Empirical analysis of indoor air quality enhancement potential in a liquid-desiccant assisted air conditioning system

The main purpose of this research was to empirically investigate the removal of volatile organic compounds (VOCs), airborne particles, and microorganism contaminants from air conditioned by a liquid-desiccant (LD) dehumidifier. The dehumidifier was used in an existing liquid-desiccant evaporative cooling-assisted 100% outdoor air system (LD-IDECOAS) using both direct and indirect evaporative coolers. The ventilation efficiency of the LD-IDECOAS was also measured via a tracer-gas test with carbon dioxide. The concentrations of two representative VOCs, toluene and formaldehyde, the number of particles with various sizes, and the colony-forming units of microorganisms such as bacteria and fungi in the process air were measured before and after liquid-desiccant dehumidification. Then, the measurement results were compared with those acquired by bypassing the liquid-desiccant unit in order to verify the impact of the liquid desiccant on air-contaminant removal. The experimental results showed that the removal efficiency of the LD unit was 36% for toluene, and 29.6% for formaldehyde. The particle-removal efficiencies measured as part of this research were 48.2%, 64.1%, and 84.9% for the particle sizes of 2.5-5 μm, 5-10 μm, and 10-25 μm, respectively. The bacteria-removal efficiency was 77.5% and 81.3% for the sampling process air of 200 and 500 L, respectively, while the fungi removal efficiency was 38.8% and 44.4% for 200 and 500 L of sampling process air, respectively. In addition, the LD-IDECOAS provided an air change rate approximately 3.1 times higher than that of the VAV system when both systems delivered the supply air to the test chamber at the same rate.