Effect of apertures on ventilation rates and heat loss from clothed heated cylinder in cross wind -

Abstract

The purpose of this work is to implement an integrated heat transport model of clothed human body subject to external wind. Each clothed segment of the human body is modeled as a vertical annulus of a heated cylinder surrounded by a permeable cylinder, subject to cross uniform wind with open or close end to the environment, depending on the aperture configuration, in the presence of natural convection. The flow and heat transport characteristics are obtained by solving the steady state mass and energy balance equations of body segments ’microclimate air annulus numerically. The model is then integrated with a segmental bioheat model to accurately determine the segmental skin temperature to be used as heated surface boundary condition in the model. Experiments were performed in a low speed wind tunnel in which an isothermally heated vertical clothed cylinder with open bottom aperture was placed in uniform cross wind. Good agreement was found between the model predictions and experimental measurements of temperature at different angular and vertical location in the microclimate air layer. The combination of the mathematical model and the segmental bioheat model is then validated with published experimental data on ensemble total ventilation for different types of clothing permeability and wind speeds. It is found that clothed segments opened from bottom increases ventilation rate by 40 percent when compared to clothed segments opened from top. Furthermore, an increase of wind speed by 1.0 m-s leads to an increase of about 36 percent of ventilation rate. Permeability also plays another role in enhancing ventilation and total heat loss from the clothed segment especially when natural convection is important.