For condensers operating under similar duty and conditions, how does the overall heat-transfer coefficient of a horizontal condenser typically compare with that of a vertical condenser?

Introduction / Context:
Condensation heat transfer is influenced by orientation, because condensate film thickness and drainage path lengths differ between horizontal and vertical configurations. In shell-and-tube equipment, many services favor orientations that minimize film resistance on the condensing side to maximize the overall heat-transfer coefficient, U.

Given Data / Assumptions:

• Filmwise condensation of a pure vapor on clean surfaces.
• Comparable tube geometry and surface condition.
• Similar coolant conditions and fouling factors.

Concept / Approach:
For horizontal tubes (or tube banks), condensate drains off each tube by gravity, limiting film thickness and associated thermal resistance. In vertical condensers, condensate film must travel a longer path length, leading to a thicker average film and lower local heat-transfer coefficients. Empirical practice often observes substantially higher U for horizontal arrangements under otherwise similar conditions.

Step-by-Step Solution:

Verification / Alternative check:
Classical condensation correlations and design heuristics support the trend that horizontal tube banks outperform vertical film condensers for the same vapor load, particularly for laminar film regimes.

Why Other Options Are Wrong:

• “Same” or “less” contradict the film-thickness argument.
• “About 0.33 times” reverses the observed tendency.

Common Pitfalls:
Ignoring the impact of non-condensables and flooding limits, which can offset orientation benefits in specific services.

Final Answer:
About 3 times