Phase Change Heat Storage with Active PCM Conveyance
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Solution Overview
Problem
Existing heat storage systems using phase change materials face challenges with low thermal conductivity, costly production, and limited temperature range, leading to inefficient heat transport and high costs due to the need for corrosive-resistant materials and complex heat exchanger designs.
Innovation Solution
A method and device utilizing unencapsulated phase change material with spatial separation between heat exchange and storage, employing a screw conveyor as both a conveyor and heat exchanger, allowing for active conveyance and heat exchange across varying phases, and using a single heat exchange device for both charging and discharging processes, thereby decoupling storage capacity from heat exchanger design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If phase change material is used for latent heat storage, then heat storage density is improved (10-20 times higher than sensible heat), but thermal conductivity is worsened (comparatively low thermal conductivity of 0.5 to 1 W/(m K))
Solution Approach 1:
The patent uses composite materials by combining phase change material particles with a carrier liquid that has higher thermal conductivity than the PCM itself. This composite structure maintains the high heat storage density of PCM while the carrier liquid matrix provides improved thermal conductivity for efficient heat transport throughout the storage volume.
Solution Approach 2:
The carrier liquid acts as an intermediary substance between the heat transfer fluid and the phase change material particles. It facilitates heat transfer from the heat exchange surfaces to the PCM particles, overcoming the low thermal conductivity of PCM while allowing the particles to maintain their high latent heat storage capacity.
2Reliability
If microencapsulation of phase change material is used, then heat transport is improved, but production complexity is worsened (complicated production of microcapsules)
Solution Approach 1:
The patent extracts the encapsulation step from the system by using unencapsulated phase change material particles directly in the carrier liquid. This eliminates the complex microencapsulation production process while maintaining effective heat transport through the particle-liquid composite structure and adequate mixing.
3Reliability
If stationary phase change material in steel tubes is used, then heat exchange is achieved, but cost is worsened (large amounts of high-quality materials such as corrosion-resistant steel required)
Solution Approach 1:
The heat transfer fluid acts as an intermediary that carries heat to and from the PCM particles suspended in the carrier liquid. This eliminates the need for extensive corrosion-resistant steel heat exchanger surfaces, as heat exchange occurs throughout the volume of the fluid-PCM mixture rather than only at tube surfaces.
Solution Approach 2:
The patent changes the physical state and arrangement of the phase change material from stationary enclosed form to mobile suspended particles. This allows the PCM to be actively circulated with the heat transfer fluid, enabling heat exchange throughout the entire storage volume rather than requiring large surface areas of expensive corrosion-resistant materials.
4Reliability
If coupling of storage capacity with heat exchanger surfaces is maintained, then heat exchange efficiency is improved, but device complexity is worsened
Solution Approach 1:
The patent introduces dynamic movement of the phase change material particles through active circulation with the heat transfer fluid. This dynamic approach allows heat exchange to occur throughout the entire storage volume during circulation, decoupling the heat exchanger size from the storage capacity and simplifying the overall device design.
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
This approach enables efficient heat storage and release across a wide temperature range (100°C to 300°C or higher), reducing costs and complexity by optimizing heat exchanger design independently of storage capacity, and allowing the use of previously limited PCM materials at higher temperatures.
Implementation Method 1
Heat accumulators which comprise a phase change material (phase change material, PCM) as the storage medium are particularly suitable for the efficient storage of heat or cold. Such latent heat accumulators have the advantage over other heat accumulators that large amounts of heat can be stored in a narrow temperature range.
Implementation Method 2
Compared to conventional sensible heat accumulators, high energy densities can be achieved with latent heat accumulators at a largely constant operating temperature. In comparison to conventional heat storage using sensible heat, a ten to twenty times higher heat storage density can be achieved with typical latent heat storage systems through a temperature change of 10 K during the phase change of the storage medium.
Implementation Method 3
during the phase change, the storage medium is actively conveyed and heat is supplied and/or dissipated at the same time
Data Source
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AI summary
The invention relates to a method for storing and releasing heat by means of a phase change material. In said method, a phase change is caused in a first heat exchanging device (4) by supplying heat during a charging process in a storage medium comprising a phase change material in order to store the heat as latent heat in the storage medium, and a phase change is caused in the storage medium while heat is dissipated during a discharging process in the first or another heat exchanging device (2). The invention is characterized in that at least predominantly non-encapsulated phase change material is used as storage medium, the storage medium is fed to the first heat exchanging device (4) as a fluid stream or particle stream during the charging process and is discharged when the phase change has been completed, the storage medium is fed to the first or another heat exchanging device (2) as a fluid stream during the discharging process and is discharged from the heat exchanging device as a fluid stream or particle stream when the phase change has been completed, the storage medium is temporarily stored in a first storage tank (1) following the charging process and/or in the first or another storage tank (3) following the discharging process, and the storage medium is actively conveyed and heat is exchanged during the phase change as the charging process and/or the discharging process take/s place. The invention further relates to an apparatus for storing and releasing heat by means of a phase change material.