There are numerous occupational and leisure tasks for which the participants are at risk of heat stress related illness. Heat stress illness effects can be either acute, such as heat stroke, heat exhaustion, heat cramps, fainting, and decline of performance; or chronic, such as loss of ability to tolerate heat, hypertension, heart muscle damage, reduced libido and impotence.
Existing practices for protection against heat stress are limited to awareness education of antagonistic conditions. Persistent monitoring of individuals is not an existing practice due to a variety of factors, including drawbacks to the sensor devices and lack of quantitative definition of heat stress limits.This project presents a Bondgraph model to illustrate the body-ambient heat exchange and how it would be measured using a heat flux transducer. Individual contributions to body heat are shown as r-elements. A measurement device of a heat flux transducer is shown as a transformer element. The equation layer of the model can be tailored for various operating conditions, using either derived or empirical formulas to describe heat transfer.
The model shows the same various components of body ambient heat exchange as are found in most occupation educational literature. Bondgraph figures further demonstrate causality and direction of power flow. Not fully quantified in the literature uncovered in research are how the body thermoregulatory functions begin to break downThis data suggest that given a sound understanding of the heat transfer mechanisms operating with the human body during high risk tasks and environments, a heat flux transducer should provide a leading indicator of heat stress illness for any variety of tasks.
Introduction
There are numerous occupational and leisure tasks for which the participants are at risk of heat stress related illness. Current practices for protection against heat stress illness are limited to education and self evaluation. Independent monitoring by means of sensors has not been adopted by industry due to reasons of impracticality. Direct measurement of body core temperatures is impractical for the majority of occupational and leisure tasks.
The model presented in this paper shows all elements of heat transfer, providing a complete systematic view of antagonistic conditions and the human body. This paper describes how heat stress illness can be prevented by monitoring the body thermoregulatory response and predicting catastrophic failure. This is evident in measuring the heat transfer to and from the body, and comparing this data to heat transfer during normal operation.
Body thermal regulation mechanisms and antagonistic conditions
The human body at all times will strive to maintain a core temperature at approximately 37±0.6ºC. The core temperature is defined as the temperature of the arterial blood at the aorta. The high specific energy of blood and low thermal impedance to internal organs maintain critical organs at a temperature very similar.
