Applications: Natural-convection air-cooled condensers are most commonly used in which of the following systems?

Introduction / Context:
Condensers reject heat from refrigeration systems. Air-cooled condensers may use either natural convection (no fan) or forced convection (with a fan). Selection depends on capacity and footprint.

Given Data / Assumptions:

• Small domestic refrigerators use wire-on-tube condensers on the back or bottom.
• Water coolers and room ACs typically employ forced convection fans.
• Natural convection capacity is limited due to low air-side heat transfer coefficients.

Concept / Approach:
Natural convection provides small heat rejection rates appropriate for low-capacity systems. Domestic refrigerators are designed around modest loads, making passive wire-and-tube condensers practical, quiet, and reliable.

Step-by-Step Solution:
Compare required heat rejection with natural convection capability.Domestic refrigerators → low Q_cond → feasible without fans.Water coolers/room ACs → higher Q_cond → require forced convection or water-cooled systems.

Verification / Alternative check:
Product tear-downs show finned coils with fans in room ACs, while household fridges often rely on passive condensers.

Why Other Options Are Wrong:

• Water coolers/room air conditioners: normally use fan-assisted condensers to meet higher heat loads.
• All of these/industrial chillers: overstate the capability of natural convection.

Common Pitfalls:
Confusing “air-cooled” with “natural convection.” Many air-cooled systems use fans (forced convection).

Final Answer:
Domestic refrigerators