A NOVEL INTEGRATED ENERGY-EFFICIENT DEDICATED OUTDOOR AIR SYSTEM (DOAS) WITH LIQUID DESICCANT

DOAS can largely improve the energy efficiency and indoor air quality (IAQ) of air-conditioning systems. Cooling coils and desiccant absorption have been adopted for dehumidification. Cooling-based dehumidification may be inefficient in many cases due to its inherent weaknesses in dehumidification. Although solid and liquid desiccant cooling has been investigated intensively, there is still a great potential for further improvement of desiccant cooling systems. A novel integrated air-conditioning system is proposed. It consists of DOAS with liquid desiccant, parallel cooling terminals, refrigeration system and heat pump. A direct evaporative cooler commonly used in the standard desiccant system is eliminated because it causes unnecessary exergy loss. A sensible heat exchanger and a membrane enthalpy exchanger are arranged in an effective way to maximally recover both sensible and latent cooling energy in the exhaust air. Mathematical models for the thermal simulation of individual components in the standard and new DOAS have been presented and integrated into a TRNSYS computer program. The computer program has been applied to an example building on a hot and humid day in Hong Kong. The simulation results indicate that the newly proposed system can recover the cooling energy 28.2 kJ/(kg air) while the standard system only 11.2 kJ/(kg air). Moreover, the former only uses 39.0 % of the total primary energy used in the latter.