Evaluating and adapting low exergy systems with decentralized ventilation for tropical climates

The use of low exergy high temperature radiant cooling in the tropics is only possible with adequate dehumidification. We analyze the adaption of a decentralized ventilation system to supply dehumidified air using models and experimental prototypes. The decentralized air supply prototype was developed and initially tested at the ETH Zurich, then installed in a building laboratory that was shipped to Singapore-ETH Centre, and it was modeled and evaluated in collaboration with the National University of Singapore. We present the findings on its performance and ability to mitigate the risk of condensation for high performance radiant cooling surfaces for buildings in the tropics from models and experiments. We show that adequate dehumidification can be achieved in the decentralized supply unit by our expanded cooling coil. Our model shows that when the supply air has a humidity ratio of 13 g/kg then sufficient mitigation of condensation on the chilled panels is achieved. Experiments in the laboratory showed supply air down to 11 g/kg, which should be sufficient, but also showed the potentially large impact of infiltration of humid outdoor air in the tropics because humidity in the space remained higher than expected, and was also very sensitive to infiltration in our models.