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Mathcad Functions For The Thermodynamic Properties Of Moist Air, Ammonia, Propane, And R 22

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2007 Annual Conference & Exposition


Honolulu, Hawaii

Publication Date

June 24, 2007

Start Date

June 24, 2007

End Date

June 27, 2007



Conference Session

Thermodynamics and Fluid Mechanics Instruction

Tagged Division

Mechanical Engineering

Page Count


Page Numbers

12.1040.1 - 12.1040.18



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Paper Authors


Stephen McClain Baylor University

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Stephen T. McClain is an Assistant Professor at the University of Alabama at Birmingham. He received his B.S. in mechanical engineering from The University of Memphis in 1995, and he received his M.S. (1997) and Ph.D. (2002) degrees in mechanical engineering from Mississippi State University. Dr. McClain has taught classes in thermodynamics, fluid mechanics, thermal systems design, convection heat transfer, internal combustion engines, and experimental design and uncertainty analysis.

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Christopher Smitherman University of Alabama-Birmingham

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Christopher B. Smitherman is an undergraduate honors student in mechanical engineering at the University of Alabama at Birmingham. Mr. Smitherman plans to finish his B.S. degree in December 2007 and plans to pursue an MBA after graduation. He is a member of the American Society of Mechanical Engineers, Tau Beta Pi, and Pi Tau Sigma.

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

MathCAD Functions for the Thermodynamics Properties of Moist Air, Ammonia, Propane, and R-22


MathCAD functions were constructed to evaluate the thermodynamic properties of moist air, ammonia, propane, and Refrigerant 22. The functions were constructed to ease the need for time-consuming interpolation using tabularized thermodynamic data while reinforcing the functional representation of traditional thermodynamic property tables. Three examples are provided to demonstrate the use of the functions in an undergraduate applied thermodynamics course. The examples include the analysis of an evaporative cooling system, the analysis of a cascade, reversed-Rankine cycle refrigeration system, and the design of a propane based heat pump system. The examples are presented in their entirety in appendices to demonstrate the report-quality worksheets possible using MathCAD. The efforts described are an extension of earlier efforts to develop a complete set thermodynamic property functions needed to teach an undergraduate applied thermodynamics course. While the function development was directed at the applied thermodynamics course, which is commonly taught early in the undergraduate mechanical engineering curriculum, the functions are excellent tools for upper-level electives such as HVAC, internal combustion engines, thermal systems design, and turbomachinery.


Learning with a combination of a textbook and a software package is a contemporary engineering-thermodynamics pedagogy. Many software tools are available for evaluating thermodynamic properties of engineering fluids. Many of these software tools are proprietary packages sold by textbook publishers, such as “Interactive Thermodynamics: IT” [1]. In fact, finding a thermodynamics text that does not come with a software package is difficult. Some textbooks are now built around using a software or web-based internet package [2]. While many educational software packages are available for evaluating thermodynamic properties, evidence that shows that practicing engineers continue to use these thermodynamic-property software packages after entering the workforce is not readily available.

MathCAD, MatLab, and Engineering Equation Solver (EES) are all powerful computational and analytical packages [3,4,5]. Many schools teach and require the use of a computational tool such as MathCAD, MatLab, or EES [6]. From informal conversations with engineers who learned to use one of these computational tools, many of them continue to use these tools after graduation. Developing extensions or toolkits for software that the students will use after graduation seems more appropriate than developing complete software packages that will only be used by students in an educational environment. Because of the need for thermodynamic property functions for the widely used computational tools, functions were generated to evaluate the thermodynamic properties of water, R-134a, air, and twelve species of the CHON system in MathCAD. Equilibrium functions for eight independent reactions involving species of the CHON system are also included. The function set created provides the minimum number of thermodynamic functions required to teach a two-course sequence in undergraduate engineering thermodynamics.

McClain, S., & Smitherman, C. (2007, June), Mathcad Functions For The Thermodynamic Properties Of Moist Air, Ammonia, Propane, And R 22 Paper presented at 2007 Annual Conference & Exposition, Honolulu, Hawaii. 10.18260/1-2--1924

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