GATE CH year:2025 PYQs & Answers — Page 6

Questions 51–60 of 65. Imported answers require independent review unless marked reviewed.

Topic practice 65 questionsPage 6 of 7

Water flowing at 70 kg/min is heated from 25 °C to 65 °C in a counter-flow double pipe heat exchanger using hot oil. The oil enters at 110 °C and exits at 65 °C. If the overall heat transfer coefficient is 300 W/(m

K), the heat exchanger area is ____ m

(rounded off to 1 decimal place).

GIVEN: Specific heat of water and oil are 4.2 kJ/(kg °C) and 2 kJ/(kg °C), respectively.

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Consider laminar flow of water over a wide flat plate maintained at a uniform temperature of 50 °C as shown in the figure. The freestream velocity and temperature of water are 1.0 m/s (parallel to the plate) and 20 °C, respectively. The distance

from the leading edge, at which the thermal boundary layer thickness

m, is ____ m (rounded off to 1 decimal place).

Diagram for Chemical Engineering question 52

GIVEN: kinematic viscosity:

Prandtl number:

velocity boundary layer thickness:

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An electrical wire of 2 mm diameter and 5 m length is insulated with a plastic layer of thickness 2 mm and thermal conductivity

W/(m K). It is exposed to ambient air at 30 °C. For a current of 5 A, the potential drop across the wire is 2 V. The air-side heat transfer coefficient is 20 W/(m

K). Neglecting the thermal resistance of the wire, the steady state temperature at the wire-insulation interface is ____ °C (rounded off to 1 decimal place).

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A binary

liquid mixture containing 30 mol%

is subjected to differential (Rayleigh) distillation at atmospheric pressure in order to recover 60 mol%

in the distillate. Assuming a constant relative volatility

, the average composition of the collected distillate is ____ mol%

(rounded off to nearest integer).

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Gas containing 0.8 mol% component

is to be scrubbed with pure water in a packed bed column to reduce the concentration of

to 0.1 mol% in the exit gas. The inlet gas and water flow rates are 0.1 kmol/s and 3.0 kmol/s, respectively.

For the dilute system, both the operating and equilibrium curves are considered linear. If the slope of the equilibrium line is 24, the number of transfer units, based on the gas side,

is ____ (rounded off to 1 decimal place).

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Solute

is absorbed from a gas into water in a packed bed operating at steady state. The absorber operating pressure and temperature are 1 atm and 300 K, respectively. At the gas-liquid interface

where

and

are the interfacial gas and liquid mole fractions of

, respectively. At a particular location in the absorber, the mole fractions of

in the bulk gas and in the bulk water are 0.02 and 0.002, respectively. If the ratio of the local individual mass transfer coefficients for the transport of

on the gas-side (

) to that on the water-side (

, then

equals ____ (rounded off to 3 decimal places).

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Components

and

form an azeotrope. The saturation vapour pressures of

and

at the boiling point are 87 kPa and 72.7 kPa, respectively. The azeotrope composition is ____ mol%

(rounded off to the nearest integer).

GIVEN:

where

and

are the liquid phase mole fraction and activity coefficient of component

, respectively.

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The reaction

with reaction rate,

, occurs in an isothermal PFR operating at steady state. The conversion (

) at two axial locations (1 and 2) of the PFR is shown in the figure.

Diagram for Chemical Engineering question 58

The value of

is ____ (rounded off to 2 decimal places).

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The catalytic gas phase reaction

is carried out in an isothermal batch reactor of 10 L volume using 0.1 kg of a solid catalyst. The reaction is first-order with

where

and

is the concentration of

in mol/L.

The catalyst activity

undergoes first order decay with rate constant

per hour and

The reactant conversion after 1 day of operation is ____ (rounded off to 2 decimal places).

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Consider a process with transfer function

A first-order plus dead time (FOPDT) model is to be fitted to the unit step process reaction curve (PRC) by applying the maximum slope method.

Let

and

denote the time constant and dead time, respectively, of the fitted FOPDT model. The value of

is ____ (rounded off to 2 decimal places).

GIVEN: For

the unit step output response:

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GATE CH year:2025 PYQs

Question 51

Question 52

Question 53

Question 54

Question 55

Question 56

Question 57

Question 58

Question 59

Question 60