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5486 results in Thermal-fluids engineering

Page 63 of 275

  • 1 - Introduction

  • William C. Reynolds, Piero Colonna, Technische Universiteit Delft, The Netherlands
  • Book:
    Thermodynamics
    Published online:
    15 June 2019
    Print publication:
    20 September 2018, pp 1-15

  • Summary

    What is Thermodynamics?

    Thermodynamics is the science of energy and its transformations. Engineering thermodynamics is the application of this science in the creation of new technology. It must be understood very well by engineers of all varieties. A basic understanding of thermodynamics can also be an asset to people in fields where the technology is used, such as medicine, and to any lawyer, politician, or citizen who participates in decisions on the appropriate uses of technology. Thermodynamic analysis provides a good model for general analytical thinking.

    Basic principles

    Like any science, thermodynamics rests on a small number of very fundamental principles. The First Law of Thermodynamics is the idea that energy is conserved; this means that the total energy in any isolated region is always the same, although the form of the energy may change. It is one of the two great conservation principles on which all of modern science rests (the other is conservation of momentum). These conservation principles cannot be proven by experiment because the things one measures in an experiment are evaluated by assuming that the principles are true. But by using the basic principles, if necessary inventing new forms of energy to keep energy conserved, or new forces to keep momentum conserved, we can explain the workings of nature and create devices that behave as we predict, and that give support to the theory.

    Microscopic and macroscopic views

    Energy exists at all scales, from the smallest subatomic scale to the grandest scale of the universe. At human scales we sense that fast-moving objects have lots of kinetic energy, and that heavy objects up high, springs wound up, or charged capacitors have lots of potential energy. We also sense that a very hot object has much energy, in modern terminology referred to as internal energy (not heat, which in modern terminology refers to a mechanism of energy transfer and not to energy content). At microscopic scales, internal energy is nothing more than the kinetic and potential energy of the molecules, which we cannot see in detail at our human macroscopic scale. The energy in the electronic bonds that hold molecules together is another form of internal energy.

Page 63 of 275