For a reciprocating pump with bore diameter 0.08 m, stroke length 0.15 m, and operating at 60 RPM with 90% volumetric efficiency, the discharge is approximately:

The correct answer is A: 0.0036 m³/s. Q = (π/4)D²L×N×η/60 = (π/4)×0.08²×0.15×60×0.90/60 = π×0.0064×0.15×0.90/4 ≈ 0.0036 m³/s

In a gas absorption process using a packed tower, if the interfacial area 'a' increases, how does it affect the mass transfer rate?

The correct answer is B: Mass transfer rate increases proportionally. Since mass transfer rate = k_G * a * ΔP, an increase in interfacial area directly increases the mass transfer rate (linear relationship).

In a constant volume process, the heat added to the system equals:

The correct answer is A: Change in internal energy (ΔU). For constant volume: W = 0, so Q = ΔU from first law (ΔU = Q - W). This is isochoric process where all heat goes to internal energy change.

For a binary gas mixture, the Stefan flow correction factor accounts for:

The correct answer is A: Net molar flow due to unequal molar diffusion rates. When one component condenses/reacts, equal molar counter-diffusion assumption breaks down. Stefan factor (B_m) corrects for net molar flow.

In laminar flow through a circular tube with constant wall temperature, the Nusselt number is constant at Nu ≈ 3.66. This means:

The correct answer is C: The entrance effects are negligible. Constant Nu in fully developed laminar flow indicates entrance effects are negligible and thermal profile is established.

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Chemical Engineering
Heat Transfer

Process design, thermodynamics, reactions

25 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–25 of 25

Topics in Chemical Engineering

All Mass Transfer 100 Heat Transfer 100 Fluid Mechanics 100 Chemical Reaction Engineering 100 Thermodynamics 97

Q.21 Easy Heat Transfer

The thermal diffusivity (α) has dimensions of which of the following?

A Length²/Time

B Length/Time²

C Energy/(Mass·Temperature)

D Energy/(Time·Length)

Correct Answer: A. Length²/Time

EXPLANATION

Thermal diffusivity α = k/(ρ·C_p) has dimensions L²/t, representing how fast thermal disturbances propagate through a material.

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Q.22 Easy Heat Transfer

Which of the following best describes the behavior of thermal conductivity with temperature for most metals?

A Increases with temperature

B Decreases with temperature

C Remains constant

D First increases then decreases

Correct Answer: B. Decreases with temperature

EXPLANATION

For most pure metals, thermal conductivity decreases with increasing temperature due to increased lattice vibrations causing phonon scattering.

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Q.23 Easy Heat Transfer

Which dimensionless number represents the ratio of buoyancy forces to viscous forces in natural convection?

A Grashof number (Gr)

B Rayleigh number (Ra)

C Nusselt number (Nu)

D Prandtl number (Pr)

Correct Answer: A. Grashof number (Gr)

EXPLANATION

Grashof number (Gr = gβΔT L³/ν²) represents the ratio of buoyancy to viscous forces. Ra = Gr × Pr combines both effects.

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Q.24 Easy Heat Transfer

In heat conduction through a composite wall, the overall heat transfer rate is determined by which principle?

A Ohm's law analogy

B Kirchhoff's law

C Fourier's law only

D Stefan-Boltzmann law

Correct Answer: A. Ohm's law analogy

EXPLANATION

The thermal resistance network (Ohm's law analogy) is used where total thermal resistance equals the sum of individual resistances in series for composite walls.

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Q.25 Easy Heat Transfer

Which of the following is the SI unit of thermal conductivity?

A W/(m·K)

B W/(m²·K)

C J/(s·m·K)

D cal/(s·cm·°C)

Correct Answer: A. W/(m·K)

EXPLANATION

Thermal conductivity is expressed as W/(m·K) in SI units, equivalent to J/(s·m·K). This represents heat flow rate per unit area per unit temperature gradient.

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