Thermal performance of SWCNTs-water enclosed by partially heated cavity: Deformation process with original geometric proportions

This study investigates the thermal behaviour of a nanofluid within a deformable parallelogram-shaped cavity, where the enclosure undergoes angle-based deformation while retaining its original geometric proportions. The left sidewall, which forms different angles with the y-axis, is partially heated to provide thermal energy to the cavity, while the remaining walls are adiabatic and cold. Using water as the base fluid with suspended single-walled carbon nanotubes (SWCNTs), the system is modelled via nonlinear partial differential equations and solved numerically using the finite element method. Key parameters: including the skew angle (−60^°≤α≤60^°), nanoparticle concentration (0≤ϕ≤0.2), Rayleigh number (10⁴≤Ra≤10^6.5), and heated segment length (0.2≤h≤1) are analysed to assess their impact on fluid flow and thermal performance. Results demonstrate that cavity deformation significantly enhances heat transfer, with fluid velocity peaking at higher inclination angles. A comparison with existing experimental studies validates the isothermal behaviour predictions. The isotherms indicate that convection becomes increasingly dominant at larger deformation angles and higher Rayleigh numbers. Furthermore, the strength of natural convection around the partially heated segment varies significantly with the deformation angle. This work provides valuable insights for optimizing thermal systems with deformable enclosures and nanofluid applications.