Thermal Accumulator Using Aqueous Formate Salt PCM
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Solution Overview
Problem
Existing thermal accumulators face issues with compatibility, safety, and efficiency due to the use of hydrogen peroxide and propylene glycol as phase change materials, which decompose, reduce thermal performance, and require subcooling for crystallization, limiting their stability and heat transfer rates.
Innovation Solution
An aqueous sodium formate solution is used as the phase change material, providing stability, non-corrosiveness, and enhanced thermal conductivity, allowing for efficient heat transfer and phase change without decomposition, and is compatible with metals for improved performance and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If hydrogen peroxide is used as PCM, then thermal storage capacity is achieved, but the PCM decomposes over time reducing thermal performance
Solution Approach 1:
The patent changes the chemical composition parameters of the PCM from hydrogen peroxide to an aqueous salt solution (sodium formate, potassium formate, or calcium formate). This parameter change eliminates the decomposition issue while maintaining the phase change thermal storage capability, thereby improving reliability without sacrificing thermal storage capacity.
2Quantity of substance
If propylene glycol is used as PCM, then thermal storage is achieved, but subcooling is required for crystallization reducing efficiency
Solution Approach 1:
The patent changes the PCM composition from propylene glycol to aqueous formate salt solutions. These formate brines exhibit superior crystallization characteristics without requiring subcooling, thereby improving operational ease while maintaining thermal storage capacity. The specific parameter change in chemical composition directly addresses the crystallization issue.
3Quantity of substance
If conventional PCMs are used, then thermal storage is achieved, but corrosion of metal walls occurs
Solution Approach 1:
The patent changes the chemical composition of the PCM to aqueous solutions of formate salts (sodium formate, potassium formate, or calcium formate). These salts are inherently non-corrosive to metals, eliminating the corrosion problem while preserving thermal storage capacity. This parameter change in chemical composition directly resolves the harmful effect on metal walls.
4Quantity of substance
If hydrogen peroxide or propylene glycol is used, then thermal storage is achieved, but heat transfer rates are limited
Solution Approach 1:
The patent changes the PCM from hydrogen peroxide or propylene glycol to aqueous formate salt solutions. These formate brines exhibit superior thermal conductivity and heat transfer characteristics, thereby improving heat transfer rates and productivity while maintaining thermal storage capacity.
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 sodium formate solution maintains thermal properties, offers higher heat transfer rates, and maintains a constant phase change temperature, making it suitable for both refrigeration and heating applications, especially in environments requiring temperature control for food or pharmaceutical products.
Implementation Method 1
The thermal accumulator is previously charged with a cooling load by circulating a coolant through the heat exchanger, making the PCM to change phase from liquid to solid
Implementation Method 2
The thermal accumulator can then refrigerate the environment in an autonomous manner by transferring the cooling load to the environment through heat exchange between the environment and the PCM through the external walls
Implementation Method 3
An aqueous sodium formate solution is used as the phase change material, providing stability, non-corrosiveness, and enhanced thermal conductivity, allowing for efficient heat transfer
Data Source
Figure 1
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Figure 4
AI summary
Thermal accumulator (1) comprising external walls (2) delimiting a closed storage space (3) that contains a PCM (4) and a heat exchanger (5) formed by a conduit for fluids arranged so that it exchanges heat with said PCM (4). The external walls (2) are made of metal. The PCM (4) is an aqueous salt solution comprising as a solute a salt selected from the group consisting in sodium formate, potassium formate, calcium formate and magnesium formate.