Effects of the environment on thermo physiological responses via 3D human eye model with porous media heat transfer theory under inconstant solar irradiation

Abstract

Abstract The human eye is one of the most sensitive parts of our entire body. The lens is an important component of the eye, and it also plays an important role in vision. A lens has a normal temperature below 38.5°C. Thermal effects with solar irradiation result in the temperature of the lens to increase to more than 38.5 °C and may significantly influence the thermal physiologic response which, in turn, will cause the of deterioration of the lens. Therefore, investigation to get knowledge and guidelines to avoid thermal effects from the environment with solar irradiation, will help prevent the eyes from deterioration. However, the study of invasion, within the human body is impracticable. The study of environmental effects on thermo physiological responses within the human eye, from numerical analysis, is another alternative that is gaining attention worldwide. The purpose of this research is to learn about thermal physiologic response on human eyes exposed to solar irradiation, using the three-dimensional (3D) model by finite element method (FEM) via a computer program. This study uses the heat transfer equation and the Navier-Stroke equation to describe heat transfer phenomena in porous mediums and fluid flow phenomena within the 3D human eye model, based on considering the natural convection heat transfer of aqueous humor and vitreous humor, under inconstant solar irradiation. The effects of the environmental parameters such as ambient temperature and air convection heat transfer coefficient are investigated. The results show that the case study which makes the best cooling mechanism is the effect of ambient temperature with ambient temperature at 25°C and effect of air convection heat transfer coefficient at 40 W/m2·K that the eye can absorb maximum solar irradiance at 575 W/m2 at the lens reaches 38.5°C and the worst cooling mechanism is the effect of ambient temperature with ambient temperature at 35°C that the eye can absorb maximum solar irradiance at 360 W/m2 at the lens reaches 38.5°C. The results from this study provide the essential aspects for a fundamental understanding of thermal physiologic response within human eye subjected to solar irradiation.