Understanding the Electrolux Refrigerator Cycle

The Electrolux refrigerator, also known as an absorption refrigerator, is a type of cooling system that uses heat as the energy source instead of a mechanical compressor. It relies on a cycle involving the absorption and evaporation of a refrigerant in different substances. The key substances involved in a typical Electrolux refrigerator are ammonia, water, and hydrogen.

Components and Their Roles

• Ammonia: This is the refrigerant. It absorbs heat when it evaporates, causing cooling.
• Water: This acts as the absorbent. It absorbs ammonia vapor in the absorber section.
• Hydrogen: This is an inert gas added to the evaporator. Its presence significantly lowers the partial pressure of ammonia in the evaporator, which allows ammonia to evaporate at a lower temperature and pressure, enhancing the cooling effect.

Working Principle Focus: Evaporation

In the Electrolux refrigerator cycle, the cooling effect happens in the evaporator section. Liquid ammonia flows into the evaporator, where it mixes with hydrogen gas. The presence of hydrogen lowers the partial pressure of ammonia. According to Dalton's law of partial pressures, the total pressure in the evaporator is the sum of the partial pressures of ammonia and hydrogen. By keeping the total system pressure relatively constant, the presence of hydrogen means the partial pressure of ammonia is low. A lower partial pressure allows the ammonia to evaporate readily at the low temperature present in the evaporator coil, absorbing heat from the refrigerator's interior.

So, the core process that creates the cooling effect in the evaporator of an Electrolux refrigerator is the evaporation of liquid ammonia. This evaporation happens within the presence of hydrogen gas, which facilitates the process by reducing the partial pressure of ammonia.

Analyzing the Options

• Option 1: "Ammonia is absorbed in water". Absorption of ammonia in water happens in the absorber section, not where cooling occurs. This is part of the cycle but not the primary cooling process described by evaporation.
• Option 2: "Ammonia is absorbed in hydrogen". Hydrogen is an inert gas and does not absorb ammonia in the way water does in the absorber. Hydrogen's role is to lower the partial pressure of ammonia in the evaporator to aid evaporation.
• Option 3: "Hydrogen is evaporated in ammonia". Hydrogen is an inert gas and does not undergo evaporation in this cycle; ammonia is the substance that evaporates.
• Option 4: "Ammonia is evaporated in hydrogen". This accurately describes the process in the evaporator section where liquid ammonia evaporates into ammonia vapor within the atmosphere of hydrogen gas, causing the cooling effect. The hydrogen gas provides a low partial pressure environment for the ammonia to evaporate effectively.

Therefore, the statement that correctly describes a key process in the cooling section of an Electrolux refrigerator is that ammonia is evaporated in hydrogen.