Chemical Engineering Principles and Applications
The Chemical Engineering Principles and Applications domain tests whether you can integrate material and energy balances, thermodynamics, transport phenomena, reaction engineering, and unit-operation design into one consistent solution. Expect items that give a process description and ask for a stream flow, duty, equipment size, or operating condition, not isolated formula recall.
Balances and reference states
Set a system boundary and write total and component balances; at steady state accumulation is zero. For reacting systems use extent of reaction ξ or fractional conversion X_A. Choose one enthalpy reference state for every stream and report heats of reaction at that state. Sensible heat is ΔH = m∫Cp dT; latent and solution heats must be included when phases or mixtures change.
Transport and unit operations
For pipes, Re = ρvD/μ; obtain f from the Moody chart or Colebrook equation, and add pump head in Bernoulli. For heat exchangers, Q = UAΔT_lm using the countercurrent LMTD and an F correction for multipass shell-and-tube units. For distillation, use relative volatility α and operating lines; for absorption, NTU/HTU or Kremser methods.
Reactors
For constant-density liquid and first-order kinetics: CSTR: V = F_A0 X/(-r_A) = v0 X/[k(1-X)] PFR: V = F_A0 ∫0^X dX/(-r_A) = -(v0/k) ln(1-X)
Worked example. A first-order liquid reaction A→B has k = 0.05 s^-1, C_A0 = 2 mol/L, and F_A0 = 10 mol/s. Find the CSTR volume for 80% conversion. v0 = F_A0/C_A0 = 10/2000 = 0.005 m3/s. At X = 0.8, C_A = C_A0(1-X) = 0.4 mol/L = 400 mol/m3, so -r_A = kC_A = 20 mol/(m3·s). V = F_A0X/(-r_A) = (10)(0.8)/20 = 0.40 m3. A PFR would need -(0.005/0.05)ln(0.2) = 0.161 m3, so the CSTR is larger because it operates at the low outlet concentration.
Traps
- Mixing molar and mass flow, or mol/L with m3.
- Using X in the rate law instead of C_A = C_A0(1-X).
- Omitting the LMTD correction factor F or using the wrong ΔT.
- Forgetting enthalpy reference states and heat of mixing.
- Assuming ideal behavior for nonideal VLE.