Basic Thermodynamics ~ J. Pohl © () | www.THERMOspokenhere.com
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This writing attempts be present narrative sections, explanations and rationalizations of concepts, ideas, and methods in brief. Important and subtle meanings are developed in context, embedded in examples. Examples tend to be discrete and to overlap only as
regard to manner of formulation, assuymptions, methods of solution etc. Some 200 examples have been written and ordered; this plan seems practical.
The initial topics and examples are high-school-physics-level in difficulty. Fundamental terms and methods of physics are introduced and developed (as did Newton) by use of vector mathematics and calculus. Required knowledge of vectors is minimal and physical. Regarding calculus, only the very simplest, sweetest part is needed; the derivative and its integral.
This material was organized and written to assist the many students who have difficulty understanding beginning-level Engineering Thermodynamics. Much of the difficulty lies in the transition-of-ideas from physics and calculus to the engineering, system perspective. There are five sections.
These are beginning ideas, a re-acquaintance with geometry, algebra, trig and physics. Newton's very simplest system, the BODY, is considered. Newton's 2nd law to studied anew. What Newton meant requires use of the math he used; vectors, a little calculus and the first-order differential equation. Newton's writings contained much more than conclusions. He established a powerful method for analysis of physical reality.
Newton's Analytic Method, we might call it, comprises the very basis of understanding of mechanics the basis of engineering thermodynamics.
Excerpts of Section 1.0
The ancient Greeks classified matter as solid or fluid with fluids being liquid or gas. Since fluids flow and deform, they can be "contained" but not "pulled." To push a fluid requires a modification of force ~ pressure. When Newton's "f = ma" is applied to a fluid element the hydrostatic equation is obtained. "Ideal Fluid" is a model of fluid which assumes fluids have no friction.
Newton's Second Law of Motion (a vector-differential-equation) describes and predicts events of real physical matter that can be suitably modeled as a BODY. No sooner had Newton written his "Laws" (1687) than others launched efforts to modify and extend them. When the Second Law is scalar-vector multiplied by a differential displacement, the mathematically resulting term is differential kinetic energy being equal to differential work.
When matter under investigations exhibits phase change (as with heat) the nature of their molecules becomes important. A new model is used, matter as a "SUBSTANCE." Phase change of water at one atmosphere is the common case of introduction to phase-change behaviors.
Analysis of existence or event of a substance (thermodynamic system) focuses on three properties, mass, momentum and energy. In the past, Conservation Principles were used. That "place" where conservation happened was the entire universe. Today a system approach is coming to the fore. System configurations of mechanisms and machines as being open, closed, steady, etc are more readily understood than are the "conserved" methods. The system method, might logically be called a method of "Property Equations." Try this approach; it puts things consistently!