Outdoor performance of the black globe temperature sensor on a hot and humid tropical region

ABSTRACT

A crucial variable to evaluate thermal comfort is the mean radiant temperature (T_mrt). In this paper we evaluate the performance of the 150 mm black globe thermometer to provide reliable T_mrt values for outdoor settings in Singapore. Accurate T_mrt values are calculated by the method of integral radiation measurements. Based on these, the mean convection coefficient of the black globe has been re-calibrated. Results show an improvement in the estimation of T_mrt with the new coefficient in comparison with the default version suggested in ISO7726:1998. Increasing the averaging periods of the measured variables improved the performance of the derived mean convective coefficients to estimate T_mrt. During clear skies day and for 10-min averaged data, RMSE for T_mrt reduce to 3.9 °C (7.4 °C for ISO7726:1998 coefficient) with an overestimation on high incoming solar radiation periods and an underestimation during the morning and evening (low solar elevation). During overcast dry conditions an underestimation of T_mrt is also expected which is higher in the rain/wet periods. The mean convective coefficient presented in this work can provide improved estimations of Tmrt relevant for outdoor thermal comfort studies in hot and humid tropical climates like Singapore.

GRAPHICAL ABSTRACT

KEYWORDS:

• Black globe thermometer
• mean radiant temperature
• Singapore
• calibration
• mean convection coefficient

Acknowledgments

We would like to thank Prof. Wong Nyuk Hien (National University of Singapore) for sharing the radiometers used for this work, and also Dr. Cuauhtemoc Anda (Future Cities Lab, SEC) for the help provided.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available on request from the authors J. A. Acero and A. Dissegna. Restrictions apply to the availability of these data, which were used for this study. Data are available from authors J. A. Acero and A. Dissegna with the permission of Singapore National Research Foundation (NRF).

Additional information

Funding

This research is supported by the Singapore National Research Foundation under its Campus for Research Excellence and Technological Enterprise (CREATE) programme and its “Cooling Singapore” collaborative project (Grant number: NRF2019VSG-UCD-001) led by the Singapore-ETH Centre (SEC), with Singapore MIT Alliance for Research and Technology (SMART), TUMCREATE (established by the Technical University of Munich), the National University of Singapore (NUS) and the Singapore Management University (SMU).