Absorption refrigeration: In common absorption vapour systems, is R-12 the widely used refrigerant, or are other working pairs standard?

Introduction / Context:
Absorption refrigeration systems use heat to drive a refrigerant–absorbent pair, unlike vapour-compression systems that use mechanical work. It is essential to distinguish the typical working fluids of each technology.

Given Data / Assumptions:

• Absorption pairs commonly include ammonia–water and water–lithium bromide.
• R-12 is a CFC refrigerant historically used in vapour-compression (not absorption).
• Environmental regulations have phased out R-12 in most applications.

Concept / Approach:
In absorption cycles, refrigerant is absorbed in a liquid and later boiled out by an external heat input. The most common pairs are ammonia (refrigerant) with water (absorbent) for low-temperature applications, and water (refrigerant) with lithium bromide (absorbent) for air conditioning. R-12 lacks an absorbent pair standard in commercial absorption systems and is not the “widely used” refrigerant there.

Step-by-Step Solution:

Verification / Alternative check:
Manufacturer literature for absorption chillers consistently specifies LiBr–water for HVAC and NH3–water for refrigeration/ice plants, confirming the standard practice.

Why Other Options Are Wrong:

Conditional options about pressure, size, or machine type do not turn R-12 into a standard absorption refrigerant.

Common Pitfalls:
Confusing the fluid choices between absorption and compression cycles; the presence of a compressor vs an absorber–generator set dictates suitable working pairs.

Final Answer:

Incorrect