A field study on application of infrared thermography for estimating mean radiant temperatures in large stadiums

•Methods of measuring mean radiant temperature were analyzed with respect to application in large spaces.•An infrared thermal imaging camera was applied for measuring surface temperature, and an MRT measurement method for a large space was derived.•An experimental study was conducted for measuring MRT values in a large space, and the applicability of an infrared thermal imaging camera is discussed. In large-space buildings such as stadiums or auditoriums, the mean radiant temperature (MRT) at an occupant location can be highly influenced by the outdoor thermal environment. Therefore, it is important to measure a wide range of MRT values to understand thermal comfort conditions. This study reports on the importance of MRT measurements when evaluating the thermal environments of large spaces. We present an MRT measurement method using an infrared thermal imaging camera (IR camera). First, MRT measurement methods using a globe thermometer and an IR camera with respect to large spaces were reviewed to assess their limitations and applicability. A method utilizing the IR camera is proposed to enable multiple-location measurements with a single installed device. In our proposed method, MRT values are calculated using angle factors (AF) and mean indoor surface temperatures. A solid-angle algorithm is adopted to calculate AFs at occupant locations using a simplified model of the indoor space. To confirm the applicability of the proposed method in a large space, experiments are conducted using the globe-thermometer method and the IR method. Results show that the MRT values estimated from both methods have similar trends with differences less than 1 °C. The measured surface temperatures using an IR camera show that indoor surface temperatures can be significantly different according to location and orientation. We conclude that the proposed method is capable of measuring MRT values at multiple locations.