HTTA 2023 06 14 Solutions 5CFU

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Heat Transfer and Thermal Analysis - 5 CFU - A.A. 2022/23 - Date 14/06/2023 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 and 2 of the first part B exercise, queries 1, 2 and 3 of the second part B exercise. Part A 1) The 1D,T =T (r), Poisson equation in cylindrical coordinates can be written as: A 1 r2 ∂ ∂r ( r2∂T ∂r ) =− ˙U ′′′ λ B 1 r2 ∂ ∂r ( r2∂T ∂r ) = 0 C* 1 r ∂ ∂r ( r∂T ∂r ) =− ˙U ′′′ λ D 1 r ∂ ∂r ( r∂T ∂r ) = 0 2) In which of the following answers is the Stefan-Boltzmann law correctly written? A ρλ,T +αλ,T +τλ,T = 1 B λmax emission·T = const C ελ,T,↗ = αλ,T,↗ D* ˙E ′′ T =εTσT 4 3) Which of the following is usually true when considering temperatures or temperature ranges for thermal control? A ∆Toperating> ∆Tnon-operating> ∆Tsurvival B* ∆Toperating< ∆Tnon-operating< ∆Tsurvival C Toperating> Tnon-operating> Tsurvival D Toperating< Tnon-operating< Tsurvival 4) In which of the following answers are the temperature and heat flow 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 5) The general form of the Laplace-Young equation reads: A ∆P =…