Measuring turbulence intensity and length scale using low-cost cylindrical sensors for quantifying human convective heat transfer in outdoor flows*

Developing accurate yet affordable sensors for measuring human radiative and convective exposure in extremely hot conditions can inform behavioral, policy, and infrastructure decisions around heat. While there are many such radiation sensors, quantification of convective heat transfer from the human body in outdoor flows, which are highly turbulent, requires expensive 3D anemometers and advanced data processing. Specifically, besides mean wind speed, turbulence intensity (TI), and turbulence length scale (Lt) substantially impact the forced convection heat transfer coefficient from the human body [1]. Here, we explore an alternative approach based on three heated isothermal cylinders with the same optical properties but varied diameters [2]. By accounting for thermal radiation using another set of cylinders with varied properties but the same diameter [2], the mean wind speed, TI, and Lt are the only unknowns in energy balances on the three varied diameter cylinders. We discuss the performance of the cylinders in measuring the three airflow parameters in grid-generated turbulent flow in a wind tunnel and in highly non-stationary outdoor flow.

[1] Joshi et al (2024) Sci Total Environ, 923, 171525.

[2] Rykaczewski et al (2024) Int J Biometeorol, 68, 1081-1092.