HTTA 2024 07 09 text with solutions

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Heat Transfer and Thermal Analysis - A.A. 2023/24 - Date 09/07/2024 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 Students attending the 5 CFU courses may have some different questions in part A. 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 of the first part B exercise; queries 1, 2, 3 of the second part B exercise. Part A 1) Which of the following correlations can be for free convection convection over a plate? A NuD = C1ReC2 D PrC3 B NuD = C1GrC2 D PrC3 C* NuL = C1RaC2 L D NuL = C1PeC2 L BiC3 2) In steady-state, 1D, radial conduction conditions, the general temperature and heat flux profilesT(r) and ˙Q ′′ (r) in a homogeneous, hollow cylinder in which a heat source ˙U ′′′ is present read as (C1> 0): A T = ˙U ′′′ r2 4λ − C1ln(r) + C2, ˙Q ′′ = ˙U ′′′ r 2 + C1λ r B T = − ˙U ′′′ r2 4λ + C1ln(r) − C2, ˙Q ′′ =− ˙U ′′′ r 2 + C1λ r C T = − ˙U ′′′ r2 4λ + C1ln(r), ˙Q ′′ = ˙U ′′′ r 2 D* none of the other answers is correct 3) The net energy flux by radiation between two diffuse, gray, opaque facing planes can be expressed as: A ˙E ′′ 1,2 =−σ (T24−T14) 1 ε1 − 1 ε2 B* ˙E ′′ 1,2 =− σ (T24−T14) 1 ε1 + 1 ε2 − 1 C ˙E ′′ 1,2 =− (ε2−ε1)σ (T24−T14) D ˙E ′′ 1,2 =−σ (T24−T14) ε2−ε1 4) The Richardson dimensionless group is defined as: A* Ri = Gr Re2, where Gr and Re are the Grashof and Reynolds dimensionless groups, respectively B Ri =…