Baffle Cut Effect on Shell and Tube Heat Exchanger Efficiency, Conjugated Heat Transfer

A detailed computational fluid dynamics investigation into the influence of baffle configuration on shell and tube heat exchanger performance, with specific focus on conjugated heat transfer effects. This study examines the complex relationship between thermal enhancement and hydraulic penalties associated with baffle implementation, providing valuable design insights for optimizing heat exchanger efficiency.

Heat Exchanger Configuration and Design Parameters

This simulation explores a shell and tube heat exchanger featuring aluminum baffles with a 36% cut ratio. The model incorporates conjugated heat transfer to accurately capture the thermal interaction between fluid domains and solid baffle structures, demonstrating how baffle thermal conductivity contributes to overall heat transfer enhancement.

Geometric Specifications

• Shell Dimensions: 600mm length, 90mm diameter
• Tube Arrangement: 7 tubes in triangular pattern, 20mm outer diameter
• Tube Spacing: 30mm center-to-center distance
• Baffle Configuration: 6 baffles with 4mm thickness
• Baffle Spacing: 86mm center-to-center distance
• Baffle Cut Ratio: 36% of shell diameter

Simulation Setup

• Mesh: Unstructured grid with 1,953,754 elements
• Near-Wall Treatment: Boundary layer mesh for appropriate y+ values
• Flow Conditions: Water at 300K entering shell side at 0.5 kg/m³
• Thermal Boundary: Constant tube wall temperature of 450K

Methodology and Physical Models

Material Properties

• Working Fluid: Water with temperature-dependent properties
• Property Definition: Piecewise-linear functions for density, viscosity, specific heat, and thermal conductivity
• Baffle Material: Aluminum with high thermal conductivity

Numerical Approach

• Solver Type: Pressure-based, steady-state simulation
• Turbulence Model: Realizable k-ε with standard wall functions
• Solution Algorithm: SIMPLE pressure-velocity coupling
• Discretization: First-order upwind schemes for momentum, energy, and turbulence parameters
• Initialization: Standard method with -0.7 m/s inlet velocity

Boundary Conditions

• Shell Inlet: Mass flow inlet at 300K
• Shell Outlet: Zero gauge pressure outlet
• Shell Wall: Adiabatic condition (zero heat flux)
• Tube Walls: Constant temperature at 450K
• Baffles: Solid aluminum with conjugated heat transfer

Results and Performance Analysis

Thermal Performance

• Exit Temperature: Shell-side fluid heated to approximately 360K
• Temperature Rise: 60K increase from inlet to outlet
• Heat Transfer Enhancement: Accelerated temperature diffusion due to baffle thermal conductivity
• Heat Transfer Coefficient: Convergence demonstrated with increasing iterations

Flow Characteristics

• Flow Pattern: Complex cross-flow arrangement induced by baffles
• Pressure Drop: Approximately 1 kPa across the heat exchanger
• Velocity Distribution: Increased local velocities in baffle-restricted regions

Conjugated Heat Transfer Effects

• Baffle Thermal Contribution: Enhanced temperature distribution through conductive heat paths
• Thermal Gradients: Visualization of temperature fields across fluid and solid domains
• Heat Transfer Mechanism: Combined convective and conductive pathways through strategic baffle placement

Engineering Implications

• Performance Trade-offs: Balance between thermal enhancement and hydraulic penalties
• Design Optimization: Insights into optimal baffle cut ratio and spacing
• Efficiency Considerations: Improved understanding of how baffle configuration affects overall heat exchanger performance

This comprehensive simulation demonstrates the significant impact of baffle design parameters on shell and tube heat exchanger efficiency, providing valuable guidance for thermal system designers seeking to optimize heat transfer performance while managing pressure drop constraints.