2020 · Paper 1

Complete GATE CH 2020 Paper 1 overview, original pages and practice · Timed previous-paper practice

Questions 55–57 of 65. Imported answers require review unless explicitly marked reviewed.

Question 45

Open question

CHNAT2 marksNeeds review

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



K



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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Question 46

Open question

CHNAT2 marksNeeds review

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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Question 47

Open question

CHNAT2 marksNeeds review

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



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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