Chemical Engineering: Fundamentals

In a steady-state process without chemical reaction, what is the fundamental material balance equation?

Input = Output. Since there is no accumulation or generation/consumption, the mass entering the system must equal the mass leaving the system.

State the Ideal Gas Law and define each variable including the universal gas constant.

PV = nRT, where P is pressure, V is volume, n is number of moles, R is the universal gas constant, and T is absolute temperature (Kelvin).

Define 'Conversion' in the context of a chemical reactor.

Conversion is the ratio of the moles of a reactant consumed by the reaction to the moles of that reactant fed into the reactor.

Which heat exchanger flow configuration is generally more thermally efficient: co-current or counter-current?

Counter-current flow is more efficient because it maintains a more uniform temperature driving force along the length of the exchanger.

What does the Reynolds Number (Re) represent physically in fluid mechanics?

The Reynolds Number is a dimensionless quantity representing the ratio of inertial forces to viscous forces within a fluid.

What is the primary difference between a Process Flow Diagram (PFD) and a Piping and Instrumentation Diagram (P&ID)?

A PFD shows the general flow of processes and major equipment, while a P&ID includes technical details like piping specifications, valves, and instrumentation/control loops.

Define the 'Recycle Ratio' in a process involving a recycle stream.

The Recycle Ratio is the ratio of the flow rate of the recycle stream to the flow rate of the fresh feed entering the process.

How is the enthalpy change (ΔH) calculated for a substance undergoing a temperature change from T1 to T2 without a phase change?

ΔH = ∫(Cp dT) from T1 to T2, where Cp is the constant-pressure heat capacity, which may be a function of temperature.

Contrast the residence time distribution (RTD) of an ideal CSTR and an ideal PFR.

An ideal CSTR has a wide distribution of residence times due to perfect mixing, while an ideal PFR has a single, uniform residence time for all fluid elements.

Write the formula for the Log Mean Temperature Difference (LMTD) used in heat exchanger design.

LMTD = (ΔT1 - ΔT2) / ln(ΔT1 / ΔT2), where ΔT1 and ΔT2 are the temperature differences between the hot and cold fluids at the two ends of the exchanger.