Multi-objective optimization of underfloor air distribution (UFAD) systems performance in a densely occupied environment: A combination of numerical simulation and Taguchi algorithm

Abstract

Underfloor air distribution (UFAD) systems are on the way of development owing to their substantial energy saving potential as well as their capability for establishing thermally comfortable environments. Comprehensive evaluating these systems necessitates considering multiple effective factors ranging in several levels, which significantly augments the number of test cases and can even make the conducting of research impossible. Proposing a methodology for combining CFD results and the Taguchi optimization algorithm using the multi-response signal to noise (MRSN) analysis, the present study addresses this issue. In order to investigate the performance of UFAD systems applied in a densely occupied classroom from three fundamental viewpoints of thermal comfort, indoor air quality (IAQ), and energy saving, this research employs a multi-objective optimization approach. The utilized algorithm concludes that setting the following conditions provides the optimal state: (i) The underfloor diffusers beside the seats of occupants, (ii) The return vent at the height of 1.5 m from the floor, (iii) ACH equal to 14, (iv) Supply air temperature equal to 18 °C, and (v) Vertical air distribution from the underfloor diffusers. The ultimate simulation outcomes demonstrate that, according to the PMV and mean age of air values equal to 0.24 and 147 s in occupied and breathing zones, respectively, the thermal comfort conditions and desirable IAQ are established. Furthermore, energy saving compared to conventional mixing ventilation systems is a significant amount of 13.2%. In addition, local thermal comfort in terms of the vertical temperature difference and local convective cooling (draft) is achieved.