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Application Of Excel In Psychrometric Analysis

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2010 Annual Conference & Exposition


Louisville, Kentucky

Publication Date

June 20, 2010

Start Date

June 20, 2010

End Date

June 23, 2010



Conference Session

Thermodynamics, Fluids, and Heat Transfer II

Tagged Division

Mechanical Engineering

Page Count


Page Numbers

15.183.1 - 15.183.20



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Paper Authors


Amir Karimi University of Texas, San Antonio

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Amir Karimi is a Professor of Mechanical Engineering and the Associate Dean of Undergraduate Studies at The University of Texas at San Antonio (UTSA). He received his Ph.D. degree in Mechanical Engineering from the University of Kentucky in 1982. His teaching and research interests are in thermal sciences. He has served as the Chair of Mechanical Engineering (1987 to 1992 and September 1998 to January of 2003), College of Engineering Associate Dean of Academic Affairs (Jan. 2003-April 2006), and the Associate Dean of Undergraduate Studies (April 2006-present). Dr. Karimi is a Fellow of ASME, senior member of AIAA, and holds membership in ASEE, ASHRAE, and Sigma Xi. He is the ASEE Campus Representative at UTSA, ASEE-GSW Section Campus Representative, and served as the Chair of ASEE Zone III (2005-07). He chaired the ASEE-GSW section during the 1996-97 academic year.

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Randall Manteufel The University of Texas at San Antonio

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Randall D. Manteufel is Associate Professor of Mechanical Engineering at The University of
Texas at San Antonio where he has taught since 1997. He received his Ph.D. degree in
Mechanical Engineering from the Massachusetts Institute of Technology in 1991. His teaching
and research interests are in the thermal sciences. He is the faculty advisor for ASHRAE at
UTSA. Manteufel is a fellow of ASME and a registered Professional Engineer (PE) in the state of

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NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

Application of Excel in Psychrometric Analysis


In undergraduate courses in applied thermodynamics or heating, ventilation and air conditioning, mechanical engineering students are introduced to psychrometric principles. Thermal analysis of systems involving dry air and water vapor mixture requires a good understanding of psychrometric concepts and definitions of such parameters as humidity ratio, relative humidity, dew point temperature, and mixture enthalpy. Formulas defining the psychrometric parameters are usually employed in conjunction with property values from the steam tables and ideal gas tables (or equations) in design and analysis of air conditioning systems, cooling towers, and other processes involving the control of water vapor content in the air. Alternatively, psychrometric charts are employed to reduce the time and ease the effort necessary for such analysis. However, human error in reading values off the charts reduces the accuracy of the analysis. In addition, solving open-ended problems usually involves many steps which may require repeated use of psychrometric charts at each step, making the solution process tedious and time consuming.

We have found that Microsoft Excel is a useful tool for teaching students the fundamental psychrometric concepts and its application in solution of problems requiring repeated evaluation of psychrometric parameters or recurring use of psychrometric charts. To reinforce students’ understanding of the fundamental concepts we have designed a series of exercises requiring students to use simple equations available for ideal gases in Excel spreadsheets to evaluate such psychrometric parameters as relative humidity, humidity ratio, dew point temperature, and the enthalpy of air-water vapor mixtures. Goal Seek, or Solver functions of Excel are introduced to aid the solution process for problems requiring iterative processes. This paper provides several examples to demonstrate the effectiveness of Excel in teaching and learning the fundamentals of psychrometric principles and its application in solution of problems requiring the recurring evaluation of psychrometric parameters.


All mechanical engineering degree programs require either a single course consisting of 3-4 semester credit hours (SCH) or a two-course sequence in thermodynamics, each consisting of 3 SCH. The fundamental concepts, including the evaluation of properties using tables or formulas are covered in the early stages of a single required course or in the first course for those programs requiring a two-semester course sequence. At the latter stages of the course coverage, students are introduced to thermodynamics cycles, including the air-standard power and refrigeration cycles. The coverage also includes an introduction to chemical reactions, mixtures of ideal gases, including psychrometric analysis of moist air. The moist air properties are usually obtained from using steam tables in combination with the properties of air.

Many modern thermodynamic textbooks provide a software packages to aid students with property evaluation1-3. Some of these software packages such as Interactive Thermodynamics (IT) or Engineering Equation Solver (EES) have programming capabilities4, 5. These programs are general purpose, non-linear equation solvers with built-in property functions. They are

Karimi, A., & Manteufel, R. (2010, June), Application Of Excel In Psychrometric Analysis Paper presented at 2010 Annual Conference & Exposition, Louisville, Kentucky. 10.18260/1-2--16857

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