HTTA 2024 01 17 Solutions

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Heat Transfer and Thermal Analysis - A.A. 2022/23 - Date 17/01/2024 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: ˆ For 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). ˆ Students having right to a test reduction should answer only to: all part A questions; part B questions 1 and 2; queries 1, 2, 3 of the first part B exercise; queries 1, 2 of the second part B exercise. Part A 1) In which of the following answers are the temperature and heat flux profiles correctly drawn, for a flat wall in steady-state conditions consisting of two layers, the one on the left with power generation and the other without, knowing that the left face of the wall is adiabatic while the face on the right exchanges by convection with a fluid? A B C D* None of the other answers is correct. 2) Concerning capillary phenomena, the Laplace - Young equation reads: A ∆P = σ/ (1/RI + 1/RII) B ∆P = σ (1/RI− 1/RII) C cosθ = σSA−σSL σLA D* None of the other answers is correct. 3) In which of the following answers are the substances correctly ordered according to increasing values of the Prandtl number? A viscous mineral oil - water - air - liquid metal B air - water - viscous mineral oil - liquid metal C* liquid metal - air - water - viscous mineral oil D air - water - liquid metal - viscous mineral oil 4) The most general form of the conduction equation for homogeneous, isotropic media with conductivity varying with temperature is: A λ∇2T + ˙U ′′′ = ρc∂T/∂τ B ∇2T + ˙U ′′′ /(ρc)…