heat balance

(geophysics) The equilibrium which exists on the average between the radiation received by the earth and atmosphere from the sun and that emitted by the earth and atmosphere.
(metallurgy) The calculation used in fluidization roasting so that the addition or removal of heat can be controlled to maintain the optimum temperature in the reacting vessel.
(thermodynamics) The equilibrium which is known to exist when all sources of heat gain and loss for a given region or body are accounted for.

A condition reached when the heat gained by a body is equal to the heat lost from it. The amount of stored heat does not change and the body temperature remains constant. It is particularly important that the temperature around the vital organs of the human body is kept at about 37°C because this is the temperature at which they work most efficiently. Mechanisms within the body maintain a constant internal temperature by ensuring that heat gained from body activities and the environment equals heat losses. Considerable heat is generated by the body's activities. During exercise, the metabolic rate can increase as much as 25 times the basal rate. Only about 30 per cent of this energy is used in movement, the rest is converted to heat which could produce a theoretical increase in body core temperature of 1°C every 5 minutes. In order to prevent overheating, the excess heat must be lost. Evaporation of sweat and convection by air currents of the heat and water vapour away from the body surface is an important cooling mechanism. This is one reason why exercisers should wear comfortable, loose-fitting clothes and drink plenty of watery fluids. Conversely, in cold environments it is important to insulate the body surface to prevent hypothermia.

1. A procedure for determining the efficiency of a combustion process: all heat losses (expressed as percentages) are added together; then their total is subtracted from 100%; the remaining figure represents the efficiency.
2. The establishment of a condition of thermal equilibrium in a space, wherein the heat gains just equal the heat losses.

A condition reached when heat gained by a body is equal to heat lost from it. At heat balance, the amount of stored heat does not change and the body temperature remains constant. In humans, heat is exchanged with the environment by radiation, conduction, convection, and evaporation. In addition to external sources of heat, heat is also gained internally by metabolism. During exercise, metabolism increases dramatically and produces much heat. Evaporation of sweat is the major means of losing this heat.

Heat balance
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