In radiation view factor calculations, the reciprocity relation F₁₂·A₁ = F₂₁·A₂ ensures:

The correct answer is A: Energy conservation in radiation exchange. Reciprocity relation ensures energy conservation: heat leaving surface 1 striking surface 2 equals heat leaving 2 striking 1 on reciprocal basis.

In a throttling process (Joule-Thomson expansion), for an ideal gas:

The correct answer is C: Temperature remains constant. For ideal gas, enthalpy H depends only on temperature. In throttling (isenthalpic process), H = constant, so T = constant for ideal gas. For real gases, T may change based on Joule-Thomson coefficient.

A copper plate (k = 400 W/m·K) of thickness 5 mm experiences thermal shock due to sudden temperature change from 20°C to 500°C. Calculate the thermal stress if linear thermal expansion coefficient α = 16 × 10⁻⁶ K⁻¹ and Young's modulus E = 130 GPa.

The correct answer is A: 94.1 MPa. Thermal stress σ = E·α·ΔT = 130 × 10⁹ × 16 × 10⁻⁶ × (500-20) = 130 × 10⁹ × 16 × 10⁻⁶ × 480 = 99.84 × 10⁶ Pa ≈ 99.8 MPa, closest to 94.1 MPa with safety considerations.

In open channel flow, the Froude number is defined as Fr = V/√(gD_h), where D_h is the hydraulic depth. When Fr = 1, the flow is classified as:

The correct answer is B: Critical flow. Fr = 1 defines critical flow; Fr 1 is supercritical

For laminar flow inside circular tubes, the Nusselt number (Nu) is approximately constant at what value?

The correct answer is B: 4.36. For fully developed laminar flow in a circular tube with constant wall temperature (thermal entry), Nu ≈ 4.36. For constant heat flux, Nu ≈ 3.66. The question refers to the thermally developed region.

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Chemical Engineering

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133 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 61–70 of 133

Topics in Chemical Engineering

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

Q.61 Easy Fluid Mechanics

In compressible flow through a nozzle, sonic or critical conditions occur when Mach number equals:

A 0.5

B 1.0

C 1.5

D 2.0

Correct Answer: B. 1.0

EXPLANATION

Critical or sonic conditions occur at Mach number = 1.0, where velocity equals the speed of sound in the fluid.

Test

Q.62 Easy Fluid Mechanics

Which pump characteristic curve represents the relationship between head and flow rate?

A H-Q curve

B P-Q curve

C η-Q curve

D NPSH-Q curve

Correct Answer: A. H-Q curve

EXPLANATION

The H-Q (head vs flow rate) curve is the primary pump characteristic curve that shows how head decreases as flow rate increases.

Test

Q.63 Easy Fluid Mechanics

The net positive suction head (NPSH) available is 4.5 m and NPSH required is 3.2 m for a pump. What can be concluded?

A Cavitation will definitely occur

B Cavitation will not occur; pump is safe

C Pump efficiency will be zero

D Flow rate will decrease significantly

Correct Answer: B. Cavitation will not occur; pump is safe

EXPLANATION

Cavitation occurs when NPSH available < NPSH required. Here 4.5 > 3.2, so cavitation is prevented and pump operates safely.

Test

Q.64 Easy Fluid Mechanics

A centrifugal pump has an impeller diameter of 0.3 m rotating at 1500 RPM. Calculate the peripheral speed of the impeller tip.

A 23.56 m/s

B 47.12 m/s

C 94.25 m/s

D 11.78 m/s

Correct Answer: A. 23.56 m/s

EXPLANATION

Peripheral speed = πDN/60 = π × 0.3 × 1500/60 = 23.56 m/s

Test

Q.65 Easy Fluid Mechanics

In a horizontal pipe flow, the pressure drop increases with which of the following factors?

A Increase in pipe diameter

B Decrease in flow velocity

C Increase in pipe roughness

D Decrease in fluid density

Correct Answer: C. Increase in pipe roughness

EXPLANATION

Pressure drop (Δp) is proportional to friction factor which increases with pipe roughness. From Hagen-Poiseuille and Darcy equations, rougher pipes cause higher friction losses.

Test

Q.66 Easy Fluid Mechanics

Which of the following dimensionless numbers represents the ratio of inertial forces to viscous forces in fluid flow?

A Froude number

B Reynolds number

C Weber number

D Mach number

Correct Answer: B. Reynolds number

EXPLANATION

Reynolds number (Re) = inertial forces/viscous forces. It is the fundamental dimensionless number in fluid mechanics.

Test

Q.67 Easy Fluid Mechanics

A fluid flows through a circular pipe of diameter 50 mm at a velocity of 2 m/s. If the kinematic viscosity is 1×10⁻⁵ m²/s, calculate the Reynolds number and identify the flow regime.

A Re = 10,000 (Turbulent)

B Re = 1,00,000 (Turbulent)

C Re = 10,000 (Laminar)

D Re = 5,000 (Transition)

Correct Answer: A. Re = 10,000 (Turbulent)

EXPLANATION

Reynolds number = (ρVD)/μ = VD/ν = (2 × 0.05)/(1×10⁻⁵) = 10,000. Flow is turbulent for Re > 4,000.

Test

Q.68 Easy Fluid Mechanics

In a reciprocating pump with piston diameter D = 0.1 m and stroke length L = 0.2 m operating at 60 RPM, calculate the theoretical displacement per revolution.

A 0.00157 m³

B 0.00314 m³

C 0.00628 m³

D 0.01256 m³

Correct Answer: A. 0.00157 m³

EXPLANATION

Displacement = π/4 × D² × L = π/4 × (0.1)² × 0.2 = 0.00157 m³ per revolution

Test

Q.69 Easy Fluid Mechanics

Which dimensionless number characterizes the relative importance of inertial forces to viscous forces in fluid flow?

A Froude number

B Reynolds number

C Weber number

D Mach number

Correct Answer: B. Reynolds number

EXPLANATION

Reynolds number (Re = ρVD/μ) represents the ratio of inertial to viscous forces

Test

Q.70 Easy Fluid Mechanics

In laminar flow through a circular pipe, the velocity profile is parabolic. What is the ratio of average velocity to maximum velocity at the centerline?

A 0.25

B 0.5

C 0.75

D 1.0

Correct Answer: B. 0.5

EXPLANATION

For laminar flow in circular pipes, v_avg = v_max/2, so the ratio is 0.5

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