A simulation model for radiative heat transfer on a human body in fire based on a new backward ray tracing method

Abstract

Thermal radiation is one of the causes of human injury in fires. In addition to causing direct burns to the body surface, thermal radiation can also result in an increase in body temperature, reduced mobility, dehydration, and life-threatening conditions. Previous studies have focused on the thermal radiation from the fires source, but the simplification of human body structure has limited the ability to calculate the variations in radiant heat flux on different parts of the human body and the influence of human body geometry on radiant heat transfer. In this research, a novel backward ray tracing method is proposed to simulate the radiant heat flux on the surface of the human body while retaining its true geometric features in a fire scenario. Firstly, a discrete human mesh is created and placed in the simulated fire scene. Then, a solid angle segmentation method is introduced, dividing the hemisphere beyond each surface element of the human body mesh into equal size. To validate the proposed method, a pool fire experiment is conducted. This method is then applied to study the distribution of thermal radiant flux on the human surface under different angles between the human mesh and the fire source, as well as varying wind speed in pool fire scenario. When the human body is located downwind of the fire, the largest surface radiative heat flux occurs in the upper body region. Conversely, when positioned upwind, the maximum radiative heat flux is observed on the leg. This study simulated the thermal exposure distance for human body wearing summer clothing in a pool fire experiment. The findings indicate that clothing significantly reduces the exposure distance when the body faces toward or away from the fire source. However, when the body is oriented sideways relative to the fire source, clothing demonstrates minimal effect on the safe exposure distance. The proposed method can be used for fire escape planning and the design of fireproof clothing.