Design and Working Principle

Design and Working Principle

Raising adsorption technology
to new levels through research.

For close to two decades, FAHRENHEIT, founded as a spin-off of the renowned Fraunhofer Institute, has been advancing the state of the art of adsorption technology.

Several patented innovations, such as the two-chamber principle and the thin sheet vacuum enclosure, cemented FAHRENHEIT’s status as the industry‚Äôs technology leader.

Thin sheet vacuum enclosure:
The “coffee bag” principle.

The two heat exchangers which make up an adsorption module are encased and vacuum sealed by a thin steel or aluminum enclosure.

The design principle is as simple as it is ingenuous: The enclosure forms a thin envelope which rests on the heat exchangers themselves, and does not require any additional support structure. The outside air pressure holds everything tightly together.

In essence, this design resembles a coffee bag. It is simple to manufacture, and the material savings result in less weight and, moreover, less thermal mass and therefore higher efficiency.




Dual-Chamber Technology: Durable design
without moving parts.

Our dual-chamber technology is a major step towards even more reliable and maintenance free cooling and heating solutions. Our chillers contain two (or more) identical adsorption modules. Each one contains a pair of heat exchangers, one acting as adsorber/desorber, and the other as evaporator/condenser.

The process chambers are interconnected through computer controlled 3-way-valves which ensure that heat and cold are always guided where it is needed in each process phase.

This setup does not require moving parts or valves within the adsorption modules and therefore ensures optimal reliability and an almost maintenance free system.

Cold is continuously generated by anticyclical operation of two identical modules.

Functional Design

Hot-Water Circuit

The hot-water circuit supplies the power to drive the adsorption chiller aggregate and the heat exchange that occurs inside of it.

Recooling Circuit

The heat that has been supplied to the adsorption chiller aggregates (heat removed from the object to be cooled, and heat to drive the adsorption cycle) is distributed to the environment via the recooler at mean temperature level.

Cold-Water Circuit

The cold-water circuit removes heat from the object to be cooled.

Our adsorption chillers operate in four phases:



The desorber is flooded with hot water from the hot-water circuit. As a result, the cooling agent, which has accumulated in the adsorbing material, is being expelled and liquefied on the condenser. The heat that is being generated during the liquefaction is being discharged through the recooler.

At the same time, the adsorber adsorbs the water vapor which is evaporated when the object to be cooled heats up the cold-water circuit. The heat that is being created during the adsorption process will be discharged, together with the liquefaction heat, to the environment. Phase 1 runs until the cold-water temperature set point has been reached.


Heat Reclamation

Right after phase 1, the 3-way-valves in the flow section of the three circuits are set such that adsorber 1, now desorbed, i.e. dried, will be flooded with recooling water. The energy which was initially was stored in the desorber will not yet be transported away to the mean temperature sink, but instead will be pumped into the driving circuit over a period of time.

The return circuit of adsorber 2, which is about to be desorbed following the adsorption process, will for some amount of time be connected to the recooling circuit. Only after a certain temperature difference between the two adsorber return circuits has been reached, phase 2 will terminate by switching the 3-way-valves in the return section of the three circuits.



The desorber is flooded with hot water (drive heat), and at the same time the adsorber is accumulating water vapor.

The process of adsorption and desorption happens analogously to phase 1.


Heat Reclamation

Following phase 3, the 3-way-valves are switched such that the previously desorbed adsorber 2 will now be flooded with recooling water.

The heat reclamation process happens analogously to phase 2.