Sodium Acetate Trihydrate Phase Change Materials
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Solution Overview
Problem
Sodium acetate trihydrate phase change materials face limitations due to their incongruent melting behavior, resulting in the formation of solid sodium acetate during phase changes, which leads to thermodynamic instability and precipitation issues in thermal energy storage systems, making them unsuitable for long-term use in domestic heating applications.
Innovation Solution
The development of aqueous compositions containing sodium acetate trihydrate, combined with alkali soluble polymers to inhibit sodium acetate anhydrous crystal formation and nucleation promoters to promote stable nucleation, which enhances homogeneity and thermodynamic stability, preventing solid sodium acetate formation and maintaining a fully liquid state at 58°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If sodium acetate trihydrate is used as a phase change material, then the desired temperature range for domestic utility is achieved, but solid sodium acetate anhydrous precipitates during melting, causing thermodynamic instability
Solution Approach 1:
A soluble polymer intermediary is introduced to interact with sodium acetate anhydrous crystals during precipitation. The polymer binds to the crystals, preventing them from forming large stable precipitates and maintaining thermodynamic stability throughout the phase change process.
Solution Approach 2:
The solubility characteristics of sodium acetate are modified by changing the chemical environment through polymer addition. This alters the precipitation behavior of sodium acetate anhydrous, allowing it to remain in solution or form stable colloidal dispersions rather than separating as unwanted solid precipitate.
2Reliability
If three dimensional crosslinked polymers are used to support sodium acetate trihydrate, then initial solid formation is reduced, but solid sodium acetate still precipitates irreversibly at the base of the storage vessel over time
Solution Approach 1:
Instead of using crosslinked polymer supports, a soluble polymer intermediary is employed that actively binds to sodium acetate anhydrous crystals. This intermediary prevents irreversible precipitation by maintaining the crystals in a suspended or dissolved state throughout the service lifetime.
Solution Approach 2:
The chemical parameters of the system are changed by adding soluble polymer that modifies the solubility and precipitation behavior of sodium acetate, preventing the time-dependent irreversible settling that occurs with crosslinked polymer supports.
3Temperature
If sodium acetate trihydrate melts incongruently, then phase change occurs at 58°C, but a mixture of liquid SAT and solid sodium acetate is formed instead of a fully liquid solution
Solution Approach 1:
A soluble polymer intermediary is introduced that binds to sodium acetate anhydrous during the melting process. This prevents the formation of separate solid phases and promotes complete dissolution, resulting in a homogeneous liquid solution at the melting temperature.
Solution Approach 2:
The chemical environment is modified by polymer addition, which changes the melting behavior from incongruent (forming solid-liquid mixture) to congruent (forming homogeneous liquid). The polymer alters the solubility parameters, allowing complete liquid phase formation at 58°C.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The compositions demonstrate improved homogeneity and thermodynamic stability, preventing the formation of crystalline sodium acetate and maintaining a stable liquid state, even after repeated heating and cooling cycles, thus addressing the limitations of sodium acetate trihydrate in phase change systems.
Implementation Method 1
at least one alkali soluble polymer for inhibition of sodium acetate anhydrous crystal formation in sodium acetate trihydrate containing phase change materials
Implementation Method 2
at least one sodium acetate trihydrate nucleation promoter
Implementation Method 3
phase change materials (PCMs) to effect the energy conversion via their inherent solid-liquid phase changing properties
Implementation Method 4
sodium acetate trihydrate, (SAT), has a solid-liquid phase change within the desired temperature range for domestic utility
Data Source
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AI summary
There are herein described phase change materials containing sodium acetate trihydrate having improved homogeneity, a process for the preparation of said materials, and their utility in phase change systems. More particularly, the present invention relates to the use of phase change compositions comprising sodium acetate trihydrate, at least one alkali soluble polymer for inhibition of sodium acetate anhydrous crystal formation in sodium acetate trihydrate containing phase change materials, and at least one sodium acetate trihydrate nucleation promoter, and, if a lower phase change temperature is required, at least .one melting point depressing agent.