In order to provide a comfortable living and working environment indoor in humid tropical countries, the outdoor air must be cooled and dehumidified before it is circulated into the rooms. The current technologies used for removing moisture from the air are either chiller or desiccants. In the air handling unit (AHU), the chiller cools the humid air to its saturation temperature and condenses the excessive moisture in the humid air. The moisture goes through the phase transition process. Using desiccant is a simple method for removing moisture. However the process to regenerate the desiccants is energy intensive and it has the risk of cross-contamination. Membrane technology for air dehumidification is based on the solution diffusion mechanism. The water molecules will be preferentially penetrating through the membranes due to its smaller kinetic diameter than the other counterparts. There is no phase transition involved neither the contacting between the fresh air stream and the polluted streams, hence it will require minimal energy consumption and it can avoid the cross-contamination problems.
A pilot scale air dehumidification system is built up with 9 pieces one-inch PAN/PDMS composite hollow fiber modules. PAN/PDMS composite hollow fiber was chosen due to its high gas permeability at low operation pressures. The hollow fiber spinning and coating technology, module design and system integration for membrane dehumidification were studied. A 150 hour long-term performance test shows that our membrane system has a stably good performance. In our test, the inlet fresh air has an average RH of 76.6±8.1% and temperature of 27.8±1.6¢ªC. After dehumidification, the dry air has an average RH of 47.3±6.5% and temperature of 31.8±2.3¢ªC. The calculation shows that using our membrane dehumidification together with air conditioning can save the energy up to 27% compared to conventional air conditioning process.