Absorptiijäähdytys

Absorptiijäähdytys, also known as absorption refrigeration, is a process that uses a heat source to generate cooling. Unlike conventional vapor-compression refrigeration systems that rely on mechanical compression, absorption systems utilize a thermal compression cycle. The core of the system involves a working fluid and a refrigerant that are mixed and then separated through a series of thermodynamic processes.

The most common absorption refrigeration cycle uses ammonia as the refrigerant and water as the absorbent. Heat is applied to a generator, which boils the ammonia out of the water solution. The gaseous ammonia then travels to a condenser, where it is cooled and liquefied. This liquid ammonia evaporates in an evaporator, absorbing heat from the space to be cooled, thus producing the chilling effect. The ammonia vapor then returns to the absorber, where it is reabsorbed into the water solution, completing the cycle.

Another common type of absorption system uses lithium bromide as the absorbent and water as the refrigerant. This system is often employed for air conditioning applications, as water is non-toxic and readily available. In this setup, the water is evaporated in the evaporator, and then absorbed by the lithium bromide solution. Heat is applied to a generator to separate the water from the lithium bromide.

Absorption refrigeration systems are particularly advantageous when waste heat is readily available, such as from industrial processes, solar thermal collectors, or combined heat and power (CHP) plants. This allows for energy savings by utilizing heat that would otherwise be discarded. They are also quieter and can be more environmentally friendly than vapor-compression systems due to the absence of mechanical compressors and the potential for using natural refrigerants. However, absorption systems typically have a lower coefficient of performance (COP) compared to vapor-compression systems, meaning they require more heat input for a given amount of cooling.