Explore topic-wise MCQs in Chemical Engineering.

This section includes 640 Mcqs, each offering curated multiple-choice questions to sharpen your Chemical Engineering knowledge and support exam preparation. Choose a topic below to get started.

1.

Hot water (0.01 m /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m/min) of density 800 kg/m and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately

A. 32
B. 37
C. 45
D. 50
Answer» B. 37
Discussion
2.

A process stream of dilute aqueous solution flowing at the rate of10 Kg.s is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s. A 1 - 1 shell and tube heat exchanger is available. The best arrangement is

A. counter flow with process stream on shell side.
B. counter flow with process stream on tube side.
C. parallel flow with process stream on shell side.
D. parallel flow with process stream on tube side.
Answer» B. counter flow with process stream on tube side.
Discussion
3.

A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be

A. greater than that for uninsulated steam pipe.
B. less than that of the uninsulated steam pipe.
C. equal to that of the uninsulated steam pipe.
D. less than the steam pipe with 5 cms insulation.
Answer» C. equal to that of the uninsulated steam pipe.
Discussion
4.

In the equation = Δ; Δ is

A. geometric mean temperature difference.
B. arithmetic mean temperature difference.
C. logarithmic mean temperature difference.
D. the difference of average bulk temperatures of hot and cold fluids.
Answer» D. the difference of average bulk temperatures of hot and cold fluids.
Discussion
5.

In Joule's experiment, an insulated container contains 20 kg of water initially at 25°C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms. Neglecting the heat capacity of agitator, the temperature of water (in °C) is

A. 40.5
B. 34.4
C. 26.8
D. 25
Answer» C. 26.8
Discussion
6.

The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K= 0.04 W/m.°K and thickness 0.16m is 10 W/m. The temperature of the inside wall is - 5°C. The outside wall temperature is

A. 25°C
B. 30°C
C. 35°C
D. 40°C
Answer» D. 40°C
Discussion
7.

Steam consumption in kg/hr in case of an evaporator is given by (where, & are capacity the economy of the evaporator respectively)

A. /
B. /
Answer» B. /
Discussion
8.

With the increase of temperature, the Col-burn factor

A. increases.
B. decreases.
C. remains unchanged.
D. may increase or decrease ; depending on temperature.
Answer» B. decreases.
Discussion
9.

Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, = shell diameter)

A. 0.2
B. 0.5
C. 0.66
D. 0.80
Answer» B. 0.5
Discussion
10.

The equation, , corrosponds to __________ analogy.

A. Von-Karmann
B. Reynolds
C. Colburn
D. Prandtl
Answer» E.
Discussion
11.

1000 Kg of liquid at 30°C in a well stirred vessel has to be heated to 120°C, using immersed coils carrying condensing steam at 150°C. The area of the steam coils is 1.2 m and the overall heat transfer co-efficient to the liquid is 1500 W/m.°C. Assuming negligible heat loss to the surrounding and specific heat capacity of the liquid to be 4 kJ/kg.°C, the time taken for the liquid to reach desired temperature will be

A. 15 min
B. 22 min
C. 44 min
D. 51 min
Answer» E.
Discussion
12.

The equation, ( x ) = /2, is the __________ analogy.

A. Colburn
B. Reynolds
C. Prandtl
D. none of these.
Answer» B. Reynolds
Discussion
13.

At steady state the temperature variation in a plane wall, made of two different solids I & II is shown below :The thermal conductivity of material I

A. is smaller than that of II.
B. is greater than that of II.
C. is equal to that of II.
D. can be greater than or smaller than that of II.
Answer» B. is greater than that of II.
Discussion
14.

For condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively and , then

A. =
B. >
C. <
D. could be greater or smaller than
Answer» D. could be greater or smaller than
Discussion
15.

Overall heat transfer co-efficient of a particular tube is . If the same tube with some dirt deposited on either side has coefficient , then

A. =
B. >
C. >
D. = dirt factor -
Answer» B. >
Discussion
16.

In a shell and tube heat exchanger, the height of 25 percent cut baffles is equal to (where, = inside diameter of shell)

A. 0.25
B. 0.75
C. 0.50
D. none of these
Answer» C. 0.50
Discussion
17.

A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m.K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is

A. 555
B. 55.5
C. 0.55
D. 0.15
Answer» E.
Discussion
18.

For a laminar flow of fluid in a circular tube, '' is the convective heat transfer co-efficient at velocity ''. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is

A. 1.26
B. 0.794
C. 0.574
D. 1.741
Answer» C. 0.574
Discussion
19.

Walls of a cubical oven are of thickness , and they are made of material of thermal conductivity . The temperature inside the oven is 100°C and the inside heat transfer co-efficient is 3/. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade ?

A. 35.5
B. 43.75
C. 81.25
D. 48.25
Answer» D. 48.25
Discussion
20.

In case of surface condensers, a straight line is obtained on plotting __________ on an ordinary graph paper.

A. 1/
B. 1/
Answer» B. 1/
Discussion
21.

( x ) is called the __________ number.

A. Graetz
B. Reyleigh
C. Nusselt
D. Stanton
Answer» C. Nusselt
Discussion
22.

If average heat transfer co-efficient is and the local coefficient at the end of the plate is then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length

A. =
B. = 2
C. = 0.5
D. = 0.75
Answer» C. = 0.5
Discussion
23.

The Fourier number (defined as a.t/L) is used in the analysis of problem involving heat transfer by

A. forced convection
B. natural convection
C. transient conduction
D. steady state conduction
Answer» D. steady state conduction
Discussion
24.

The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m.K. At steady state, the temperature of the right face in °C is

A. 77.2
B. 71.2
C. 63.8
D. 48.7
Answer» E.
Discussion
25.

Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by This is valid for the value of equal to

A. < 2100
B. 2100-4000
C. > 4000
D. > 10000
Answer» E.
Discussion
26.

Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m°C.

A. 10-50
B. 100-500
C. 1000-1500
D. 5000-15000
Answer» E.
Discussion
27.

If = inner film co-efficient and / = outer film co-efficient, then the overall heat transfer co-efficient is

A. always less than
B. always between
C. and
D. always higher than
E. dependent on metal resistance
Answer» C. and
Discussion
28.

A composite wall consists of two plates A and B placed in series normal to the flow of heat. The thermal conductivities are and and the specific heat capacities are and for plates A and B respectively. Plate B has twice the thickness of plate A. At steady state, the temperature difference across plate A is greater than that across plate B, when

A. >
B. <
C. < 0.5
D. >2
Answer» D. >2
Discussion
29.

The critical radius of insulation for a spherical shell is (where, = thermal conductivity of insulating material = heat transfer coefficient at the outer surface)

A. /
B. 2
C. /
D. /
E. /
Answer» C. /
Discussion
30.

The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is

A. 11.2 kW/m
B. 12.0 kW/m
C. 14.6 kW/m
D. 16.5 kW/m
Answer» E.
Discussion
31.

In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing is respectively (where, = inside diameter of the shell)

A. /5 and
B. /2 and 2
C. /4 and 2
D. and 2
Answer» B. /2 and 2
Discussion
32.

Heat transfer co-efficient equation for forced convection, = 0.023 . , is not valid, if the value of

A. n = 0.4 is used for heating.
B. n = 0.3 is used for cooling.
C. Reynolds number for the flow involved is > 10000.
D. Reynolds number for the flow involved is < 2100.
Answer» E.
Discussion
33.

The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m.°C respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m.°C. The rate of heat loss from the outer surface in W.mis

A. 165.4
B. 167.5
C. 172.5
D. 175
Answer» B. 167.5
Discussion
34.

Value of Nusselt number [ = (/)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is

A. 0.5
B. 2
C. 10
D. 100
Answer» C. 10
Discussion
35.

In a laboratory test run, the rate of drying was found to be 0.5 x 10 kg/m.s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is

A. 2000
B. 4000
C. 5000
D. 6000
Answer» D. 6000
Discussion
36.

What is the geometric mean of two heat transfer areas and ?

A.
B. 2
Answer» B. 2
Discussion
37.

Fouling factor for a heat exchanger is given by (where, = heat transfer co-efficient of dirty surface = heat transfer co-efficient of clean surface)

A. -
B. -
Answer» C.
Discussion
38.

The thermal radiation emitted by a body is proportional to , where is its absolute temperature. The value of '' is exactly 4 for

A. black painted bodies only
B. all bodies
C. polished bodies only
D. a black body
Answer» C. polished bodies only
Discussion
39.

Stefan-Boltzman law which describes the radiation heat transfer states that, it is proportional to (where, = temperature in °C = absolute temperature in ° K )

A. 1/
B. 1/
Answer» C.
Discussion
40.

For what value of Prandtl number, = /2?

A. 1.5
B. 1
C. > 1
D. < 1
Answer» C. > 1
Discussion
41.

Out of the following four assumptions used in the derivation of the equation for LMTD , which one is subject to the largest deviation in practice ?

A. Constant overall heat transfer co-efficient.
B. Constant rate of fluid flow.
C. Constant specific heat.
D. No partial phase change in the system.
Answer» C. Constant specific heat.
Discussion
42.

Resistance to heat flow by conduction is proportional to (where, & ρ are thickness & density of the material respectively and = area normal to the direction of heat flow. )

A. 1/ρ
B. 1/
C. all (a), (b) & (c)
Answer» E.
Discussion
43.

200 kg of solids (on dry basis) is subjected to a drying process for a period of 5000 seconds. The drying occurs in the constant rate period with the drying rate as, = 0.5 x 10 kg/m.s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m/1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid)

A. 0.5
B. 0.05
C. 0.1
D. 0.15
Answer» D. 0.15
Discussion
44.

The average heat transfer co-efficient over the entire length of the plate () and the local heat transfer co-efficient (), in case of heat transfer over a flat plate in lminar zone is related as

A. = 0.8
B. = 2
C. =
D. = 5
Answer» C. =
Discussion
45.

Conductance is given by(where, = thickness, = heat flow area, = thermal conductivity.)

A. /
B. /
C. /
D. /
Answer» C. /
Discussion
46.

The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, = absolute temperature of the black body)

A. α
B. α 1/
C. α
D. independent of
Answer» C. α
Discussion
47.

The local surface conductance for laminar film condensation on vertical surface is (where, = film thickness)

A. ∝
B. ∝ 1/
C. ∝
D. independent of '
E. '
Answer» C. ∝
Discussion
48.

Heat transfer co-efficient (h) for liquids increases with

A. increasing temperature.
B. decreasing temperature.
C. decreasing Reynolds number.
D. none of these.
Answer» B. decreasing temperature.
Discussion
49.

A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m.K. The Biot number is

A. 5.6
B. 0.025
C. 3.5
D. 0.0035
Answer» C. 3.5
Discussion
50.

At > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the

A. buffer zone
B. turbulent core
C. both (a) and (b)
D. viscous sub-layer
Answer» E.
Discussion