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.
ASJC Scopus subject areas
- Environmental Engineering
- Building and Construction
- Fluid Flow and Transfer Processes