HTTA 2020 02 07 Solutions

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VER Y IMPOR T ANT Please read with great attention the instructions written at the beginning of the text of Part B. Not complying with them will result in a penalty . Heat T ransfer and Thermal Analysis - A.Y. 2018/19 - Date 07/02/2020 Surname: Name: ID number: Signature: (“matricola” or person code) Part A 1. Write the generic (before application of the b.c.s) temperature and heat flux profiles T (x) and ˙Q ′′ (x) for a hollow sphere with a heat source, for 1D steady-state conduction. 2. Write the Young equation for a drop resting on a surface. 3. Write the criterion commonly used to decide if convection is forced/free/mixed. 4. Write the cosine or Lambert law for radiation. 5. Sketch the Nukiyama curve stating the different heat transfer / boiling phases. 6. Sketch a vapour chamber. 7. Sort the following materials in ascending order of conductivity: stainless steel - air - copper - water - diamond Heat T ransfer and Thermal Analysis - A.Y. 2018/19 - Date 07/02/2020 - Part B INSTRUCTIONS Read them very carefully - Not complying with them will result in a penalty from -1 point to not having some parts of the test corrected. • test duration is 1 h 45’. The text of both exam parts is given at the beginning. The suggestion is to devote to part A no more than 35’. • you must fill in all the fields (surname, name, student ID number, signature) on part A sheet; • you must answer to part A questions in the spaces provided after the questions themselves; • for part B, you can use only one foolscap for the final copy (additional foolscap will not be collected/corrected); • on top-left of the first page of the foolscap paper for part B, you must write your pro- gressive number∗, surname, name, student ID number, signature. They must be written in a large and easily readable way and…