Method for enhancing thermal energy storage performance of industrial grade hydrated salts based on phase change

1. A method for enhancing thermal energy storage performance of industrial grade hydrated salts based on phase change, comprising following steps, where a symbol “m 0 ” represents the mass of the aqueous system of industrial grade hydrated salts after being heated, and the numerical value of m0 is in a range of 10 gram (g)≤m 0 ≤100 kilogram (kg):

S 1 : heating an aqueous system of industrial grade hydrated salts containing industrial grade hydrated salt of 105-130% of m 0 by mass, and taking a sample No. 1 from the system for differential scanning calorimeter (DSC) testing when the mass of the aqueous system of industrial grade hydrated salts is reduced to m 0 , recording a melting enthalpy of sample No. 1 as ΔH 1 and the mass of the remaining industrial grade hydrated salts aqueous solution as m 1 ; or, heating and melting a recrystallized industrial grade hydrated salts system of mass m 0 , taking a sample No. 1 for DSC testing and recording the melting enthalpy of sample No. 1 as ΔH 1 and the mass of the remaining industrial grade hydrated salts system as m 1 ; and

S 2 : melting and adding water into, or melting and evaporating the residual aqueous system of industrial grade hydrated salts or the residual industrial grade hydrated salts system with the mass of m 1 in step S 1 to increase or decrease the mass by 0.4-0.8% m 0 , then taking a sample No. 2 from the residual system for DSC testing and recording the melting enthalpy of the sample No. 2 as ΔH 2 , and taking the mass of the residual aqueous system of industrial grade hydrated salts or residual industrial grade hydrated salts system as m 2 ; then repeating the melting and adding water or melting and evaporating process until a melting enthalpy ΔH n of a sample No. n that taken from the residual aqueous system of industrial grade hydrated salts or residual industrial grade hydrated salts system with a mass of m n satisfies ΔH 2 < . . . <ΔH n >ΔH n+1 , or the difference between ΔH n and ΔH GR is in a range of −5-5 Joule (J/g), where the residual aqueous system of industrial grade hydrated salts or the residual industrial grade hydrated salts system with the mass of m n is confirmed to be a desired industrial hydrated salts system with improved phase change thermal energy storage performance, with ΔH n being the melting enthalpy of sample No. n+1, and ΔH GR being the melting enthalpy of superior purity hydrated salts, n≥2.

2. The method according to claim 1 , wherein the method comprises:

S 21 : melting and evaporating the residual aqueous system of industrial grade hydrated salts or residual industrial grade hydrated salts system of mass m 1 in step S 1 until the mass is reduced by 0.4 to 0.8% of m 0 , taking the sample No. 2 from the residual system for DSC testing and recording the melting enthalpy of the sample No. 2 as ΔH 2 , and taking the mass of the residual aqueous system of industrial grade hydrated salts or residual industrial grade hydrated salts system as m 2 ; and

S 22 : when ΔH 1 <ΔH 2 , continuing melting and evaporating the residual industrial grade hydrated salt aqueous solution system or the residual industrial grade hydrated salt system with mass m 2 until the mass is reduced by 0.4 to 0.8% of m 0 , repeating S 21 until the melting enthalpy ΔH n of the sample No. n that taken from the residual aqueous system of industrial grade hydrated salts or residual industrial grade hydrated salts system with a mass of m n satisfies ΔH 1 <ΔH 2 < . . . <ΔH n >ΔH n+1 , or the difference between ΔH n and ΔH GR is in the range of −5-5 J/g, where the residual aqueous system of industrial grade hydrated salts or the residual industrial grade hydrated salts system with the mass of m n is confirmed to be an industrial hydrated salts system with improved phase change thermal energy storage performance, with ΔH n being the melting enthalpy of sample No. n+1, n≥2.

3. The method according to claim 1 , wherein the method comprises:

S 21 : the residual aqueous system of industrial grade hydrated salts or residual industrial grade hydrated salts system of mass m 1 in step S 1 is subjected to melting and evaporating to reduce the mass by 0.4 to 0.8% of m 0 , after which a sample No. 2 is taken from the system for DSC testing, the melting enthalpy of this sample No. 2 is recorded as ΔH 2 and the mass of the residual aqueous system of industrial grade hydrated salts or residual industrial grade hydrated salts system is recorded as m 2 ; and

S 22 : when ΔH 1 >ΔH 2 , the residual industrial grade hydrated salts aqueous system or the residual industrial grade hydrated salts system with mass m 2 is subjected to melting and diluting with water to increase the mass of the system by 0.4-0.8% of m 0 , and then melting and diluting with water is repeated until the melting enthalpy ΔH n of the sample No. n that taken from the residual industrial grade hydrated salts aqueous system or the residual industrial grade hydrated salts system with mass m n satisfies ΔH 2 <ΔH 3 < . . . <ΔH>ΔH n+1 , or the difference between ΔH n and ΔH GR is in the range of −5 to 5 J/g, where the residual aqueous system of industrial grade hydrated salts or the residual industrial grade hydrated salts system with the mass of m n is confirmed to be an industrial hydrated salts system with improved phase change thermal energy storage performance, with ΔH n being the melting enthalpy of sample No. n+1, n≥3.

4. The method according to claim 1 , wherein the method comprises:

S 21 : the residual aqueous system of industrial grade hydrated salts or residual industrial grade hydrated salts system of mass m 1 in step S 1 is subjected to melting and diluting with water to increase the mass by 0.4-0.8% of m 0 , after which the sample No. 2 is taken for DSC testing and the melting enthalpy of the sample No. 2 is recorded as ΔH 2 and the mass of the residual aqueous system of industrial grade hydrated salts or residual industrial grade hydrated salts system is recorded as m 2 ; and

S 22 : when ΔH 1 <ΔH 2 , the residual aqueous system of industrial grade hydrated salts or the residual industrial grade hydrated salts system with mass m 2 is subjected to melting and diluting with water to increase the mass of the system by 0.4-0.8% of m 0 , and then the step S 21 is repeated until the melting enthalpy ΔH n of the sample No. n that taken from the residual aqueous system of industrial grade hydrated salts or the residual industrial grade hydrated salts system with mass m n satisfies ΔH 1 <ΔH 2 < . . . <ΔH n >ΔH n+1 , or the difference between ΔH n and ΔH GR is in the range of −5 to 5 J/g, where the residual aqueous system of industrial grade hydrated salts or the residual industrial grade hydrated salts system with the mass of m n is confirmed to be an industrial hydrated salts system with improved phase change thermal energy storage performance, with ΔH n being the melting enthalpy of sample No. n+1, n≥2.

5. The method according to claim 1 , wherein the method comprises:

S 21 : the residual industrial grade hydrated salt aqueous solution system or residual industrial grade hydrated salt system of mass m 1 in step S 1 is subjected to melting and diluting with water to increase the mass by 0.4-0.8% of m 0 , after which the sample No. 2 is taken for DSC testing and the melting enthalpy of the sample No. 2 is recorded as ΔH 2 and the mass of the residual industrial grade hydrated salt aqueous solution system or residual industrial grade hydrated salt system is recorded as m 2 ; and

S 22 : when ΔH 1 >ΔH 2 , the residual industrial grade hydrated salt aqueous solution system or the residual industrial grade hydrated salt system with mass m 2 is subjected to melting and evaporating until the mass of the system is reduced by 0.4-0.8% m 0 ; then the melting and evaporating is repeated until the melting enthalpy ΔH n of the sample No. n that taken from the residual industrial grade hydrated salt aqueous solution system or the residual industrial grade hydrated salt system with mass m n satisfies ΔH 2 <ΔH 3 < . . . <ΔH n >ΔH n +1, or the difference between ΔH n and ΔH GR is in the range of −5 to 5 J/g, where the residual aqueous system of industrial grade hydrated salts or the residual industrial grade hydrated salts system with the mass of m n is confirmed to be an industrial hydrated salts system with improved phase change thermal energy storage performance, with ΔH n being the melting enthalpy of sample No. n+1, n≥3.

6. The method according to claim 1 , wherein the heating or heating and melting in step S 1 is carried out at temperatures in a range of 95 to 125 degree Celsius (° C.).

7. The method according to claim 1 , wherein the industrial grade hydrated salts include any one selected from, a group of, bischofite, sodium acetate trihydrate, calcium chloride hexahydrate, magnesium nitrate hexahydrate.

8. The method according to claim 7 , wherein the industrial grade hydrated salt is bischofite.

9. The method according to claim 1 , wherein the mass of any of the sample from sample No. 1 to sample No. n+1 is in a range of 0.1 g to 0.3 g.

10. The method according to claim 1 , wherein the method further comprises: dissolving an industrial bischofite of a mass of 105-130% m 0 in water, and then filtering the water dissolved with industrial bischofite to form the aqueous system of industrial grade hydrated salts.

11. The method according to claim 1 , wherein the method further comprises: heating the aqueous system of industrial grade hydrated salts to above 95° C. and evaporating the aqueous system of industrial grade hydrated salts with constant stirring to reduce its mass to m 0 .