In which type of refrigeration system is the cooling effect achieved through the absorption process?

The correct choice is absorption systems, as they utilize an absorption process to achieve the cooling effect. In an absorption refrigeration system, a refrigerant is absorbed by a secondary fluid, typically a solution of water and ammonia or lithium bromide. This process involves converting thermal energy into mechanical energy, allowing the system to create a cooling effect without the use of a compressor like in vapor-compression systems.

Absorption systems are particularly advantageous in applications where waste heat or natural gas can be utilized, as they often operate at lower energy consumption compared to traditional vapor-compression systems. They also have unique features suited for specific applications, such as those requiring quieter operation or those utilizing waste heat.

In contrast, vapor-compression systems rely on the mechanical compression of refrigerant gases. Thermoelectric systems use the Peltier effect to create a cooling effect but are generally less efficient for larger applications. Direct expansion systems are similar to vapor-compression systems but are specifically designed for cooling individual spaces or units. Each of these alternative systems operates on different principles, making absorption systems uniquely capable of utilizing thermal energy for cooling.