Year

2014

Degree Name

Master of Engineering (Mechanical)

Department

Sustainable Buildings Research Centre

Abstract

Advanced liquid desiccant air-conditioning systems driven by solar energy may offer alternative answers for better indoor thermal comfort and enhanced energy efficiency in the built environment.

This thesis presents the development, modelling and simulation of an advanced solar-assisted liquid desiccant dehumidification air-conditioning system for energy efficiency and sustainability. The proposed system includes a counter-flow packed bed absorber, a counter-flow packed bed regenerator and a solar water heating system which consists of an array of flat plate solar collectors integrated with a thermal storage tank and an electric heater. It is designed to benefit from the low cost evaporative cooling technique in cooling the dehumidified processed air and the strong desiccant solution. Heat exchangers are used to improve the thermal performance of the system or prevent the direct contact between the liquid desiccant and water.

Various aspects such as proper system design, selection of appropriate types of dehumidifiers and liquid desiccants, and modelling of the different system components are addressed in this study. Lithium chloride solution is utilised as the working fluid owing to its excellent dehumidification performance and low regeneration energy requirements. A simplified approach has been developed to predict the size and the pressure drop of the absorber and regenerator at the design stage. A parametric study has been carried out to investigate the effects of various design and operational variables on the overall system performance, especially on the performance of the absorber and regenerator.

A thorough simulation platform for the proposed system has been developed using the Matlab Simulink integrating the models of the individual components developed and selected. The results revealed that enormous free solar energy for Sydney location could be used to reduce the electricity consumption in re-concentrating the liquid desiccant. The simulation results indicated that the proposed system has an average daily thermal coefficient of performance of 0.5-0.55. It was also shown that 73.4% of thermal energy required by the system for thermal regeneration was provided by the solar collectors while the rest was matched by the auxiliary electric heater. It is worthwhile to mention that, at the mid sunny days, the system is expected to consume less energy by the auxiliary heater when less cooling is required.

FoR codes (2008)

0913 MECHANICAL ENGINEERING

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.