Abstract
Local thermal sensation modeling gained importance due to developments in personalized and locally applied heating and cooling systems in office environments. The accuracy of these models depends on skin temperature prediction by thermophysiological models, which in turn rely on accurate environmental and personal input data. Environmental parameters are measured or prescribed, but personal factors such as clothing properties and metabolic rates have to be estimated. Data for estimating the overall values of clothing properties and metabolic rates are available in several papers and standards. However, local values are more difficult to retrieve. For local clothing, this study revealed that full and consistent data sets are not available in the published literature for typical office clothing sets. Furthermore, the values for local heat production were not verified for characteristic office activities, but were adapted empirically. Further analyses showed that variations in input parameters can lead to local skin temperature differences (∆Tskin,loc =0.4-4.4°C). These differences can affect the local sensation output, where ∆Tskin,loc =1°C is approximately one step on a 9-point thermal sensation scale. In conclusion, future research should include a systematic study of local clothing properties and the development of feasible methods for measuring and validating local heat production.
Highlights
The built environment currently accounts for 30-40% of the total energy consumption worldwide (IEA, 2013)
The heat production in muscle layers is determined by local metabolic heat distribution coefficients (LDCs)
Thermal sensation can be modeled with multi-segment thermophysiological and coupled sensation models
Summary
The built environment currently accounts for 30-40% of the total energy consumption worldwide (IEA, 2013). These two categories are connected in a general concept of human thermal modelling (Figure 1) This concept includes that TP models require input of environmental variables (e.g. operative temperature, humidity, wind speed), two personal factors namely clothing and metabolic rate and, optionally, individual characteristics (e.g. weight, height, age). Environmental conditions can mostly be obtained, since they are set or measured Personal factors such as local clothing values (insulation and evaporative resistance), metabolic heat production and its local distribution over the body, as well as local tissue insulation have to be estimated. Havenith et al (2002) proposed to include clothing vapor resistance into thermal comfort calculations and to account for the effect of air and body movement on all clothing properties They question the precision of the measurements for metabolic rates and suggest enlarging the database for low level activities. All clothing properties are generally given as whole-body coefficients and values are provided in current standard, e.g. EN-ISO 9920 (ISO, 2009) or ASHRAE/55 (ASHRAE, 2004)
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