TABLE OF CONTENTS In order to apply the heat balance procedures to calculating cooling loads, it is necessary to develop a suitable framework for the heat transfer processes involved. This takes the form of a general thermal zone to whose surfaces and air mass the heat balance can be applied. A thermal zone is defined as an air volume at a uniform temperature plus all the heat transfer and heat storage surfaces bounding or inside of that air volume. It is primarily a thermal, not a geometric concept, and can consist of a single room, a number of rooms, or even an entire building. Generally, it parallels the HVAC system concept of the region, which is controlled by a single thermostat. Note particularly, however, that such things as furniture are considered part of the thermal zone.
The heat balance procedure for load calculations needs to be flexible enough to accommodate a variety of geometric arrangements, but the procedure also requires that a complete thermal zone be described. Because of the interactions between elements, it is not possible to build up the zone behavior from a component-by-component analysis. To provide the necessary flexibility, a generalized 12-surface zone can be used as a basis. This zone consists of four walls, a roof or ceiling, a floor, a thermal mass surface. Each of the walls and the roof can include a window (or skylight in the case of the roof). This makes a total of 12 surfaces, any...
