Resources for the Resourceful – Roy Dossat and Principles of Refrigeration

I often have been heard to say that I don’t really know that much about engineering, I just know where it is in a book. To some extent, I think that is true for most of us in technical fields. Generally, we develop a pretty good grasp of the fundamentals, but
we learn to supplement that by gathering, organizing and remembering reliable sources for the details that we use to apply the fundamentals in our particular field of endeavor.

For instance, if you do work with duct systems, you undoubtedly know and understand the important fundamental principles behind air flow in duct systems, like the relationship between flow and duct cross section and the relationship between flow and pressure drop. And you probably have a pretty good feel for how these things
interact as duct aspect ratios and shapes change. But few of us could cite from memory the various fitting loss coefficients for the nearly infinite variety of duct fittings out there. Rather, recognizing the need to know, we acquaint ourselves with the
fundamentals cited previously and then consult any one of a number
of recourses like the  ASHRAE duct fitting data base the AMCA
Handbooks
or the United McGill Duct Design Handbook as we work out the details
of a design.

As a result, most engineers develop a fairly extensive library of books, handbooks, papers, articles and these days, software, that they use to help them perform their job. If you are like me and learn by reading a number of different perspectives on a particular topic, you may even have multiple references on a particular subject.

How often you consult any particular item in your personal library is mostly a matter of how often a particular issue comes up. Or occasionally, at least in my case, I will find myself simply wondering about something because of a new insight that
causes me to re-visit a reference to read it from a different perspective.  And again, if you are like me, there will typically be one or two references on a particular topic that stand out because their particular manner of presentation really “connected the dots” for you.

I was recently reminded of one such reference in my library and thought I would mention it here because if you are in the business, you may want to add it to your own library. The book is Principles of Refrigeration by Roy Dossat .

His book aside, Mr. Dossat’s career is both interesting and inspirational. It started with his desire to know more after doing refrigerator repair work with two brothers who worked out of their garage in the mid 1940’s . That led him to enroll at the University of Houston, where he ultimately became a professor. Rumor has it that he got that job because as a student, he asked so many questions that his professor finally said something along the lines of “here, you teach the class and find out why yourself”.

That led to his decision to write a text book because there simply was not one that he felt was adequate for his needs as an instructor. The resulting Principles of Refrigeration, first published in 1961, is currently in it’s 5th edition and still going strong.

Probably the biggest reason I hold Mr. Dossat’s text in high esteem is illustrated by the following two figures which are simply scans of pages in two different books. This first  figure is a portion of the discussion of Entropy from the text book used in my college thermodynamics class.

This second figure is the discussion of Entropy from Principles of Refrigeration.

I realize that the print is fine an maybe not even legible at the scale I had to use to post these images, but even without being able to read the text, I suspect you can see a significant difference between the two explanations.

Specifically, the thermodynamics text is based primarily on using mathematics and calculus to explain the phenomenon while the explanation in Mr. Dossat’s book relies on the written word. For those who want to actually read these pages,  I have them posted on my Google Picasa page as a web album.

Obviously, to be able to usefully apply fundamental principles in engineering and scientific endeavors, one has to be able to deal with the mathematics behind them. But, at least for me, to be able to do that successfully, you have to understand in your head and in your gut, what the mathematics are really saying. And that, in my experience, is the hard part.

What I really appreciate about the way the material is presented in Principles of Refrigeration is that Mr. Dossat is able to provide a very readable and understandable explanation of what the equations and fundamentals behind refrigeration systems mean in practical terms that make sense in the real world. The critical equations and math are also presented, but they are supplemented with a very down to earth explanation, which can be priceless.

For instance, the first time I saw this book and started looking at it (I believe it was in the used book section of Powell’s Technical Books or a similar used book store) I literally thought where was this book when I was struggling to understand and pass thermo? I (and I suspect others) had a really rough time with thermo, especially the concept of entropy.  Hindsight is always 20/20 but I suspect had I obtained a copy of this book back in 1974 and used it to supplement my thermo text book and the lectures from Mr. Flanagan, the light bulb that finally opened the door to my “getting it” might have come on sooner.

Its important you understand that the preceding is not a complaint about the quality of the thermo text book or the instructor. Part of the binding on my copy of
Fundamentals of Classical Thermodynamics
(2nd edition, 1973) has fallen off because I have referred to it so frequently. And my professor, Mr. Flanagan, delivered complex topics in clear lectures supplemented by a generous “open door” policy under-which anyone could drop by his office to ask questions and have them patiently answered if you didn’t understand something in class.

In addition, in my case and I suspect for others, he was a major player in helping someone who thought they were destined to be an airplane mechanic discover that they were also an engineer, opening the door to what I do now and love doing, something I would never have even imagined myself doing back in the early 1970’s.

So, bottom line, if you find yourself at a used bookstore or a garage sale or a book fair, take a few minutes to see if there is a copy of Principles of Refrigeration available. If you are an engineer, you may find it presents a useful and refreshing perspective on the thermodynamic theory you learned in college.

If you are an operator or field person who never took a thermo course but find yourself dealing with machinery based on its principles every day, the book may turn out to be a gold mine by acquainting you with the fundamental theory behind the phenomenon you work with in a very accessible manner.

You may also want to check out the ASHRAE journal article on Roy Dossat that I linked to previously. I think you might find his story and the life he led to be inspiring.

David Sellers
Senior Engineer – Facility Dynamics Engineering

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