HTTA 2022 06 13 Solutions

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Heat Transfer and Thermal Analysis - A.A. 2021/22 - Date 13/06/2022 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 of the Nuclear Engineering programme (attending the 052603 - 5 CFU course) have some different questions in part A. ˆ Students having right to a test reduction should answer only to: all part A questions, the first 2 (two) part B questions, the first 3 (three) queries of the first part B exercise, the first 2 (two) queries of the second part B exercise. Part A 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 In steady-state, 1D, radial conduction conditions, the general temperature and heat flux profiles T(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 none of the other answers is correct C* T = − ˙U ′′′ r2 4λ + C1ln(r) + C2, ˙Q ′′ = ˙U ′′′ r 2 − C1λ r D T = − ˙U ′′′ r2 4λ + C1ln(r) − C2, ˙Q ′′ =− ˙U ′′′ r 2 + C1λ r 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 =− (ε2−ε1)σ(T24−T14) C* ˙E ′′ 1,2 =−σ(T24−T14) 1 ε1 + 1 ε2 − 1 D ˙E ′′ 1,2 =−σ(T24−T14) ε2−ε1 A full sphereS1 having radiusR1 = 25 mm is concentric with a spherical shellS2 having radius R2 = 50 mm. The view factorFS2→S1 from spherical shellS2 towards…