2007, Piran, Slovenia

Clothing
EFFECT OF CLOTHING INSULATION ON ATTENUATION OF
RADIATIVE HEAT GAIN.
Emiel A Den Hartog, Peter Broede, Victor Candas, George Havenith
TNO Defence, Security and Safety, Business Unit Human Factors, Soesterberg, The
Netherlands
Contact person: emiel.denhartog@tno.nl
INTRODUCTION
The ThermProtect project, financed by the European Union, is aimed at addressing
the effects of radiative heat and moisture on clothing insulation, especially focussing
on the effect these sources of heat transfer may have on current standards on
protective clothing. In one work package, the effect of heat radiation on heat exchange
was studied in manikins, as well as in humans. As a wide variety of clothing and
radiative environments was studied, there was a need for modelling these data to be
able to fully comprehend the results. Also, the modelling effort should serve as a basis
to transfer the results to the relevant standards for protective clothing. In this paper, a
modelling approach is presented, that is aimed to describe the effect of different levels
of insulation on the attenuation of radiative heat gain from external sources.
METHODS
The modelling effort was based on experimental data that were collected in manikin
measurements during the ThermProtect project. The properties of the model are
briefly discussed, and then the prediction of the model is compared to the results of
the manikin experiments within the ThermProtect project. In a previous paper, only
the data on basic black Nomex® fabrics were presented. In this paper, the results from
other materials, with different colours or with different reflective properties, are
presented The experimental data contain measurements of manikin heat loss in the
infrared and visible radiation spectra, with clothing ensembles consisting of two and
three layers, and at different wind speeds ranging from 0.5 m/s up to 2 m/s.
RESULTS
Comparison of the model predictions with these experimental data shows that the
clothing model explains a large part of the variation of the experimental data. When
more complex types of (reflective) clothing are incorporated, the model clearly does
not explain all of the experimental variation. This is due to the direct effect of the
clothing on the radiative properties (reflection) and requires an extension of the model
to describe the attenuation of the radiative field by clothing with low emissivity
values. However, there is no simple way to insert a single emissivity value into the
model, as the incoming radiation may have another emissivity value than the radiation
that is emitted from the clothing. This effect complicates a straightforward analysis. A
model to describe these effects has been studied within the ThermProtect project and
may be published later.
DISCUSSION
The current model describes the attenuating effect of clothing on radiation for one
type of clothing. The model shows that an increase in clothing insulation decreases
heat gain to the wearer. When the radiation levels become very high, it shows that
increasing the insulation is as beneficial to the wearer as the increase in insulation is
to losing heat. Thus heat strain is counteracted by reducing heat gain from radiation.
These results are relevant at moderate to high levels of radiation.
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