GATE CH topic:process-engineering PYQs & Answers — Page 45

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Questions 441–450 of 650. Imported answers require independent review unless marked reviewed.

Topic practice 650 questionsPage 45 of 65

A fluid is heated from 40 °C to 60 °C in a countercurrent, double pipe heat exchanger. Hot fluid enters at 100 °C and exits at 70 °C. The log mean temperature difference, i.e. LMTD (in °C), is __________ (round off to 2 decimal places).

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Consider an infinitely long rectangular fin exposed to a surrounding fluid at a constant temperature

. The figure shows the fin.

Diagram for Chemical Engineering question 42

The steady state one dimensional energy balance on an element of the fin of thickness

at a distance

from its base yields

where

is the temperature of the fin at the distance

from its base in °C. The value of

is 0.04 cm

and the temperature at the base is

. The temperature (in °C) at

cm is ________ (round off to 1 decimal place).

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Liquid water is pumped at a volumetric flow rate of 0.02 m

from Tank I to Tank II, as shown in the figure.

Diagram for Chemical Engineering question 43

Both the tanks are open to the atmosphere. The total frictional head loss for the pipe system is 1.0 m of water.

In addition, use the following data and assumptions:

Density of water is 1000 kg m

Acceleration due to gravity is 9.81 m s

Efficiency of the pump is 100%

The liquid surfaces in the tanks have negligible velocities

The power supplied (in W) by the pump to lift the water is ________ (round off to 1 decimal place).

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An elementary liquid phase reversible reaction

is carried out in an ideal continuous stirred tank reactor (CSTR) operated at steady state. The rate of consumption of P,

(in mol liter

minute

), is given by

where

and

are the concentrations (in mol liter

) of P and Q, respectively.

The feed contains only the reactant P at a concentration of 1 mol liter

, and the conversion of P at the exit of the CSTR is 75% of the equilibrium conversion. Assume that there is no volume change associated with the reaction, and the temperature of the reaction mixture is constant throughout the operation. The space time (in minutes) of the CSTR is ________ (round off to 1 decimal place).

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An aqueous suspension at 60 °C is fed to the first effect of a double effect forward feed evaporator with a mass flow rate of 1.25 kg s

. The sum of the rates of water evaporated from the first and second effects is 1.0 kg s

. Temperatures of the exit streams from the first and the second effects are 100 °C, and 60 °C, respectively. Consider the specific heat of the aqueous suspension, and the latent heat of phase change for water to be 4 kJ kg

and 2200 kJ kg

, respectively, over this temperature range. The steam economy (in kg per kg) is ________ (round off to 2 decimal places).

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A vertically held packed bed has a height of 1 m, and a void fraction of 0.1, when there is no flow through the bed. The incipient (minimum) fluidization is set in by injection of a fluid of density 1 kg m

. The particle density (

) of the solids is 3000 kg m

. Acceleration due to gravity is 9.81 m s

. The pressure drop (in Pa) across the height of the bed is ________ (round off to nearest integer).

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Two ideal cross-current stages operate to extract P from a feed containing P and Q, as shown below.

Diagram for Chemical Engineering question 47

The mass flow rates of P and Q fed to Stage 1 are 1,000 kg h

and 10,000 kg h

, respectively. Pure solvent (S) is injected at mass flow rates of 5,000 kg h

and 15,000 kg h

to Stages 1 and 2, respectively. The components Q and S are immiscible. The equilibrium relation is given by

, where

is the mass of P per unit mass of Q in the raffinate, and

is the mass of P per unit mass of S in the extract, which is in equilibrium with the raffinate. The mass flow rate of P (in kg h

) in the raffinate from Stage 2 is ________ (round off to nearest integer).

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Consider a vertically falling film of water over an impermeable wall. The film is in contact with a static pool of non-reactive pure gas. The gas diffuses into the water film over the entire height of the falling film. The height of the film is 1.0 m, and its thickness is

m. The velocity of water, averaged over the film thickness, is 0.01 m s

. The gas concentration (in kg m

), averaged over the film thickness is

where

is the vertical position in meters measured from the top of the wall.

In addition, use the following data and assumptions:

The flow is fully developed

The width of the film is much larger than the thickness of the film, and the dissolved gas concentration is invariant over this width

The solubility of the gas in water,

, is constant

Pure water enters at

The evaporation of water is negligible

The mass transfer coefficient on the liquid side (in mm s

), averaged over the entire height of the falling film is ________ (round off to 3 decimal places).

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An exothermic, aqueous phase, irreversible, first order reaction,

is carried out in an ideal continuous stirred tank reactor (CSTR) operated adiabatically at steady state. Rate of consumption of Y (in mol liter

minute

) is given by

where

is the concentration of Y (in mol liter

), and

is the temperature of the reaction mixture (in K). Reactant Y is fed at 50 °C. Its inlet concentration is 1.0 mol liter

, and its volumetric flow rate is 1.0 liter minute

In addition, use the following data and assumptions:

Heat of the reaction = −4200 J mol

Specific heat capacity of the reaction mixture = 4.2 J g

Density of the reaction mixture = 1000 g liter

Heat of the reaction, specific heat capacity and density of the reaction mixture do not vary with temperature

Shaft work is negligible

If the conversion of Y at the exit of the reactor is 90%, the volume of the CSTR (in liter) is ________ (round off to 2 decimal places).

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The liquid phase irreversible reactions,

and

, are carried out in an ideal continuous stirred tank reactor (CSTR) operating isothermally at steady state. The space time of the CSTR is 1 minute. Both the reactions are first order with respect to the reactant P, and

and

denote the rate constants of the two reactions. At the exit of the reactor, the conversion of reactant P is 60%, and the selectivity of Q with respect to R is 50%. The value of the first order rate constant

(in minute

) is ________ (correct up to one decimal place).

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GATE CH topic:process-engineering PYQs

Question 41

Question 42

Question 43

Question 44

Question 45

Question 46

Question 47

Question 48

Question 49

Question 50