Lumped versus distributed thermoregulatory control: Results from a three-dimensional dynamic model

Abstract

In this study we use a three-dimensional model of the human thermal system, the spatial grid of which is 0.5 ... 1.0 cm. The model is based on well-known physical heat-transfer equations, and all parameters of the passive system have definite physical values. According to the number of substantially different areas and organs, 54 spatially different values are attributed to each physical parameter. Compatibility of simulation and experiment was achieved solely on the basis of physical considerations and physiological basic data. The equations were solved using a modification of the alternating direction implicit method. On the basis of this complex description of the passive system close to reality, various lumped and distributed parameter control equations were tested for control of metabolic heat production, blood flow and sweat production. The simplest control equations delivering results on closed-loop control compatible with experimental evidence were determined. It was concluded that it is essential to take into account the spatial distribution of heat production, blood flow and sweat production, and that at least for control of shivering, distributed controller gains different from the pattern of distribution of muscle tissue are required. For sweat production this is not so obvious, so that for simulation of sweating control after homogeneous heat load a lumped parameter control may be justified. Based on these conclusions three-dimensional temperature profiles for cold and heat load and the dynamics for changes of the environmental conditions were computed. In view of the exact simulation of the passive system and the compatibility with experimentally attainable variables there is good evidence that those values extrapolated by the simulation are adequately determined. The model may be used both for further analysis of the real thermoregulatory mechanisms and for special applications in environmental and clinical health care.

Progress in thermal comfort research over the last twenty years

“…Heat exchanges between the segments are conducted through the central blood (as another node). Along with the multinode human physiology modeling, there have been other finite difference (Wissler, ) and finite element schemes (Smith, ) or 3D models (Werner, ), which are not discussed in this review.…”

Design and Control Optimization of Microclimate Liquid Cooling Systems Underneath Protective Clothing

“…4,7,[18][19][20][21]48,109,111,131,132 Thereafter, optimization attempts focused more on engineering and physiological aspects of cooling distribution (i.e., whole-body vs. regional cooling) 8,30,45,48,75,92,94,107,111,141,146 and system control. 9,17,30,33,[57][58][59]74,95,96,120,135,[137][138][139][143][144][145] The latter will be discussed analytically in a subsequent part of this paper, while the present section will focus on mechanical LQ MCS optimization, that is, tubing network properties and tubing/cooling distribution.…”

Control of metabolic rate is a hidden variable in the allometric scaling of homeotherms

“…Although we offered saturation of responses as an example, we also acknowledge that a multiplicity of controllers, spatial heterogeneities in temperature distribution, non-linearities in the controllers themselves, and others (e.g. Gordon and Heath, 1983;Werner et al, 1989) would render the temporal patterns of the system more realistic, yet much more complex. The important point is that such temporal patterns would be more distant from the well-behaved δB=0 of the classical SMR.…”