Applying a novel extra-low temperature dedicated outdoor air system for humidity control and energy efficiency

摘要

A novel dedicated outdoor air system consisting of a multi-stage direct expansion coil to generate extra-low temperature outdoor air to avoid moisture-related problems and for desirable air conditions and better energy efficiency is proposed for investigation. In this study, the proposed system's (extra-low temperature-dedicated outdoor air system) performance in achieving the desirable air conditions and better energy efficiency objectives is compared with a conventional direct expansion coil system with variable speed compressor and fan used for air conditioning of a typical office building in Hong Kong. Through hour-by-hour simulations, using equipment performance data of a pilot study and realistic building and system characteristics, it was found that the extra-low temperature-dedicated outdoor air system, as compared to the conventional system, could reduce the annual air-conditioning energy consumption by 22.6%, the indoor discomfort hours by 31% and the condensation risk to zero hours. Root-mean-square error and standard deviation analysis of the resultant relative humidity confirmed that the extra-low temperature-dedicated outdoor air system could better achieve the desired relative humidity. The findings of this study confirm that the extra-low temperature-dedicated outdoor air system is better than the conventional system in terms of both energy consumption and the desirable air conditions when used in office buildings in Hong Kong.