Chemical Engineering - MCQ Practice Questions

The Peclet number (Pe = Re·Pr) is used to determine the relative importance of convection to conduction. For Pe << 1, which heat transfer mechanism is dominant?

In pipeline heat loss calculations for process industries, the critical radius of insulation is the thickness at which the outer surface area increase due to added insulation equals the reduction in heat transfer coefficient. For a pipe with outer radius r_o = 50 mm and insulation thermal conductivity k = 0.05 W/(m·K), what is the approximate critical radius?

In the 2024-2025 update to heat exchanger design standards (TEMA), which of the following represents the most significant advancement in fouling prediction for industrial heat exchangers?

What is the SI unit of thermal conductivity?

In a parallel flow heat exchanger, the temperature approach is minimum at which end?

The Biot number (Bi = hL_c/k) is used to determine which regime of unsteady-state heat conduction?

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

A shell-and-tube heat exchanger with one shell pass and two tube passes (1-2 STHE) has a correction factor F. What is the typical range of F values?

In convective heat transfer, which dimensionless number represents the ratio of buoyant to viscous forces?

A flat plate at 100°C is cooled by air at 25°C. The convection heat transfer coefficient is 50 W/(m²·K). Calculate heat flux if plate area is 2 m².

For radiation heat transfer between two surfaces, increasing the absolute temperature of the hot surface by 10% will increase radiative heat transfer by approximately what percentage?

A double-pipe heat exchanger (counterflow) is used to cool 5 kg/s of oil (Cp = 2.0 kJ/kg·K) from 80°C to 50°C using water at 20°C entering with a temperature rise of 15°C. What is the water flow rate required?

The overall heat transfer coefficient U in a composite system (series resistances) is determined by which method?

In pool boiling, the critical heat flux (CHF) occurs at which point on the boiling curve?

A 10 cm diameter steel pipe (k = 50 W/m·K) with inner diameter 9 cm carries hot water at 90°C. Outer surface is at 70°C. Calculate heat transfer rate per meter length.

The Prandtl number (Pr = Cp·μ/k) represents the ratio of which two transport properties?

In cross-flow heat exchangers (unmixed-unmixed configuration), the effectiveness is lower than parallel/counterflow because:

For turbulent flow over a flat plate, the local Nusselt number varies with distance x according to which relationship?

A condensing steam at 100°C releases latent heat to water inside tubes. This is an example of which type of phase-change heat transfer?

In a multipass heat exchanger design, increasing the number of shell passes from 1 to 2 will predominantly affect which parameter?