Helical-Fin PCM Heat Exchanger Assembly for Lower-Cost Thermal Storage
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Solution Overview
Problem
Existing thermal storage systems using phase change materials (PCMs) in district heating networks face challenges such as low conductivity, high costs due to complex assembly and finned tube connections, and mechanical stress from PCM expansion, which hinder efficient heat transfer and increase system costs.
Innovation Solution
A thermal storage system (TSS) with a heat transfer fluid exchanger featuring helical fins on tubes and optimized plate design, allowing easy assembly and improved thermal conductivity by ensuring fins are partially inserted within the PCM volume, eliminating dead zones, and facilitating screwing of tubes into openings in the plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional finned tube heat exchangers are used in thermal storage systems, then heat transfer surface area is increased, but assembly complexity and manufacturing cost increase due to complex finned tube connections
Solution Approach 1:
The heat exchanger is divided into modular sections where tubes pass through plate openings, allowing independent assembly of plates and tubes. This segmentation eliminates the need for complex finned tube connections while maintaining heat transfer surface area through the plate-tube contact design.
Solution Approach 2:
The plate and tube are merged into an integrated assembly where the tube passes through the plate opening and is secured by the helical fin engagement. This merging simplifies the connection mechanism while maintaining effective heat transfer between the tube surface and the surrounding PCM through the plate structure.
2Reliability
If conventional heat exchanger assembly methods are used, then heat transfer functionality is achieved, but production cost increases due to complex assembly processes
Solution Approach 1:
The helical fin is pre-formed on the tube during manufacturing, and the plate openings are pre-positioned with sealing elements. This preliminary preparation allows for simple insertion and securing operations during assembly, reducing manufacturing complexity and cost while ensuring reliable heat transfer functionality.
Solution Approach 2:
The helical fin structure automatically engages with the plate opening geometry to secure the tube in position and provide sealing. This self-securing mechanism eliminates the need for additional fastening components or complex assembly operations, reducing production cost while maintaining heat transfer reliability.
3Quantity of substance
If PCM is stored in conventional heat exchanger configurations, then thermal energy is stored, but mechanical stress from PCM expansion causes structural issues
Solution Approach 1:
The plate structure provides localized support and stress distribution around the tube where PCM expansion occurs. The rigid plate material and its connection to the container structure create stress-relief zones that accommodate PCM volume changes during phase transition, preventing structural damage while maintaining thermal energy storage capacity.
Solution Approach 2:
The plate-tube assembly design incorporates flexible sealing elements and gap spaces between components that accommodate PCM expansion before stress builds up. This preliminary cushioning capacity prevents mechanical stress from reaching damaging levels during PCM phase change and volume expansion.
4Stability of the object's composition
If helical fins are fully inserted into plate openings, then structural stability is improved, but heat transfer efficiency decreases due to reduced convective flow
Solution Approach 1:
The helical fin is inserted partially into the plate opening rather than fully, providing just enough structural stability to secure the tube while leaving sufficient exposed fin surface area to maintain effective convective heat transfer with the PCM. This partial insertion optimizes the balance between mechanical stability and thermal efficiency.
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 TSS enhances heat exchange surface area, reduces mechanical stress, and lowers production costs by simplifying assembly, resulting in efficient and cost-effective thermal energy storage with improved conductivity and convective heat transfer.
Implementation Method 1
the exchange occurs between a heat transfer fluid circulating in the tubes and a PCM (progressive capacitor) that is fixed in the shell
Implementation Method 2
heat transfer fluid heat exchanger arranged at least partially in the container in contact with the PCM
Implementation Method 3
storage occurs via the phase change of a phase-change material. It is the enthalpy of phase change, most often during the solid/liquid phase transition, that is stored
Implementation Method 4
This energy, which is absorbed during melting and released during solidification, for example, results from the formation or breaking of interatomic or intermolecular bonds
Implementation Method 5
each tube comprising on its surface at least one helical fin wound helically along a longitudinal axis along which the tube extends
Data Source
Figure 1~2A
Figure 2B
Figure 3
AI summary
The invention relates to a phase change material (PCM) thermal storage system (TCS) comprising a container for holding a PCM and a heat transfer fluid heat exchanger arranged at least partially within the container in contact with the PCM. The heat exchanger comprises a bundle of parallel tubes for receiving a heat transfer fluid. Each tube has at least one helical fin wound helically along a longitudinal axis along which the tube extends. The system is characterized in that it comprises plates, each having an opening for each tube through which a tube is disposed, and in that the diameter of the openings is smaller than the diameter of the helical fin. The present invention relates to a PCM thermal storage system equipped with a heat transfer fluid heat exchanger and its assembly method.The field of the invention relates to Thermal Storage Systems (TSS) by Phase Change Materials (PCM); and more particularly, the integration of a heat exchanger with optimized geometry.