Desiccant thermally controlled dehumidification in HVAC systems: Energy and exergy analysis, evaluation of different materials

This work presents a comparison between a traditional air conditioning system that dehumidifies via a low-temperature cooling coil and a system that dehumidifies using a dedicated dehumidification section equipped with an exchanger coated with desiccant material. The dehumidification with desiccant has been supposed isothermal. The two systems are compared from both energy (cooling power required by the cooling coil, Coefficient of Performance and electrical consumption of the refrigeration device) and exergy (exergy efficiency of the system) perspectives. A parametric analysis is conducted, by varying the external temperature (30–38 °C) and external humidity (10–18 g/kg). Three load scenarios, differing in sensible/latent ratio (0.5, 1, 2), are considered. In the case of a sensible/latent ratio of 0.5, the system with the desiccant exhibits savings between 65 % and 85 %, depending on the inlet humidity ratio. In this scenario, a strong improvement is also obtained in the exergy efficiency. Then, three different materials are considered as desiccants: silica gel, zeolite and Metal-Organic Frameworks MIL-100 (Fe). They have been compared by analysing the isotherms of adsorptions. The findings underscore the potential of desiccant materials to enhance the energy and exergy efficiency of air conditioning systems, in particular if they are used in exchangers able to perform near-isothermal dehumidification. The obtained results propose the concept of near-isothermal dehumidification and Metal-Organic Frameworks as an effective solution for air conditioning systems, promoting energy efficiency and a consistent decarbonisation of this sector.