The influence of a sweat rate on heat losses of the selected segments of a sweating thermal manikin

Abstract

The procedure of determining the heat resistance, i.e. thermal insulation is described in a series of the European Standards. It is well recognised and disseminated across the world. However, there is no European Standard with regard to the procedure for determining clothing evapourative resistance (R_et). In 2016, ASTM published F2370 standard where it set out the method for determining R_et. The said standard however is lacking detailed information concerning the required sweat rate for a manikin. The aim of the present study was to examine the influence of a sweat rate on the segmental heat losses at the selected manikin’s parts in the so-called isothermal and non-isothermal conditions. The research was carried out on the NEWTON thermal manikin dressed in special fabric skin. Four sweating rates were considered, i.e. 100, 250, 500 and 650 g/(h m²). The results showed different segmental heat loss in isothermal and non-isothermal conditions. It was furthermore found that heat loss depended on a sweat rate, namely a lower sweat rate caused lower heat loss.

Keywords:

• Thermal manikin
• evaporative resistance
• sweat rate
• sweating
• wet heat exchange

Acknowledgement

This paper has been based on the results of a research task carried out within the scope of the third stage of the National Programme “Improvement of safety and working conditions” partly supported in 2014–2016 — within the scope of state services — by the Ministry of Labour and Social Policy. The Central Institute for Labour Protection – National Research Institute is the Programme’s main co-ordinator.

Disclosure statement

No potential conflict of interest was reported by the author.

Notation

A   area of the manikin’s surface that is sweating (m²)

H_e  power required for the sweating areas (W)

H_L  total heat loss during thermal manikin’s sweating (W/m²)

p_a  water vapour pressure in the air flowing over the clothing (kPa)

p_s  water vapour pressure at the manikin’s sweating surface (kPa)

R_et  total evaporative resistance (kPa m²/W)

RH  relative humidity (%)

RH_s  relative humidity measured on skin/manikin’s surface (%)

R_t   total thermal resistance (R_t – according to ASTM F2370-16)

R_ct  according to EN 342 (°C m²/W)

t_a   ambient temperature (°C)

t_s   temperature at the manikin surface (°C)

V_a   air velocity (m/s)

X_i   value for i-segments of manikin

λ   heat of vapourisation of water at the measured surface temperature (W)

dm/dt evaporation rate of moisture leaving the manikin’s sweating surface (g/min)