The thermal entrance length for laminar flow in a pipe is given by x_th/D ≈ 0.05·Re·Pr. For water flowing in a 25 mm diameter pipe with Reynolds number of 1000 and Prandtl number of 7, what is the thermal entrance length?

The correct answer is A: 0.875 m. x_th = 0.05 × Re × Pr × D = 0.05 × 1000 × 7 × 0.025 = 8.75 m. This is the distance from the entrance where thermal development is completed (approximately 99% developed).

The mass transfer coefficient k_L in liquid phase absorption typically has units of:

The correct answer is A: m/s. The liquid phase mass transfer coefficient k_L has units of m/s or cm/s, representing the rate of mass transfer per unit concentration difference.

The chemical potential μᵢ of a component in a mixture relates to partial molar properties by:

The correct answer is D: All of the above. All statements define chemical potential from different perspectives. μᵢ is the partial molar Gibbs energy and equals (∂G/∂nᵢ)_{T,P,n_j}.

In boundary layer theory, the displacement thickness (δ*) represents which physical concept?

The correct answer is B: The distance by which the streamline is displaced due to the formation of boundary layer. Displacement thickness is the distance the external streamline is displaced due to the reduction in flow velocity within the boundary layer

For natural convection over a vertical flat plate, the Nusselt number correlation is typically given by Nu = C·Ra^n. What is the typical value of exponent 'n'?

The correct answer is B: 0.33. For laminar natural convection on vertical plates, Nu = 0.59·Ra⁰·²⁵ is used, while for turbulent natural convection (Ra > 10⁹), Nu = 0.1·Ra⁰·³³ is commonly used. The value 0.33 or 1/3 is standard for turbulent natural convection.

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Chemical Engineering
Fluid Mechanics

Process design, thermodynamics, reactions

52 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 51–52 of 52

Topics in Chemical Engineering

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

Q.51 Medium Fluid Mechanics

Water flows through a venturimeter with inlet diameter 0.1 m and throat diameter 0.05 m. The pressure difference is 5 kPa. Assuming ideal flow, calculate the velocity at the inlet (ρ = 1000 kg/m³).

A 1.44 m/s

B 2.88 m/s

C 4.32 m/s

D 5.76 m/s

Correct Answer: B. 2.88 m/s

EXPLANATION

Using continuity and Bernoulli: V₁ = √[2ΔP/(ρ(A₁²/A₂² - 1))]. With area ratio 4, V₁ = √[2×5000/(1000×15)] = 2.88 m/s.

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Q.52 Medium Fluid Mechanics

For turbulent flow in rough pipes at high Reynolds numbers, which friction factor equation is most applicable?

A Laminar equation: f = 64/Re

B Colebrook-White equation

C Blasius equation: f = 0.316/Re⁰·²⁵

D Swamee-Jain equation

Correct Answer: B. Colebrook-White equation

EXPLANATION

Colebrook-White equation is implicit but accurate for all turbulent regimes including rough pipes. For very rough pipes at high Re, relative roughness dominates.

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