Development and performance analysis of a novel multi-zone hybrid desiccant cooling system

Abstract

This study proposed a novel multi-zone applicable hybrid desiccant cooling system (MHDC) that uses condensing heat from the condenser to regenerate the solid desiccant and applied it as an outdoor air unit (OAU) with demand-controlled ventilation (DCV) in order to control the indoor humidity and air quality (IAQ). Indoor temperature and humidity control effect and system energy use were analysed compared to a conventional packaged terminal air-conditioning (PTAC) system with the heat recovery wheel (HRW) assisted OAU. The simulation result shows that in a typical high-rise building with high air tightness, The CO2 concentration in bedrooms can reach up to 3686 ppm when PTACs operate without fresh air. Without the dehumidification process, the introduction of fresh air will increase the relative humidity most of the occupancy time. The MHDC system adopted DCV can maintain IAQ except for a short period of cooking time and can handle the fresh air latent load while controlling indoor humidity without a separate regeneration heat source. However, due to the air volume limitation of OAU, the instantaneous dehumidification capacity of the MHDC system is not sufficient, resulting in a short time required to process the indoor humidity to 50 % level when the system initially started. Although the operation of the MHDC system increases the energy use of the OAU, the decrease in the latent load of zone level PTACs makes the total energy use is almost equal to the PTAC system with HRW assisted OAU, 606 kWh and 605 kWh respectively, while obtaining better indoor thermal comfort and IAQ. This study can prove that the proposed MHDC system is a possible alternative system to a conventional multi-zone air-conditioning system that can provide energy savings and thermal comfort.