Double-shell phase change heat storage balls with ceramic shell
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Solution Overview
Problem
Existing phase change heat storage materials, particularly those using aluminum or aluminum silicon alloys, face issues such as corrosion, leakage, low heat storage density, high production costs, and short cycle life due to chemical and physical reactions with container materials, as well as poor thermal shock stability.
Innovation Solution
A double-shell phase change heat storage ball design is developed, where metal balls are coated with an organic ignition loss and then encapsulated in sequential layers of alumina and mullite refractory slurries, allowing for in-situ packaging and controlled shell formation, preventing metal overflow and oxidation, and enhancing thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If aluminum or aluminum silicon alloy is used as phase change heat storage material, then high heat storage capacity is achieved, but corrosion and chemical reactions with container material occur
Solution Approach 1:
The patent applies composite materials by combining aluminum or aluminum silicon alloy core with ceramic shell materials (alumina, mullite, or other refractory ceramics). This creates a composite structure where the metal core provides high heat storage capacity while the ceramic shell provides corrosion resistance and chemical stability, resolving the contradiction between heat storage performance and corrosion resistance.
Solution Approach 2:
The ceramic shell acts as an intermediary layer between the aluminum alloy core and the external environment. This intermediate barrier prevents direct contact and chemical reactions between the corrosive metal and the container material or external environment, thereby protecting the system while maintaining the heat storage function of the metal core.
2Quantity of substance
If aluminum alloy material is used for heat storage, then high heat storage density is achieved, but medium leakage occurs during phase change
Solution Approach 1:
The composite structure with ceramic shell encapsulates the aluminum alloy core, creating a contained system that prevents leakage of molten metal or phase change materials. The ceramic shell serves as a containment barrier that maintains structural integrity during phase change cycles.
Solution Approach 2:
The ceramic shell functions as a protective envelope that encapsulates the phase change material. This shell structure prevents medium leakage while allowing the internal phase change process to occur, maintaining both containment and thermal functionality.
3Use of energy by moving object
If aluminum alloy is used in heat storage system, then high heat storage performance is achieved, but container housing is corroded during cycling
Solution Approach 1:
The ceramic shell serves as an intermediary protective layer between the aluminum alloy heat storage material and the container housing. During thermal cycling, this intermediate barrier prevents direct chemical and electrochemical reactions between the aluminum and the container, thereby preventing container corrosion while maintaining heat storage performance.
Solution Approach 2:
The patent converts the potentially harmful corrosive nature of aluminum into a beneficial configuration by using the aluminum core's high heat storage capacity while the ceramic shell manages the corrosion issue. The shell transforms the problematic interaction between aluminum and container into a controlled interface, protecting both components.
4Ease of manufacture
If aluminum silicon alloy powder is mixed with matrix material, then phase change heat storage function is achieved, but aluminum powder leaks and overflows after melting during roasting
Solution Approach 1:
The patent applies preliminary action by forming the aluminum alloy into a solid core structure before applying the ceramic shell coating. This pre-formed core prevents aluminum powder from leaking and overflowing during subsequent roasting operations, as the material is already contained within the shell structure.
Solution Approach 2:
The composite structure with metal core and ceramic shell prevents aluminum powder leakage during roasting. The ceramic shell acts as a containment barrier that holds the aluminum core in place, preventing it from melting and overflowing during the high-temperature roasting process.
5Manufacturing precision
If alumina shell is prepared for phase change heat storage microcapsule, then dense shell structure is achieved, but thermal shock stability is poor
Solution Approach 1:
The patent uses composite shell materials combining alumina with mullite or other refractory ceramics. This composite shell structure provides both density and improved thermal shock stability, as the combination of materials creates a more resilient structure that can withstand thermal cycling while maintaining structural integrity.
Solution Approach 2:
The patent modifies the shell material composition parameters by incorporating mullite or other refractory ceramics alongside alumina. This changes the thermal and mechanical properties of the shell, improving thermal shock stability while maintaining density through controlled composition ratios and sintering parameters.
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 double-shell design achieves high heat storage capacity, good thermal shock stability, long service life, and improved heat utilization rates, with a simple and controllable production process, and can withstand high temperatures, addressing the limitations of prior art.
Implementation Method 1
The phase change energy storage technology stores energy by using the property of absorbing and releasing heat during the phase change material state change. When the ambient temperature is higher than the phase change temperature, the phase change material melts or vaporizes and absorbs heat; on the contrary, when the ambient temperature is lower than the phase change temperature, the phase change material condenses or solidifies and releases heat
Implementation Method 2
Thorough utilization of the latent heat storage characteristics of the phase change material, various requirements of building temperature adjustment and energy conditioning, residual heat recovery and storage, auxiliary heat storage and solar heat storage can be achieved
Implementation Method 3
The organic ignition loss undergoes thermal decomposition and combustion at high temperature, releasing gases and forming pores in the shell structure
Implementation Method 4
The organic ignition loss undergoes thermal decomposition and combustion at high temperature, releasing gases and forming pores in the shell structure
Implementation Method 5
The alumina and mullite refractory slurries undergo sintering at high temperature, densifying the shell structure and forming a stable double-shell enclosure
Implementation Method 6
The paraffin undergoes melting at elevated temperature, expanding and being discharged through pores in the shell
Data Source
AI summary
A double-shell phase change heat storage balls and preparation method thereof is disclosed. The technical scheme is as follows. Paraffin is placed in oven, and organic ignition loss is added to obtain paraffin melt containing the ignition loss; metal balls is immersed in the paraffin melt containing the ignition loss, and cooled naturally to obtain the metal balls coated by ignition loss and paraffin; alumina refractory slurry is placed in a pan granulator, and the metal balls coated by ignition loss and paraffin is added, pelletized, and dried to obtain alumina composite phase change heat storage ball bodies; mullite refractory slurry is placed in a pan granulator, alumina composite phase change heat storage ball bodies is added, pelletized, dried, and placed in a muffle furnace. The temperature is raised to 1200-1600° C. by three systems and maintained. After naturally cooling, the double-shell phase change heat storage balls are prepared.