Question

A smaller HTU indicates:

• A. Poor mass transfer efficiency
• B. Higher column height required
• C. Less height needed per transfer unit
• D. Lower gas flow rates

Hint:

A smaller HTU value means the equipment is more efficient — you need a shorter column to achieve the desired separation.

Answer 1

The Correct Option is C

HTU stands for Height of a Transfer Unit, which is a key concept in mass transfer operations such as absorption, stripping, and distillation.
The total height of a packed column required for a certain separation is given by:
\[ H = N_{TU} \times HTU \]
Where:
$H$ = total column height
$N_{TU}$ = number of transfer units
$HTU$ = height of each transfer unit
A smaller HTU means each transfer unit achieves more mass transfer per unit height. Therefore, fewer total column height is needed to accomplish the same degree of separation.
Thus, a smaller HTU indicates better mass transfer efficiency and implies that less height is needed per transfer unit.
Analysis of options:
Option 1: Incorrect — smaller HTU suggests better, not poor, mass transfer.
Option 2: Incorrect — smaller HTU implies lower total height required.
Option 3: Correct — less height is required per transfer unit.
Option 4: Incorrect — HTU is more directly linked to mass transfer efficiency than flow rate.
Hence, the correct interpretation is: less height needed per transfer unit.