GATE CH format:nat PYQs & Answers — Page 15

Questions 141–150 of 252. Imported answers require independent review unless marked reviewed.

Topic practice 252 questionsPage 15 of 26

Consider a solid slab of thickness 2L and uniform cross section A. The volumetric rate of heat generation within the slab is

(W m

). The slab loses heat by convection at both ends to air with heat transfer coefficient

. Assuming steady state, one-dimensional heat transfer, the temperature profile within the slab along the thickness is given by:

where

is the thermal conductivity of the slab and

is the surface temperature. If

K, ambient air temperature

K, and Biot number (based on L as the characteristic length) is 0.5, the maximum temperature in the slab is ________ K (round off to nearest integer).

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A distillation column handling a binary mixture of A and B is operating at total reflux. It has two ideal stages including the reboiler. The mole fraction of the more volatile component in the residue (

) is 0.1.

The average relative volatility

is 4. The mole fraction of A in the distillate (

) is ________ (round off to 2 decimal places).

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In a batch drying experiment, a solid with a critical moisture content of 0.2 kg H

O/kg dry solid is dried from an initial moisture content of 0.35 kg H

O/kg dry solid to a final moisture content of 0.1 kg H

O/kg dry solid in 5 h. In the constant rate regime, the rate of drying is 2 kg H

O/(m

·h).

The entire falling rate regime is assumed to be uniformly linear. The equilibrium moisture content is assumed to be zero.

The mass of the dry solid per unit area is ________ kg/m

(round off to nearest integer).

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As shown in the figure below, air flows in parallel to a freshly painted solid surface of width 10 m, along the z-direction.

Diagram for Chemical Engineering question 48

The equilibrium vapor concentration of the volatile component A in the paint, at the air-paint interface, is

. The concentration

decreases linearly from this value to zero along the y-direction over a distance

of 0.1 m in the air phase. Over this distance, the average velocity of the air stream is 0.033 m s

and its velocity profile (in m s

) is given by

where y is in meter.

Let

represent the flow averaged concentration. The ratio of

is ________ (round off to 2 decimal places).

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The following isothermal autocatalytic reaction,

is carried out in an ideal continuous stirred tank reactor (CSTR) operating at steady state. Pure A at 1 mol L

is fed, and 90% of A is converted in the CSTR. The space time of the CSTR is ________ seconds.

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Reactant A decomposes to products B and C in the presence of an enzyme in a well-stirred batch reactor. The kinetic rate expression is given by

If the initial concentration of A is 0.02 mol L

, the time taken to achieve 50% conversion of A is ________ min (round off to 2 decimal places).

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The following homogeneous, irreversible reaction involving ideal gases,

is carried out in a steady state ideal plug flow reactor (PFR) operating at isothermal and isobaric conditions. The feed stream consists of pure A, entering at 2 m s

In order to achieve 50% conversion of A, the required length of the PFR is ________ meter (round off to 2 decimal places).

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A system has a transfer function

. When a step change of magnitude M is given to the system input, the final value of the system output is measured to be 120. The value of M is ________.

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A process has a transfer function

. Initially the process is at steady state with

and

. If a step change in x is given from 0.4 to 0.5, the maximum value of y that will be observed before it reaches the new steady state is ________ (round off to 1 decimal place).

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Operating labor requirements L in the chemical process industry is described in terms of the plant capacity C (kg day

) over a wide range (

–

) by a power law relationship

where

and

are constants. It is known that

is 60 when

is 70 when

The value of L when C is

kg day

is ________ (round off to nearest integer).

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GATE CH format:nat PYQs

Question 45

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Question 54