Working Substance in a Refrigerator: Freon (Dichlorodifluoromethane)

In a home refrigerator, the vapors of Freon, which is dichlorodifluoromethane (CCl2F2), act as the working substance. Let's understand why Freon is chosen as the working substance in refrigerators.

1. Working Substance:
The working substance in a refrigerator is the substance that undergoes a thermodynamic cycle and extracts heat from the cooling space (inside the refrigerator) and transfers it to the surroundings (outside the refrigerator). It is responsible for the cooling effect produced in the refrigerator.

2. Properties of Freon (CCl2F2):
Freon, also known as R-12 or dichlorodifluoromethane, is a chlorofluorocarbon (CFC) compound. It has several properties that make it suitable for use as a working substance in refrigerators:

- Low boiling point: Freon has a relatively low boiling point (-29.8 degrees Celsius or -21.6 degrees Fahrenheit), which allows it to easily evaporate and absorb heat from the surroundings.

- High latent heat of vaporization: Freon has a high latent heat of vaporization, which means it can absorb a significant amount of heat when it changes from a liquid to a vapor. This property allows it to extract heat from the cooling space efficiently.

- Non-toxic and non-flammable: Freon is non-toxic and non-flammable, making it safe for use in home refrigerators.

- Stable under normal conditions: Freon is stable under normal operating conditions, ensuring its reliability and longevity as a working substance.

3. Refrigeration Cycle:
The working substance (Freon) undergoes a thermodynamic cycle known as the refrigeration cycle in a refrigerator. The cycle consists of four main processes: compression, condensation, expansion, and evaporation.

- Compression: The compressor in the refrigerator compresses the vaporized Freon, increasing its pressure and temperature.

- Condensation: The high-pressure Freon then flows through the condenser coils, where it releases heat to the surroundings and condenses into a liquid state.

- Expansion: The condensed liquid Freon passes through an expansion valve, where its pressure decreases, causing it to expand and cool down.

- Evaporation: The low-pressure and low-temperature Freon now enters the evaporator coils located inside the refrigerator. As it evaporates, it absorbs heat from the cooling space, cooling the interior of the refrigerator.

4. Role of Freon as a Working Substance:
Freon acts as the working substance in a refrigerator by undergoing the refrigeration cycle, extracting heat from the cooling space, and transferring it to the surroundings. It absorbs heat from the interior of the refrigerator (sink) during evaporation and releases heat to the surroundings (source) during condensation.

By continuously circulating and undergoing phase changes, the Freon extracts heat from the refrigerator and maintains a cool temperature inside. This allows the refrigerator to store and preserve food items for longer periods.

In conclusion, the vapors of Freon (dichlorodifluoromethane) act as the working substance in a home refrigerator. Its properties, such as low boiling point, high latent heat of vaporization, non-toxicity,