TABLE OF CONTENTS This chapter covers the fundamentals of thermodynamics, fluid mechanics, and heat transfer as related to the theory and practice of air conditioning, heating and ventilation. Basic concepts needed for the HVAC professional are presented, while advanced topics are not considered. Excellent resources, such as the ASHRAE Handbook series and many great textbooks in the areas of thermal fluid sciences, treat the details and advanced topics that have been omitted from this focused chapter.
Thermodynamics is the study of energy, its transformations, and its relation to states of matter or substance. Thermodynamics deals with equilibrium conditions that are typical of steady state, and any changes are considered to be quasi-equilibrium processes where change occurs slowly and incrementally so as to allow each incremental intermediate state to reach equilibrium before it advances further.
A pure substance has a homogeneous and invariable chemical composition. It can exist in more than one phase, but chemical composition is the same in all phases. If a substance exists as liquid at saturation temperature and pressure, it is called a saturated liquid. If the temperature of the liquid is lower than the saturation temperature for the existing pressure, it is called either a subcooled liquid (the temperature is lower than the saturation temperature for the given pressure) or a compressed liquid (the pressure is greater than the saturation pressure for the given temperature). When a substance exists as part liquid and part vapor at the saturation temperature, its quality is defined...
