Response-Specific Applicability of Equivalent Thermal Models for 3D-Printed Ribbed Wall Envelopes

Equivalent thermal calculations describe mean heat transfer, but their accuracy may not extend to local thermal-bridge responses in 3D-printed ribbed walls. We compared the ISO 6946 path-layer method with two-dimensional finite-volume solutions for 2700 dry, steady, insulation-filled periodic cells. Four geometry and conductivity parameters were varied at fixed wall thickness, matrix conductivity, and surface resistances. Numerical benchmarks, mesh checks and ANSYS APDL cross-checks of five selected cases (resistance differences within 0.14%) assessed implementation. Experimental validation was not performed. Resistance error was within 5% for 72.2% of the full grid but for only 6.7% of a 75-case subset selected using literature-reported geometric and conductivity ranges. These proportions characterize the selected domains, not constructed-wall populations. The conductivity contrast at which the resistance error crossed 5% varied with geometry. Resistance errors also changed with wall scale and surface resistance. Sensitivity calculations with air cores used prescribed equivalent resistances without resolving cavity convection or radiation; ISO cavity-geometry compliance was not confirmed. Within the full-grid 5% band, the peak-to-mean heat-flux ratio reached 2.72, and the equivalent model overpredicted minimum internal surface temperature by up to 3.21K. Global resistance accuracy is therefore not a proxy for local thermal accuracy: conditional error maps can screen resistance, but minimum surface temperature and peak heat flux need explicit-field assessment.