S3

Question 1

What is the steam economy in case of a single effect evaporator system?

Answer 1

<1

Question 2

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

Answer 2

ha=2hi

Question 3

jH factor for heat transfer is not a function of the ______ number.

Answer 3

Both b and c

B. Nusselt
C. Grashof

Question 4

The Fourier number is used in the analysis of problem involving heat transfer by

Answer 4

transient conduction

Question 5

The energy radiated from a surface Q at absolute temperature T is related as

Answer 5

Q α T^4

Question 6

Baffles are provided in heat exchangers to increase the

Answer 6

heat transfer coefficient

Question 7

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, Nc = 0.5 x 10-3 kg/m2.s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m2/1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid)

Answer 7

0.1

Question 8

In case of a vertical tube evaporator, with increase in the liquor level, the

Answer 8

capacity of the evaporator is decreased

Question 9

The ratio of total radiating power to the absorptivity of the body depends upon the _______ as per Kirchoffs law.

Answer 9

temperature of the body

Question 10

For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally

Answer 10

decreases

Question 11

A 2-4 heat exchanger involves

Answer 11

both counter and parallel flow of the fluids

Question 12

In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always

Answer 12

<1

Question 13

With an increased temperature, the thermal conductivity of steel

Answer 13

decreases

Question 14

Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids?

Answer 14

Sieder-Tate equation

Question 15

The main function of baffles provided in a shell and tube heat exchanger is to

Answer 15

enhance turbulence

Question 16

In a single effect evaporator, the economy is

Answer 16

<1

Question 17

LMTD correction factor which is to be applied for a cross flow heat exchanger increases with increase in the number of shell passes. Its value for a single pass cross flow heat exchanger is

Answer 17

<1

Question 18

Which of the following is not concerned with the heat transfer?

Answer 18

Schmidt number

Question 19

Latent heat absorbed by 1 lb of water at 212°F, when it is changed to steam at 212°F, may be around __________ BTU.

Answer 19

180

Question 20

In counter flow compared to parallel flow,

Answer 20

both a and b

A. LMTD is greater
B. Less surface area is required for a given heat transfer rate

Question 21

The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is
(Stefan-Boltzman constant = 5.67xl0-8 W/m2.K4)

Answer 21

1000

Question 22

Crystallization of solids from a homogenous solution is an _______ process

Answer 22

exothermic

Question 23

A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is

Answer 23

24000

Question 24

Value of Prandtl number for water ranges from

Answer 24

5 to 10

Question 25

Heat transfer in the laminar sublayer in case of a liquid flowing through a pipe, is mostly by

Answer 25

**conduction**

Question 26

Among liquids, water has a comparatively high value of thermal conductivity, due to its

Answer 26

**partial ionization**

Question 27

Reynold’s analogy states that

Answer 27

**St= f/2**

Question 28

For evaporation of viscous solution multiple effect evaporator, the preferred feeding scheme is

Answer 28

**backward**

Question 29

The sum of reflectivity and absorptivity for an opaque body is equal to

Answer 29

**1**

Question 30

The film thickness for laminar dilm condensation on vertical surface ______ from top to bottom

Answer 30

**cumulatively increases**

Question 31

In case of multipass shell and tube heat exchanger, providing a baffle on the shell side ______ the heat transfer rate

Answer 31

**increases**

Question 32

The local surface conductance for laminar film condensation on vertical surface is

Answer 32

** α1/t**

Question 33

Heat transfer coefficient for liquids increases with

Answer 33

**increasing temperature**

Question 34

A diathermaneous substance _______ the thermal radiation completely

Answer 34

**transmits**

Question 35

A hot body will radiate heat most rapidly, if its surface is

Answer 35

**black and rough**

Question 36

Evaporation of 1kg of water from a solution in a single effect evaporator requires about ______ kg of steam

Answer 36

**1-1.3**

Question 37

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/m2.K. The Biot number is

Answer 37

**0.025**

Question 38

Analogy between mass and heat transfer is not applicable in case of

Answer 38

**both b and c** B. Thermal or pressure mass diffusion C. Viscous heating or chemical reaction

Question 39

A ______ surface has the maximum thermal emissivity out of the following

Answer 39

**black and rough**

Question 40

Radiant energy received by a body is proportional to

Answer 40

**d^2**

Question 41

Mechanical recompression evaporation is used in the production of

Answer 41

**distilled water**

Question 42

A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the ______number.

Answer 42

**Brinkman**

Question 43

Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be

Answer 43

**0.45**

Question 44

The purpose of providing a ‘catchall’ in the vapor line of an evaporator is to

Answer 44

**arrest the entrained liquid**

Question 45

What is the thermal conductivity of a perfect heat insulator?

Answer 45

**zero**

Question 46

Fouling factor used in the design of a multipass shell and tube heat exchanger is a

Answer 46

**factor of safety**

Question 47

A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co-efficient for turbulent flow conditions is proportional to

Answer 47

**d^-0.2**

Question 48

Prandtl and Reynolds analogy are same, when Prandtl number is

Answer 48

**1**

Question 49

Heat transfer occurs by natural convection because change in temperature causes difference in

Answer 49

**density**

Question 50

The ratio of kinematic viscosity to thermal diffusivity is called the ____ number

Answer 50

**Prandtl**