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Building Design and Construction Handbook - Merritt - Ventech!

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SECTION THIRTEEN<br />

HEATING, VENTILATION, AND<br />

AIR CONDITIONING<br />

Lawrence E. McCabe*<br />

Chief Engineer—Mechanical<br />

STV Group<br />

Douglassville, Pennsylvania<br />

The necessity of heating, ventilation, <strong>and</strong> air-conditioning (HVAC) control of environmental<br />

conditions within buildings has been well established over the years<br />

as being highly desirable for various types of occupancy <strong>and</strong> comfort conditions as<br />

well as for many industrial manufacturing processes. In fact, without HVAC systems,<br />

many manufactured products produced by industry that are literally taken for<br />

granted would not be available today.<br />

13.1 DEFINITIONS OF TERMS OF HEATING,<br />

VENTILATION, AND AIR CONDITIONING<br />

(HVAC)<br />

Adiabatic Process. A thermodynamic process that takes place without any heat<br />

being added or subtracted <strong>and</strong> at constant total heat.<br />

Air, Makeup. New, or fresh, air brought into a building to replace losses due to<br />

exfiltration <strong>and</strong> exhausts, such as those from ventilation <strong>and</strong> chemical hoods.<br />

Air, Return (Recirculated). Air that leaves a conditioned spaced <strong>and</strong> is returned<br />

to the air conditioning equipment for treatment.<br />

Air, Saturated. Air that is fully saturated with water vapor (100% humidity),<br />

with the air <strong>and</strong> water vapor at the same temperature.<br />

Air, St<strong>and</strong>ard. Air at 70�F (21�C) <strong>and</strong> st<strong>and</strong>ard atmospheric pressure [29.92 in<br />

(101.3 kPa) of mercury] <strong>and</strong> weighing about 0.075 lb/ft 3 (1.20 kg/m 3 ).<br />

Air Change. The complete replacement of room air volume with new supply air.<br />

*Revised <strong>and</strong> updated from the previous edition by Frank C. Yanocha.<br />

13.1

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