Chemical Engineering - MCQ Practice Questions

In a recuperative heat exchanger, the effectiveness (ε) is defined as the ratio of actual heat transfer to:

The Peclet number (Pe = Re·Pr) in convective heat transfer indicates that:

The mean free path (λ) in gas kinetic theory at standard conditions is approximately 60 nm. This implies that at atmospheric pressure, heat conduction in gases is primarily through:

The convective heat transfer coefficient 'h' for natural convection from a vertical surface at constant temperature increases with height due to:

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

A steel rod (k = 50 W/m·K) of diameter 10 mm and length 100 mm is exposed to air at 25°C with h = 20 W/m²·K. The rod is maintained at 100°C at one end. Calculate the fin efficiency if m = √(hP/kA) = 8.37 m⁻¹.

Which heat exchanger type provides the maximum temperature effectiveness under the same flow conditions?

A surface at 300 K with emissivity 0.8 radiates heat to surroundings at 250 K. Calculate the net radiative heat transfer per m² (σ = 5.67 × 10⁻⁸ W/m²·K⁴).

In transient heat conduction, the Fourier number (Fo = α·t/L²) represents:

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'?

In a shell and tube heat exchanger, which configuration reduces the pressure drop while maintaining adequate heat transfer?

A spherical tank of diameter 1 m containing hot liquid at 90°C is placed in ambient air at 15°C. If h = 8 W/m²·K and k_insulation = 0.05 W/m·K with 50 mm insulation thickness, calculate the heat loss rate.

In a finned tube heat exchanger, the overall surface effectiveness is 0.75. This means:

A composite wall consists of three layers: Layer 1 (k₁ = 50 W/m·K, L₁ = 10 mm), Layer 2 (k₂ = 2 W/m·K, L₂ = 20 mm), Layer 3 (k₃ = 30 W/m·K, L₃ = 15 mm). The inner surface is at 100°C and outer at 25°C. Calculate thermal resistance per unit area.

In a double-pipe heat exchanger with counter-flow arrangement, the LMTD correction factor F = 0.95. What does this indicate?

A heat pipe is used to transfer heat from an electronic component at 80°C to ambient air at 25°C through evaporation and condensation. What is the primary advantage of a heat pipe over conventional conduction cooling?

A condenser operates with steam at 100°C condensing on a tube bank at 20°C. The saturation temperature drop is negligible. Which phase of condensation provides maximum heat transfer rate?

Which of the following methods is most suitable for measuring the convective heat transfer coefficient in real-time industrial applications?

In a cross-flow heat exchanger where both fluids are unmixed, the effectiveness (ε) is lower than in a counter-flow arrangement. What is the main reason for this?

The Grashof number (Gr) is used to characterize natural convection. For natural convection heat transfer, which of the following correctly describes the Grashof number?