Evaporative and Desiccant Cooling Techniques Feasibility When Applied to Air Conditioning

Doktorsavhandling, 2000

This thesis describes evaporative and desiccant cooling processes for air-conditioning purposes, i.e. for the removal of surplus heat from premises by the supply of cooled ventilation air. These cooling processes can replace the conventional method of cooling ventilation air involving the use of refrigerating machinery. An important difference between the use of evaporative and desiccant cooling and the use of refrigerating machinery is that no electrical energy is required and no refrigerant is needed to cool the ventilation air. Instead, water is consumed and, when using desiccant cooling, heat, which can be waste heat. However, in general less is known about evaporative and desiccant cooling, and there is less experience of their use, than for conventional systems using refrigerating machinery. The application of evaporative and desiccant cooling to comfort cooling changes the conditions and prerequisites relative to those when using refrigerating machinery. Although evaporative and desiccant cooling are based on essentially relatively uncomplicated technology, there are physical complications that must be understood and considered when designing such systems. This thesis therefore concentrates on describing and analysing the potentials and limitations of evaporative and desiccant cooling, with the aim of contributing to an understanding of the processes and illustrating ways of handling them. The work has therefore developed a methodology that can be used for demonstrating and analysing the potentials and limitations of the processes, involving appropriate design tools and performance models. The methodology is based on a concept to which the name of boundary lines has been given, indicating that this is a graphical method of illustrating the performance of evaporative and desiccant cooling systems in relation to given ambient and required conditions. The method has been used in this thesis to investigate different configurations of evaporative and desiccant cooling systems. The configurations are based on, or related to, a reference case, and illustrate by how much the ventilation air can be cooled as various parameters are altered. The effect of the variation of each parameter is analysed in parameter variation studies.