-Second law of thermodynamics The second law of thermodynamics has several forms of expression. One of them states that no heat engine is capable of completely converting all the energy it absorbs into usable work (Kelvin-Planck formulation). Another way of stating it is to say that real processes occur in such a sense that the quality of energy is lower because entropy tends to increase. -Equation of the second law of thermodynamics A heat engine transforms heat energy into work by continuously cycling . In them there is no variation of internal energy, Δ U= 0 Since T 1 > T 2, heat flows spontaneously from the source to the sink. The machine transforms part of this heat into work, and the rest flows to the sump. There is no variation in the internal energy of the machine resulting in: Δ U= 0 ⇒ |Q1| = | W| + |Q2| Where we have used the absolute value to be consistent with any of the usual sign criteria. Note that, under optimal conditions: | W| = |Q1| - |Q2| ⇒ | W| < |Q1| In other words, not all the heat absorbed by the machine is transformed into work. Thermodynamics Gutierrez Josue Miguel Rodriguez 200154 MECATRONICA -Segunda law of thermodynamics in open and closed systems Open Entropy Second law of thermodynamics: in any cyclic process, entropy will increase, or remain the same. Entropy: It is a state variable whose change is defined by a reversible process in T, and where Q is the absorbed heat. Entropy: a measure of the amount of energy that is not available to perform work. Entropy: a measure of the disorder of a system. Entropy: a measure of the multiplicity of a system. Since entropy gives information about the evolution in time of an isolated system, it is said to give us the direction of the "arrow of time". If snapshots of a system at two different times show one that is more disordered, then it can be deduced that this state occurred later in time than the other. In an isolated system, the natural course of events leads the system to a greater disorder (higher entropy) of its state. Closed The refrigerador Second law of thermodynamics: It is not possible for heat to flow from a cold body to a hotter body, without the need to produce any work that generates this flow. Energy does not flow spontaneously from an object at a low temperature,to another object at a highertemperature. This is opposed to the perfect refrigerator. Statements about refrigerators apply to air conditioners and heat pumps,which embody the same principles. This is the "second way," or Clausius' statement of the second law. Thermodynamics Gutierrez Josue Miguel Rodriguez 200154 MECATRONICA It is important to note that when it is stated that energy will not flow spontaneously from a cold object to a hot object, that statement refers to the net transfer of energy. Energy can be transferred from a cold object to a hot object either by transfer of energetic particles or electromagnetic radiation, but the net transfer will be from the hot object to the cold object in any spontaneous process. Work is required to transfer energy to a hot object. -Carnot Cycle The Carnot cycle is a thermodynamic cycle that occurs in an equipment or machine when it works by absorbing an amount of heat Q 1 from a higher temperature source and transferring a heat Q 2 to the lower temperature one, producing work on the outside. The performance of this cycle is defined by n= 1− T2 T1 and, as will be seen later, it is greater than that produced by any machine that works cyclically between the same temperature sources. A heat engine that performs this cycle is called a Carnot engine . -Thermodynamic systems A thermodynamic system is a part of the physical universe with a specific limit for observation. This limit can be defined by real or imaginary walls. A system contains what is called an object of study. An object of study is a substance with a large number of molecules or atoms. This object is formed by a geometric volume of macroscopic dimensions subjected to controlled experimental conditions. A thermodynamic system can undergo internal transformations and exchange energy and / or matter with the external environment. Definition of thermodynamic system Thermodynamics Gutierrez Josue Miguel Rodriguez 200154 MECATRONICA A thermodynamic system is defined as a quantity of matter or a region in space on which attention is concentrated in the analysis of a problem. Everything that is part of the exterior of the system is called environment or environment. The system is separated from the environment by the system boundary. -Aesthetic It is the part of physics that studies forces in equilibrium. If no forces act on a body or several forces whose resultant is zero, we say that the body is in equilibrium. If a body is in equilibrium, it means that it is at rest or is moving in a straight line with constant speed. -Fluid dynamics Fluid dynamics studies the laws of fluid motion, the forces involved in such motion and their interaction with solid bodies. ... Viscous flow is the study of real flow, since viscous forces are produced by taking into account the viscosity of the fluid. Thermodynamics Gutierrez Josue Miguel Rodriguez 200154 MECATRONICA