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Abstract: Growing demand for air conditioning in recent years has caused a significant increase in demand for primary energy resources. Solar-powered cooling is one of the environmentally-friendly techniques which may help alleviate the problem. A promising solar cooling method is through the use of a liquid desiccant system, where humidity is absorbed directly from the process air by direct contact with the desiccant. The desiccant is then regenerated, again in direct contact with an external air stream, by solar heat at relatively low temperatures. The liquid desiccant system has many potential advantages over other solar air conditioning systems and can provide a promising alternative to absorption or to solid desiccant systems. Earlier work by the authors included theoretical simulations and preliminary experiments on the key components of the liquid desiccant system. The objective of the present study has been to construct a prototype system based on the knowledge gained, to monitor its performance, identify problems and carry out preliminary design optimization. A 16kWt system was installed at the Energy Engineering Center at the Technion, in the Mediterranean city of Haifa. The system comprises a dehumidifier and a regenerator with their associated components operating together to dehumidify the fresh (ambient) air supply to a group of offices on the top floor of the building. LiCl-water is employed as the working fluid. The system is coupled to a solar collector field and employs two methods of storage – hot water and desiccant solution in the regenerated state. The performance of the system was monitored for five summer months under varying operating conditions. The paper describes the operation of the experimental system and presents the measured data and the calculated performance parameters. [Copyright &y& Elsevier]

The growing demand for air conditioning, particularly in hot and humid climates has caused a significant increase in demand for energy resources. A promising solar technology with potential to alleviate the problem is an open absorption system, where humidity is absorbed directly from the air to be treated by direct contact with the absorbent. The absorbent is then regenerated, again in direct contact with an external air stream, at relatively low temperatures of the heat source. The paper describes a study of a liquid desiccant cooling system designed to air-condition a group of offices on the top floor of a building in the Mediterranean city of Haifa, Israel. The system is capable of using as its source of power low-grade solar heat, of the type obtainable from low-cost flat plate collectors, and has a potential to provide both cooling and dehumidification in variable ratios, as required by the load. Several cycle variations have been considered, corresponding to different design options. A parametric study shows that entrance conditions of the ambient air significantly affect the heat and mass transfer occurring during the dehumidification process. The temperatures and flow rates of the heating and cooling water and the flow rates of solution through the dehumidifier and regenerator affect the humidity of the supply air delivered to the conditioned space, and show an optimum in certain cases. [ABSTRACT FROM AUTHOR]

In earlier work, a novel open absorption cycle was proposed, capable of producing both cooling and dehumidification for air conditioning, utilizing low-grade heat. The system, referred to as DER (Dehumidifier-Evaporator-Regenerator), uses ambient air in conjunction with an absorbent solution; the air is dehumidified and then employed to produce chilled water in an evaporative cooler. Alternatively, a portion of the dehumidified air may be used directly for air conditioning purposes. The system thus has the potential to provide both cooling and dehumidification in variable ratios, as required by the load. Computer simulations and theoretical investigations were carried out to analyze and predict the performance of the system. The objective of the present study has been to construct a laboratory system to test the concept, identify problems and carry out preliminary design optimization. The characteristic performance of individual components, analyzed theoretically in the simulation, was studied experimentally. Measurements have provided much-needed realistic data about heat and mass transfer coefficients. The performance of the system has been studied under varying operating conditions. The paper describes the operation of the experimental system and presents the measured data and the resulting transfer coefficients. [ABSTRACT FROM AUTHOR]