Influence of relayed fans and low level exhausts on performance of attachment ventilation under heating mode

Abstract Compared with displacement ventilation, attachment ventilation characterized by high supply air momentum has the potential to generate warm air lake on the floor under winter heating mode. However, the airflow can not keep attaching to the floor and moves upwards by thermal buoyancy. The influence of relayed fans and low level exhausts on performance of attachment ventilation under heating mode was explored. One/two relayed fans and five dimensionless exhaust heights were investigated. Performance evaluating index include vertical temperature gradient, temperature efficiency, predicted mean vote (PMV), predicted percentage of dissatisfied (PPD) and Draught risk (DR). Simulation results showed that relayed fans and low level exhausts effectively increase the attachment length of warm air lake in winter. Operation of relayed fans reduces vertical temperature difference, maintaining the head and foot temperature difference less than 3 °C. Low level exhausts effectively increase occupant zone temperature, reduce airflow short circuit and improve temperature efficiency. The operation of relayed fans slightly increase the temperature efficiency under high level exhausts. Two relayed fans decrease the temperature efficiency under low level exhausts. Better performance can be achieved by using only one relayed fan.