1. Absorption: Hydrogen gas, under low pressure, is absorbed by a strong solution of lithium bromide (LiBr). This absorption process releases heat, which is removed by a cooling water circuit.
2. Vaporization: The LiBr solution, now saturated with hydrogen, is pumped to a high-pressure area where it is heated. The heat causes the hydrogen to vaporize and separate from the LiBr solution.
3. Condensation: The high-pressure hydrogen vapor is then passed through a condenser, where it cools and condenses back into a liquid. This process releases heat, which is usually dissipated to the surrounding environment.
4. Expansion: The liquid hydrogen then passes through an expansion valve, where its pressure drops dramatically. This expansion causes the hydrogen to cool further.
5. Evaporation: The cold, low-pressure hydrogen is then passed through an evaporator. Here, it absorbs heat from the refrigerator's interior, causing it to evaporate again. This cooling effect is what chills the refrigerator's contents.
6. Back to Absorption: The evaporated hydrogen, now warmer and at low pressure, returns to the absorber, where it is absorbed by the LiBr solution, completing the cycle.
Key points:
* Low pressure: Hydrogen's low boiling point makes it ideal for use as a refrigerant. At low pressures, it readily evaporates, absorbing heat and providing a cooling effect.
* High pressure: The hydrogen's high pressure during condensation is crucial for releasing heat to the environment and completing the cycle.
* Efficiency: The absorption refrigerator's efficiency stems from the fact that the hydrogen's phase changes (absorption, vaporization, condensation, and evaporation) are driven by heat rather than mechanical compression, making it a more environmentally friendly alternative to traditional refrigeration systems.
Overall, hydrogen's unique properties in absorption refrigerators allow for efficient cooling without the use of harmful refrigerants like CFCs or HCFCs.
