Performance analysis of a novel desiccant and evaporative cooling cycle

In conventional desiccant and evaporative airconditioning systems employing solid sorptive material, indirect evaporative cooling of the supply air follows the sorptive process. The sequence of the two processes sets thermodynamic limits of the cycle and restricts the applicability of the cycle in severe conditions, i.e., conditions at high ambient air humidity. Here, a new system concept (named ECOS), based on a sorptive cooled heat exchanger, for air-conditioning applications, is presented. The novel system is the implementation of an original desiccant and evaporative cooling process. The system implementing the process is based on a counter-flow air-to-air heat exchanger technology. The heat exchanger is divided in sorptive and cooling channels, which are physically separated but in thermal contact. The sorptive material is fixed on the heat exchanger sorptive channels. The process is based on simultaneous sorptive dehumidification and indirect evaporative cooling of the supply air stream. The new system’s design results in a far higher dehumidification potential in comparison with conventional systems. Moreover in the cooling channels a continuous humidification of the cooling stream takes place. The latter, used for indirect evaporative cooling of the supply air stream, is always kept in close-tosaturated conditions during the process. Such a system has the potential to overcome the limits of standard systems and reach higher performances compared to conventional heat driven desiccant and evaporative systems. A parametric analysis aiming to the process potential assessment has been worked out. A simulation study based on the use of a simplified dynamical model describing the heat and mass transfer processes has been carried out. The analysis aimed to study the optimum system’s operation parameters. The performance of the sorptive cooled heat exchanger for typical air-conditioning applications has been investigated. In particular the new system offers the possibility to use low temperature heat such as heat from cogeneration systems for air conditioning, i.e. air treatment in an air handling unit for supply of cold, dry air during summer, without refrigeration even under climatic conditions with high humidity values of the ambient air (e.g., Mediterranean or tropic climate).