Production metabolic heat

All assessments of thermal environments require an estimate of the metabolic heat production of the occupants. ISO EN 8996 presents three types of methods. The first is by use of tables, where estimates are provided based on a description of the activity. These range from a general description (light. 

The second method is by use of the heart rate. The total heart rate is regarded as a sum of several components and, in general, is linearly related to the metabolic heat production for heart rates above 120 beats per minute. Heat stress will, however, also increase the heat rate. The third method is to calculate the metabolic heat production from measures of oxygen consumption, and carbon dioxide production during activity and recovery. 

Metabolic heat production The production of body heat due to the intake of oxygen and carbohydrates. 

Functionally, the onset of fever is mediated by an increase in metabolic heat production (thermogenesis) and cutaneous vasocontriction (to reduce heat loss from the skin), and by cessation of sweating, if present. The... 

At low cirabient temperatures a greater portion of the metabolic heat production (depending upon exercise intensity and clothing) is dissipated by convection and radiation and a minor portion by evaporation of sweat and respiratory water. As ambient temperature rises, the portion of heat dissipated by convection and radiation decreases progressively in concert with a proportional increase in the rate of sweating and evaporative heat loss. The coordination of the rate of heat loss between conduction, radiation, and evaporation is so precise that, for ambient dry-bulb temperatures between 5 C and 29 C, the equilibrium level of core (rectal) temperature is related directly to the intensity of the exercise load and is independent of environmental temperature (25). 

Heat stress is a constant and potentially severe health threat to the worker in toxicological protective clothing. The combination of exposure to solar radiant energy or enclosed areas with high temperatures, metabolic heat production, and the use of impermeable clothing (which prevents evaporative cooling) place the chemical worker at high risk for heat injury. 

The human heat balance equation is used to describe the balance of the thermal system of a person. There have been many models proposed, the aims of which are to show the balance of the metabolic heat production—the metabolic energy produced (M) minus the energy of mechanical work done (W)—and the sum of all the heat loss systems, including the rate of heat storage (i.e., whether the system is heating up or cooling down) (Fanger, 1972 Parsons, 2002). 

Activity Metabolic heat production Air flow Ideal clothing response... 

The body has a very limited capacity to adjust to cold environmental conditions. Adjustments in blood circulation may conserve body heat, and shivering increases metabolic heat production slightly. 

Figure 19.1 Schematic representation of the pathways for heat loss from the body (M = metabolic heat production).

Problems have also occurred from over-interpretation of the consequences of metabolic heat production in plants. In a series of papers, Raskin and coworkers [55-57] postulated that a temperature increase from metabolic heating protects... 

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