Q. The boiling process has wide-spread applications in

(i) Production of steam in nuclear and steam power plants for generation and for industrial processes and space heating
(ii) Absorption of heat in refrigeration and air-conditioning systems
(iii) Concentration, dehydration and drying of foods and materials

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

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Q. Which type of boiling occurs in steam boilers employing natural convection?

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Q. In which type of boiling the fluid motion is induced by external means?

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Q. 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

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

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Q. The phenomenon of stable film boiling is referred to as

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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

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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

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