GATE CH format:nat PYQs & Answers — Page 9

Questions 81–90 of 252. Imported answers require independent review unless marked reviewed.

Topic practice 252 questionsPage 9 of 26

A fluid is flowing steadily under laminar conditions over a thin rectangular plate at temperature

as shown in the figure below. The velocity and temperature of the free stream are

and

, respectively. When the fluid flow is only in the

-direction,

is the local heat transfer coefficient. Similarly, when the fluid flow is only in the

-direction,

is the corresponding local heat transfer coefficient. Use the correlation

for the local heat transfer coefficient, where, Nu, Re and Pr are the appropriate Nusselt, Reynolds and Prandtl numbers. The average heat transfer coefficients are defined as

and

. If

m and

m, the value of the ratio of

is ______ (in integer).

Diagram for Chemical Engineering question 54

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A perfectly insulated, concentric tube countercurrent heat exchanger is used to cool lubricating oil using water as a coolant (see figure below). Oil enters the outer annulus at a mass flow rate of 2 kg·s

with a temperature of 100 °C and leaves at 40 °C. Water enters the inner tube at a mass flow rate of 1 kg·s

with a temperature of 20 °C and leaves at 80 °C. Use specific heats of oil and water as 2089 J·kg

·K

and 4178 J·kg

·K

, respectively. There is no phase change in both the streams. Under steady-state conditions, the number of transfer units (NTU) is ______ (in integer).

Diagram for Chemical Engineering question 55

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Partially saturated air at 1 bar and 50 °C is contacted with water in an adiabatic saturator. The air is cooled and humidified to saturation, and exits at 25 °C with an absolute humidity of 0.02 kg water per kg dry air. Use latent heat of vaporization of water as 2450 kJ·kg

, and average specific heat capacity for dry air and water, respectively as 1.0 kJ·kg

·K

and 4.18 kJ·kg

·K

. If the absolute humidity of air entering the adiabatic saturator is

kg water per kg dry air, the value of

is __________ (rounded off to two decimal places).

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Distillation of a non-reactive binary mixture with components

and

is carried out in a batch still as shown in the figure below. The initial charge of the mixture in the still is 1 kmol. The initial and final amounts of

in the still are 0.1 kmol and 0.01 kmol, respectively. Use a constant relative volatility of 4.5. The mole fraction of

remaining in the vessel is ______ (rounded off to three decimal places).

Diagram for Chemical Engineering question 57

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Fresh catalyst is loaded into a reactor before the start of the following catalytic reaction:

The catalyst gets deactivated over time. The instantaneous activity

, at time

, is defined as the ratio of the rate of the reaction

(mol·(g cat)

·hr

) to the rate of reaction with fresh catalyst. Controlled experimental measurements led to an empirical correlation

where

is in hours. The activity of the catalyst at

hr is ______ (rounded off to one decimal place).

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A unimolecular, irreversible liquid-phase reaction

was carried out in an ideal batch reactor at temperature

. The rate of the reaction (

) measured at different conversions

is given in the table below. This reaction is also carried out in an ideal continuous stirred tank reactor (CSTR) at the same temperature

with a feed concentration of 1 mol m

, under steady-state conditions. For a conversion of 0.8, the space time (in s) of the CSTR is ______ (in integer).

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An irreversible liquid-phase second-order reaction

with rate constant

liter·mol

·min

, is carried out in an isothermal non-ideal reactor. A tracer experiment conducted on this reactor resulted in a residence time distribution (

-curve) as shown in the figure below. The areas of the rectangles (i), (ii) and (iii) are equal. Pure

at a concentration of 1.5 mol·liter

is fed to the reactor. The segregated model mimics the nonideality of the reactor. The percentage conversion of

at the exit of the reactor is _____ (rounded off to the nearest integer).

Diagram for Chemical Engineering question 60

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The outlet concentration

of a plug flow reactor (PFR) is controlled by manipulating the inlet concentration

. The following transfer function describes the dynamics of this PFR.

In the above equation,

min

and

min

. The measurement and valve transfer functions are both equal to 1. The ultimate gain, defined as the proportional controller gain that produces sustained oscillations, for this system is _____ (rounded off to one decimal place).

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The transfer function of a measuring instrument is

At time

, a step change of +1 unit is introduced in the input of this instrument. The time taken by the instrument to show an increase of 1 unit in its output is _____ (rounded off to two decimal places).

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A design engineer needs to purchase a membrane module (M) for a plant. Details about the two available options, M1 and M2, are given in the table below. The overall plant has an expected life of 7 years. If the interest rate is 8% per annum, compounded annually, the difference in the net present value (NPV) of these two options, in lakhs of rupees, is _____ (rounded off to one decimal place).

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GATE CH format:nat PYQs

Question 54

Question 55

Question 56

Question 57

Question 58

Question 59

Question 60

Question 61

Question 62

Question 63