub.3 + H.sub.2O). J Chem Thermodyn 2008; 40(2): 232-239. https://doi.org/10.1016/j.jct.2007.06.018 NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2 54031 −219.129 273-320 Zeng D W, Fan S S, Chen S H. Phase diagram prediction of system Mn(NO.sub.3).sub.2—M(NO.sub.3).sub.n—H.sub.2O (M = Ca, Mg and Li) with modified BET model. Trans Nonferrous Met Soc China 2004; 6: 1192-1198
[0114] As is known, the modified BET model has been successfully applied to calculate the melting temperature and chemical composition of a eutectic mixture of hydrated salts. For this purpose, the equations of the fusion process are required, which are known from the literature. Analogously to the parameters of the modified BET model, in the literature the coefficients A, B and C are also reported for various anhydrous and hydrated salts. In Table 8 these coefficients are given for the solids that establish the quaternary systems defined above.
TABLE-US-00008 TABLE 8 Constant coefficients Ink of different solid phases Ink = A + B/T + Cln(T) Solid Phase A B C Range, T/K Source LiCl•2H.sub.2O −36125.99 50.5965 0 273-292 Zeng D, Ming J, Voigt W. Thermodynamic study of the system (LiCl + LiNO.sub.3 + H.sub.2O). J Chem Thermodyn 2008; 40(2): 232-239. https://doi.org/10.1016/j.jct.2007.06.018 LiClO.sub.3•3H.sub.2O 8.537 −6505.9 0 298-368 Zeng D, Voigt W. Phase diagram calculation of molten salt hydrates using the modified BET equation. Calphad 2003; 27(3): 243-251. https://doi.org/10.1016/j.calphad.2003.09.004 LiNO.sub.3•3H.sub.2O 11057.869 −1235.211 198.82931 273-301 Li B, Zeng D, Yin X, Chen Q. Theoretical prediction and experimental determination of room-temperature phase change materials using hydrated salts as agents. J Therm Anal Calorim 2010; 100(2): 685-93. https://link.springer.com/article/10.1007%2Fs10973-009-0206-1 NaNO.sub.3 −15699.33 26.92 0 273-292 Li B, Zeng D, Yin X, Chen Q. Theoretical prediction and experimental determination of room-temperature phase change materials using hydrated salts as agents. J Therm Anal Calorim 2010; 100(2): 685-93. https://link.springer.com/article/10.1007%2Fs10973-009-0206-1 NH.sub.4NO.sub.3 −29822.983 436.06597 −60.704671 278-368 Li B, Zeng D, Yin X, Chen Q. Theoretical prediction and experimental determination of room-temperature phase change materials using hydrated salts as agents. J Therm Anal Calorim 2010; 100(2): 685-93. https://link.springer.com/article/10.1007%2Fs10973-009-0206-1] Ca(NO.sub.3).sub.2•4H.sub.2O 6.263 −5328.9 0 283-316 Zeng D, Voigt W. Phase diagram calculation of molten salt hydrates using the modified BET equation. Calphad 2003; 27(3): 243-251. https://doi.org/10.1016/j.calphad.2003.09.004 Mg(NO.sub.3).sub.2•6H.sub.2O — — — 273-362 Li B, Zeng D, Yin X, Chen Q. Theoretical prediction and experimental determination of room-temperature phase change materials using hydrated salts as agents. J Therm Anal Calorim 2010; 100(2): 685-93. https://link.springer.com/article/10.1007%2Fs10973-009-0206-1 Mn(NO.sub.3)2•6H.sub.2O.sup.a 38.845 −25924 2672400 278-300 Rains W O, Courice R M. Liquidus Curves of NH.sub.4NO.sub.3(aq) Calculated from the Modified Adsorption Isotherm Model for Aqueous Electrolytes. Sep Sci Technol 2006; 41(11): 2629-2634. https//doi:10.1080/01496390600743045 .sup.aEquation of the equilibrium constant is Ink = A + B/T + C/T.sup.2.
[0115] Based on the values of the activities ai and aw of the modified BET model and the natural logarithm of the equilibrium constant Ink, the solubility and composition of the eutectic points of the systems are calculated by means of a calculation program. The results found can be better expressed in relative amounts as in the weight fraction scale. The calculation program also allowed the construction of the solid-liquid phase diagrams of the following 10 systems/mixtures: LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiCl—LiNO.sub.3—LiClO.sub.4—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Ca(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NaNO.sub.3—Ca(NO.sub.3).sub.2—H.sub.2O, NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, NaNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2 and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O.
[0116] The mixtures were prepared following the mass ratio (compositions) of Table 9, and the eutectic mixtures were tested as PCM when it was confirmed that the expected values coincided with the values obtained from the experimentation, in the mixture being tested, and finally characterized by the properties of eutectic mixtures. See Table 9.
[0117] In addition to the mixtures with eutectic compositions and the eutectic point, the equations of the thermodynamic model were used for the construction of phase diagrams of quaternary systems of each mixture. The polythermic lines and the isotherms expected for each system/mixture, allowed to establish the eutectic composition as the point of intersection of the three polythermic lines (see
[0118] Mixtures LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, They were tested in three compositions (A, B and C) that were close to the eutectic point (e) to compare the results with those of the eutectic quaternary mixture and use the information for the other mass relationships with the same components.
[0119] In summary, from the modified BET model, 10 mixtures of quaternary systems were defined that were LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiCl—LiNO.sub.3—LiClO.sub.4—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Ca(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NaNO.sub.3—Ca(NO.sub.3).sub.2—H.sub.2O, NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, NaNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O for conditioning of environments in a range of 0 to 15° C. The expected phase change temperatures were 10.8° C., 3.4° C., 10.8° C., 8.9° C., 7.9° C., 16.4° C., 13° C., 20.6° C., 13.6° C. and 5.7° C., respectively. Phase diagrams were designed for the ten quaternary systems with the equations of the modified BET model.
[0120] Only 5 of the mixtures are eutectic, LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O. Two of the five eutectic samples were tested, LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O. For the eutectic composition (e) found with a modified BET model, and for three points close to this (A, B and C) for two of the quaternary systems, LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, confirming the eutectic composition. From the T-history method it was determined that the behavior of both mixtures with composition e had the characteristic behavior of a compound with eutectic composition, unlike the mixtures, whose compositions were defined with the points A, B and C.
[0121] The subcooling present in the mixtures, by the T-history method, was 3.0, 2.7, 7.5, 3.4 and 2.9 LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O, respectively. Subcooling could be exceeded or decreased for a TES system application where large amounts of material are required. For applications where small amounts of PCM are required, it would be necessary to use nucleating agents.
[0122] The heat of fusion of the five mixtures was 172.5 kJ.Math.kg.sup.−1 to LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, 169.8 kJ.Math.kg.sup.−1 to LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, 152.8 kJ.Math.kg.sup.−1 to LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, 187.6 kJ.Math.kg.sup.−1 to LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and 142.2 kJ.Math.kg.sup.−1 to LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O. The heat of crystallization of the mixtures was 157.7 kJ.Math.kg.sup.−1 to LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, 136.0 kJ.Math.kg.sup.−1 to LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, 133.4 kJ.Math.kg.sup.−1 to LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, 162.6 kJ.Math.kg.sup.−1 to LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and 107.6 kJ.Math.kg.sup.−1 to LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O.
[0123] The solid state specific heat results for LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O showed an increase with temperature ranging from 1.538 to 2.379 J.Math.g.sup.−1K.sup.−1 in a range of temperature from 272.7 to 280.0 K, to LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O the values vary from 2.001 to 2.166 J.Math.g.sup.−1.Math.K.sup.−1 in a range of temperature from 247.2 to 259.9 K, to LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O the values increase from 1.227 to 2.038 J.Math.g.sup.−1.Math.K.sup.−1 in a range of temperature from 269.9 to 280.1 K, to LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O showing an increase that goes from 1.790 to 2.131 J.Math.g.sup.−1.Math.K.sup.−1 in a range of temperature from 250.5 to 265.1 K and to LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O the values vary from 2.304 to 1.946 J.Math.g.sup.−1.Math.K.sup.−1 in a range of temperature from 247.8 to 261.9 K. Further, specific heat experimental values of solid state were adjusted for the five eutectic mixtures.
[0124] Specific heat values were measured to liquid phase. To LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O in a range of temperature from 290.0 to 302.1 K with values of 2.500 to 2.583 J.Math.g.sup.−1.Math.K.sup.−1, to LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O in a range of temperature from 284.8 to 330.0 K with values of 2,892 to 3,174 J.Math.g.sup.−1.Math.K.sup.−1, to LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O in a range of temperature from 302.6 to 320.0 K with values of 2.600 to 2.446 J.Math.g.sup.−1.Math.K.sup.−1, to LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O in a range of temperature from 297.4 to 330.0 K with values of 2.961 to 2.585 J.Math.g.sup.−1.Math.K.sup.−1 and to LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O in a range of temperature from 284.3 to 330.0 K with values from 2,536 to 2,441 J.Math.g.sup.−1.Math.K.sup.−1.
[0125] The dinamic viscosity of the studied mixtures was 18.18, 12.30, 18.15, 11.45 and 21.43 cP to LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O, respectively.
[0126] The densisty of solid at 0° C. is 1.753, 1.679, 1.623 and 1.676 g.Math.cm.sup.−3 to LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O. respectively. While the density of solid to the mixture LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O obtained at −5° C. was 1.641 g.Math.cm.sup.−3.
[0127] The liquid density to eutectic mixtures was measured in a range of temperature between 25 and 45° C. and the values of density were found in the range from 1.65455 to 1.63891, 1.60102 to 1.57107, 1.63472 to 1.62144, 1.48125 to 1.46923 and 1.63005 to 1.61306 g.Math.cm.sup.−3 to LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O, respectively.
[0128] The volume change values were ΔV/N solid=4.9%, 4.2%, 2.1%, 2.0% and 0.4% to LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O, respectively.
[0129] The energy storage density was 302.4, 278.6, 256.6, 304.5 and 238.3 MJ.Math.m.sup.|3 to LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O, respectively. The energy storage density to the five quaternary eutetic mixtures is found near to the values of commercial compounds, which ranging from 162.4 to 259.9 Mj.Math.m.sup.−3 to ClimSel C10 and S10 (Commercial, PCM Products Ltd), respectively.
[0130] The results obtained from heat of fusion/crystallization, specific heat, density, and viscosity were shown to be adequate for the use of four mixtures as PCM in storage systems in the study range from 0 to 15° C. The mixture that must be discarded, for this application in this specific temperature range, is the mixture LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O due to its melting temperature is −1.1° C.
[0131] The most suitable PCM to be used in the solar energy-assisted AC system is LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O due to the results obtained in the characterizations, cost estimation and because its subcooling is lower than that of the other compounds studied at different volumes, as was the case with 15 mg in the DSC equipment (ΔT.sub.sub=25.2° C.) and 12.5 g in the device to the T-history (ΔT.sub.sub=3° C.).
[0132] All mixtures have potential for applications as thermal storage material, in systems, where the operating temperature range corresponds to the melting temperature of the PCM
Examples
[0133] The reagents used in the preparation of the eutectic mixtures were: LiNO.sub.3 purity+98.0% wt, NaNO.sub.3 purity+99.7% wt, Mg(NO.sub.3).sub.20.6H.sub.2O purity+99.5% wt, Mn(NO.sub.3).sub.2.4H.sub.2O purity+98.5% wt, NH.sub.4NO.sub.3 purity+95.0% wt, LiCl purity+99.0% wt, LiClO.sub.4.3H.sub.2O purity+98.0% wt, Ca(NO.sub.3).sub.2.4H.sub.2O purity+99.0% wt, ultra pure water.
[0134] The mixtures were prepared following the following protocol after washing and drying all the materials and utensils to be used (beakers, watch glasses, spatula), and letting them dry in an oven at 40° C., and performing the standard tasks associated with tare utensils for analytical balance measurements. A first salt is added to a beaker containing 100 mL of distilled water, and then a second salt different from the first, and then a third salt different from the first and second salts, the mixture is stirred at medium speed at a temperature of 30° C. for 1 hour and stir until all salts are dissolved. The amounts of the first, second and third salts and water are indicated in table 9.
TABLE-US-00009 TABLE 9 System/Mixturea T/(° C.) Mass relation LiNO.sub.3•3H.sub.2O:NaNO.sub.3:Mn(NO.sub.3).sub.2•6H.sub.2O 10.8 24.2:3.0:72.8 LiNO.sub.3•3H.sub.2O:NH.sub.4NO.sub.3:Mn(NO.sub.3).sub.2•6H.sub.2O 3.4 21.4:13.9:64.7 LiNO.sub.3•3H.sub.2O:Mn(NO.sub.3).sub.2•6H.sub.2O:Mg(NO.sub.3).sub.2•6H.sub.2O 10.8 22.9:68.6:8.5 LiNO.sub.3•3H.sub.2O:LiCl:LiClO.sub.4•3H.sub.2O 8.9 47.4:47.6:5.0 LiNO.sub.3•3H.sub.2O:NH.sub.4NO.sub.3:Ca(NO.sub.3).sub.2•4H.sub.2O 7.9 33.7:19.4:46.9 LiNO.sub.3•3H.sub.2O:NaNO.sub.3:Ca(NO.sub.3).sub.2•4H.sub.2O 16.4 39.5:4.2:56.3 NH.sub.4NO.sub.3:Mn(NO.sub.3).sub.2•6H.sub.2O:Mg(NO.sub.3).sub.2•6H.sub.2O 13 12.7:74.3:13.1 NaNO.sub.3:Mn(NO.sub.3).sub.2•6H.sub.2O:Mg(NO.sub.3).sub.2•6H.sub.2O 20.6 2.8:87.0:10.2 LiNO.sub.3•3H.sub.2O:NH.sub.4NO.sub.3:Mg(NO.sub.3).sub.2•6H.sub.2O 13.6 55.8:27.8:16.4 LiNO.sub.3•3H.sub.2O:Mn(NO.sub.3).sub.2•6H.sub.2O:Ca(NO.sub.3).sub.2•4H.sub.2O 5.7 17.7:55.3:27.0
[0135] The crystallization and melting tests of the mixtures were carried out by the T-history method. They were carried out in a LAUDA ECO RE 420 thermostatted bath with a LAUDA Kryo 30 cooling liquid. The diagram of the experimental cooling and heating equipment is shown in
[0136] For each of the samples found, a cooling/heating cycle was performed for the mixture. The thermostatted bath was programmed so that the temperature of the coolant decreases/increases in the range −30° C. and 30° C. at a rate of 6° C..Math.h.sup.−1. Between the cooling and heating stages, one isotherm was programmed at −30° C. for 2 hours and the second isotherm at 30° C. for a period of 2 hours.
[0137] For two of the mixtures, which exhibited verified eutectic composition as described below, additional heating/cooling tests were performed to demonstrate eutectic behavior. For this, in the phase diagram of the corresponding mixture, three additional points were defined (called A, B and C) with a composition close to the eutectic (e) obtained by the modified BET model. The validation of the composition was carried out in a LAUDA ECO RE 420 thermostatized bath with a LAUDA Kryo 30 cooling liquid following the procedure set forth below.
[0138] Inside the thermostatized bath, a 200 mL glass bottle was fixed in which a long aluminum tube was placed, which contained 12.5 g of the eutectic composition mixture, as well as the mixture of the three different compositions to the point. Eutectic A, B, or C. Two ±0.5° C. precision K-type thermocouples were used for the measurements, one dipped into the center of the mix and the other into the bath coolant. Temperature data was recorded with PCE Instruments model PCE-T 390 and retrieved and analyzed by computer. A cooling/heating cycle was carried out for the mixture of composition A, B or C. The equipment was programmed so that the temperature of the cooling liquid decreases and increases in the range −20° C. and 28° C., at a speed of 6° C..Math.h.sup.−1. Between the cooling and heating stages, one isotherm was programmed at −20° C. for 2 hours and the second isotherm at 28° C. for a period of 2 hours; fulfilling 20 hours of programming.
[0139] The presence of the shorter platform or the absence of it indicates the remoteness of the selected composition mixture from the eutectic composition mixture. This behavior would confirm if the composition of point (e) corresponds to a mixture of eutectic composition. The characterization of the thermal and physical properties was carried out for the mixtures of confirmed eutectic composition.
[0140] To determine the phase change temperatures, the latent heat of fusion and crystallization of the PCMs, a differential scanning calorimeter (DSC 204 F1 Phoenix NETZSCH with N2 atmosphere) was used. The tests were carried out under the protection of nitrogen at a constant gas volumetric flow of 20 mL.Math.min.sup.−1. The sample amount of the eutectic mixtures was approximately 15 mg. Two cooling/heating cycles were carried out in a temperature range that varies according to the melting and crystallization temperatures of each mixture, the ranges were −25-40° C., −50-20° C., −20-40° C., −40-60° C. and −50 20° C. to LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O, respectively. The cooling/heating rate was carried out at 5 K.Math.min.sup.−1. The results of the second cycle were recorded. Aluminum crucibles with a 25 μL capacity were used. The phase change temperature and latent heat of the sample were obtained by analyzing the curves measured by the DSC.
[0141] Analysis of the specific heat of the eutectic mixtures was carried out using the DSC method, during the heating step. Temperature range −10-30° C., −30-60° C., −10-60° C., −30 60° C. and −30-60° C. to LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O, respectively. The heating rate was 1 K.Math.min.sup.−1. Sapphire (monocrystalline alumina) was used as a reference material for specific heat measurements. In addition to measuring the Cp of eutectic mixtures, Cp adjustments were made for the solid and liquid phases and the best correlation was found.
[0142] The dynamic viscosity of all liquid mixtures was determined experimentally with a Schott-Gerate viscometer. The measurement is based on the time that the liquid elapses between two points in a Micro-Ostwald type capillary. The viscometer is automatic and requires 2 mL of liquid sample for its measurement.
[0143] The density of the solid phase quaternary eutectic mixtures was determined using a pycnometer with n-dodecane as displacement liquid. (Xia Y. Phase Diagram Prediction of the Quaternary System LiNO.sub.3—Mg(NO.sub.3).sub.2—NH.sub.4NO.sub.3—H.sub.2O and Research of Related Phase Change Material. Chinese J Inorg Chem 2012; 28(9):1873-1877). On the other hand, the density of the liquid phase was measured by an oscillation densimeter (Mettler Toledo model DE50). Density measurements were performed in triplicate for the solid and liquid phases.
[0144] To measure the density of the pure PCM, a METTLER TOLEDO model DE 50 density meter was used, which can measure densities in a range of 0 to 3 g.Math.cm.sup.−3. The resolution of this equipment is 1×10.sup.−5 g.Math.cm.sup.−3. The temperature range of the equipment is 4° C. to 70° C. Density measurements were carried out in triplicate for the following temperatures 25° C., 30° C., 35° C., 40° C. and 45° C. The amount of liquid sample introduced into the measuring cell was approximately 2 mL.
[0145] A pycnometer is a simple instrument, used to accurately determine the density of solids, it is a glass container equipped with a ground stopper with a capillary tube, whose volume (Vpic) and mass (mpic) are known at a given temperature. To calculate the density, n-dodecane was used as the displacement liquid.
[0146] To calculate the density of the PCM, the procedure was as follows: the empty and covered pycnometer (mpic) was weighed, the pycnometer filled with n-dodecane was weighed and covered (mpic+n-dod), a known mass of the PCM, then capped and weighed (mpic+dod+PCM). To calculate the density of the PCM at temperature, I calculate the displaced volume based on the previous measurements and using the mass of n-dodecane and its density, and from the volume, the density of the PCM was calculated, knowing its mass and dividing by the volume calculated as indicated.
[0147] The expansion of the volume during the melting process of the mixtures must be considered for the encapsulation of the PCM and its implementation in the thermal energy storage system. To estimate these parameters, the densities of solid and liquid samples were extrapolated to the melting point, determining the value of the decrease in density due to a phase change (Shamberger P J, Reid T. Thermophysical Properties of Lithium Nitrate Trihydrate from (253 to 353) K. J Chem Eng Data 2012; 57 (5): 1404 1411. https://doi.org/10.1021/je3000469). The expansion was estimated as the ratio θV/Vsolid and is expressed as a percentage.
[0148] One quantity that is of primary importance is the energy storage density (esd) of the PCM, which is the ratio of specific latent heat to density. PCMs with esd values >200 MJ.Math.m.sup.−3 are attractive because, due to a small change in temperature, they allow greater thermal energy storage than water, reducing costs. Therefore, it is imperative to know the density of any suggested PCM to assess its applicability for practical purposes (Minevich A, Marcus Y, Ben-Dor L. Densities of solid and molten salt hydrates and their mixtures and viscosities of the molten salts. J Chem Eng 2004; 49: 1451-1455. Https://doi.org/10.1021/je049849b). Energy storage density is calculated based on density and enthalpy. Total heat is also calculated based on enthalpy, the difference or range of operating temperature of the thermal energy system and thermal capacities of solid and liquid.
[0149] To the mixture LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, the experimental melting temperature was 10.8° C. and coincided with the value theoretically expected by the modified BET model and presented in the phase diagram (
[0150] The quaternary mixture LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O has a crystallization temperature of −3.1° C. and its melting temperature is −1.1° C., however the expected melting temperature is 3.4° C. The experimental results for the eutectic composition are shown in
[0151] The measurement of the melting temperature for the mixture LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O gave a value of 13.1° C., 2.3° C. above the expected value shown in
[0152] The LiCl—LiNO.sub.3—LiClO.sub.4—H.sub.2O quaternary mixture does not show crystallization or melting in the temperature range −30 to 30° C. Therefore, it is not a candidate to be used as PCM in the temperature range studied, which is from 0 to 15° C. The expected melting temperature is 8.9° C. The experimental results for the composition modeled in
[0153] The quaternary mixture LiNO.sub.3—NH.sub.4NO.sub.3—Ca(NO.sub.3).sub.2—H.sub.2O presents crystallization at 0.2° C. and irregular melting from −2.9° C. Therefore, it is not a candidate to be used as PCM in the temperature range studied, which is from 0 to 15° C. The predicted melting temperature is 7.9° C. Which is 10.9° C. higher than the experimental temperature. The experimental results for the composition modeled in
[0154] The quaternary mixture LiNO.sub.3—NaNO.sub.3—Ca(NO.sub.3).sub.2—H.sub.2O has a crystallization temperature of 2.4° C. and the melting temperature is 14.2° C. The temperature expected by the BET thermodynamic model, defined in
[0155] The NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O quaternary mixture has a crystallization temperature of 2.4° C. and the melting temperature is 6.2° C. The experimental results for the eutectic composition modeled in
[0156] The experimental results for the modeled eutectic composition of the quaternary mixture NaNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O are shown in
[0157] The quaternary mixture LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O has the crystallization temperature of 10.9° C. and the melting temperature of 11.6° C. The temperature expected by the modified BET model is 13.6° C. (
[0158] The quaternary mixture LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O has the crystallization temperature equal to 0.4° C. and the melting temperature is 7.1° C. The temperature expected by the modified BET model is 5.7° C. (
[0159] In addition to experimentally verifying the results of the thermodynamic modeling, the nucleation temperature, Tnucl, and the presence of subcooling were determined, defined as the difference between the crystallization and nucleation temperatures, (ΔT.sub.sub=Tcr−Tnucl). The values are summarized in Table 10.
TABLE-US-00010 TABLE 10 Summary of the experimental verification of the eutectic composition and the phase change temperature for the ten quaternary mixtures. Tf/ Tcr/ Tnucl/ ΔTsub/ Eutectic Mixture (° C.) (° C.) (° C.) (° C.) Composition LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O 10.8 8.2 5.2 3.0 Yes LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O −1.1 −3.1 −5.7 2.7 Yes LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O 13.1 10.0 2.5 7.5 Yes LiCl—LiNO.sub.3—LiClO.sub.4—H.sub.2O — — — — — LiNO.sub.3—NH.sub.4NO.sub.3—Ca(NO.sub.3).sub.2—H.sub.2O −2.9 0.2 0.2 0 — LiNO.sub.3—NaNO.sub.3—Ca(NO.sub.3).sub.2—H.sub.2O 14.25 2.4 2.4 0 — NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O 6.2 2.4 1 1.4 — NaNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O — — — — — LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O 12.0 10.9 7.5 3.4 Yes LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O 7.1 0.4 −2.5 2.9 Yes
[0160] Subcooling is a serious problem associated with hydrated salts. One of the variables that affect nucleation is the sample size (Garcia-Romero A, Diarce G, Ibarretxe J, Urresti A, Sala J M. Influence of the experimental conditions on the subcooling of Glauber's salt when used as PCM. 94 Sol Energy Mater Sol Cells 2012; 102: 189-195. Https://doi.org/10.1016/j.solmat.2012.03.003). This method presented the subcooling corresponding to the sample size used, which was 12.5 g.
[0161] By verifying the modified BET model (see Table 9) of the ten quaternary mixtures, only five of them were shown to be suitable to be used as PCMs, LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O. The following physical and thermal property characterizations apply to the five most suitable mixtures to be used as PCMs.
[0162] The eutectic point of two quaternary mixtures proposed by the modified BET model were tested with compositions other than the expected eutectic point (e). The compositions of A, B and C of the mixtures LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O is summarized in Table 11.
TABLE-US-00011 TABLE 11 Composition A, B and C of mixtures LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O. Mass relation System A B C LiNO.sub.3•3H.sub.2O:NaNO.sub.3:Mn(NO.sub.3).sub.2•6H.sub.2O 22.1:10.0:67.9 18.1:1.8:80.1 36.0:2.5:61.5 LiNO.sub.3•3H.sub.2O:Mn(NO.sub.3).sub.2•6H.sub.2O:Mg(NO.sub.3).sub.2•6H.sub.2O 20.9:63.1:16.0 17.5:73.3:9.2 30.0:65.0:5.0
[0163] The exothermic and endothermic behavior of LiNO.sub.3—NaNO.sub.3—Mn (NO.sub.3).sub.2—H.sub.2O for the mixtures with the compositions of the eutectic point and points A, B and C is shown in
[0164] Mixes with composition other than the expected point e (points A, B and C) practically lack the platform. The only exception is point C, which has a certain tendency to form the platform because it has the composition closest to the eutectic point compared to A and B. Therefore, it can be confirmed that the measured eutectic composition and melting temperature validate the expected value by the modified BET model.
[0165] The exothermic and endothermic behavior of LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O was demonstrated for the mixtures with compositions A, B and C are presented in
[0166] The thermophysical characterization of the 5 PCMs is provided below. The properties of quaternary mixtures are related to the values of the reactants that participate in the system/mixture. Table 12 shows the properties of the reagents present in the systems/mixtures.
TABLE-US-00012 TABLE 12 Properties of reagents LiNO.sub.3.Math.3H.sub.2O, NaNO.sub.3, Mg(NO.sub.3).sub.2 .Math. 6H.sub.2O, Mn(NO.sub.3).sub.2 .Math. 6H.sub.2O and some of its systems Hydrated Tm/ ΔHf/ ρ/ Cp/(J .Math. g.sup.−1 .Math. Salt (° C.) (kJ .Math. kg.sup.−1) (g .Math. cm.sup.−3) K.sup.−1) η/(cP) Source LiNO.sub.3•3H.sub.2O 30 296 1.610 (s, 1.73 (s, 4.80 Shamberger PJ, Reid T. Thermophysical 22° C.) 15° C.) (40° C.) Properties of Lithium Nitrate Trihydrate from 1.420 (I, 2.76 (I, (253 to 353) K. J Chem Eng Data 40° C.) 40° C.) 2012; 57(5): 1404-1411. https://doi.org/10.1021/je3000469; Cabeza LF, Castell A, Barrenechea C, Gracia A, Fernández Al. Materials used as PCM in thermal energy storage in buildings: A review. Renew Sust Energ Rev 2011; 15: 1675-1695. https://doi.org/10.1016/j.rser.2010.11.018 NaNO.sub.3 306 172 1.636 (s) 1.38 (s, — Cabeza LF, Castell A, Barrenechea C, Gracia 1.550 (I) 155° C.) A, Fernández Al. Materials used as PCM in 1.67 (I, thermal energy storage in buildings: A review. 312- Renew Sust Energ Rev 2011; 15: 1675-1695. 377° C) https://doi.org/10.1016/j.rser.2010.11.018. Mg(NO.sub.3).sub.2• 89.9 163 1.636 (s, 1.636(s, — Cabeza LF, Castell A, Barrenechea C, 6H.sub.2O 25° C.) 25° C.) Gracia A, Fernández Al. Materials used as 1.550 (I, 1.550(I, PCM in thermal energy storage in buildings: 94° C.) 94° C.) A review. Renew Sust Energ Rev 2011; 15: 1675-1695. https://doi.org/10.1016/j.rser.2010.11.018. Mn(NO.sub.3).sub.2• 37.1 115 1.738 (I, — — Cabeza LF, Castell A, Barrenechea C, 6H.sub.2O 20° C.) Gracia A, Fernández Al. Materials used as PCM in thermal energy storage in buildings: A review. Renew Sust Energ Rev 2011; 15: 1675-1695. https://doi.org/10.1016/j.rser.2010.11.018. LiCl 610 441 2070 (s) — — Alva G, Liu L, Huang X, Fang G. Thermal 1502 (I) energy storage materials and systems for solar energy applications. Renewable and Sustainable Energy Reviews 2017; 68: 693- 706. https://doi.org/10.1016/j.rser.2016.10.021. LiClO.sub.3 8.1 253 1720 (s) 2.88 (s) — Baumann H, Heckenkamp J. 3H.sub.2O 155 1530 (I) Latentwärmespeicher. Nachrichten Aus Chemie, Technik Und Laboratorium 1997; 45(11): 1075-1081. https://doi:10.1002/nadc.199700023 NH.sub.4NO.sub.3 169.6 — 1.725 — — Byju's the learning app https://byjus.com/chemistry/ammonium-nitrate/2016 [consultado 1 de octubre de 2019] Ca(NO.sub.3).sub.2• 42.6 140 1.82 (s) 1.46 (s) — Kenisarin M, Mahkamov K. Salt hydrates as 4H.sub.2O latent heat storage materials: Thermophysical properties and costs. Sol Energy Mater Sol Cells 2006; 145: 255-286. https://doi:10.1016/j.solmat.2015.10.029
[0167] The heats of crystallization and fusion of mixtures LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O eutectic composition were measured by DSC and are listed in Table 13.
TABLE-US-00013 TABLE 13 Heats and temperatures of melting and crystallization of eutectic mixtures measured in DSC. Tcr/ Tm/ Eutectic composition ΔHcrl ΔHml (° C.) (° C.) mixtures (kJ .Math. kg.sup.−1) (kJ .Math. kg.sup.−1) Tinitial Tpeak Tfin Tinicio Tpeak Tfin LiNO.sub.3—NaNO.sub.3— 157.7 172.5 −4.2 −7.5 −11.4 108 17.7 22.0 Mn(NO.sub.3).sub.2—H.sub.2O LiNO.sub.3—NH.sub.4NO.sub.3— 136 169.8 −42.2 −31.3 −25.9 −3.5 0.8 9.3 Mn(NO.sub.3).sub.2—H.sub.2O LiNO.sub.3—Mn(NO.sub.3).sub.2— 133.4 152.8 −14.8 −15.9 −18.1 13.5 19.5 25.2 Mg(NO.sub.3).sub.2—H.sub.2O LiNO.sub.3—NH.sub.4NO.sub.3— 162.6 187.6 −34.8 −31.8 −29.5 9.6 19.4 22.7 Mg(NO.sub.3).sub.2—H.sub.2O LiNO.sub.3—Mn(NO.sub.3).sub.2— 107.6 142.2 −28.2 −22.2 −14.2 4.6 11.5 15.4 Ca(NO.sub.3).sub.2—H.sub.2O
[0168]
[0169] It is common to observe the presence of subcooling in PCMs that have hydrated salts or their mixtures. The 5 PCMs mentioned above present a subcooling, ΔT, estimated on the basis of DSC measurements, as the difference between melting and crystallization temperatures (Tpeak), of 25.2° C., 43.0° C., 35.4° C., 51.2° C. and 33.7° C. to LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O, respectively.
[0170] It is common to observe the presence of subcooling in PCMs that have hydrated salts or their mixtures. The 5 PCMs mentioned above present a subcooling, ΔT, estimated on the basis of DSC measurements, as the difference between the temper. However, these values are high, compared to the results shown in Table 10, a decrease in subcooling was observed by increasing the amount of material analyzed (12.5 g vs 15 mg). A similar subcooling reduction was presented in previous works, where bischophyte (95% MgCl.sub.2H.sub.2O) was characterized with DSC, T-history methods and on the pilot scale melting and crystallization saturations. (Ushak S, Gutierrez A, Galleguillos H, Fernandez A G, Cabeza L F, Grágeda M. Thermophysical characterization of a by-product from the non metallic industry as inorganic PCM. Sol Energy Mater Sol Cells 2015; 132: 385-391. https://doi.org/10.1016/1.solmat.2014.08.042; Rathgeber C, Schmit H, Mitt L, Cabeza L F, Gutierrez A, Ushak S N et al. Enthalpy-temperature plots to compare calorimetric measurements of phase change materials at different sample scales. Journal of Energy Storage 2018; 15:32-38. https://doi.org/10.1016/j.est.2017.11.002; Gasia J, Gutierrez A, Peiro G, Miro L, Grageda M, Ushak S et al. Thermal performance evaluation of bischofite at pilot plant scale. Applied Energy 2015; 155:826-833. https://doi.org/10.1016/j.apenergy.2015.06.042).
[0171] Latent heat storage is closely related to sensible heat storage. On the one hand, before materials reach the temperature of the phase change, they use sensible heat to store energy. On the other hand, due to the extremely low thermal conductivity of phase change materials, the temperature difference in the internal area of the materials is huge, which will lead to the fact that when some parts start the phase transformation, the others have not yet reached the transition temperature. Therefore, specific heat is crucial in real applications. (Chen Y Y, Zhao C Y. Thermophysical properties of Ca(NO.sub.3).sub.2—NaNO.sub.3—KNO.sub.3 mixtures for heat transfer and thermal storage. Solar Energy 2017; 146:172-179. https://doi:10.1016/j.solener.2017.02.033).
[0172] Based on the DSC the specific heat of the eutectic mixtures was measured.
[0173] For solid samples, the specific heat shows an increase over a temperature range of 272.7 to 280.0 K with values of 1.538 to 2.379 J.Math.g.sup.−1.Math.K.sup.−1 to the mixture LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, the range of temperature 247.2 to 259.9 K with values of 2.001 to 2.166 J.Math.g.sup.−1.Math.K.sup.−1 to the mixture LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, the range of temperature 269.9 to 280.1 K of 1.227 to 2.038 J.Math.g.sup.−1.Math.K.sup.−1 to the mixture LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, the range of temperature 250.5 to 265.1 K with values of 1.790 to 2.131 J.Math.g.sup.−1.Math.K.sup.−1 to the mixture LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and the range of temperature 247.8 to 261.9 K with values of 2.304 to 1.46 J.Math.g.sup.−1.Math.K.sup.−1 to the mixture LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O.
[0174] Specific heat values for the liquid phase in a temperature range from 290.0 to 302.1 K with values from 2.500 to 2.583 J.Math.g.sup.−1.Math.K.sup.−1 to LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, in a range of temperature from 284.8 to 330.0 K with values from 2,892 to 3,174 J.Math.g.sup.−1.Math.K.sup.−1 to the mixture LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, in a range of temperature from 302.6 to 320.0 K with values from 2.600 to 2.446 J.Math.g.sup.−1.Math.K.sup.−1 to LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, in a range of temperature from 297.4 to 330.0 K with values from 2.961 to 2.585 J.Math.g.sup.−1.Math.K.sup.−1 to the mixture LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and in a range of temperature from 284.3 to 330.0 K with values from 2.536 to 2.441 J.Math.g.sup.−1.Math.K.sup.−1 to the mixture LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O. The adjustments of Cp solid is showed in Table 13.
TABLE-US-00014 TABLE 13 Adjustments of the quaternary eutectic mixtures is solid state. Quaternary systems Cp/J .Math. g.sup.−1 .Math. K.sup.−1 LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O y = −0.001x.sup.2 + 0.6152x − 92.066; R.sup.2 = 0.9675 LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O y = 0.0057x.sup.2 − 2.932x + 379.88; R.sup.2 = 0.9956 LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O y = −0.0006x.sup.2 + 0.3829x − 61.461; R.sup.2 = 0.9881 LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O y = 0.0003x.sup.2 − 0.1391x + 17.017; R.sup.2 = 0.9967 LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O y = 4 × 10.sup.−5x.sup.5 − 0.0492x.sup.4 + 24.984x.sup.3 − 6340.9x.sup.2 + 804535x − 4 × 10.sup.7; R.sup.2 = 0.9953
[0175] The dynamic viscosity of the five promising quaternary mixtures as PCMs is presented in Table 14.
TABLE-US-00015 TABLE 14 Dynamic viscosity of expected quaternary mixtures of eutectic composition. Mixture μ/cP LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O 18.18 ± 0.02 LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O 12.30 ± 0.25 LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O 18.15 ± 0.16 LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O 11.45 ± 0.23 LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O 21.43 ± 0.23
[0176] The solid phase density of the quaternary eutectic mixtures was measured at 0° C., with the exception of LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O which was measured at −5° C. and the liquid phase was measured at 25, 30, 35, 40 and 45° C. to the five quaternary eutectic mixtures. The results obtained are showed in Table 15.
TABLE-US-00016 TABLE 15 Densities (+std) of mixtures with eutectic composition. Mixtures T/(° C.) ρ/(g .Math. cm.sup.−3) Phase LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O 0 1.753 ± 2.1 × 10.sup.−2 Solid 25 1.65455 ± 0.3x × 10.sup.−4 Liquid 30 1.65212 ± 0.3 × 10.sup.−4 35 1.64769 ± 0.3 × 10.sup.−4 40 1.64328 ± 0.4 × 10.sup.−4 45 1.63891 ± 0.4 × 10.sup.−4 LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O −5 1.641 ± 0.9 × 10.sup.−2 Solid 25 1.60102 ± 3.2 × 10.sup.−4 Liquid 30 1.59156 ± 8.4 × 10.sup.−4 35 1.58608 ± 0.1 × 10.sup.−4 40 1.58274 ± 0.9 × 10.sup.−4 45 1.57107 ± 0.1 × 10.sup.−4 LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O 0 1.679 ± 1.4 × 10.sup.−2 Solid 25 1.63472 ± 7.9 × 10.sup.−4 Liquid 30 1.63441 ± 0.1 × 10.sup.−4 35 1.63010 ± 0.4 × 10.sup.−4 40 1.62568 ± 0.3 × 10.sup.−4 45 1.62144 ± 0.1 × 10.sup.−4 LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O 0 1.623 ± 8.3 × 10.sup.−2 Solid 25 1.48125 ± 2.5 × 10.sup.−4 Liquid 30 1.47869 ± 5.0 × 10.sup.−4 35 1.47493 ± 2.0 × 10.sup.−4 40 1.47324 ± 0.1 × 10.sup.−4 45 1.46923 ± 2.5 × 10.sup.−4 LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O 0 1.676 ± 8.0 × 10.sup.−2 Solid 25 1.63005 ± 8.5 × 10.sup.−4 Liquid 30 1.62851 ± 0.1 × 10.sup.−4 35 1.62356 ± 7.8 × 10.sup.−4 40 1.61634 ± 0.1 × 10.sup.−4 45 1.61306 ± 6.2 × 10.sup.−4
[0177] The density data in the liquid state in the temperature range from 20° C. to 45° C. are fitted as a linear function of temperature and are represented by the following linear relationships respectively:
LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, ρ/l (g.Math.cm.sup.−3)=−0.0011T+1.686
LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, ρ/l (g.Math.cm.sup.−3)=−0.0012T+1.6238
LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, ρ/l (g.Math.cm.sup.−3)=−0.0008T+1.6575
LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O, y ρ/l (g.Math.cm.sup.−3)=−0.0006T+1.4943
LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O, ρ/l (g.Math.cm.sup.−3)=−0.0012T+1.6571
[0178] Volume expansion during melting of mixtures LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2—H.sub.2O, LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2—H.sub.2O and LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2—H.sub.2O was ΔV/Vsolid=4.9%, 4.2%, 2.1%, 2.0% and 0.4%, respectively. Such values were similar to the established ones to salt hydrates or mixtures (Minevich A, Marcus Y, Ben-Dor L. Densities of solid and molten salt hydrates and their mixtures and viscosities of the molten salts. J Chem Eng 2004; 49:1451-1455. https://doi.org/10.1021/je049849b).
[0179] The design and thermophysical characterizations of the five mixtures were carried out to be applied in water storage tanks coupled to a solar-assisted AC system installed in a building. The melting temperatures of the 5 mixtures were adequate to achieve the operation of the chilled water storage tanks at a temperature between 0 and 15° C., with the exception of LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2—H.sub.2O whose melting temperature is lower than the desired temperature range.
[0180] When designing a material for TES, it is important to know its properties and storage costs. In this sense, the calculation of the total heat was carried out. The results are presented in Table 16 for each of the 5 mixtures, which were compared with four commercial mixtures at similar melting temperatures, obtaining values close to those of their commercial competitors.
TABLE-US-00017 TABLE 16 Stored energy Mixtures having T/ ρ/ ΔH/kJ .Math. Cp/J .Math. Q total/ esd/ eutectic composition ° C. g .Math. cm.sup.−3 kg.sup.−1 g.sup.−1 .Math. K.sup.−1 kJ .Math. kg.sup.−1 MJ .Math. m.sup.−3 LiNO.sub.3—NaNO.sub.3—Mn(NO.sub.3).sub.2— 10.8 1.753 157.7 (cr) 1.538 (s, 199.6 302.4 H.sub.2O 172.5 (m) 272.7 K) 2.489 (I, 290.0 K) LiNO.sub.3—NH.sub.4NO.sub.3—Mn(NO.sub.3).sub.2— −1.1 1.641 136.0 (cr) 2.166 (s, 228.8 278.6 H.sub.2O 169.8 (m) 259.9 K) 3.174 (I, 330 K) LiNO.sub.3—Mn(NO.sub.3).sub.2—Mg(NO.sub.3).sub.2— 13.1 1.679 133.4 (cr) 1.227 (s, 173.8 256.6 H.sub.2O 152.8 (m) 269.9 K) 2.600 (I, 302.6 K) LiNO.sub.3—NH.sub.4NO.sub.3—Mg(NO.sub.3).sub.2— 12.0 1.623 162.6 (cr) 2.131 (s, 222.1 304.5 H.sub.2O 187.6 (m) 265.1 K) 2.961 (I, 297.4 K) LiNO.sub.3—Mn(NO.sub.3).sub.2—Ca(NO.sub.3).sub.2— 7.1 1.676 107.6 1.946 (s, 175.3 238.3 H2O (cr) 261.9 K) 142.2 2.441 (m) (I, 330 K) S8 (Commercial, 8 1.475 130 1.90 158.5 191.8 PCM Products Ltd) S10 (Commercial, 10 1.470 170 1.90 198.5 249.9 PCM Products Ltd) S13 (Commercial, 13 1.515 150 1.90 178.5 227.3 PCM Products Ltd) ClimSel C10 11 1.4 116 — — 162.4