A liquid desiccant air conditioning system for buildings in hot and humid climates | |
| Author | Thosapon Katejanekarn |
| Call Number | AIT Diss. no.ET-08-02 |
| Subject(s) | Air conditioning Drying agents |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctoral of Engineering in Energy Technology, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ET-08-02 |
| Abstract | In tropical, hot and humid climates where temperature and humidity level are high, air conditioning (AC) systems are necessary for providing thermal comfort to the building occupants. For an air conditioned space that needs outside air ventilation to maintain the indoor air quality, the ventilation air can bring the sensible heat ratio (SHR) of the cooling load well below 0.7 since it accounts for as high as 80% of total latent load in the space. The cooling load SHR below this value cannot be handled effectively by conventional AC systems. Handling sensible and latent load separately using a hybrid scheme is an interesting option. A desiccant system can handle the latent load while a conventional system can handle mainly the sensible load. This could help reduce overall energy consumption and provide effective control of indoor air condition. A theoretical and experimental investigation of the use of a liquid desiccant AC system in a tropical, hot and humid climate has been carried out.. The lithium chloride liquid desiccant system treated the ventilation air before supplying it into the conditioned space. Solar energy was used for the regeneration process. Cooling water from a cooling tower was used to provide cooling for the entire system. Models were developed to evaluate the performance of the dehumidification and the regeneration side of the system. In this study, a simulation procedure incorporating the effects of both sides has been developed to evaluate the system performance, namely, delivered air condition, moisture removal rate at the dehumidifier, and evaporation rate at the regenerator. The simulation procedure used AIT's 2007 weather data and the results showed that the system can work for all seasons (i.e., hot, rainy, and cold season). The average temperature and humidity reduction was found to be 1.9°C and 0.0058 kgw/kgda equivalent to 15.0% relative humidity (RH) reduction. The average evaporated water at the regenerator was found to be greater than the moisture removed at the dehumidifier in every season. This is favorable since the overall concentration of the desiccant in the system will not decrease and the system performance will not drop. Experimental studies were also carried out at AIT covering all three seasons. On an average, temperature and humidity reduction was found to be 1.2°C and 0.0042 kgw/kgda equivalent to 11.1 %RH reduction. The average evaporated water was also found to be greater than the removed moisture in every season. Therefore, both simulation and experimental studies confirm that the liquid desiccant system developed in this study can operate in the actual hot and humid climate. However, the study also suggests some limitations of the system to be improved, such as, the temperature of cooling water from the cooling tower that cannot go below the ambient wet-bulb temperature and the capacity of the regeneration side of the system. The system was also experimented in hybrid operations with a chilled water fan coil unit (CHW FCU) system and a radiant cooling system during all three seasons. For the CHW FCU cases, the hybrid operation can save energy at the chilled water plant by around 13.5% while it can provide thermal comfort all the time. For the radiant cooling cases, the hybrid operation can improve thermal comfort level by around 0.5 to 1.0 on the ASHRAE's thermal sensation scale. |
| Year | 2008 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ET-08-02 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Energy Technology (ET) |
| Chairperson(s) | Kumar, S.; |
| Examination Committee(s) | Kato, Shinsuke ;Dutta, Animesh ;Nadarajah, Mithulananthan ;Perera, Ranjith ;Surapong Chirarattananon; |
| Scholarship Donor(s) | Ministry of Education, Thailand (CRN) ;Asian Institute of Technology (RTG); |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2008 |