Emergence of the engineering sciences: thermodynamics as an example

The engineering sciences arose during the 18th _{and 19}th _{centuries as the product of the political,}

social, economic and intellectual changes brought about by the Industrial Revolution (Channell, 2009). There was a growing realisation that technical knowledge needed to be developed from the practicable, tinkering knowledge that resulted in working artefacts, into something more systematic and theory-based, which could be extended beyond a specific context (Banse & Grunwald, 2009).

Channell (2009) calls the development of thermodynamics “one of the most significant

developments in the emergence of the engineering sciences” (p. 132). Thermodynamics theory resulted from the study of the steam engine, but very early on there was a realisation that the theory did not depend on a particular theoretical conception of heat, “making thermodynamics a true engineering science” (Channell, p. 133). This was soon extended; energy and entropy were recognised as universal concepts applicable beyond heat phenomena to many every-day, scientific and technological events and processes -- from the efficiency of power stations to the evolution of stars; from the cooling down of a cup of coffee to the probabilistic likelihood of events. This represents an interesting shift in the way practical shop floor type knowledge became more general and systematic.

22 The first use of the term “thermodynamic” appears in William Thomson’s (Lord Kelvin) (1849) report on Sadi Carnot’s work to the Edinburgh Royal Society: ”A perfect thermo-dynamic engine of any kind, is a machine by means of which the greatest possible amount of mechanical effect can be obtained from a given thermal agency…. and so to complete the theory of the motive power of heat.” (p. 118, emphasis in the original). There are several aspects of interest here: features of idealisation (the notion of a “perfect” engine), the universalised engine “of any kind”, the normative idea of evaluating the “mechanical effect,” and the concern with the theory of the “motive power of heat”. It is an indication of a shift to a more systematic, theoretical way of thinking about the implications of the operation of steam engines from the shop floor of the industrial workshops.

The Industrial Revolution brought in its wake an urgent demand for more and better sources of power, and therefore an increased interest in improving the steam engines by understanding the principles on which they function. In 1768, Smeaton conducted the first parameter variation studies (a uniquely engineering analytical process, according to Vincenti (1990)) on a model steam engine. By the end of the 18th _{century, Watt was trying to calculate the amount of work}

done by his steam engine, or the ‘duty’ of the engine (Cardwell, 1994), a process that was problematic because of the way in which steam expanded in the engine. One of Watt’s assistants eventually built a meter that recorded the pressure changes throughout the stroke of the engine, leading to the development of pressure-volume diagrams that became a standard feature of thermodynamics.

However, the person who contributed most to understanding the thermodynamic processes at work in steam engines was the French military engineer, Sadi Carnot. His contribution

(Reflexions on the Motive Power of Fire published in 1824) came more than 100 years after the invention of the steam engine launched the Industrial Revolution in Britain. The epistemic purpose for Carnot’s work was the desire for an understanding of the theoretical limits of the performance of a heat engine (Boon & Knuuttila, 2009) – today we would call this the efficiency of the heat engine. In 1824, Carnot wrote, “In spite of the many advances that have been made with the heat-engine… the theory of its operation is rudimentary, and attempts to improve its performance are still made in an almost haphazard way” (1986 [1824], p. 61, as quoted in Boon & Knuuttila, 2009). This is an illustration of how technological developments in many cases lead the scientific understanding of the processes, an example of “technology setting the agenda for scientific research” (McClellan & Dorn, 2006, p. 305).

23 Boon & Knuuttila (2009) point out that, unlike theoretical explanations in the typical ‘pure’ sciences, the engineering science starts from a practical problem5_{, in this case the efficiency of a}

heat-engine. Carnot was the first to think of the steam engine as a heat engine, rather than a pressure engine, as most of his contemporaries saw it and where they focused their attention for improvement (Cardwell, 1994). Carnot’s crucial insight was to set out to understand ‘steam power’: ‘water power’ was well understood at the time, but the behaviour of steam (for example the rapid increase in pressure with an increase in temperature) was not understood in the context of the steam engine at the time. He described a ‘perfect’ heat engine: a set of conditions under which a heat engine functioned at maximum efficiency. ‘Perfection’ (an idealisation) is here conceptualised in terms of the ever-present normative concern of efficiency. Carnot was able to demonstrate that his ideal theoretical cycle was independent of any particular theory of heat (and independent of the properties of any particular working fluid). The knowledge is generalised and extends beyond the immediate practical problem that saw its inception. At the time, Carnot supported a material theory of heat: heat is a caloric fluid that produces work as it flows from a hotter to a colder body. By the 1850s, the material (caloric) theory of heat had been replaced by a mechanical understanding of heat, and Joule (1818 – 1889) argued that heat was converted into work (the notion that both heat and work are different forms of energy came a little later in the work done by Thomson and Rankine). Clausius (1822 – 1888) was able to reconcile the new theory about heat to the growing body of thermodynamics theory by postulating that some of the heat is converted into work, and that the rest of the energy is dissipated at a lower temperature. He introduced the term “entropy” to refer to this dissipated energy, nature’s ‘penalty’ (Lindsay, 1959) for energy transformations. Clausius defined the concept of ‘internal energy’ and formulated the two laws of thermodynamics: the First Law states that the energy in the universe is constant, and the Second Law that the entropy in the universe tends towards a maximum (Massoud, 2005).

On the chemistry front, J. Willard Gibbs (1839 – 1903) made major contributions to

thermodynamics theory in his work on thermodynamic equilibrium, effectively launching the field of physical chemistry in the late 1870s. One of Gibbs’ most important contributions was the move towards a statistical mechanical approach to thermodynamics.

At this point, with the emergence of thermodynamics as an example of an engineering science, I conclude the historical overview. I next turn to the recontextualisation of the knowledge into curricula for educating discipline specialists.

5 _{This is an important distinction, explored further in the following chapter: although engineering science,} as a science, is interested in explaining and understanding, the fundamental purpose (‘telos’) is always response to a perceived human need and a problem.

24