HTTA 2018 02 16 Solutions

Pagina 1

Heat T ransfer and Thermal Analysis - A.Y. 2016/17 - Date 16/02/2018 Surname: Name: ID number: Signature: (“matricola” or person code) Part A 1. Write the Young equation, stating which quantities are indicated by the used symbols. 2. Draw the temperature profiles T (x) for the two fluids and write the expression of the logarithmic mean temper- ature difference (evidencing the involved temperatures in the drawing) for a co-current parallel-flow double-pipe heat exchanger if the cold fluid is undergoing a phase change. 3. Draw the temperature profile T(x) in the system (two solid layers + 1 fluid layer) depicted in the figure: 4. Write the Wien law and its meaning. 5. Define the irradiation and the radiosity quantities. 6. Put the following substances in correct ascending order of Prandtl number: air, water, a liquid metal, a very viscous mineral oil. 7. Sketch the Nukiyama curve stating the different phases. Heat T ransfer and Thermal Analysis - A.Y. 2016/17 - Date 16/02/2018 - Part B INSTRUCTIONS - Read them very carefully! • test duration is 1 h 35’. After 35’ part A will be collected. If you finish part A in a shorter time, you can immediately move to part B; • you must answer to part A questions in the spaces provided after the questions themselves; remember also to fill in all the fields (surname, name, progressive number, ...) on the part A paper; • for part B, you can use only one foolscap paper for the final copy (additional papers will not be collected). On top-left of the first page of the foolscap paper you have to write (in a large and well-readable way): – progressive number (this is the progressive alphabetical order number the teacher will give you in each test, not your “matricola” or person code). – surname – name – “matricola” or person code – signature The space at…