Chemical reaction engineering — space velocity (SV) in flow reactors: Identify the incorrect statement about the definition and interpretation of space velocity.

Introduction / Context:
Space velocity (SV) is a key sizing and performance metric for flow reactors in chemical reaction engineering. It normalizes the volumetric feed rate by the reactor volume and therefore indicates how many reactor volumes of feed pass through per unit time.

Given Data / Assumptions:

• SV is defined at specified temperature and pressure of the feed.
• Liquid Hourly Space Velocity (LHSV) and Gas Hourly Space Velocity (GHSV) are common forms.
• Reactor is assumed to be of constant holdup at the stated conditions.

Concept / Approach:
By definition, SV = volumetric feed rate / reactor volume. Hence its SI sense is time^(-1). An SV of 3 hr^(-1) literally means that, each hour, a volume of feed equal to three times the reactor volume is processed under the stated conditions.

Step-by-Step Solution:
Write SV = Q / V_R.If SV = 3 hr^(-1), then Q = 3 * V_R per hour.Therefore, the interpretation as one third reactor volume per hour is incorrect.

Verification / Alternative check:
Residence time τ for a well mixed system is τ = V_R / Q. Therefore τ = 1 / SV. If SV = 3 hr^(-1), then τ = 1/3 hr, which confirms the above interpretation.

Why Other Options Are Wrong:
Time^(-1) is the correct unit, and three reactor volumes per hour is the correct reading for SV = 3 hr^(-1). Hence only the one third statement is wrong.

Common Pitfalls:
Confusing SV with 1/SV. Mixing feed conditions with reactor conditions can also mislead when compressibility is significant.

Final Answer:
SV = 3 hr^(-1) means one third of a reactor volume of feed is fed each hour.