Dependence of the indoor 222Rn concentration on the temperature difference between two adjacent indoor spaces or rooms was investigated. The variations in 222Rn concentration in a vessel with two orifices were measured at various inner-to-outer temperature differences, and were numerically modeled based on a theoretical consideration on the static pressure difference. An equation to calculate the decrease of 222Rn concentration as a function of the temperature difference between two adjacent spaces was developed. The calculation results using the developed equation in this study, if the drag coefficient of the orifice flow was properly formulated as a function of the Reynolds number, were consistent with the measurement results. The equation developed in this study can be applied to the real case (rooms with several orifices). The approach taken in this study can also be performed to measure accurately a very low air flow (Reynolds number < 100).
- Decrease rate
- Radon-222 concentration
- Temperature difference-driven flow
- Very low airflow measurement