# Test: Free Convection Boiling

## 10 Questions MCQ Test Heat Transfer | Test: Free Convection Boiling

Description
Attempt Test: Free Convection Boiling | 10 questions in 10 minutes | Mock test for Chemical Engineering preparation | Free important questions MCQ to study Heat Transfer for Chemical Engineering Exam | Download free PDF with solutions
QUESTION: 1

### 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

Solution:

The functions f and f 2 depend upon the geometry of the heating surface.

QUESTION: 2

### Fritz criterion is given by

Solution:

Fritz formulated the following formula for water boiling at atmospheric pressure in free convection in a vertical tube headed from outside.

QUESTION: 3

### 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

Solution:

Q = E I = 616.25 W and A = 4.71 * 10 -4 m2.

QUESTION: 4

Consider the above problem, find the excess temperature of the wire

Solution:

1.54 (1.308 * 10 6) 2 = 5.58 (d t) 3.

QUESTION: 5

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

Solution:

The fluids must be same so their flow pattern.

QUESTION: 6

The heat flux in nucleate boiling varies in accordance with

Solution:

Q/A = δ f g [(p – p g) g/σ] 0.5 [C d t/h f g p C s f3.

QUESTION: 7

In nucleate pool boiling, the heat flux depends on

Solution:

The heat flux must depends on liquid properties material and condition of the surface.

QUESTION: 8

Identify the wrong statement with respect to boiling heat transfer?

Solution:

For boiling to occur, the heated surface must be exposed to a liquid and maintained at a temperature higher than the saturation temperature of the liquid.

QUESTION: 9

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

Solution:

(Q/A) = 0.18 p f g [σ (p – p g)/p 20.25.

QUESTION: 10

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

Solution:

(Q/A) MAX = 1480000 W/m2. Let E be the voltage at burnout. Then electric energy input to wire is E I = 195 E W.

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