Heat source plumes are a type of airflow pattern that universally exists in daily life and work. However

it causes a considerable interference to the ventilation airflow which helps in creating a comfortable indoor environment. In this study

to avoid the interference of the test instrument on the heat source plume

a two-dimensional particle image velocimetry system with splicing technology was applied to measure the vertical area of the surface-source plumes with different heat source strengths and sizes so that more accurate motion characteristic equations and global airflow distribution can be obtained. Based on the measured data

the axial velocity and expansion radius of the surface-source plume were fitted by formulas and the fitting coefficients were discussed. A simple and accurate expression of the axial velocity of the plume from a circular area source was obtained and the coefficients in the formula were fitted and corrected. The radius of the heat source was in the range of 0.05–0.125 m

while the heat dissipation capacity was in the range of 40–120 W

which could better reflect the relationship between the axial velocity of the thermal plume and height away from the heat source.