Abstract: A method and system of thermal computational fluid dynamics (CFD) analysis on a structure. A thermal CFD model of the structure is created using 3D-CAD software in which a volume of the structure, encompassing a third part, a portion of a first part which is adjacent to and includes a boundary between the first and third parts, and a portion of the second part which is adjacent to and includes a boundary between the second and third parts, is replaced by a notional fourth part. Thermal-CFD analysis of the thermal CFD model is performed using thermal conductivity of a fourth part that is calculated, based on known thickness of the fourth part, known thickness, the derived shape and known value of the thermal conductivity of the third part, and known values of the thermal conductivity of portions of the first and second parts.