Experimental investigation of supplied flow characteristics under impinging jet ventilation systems with round duct supply terminal

• The fundamental IJV flow features were first measured under isothermal conditions. • The supply velocity and turbulence intensity were measured to be 2.8 m/s and 9.8%. • The maximum velocity decay and jet half-width expansion were shown as equations. • The jet profiles at different angles can be predicted using these equations. • The listed findings can be applied to both the isothermal and cooling conditions. Using the impinging jet ventilation system (IJV), it is possible to accomplish high ventilation effectiveness within the occupied zone. Since the supplied air spreads along the floor, the flow feature is assumed to have a large impact on the whole room environment. To understand this, the jet’s velocity profile was measured using a hotwire anemometer under isothermal conditions and particle image velocimetry (PIV) under isothermal and cooling conditions. Firstly, the velocity and turbulence intensity of the supply jet were measured to be around 2.8 m/s and 9.8%, respectively. Secondly, the maximum velocity decay and jet half-width expansion were shown. Thirdly, the relationship between measured dimensionless radial velocity and dimensionless height was shown to have a good agreement with Verhoff’s equation and the free turbulent jet’s equation in most of the regions, regardless of the angle from the wall. Fourthly, the velocity profiles at the central cross-section measured by the hotwire anemometer and PIV are almost the same in the region sufficiently far from the supply duct. Finally, the velocity profiles under isothermal and cooling conditions measured by PIV were practically the same; therefore, it is assumed that the findings listed above can also be applied to cooling conditions as well.