Psychrometrics Without Tears

Book excerpt: All You Ever Wanted to Know About Air… And Then Some! A/C technicians should be knowledgeable about air and its properties. This program helps technicians understand the basic properties of air and how these properties relate to each other. Over the years, much has been written on the subject of Psychrometrics. However, much of this material has been geared toward engineering and system design. Psychrometrics Without Tears presents the important concepts of air in a manner that will appeal to HVAC students and service technicians. Knowing all there is to know about an air sample is pretty empowering, so this book starts by discussing the basic properties of air and how these properties relate to each other. The Psychrometric chart is introduced to provide a visual representation of how air behaves when exposed to different conditions. Once the basics of the chart are covered, we then move into some more interesting topics such as sensible heat ratio, bypass factor, and apparatus dew point temperatures. These properties help determine system performance and are very important concepts to learn in order to fully understand air. The plotting of actual systems follows next. This involves plotting out air distribution systems that are operating correctly so that we can see what properly operating systems look like on the chart. This book covers a wide range of systems that includes residential heating and cooling systems as well as commercial systems that provide ventilation air to the occupied space to meet building code requirements. Prepare to learn about mixed air systems and learn to calculate the mixed air conditions provided we know what the outside air and return air conditions are. In addition to everything mentioned already, we will discuss the concepts of ventilation, economizing and air balancing.