Estimating the radiation absorbed by a human

Abstract

The complexities of the interactions between long-and short-wave radiation fluxes and the human body make it inherently difficult to estimate precisely the total radiation absorbed (R) by a human in an outdoor environment. The purpose of this project was to assess and compare three methods to estimate the radiation absorbed by a human in an outdoor environment, and to compare the impact of applying various skin and clothing albedos (α h ) on R. Field tests were conducted under both clear and overcast skies to evaluate the performance of applying a cylindrical radiation thermometer (CRT), net radiometer, and a theoretical estimation model to predict R. Three albedos were evaluated: light (α h = 0.57), medium (α h = 0.37), and dark (α h = 0.21). During the sampling periods, the range of error between the methods used to estimate the radiation absorbed by a cylindrical body under clear and overcast skies ranged from 3 to 8%. Clothing and skin albedo had a substantial impact on R, with the mean change in R between the darkest and lightest albedos ranging from 115 to 157 W m −2 over the sampling period. Radiation is one of the most important variables to consider in outdoor thermal comfort research, as R is often the largest contributor to the human energy balance equation. The methods outlined and assessed in this study can be conveniently applied to provide

The influence of surface type on the absorbed radiation by a human under hot, dry conditions

“…1) is a copper cylinder (10-cm height and 1.0-cm diameter) filled with conductive epoxy with a copper-constantan thermocouple inserted in the middle. It is designed to have the representative geometry (cylinder) and radiational properties of an average clothed human (albedo of 0.39 and emissivity of 0.95) (Brown and Gillespie 1986;Kenny et al 2008; Monteith 1973). The CRT measures a value of radiant temperature that is then used to provide a value of R abs (Wm −2 ), which is an integration of the total solar and terrestrial radiation fluxes that are absorbed by a cylindrical body (Kenny et al 2008).…”

“…The combination of all short-and long-wave radiant fluxes in a given point location results in a mean radiant temperature (T mrt ) Kenny et al 2008), which is the most significant heat gain to urban surfaces and human heat load on warm-hot days. Therefore, accurate radiation monitoring or modeling is required for assessing the thermal environment's influence on human heat stress.…”

The influence of trees and grass on outdoor thermal comfort in a hot‐arid environment

“…Such measures typically portray radiant effects using the mean radiant temperature (MRT), which is difficult to quantify in an outdoor urban context due to the multiplicity of radiating surfaces together with the high intensity of solar and atmospheric radiation. Although the measurement of MRT using globe thermometers of varying diameters and materials has received wide attention in recent studies (Ali-Toudert and Mayer, 2006Mayer, , 2007Thorsson et al, 2007;Kenny et al, 2008), this approach is still subject to uncertainties given the extreme variability of air flow and convective heat transfer that is typical in the urban canopy layer.…”

Part A: Assessing the performance of the COMFA outdoor thermal comfort model on subjects performing physical activity

“…Radiation was measured using a cylindrical radiation thermometer (CRT) (Kenny et al 2008) and a CNR1 net radiometer (Model CNR1; Kipp & Konen, Delft, Netherlands). The CNR1 net radiometer provided separate measurements for all four radiation flux components (K T , K r , L a , and L g ) and was secured on a mobile stand (PCS-1; Parktool, USA).…”

“…The methods outlined by Kenny et al (2008) were used to convert the CRT measurements to the radiation absorbed by a human.…”