If Prandtl number is greater than the Schmidt number, then the____________________?

Concentration boundary layer lies inside the thermal boundary layer

Thermal boundary layer lies inside the concentration boundary layer

Concentration boundary layer lies inside the thermal boundary layer

Thermal & concentration boundary layers are of equal thickness

Hydrodynamic (i.e., momentum) boundary layer is thicker than the other two

If air (a non-condensing gas) is present in a condensing vapor stream, it will ______________ the condensation rate of vapor?

Increase the condensing film co-efficient as well as

Heat transfer efficiency leading of energy conservation in a heat exchanger can be achieved by____________________?

Enhancing the fluid pumping rate

Keeping the heat transfer surface clean

Enhancing the fluid pumping rate

Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8. Pr n, is not valid, if the value of __________________?

Reynolds number for the flow involved is > 10000

Reynolds number for the flow involved is < 2100

Heat transfer by natural convection is enhanced in system with__________________?

High co-efficient of thermal expansion

Low density change with temperature

Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer cannot take place____________________?

From one part of a body to the another part of the same body

Between two bodies in physical contact with each other

Between two bodies not in physical contact with each other

From one part of a body to the another part of the same body

Heat exchangers operating, when the asymptotic range is reached, ?

Results in abruptly increased velocity

Provide very large heat transfer co-efficient

Results in making part of the heating surface inactive

Results in abruptly increased velocity

Harmonic mean temperature difference is given by_________________?

2 (ΔT1 . ΔT2)/(ΔT1 – ΔT2)

Fouling factor_____________________?

Does not provide a safety factor for design

Accounts for additional resistances to heat flow

‘Fouling factor’ used in the design of a multipass shell and tube heat exchanger is a_____________________?

Conversion factor for individual film heat transfer co-efficient to overall heat transfer coefficient

Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator ?

Calandria vertical tube evaporator

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

425 + Mcqs in Chemical Heat Transfer in Chemical Engineering Page 6 McqOptions

251.	If Prandtl number is greater than the Schmidt number, then the____________________?
A.	Thermal boundary layer lies inside the concentration boundary layer
B.	Concentration boundary layer lies inside the thermal boundary layer
C.	Thermal & concentration boundary layers are of equal thickness
D.	Hydrodynamic (i.e., momentum) boundary layer is thicker than the other two
Answer» B. Concentration boundary layer lies inside the thermal boundary layer

Discussion

252.	If heat transfer rate varies with the time, it is termed as__________________?
A.	Forced convection
B.	Steady state conduction
C.	Monochromatic radiation
D.	None of these
Answer» E.

Discussion

253.	If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is________________?
A.	Always less than h1
B.	Always between h1 and h2
C.	Always higher than h2
D.	Dependent on metal resistance
Answer» C. Always higher than h2

Discussion

254.	If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length________________?
A.	ha = hl
B.	ha = 2hl
C.	ha = 0.5 hl
D.	ha = 0.75 hl
Answer» C. ha = 0.5 hl

Discussion

255.	If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is_________________?
A.	1
B.	2
C.	1/2
D.	4
Answer» C. 1/2

Discussion

256.	If air (a non-condensing gas) is present in a condensing vapor stream, it will ______________ the condensation rate of vapor?
A.	Increase
B.	Decrease
C.	Not affect
D.	Increase the condensing film co-efficient as well as
Answer» C. Not affect

Discussion

257.	If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will ________________?
A.	Increase by 1.8 times
B.	Decrease by 22
C.	Increase by 216
D.	Remain unchanged
Answer» D. Remain unchanged

Discussion

258.	Hot water (0.01 m3 /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 m3/min) of density 800 kg/m3 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

259.	Heat waves_____________________?
A.	Cannot pass through vacuum
B.	Travel in straight line
C.	Can be reflected by a mirror
D.	Both B. and C.
Answer» E.

Discussion

260.	Heat transfer rate per unit area is called_________________?
A.	Thermal conductivity
B.	Heat flux
C.	Heat transfer co-efficient
D.	Thermal diffusivity
Answer» C. Heat transfer co-efficient

Discussion

261.	Heat transfer rate described by Fourier’s law will decrease, if the _____________ increases?
A.	Thermal conductivity
B.	Thickness
C.	Temperature difference
D.	Heat transfer area
Answer» C. Temperature difference

Discussion

262.	Heat transfer occurs by natural convection because change in temperature causes difference in__________________?
A.	Viscosity
B.	Density
C.	Thermal conductivity
D.	Heat capacity
Answer» C. Thermal conductivity

Discussion

263.	Heat transfer in the laminar sub-layer in case of a liquid flowing through a pipe, is mostly by__________________?
A.	Eddies current
B.	Conduction
C.	Convection
D.	None of these
Answer» C. Convection

Discussion

264.	Heat transfer efficiency leading of energy conservation in a heat exchanger can be achieved by____________________?
A.	Keeping the heat transfer surface clean
B.	Enhancing the fluid pumping rate
C.	Increasing the tube length
D.	None of these
Answer» B. Enhancing the fluid pumping rate

Discussion

265.	Heat transfer co-efficient (h1) for liquids increases with__________________?
A.	Increasing temperature
B.	Decreasing temperature
C.	Decreasing Reynolds number
D.	None of these
Answer» B. Decreasing temperature

Discussion

266.	Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by h = 0.023 (K/D) (DVρ/μ)0.8 (CP.μ/k)0.4. This is valid for the value of NRe equal to_______________?
A.	4000
B.	> 10000
Answer» C.

Discussion

267.	Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8. Pr n, 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

268.	Heat transfer by radiation between two bodies at T1 & T2 and in an ambient temperature of Ta°C depends on_____________?
A.	T1 – T2
B.	T1 – Ta
C.	T2 – Ta
D.	None of these
Answer» E.

Discussion

269.	Heat transfer by natural convection is enhanced in system with__________________?
A.	High viscosity
B.	High co-efficient of thermal expansion
C.	Low temperature gradients
D.	Low density change with temperature
Answer» C. Low temperature gradients

Discussion

270.	Heat transfer by ____________ may not necessarily require the presence of a medium?
A.	Conduction
B.	Natural convection
C.	Forced convection
D.	Radiation
Answer» E.

Discussion

271.	Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer cannot take place____________________?
A.	Between two bodies in physical contact with each other
B.	Between two bodies not in physical contact with each other
C.	From one part of a body to the another part of the same body
D.	Both B & C
Answer» C. From one part of a body to the another part of the same body

Discussion

272.	Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is_______________?
A.	0.2
B.	0.4
C.	0.6
D.	0.8
Answer» D. 0.8

Discussion

273.	Heat sensitive materials can be concentrated in an evaporator employing_______________?
A.	Vacuum
B.	High pressure
C.	High residence time
D.	None of these
Answer» B. High pressure

Discussion

274.	Heat produced when a steady state current, I passes through an electrical conductor having resistance, ‘R’ is___________________?
A.	IR
B.	I2R
C.	IR2
D.	I2R2
Answer» C. IR2

Discussion

275.	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

Discussion

276.	Heat flux is the time rate of heat transfer per unit_______________?
A.	Length
B.	Area
C.	Volume
D.	None of these
Answer» C. Volume

Discussion

277.	Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because___________________?
A.	Convection becomes important
B.	Conduction becomes important
C.	Radiation becomes important
D.	Sub-cooled boiling occurs
Answer» D. Sub-cooled boiling occurs

Discussion

278.	Heat flux, as defined in heat flow is analogous to _______________ in electricity flow?
A.	Current
B.	Voltage
C.	Resistance
D.	None of these
Answer» B. Voltage

Discussion

279.	Heat exchangers operating, when the asymptotic range is reached, ?
A.	Provide very large heat transfer co-efficient
B.	Results in making part of the heating surface inactive
C.	Results in abruptly increased velocity
D.	None of these
Answer» C. Results in abruptly increased velocity

Discussion

280.	Heat exchanger tubes are never made of_________________?
A.	Plain carbon steel
B.	Stainless steel
C.	Lead
D.	Copper
Answer» D. Copper

Discussion

281.	_____________ heat exchanger is used for chilling oil to be dewaxed?
A.	U-tube
B.	Double pipe
C.	Fixed tube
D.	Floating head
Answer» C. Fixed tube

Discussion

282.	_____________ heat exchanger is the most suitable, when the temperature of shell side fluid is much higher than that of tube side?
A.	Single pass, fixed tube sheet
B.	U-tube
C.	Three pass, fixed tube sheet
D.	None of these
Answer» C. Three pass, fixed tube sheet

Discussion

283.	Harmonic mean temperature difference is given by_________________?
A.	√(ΔT1 . ΔT2)
B.	2 (ΔT1 . ΔT2)/(ΔT1 + ΔT2)
C.	2 (ΔT1 . ΔT2)/(ΔT1 – ΔT2)
D.	(ΔT1 – ΔT2)/(ΔT1 . ΔT2)
Answer» C. 2 (ΔT1 . ΔT2)/(ΔT1 – ΔT2)

Discussion

284.	Grashoff number is given by________________?
A.	gD3.β.Δtρ2/μ2
B.	gD2βΔtρ/μ2
C.	gD2βΔtP2μ
D.	gD3βΔtP2/μ
Answer» B. gD2βΔtρ/μ2

Discussion

285.	Grashoff number, which is defined as g . β (Ts – T∞) ρ2. L3/μ2, is proportional to the ratio of buoyancy force to ____________ force?
A.	Viscous
B.	Elastic
C.	Inertial
D.	None of these
Answer» B. Elastic

Discussion

286.	Graetz number is given by__________________?
A.	mCp/kL
B.	kL/mCp
C.	mCp/kμ
D.	kμ/mCp
Answer» B. kL/mCp

Discussion

287.	Fruit juice (a heat sensitive material) can be concentrated in a ____________ evaporator?
A.	Long tube
B.	Falling film
C.	High pressure
D.	None of these
Answer» C. High pressure

Discussion

288.	Fresh orange juice contains 12% (by weight) solids and the rest water 90% of the fresh juice is sent to an evaporator to remove water and subsequently mixed with the remaining 10% of fresh juice. The resultant product contains 40% solids. The kg of water removed from 1 kg fresh juice is__________________?
A.	0.4
B.	0.5
C.	0.6
D.	0.7
Answer» E.

Discussion

289.	Fqra cold viscous feed, backward feed gives _____________ than forward feed?
A.	A higher capacity
B.	A lower capacity
C.	Lower economy
D.	None of these
Answer» B. A lower capacity

Discussion

290.	Fourier’s law of heat conduction applies to _____________ surfaces?
A.	Isothermal
B.	Non-isothermal
C.	Both A. and B.
D.	Neither A. and B.
Answer» D. Neither A. and B.

Discussion

291.	Fourier’s law applies to the heat transfer by__________________?
A.	Convection
B.	Radiation
C.	Conduction
D.	All A., B. & C.
Answer» D. All A., B. & C.

Discussion

292.	Fouling factor_____________________?
A.	Is a dimensionless quantity
B.	Does not provide a safety factor for design
C.	Accounts for additional resistances to heat flow
D.	None of these
Answer» D. None of these

Discussion

293.	‘Fouling factor’ used in the design of a multipass shell and tube heat exchanger is a_____________________?
A.	Non-dimensional factor
B.	Factor of safety
C.	Conversion factor for individual film heat transfer co-efficient to overall heat transfer coefficient
D.	None of these
Answer» C. Conversion factor for individual film heat transfer co-efficient to overall heat transfer coefficient

Discussion

294.	Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface) ?
A.	U1 – U2
B.	1/U1 – 1/U2
C.	1/U2 – 1/U1
D.	U2 – U1
Answer» C. 1/U2 – 1/U1

Discussion

295.	Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator ?
A.	Long vertical evaporator
B.	Horizontal tube evaporator
C.	Agitated film evaporator
D.	Calandria vertical tube evaporator
Answer» D. Calandria vertical tube evaporator

Discussion

296.	Forced circulation evaporators are normally used for concentrating liquids having ___________________?
A.	Scaling characteristics
B.	High viscosity
C.	Both A. & B.
D.	Neither A. nor B.
Answer» D. Neither A. nor B.

Discussion

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

Discussion

298.	For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus- Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of________________?
A.	1
B.	1.74
C.	6.1
D.	37
Answer» D. 37

Discussion

299.	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

Discussion

300.	For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is_________________?
A.	3
B.	0.33
C.	1
D.	1.33
Answer» D. 1.33

Discussion

Explore topic-wise MCQs in Chemical Engineering.

If Prandtl number is greater than the Schmidt number, then the____________________?

If heat transfer rate varies with the time, it is termed as__________________?

If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is________________?

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

If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is_________________?

If air (a non-condensing gas) is present in a condensing vapor stream, it will ______________ the condensation rate of vapor?

If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will ________________?

Hot water (0.01 m3 /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 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately ?

Heat waves_____________________?

Heat transfer rate per unit area is called_________________?

Heat transfer rate described by Fourier’s law will decrease, if the _____________ increases?

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

Heat transfer in the laminar sub-layer in case of a liquid flowing through a pipe, is mostly by__________________?

Heat transfer efficiency leading of energy conservation in a heat exchanger can be achieved by____________________?

Heat transfer co-efficient (h1) for liquids increases with__________________?

Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by h = 0.023 (K/D) (DVρ/μ)0.8 (CP.μ/k)0.4. This is valid for the value of NRe equal to_______________?

Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8. Pr n, is not valid, if the value of __________________?

Heat transfer by radiation between two bodies at T1 & T2 and in an ambient temperature of Ta°C depends on_____________?

Heat transfer by natural convection is enhanced in system with__________________?

Heat transfer by ____________ may not necessarily require the presence of a medium?

Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer cannot take place____________________?

Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is_______________?

Heat sensitive materials can be concentrated in an evaporator employing_______________?

Heat produced when a steady state current, I passes through an electrical conductor having resistance, ‘R’ is___________________?

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

Heat flux is the time rate of heat transfer per unit_______________?

Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because___________________?

Heat flux, as defined in heat flow is analogous to _______________ in electricity flow?

Heat exchangers operating, when the asymptotic range is reached, ?

Heat exchanger tubes are never made of_________________?

_____________ heat exchanger is used for chilling oil to be dewaxed?

_____________ heat exchanger is the most suitable, when the temperature of shell side fluid is much higher than that of tube side?

Harmonic mean temperature difference is given by_________________?

Grashoff number is given by________________?

Grashoff number, which is defined as g . β (Ts – T∞) ρ2. L3/μ2, is proportional to the ratio of buoyancy force to ____________ force?

Graetz number is given by__________________?

Fruit juice (a heat sensitive material) can be concentrated in a ____________ evaporator?

Fqra cold viscous feed, backward feed gives _____________ than forward feed?

Fourier’s law of heat conduction applies to _____________ surfaces?

Fourier’s law applies to the heat transfer by__________________?

Fouling factor_____________________?

‘Fouling factor’ used in the design of a multipass shell and tube heat exchanger is a_____________________?

Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface) ?

Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator ?

Forced circulation evaporators are normally used for concentrating liquids having ___________________?

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

For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus- Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of________________?

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 the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is_________________?