PCM in Shell and Tube Finned Heat Exchanger Simulation

A comprehensive computational fluid dynamics investigation of thermal energy storage using phase change materials (PCMs) within a finned shell and tube heat exchanger configuration. This simulation captures the complex transient behavior of PCM melting processes, demonstrating the effectiveness of latent heat storage systems for thermal management applications.

Thermal Energy Storage with Phase Change Materials

This simulation explores the dynamic thermal behavior of a shell and tube heat exchanger incorporating phase change materials as the storage medium. The study focuses on capturing the complex phase transformation process and associated heat transfer mechanisms that make PCMs valuable for thermal energy storage applications.

PCM Operating Principles

• Energy Storage Mechanism: Latent heat absorption during solid-to-liquid phase transition
• Energy Release Process: Heat dissipation during liquid-to-solid phase change
• Application Versatility: Thermal regulation in both heating and cooling systems
• Diurnal Cycle Utilization: Heat absorption during daytime and release during nighttime

Geometric Configuration and System Design

Heat Exchanger Architecture

• Shell Design: Cylindrical tank containing uniformly distributed PCM
• Heat Transfer Elements: Copper tube with winding path through PCM medium
• Enhancement Features: Cross-shaped copper fins along tube pathway
• Material Selection: Copper components for high thermal conductivity
• Tube Specifications: 0.001m wall thickness for efficient heat transfer

Computational Domain

• Mesh Characteristics: Unstructured grid with 2,448,380 elements
• Domain Regions: PCM volume, copper tube, copper fins, fluid flow path
• Boundary Definition: Interfaces between different materials and phases

Simulation Methodology and Physical Models

Phase Change Modeling Approach

• Model Selection: Solidification and Melting model for phase transition simulation
• Phase Transition Parameters:
  • Solidus temperature: 314.15K
  • Liquidus temperature: 317.15K
  • Latent heat of fusion: 255,000 J/kg

Material Properties

• PCM Characteristics: Paraffin with following properties:
  • Density: 750 kg/m³
  • Specific heat capacity: 2000 J/kg·K
  • Thermal conductivity: 0.2 W/m·K
  • Viscosity: 0.008 kg/m·s
• Heat Transfer Fluid: Water at 325.15K with 1.4973 kg/s mass flow rate
• Structural Components: Copper tubes and fins with high thermal conductivity

Numerical Approach

• Simulation Type: Transient analysis with 1200-second duration
• Time Step Configuration: Appropriate stepping for phase change capture
• Convergence Criteria: Suitable tolerances for energy and phase equations

Results and Performance Analysis

Thermal Evolution and Phase Transition

• Temperature Distribution: Visualization of thermal gradients throughout the storage medium
• Melting Front Progression: Tracking of solid-liquid interface movement over time
• Liquid Fraction Development: Quantification of PCM melting as a function of time
• Heat Transfer Effectiveness: Analysis of temperature rise near tube surfaces

System Performance Metrics

• Energy Storage Capacity: Evaluation of total thermal energy absorbed by PCM
• Charging Rate: Assessment of system response to heat input
• Thermal Gradients: Identification of temperature distribution patterns
• Fin Effectiveness: Contribution of extended surfaces to overall heat transfer

Engineering Insights

• Design Optimization: Guidance for fin placement and tube routing
• Operational Parameters: Influence of flow rate and inlet temperature
• System Response: Transient behavior during charging cycle
• Efficiency Considerations: Balance between thermal performance and material usage

This detailed simulation provides valuable insights into the dynamic behavior of PCM-based thermal energy storage systems, demonstrating how finned shell and tube configurations can effectively manage the inherent thermal conductivity limitations of phase change materials. The results highlight the potential of such systems for applications requiring efficient thermal energy storage and release cycles, including building climate control, solar thermal systems, and waste heat recovery.