Glossary

The angle between the direction of interest (the sun, for example) and the zenith (directly overhead).

group of aluminosilicates containing very loosely held cations, used in molecular sieves and ion exchangers.

blend comprising multiple components of different volatilities that, when used in refrigeration cycles, change volumetric composition and saturation temperatures as they evaporate (boil) or condense at constant pressure.

refers to blends comprising multiple components of different volatility that, when used in refrigeration cycles, change volumetric composition and saturation temperatures as they evaporate (boil) or condense at constant pressure. The word is derived from the Greek words zein (to boil) and tropos (to change).

a zeotropic refrigerant contains two or more components whose equilibrium vapor phase and liquid phase compositions differ. The temperature of a zeotropic refrigerant changes as it evaporates or condenses at constant pressure (Compare to [[azeotropic refrigerant]]).

the dead band between control setpoints, such as between heating and cooling, where the lowest amount of mechanical energy is being utilized. Contrast [[dead band]].

residual energy of a system at absolute zero.

if two systems are both in thermal equilibrium with a third one, they are in mutual thermal equilibrium.

(1) a separately controlled heated or cooled space. (2) one occupied space or several occupied spaces with similar occupancy category, occupant density, zone air distribution effectiveness, and zone primary airflow per unit area. (3) space or group of spaces within a building for which the heating, cooling, or lighting requirements are sufficiently similar that desired conditions can be maintained throughout by a single controlling device.

valve that modulates water flow to a thermal zone in response to a downstream temperature signal.

those combinations of air temperature, mean radiant temperature, and humidity that are predicted to be an acceptable thermal environment at particular values of air speed, metabolic rate, and clothing insulation (Icl).

the region normally occupied by people within a space. In the absence of known occupant locations, the occupied zone is to be between the floor and 1.8 m (6 ft) above the floor and more than 1.0 m (3.3 ft) from outside walls/windows or fixed heating, ventilating, or air-conditioning equipment, and 0.3 m (1 ft) from internal walls.

division of a building or group of buildings into separately controlled spaces (zones), where different conditions can be maintained simultaneously.