Coordinate control of air movement for optimal thermal comfort

Abstract

Personally controlled air movement can maintain or enhance thermal comfort in warm environments and reduce energy consumption. Unlike controlling a personal fan, using a system of fans for multiple occupants is difficult as it is hard to find an appropriate fan speed setting that maximizes occupants' satisfaction. Since limited work has been carried out on this issue, in this paper, a novel cooperative control approach for a system of fans is proposed to provide optimized air movement for multiple occupants. This is the first time that a system of fans is controlled cooperatively in the research of built environment. The proposed approach predicts airflow in a cost-effective manner by calibrating the fans in the real environment. The operation of the fans is optimized by minimizing the worst-case deviation between the actual air speed and the desired air speed, which can be determined based on either the PMV -SET model or the occupants' feedback. This minimax-error problem is formulated as an equivalent linear programming problem which can be solved using standard methods. The proposed approach was tested in two different indoor scenarios respectively by 1) measuring air speed directly in a business conference room and 2) involving human subject surveys in a university classroom. In the first experiment, the measured air speeds after optimization are closer to the target values at all tested temperature levels (26 °C, 27.5 °C and 29 °C) indicating improved thermal comfort. In the second experiment, only 62% of the occupants (totally 34) are satisfied with slightly increased room temperature (around 26.5 °C) before optimization, while this number increased to 94% after optimization.

Detailed experimental investigation of air speed field induced by ceiling fans

“…The air movement induced with multiple fans can then satisfy more occupants, even when they are not directly under the ceiling fan. Moreover, use of the multiple fans installed in the matrix instead of a single fan in bigger size allows for a cooperative control approach [38], which has the flexibility to adjust fans operation to occupants preferences and furtherly increases their satisfaction. It is possible that running the fans in reverse (moving the air toward the ceiling) may create an even more uniform environment.…”

“…Relative performance of multiple fans has not been reported in the literature, while such information is crucial for successful implementation of fans in large area spaces (e.g., open space offices). The designers need to receive tools addressing this concern to properly select fans' spacing and to optimize the fans' control [38].…”

Comparison of stationary and transient RANS modelling

“…Beside the ve locity, field studies also analyze human perception of air velocities, using questionnaires [6][7][8][9][10] and investigate the usage of ceiling fans by the occupants [11]. Other studies analyze potentials to increase night cooling [12; 13] or the control of stand fans to achieve a homogeneous velocity distribution [14]. Furthermore the ceiling fan blade opti mization for improved aerodynamic performance is in vestigated [15].…”