Developing small-sized thermal dummies to reproduce human convective airflows in ventilation effectiveness measurement

• Developed small-sized dummy can replicate human plumes for ventilation assessments • Velocity profile and ventilation effectiveness outperformed standard dummies • The small-sized dummy’s plume volume flow aligns with the human value of 20 L/s • Ventilation effectiveness with small-sized dummies matches human presence • Unheated fans showed reasonable performance in mixing ventilation measurements This study introduces and validates a compact, small-sized thermal dummy designed to replicate human convective airflows in ventilation effectiveness assessments. Addressing limitations of conventional manikins and standard cylindrical dummies, particularly their size, cost, and limited portability, this novel dummy integrates a heating element and a top-mounted fan to replicate the thermal plume of a seated human. Air velocity measurements under non-ventilated and ventilated conditions confirmed that the small-sized dummy generates a convective plume and volumetric flow rates closely matching those of human subjects. In contrast, standard dummies showed lower velocities and a flatter profile. Tracer gas measurements of dummies’ impact on ventilation effectiveness were conducted using two air distribution strategies, duct diffusers and mixing ventilation, which showed the importance of heat output. While the small-sized dummy provided the results closest to human occupancy, standard dummies showed considerably higher ventilation effectiveness than observed in an unoccupied room. An unheated fan was measured as the simplest possible alternative to dummies, and results were obtained for dummies and unoccupied rooms. Despite its limitations, it may be a reasonable alternative for mixing ventilation measurements. In conclusion, under both ventilated and non-ventilated scenarios, the small-sized dummy demonstrated performance characteristics nearly equivalent to those obtained in human presence, surpassing the results of standard dummy configurations. The results underscore the small-sized dummy’s capacity to provide a reliable, portable, and cost-effective alternative for field measurements in indoor environments.