|A visual conception of psychodynamics as conceived by Austrian psychologist Sigmund Freud, as a type of conservation of energy (or force) model of the mind, as outlined in his 1895 “A Project for Scientific Psychology”, a chemical thermodynamics / steam engine stylized psychology, wherein the Helmholtz terms 'bound energy' (repressed energy) and 'unbound energy' (free energy) were first employed in a psychological sense, for the first time, and elaborated on further in his Beyond the Pleasure Principle (1920) and The Ego and the Id (1923), among other publications.|
In 1874, German physiologist Ernst von Brücke—an associate of physicist Hermann von Helmholtz, one of the formulators of the first law of thermodynamics (conservation of energy), both of whom supposing that all living organisms are energy-systems also governed by this principle—gave his Lectures on Physiology, which is said, by some, to mark the initiation of psychodynamics.
Austrian psychologist Sigmund Freud, Brucke's medical school student, in 1874, absorbed some of these Brucke-Helmholtz ideas about energy and thermodynamics. During this year, at the University of Vienna, Brücke served as supervisor for first-year medical student Sigmund Freud who adopted this new "dynamic" physiology. In his Lectures on Physiology, Brücke set forth the radical view that the living organism is a dynamical system to which the laws of chemistry and physics apply.  This was the starting point for Freud's dynamic psychology of the mind and its relation to the unconscious.  The origins of Freud’s basic model, based on the fundamentals of chemistry and physics, according to John Bowlby, stems from Brücke, Meynert, Breuer, Helmholtz, and Herbart. 
English child attachment psychologist John Bowlby (1969), an adamant objector to Frued's “dynamic view of psychology”, defined psychodynamics as:
“[The dynamic view is] propositions concerning psychological energy or psychological forces; concepts such as conservation of energy, entropy, direction and magnitude of forces, [in conjunction with] a principle of inertia.”
In a modern medical sense, psychodynamics is the systematized study and theory of the psychological forces that underlie human behavior, emphasizing the interplay between unconscious and conscious motivation and the functional significance of emotion. 
The second law or entropy aspect of this view, i.e. psychic entropy, was developed later by Freud's associate Carl Jung. 
At the heart of psychological processes, according to Freud, is the ego, which he sees battling with three forces: the id, the super-ego, and the outside world.  Hence, the basic psychodynamic model focuses on the dynamic interactions between the id, ego, and superego.  Psychodynamics, subsequently, attempts to explain or interpret behavior or mental states in terms of innate emotional forces or processes. In his writings about the "engines of human behavior", Freud used the German word Trieb, a word that can be translated into English as either instinct or drive. 
From these early beginnings, by the turn of the century, psychologists around the world were in pursuit of "psychological laws" based on the laws of Energetik.  In Russia, for instance, Krainsky's volume on the "Law of Conservation of Energy applied to Psychical Activity" appeared in 1897. In the decades to follow, energy, according to the doctrine of “Energetics”, was the only enduring reality, being capable of assuming, or transforming itself into, many different modes or species of which consciousness or psychical energy is a part. All mental processes were thus conceived as the interplay of psychical energy with other species of energy. 
In the 1950s, American psychiatrist Eric Berne built on Freud's psychodynamic model, particularly that of the "ego states", to develop a psychology of human interactions called transactional analysis.  Transactional analysis, according to physician James R. Allen, is a "cognitive behavioral approach to treatment and that it is a very effective way of dealing with internal models of self and others as well as other psychodynamic issues."  The theory was popularized in the 1964 book Games People Play, a book that sold five-million copies, giving way to such catch phrases as “Boy, has he got your number” and others.
The etymology of the term "psychodynamics" likely stems from or was influenced in its synthesis and developmental use by the 1860 publication of Elemente der Psychophysik (Elements of Psychophysics) by German physicist and psychologist Gustav Fechner, who coined the term “psychophysics” as the study of the relation between physical stimuli and the intensity of perception of the stimuli.  The term "psychodynamics", however, was not used immediately. Early prototype synonyms include: the "dynamic view" or "mental dynamics" (Freud, 1923), "psychic energism and dynamism" (Jung, 1928), the "psychical energy model" (Bowlby, 1969), "dynamic psychology", or "energy psychology". According to a 1979 translation, psychodynamics refers to the forces, motives, and energy generated by the deepest of human needs. 
The term "psychological thermodynamics", in a modern clarifying sense, as sub-branch of human thermodynamics, is an apt term.
A rare term "psycho-thermodynamics" or psychothermodynamics was coined in about in 1964 by physician Jurgen Ruesch. 
1. (a) Psychodynamics (1874): (1) the psychology of mental or emotional forces or processes developing especially in early childhood and their effects on behavior and mental states; (2) explanation or interpretation, as of behavior or mental states, in terms of mental or emotional forces or processes; (3) motivational forces acting especially at the unconscious level. Source: Merriam-Webster, 2000, CD-ROM, version 2.5.
(b) Thims, Libb. (2007). Human Chemistry (Volume One), (preview), (pgs. 261-64). Morrisville, NC: LuLu.
(c) Thims, Libb. (2007). Human Chemistry (Volume Two), (preview), (section: "Psychodynamics", pgs. 675-77). Morrisville, NC: LuLu.
(d) Freud, Sigmund (1923). The Ego and the Id (pgs. 4-5). W.W. Norton & Company.
(e) Hall, Calvin, S. (1954). A Primer in Freudian Psychology. Meridian Book.
2. Hall, Calvin, S. (1954). A Primer in Freudian Psychology. Meridian Book.
3. Bowlby, John (1999). Attachment and Loss: Vol I, 2nd Ed. (pgs. 13-23). Basic Books.
4. Hall, Calvin S.; Nordby, Vernon J. (1999). A Primer of Jungian Psychology. New York: Meridian.
5. Adams, Henry, and Brooks, Adams. (1910). "A Letter to American Teachers of History", Kessinger Publishing (reprint).
6. McDougall, William. (1932) Body and Mind – A History and a Defense of Animism, 3rd ed.(pg. 130). New York: International Publishers.
7. Berne, Eric (1964). Games People Play – The Basic Hand Book of Transactional Analysis. New York: Ballantine Books.
8. Freud, Sigmund (1923). The Ego and the Id (pgs. 4-5). W.W. Norton & Company.
9. Ahles, Scott, R. (2004). Our Inner World: A Guide to Psychodynamics and Psychotherapy (1-2). John Hopkins University Press.
10. Walsh, Anthony (1991). The Science of Love - Understanding Love and its Effects on Mind and Body. Buffalo, New York: Prometheus Books.
11. Stedman, Thomas Lathrop. (1995). Stedman’s Medical Dictionary, 26th ed. Baltimore, MD: Williams & Wilkins.
12. (a) Freud’s Psycho Dynamic Theory (1873-1923) – Institute of Human Thermodynamics.
(b) Fechner, Gustav T. (1860). Elements of Psychophysics (1966 English ed.). Holt, Rinehart, and Winston.
13. Klimek, David. (1979). Beneath Mate Selection and Marriage – the Unconscious Motives in Human Pairing, (pg. 3). New York: Van Nostrand Reinhold.
14. (a) Ruesch, Jurgen. (1964). “Clinical Science and Communication Theory”, Disorders of Communication: Proceedings of the Association, December 7 and 8 (psycho-thermodynamics, pg. 252). Williams & Wilkins.
(b) Ruesch, Jurgen. (1972). Semiotic Approaches to Human Relations (psycho-thermodynamics, pg. 492). Mouton.
● Psychodynamics – Wikipedia.
● Psychodynamics - McGraw-Hill Science Tech Dictionary.
● Psychodynamics – Microsoft Encarta.