Question 11. When evaporation takes place at the liquid-vapor interface, the heat transfer is solely due to free convection and the film coefficient follows the relation

Question 12. A 0.10 cm diameter and 15 cm long wire has been laid horizontally and submerged in water at atmospheric pressure. The wire has a steady state voltage drop of 14.5 V and a current of 42.5 A. Determine the heat flux of the wire.
The following equation applies for water boiling on a horizontal submerged surface
H = 1.54 (Q/A)^0.75 = 5.58 (d t)³ W/m² K
where Q/A is the heat flux rate in W/m² and d t is the temperature difference between surface and saturation.

Question 13. Natural convection heat transfer coefficients over surface of a vertical pipe and a vertical flat plate for same height. What is/are the possible reasons for this?
(i) Same height
(ii) Both vertical
(iii) Same fluid
(iv) Same fluid flow pattern
Select the correct answer

Question 14. The heat flux in nucleate boiling varies in accordance with

Question 15. Fritz criterion is given by

Question 16. Condensation process is very common in
(i) Boilers
(ii) Condensers
(iii) Evaporators
Identify the correct statements

Question 17. Consider the following statements:
(i) If a condensing liquid does not wet a surface, then drop wise condensation will not take place on it
(ii) Drop wise condensation gives a higher transfer rate than film wise condensation
(iii) Reynolds number of condensing liquid is based on its mass flow rate
(iv) Suitable coating or vapor additive is used to promote film wise condensation
Identify the correct statement

Question 18. Depending upon the behavior of condensate up on the cooled surface, the condensation process are classified into how many distinct modes?

Question 19. The convective coefficients for condensation usually lie in the range

Question 20. Drop wise condensation usually occurs on