In the constant rate period of the rate of drying curve for batch drying, (A) Cracks develop on the surface of the solid (B) Rate of drying decreases abruptly (C) Surface evaporation of unbound moisture occurs (D) None of these

In the constant rate period of the rate of drying curve for batch drying,

(A) Cracks develop on the surface of the solid

(B) Rate of drying decreases abruptly

(C) Surface evaporation of unbound moisture occurs

(D) None of these

by

1 Answer

Answer :

(C) Surface evaporation of unbound moisture occurs

by

Related questions

During the constant rate period of drying of a solid, (A) Increased air humidity decreases the rate of drying (B) Increasing the air temperature decreases the drying rate (C) Surface evaporation of unbound moisture occurs (D) None of these

Description : During the constant rate period of drying of a solid, (A) Increased air humidity decreases the rate of drying (B) Increasing the air temperature decreases the drying rate (C) Surface evaporation of unbound moisture occurs (D) None of these

Last Answer : (C) Surface evaporation of unbound moisture occurs

The drying time between fixed moisture contents within the 'constant rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid). (A) √T (B) T (C) T 1.5 (D) T

Description : The drying time between fixed moisture contents within the 'constant rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid). (A) √T (B) T (C) T 1.5 (D) T

Last Answer : (B) T

The drying time between fixed moisture content within diffusion controlled 'falling rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid). (A) √T (B) T (C) T 2 (D) T

Description : The drying time between fixed moisture content within diffusion controlled 'falling rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid). (A) √T (B) T (C) T 2 (D) T

Last Answer : (C) T

Pick out the correct statement. (A) Bound moisture is removed during constant rate drying period (B) Free moisture is removed during falling rate drying period (C) The sum of free moisture and equilibrium moisture in a solid is called the critical moisture (D) The driving force for mass transfer in a wet solid is its free moisture content

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Last Answer : (D) The driving force for mass transfer in a wet solid is its free moisture content

Drying operation under vacuum is carried out to (A) Dry those materials which have very high unbound moisture content (B) Reduce drying temperature (C) Increase drying temperature (D) Dry materials having high bound moisture content

Description : Drying operation under vacuum is carried out to (A) Dry those materials which have very high unbound moisture content (B) Reduce drying temperature (C) Increase drying temperature (D) Dry materials having high bound moisture content

Last Answer : (B) Reduce drying temperature

During drying operation, it is easier to remove the __________ moisture. (A) Equilibrium (B) Critical (C) Unbound (D) Bound

Description : During drying operation, it is easier to remove the __________ moisture. (A) Equilibrium (B) Critical (C) Unbound (D) Bound

Last Answer : (C) Unbound

With increase in the mass velocity of the gas, the rate of drying during the constant rate period __________, if the conduction and radiation through the solid are negligible. (A) Increases (B) Decreases (C) Remain same

Description : With increase in the mass velocity of the gas, the rate of drying during the constant rate period __________, if the conduction and radiation through the solid are negligible. (A) Increases (B) Decreases (C) Remain same

Last Answer : (A) Increases

Occurrence of 'case hardening' during drying of a high moisture solid cake __________ the drying rate. (A) Increases (B) Decreases (C) Does not affect

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Last Answer : (B) Decreases

Moisture in a solid exerting an equilibrium vapour pressure equal to that of the pure liquid at the same temperature is called the __________ moisture. (A) Unbound (B) Critical (C) Free (D) Bound

Description : Moisture in a solid exerting an equilibrium vapour pressure equal to that of the pure liquid at the same temperature is called the __________ moisture. (A) Unbound (B) Critical (C) Free (D) Bound

Last Answer : (A) Unbound

The critical moisture content in case of drying indicates the __________ rate period. (A) Beginning of falling (B) Beginning of constant (C) End of falling (D) None of these

Description : The critical moisture content in case of drying indicates the __________ rate period. (A) Beginning of falling (B) Beginning of constant (C) End of falling (D) None of these

Last Answer : (A) Beginning of falling

Advantage of continuous drying over batch drying is that the (A) Drying cost per unit weight of dried product is less (B) Product with more uniform moisture content is produced (C) Equipment size required is smaller (D) All 'a', 'b' & 'c'

Description : Advantage of continuous drying over batch drying is that the (A) Drying cost per unit weight of dried product is less (B) Product with more uniform moisture content is produced (C) Equipment size required is smaller (D) All 'a', 'b' & 'c'

Last Answer : (D) All 'a', 'b' & 'c'

During constant rate period, the rate of drying decreases with the (A) Decrease in air temperature (B) Increase in air humidity (C) Both (A) and (B) (D) Neither (A) nor (B)

Description : During constant rate period, the rate of drying decreases with the (A) Decrease in air temperature (B) Increase in air humidity (C) Both (A) and (B) (D) Neither (A) nor (B)

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

Mechanism of moisture removal in case of freeze drying of food stuff is by (A) Evaporation (B) Sublimation (C) Dehydration (D) Adsorption

Description : Mechanism of moisture removal in case of freeze drying of food stuff is by (A) Evaporation (B) Sublimation (C) Dehydration (D) Adsorption

Last Answer : (B) Sublimation

During drying of a solid, the critical moisture content increases with (A) Decreased drying rate (B) Increased thickness of the solid (C) Increased drying rate (D) Both (B) and (C)

Description : During drying of a solid, the critical moisture content increases with (A) Decreased drying rate (B) Increased thickness of the solid (C) Increased drying rate (D) Both (B) and (C)

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

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 falling rate period in the drying of a solid is characterised by (A) Increase in rate of drying (B) Increasing temperatures both on the surface and within the solid (C) Decreasing temperatures (D) None of these

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Last Answer : (B) Increasing temperatures both on the surface and within the solid

For __________ drying, the effects of velocity, temperature and humidity of the gas and the thickness of the solid are the same. (A) Unsaturated surface (B) Constant rate (C) Both (A) and (B) (D) Neither (A) nor (B)

Description : For __________ drying, the effects of velocity, temperature and humidity of the gas and the thickness of the solid are the same. (A) Unsaturated surface (B) Constant rate (C) Both (A) and (B) (D) Neither (A) nor (B)

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

n a chemical factory where dyes are made, wet cake at 30 OC consisting of 60% moisture is put in a dryer to obtain an output having only 5% moisture, at atmospheric pressure. In each batch about 120 kgs of material is dried. a. The quantity of moisture removed per batch. b. What is the total quantity ( sensible & latent) of heat required to evaporate the moisture, if the latent heat of water is 540 kcal/kg at atmospheric conditions, Ignore heat absorbed by the solids c. Find the quantity of steam required for the drying process (per batch), if steam at 4 kg/cm2 is used for generating hot air in the dryer and the dryer efficiency is 80%. Latent heat of steam at 4 kg/cm2 is 520 kcal/kg.

Description : n a chemical factory where dyes are made, wet cake at 30 OC consisting of 60% moisture  is put in a dryer to obtain an output having only 5% moisture, at atmospheric pressure. In  each batch about 120 ... dryer and the dryer efficiency  is 80%. Latent heat of steam at 4 kg/cm2 is 520 kcal/kg.

Last Answer : Given that   Qty of material dried per batch - 120 Kgs  Moisture at inlet - 60% a. The quantity of moisture removed per batch.  Water quantity in a wet batch - 120 x 0.6 = 72 Kgs.  Quantity of bone dry ... - 48/0.95 = 50.5 Kgs.  Equivalent water in a dry batch - 50.5 - 48 = 2.5 Kgs.

Moisture in a substance exerting an equilibrium vapour pressure less than that of pure liquid at the same temperature is called the __________ moisture. (A) Bound (B) Unbound (C) Critical (D) None of these

Description : Moisture in a substance exerting an equilibrium vapour pressure less than that of pure liquid at the same temperature is called the __________ moisture. (A) Bound (B) Unbound (C) Critical (D) None of these

Last Answer : (A) Bound

Moisture contained by a substance in excess of the equilibrium moisture is called the __________ moisture. (A) Unbound (B) Free (C) Critical (D) Bound

Description : Moisture contained by a substance in excess of the equilibrium moisture is called the __________ moisture. (A) Unbound (B) Free (C) Critical (D) Bound

Last Answer : (B) Free

All moisture in a non-hygroscopic material is the __________ moisture. (A) Free (B) Equilibrium (C) Unbound (D) Bound

Description : All moisture in a non-hygroscopic material is the __________ moisture. (A) Free (B) Equilibrium (C) Unbound (D) Bound

Last Answer : (C) Unbound

Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the __________ moisture. (A) Free (B) Unbound (C) Equilibrium (D) Bound

Description : Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the __________ moisture. (A) Free (B) Unbound (C) Equilibrium (D) Bound

Last Answer : (C) Equilibrium

It takes 6 hours to dry a wet solid from 50% moisture content to the critical moisture content of 15%. How much longer it will take to dry the solid to 10% moisture content, under the same drying conditions? (The equilibrium moisture content of the solid is 5%). (A) 15 min (B) 51 min (C) 71 min (D) 94 min

Description : It takes 6 hours to dry a wet solid from 50% moisture content to the critical moisture content of 15%. How much longer it will take to dry the solid to 10% moisture content, under the same drying conditions? (The ... 5%). (A) 15 min (B) 51 min (C) 71 min (D) 94 min

Last Answer : (C) 71 min

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Description : Sulphur in metallurgical coal (A) Contributes to its heating value (B) Affects the quality of steel produced as cracks develop on the surface while rolling the steel (C) Both (A) and (B) (D) Neither (A) nor (B)

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

The concentration of A in a first order reaction, A → B, decreases (A) Linearly with time (B) Exponentially with time (C) Very abruptly towards the end of the reaction (D) Logarithmically with time

Description : The concentration of A in a first order reaction, A → B, decreases (A) Linearly with time (B) Exponentially with time (C) Very abruptly towards the end of the reaction (D) Logarithmically with time

Last Answer : (B) Exponentially with time

A screen is said to be blinded, when the (A) Over-sizes are present in undersize fraction (B) Under-sizes are retained in oversize fraction (C) Screen is plugged with solid particles (D) Screen capacity is abruptly increased

Description : A screen is said to be blinded, when the (A) Over-sizes are present in undersize fraction (B) Under-sizes are retained in oversize fraction (C) Screen is plugged with solid particles (D) Screen capacity is abruptly increased

Last Answer : (C) Screen is plugged with solid particles

In batch distillation with constant reflux, overhead product composition __________ with time. (A) Increases (B) Decreases (C) Does not vary (D) May increase on decrease, depends on the system

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Last Answer : (B) Decreases

With lapse of time, the overhead composition of light component in case of batch distillation with constant reflux (A) Increases (B) Decreases (C) Remain same (D) May increase or decrease; depends on system

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The application of plastic mulch? 1. Reduces the surface evaporation 2. Increases the yield of cabbage crop moisture 3.both of these 4. none of these

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Substances whose specific resistance abruptly decreases at very low temperature are called

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Drying of a wet solid under constant drying conditions means the exposure of the wet solid to the air of constant (A) Humidity (B) Velocity (C) Temperature (D) All (A), (B) & (C)

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Swenson-Walker crystalliser is a __________ unit. (A) Continuous (B) Batch (C) Semi-batch (D) Cooling (adiabatic)-cum-evaporation

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Good quality of edible salt is obtained from brine by the process of (A) Solar evaporation (B) Vacuum evaporation (C) Freeze drying (D) Electrolysis

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Description : A solid material shows case hardening properties while drying. Which of the following should be controlled to control the drying process? (A) Flow rate of inlet air (B) Relative humidity of outlet air (C) Humidity of inlet air (D) Temperature of the solid

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Explain the following unit operations: (i) Mixing (ii) Drying (iii) Evaporation (iv) Absorption.

Description : Explain the following unit operations: (i) Mixing (ii) Drying (iii) Evaporation (iv) Absorption.

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Assertion: Black soils are black in colour due to diffusion of iron in crystalline and metamorphic rocks. Reason: They develop deep cracks during hot weather Options: (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true and R is not the correct explanation of A.(c) A is true but B is false. (d) A is false but R is true.

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Last Answer : (d) A is false but R is true.

An R.C.C. beam not provided with shear reinforcement may develop cracks in its bottom inclined roughly to the horizontal at (A) 25° (B) 35° (C) 45° (D) 55°

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Last Answer : Answer: Option C

Which of the following fixes the volume of a batch reactor for a particular conversion and production rate? (A) Operating conditions (e.g. pressure and temperature) (B) Rate constant (C) Density of mixture (D) None of these

Description : Which of the following fixes the volume of a batch reactor for a particular conversion and production rate? (A) Operating conditions (e.g. pressure and temperature) (B) Rate constant (C) Density of mixture (D) None of these

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A second order liquid phase reaction, A → B, is carried out in a mixed flow reactor operated in semi batch mode (no exit stream). The reactant A at concentration CAF is fed to the reactor at a volumetric flow rate of F. The volume of the reacting mixture is V and the density of the liquid mixture is constant. The mass balance for A is (A) d(VCA )/dt = -F (CAF - CA ) - kCA 2V (B) d(VCA )/dt = F (CAF - CA ) - kCA 2V (C) d(VCA )/dt = -FCA - kCA 2V (D) d(VCA )/dt = FCAF - kCA 2V

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