HTTA 2026 07 07 text with solutions

Page 1

Heat Transfer and Thermal Analysis - A.A. 2025/26 - Date 07/07/2026 VERY IMPORTANT: the answers must be written on the “Results” paper sheet, not on this text. Only the “Results” paper sheet must be uploaded and will be evaluated. NOTES: ˆStudents attending the 5 CFU course may have some different questions in part A. ˆFor the exercise queries, in case none of the multiple-choice answers the exercise matches the result you get, write your own result instead of marking an answer (so that in case we did a mistake and your answer is correct you can get the related points). ˆStudents having right to a test reduction should answer only to: all part A questions; queries 1, 2, 3 of the part B exercises. Part A 1) Considering a mesh for a CFD simulation, if the cell faces are aligned with the coordinate axes of the domain, the mesh is defined: ADynamic BOverset CUnstructured D*Structured 2) For a full sphere, homogeneous and isotropic, with heat source, exchanging heat by convection with a fluid at uniform temperature under steady-state conditions, the first integration constant obtained when integrating the one-dimensional Poisson equation is: A*Always zero. BAlways negative. CAlways positive. DPositive if the sphere radius is larger than the critical radius of insulation, negative otherwise. 3) A gray, diffuse, opaque surface having α= 0.7, areaA= 2m 2 and temperature 500 K receives an irradiation equal to 930 W/m2. The total power leaving such surface by radiation is: A6981 W B4961 W C*5519 W DThere are not enough data to calculate it. 4) The general form of the Laplace-Young equation reads: A∆P= 2σ / R B∆P=σ(1/R I −1/RII) C*∆P=σ(1/R I + 1/RII) D∆P=σ / R 5) The Weber number, used for convection with phase change, is defined as? A ρV wD2 C σ2 LV B* ρV w2DC σLV C µLw2D2 C σ3…