%_The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation._%

May increase or decrease ; depends on the material

%_Shell side pressure drop in a shell and tube heat exchanger does not depend upon the_%

Baffle spacing & shell diameter

Viscosity, density & mass velocity of shell side fluid

%_In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is __________ the outlet temperature of the cold fluid._%

Either more or less than (depending upon the fluid)

_ Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger?$?

Corrosiveness & fouling characteristics

_ For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it$?

Decreases the outlet temperature of cooling medium

Increases the overall heat transfer coefficient

_ Prandtl number is the reciprocal of$?

Thermal diffusivity/Momentum diffusivity

Thermal diffusivity x Mass diffusivity

Mass diffusivity x Momentum diffusivity

_ The outlet temperature of cooling water in a heat exchanger is generally not allowed to exceed above 50¬¨‚àûC in industrial practice mainly to avoid$?

Decrease in heat exchanger efficiency

_ Boiling point elevation of an ideal solution$?

Decreases rapidly with temperature rise

Increases rapidly with temperature rise

Decreases rapidly with temperature rise

_ Which of the following situations can be approximated to a steady state heat transfer system?$?

Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180¬¨‚àûC

A red hot steel slab (having outside surface temperature as 1300¬¨‚àûC) exposed to the atmosheric air at 35¬¨‚àûC

10 kg of dry saturated steam at 8 kgf/cm¬¨‚â§ flowing through a short length of stainless steel pipe exposed to atmospheric air at 35¬¨‚àûC

Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180¬¨‚àûC

A sub-cooled refrigerant liquid at 8¬¨‚àûC flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35¬¨‚àûC

_ In regenerative air preheater (as practised in heating of coke ovens), the heat is transferred$?

By direct contact of hot flue gas with air

By heating an intermediate material (like chequor bricks) and then heating the air from this hot material

_ If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid$?

Increases or decreases depending on number of shell passes

_ Boiling point of a solution according to Duhring's rule is a linear function of the __________ of water.$?

Boiling point (at the same pressure)

_ Dropwise condensation of steam on cooling surface is promoted$?

When both the steam and the tube are clean

_ Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube$?

Exit-fluid temperature > wall temperature

Exit fluid temperature < wall temperature

Exit fluid temperature = wall temperature

_ The value of Stefan-Boltazman constant in SI unit is$?

0.1714 x 10-8W/m¬¨‚â§.¬¨‚àûK4

5.6697 x 10-8W/m¬¨‚â§.¬¨‚àûK4

0.1714 x 10-8W/m¬¨‚â§.¬¨‚àûK4

5.6697 x 10-8kcal/m¬¨‚â§ . ¬¨‚àûK4

0.1714 x 10-8kcal/m¬¨‚â§. ¬¨‚àûK4

482 + Mcqs in Heat Transfer in Chemical Engineering Page 5 McqOptions

201.	%_The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation._%
A.	Increases
B.	Decreases
C.	Remains constant
D.	May increase or decrease ; depends on the material
Answer» E.

202.	%_Dietus-Boelter equation cannot be used for molten metals mainly due to its very low_%
A.	Prandtl number
B.	Grashoff number
C.	Thermal conductivity
D.	Viscosity
Answer» B. Grashoff number

203.	%_Value of Nusselt number [Nu = (hD/k)] 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

204.	%_It is not preferable to use superheated steam in evaporators, because of its very_%
A.	High temperature
B.	High pressure
C.	Low film co-efficient
D.	None of these
Answer» D. None of these

205.	%_Shell side pressure drop in a shell and tube heat exchanger does not depend upon the_%
A.	Baffle spacing & shell diameter
B.	Tube diameter & pitch
C.	Viscosity, density & mass velocity of shell side fluid
D.	None of these
Answer» E.

206.	%_In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is __________ the outlet temperature of the cold fluid._%
A.	Equal to
B.	More than
C.	Less than
D.	Either more or less than (depending upon the fluid)
Answer» B. More than

207.	%_For a multipass shell and tube heat exchanger, the LMTD correction factor is always_%
A.	1
B.	> 1
C.	< 1
D.	Between 1 & 2
Answer» D. Between 1 & 2

208.	%_Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface?_%
A.	Liquid density
B.	Liquid viscosity
C.	Hot surface temperature
D.	Interfacial tension
Answer» E.

209.	_ For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area$?
A.	Increases
B.	Decreases
C.	Remains constant
D.	Passes through a maxima
Answer» E.

210.	_ Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger?$?
A.	Corrosiveness & fouling characteristics
B.	Pressure
C.	Viscosity
D.	Density
Answer» E.

211.	_ Small scale evaporation is done in a$?
A.	Heat exchanger
B.	Condenser
C.	Multiple effect evaporator
D.	Steam jacketed kettle
Answer» E.

217.	_ In a boiling curve, the peak heat flux is called the __________ point.$?
A.	Nusselt
B.	Leidenfrost
C.	Boiling
D.	Burnout
Answer» E.

218.	_ For what value of Prandtl number, St = f/2?$?
A.	1.5
B.	1
C.	> 1
D.	< 1
Answer» C. > 1

220.	_ Film condensation is promoted on a/an __________ surface.$?
A.	Oily
B.	Coated
C.	Clean & smooth
D.	Dirty
Answer» D. Dirty

224.	_ In a multiple effect evaporator, the effect of boiling point elevation is to$?
A.	Reduce the capacity
B.	Reduce the economy
C.	Increase the economy
D.	None of these
Answer» B. Reduce the economy

212.	_ For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it$?
A.	Decreases the pressure drop
B.	Decreases the outlet temperature of cooling medium
C.	Increases the overall heat transfer coefficient
D.	None of these
Answer» D. None of these

213.	_ For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally$?
A.	Decreases
B.	Increases
C.	Remains unchanged
D.	Increases exponentially
Answer» B. Increases

214.	_ Prandtl number is the reciprocal of$?
A.	Thermal diffusivity/Momentum diffusivity
B.	Thermal diffusivity x Momentum
C.	Thermal diffusivity x Mass diffusivity
D.	Mass diffusivity x Momentum diffusivity
Answer» B. Thermal diffusivity x Momentum

215.	_ The outlet temperature of cooling water in a heat exchanger is generally not allowed to exceed above 50¬¨‚àûC in industrial practice mainly to avoid$?
A.	Its evaporation loss
B.	Excessive corrosion
C.	Uneconomic LMTD
D.	Decrease in heat exchanger efficiency
Answer» C. Uneconomic LMTD

216.	_ The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are$?
A.	Re.Gz
B.	Nu, Pr
C.	Nu, Pr, Re
D.	Nu, Gz
Answer» E.

219.	_ Baffles are provided in heat exchangers to increase the$?
A.	Fouling factor
B.	Heat transfer area
C.	Heat transfer co-efficient
D.	Heat transfer rate
Answer» D. Heat transfer rate

221.	_ Boiling point elevation of an ideal solution$?
A.	Increases rapidly with temperature rise
B.	Decreases rapidly with temperature rise
C.	In independent of pressure
D.	Both B and C
Answer» B. Decreases rapidly with temperature rise

222.	_ Tube pitch is the __________ of tube diameters and the clearances.$?
A.	Sum
B.	Difference
C.	Ratio
D.	None of these
Answer» B. Difference

223.	_ 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$?
A.	D0.8
B.	D-0.2
C.	D-1
D.	D-1.8
Answer» C. D-1

225.	_ A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of$?
A.	2
B.	20.8
C.	20.2
D.	20.5
Answer» C. 20.2

Explore topic-wise MCQs in Chemical Engineering.

%_The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation._%

%_Dietus-Boelter equation cannot be used for molten metals mainly due to its very low_%

%_Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is_%

%_It is not preferable to use superheated steam in evaporators, because of its very_%

%_Shell side pressure drop in a shell and tube heat exchanger does not depend upon the_%

%_In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is __________ the outlet temperature of the cold fluid._%

%_For a multipass shell and tube heat exchanger, the LMTD correction factor is always_%

%_Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface?_%

_ For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area$?

_ Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger?$?

_ Small scale evaporation is done in a$?

_ For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it$?

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

_ Prandtl number is the reciprocal of$?

_ The outlet temperature of cooling water in a heat exchanger is generally not allowed to exceed above 50¬¨‚àûC in industrial practice mainly to avoid$?

_ The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are$?

_ In a boiling curve, the peak heat flux is called the __________ point.$?

_ For what value of Prandtl number, St = f/2?$?

_ Baffles are provided in heat exchangers to increase the$?

_ Film condensation is promoted on a/an __________ surface.$?

_ Boiling point elevation of an ideal solution$?

_ Tube pitch is the __________ of tube diameters and the clearances.$?

_ 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$?

_ In a multiple effect evaporator, the effect of boiling point elevation is to$?

_ A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of$?

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

_ LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counterflow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the __________ flow.$?

_ When vaporisation takes place directly at the heating surface, it is called$?

_ For a laminar flow of fluid in a circular tube, 'h‚Äö√á√Ö' is the convective heat transfer co-efficient at velocity 'V‚Äö√á√Ö'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is$?

_ Heat flux through several resistances in series in analogous to the current flowing through several$?

_ Which of the following situations can be approximated to a steady state heat transfer system?$?

_ Which one gives the monochromatic emissive power for black body radiation?$?

_ In regenerative air preheater (as practised in heating of coke ovens), the heat is transferred$?

_ Removal of __________ heat is involved in the condensation of a vapor under saturated conditions.$?

_ For concentrating an aqueous solution of a material like anhydrous Na‚Äö√á√áSO‚Äö√á√ë, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator.$?

_ Fourier's law of heat conduction applies to __________ surfaces.$?

_ Pick out the correct equation.$?

_ The absorptivity of a body is equal to its emissivity$?

_ For a perfectly transparent surface (like gases), the$?

_ If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law.$?

_ Heat transfer rate per unit area is called$?

_ The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m¬¨‚â§.K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m¬¨‚â§.K. The overall heat transfer co-efficient at this time is$?

_ If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid$?

_ A perfect black body is a perfect __________ of radiation.$?

_ Boiling point of a solution according to Duhring's rule is a linear function of the __________ of water.$?

_ Dropwise condensation of steam on cooling surface is promoted$?

_ Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube$?

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

_ Kg of liquid evaporated per hour in an evaporator is defined as its$?

_ The value of Stefan-Boltazman constant in SI unit is$?

226.	_ In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing is respectively (where, D = inside diameter of the shell)$?
A.	D/5 and D
B.	D/2 and 2 D
C.	D/4 and 2 D
D.	D and 2 D
Answer» B. D/2 and 2 D

227.	_ LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counterflow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the __________ flow.$?
A.	Parallel
B.	Mixed
C.	Counterflow
D.	Same in either A, B or C
Answer» E.

228.	_ When vaporisation takes place directly at the heating surface, it is called$?
A.	Film boiling
B.	Nucleate boiling
C.	Vapour binding
D.	None of these
Answer» C. Vapour binding

229.	_ For a laminar flow of fluid in a circular tube, 'h‚Äö√á√Ö' is the convective heat transfer co-efficient at velocity 'V‚Äö√á√Ö'. 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 h‚Äö√á√Ö
B.	0.794 h‚Äö√á√Ö
C.	0.574 h‚Äö√á√Ö
D.	1.741 h‚Äö√á√Ö
Answer» C. 0.574 h‚Äö√á√Ö

230.	_ Heat flux through several resistances in series in analogous to the current flowing through several$?
A.	Resistances in parallel
B.	Capacitors in series
C.	Resistances in series
D.	None of these
Answer» D. None of these

231.	_ Which of the following situations can be approximated to a steady state heat transfer system?$?
A.	A red hot steel slab (having outside surface temperature as 1300¬¨‚àûC) exposed to the atmosheric air at 35¬¨‚àûC
B.	10 kg of dry saturated steam at 8 kgf/cm¬¨‚â§ flowing through a short length of stainless steel pipe exposed to atmospheric air at 35¬¨‚àûC
C.	Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180¬¨‚àûC
D.	A sub-cooled refrigerant liquid at 8¬¨‚àûC flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35¬¨‚àûC
Answer» C. Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180¬¨‚àûC

232.	_ Which one gives the monochromatic emissive power for black body radiation?$?
A.	Planck's law
B.	Kirchhoffs law
C.	Wien's law
D.	Stefan-Boltzman law
Answer» B. Kirchhoffs law

233.	_ In regenerative air preheater (as practised in heating of coke ovens), the heat is transferred$?
A.	Through a metallic wall
B.	By direct contact of hot flue gas with air
C.	By heating an intermediate material (like chequor bricks) and then heating the air from this hot material
D.	None of these
Answer» D. None of these

234.	_ Removal of __________ heat is involved in the condensation of a vapor under saturated conditions.$?
A.	Super
B.	Sensible
C.	Latent
D.	Both B & C
Answer» C. Latent

235.	_ For concentrating an aqueous solution of a material like anhydrous Na‚Äö√á√áSO‚Äö√á√ë, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator.$?
A.	High pressure
B.	Vacuum
C.	Backward feed
D.	None of these
Answer» C. Backward feed