Search

Impinging jet ventilation (IJV) system is believed to combines the advantages of good indoor air quality (IAQ) and high energy efficiency. However, there is few study about the optimization of multiple performance characteristics and the significance of design variables on the ventilation performance is not clear for IJV. This study addresses an approach based on Taguchi method with grey relational analysis for optimizing an IJV system with multiple performance characteristics (including draught discomfort (PD), temperature difference between the head and ankle level (Δ T), air change efficiency (ACE) and energy utilization coefficient (EUC)). The supply inlet height, supply velocity, supply temperature and return outlet height are selected as factors that affecting the ventilation performance of IJV and L 9 (43) orthogonal array is employed to design the experiments. First, the optimal combinations for PD, Δ T , ACE and EUC are determined separately by Taguchi method coupled with numerical simulations and the significance of the studied factors in promoting each evaluation index is revealed and ranked through main effect analysis and ANOVA. Second, the optimal combination of design variables corresponding to the best overall performance for IJV is determined by converting multi-objective into a single-objective according to Taguchi-based grey relational analysis. Then the important factors influencing the overall performance is ranked and the heights of supply inlet and return device are found to be significant factors in improving the overall performance. Finally, a confirmatory test is conducted to verify the improvement of performance characteristics and satisfactory results are obtained. • A multi-objective optimization study for impinging jet ventilation (IJV) is conducted. • Thermal comfort, indoor air quality and energy efficiency are considered together. • Significance of factors influencing the overall performance of IJV is revealed. • An optimal combination of design variables is obtained for the best performance. [ABSTRACT FROM AUTHOR]

For impinging jet ventilation (IJV) system, the energy efficiency is believed to be further improved by splitting the return vent from the exhaust device. However, how to properly set the return devices of IJV is unclear when it comes to a comprehensive consideration of the thermal comfort, indoor air quality (IAQ) and energy efficiency. In the present study, numerical simulations are performed to determine the thermal comfort indices (draught comfort (PD) and temperature gradient between the head and ankle levels (Δ T)), IAQ indices (air change efficiency (ACE) and contaminant removal efficiency (ε)) and energy efficiency index (η) for an IJV system with return outlet height (H) ranged from the ceiling to the floor level. The technique for order preferences by similarity to an ideal solution (TOPSIS) method is employed to determine the optimal return vent height by considering these performance evaluation indices simultaneously. The results indicate that when the H increases, the values of Δ T and η decrease, while the values of PD, ACE and ε increase. An optimal range of H (1.2–1.5 m above the floor) is recommended for the best overall performance of IJV. Moreover, a comprehensive graph of H is displayed in this paper, which could provide directions for optimizing the positions of exhaust and return devices. Image 1 • Impinging jet ventilation (IJV) with separate exhaust and return devices is studied. • Thermal comfort, indoor air quality and energy efficiency are considered together. • Short-circuit flow phenomenon of supply cold air might be occurred in the IJV. • An optimal return vent height (H) range for IJV is achieved by using TOPSIS method. [ABSTRACT FROM AUTHOR]