• ASHRAE 90167
  • Revision:2013 Edition, January 1, 2013
  • Published Date:January 2013
  • Status:Active, Most Current
  • Document Language:English
  • Published By:American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)
  • Page Count:403
  • ANSI Approved:No
  • DoD Adopted:No

  • How to Use this Book

    vMIn general, each chapter is written as a stand-alone sectionso that it is possible to pick and choose chapters and, as such,the text serves as a reference for those with prior knowledge ofpsychrometrics.

    The book also serves as a four- to six-hour introduction to thescience of psychrometrics for those new to the subject, and thisinfluenced the sequencing of chapters. The clock in the margin ofthis paragraph and elsewhere in this book indicates the text thatshould be read in a four- to six-hour learning session.

    Since this bookwas written as both a learning module and areference book, many of the definitions, physical phenomena, andequations are explained in more detail than found in a basic book.The reader should have a general background knowledge equivalent toa high school physics or general science course. For those somewhatfamiliar with psychrometrics in inch-pound (I-P) units, this textwill not only provide an easy transition to psychrometrics inSystème International (SI) units but also a quick refresher on theunderlying principles of psychrometrics. Learning psychrometricstoday is easier because of the SI coherent system of units, whicheliminates duplicate units and conversions, and because of thepersonal computer and software that has all but eliminated not onlymanual computations using approximate formulae but also graphicalsolutions using the psychrometric chart.

    Psychrometrics brings with it many new terms and concepts. Sometexts introduce all of the terms and concepts in a single chapter.For many, including the author, this can produce brain overload andconfusion and is an obstacle to the learning process, which is,after all, the goal. In this book, definitions and new concepts areintroduced as needed and each psychrometric property istreated in a separate chapter. In general, equations thatinterrelate the properties are introduced with the property.

    An exception to the as needed introduction of terms andconcepts is Chapter 5, "Basics of the Psychrometric Chart," whichprecedes the individual chapters on psychrometric properties. Thepsychrometric chart is a convenient and useful tool for determiningpsychrometric properties and visualizing the changes to moist airproperties in psychrometric processes. This early chapter isintended to give the reader an overview of the chart to help inoverall understanding and to add clarity and meaning as eachpsychrometric property is developed and discussed in subsequentchapters.

    The choice of whether or not to read Chapter 8, "PsychrometricPioneers and Charts from the First 100 Years," is left to thereader. It may pique the reader's interest. It may help to explainthe evolution of this science and the plethora of sometimesoverlapping and confusing terms introduced into psychrometrics fromthe fields of meteorology, drying of materials, air conditioning,thermodynamics, chemical engineering, and agriculturalengineering.

    Each of the chapters dealing with individual psychrometricproperties defines and discusses the property at several levels ofdetail. Those new to psychrometrics and those interested in a quickrefresher or overview may want to read only the definitions and thefirst level of detail and then move on to the next chapter. In mostcases, multiple definitions are provided. The first definition issuitable for general lay-person discussion. Subsequent definitionsare more complete and technically more accurate. A definitionserves no purpose unless it provides meaning and understanding forthe reader. Multiple definitions allowthe reader to choose thedefinitions that have the most meaning. Readers are encouraged tocustomize definitions.

    A skeleton psychrometric chart highlighting only the isolines ofthe property under discussion is included in each propertychapter.

    Chapter 25 on altitude effects for locations other thansea level is required reading for those readers who live in ordesign for deep underground applications or applications forprojects at high elevations; but, for most users concerned withpsychrometrics within ±500 metres of sea level, this chapter can bescanned for future reference or skipped altogether. This chapteralso illustrates the change in altitude (or local barometricpressure) effect on the appearance of the psychrometric chart.

    ASHRAE 90167

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