Heat Transfer Mock Test 8

1. The bubble diameter at the time of detachment from the surface can be worked out from the relation proposed by

2. What is the value of surface fluid constant for water-copper combination?

3. With increase in excess temperature, the heat flux in boiling

4. Estimate the peak heat flux for water boiling at normal atmospheric pressure. The relevant thermo-physical properties are
p _f (liquid) = 958.45 kg/m³
p _g (vapor) = 0.61 kg/m³
h _{f g} = 2.25 * 10 ⁶ J/kg
σ = 0.0585 N/m

5. Investigate the effect of following condition on the average value of heat transfer coefficient in flow through a tube
Two fold increases in flow velocity by varying mass flow rate
It may be presumed that there is no change in the temperature of the liquid and the tube wall, and that the flow through the tube is turbulent in character

6. For turbulent flow over a flat plate, the average value of Nusselt number is prescribed by the relation
Nu = 0.664 (Re) ^0.5 (Pr) ^0.33
Which of the following is then a false statement?
The average heat transfer coefficient increases as

7. In which type of boiling the temperature of the liquid exceeds the saturation temperature?

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

9. The temperature of the liquid is below the saturation temperature and boiling takes place only in vicinity of the heated surface. This type of boiling is known as

10. 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