Electrolux (Platen–Munters) absorption refrigerator: Which combination of working fluids is used?

Introduction / Context:
The classic Electrolux (Platen–Munters) absorption refrigerator is a diffusion-absorption system widely used in off-grid or RV applications because it requires no mechanical compressor. Understanding the fluid trio clarifies how refrigeration is achieved without moving parts.

Given Data / Assumptions:

• Absorber and generator handle an ammonia–water solution.
• Hydrogen is used as an inert gas to reduce ammonia partial pressure in the evaporator.
• Heat input at the generator replaces the work input of a compressor.

Concept / Approach:
In the Electrolux system, ammonia (refrigerant) is absorbed in water (absorbent). Heating the strong solution in the generator liberates ammonia vapour, which is condensed and then expanded into the evaporator. Hydrogen circulates on the low-pressure side to lower the partial pressure of ammonia, enabling ammonia to evaporate at a low temperature and absorb heat (refrigeration effect).

Step-by-Step Solution:

Verification / Alternative check:
Mass and partial pressure balances show that the inert hydrogen permits evaporation at reduced ammonia partial pressure without a mechanical compressor.

Why Other Options Are Wrong:
Pairs like “water and hydrogen” or “ammonia and hydrogen” omit the necessary absorbent (water) or refrigerant; “ammonia and CO2” is unrelated to the Electrolux configuration.

Common Pitfalls:
Confusing the role of hydrogen (it is not condensed; it provides partial pressure control) and thinking water is the refrigerant (it is the absorbent).

Final Answer:
Ammonia, water, and hydrogen