Absorption refrigeration pair identification — LiBr system In a lithium–bromide absorption refrigeration system used for air-conditioning, which working-pair role assignment is correct?

Introduction / Context:
Absorption refrigeration systems use a refrigerant–absorbent pair instead of a mechanical compressor to circulate refrigerant. Lithium–bromide systems are common in large HVAC applications.

Given Data / Assumptions:

• Application: air-conditioning (chilled water), not low-temperature freezing.
• LiBr–H2O pair operates under vacuum with water as the refrigerant.

Concept / Approach:
In LiBr systems, water evaporates in the evaporator (producing cooling) and is absorbed by a strong lithium–bromide solution in the absorber. The solution is then pumped to the generator where heat drives off the absorbed water vapour, which condenses and returns through the expansion device to the evaporator.

Step-by-Step Solution:

Verification / Alternative check:
Contrast with ammonia–water systems, where ammonia is the refrigerant and water is the absorbent; LiBr cannot practically absorb ammonia for HVAC use.

Why Other Options Are Wrong:
Reversing roles contradicts the operating principle; ammonia/CO2 pairs are not the LiBr air-conditioning system.

Common Pitfalls:
Assuming the higher-mass fraction component is the refrigerant; in absorption, the low-boiling constituent is the refrigerant regardless of mass fraction in solution.

Final Answer:

water is the refrigerant and lithium bromide is the absorbent