Value of Nusselt number [Nu = (hD/k)] for the heat transfer byconduction from a droplet or a spherical particle to a surrounding stagnant film is (A) 0.5 (B) 2 (C) 10 (D) 100

Value of Nusselt number [Nu = (hD/k)] for the heat transfer byconduction from a droplet or a spherical particle to a surrounding stagnant
film is
(A) 0.5
(B) 2
(C) 10
(D) 100
by

1 Answer

Answer :

(B) 2
by

Related questions

The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re 0.8 , where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as (A) D-1.8 (B) D-0.2 (C) D0.2 (D) D1.8

Description : The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re 0.8 , where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient ... pipe diameter (D) as (A) D-1.8 (B) D-0.2 (C) D0.2 (D) D1.8

Last Answer : (B) D-0.2

What is Nusselt number? (A) CP . µ/k (B) hD/k (C) h. CP /µ (D) CP . µ/h

Description : What is Nusselt number? (A) CP . µ/k (B) hD/k (C) h. CP /µ (D) CP . µ/h

Last Answer : (B) hD/k

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

Description : 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

Last Answer : (D) Reynolds number for the flow involved is < 2100

Gage pressure within a spherical droplet of a fluid is 'p'. What will be gage pressure within a bubble of the same size & of the same fluid? (A) p (B) 2 p (C) 0.5 p (D) 0.25 p

Description : Gage pressure within a spherical droplet of a fluid is 'p'. What will be gage pressure within a bubble of the same size & of the same fluid? (A) p (B) 2 p (C) 0.5 p (D) 0.25 p

Last Answer : (B) 2 p

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

Description : 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

Last Answer : (D) Nu, Gz

For the non catalytic reaction of particles with surrounding fluid, the same needed to achieve the same fractional conversion for particles of different unchanging sizes is proportional to the particle diameter, when the __________ is the controlling resistance. (A) Film diffusion (B) Diffusion through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Description : For the non catalytic reaction of particles with surrounding fluid, the same needed to achieve the same fractional conversion for particles of different unchanging sizes is proportional to the particle diameter, when the ... through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Last Answer : (C) Chemical reaction

For the non-catalytic reaction of particles with surrounding fluid, the time needed to achieve the same fractional conversion for particles of different but unchanging sizes is proportional to the square of particle diameter, when the __________ is the controlling resistance. (A) Film diffusion (B) Diffusion through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Description : For the non-catalytic reaction of particles with surrounding fluid, the time needed to achieve the same fractional conversion for particles of different but unchanging sizes is proportional to the square of particle diameter, ... through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Last Answer : (B) Diffusion through ash layer

Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the __________ number. (A) Sherwood (B) Schmidt (C) Peclet (D) Stanton

Description : Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the __________ number. (A) Sherwood (B) Schmidt (C) Peclet (D) Stanton

Last Answer : (A) Sherwood

Pick out the wrong statement pertaining to the analogy between equations of heat and mass transfer operations. (A) Sherwood number in mass transfer is analogous to Nusselt number in heat transfer (B) Prandtl number in heat transfer is analogous to Schmidt number in mass transfer (C) Reynolds number in mass transfer is analogous to Grashoff number in heat transfer (D) Reynolds number remains the same in both heat and mass transfer

Description : Pick out the wrong statement pertaining to the analogy between equations of heat and mass transfer operations. (A) Sherwood number in mass transfer is analogous to Nusselt number in heat transfer ... heat transfer (D) Reynolds number remains the same in both heat and mass transfer

Last Answer : (C) Reynolds number in mass transfer is analogous to Grashoff number in heat transfer

Nusselt number (for forced convection heat transfer) is a function of the __________ number. (A) Prandtl (B) Reynolds (C) Both (A) & (B) (D) Neither (A) nor (B)

Description : Nusselt number (for forced convection heat transfer) is a function of the __________ number. (A) Prandtl (B) Reynolds (C) Both (A) & (B) (D) Neither (A) nor (B)

Last Answer : (C) Both (A) & (B)

jH factor for heat transfer is not a function of the __________ number. (A) Reynolds (B) Nusselt (C) Grashoff (D) Both (B) & (C)

Description : jH factor for heat transfer is not a function of the __________ number. (A) Reynolds (B) Nusselt (C) Grashoff (D) Both (B) & (C)

Last Answer : (D) Both (B) & (C)

Which of the following is concerned with both heat and mass transfer? (A) Lewis relationship (B) Nusselt number (C) Kutateladze number (D) Froude number

Description : Which of the following is concerned with both heat and mass transfer? (A) Lewis relationship (B) Nusselt number (C) Kutateladze number (D) Froude number

Last Answer : (A) Lewis relationship

The rate of heat transfer is a product of overall heat transfer co￾efficient, the difference in temperature and the (A) Heating volume (B) Heat transfer area (C) Nusselt number (D) None of these

Description : The rate of heat transfer is a product of overall heat transfer co￾efficient, the difference in temperature and the (A) Heating volume (B) Heat transfer area (C) Nusselt number (D) None of these

Last Answer : (B) Heat transfer area

jH factor for heat transfer depends upon the __________ number. (A) Biot (B) Nusselt (C) Reynolds (D) Prandtl

Description : jH factor for heat transfer depends upon the __________ number. (A) Biot (B) Nusselt (C) Reynolds (D) Prandtl

Last Answer : (C) Reynolds

Pick out the wrong statement. (A) In drying a solid containing moisture above the critical moisture content the number of degrees of freedom is 2 (B) Sherwood number in mass transfer corresponds to Nusselt number in heat transfer and Schmidt number to Prandtl number (C) Forced convection is relatively more effective in increasing the rate of mass transfer, if Schmidt number is larger (D) Hot gases at moderate pressure are usually in the shell side of shell and tube heat exchangers. At higher pressure, however, it is customary to put gas in the tube side

Description : Pick out the wrong statement. (A) In drying a solid containing moisture above the critical moisture content the number of degrees of freedom is 2 (B) Sherwood number in mass transfer corresponds to ... tube heat exchangers. At higher pressure, however, it is customary to put gas in the tube side

Last Answer : (C) Forced convection is relatively more effective in increasing the rate of mass transfer, if Schmidt number is larger

The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is (A) Nusselt number (B) Sherwood number (C) Schmidt number (D) Stanton numbe

Description : The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is (A) Nusselt number (B) Sherwood number (C) Schmidt number (D) Stanton numbe

Last Answer : (C) Schmidt number

Nusselt number is a function of Prandtl number and __________ number of fluid in natural convection heat transfer. (A) Grashoff (B) Biot (C) Stanton

Description : Nusselt number is a function of Prandtl number and __________ number of fluid in natural convection heat transfer. (A) Grashoff (B) Biot (C) Stanton

Last Answer : (A) Grashoff

Nusselt number/Biot number varies (A) Inversely with thermal conductivity (B) Directly with heat transfer co-efficient (C) Directly with thermal conductivity (D) Inversely with the dimension of the solid

Description : Nusselt number/Biot number varies (A) Inversely with thermal conductivity (B) Directly with heat transfer co-efficient (C) Directly with thermal conductivity (D) Inversely with the dimension of the solid

Last Answer : (A) Inversely with thermal conductivity

The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) (A) K/h0 (B) 2K/h0 (C) h0 /K (D) h0 /2K

Description : The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) (A) K/h0 (B) 2K/h0 (C) h0 /K (D) h0 /2K

Last Answer : (B) 2K/h0

Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids? (A) Dittus-Boelter equation (B) Sieder-Tate equation (C) Nusselt equation (D) None of these

Description : Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids? (A) Dittus-Boelter equation (B) Sieder-Tate equation (C) Nusselt equation (D) None of these

Last Answer : (B) Sieder-Tate equation

Pick out the wrong statement. (A) A particular chemical reaction is more temperature sensitive at low temperatures (B) A very high value of equilibrium constant, K (K >> 1) indicates that the reaction is practically irreversible in nature (C) The intercept of the Arrhenius plot is called the 'activation energy' (D) Non-ideal flow takes place in reactors due to recycling, channeling or by creation of stagnant regions

Description : Pick out the wrong statement. (A) A particular chemical reaction is more temperature sensitive at low temperatures (B) A very high value of equilibrium constant, K (K >> 1) indicates that the ... ) Non-ideal flow takes place in reactors due to recycling, channeling or by creation of stagnant regions

Last Answer : (C) The intercept of the Arrhenius plot is called the 'activation energy

The settling velocity of a spherical particle of diameter less than 0.1 mm as per Stock’s law, is A. Vs = 418 (Gs – Gw) d [(3T + 70)/100] B. Vs = 418 (Gs – Gw)d² [(3T + 70)/100] C. Vs = 218 (Gs – Gw)d² [(3T + 70)/100] D. Vs = 218 (Gs – Gw)d [(3T + 70)/100]

Description : The settling velocity of a spherical particle of diameter less than 0.1 mm as per Stock’s law, is A. Vs = 418 (Gs – Gw) d [(3T + 70)/100] B. Vs = 418 (Gs – Gw)d² [(3T + 70)/100] C. Vs = 218 (Gs – Gw)d² [(3T + 70)/100] D. Vs = 218 (Gs – Gw)d [(3T + 70)/100]

Last Answer : ANS: B

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 (A) 5.6 (B) 0.025 (C) 3.5 (D) 0.0035

Description : 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 (A) 5.6 (B) 0.025 (C) 3.5 (D) 0.0035

Last Answer : (B) 0.025

A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle system (in SI units) is given below : Δ P/L = 375 × 10 3 VOM + 10.94 × 10 6 V2 OM (SI units) If water is to be used as the fluidising medium, the minimum fluidisation velocity, VOM is (A) 12 mm/s (B) 16 mm/s (C) 24 mm/s (D) 28 mm/s

Description : A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle ... fluidisation velocity, VOM is (A) 12 mm/s (B) 16 mm/s (C) 24 mm/s (D) 28 mm/s

Last Answer : (B) 16 mm/s

A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle system (in SI units) is given below: Δ P/L = 375 × 10 3 VOM + 10.94 × 10 6 V2 OM (SI units) If water is to be used as the fluidising medium, in actual operation, the above bed has a height = 1 m. What is the porosity of the fluidised bed? (A) 0.2 (B) 0.5 (C) 0.7 (D) 0.8

Description : A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle system ... What is the porosity of the fluidised bed? (A) 0.2 (B) 0.5 (C) 0.7 (D) 0.8

Last Answer : (C) 0.7

The equation, (h.D/K) is called the __________ number. (A) Nusselt (B) Peclet (C) Rayleigh (D) Grashoff

Description : The equation, (h.D/K) is called the __________ number. (A) Nusselt (B) Peclet (C) Rayleigh (D) Grashoff

Last Answer : (A) Nusselt

Cpµ/K is termed as the __________ number. (A) Grashoff (B) Nusselt (C) Prandtl (D) Stanton

Description : Cpµ/K is termed as the __________ number. (A) Grashoff (B) Nusselt (C) Prandtl (D) Stanton

Last Answer : (C) Prandtl

Nusselt number for full developed, laminar, constant property flow in a pipe at uniform heat flux is (A) 0.72 (B) 4.364 (C) 18 (D) 83

Description : Nusselt number for full developed, laminar, constant property flow in a pipe at uniform heat flux is (A) 0.72 (B) 4.364 (C) 18 (D) 83

Last Answer : (B) 4.364

Sphericity is the ratio of the surface area of a spherical particle having the same volume as the particle to the surface area of the particle. Which of the following has the maximum value of sphericity? (A) Sphere(B) Cube(C) Cylinder (L/D = 1)(D) Raschig rings

Description : Sphericity is the ratio of the surface area of a spherical particle having the same volume as the particle to the surface area of the particle. Which of the following has the maximum value of sphericity? (A) Sphere (B) Cube (C) Cylinder (L/D = 1) (D) Raschig rings

Last Answer : (A) Sphere

Component A is diffusing in a medium B. The flux NA relative to a stationary point is equal to the flux due to molecular diffusion, if (A) Mass transfer is accompanied by reaction (B) Diffusion of A is in stagnant medium B (C) Molecular mean free path is high (D) There is equimolar counter diffusion

Description : Component A is diffusing in a medium B. The flux NA relative to a stationary point is equal to the flux due to molecular diffusion, if (A) Mass transfer is accompanied by reaction (B ... stagnant medium B (C) Molecular mean free path is high (D) There is equimolar counter diffusion

Last Answer : (D) There is equimolar counter diffusion

The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving force. and, Kp= M.T.C. for diffusion of a gas through a stagnant inert gas with pressure as driving force.) (A) Kc = Kp = Km (B) Kc = Kp /RT = Km . RT/P (C) Kc = Kp . RT = Km . RT/p (D) None of these

Description : The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving ... (C) Kc = Kp . RT = Km . RT/p (D) None of these

Last Answer : (C) Kc = Kp . RT = Km . RT/p

Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the (A) Surrounding temperature (B) Average temperature of the fin (C) Temperature of the fin end (D) Constant temperature equal to that of the base

Description : Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer ... (C) Temperature of the fin end (D) Constant temperature equal to that of the base

Last Answer : (D) Constant temperature equal to that of the base

Heat transfer takes place through a liquid medium surrounding the submerged material under heating, in case of a/an (A) Blast furnace (B) Steam boiler (C) Salt bath furnace (D) Annealing furnace

Description : Heat transfer takes place through a liquid medium surrounding the submerged material under heating, in case of a/an (A) Blast furnace (B) Steam boiler (C) Salt bath furnace (D) Annealing furnace

Last Answer : (C) Salt bath furnace

The second law of thermodynamics states that (A) The energy change of a system undergoing any reversible process is zero (B) It is not possible to transfer heat from a lower temperature to a higher temperature (C) The total energy of system and surrounding remains the same (D) None of the above

Description : The second law of thermodynamics states that (A) The energy change of a system undergoing any reversible process is zero (B) It is not possible to transfer heat from a lower temperature to a higher temperature (C) The total energy of system and surrounding remains the same (D) None of the above

Last Answer : (D) None of the above

For the free settling of a spherical particle through a fluid, the slope of, CD-log NRe , plot is (A) 1(B) -1 (C) 0.5 (D) -0.5

Description : For the free settling of a spherical particle through a fluid, the slope of, CD-log NRe , plot is (A) 1 (B) -1 (C) 0.5 (D) -0.5

Last Answer : (B) -1

For condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively hf and hd , then (A) hf = hd (B) hf > hd (C) hf < hd (D) hf could be greater or smaller than hd

Description :  For condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively hf and hd , then (A) hf = hd (B) hf > hd (C) hf < hd (D) hf could be greater or smaller than hd

Last Answer : (C) hf < hd

Nusselt number is the ratio of the temperature gradient at the wall to (A) Temperature difference (B) Heat flux (C) That across the entire pipe (D) None of these

Description : Nusselt number is the ratio of the temperature gradient at the wall to (A) Temperature difference (B) Heat flux (C) That across the entire pipe (D) None of these

Last Answer : (C) That across the entire pipe

The non-dimensional temperature gradient in a liquid at the wall of a pipe is the (A) Heat flux (B) Nusselt number (C) Prandtl number (D) Schmidt number

Description : The non-dimensional temperature gradient in a liquid at the wall of a pipe is the (A) Heat flux (B) Nusselt number (C) Prandtl number (D) Schmidt number

Last Answer : (A) Heat flux

The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is(A) 2.36(B) 4.36(C) 120.36(D) Dependent on NRe only

Description : The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is (A) 2.36 (B) 4.36 (C) 120.36 (D) Dependent on NRe only

Last Answer : (B) 4.36

Nusselt number is the ratio of the (A) Temperature gradient of the wall to that across the entire pipe (B) Temperature difference to the temperature gradient at the wall (C) Heat flux at the wall to that across the entire pipe (D) None of these

Description : Nusselt number is the ratio of the (A) Temperature gradient of the wall to that across the entire pipe (B) Temperature difference to the temperature gradient at the wall (C) Heat flux at the wall to that across the entire pipe (D) None of these

Last Answer : (C) Heat flux at the wall to that across the entire pipe

In Newton's law range, the drag co-efficient for the motion of spherical particle in a stationary fluid is (A) 0.44 (B) 0.044 (C) 4.4 (D) 44

Description : In Newton's law range, the drag co-efficient for the motion of spherical particle in a stationary fluid is (A) 0.44 (B) 0.044 (C) 4.4 (D) 44

Last Answer : (A) 0.44

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) < 2100 (B) 2100-4000 (C) > 4000 (D) > 10000

Description : 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) < 2100 (B) 2100-4000 (C) > 4000 (D) > 10000

Last Answer : (D) > 10000

The Reynolds number of the liquid was increased 100 fold for a laminar falling film used for gas-liquid contacting. Assuming penetrating theory is applicable, the fold increase in the mass transfer co-efficient (Kc ) for the same system is(A) 100(B) 10(C) 5(D) 1.

Description : The Reynolds number of the liquid was increased 100 fold for a laminar falling film used for gas-liquid contacting. Assuming penetrating theory is applicable, the fold increase in the mass transfer co-efficient (Kc ) for the same system is. (A) 100 (B) 10 (C) 5 (D) 1

Last Answer : (B) 10

In a boiling curve, the peak heat flux is called the __________ point. (A) Nusselt (B) Leidenfrost (C) Boiling (D) Burnout

Description : In a boiling curve, the peak heat flux is called the __________ point. (A) Nusselt (B) Leidenfrost (C) Boiling (D) Burnout

Last Answer : (D) Burnout

A spherical particle is falling slow in a viscous liquid such that Reynolds number is less than 1. Which statement is correct for this situation? (A) Inertial and drag forces are important (B) Drag, gravitational and buoyancy forces are important (C) Drag force and gravitational forces are important (D) None of the above

Description : A spherical particle is falling slow in a viscous liquid such that Reynolds number is less than 1. Which statement is correct for this situation? (A) Inertial and drag forces are important (B) Drag ... forces are important (C) Drag force and gravitational forces are important (D) None of the above

Last Answer : (B) Drag, gravitational and buoyancy forces are important

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/m2 .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

Description : 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 ... temperature of the right face in °C is (A) 77.2 (B) 71.2 (C) 63.8 (D) 48.7

Last Answer : (D) 48.7