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Chapter:

Condensation-and-Boiling

1. Fritz criterion is given by


Hint Answer

2. The nucleate pool boiling is influenced by following factors
(1) Pressure
(2) Liquid properties
(3) Material
Identify correct statements


Hint Answer

3. An electric wire of 1.25 mm diameter and 250 mm long is laid horizontally and submerged in water at 7 bar. The wire has an applied voltage of 2.2 V and carries a current of 130 amperes. If surface of wire is maintained at 200 degree Celsius, make calculations for heat flux


Hint Answer

4. With increase in excess temperature, heat flux in boiling


Hint Answer

5. Estimate peak heat flux for water boiling at normal atmospheric pressure. The relevant rmo-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


Hint Answer

6. Maximum heat transfer rate in a modern boiler is about


Hint Answer

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


Hint Answer

8. The boiling phenomenon is known to occur in how many forms?


Hint Answer

9. Heat flux increases with temperature excess beyond Leiden-frost point due to


Hint Answer

10. Which of following parameters affect burnout heat flux in nucleate boiling region
(i) Heat of evaporation
(ii) Temperature difference
(iii) Density of vapor
(iv) Density of liquid
(v) Surface tension at vapor-liquid interface
Mark correct answer from codes indicated below


Hint Answer

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Topics

This Chapter Condensation-and-Boiling consists of the following topics

Condensation and Boiling

Fritz criterion is given by

;

The nucleate pool boiling is influenced by following factors
(1) Pressure
(2) Liquid properties
(3) Material
Identify correct statements

;

An electric wire of 1.25 mm diameter and 250 mm long is laid horizontally and submerged in water at 7 bar. The wire has an applied voltage of 2.2 V and carries a current of 130 amperes. If surface of wire is maintained at 200 degree Celsius, make calculations for heat flux

;

With increase in excess temperature, heat flux in boiling

;

Estimate peak heat flux for water boiling at normal atmospheric pressure. The relevant rmo-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

;

Maximum heat transfer rate in a modern boiler is about

;

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

;

The boiling phenomenon is known to occur in how many forms?

;

Heat flux increases with temperature excess beyond Leiden-frost point due to

;

Which of following parameters affect burnout heat flux in nucleate boiling region
(i) Heat of evaporation
(ii) Temperature difference
(iii) Density of vapor
(iv) Density of liquid
(v) Surface tension at vapor-liquid interface
Mark correct answer from codes indicated below

;