Air-cooled condenser design – Typical temperature difference Most air-cooled condensers are designed to operate with approximately what condensing-to-air temperature difference (approach)?

Introduction / Context:
The temperature difference between condensing refrigerant and leaving ambient air (often called the “TD” or approach) is a key sizing parameter for air-cooled condensers. It affects coil surface area, fan power, and system efficiency.

Given Data / Assumptions:

• Typical comfort-cooling or light industrial HVAC conditions.
• Reasonable ambient design temperatures and airflow rates.
• Standard finned-tube air-cooled condensers.

Concept / Approach:
Design practice often targets a temperature difference around 14 °C (about 25 °F). This balances coil cost and size against fan energy and compressor discharge pressure. Much lower TD requires oversized coils and fans; much higher TD raises condensing temperatures, hurting COP.

Step-by-Step Solution:
Define TD ≈ T_condensing − T_ambient (leaving air or outdoor ambient as specified).Adopt common design guidance: TD ≈ 14 °C for many packaged and split systems.Select the closest nominal value among choices: 14 °C.

Verification / Alternative check:
Manufacturers’ rating catalogs show nominal ARI/ASHRAE conditions that imply condenser approaches in the 10–15 °C range for many standard units, with 14 °C a widely cited rule-of-thumb.

Why Other Options Are Wrong:

• 5 °C or 8 °C imply very large coils/fans and higher first costs.
• 22 °C significantly elevates condensing temperature, reducing efficiency and compressor life under design conditions.
• 2 °C is impractically low for typical air-cooled designs.

Common Pitfalls:
Confusing “approach” with subcooling; comparing water-cooled versus air-cooled figures (water-cooled typically use much smaller approaches).

Final Answer:
14°C