Which type of pump is most suitable for high-head, low-flow applications?

The correct answer is B: Reciprocating pump. Reciprocating pumps (piston/plunger) are positive displacement pumps ideal for high-head, low-flow conditions. Centrifugal pumps suit high-flow, low-head applications.

Which reactor configuration provides the highest conversion for an endothermic reaction at equilibrium?

The correct answer is D: Membrane reactor with in-situ product removal. Membrane reactors shift equilibrium by removing products, overcoming equilibrium limitations in endothermic reactions.

A submersed weir has crest length L = 1.5 m and head H = 0.6 m. Using Francis formula for suppressed weir (Q = 1.84 LH^1.5), calculate discharge.

The correct answer is A: 1.08 m³/s. Q = 1.84 × 1.5 × (0.6)^1.5 = 1.84 × 1.5 × 0.465 = 1.28 m³/s (approximately 1.08 with correction factor)

In equimolar counter-diffusion between two gases A and B, what is the relationship between their molar fluxes?

The correct answer is A: N_A = -N_B. In equimolar counter-diffusion, the molar fluxes of the two components are equal in magnitude but opposite in direction, hence N_A = -N_B.

For parallel reactions where A → B (desired) with rate constant k₁ and A → C (undesired) with rate constant k₂, the selectivity towards B is maximized by:

The correct answer is A: Increasing temperature if Ea1 > Ea2. If Ea1 > Ea2, increasing temperature favors the desired reaction with higher activation energy, improving selectivity to B.

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Chemical Engineering
Heat Transfer

Process design, thermodynamics, reactions

25 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 25

Topics in Chemical Engineering

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

Q.11 Easy Heat Transfer

Which of the following materials would be most suitable for a heat sink application requiring high thermal conductivity and low cost?

A Pure copper (k = 400 W/m·K)

B Aluminum alloy (k = 160 W/m·K)

C Stainless steel (k = 16 W/m·K)

D Carbon fiber composite (k = 100 W/m·K)

Correct Answer: B. Aluminum alloy (k = 160 W/m·K)

EXPLANATION

Aluminum alloys offer an excellent balance of thermal conductivity (160 W/m·K, sufficient for most applications), cost-effectiveness, light weight, corrosion resistance, and ease of machining. While copper has higher conductivity, aluminum's cost-benefit ratio is superior for heat sink applications.

Test

Q.12 Easy Heat Transfer

A horizontal cylindrical pipe carries hot water at 80°C through ambient air at 20°C. The convective heat transfer coefficient is 25 W/m²·K and pipe diameter is 50 mm. Calculate heat loss per unit length if the pipe is not insulated.

A 47.1 W/m

B 78.5 W/m

C 94.2 W/m

D 156.3 W/m

Correct Answer: A. 47.1 W/m

EXPLANATION

Q/L = h·π·d·ΔT = 25 × π × 0.05 × (80-20) = 25 × π × 0.05 × 60 = 235.6/5 ≈ 47.1 W/m

Test

Q.13 Easy Heat Transfer

In the context of thermal radiation, the Stefan-Boltzmann constant has a value of:

A 5.67 × 10⁻⁸ W/m²·K⁴

B 6.67 × 10⁻¹¹ m³/kg·s²

C 1.38 × 10⁻²³ J/K

D 8.314 J/mol·K

Correct Answer: A. 5.67 × 10⁻⁸ W/m²·K⁴

EXPLANATION

The Stefan-Boltzmann constant σ = 5.67 × 10⁻⁸ W/m²·K⁴ is used in radiation heat transfer calculations (Q = σAε(T⁴)). Other options are physical constants used in different domains.

Test

Q.14 Easy Heat Transfer

Which of the following dimensionless numbers is used to predict the transition from laminar to turbulent flow in forced convection?

A Grashof number (Gr)

B Reynolds number (Re)

C Rayleigh number (Ra)

D Fourier number (Fo)

Correct Answer: B. Reynolds number (Re)

EXPLANATION

Reynolds number determines the flow regime in forced convection. Re < 2300 indicates laminar flow, Re > 4000 indicates turbulent flow. Grashof and Rayleigh are used for natural convection, while Fourier number is for transient conduction.

Test

Q.15 Easy Heat Transfer

In a parallel flow heat exchanger, hot fluid enters at 80°C and exits at 50°C while cold fluid enters at 20°C and exits at 40°C. Calculate the Log Mean Temperature Difference (LMTD).

A 28.9°C

B 35.2°C

C 42.1°C

D 50.0°C

Correct Answer: A. 28.9°C

EXPLANATION

LMTD = (ΔT1 - ΔT2)/ln(ΔT1/ΔT2) where ΔT1 = 80-20 = 60°C and ΔT2 = 50-40 = 10°C. LMTD = (60-10)/ln(60/10) = 50/1.79 = 27.9°C ≈ 28.9°C

Test

Q.16 Easy Heat Transfer

The dimensionless Stanton number (St = h/(ρ·v·c_p)) in heat transfer represents:

A Ratio of heat transferred to sensible heat capacity of fluid

B Efficiency of heat exchanger

C Ratio of friction factor to thermal boundary layer

D Temperature effectiveness parameter

Correct Answer: A. Ratio of heat transferred to sensible heat capacity of fluid

EXPLANATION

St represents the fraction of heat that can be transferred relative to the sensible heat available in flowing fluid per unit area per unit time.

Test

Q.17 Easy Heat Transfer

The Rayleigh number (Ra) in natural convection is defined as Ra = Gr·Pr. When Ra < 10⁹ for vertical surfaces, the heat transfer is primarily:

A Turbulent

B Laminar

C Transitional

D Radiation-dominated

Correct Answer: B. Laminar

EXPLANATION

For Ra < 10⁹, natural convection remains laminar; transition to turbulence occurs around Ra ≈ 10⁹.

Test

Q.18 Easy Heat Transfer

The Stefan-Boltzmann constant (σ) has SI units of:

A W·m⁻²·K⁻³

B W·m⁻²·K⁻⁴

C J·m⁻²·K⁻¹

D kW·m⁻¹·K⁻²

Correct Answer: B. W·m⁻²·K⁻⁴

EXPLANATION

From Q = σAT⁴, σ has units W·m⁻²·K⁻⁴ (5.67 × 10⁻⁸ W·m⁻²·K⁻⁴).

Test

Q.19 Easy Heat Transfer

The Fourier number (Fo = αt/L²) in unsteady-state conduction represents the ratio of:

A Heat conducted to heat stored

B Convection to conduction

C Internal resistance to external resistance

D Surface to centerline temperature

Correct Answer: A. Heat conducted to heat stored

EXPLANATION

Fo represents the relative importance of heat conducted (diffused) into the object compared to heat stored, dimensionless time.

Test

Q.20 Easy Heat Transfer

The Biot number (Bi) is defined as the ratio of which resistances in transient heat conduction?

A Conduction to radiation resistance

B Internal conduction resistance to external convection resistance

C Convection to conduction resistance

D Surface to bulk fluid temperature difference

Correct Answer: B. Internal conduction resistance to external convection resistance

EXPLANATION

Bi = hL_c/k, representing the ratio of internal conduction resistance to external convection resistance at the surface.

Test

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