Q. For water evaporating at atmospheric pressure, the burnout occurs at temperature excess slightly above

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

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Q. 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

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Q. Fritz criterion is given by

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Q. 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.

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Q. 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

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Q. The heat flux in nucleate boiling varies in accordance with

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Q. In nucleate pool boiling, the heat flux depends on

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Q. Identify the wrong statement with respect to boiling heat transfer?

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Q. 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 * 10⁶ J/kg
σ = 0.0585 N/m

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Q. A 1.0 mm diameter and 300 mm long nickel wire is submerged horizontal in water at atmospheric pressure. At burnout, the wire has a current of 195 A. Calculate the voltage at burnout. The relevant thermos-physical properties are

p f (fluid) = 959.52 kg/m³
p g (vapor) = 0.597 kg/m³
h f g = 2257000 J/kg
σ = 0.0533 N/m

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Q. Condensation refers to a change from the

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Q. Condensation process is very common in

(i) Boilers
(ii) Condensers
(iii) Evaporators

Identify the correct statements

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Q. The convective coefficients for condensation usually lie in the range

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Q. Drop wise condensation usually occurs on

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Q. 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

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

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Q. A plate condenser was designed to be kept vertical. How would the condensation coefficient be effected if due to site constraints, it has to be kept at 60 degree to the horizontal?

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Q. Saturated steam is allowed to condense over a vertical flat surface and the condensate film flows down the surface. The local coefficient of heat transfer for condensation

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Q. In condensation over a vertical surface, the value of convection coefficient varies as

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