Open system thermodynamic laws applied

Applying the first law and second law of thermodynamics of the open system to each of the four processes of the Carnot vapor cycle yields ... 

The first law of thermodynamics simply says that energy cannot be created or destroyed. With respect to a chemical system, the internal energy changes if energy flows into or out of the system as heat is applied and/or if work is done on or by the system. The work referred to in this case is the PV work defined earlier, and it simply means that the system expands or contracts. The first law of thermodynamics can be modified for processes that take place under constant pressure conditions. Because reactions are generally carried out in open systems in which the pressure is constant, these conditions are of greater interest than constant volume processes. Under constant pressure conditions Equation 3 can be rewritten as... 

No laws of physics or thermodynamics are violated in such open dissipative systems exhibiting increased COP and energy conservation laws are rigorously obeyed. Classical equilibrium thermodynamics does not apply and is permissibly violated. Instead, the thermodynamics of open systems far from thermodynamic equilibrium with their active environment—in this case the active environment-rigorously applies [2-4]. 

For a closed system the first law of thermodynamics has defined an energy function called internal energy U, which is expressed as a function of the temperature, volume, and number of moles of the constituent substances in the system U = u(t, V, n, nc). Furthermore, the second law has defined a state property, called entropy S, of the system, which is also expressed as a function of state variables S =s(T,V,nl---nc). Thermodynamics presumes that the functions t/(r,V,n, " nj and 5(7, y, I nc) exist independent of whether the system is closed or open. The energy functions of U, H, F, and G, then, apply not only to closed systems but also to open systems. 

First of all, we will touch a widely believed misunderstanding about impossibility of using the second law of thermodynamics in the analysis of open systems. Surely, the conclusion on inevitable degradation of isolated systems that follows from the second law of thermodynamics cannot be applied to open systems. And particularly unreasonable is the supposition about thermal death of the Universe that is based on the opinion of its isolation. The entropy production caused by irreversible energy dissipation is, however, positive in any system. Here we have a complete analogy with the first law of thermodynamics. Energy is fully conserved only in the isolated systems. For the open systems the balance equalities include exchange components which can lead to the entropy reduction of these systems at its increase due to internal processes as well. 

In Chap. 2 the first law of thermodynamics was applied to closed systems (nonflo processes) and to single-stream, steady-state flow processes to provide specifi equations of energy conservation for these important applications. Our purpos here is to present a more general equation applicable to an open system or to control volume. 

Thermodynamics of nonequilibrium (irreversible) processes is an extension of classical thermodynamics, mainly to open systems. Unfortunately, the Second Law of classical thermodynamics cannot be applied directly to systems where nonequilibrium (i.e., thermodynamically irreversible) pro cesses occur. For this reason, thermodynamics of nonequilibrium processes has used several principal concepts that are supplementary to the classical thermodynamics postulates. In contrast to the postulates, many of the con cepts in thermodynamics of nonequilibrium processes can be mathe maticaUy substantiated by considering, for example, the time hierarchy of the processes involved. 

The first law of thermodynamics for open systems applies the transport of work dl heat dQ mass dm, with its enthalpy h and external energy (kinetic and potential energy) across the system boundaries equals the change in internal energy dtJ and external energy d a in the system. 

In 2.2 and 2.3 we presented the first and second laws for closed systems. In practice these would apply to such situations as those batch processes in which the amount of material in the system is constant over the period of interest. But many production facilities are operated with material and energy entering and leaving the system. To analyze such situations, we must extend the first and second laws to open systems. The extensions are obtained by straightforward applications of the stuff equations cited in 1.4. We begin by clarifying our notation ( 2.4.1), then we write stuff equations for material ( 2.4.2), for energy ( 2.4.3), and for entropy ( 2.4.4). These three stuff equations are always true and must be satisfied by any process, and therefore they can be used to test whether a proposed process is thermodynamically feasible ( 2.4.5). 

A similar program is used for reacting systems. In 7.4 we extend the combined first and second laws to closed systems xmdergoing chemical reactions, then in 7.5 we show how the combined laws apply to reactions in open systems. In 7.6 we formulate the thermodynamic criterion for identifying reaction equilibria. By presenting... 

In this chapter we formulated the combined first and second laws for closed and open systems, both with and without chemical reactions. We found that each form of the combined laws imposes limitations on the directions and magnitudes of processes particular forms apply to particular kinds of processes and systems. In addition, the combined laws provide the conditions that must be satisfied when all processes are complete and equilibrium has been established. This means that the material in this chapter can serve as the starting point for any thermodynamic analysis. 

The substance contained within a system can be characterized by its properties. These include measured properties of volume, pressure, and temperature. The properties of the gas in Figure 1.1 are labeled as Ti, the temperature at which it exists Pi, its pressure and Vi, its molar volume. The properties of the open system depicted in Figure 1.2 are also labeled, and Psys. In this case, we can characterize the properties of the fluid in the inlet and outlet streams as well, as shown in the figure. Here n represents the molar flow rate into and out of the system. As we develop and apply the laws of thermodynamics, we will learn about other properties for example, internal energy, enthalpy, entropy, and Gibbs energy are all useful thermodynamic properties. 

The chemical and physical changes that occur around us, such as photosynthesis in the leaves of a plant, evaporation of water from a lake, or a reaction in an open beaker in a laboratory, occur under the essentially constant pressure of Earth s atmosphere. These changes can result in the release or absorption of heat and can be accompanied by work done by or on the system. In exploring these changes, we have a number of experimental means to measure the flow of heat into and out of the system, and we therefore focus much of our discussion on what we can learn from the heat flow. (Of course, in order to apply the first law of thermodynamics to these processes, we still need to account for any work that accompanies the process.)... 

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