Working principle of fridges

The refrigeration principle of freezers (e.g. refrigerators, freezers, etc.) is based on the "vapor compression refrigeration cycle", the core of which is the transfer of heat through the phase change (liquid to gaseous conversion) of the refrigerant in a closed system.

The main component of a freezer refrigeration system

1. Compressors

2. Condenser

3. Expansion valve

4. Evaporator

5. Refrigerants (e.g. R290a, R600a, etc.)

Detailed steps of the refrigeration cycle

1. Compression process (high temperature and high pressure gas) .

The compressor sucks in the gaseous refrigerant at low temperature and low pressure, and compresses it into a gas with high temperature and high pressure. At this point, the temperature of the refrigerant is much higher than the ambient temperature.

2. Condensation and heat dissipation (high-pressure liquid) .

The high-temperature and high-pressure gaseous refrigerant enters the condenser (usually a metal coil or heat sink), where it is gradually cooled and liquefied into a high-pressure liquid through heat exchange (heat dissipation) with the outside air. During condensation, the refrigerant releases heat into the environment, so heat is generated around the condenser.

3. Throttling and depressurizing (low-temperature and low-pressure liquids)

When the high-pressure liquid refrigerant passes through the expansion valve, the pressure drops sharply due to the throttling effect of the narrow channel, and it becomes a liquid-gaseous mixture at low temperature and low pressure.

4. Evaporative endothermy (low-temperature and low-pressure gases)

The low-temperature and low-pressure refrigerant enters the evaporator (located inside the freezer), absorbs the heat in the freezer, and rapidly evaporates into a gaseous state. The evaporation process can absorb a lot of heat, causing the temperature inside the freezer to drop.

5. Repeat the cycle

The gaseous refrigerant is sucked in by the compressor again, starting a new cycle.

Key Physics Principles

1. Phase change absorption/exothermy: liquid → gaseous (evaporative) endothermy, gaseous → liquid (condensing) exothermic.
2. Pressure control: The temperature range of endothermic and exothermic heat is controlled by adjusting the pressure through the compressor and expansion valve to change the boiling point of the refrigerant.

Additional Notes:

1. Refrigerant: It needs to have the characteristics of low boiling point, high latent heat, chemical stability, etc., and modern freezers mostly use environmentally friendly refrigerants (such as R600a).
2. Temperature control: The compressor is started and stopped through the temperature sensor and control system to maintain the set temperature.
3. Energy efficiency: The design of the condenser and evaporator (e.g., heat dissipation area, material) directly affects the refrigeration efficiency.

Safety Tips:

1. The refrigeration system is a closed cycle, and non-professionals should not disassemble it to avoid the risk of refrigerant leakage or electric shock.
2. If the freezer is not cooling, it may be due to refrigerant leakage, compressor failure or clogged pipeline, and professional repair is required.