In conventional desiccant and evaporative air-conditioning 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. A new system concept based on a sorptive cooled heat exchanger for the utilisation in air-conditioning processes, 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 design of the process results in a 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 stream, is always kept in over saturated 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 theoretical study aiming to the process potential assessment has been worked out. An accurate mathematical modelling activity of the physical processes through the component has been carried out. In particular the heat and mass transfer processes have been modelled in order to study the optimum configuration and system’s design parameters. The performance of the sorptive cooled heat exchanger for typical air-conditioning applications has been investigated. Experimental work has been carried on a pilot laboratory system. Different experiments, on the continuous indirect evaporative cooling process alone and on the cooled sorptive process have been worked out. The data collected during the experiments have been used to validate the numerical analysis results. The results of the sorptive cooled process analysis are presented in this paper. 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.
An original heat driven air-conditioning concept: advanced desiccant and evaporative cooling cycle numerical analysis
MOTTA, MARIO;
2004-01-01
Abstract
In conventional desiccant and evaporative air-conditioning 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. A new system concept based on a sorptive cooled heat exchanger for the utilisation in air-conditioning processes, 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 design of the process results in a 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 stream, is always kept in over saturated 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 theoretical study aiming to the process potential assessment has been worked out. An accurate mathematical modelling activity of the physical processes through the component has been carried out. In particular the heat and mass transfer processes have been modelled in order to study the optimum configuration and system’s design parameters. The performance of the sorptive cooled heat exchanger for typical air-conditioning applications has been investigated. Experimental work has been carried on a pilot laboratory system. Different experiments, on the continuous indirect evaporative cooling process alone and on the cooled sorptive process have been worked out. The data collected during the experiments have been used to validate the numerical analysis results. The results of the sorptive cooled process analysis are presented in this paper. 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
