Download Introduction to Engineering Thermodynamics and more Study notes Thermodynamics in PDF only on Docsity! 10/8/2017 1 Lecture 01 Introduction and Basic Concepts Engineering Thermodynamics CHE 215 University of Anbar 2 • Identify the unique vocabulary associated with thermodynamics through the precise definition of basic concepts to form a sound foundation for the development of the principles of thermodynamics. • Be comfortable with the metric SI and English units.. Objectives of Lecture Note 10/8/2017 2 Introduction to Thermo 3 • Thermal-fluid sciences: The physical sciences that deal with energy and the transfer, transport, and conversion of energy. • Thermal-fluid sciences are studied under the subcategories of Fluid mechanics Thermodynamics Heat transfer The design of many engineering systems, such as this solar hot water system, involves thermal- fluid science. 1.1 Thermodynamics and Energy 4 • Thermodynamics: can be defined the science of energy and entropy. • Energy: The ability to cause changes. • The name thermodynamics stems from the Greek words therme (heat) and dynamis (power). • Conservation of energy principle: During an interaction, energy can change from one form to another but the total amount of energy remains constant. • Energy cannot be created or destroyed. • The first law of thermodynamics: An expression of the conservation of energy principle. • The first law asserts that energy is a thermodynamic property. Energy cannot be created or destroyed; it can only change forms (the first law). Conservation of energy principle for the human body. 10/8/2017 5 Some SI and English Units 9 The SI unit prefixes are used in all branches of engineering. The definition of the force units. Work = Force × Distance 1 J = 1 N∙m 1 cal = 4.1868 J 1 Btu = 1.0551 kJ 10 The relative magnitudes of the force units newton (N), kilogram- force (kgf), and pound-force (lbf). The weight of a unit mass at sea level. A body weighing 60 kgf on earth will weigh only 10 kgf on the moon. W weight m mass g gravitational acceleration 10/8/2017 6 11 All equations must be dimensionally homogeneous. To be dimensionally homogeneous, all the terms in an equation must have the same unit. Dimensional homogeneity 12 Unity Conversion Ratios All nonprimary units (secondary units) can be formed by combinations of primary units. Force units, for example, can be expressed as They can also be expressed more conveniently as unity conversion ratios as Unity conversion ratios are identically equal to 1 and are unitless, and thus such ratios (or their inverses) can be inserted conveniently into any calculation to properly convert units. 10/8/2017 7 13 Always check the units in your calculations!! Every unity conversion ratio (as well as its inverse) is exactly equal to one. Shown here are a few commonly used unity conversion ratios. 14
