Predicting segmental and overall ventilation of ensembles using an integrated bioheat and clothed cylinder ventilation models

Abstract

The purpose of this work is to implement an integrated ventilation and heat transport model of a clothed human subject to external wind. Each segment of the human body is modeled as a vertical cylinder with an air annulus separating the ventilated clothing from the skin with open or closed end to the environment. The developed ventilation model takes into consideration natural convection induced by the temperature difference between the skin and the annulus air. The steady-state mass and energy balance equations of the annulus microclimate air and clothing were solved numerically. The model is integrated with a segmental bioheat model to determine the local skin temperature, which is used as boundary condition. The clothing ventilation model was validated by conducting experiments on an isothermally heated vertical clothed cylinder with an open lower end aperture and subject to a uniform cross wind. Good agreement was found between the model predictions and experimental measurements of temperature at different angular and vertical locations in the air layer. The combined clothed cylinder and segmental bioheat model was validated with published experimental data on ensemble total ventilation for different permeabilities and wind speeds. It was found that clothed segments opened from the bottom increased ventilation by 40% when compared to clothed segments opened from the top. An increase of wind speed by 1.0 m/s leads to an increase in ventilation rate of about 36%. Natural convection was also found to enhance the ventilation of highly permeable clothing at low wind speeds compared to less permeable clothing.