In case of cooling towers, the ratio of the rates of heat and mass transfer is indicated by the __________ number. (A) Lewis (B) Grashoff (C) Sherwood

In case of cooling towers, the ratio of the rates of heat and mass transfer

is indicated by the __________ number.

(A) Lewis

(B) Grashoff

(C) Sherwood

by

1 Answer

Answer :

(A) Lewis


by

Related questions

__________ number indicates the ratio of the rates of the heat and mass transfer incase of a cooling tower. (A) Sherwood (B) Stanton (C) Lewis (D) Peclet

Description : __________ number indicates the ratio of the rates of the heat and mass transfer incase of a cooling tower. (A) Sherwood (B) Stanton (C) Lewis (D) Peclet

Last Answer : (C) Lewis

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

Which of the following is directly concerned with the heat transfer? (A) Strouhal number (B) Sherwood number (C) Euler number (D) Grashoff number

Description : Which of the following is directly concerned with the heat transfer? (A) Strouhal number (B) Sherwood number (C) Euler number (D) Grashoff number

Last Answer : (D) Grashoff number

Which of the following plays an important role in problems of simultaneous heat and mass transfer?(A) Lewis number (B) Schmidt number (C) Prandtl number (D) Sherwood number

Description : Which of the following plays an important role in problems of simultaneous heat and mass transfer (A) Lewis number (B) Schmidt number (C) Prandtl number (D) Sherwood number

Last Answer : (A) Lewis number

Pick out the wrong statement. (A) The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one (B) Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference (C) According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(B)P - 3, Q - 2 (D) The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz

Description : Pick out the wrong statement. (A) The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one (B) Sherwood number for flow in pipes can be expressed ... flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz

Last Answer : (C) According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(B)P - 3, Q - 2

Which is not concerned directly with mass transfer? (A) Schmidt number (B) Sherwood number (C) Lewis relationship (D) Froude number

Description : Which is not concerned directly with mass transfer? (A) Schmidt number (B) Sherwood number (C) Lewis relationship (D) Froude number

Last Answer : (D) Froude number

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

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

Last Answer : (A) Schmidt

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

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Last Answer : (A) Sherwood

NSc /NPr is called the (A) Psychrometric ratio (B) Lewis number (C) Sherwood number (D) Stanton number

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Last Answer : (B) Lewis number

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

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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

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Last Answer : (C) Schmidt number

(NRe . NSc ) is termed in mass transfer operation as the __________ number. (A) Stanton (B) Sherwood (C) Peclet (D) None of these

Description : (NRe . NSc ) is termed in mass transfer operation as the __________ number. (A) Stanton (B) Sherwood (C) Peclet (D) None of these

Last Answer : (C) Peclet

When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is: (A) Free convection (B) Entry length problem in laminar forced conduction (developing thermal boundary layer) (C) Mixed convection (both free and forced) (D) Forced convection

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Last Answer : (C) Mixed convection (both free and forced)

Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of (A) Mass diffusivity to momentum diffusivity (B) Thermal diffusivity to mass diffusivity (C) Momentum diffusivity to thermal diffusivity (D) None of these

Description : Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of (A) Mass diffusivity to momentum diffusivity (B) Thermal diffusivity to mass diffusivity (C) Momentum diffusivity to thermal diffusivity (D) None of these

Last Answer : (B) Thermal diffusivity to mass diffusivity

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)

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

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Last Answer : (A) Grashoff

Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer. (A) Grashoff (B) Reynolds (C) Both 'a' & 'b' (D) Prandtl & Grashoff

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Last Answer : (D) Prandtl & Grashoff

Pick out the wrong statement. (A) With decrease in feed temperature, the number of plates required for binary distillation decreases for a given ‘L/V’ ratio (B) The extraction per unit of total height for a short packed column is more effective than for a tall column, in case of liquid-liquid extraction(C) Natural draft cooling towers are made of ferroconcrete and its cross￾section is wider at the bottom(D) Vander wall adsorption is also called chemisorption

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Last Answer : (D) Vander wall adsorption is also called chemisorption

For turbulent mass transfer in pipes, the Sherwood number depends on the Reynolds number as (A) Re 0.33 (B) Re 0.53 (C) Re 0.83 (D) Re

Description : For turbulent mass transfer in pipes, the Sherwood number depends on the Reynolds number as (A) Re 0.33 (B) Re 0.53 (C) Re 0.83 (D) Re

Last Answer : (C) Re 0.83

Cooling towers operate through a ____process that efficiently cools the already cycled water to be reused. 1. Heat exchange 2. Heat expand 3. Heat transfer 4. None of above

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Last Answer : Heat transfer

In natural convection heat transfer, the correlating parameter is the (A) Graetz number (B) Eckert number (C) Grashoff number (D) Bond number

Description : In natural convection heat transfer, the correlating parameter is the (A) Graetz number (B) Eckert number (C) Grashoff number (D) Bond number

Last Answer : (C) Grashoff number

The Dittus-Boelter equation for convective heat transfer [(i.e. h = 0.023 (K/D) (Re) 0.8 (Pr) 0.4 ] cannot be used for (A) Low Reynold's number (B) Very low Grashoff number (C) Molten metals (D) All (A), (B) and (C)

Description : The Dittus-Boelter equation for convective heat transfer [(i.e. h = 0.023 (K/D) (Re) 0.8 (Pr) 0.4 ] cannot be used for (A) Low Reynold's number (B) Very low Grashoff number (C) Molten metals (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Dittus-Boelter equation used for the determination of heat transfer co￾efficient is valid (A) For fluids in laminar flow (B) For fluids in turbulent flow (C) When Grashoff number is very important (D) For liquid metals

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Last Answer : (B) For fluids in turbulent flow

Pick out the correct statement. (A) 1 kcal/hr.m.°C is equal to 1 BTU/hr. ft.°F (B) In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity (C) In unsteady state heat conduction, heat flows in the direction of temperature rise (D) In heat transfer by forced convection, Grashoff number is very important

Description : Pick out the correct statement. (A) 1 kcal/hr.m.°C is equal to 1 BTU/hr. ft.°F (B) In steady state heat conduction, the only property of the substance which determines the ... in the direction of temperature rise (D) In heat transfer by forced convection, Grashoff number is very important

Last Answer : (B) In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity

Transition from laminar to turbulent zone in free convection heat transfer is governed by the critical value of (A) Grashoff number (B) Grashoff number & Reynolds number (C) Reynolds number (D) Grashoff number & Prandtl number

Description : Transition from laminar to turbulent zone in free convection heat transfer is governed by the critical value of (A) Grashoff number (B) Grashoff number & Reynolds number (C) Reynolds number (D) Grashoff number & Prandtl number

Last Answer : Option D

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

Pick out the wrong statement. (A) Mechanical agitation is required, if the system has low interfacial tension (B) Sieve tray towers are generally used for systems having low interfacial tension (C) When Henry's law constant is very small, then the mass transfer rate is controlled by the gas film resistance (D) Taylor-Prandtl analogy for heat and mass transfer considers the transfer through both laminar and turbulent layers

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Last Answer : (A) Mechanical agitation is required, if the system has low interfacial tension

The __________ that are present depend on cooling tower building material, as well. Cooling towers are built of concrete, wood, plastic or metal. a. Heat b. Pollutants c. Cold d. All of Above

Description : The __________ that are present depend on cooling tower building material, as well. Cooling towers are built of concrete, wood, plastic or metal. a. Heat b. Pollutants c. Cold d. All of Above

Last Answer : b. Pollutants

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. (A) Condensation (B) Grashoff (C) Stanton (D) Brinkman

Description : 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. (A) Condensation (B) Grashoff (C) Stanton (D) Brinkman

Last Answer : (D) Brinkman

The ratio of momentum diffusivity to thermal diffusivity is the __________ number. (A) Prandtl (B) Nusselt (C) Stanton (D) Grashoff

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Last Answer : (A) Prandtl

Pick out the wrong statement pertaining to the cooling towers. (A) In case of induced draft cooling tower, the fan is placed at the top of the tower (B) Effectiveness of forced draft cooling tower is reduced by the recirculation of the humid and hot discharged air (C) A natural draft cooling tower is recommended to be used, when the air humidity is low and air temperature is also low (D) Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature

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Last Answer : (D) Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature

Which one of the following fill material is more energy efficient for cooling towers in case of sea water cooling? • Splash fill • Film fill • Low clog film fill • None of the above

Description : Which one of the following fill material is more energy efficient for cooling towers in case of sea water cooling? • Splash fill • Film fill • Low clog film fill • None of the above

Last Answer : Film fill

Pick out the wrong statement. (A) 'Solvates' are chemical compounds formed by solute with their solvents. When water is the solvent, then it is called a 'hydrate' (B) In heat exchanger calculations (Δt) weighted is used in place of Δt, when it involves more than one sequence of heating or cooling i.e., desuperheating & condensation or condensation & sub-cooling (C) Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted (D) In case of short tube vertical evaporators, area of central downtake is about 50 to 100% of the total tube cross-sectional area

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Last Answer : (C) Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted

In case of a close thermodynamic system, there is __________ across the boundaries. (A) No heat and mass transfer (B) No mass transfer but heat transfer (C) Mass and energy transfer (D) None of these

Description : In case of a close thermodynamic system, there is __________ across the boundaries. (A) No heat and mass transfer (B) No mass transfer but heat transfer (C) Mass and energy transfer (D) None of these

Last Answer : (B) No mass transfer but heat transfer

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

Description : 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) ... the outlet temperature of cooling medium (C) Increases the overall heat transfer coefficient (D) None of these

Last Answer : (C) Increases the overall heat transfer coefficient

__________ Cooling towers have become the design standard for all natural-draft cooling towers because oftheir structural strength and minimum usage of material. • HCT • CCT • Hyperboloid • None

Description : __________ Cooling towers have become the design standard for all natural-draft cooling towers because oftheir structural strength and minimum usage of material. • HCT • CCT • Hyperboloid • None

Last Answer : Hyperboloid

Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. (A) Laminar (B) Transition (C) Both 'a' & 'b' (D) Highly turbulent

Description : Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. (A) Laminar (B) Transition (C) Both 'a' & 'b' (D) Highly turbulent

Last Answer : (D) Highly turbulent

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

Water entrained by circulating air in cooling towers is termed as (A) Drift (B) Blow down (C) Vapor load (D) None of these

Description : Water entrained by circulating air in cooling towers is termed as (A) Drift (B) Blow down (C) Vapor load (D) None of these

Last Answer : (A) Drift

Air intake for an air compressor should be preferably taken from (A) A site, where cooling towers are located nearby (B) A site, where open coal yard in located nearby (C) An air conditioned room maintained at a temperature of 18°C (D) An outside atmosphere at 10°C

Description : Air intake for an air compressor should be preferably taken from (A) A site, where cooling towers are located nearby (B) A site, where open coal yard in located nearby (C) An air conditioned room maintained at a temperature of 18°C (D) An outside atmosphere at 10°C

Last Answer : (D) An outside atmosphere at 10°C

Turndown ratio of a burner gives an idea of the __________ in the furnace. (A) Range of fuel firing rates (B) Volume of the combustion chamber (C) Maximum heat input rate only (D) Minimum heat input rate only

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Last Answer : (A) Range of fuel firing rates

Pick out the wrong statement. (A) Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection (B) The ratio NNu /NRe . Npr is called the Stanton number (C) The Peclet number is a measure of the ratio of energy transport by convection to that by conduction (D) The Colburn jH factor for heat transfer is given by Nst Npr

Description : Pick out the wrong statement. (A) Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection (B) The ratio NNu /NRe . Npr is ... convection to that by conduction (D) The Colburn jH factor for heat transfer is given by Nst Npr

Last Answer : (D) The Colburn jH factor for heat transfer is given by Nst Npr

Analogy between mass and heat transfer is not applicable in case of (A) Same velocity profile or equal eddy diffusivities (B) Thermal or pressure mass diffusion (C) Viscous heating or chemical reaction (D) Both (B) and (C)

Description : Analogy between mass and heat transfer is not applicable in case of (A) Same velocity profile or equal eddy diffusivities (B) Thermal or pressure mass diffusion (C) Viscous heating or chemical reaction (D) Both (B) and (C)

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

The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by __________ times, when the number of tube passes is increased to 8. (A) 2 0.8 (B) 4 0.8 (C) 4 0.4 (D) 2 0.4

Description : The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by __________ times, when the number of tube passes is increased to 8. (A) 2 0.8 (B) 4 0.8 (C) 4 0.4 (D) 2 0.4

Last Answer : (B) 4 0.8

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

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

Pick out the wrong statement. (A) In a first order reaction, A → products; the reaction becomes slower as it proceeds, because the concentration of A decreases and the rate is proportional to the concentration of A (B) Transition state theory approaches the problem of calculating reaction rates by concentrating on the idea of activated complexes (C) According to the penetration theory, the mass transfer co-efficient decreases, if the exposure time of an eddy to the solute decreases (D) If the rate of an irreversible reaction, A + B → 2C is k.CA .CB , then the reaction is always elementary

Description : Pick out the wrong statement. (A) In a first order reaction, A → products; the reaction becomes slower as it proceeds, because the concentration of A decreases and the rate is proportional to the concentration ... irreversible reaction, A + B → 2C is k.CA .CB , then the reaction is always elementary

Last Answer : (C) According to the penetration theory, the mass transfer co-efficient decreases, if the exposure time of an eddy to the solute decreases

Cooling towers are rated in terms of A. approach B. range C. both of the mentioned D. none of the mentioned

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Last Answer : ANSWER :C

Why cooling towers require in the Steam power plant ?

Description : Why cooling towers require in the Steam power plant ?

Last Answer : Cooling towers cool the warm water discharged from the condenser and feed the cooled water back to the condenser. There are two types of cooling methods provided in the cooling towers, they can be either ... finned tubes over which cooling air is passed. Heat is rejected to air as water is cooled