Sorption materials for the safe use of flammable refrigerants in cooling/heating cycles.

The F-Gas regulation and the resulting phasedown of fluorinated hydrocarbons (HFOs) as safe refrigerants (e.g R407C and R410A) effects an increase in research and development activities for alternative low GWP refrigerants. Besides new synthetic refrigerants, there is a focus on natural refrigerants like hydrocarbons, ammonia and carbon dioxide (Europaisches Parlament 2014). The relevant alternative refrigerants are characterized by a low GWP and good thermodynamic properties. However, they are dangerous to humans (e.g., through a high flammability) and nature by different degrees in case of leakage. Thus, the development of safety concepts has become of central importance in the R&D of heat pumps and chillers with a strong focus on indoor units. In this work, a safety element adsorbing the refrigerant in the event of an occuring leakage will be presented. The adsorption process is coupled to the refrigerant system in order to reduce the refrigerant release in huge amount. The main focus of this presentation is set on the evaluation and the choice of the adsorption material for the uptake of a flammable refrigerant. Therefore, the material characteristics of certain adsorptive materials were characterized with respect to the specific surface (BET surface), pore geometry and the adsorption equilibrium and enthalpy at different temperatures and pressures.