Evaluation of Thermal Comfort in Slightly Warm Ventilated Spaces in Nonuniform Environments

Abstract

The present work analyzes and evaluates the global thermal comfort and local thermal discomfort levels of an occupant subjected to a symmetric nonuniform airflow, originated in common use ventilators. Several incident airflow directions are studied and their effects are described. The global thermal comfort level is evaluated through a multi-nodal numerical model that simulates human and clothing thermal responses, while the local thermal discomfort level is analyzed using an empirical model that predicts draft risks.

The computational model of the human body and clothing thermal systems is based on the energy balance integral equations for human body tissue, blood, and clothing, as well as mass balance integral equations for the blood and transpired water in skin surface and the clothing. The human body is divided into 35 elements, each one in several layers of tissue, which could be protected through some clothing layers. A thermoregulatory system model was adapted to control the human body tissue temperature.

The experimental tests were carried out in a test chamber in controlled environmental conditions; a thermal manikin was used to simulate the human posture, an indoor climate analyzer was used to measure the environmental variables around the occupant, and two ventilators were used to produce an airflow field around the occupant. The frontal and ascendant airflows from the ventilators placed in front of the occupant are characterized and their velocities around the occupant are measured for several incident angles. The global thermal comfort conditions of the occupant are evaluated both with and without ventilation, and the local thermal discomfort level is evaluated with ventilation for slightly warm, moderate environments.