Thermal stability of the human body under hyperbaric environmental conditions: a theoretical study
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I report here a theoretical study of the dependence on ambient pressure of heat and mass (water vapour) rate transfer processes between the human body and its gaseous surroundings, for monocomponent gases (N2, O2, He) and/or diatomic gas mixtures (He-O2, N2-O2). Heat and water vapour rate transport are described by the following rate transfer parameters: the convective heat transfer coefficient (hc), the evaporative heat transfer coefficient (he) and the Lewis relationship (LR). It is shown that the thermal stability of the human body under hyperbaric conditions is proportional to the evaporative resistance. It is also shown that in a He atmosphere the change in the thermal state caused by a heat load of 1 W·m–2 at sea level is equivalent to the effect of a heat flow of 0.186 W·m–2 at 30 atmospheres absolute. This indicates that the thermal state of the body is more prone to instability at increasing ambient pressures.
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