Energy balance thermodynamics

This book presents an elementary treatment of the principles of heat transfer. As a text it contains sufficient material for a one-semester course which may be presented at the junior level, or higher, depending on individual course objectives. A background in ordinary differential equations is helpful for proper understanding of the material. Although some familiarity with fluid mechanics will aid in the convection discussions, it is not essential. The concepts of thermodynamic energy balances are also useful in the various analytical developments. 

Steam undergoes a Carnot cycle between temperatures 500 °C and 300 °C. During the isothermal heating step, the steam expands from pressure 50 bar to 30 bar. Determine the states in each of the four corners A, B, C, and D of the cycle (see Figure 4-f ). calculate the thermodynamic energy balances and determine the thermodynamic efficiency of the cycle. 

The contact angles and surface tension are connected via Young s equation, based on the thermodynamic energy balance at a fluid/solid/... 

To apply thermodynamic energy balances (1st law), knowledge of how mechanical work changes the state of the system must be available. As the phase houndary is included, the usual equations have to be revised. Fig. 4.3 depicts the situation for the volume expansion dV of the phase A that is accompanied by a change of the principal radii of curvature from Rj, R2 to (R] + Sz), (Rj + 3z), respectively. 

It should be stressed that although these symmetry considerations may allow one to anticipate barriers on reaction potential energy surfaces, they have nothing to do with the thermodynamic energy differences of such reactions. Symmetry says whether there will be symmetry-imposed barriers above and beyond any thermodynamic energy differences. The enthalpies of formation of reactants and products contain the information about the reaction s overall energy balance. 

The scientific basis of extractive metallurgy is inorganic physical chemistry, mainly chemical thermodynamics and kinetics (see Thermodynamic properties). Metallurgical engineering reties on basic chemical engineering science, material and energy balances, and heat and mass transport. Metallurgical systems, however, are often complex. Scale-up from the bench to the commercial plant is more difficult than for other chemical processes. 

Thermodynamics. The first law of thermodynamics, which states that energy can neither be created nor destroyed, dictates that the total energy entering an industrial plant equals the total of all of the energy that exits. Eeedstock, fuel, and electricity count equally, and a plant should always be able to close its energy balance to within 10%. If the energy balance does not close, there probably is a big opportunity for saving. 

The energy balance for a steady-state steady-flow process resulting from the first law of thermodynamics is... 

Those based on strictly empirical descriptions Mathematical models based on physical and chemical laws (e.g., mass and energy balances, thermodynamics, chemical reaction kinefics) are frequently employed in optimization apphcations. These models are conceptually attractive because a gener model for any system size can be developed before the system is constructed. On the other hand, an empirical model can be devised that simply correlates input-output data without any physiochemical analysis of the process. For... 

The first law of thermodynamics is the basis for material- and energy-balance calculations. Because there is no significant transformation of mass to energy in most manufacturing operations, for a material balance the first law can be reduced to the simplified form ... 

The energy equation of a continuing system can be presented by means of the first law of thermodynamics and the energy balance of a flow system as... 

The basis of the calculation is operation for 1 hour. Necessary data are presented in Table 9.1. The energy balance is based on first law of thermodynamics ... 

Woou.ATT, E. Trans. Inst. Chem. Eng. 24 (1946) 17. Some aspects of chemical engineering thermodynamics with particular reference to the development and use of the steady flow energy balance equations. 

A homogeneous flow basis must be used when thermodynamic equilibrium is assumed. For furtl er simplification it is assumed there will be no reaction occurring in the pipeline. The vapor and liquid contents of the reactor are assumed to be a homogeneous mass as they enter the vent line. The model assumes adiabatic conditions in the vent line and maintains constant stagnation enthalpy for the energy balance. 

During this period of intensive development of unit operations, other classical tools of chemical engineering analysis were introduced or were extensively developed. These included studies of the material and energy balance of processes and fundamental thermodynamic studies of multicomponent systems. 

The kinetic equilibrium constant is estimated from the thermodynamic equilibrium constant using Equation (7.36). The reaction rate is calculated and compositions are marched ahead by one time step. The energy balance is then used to march enthalpy ahead by one step. The energy balance in Chapter 5 used a mass basis for heat capacities and enthalpies. A molar basis is more suitable for the current problem. The molar counterpart of Equation (5.18) is... 

Energy intake is only part of the equation. We can also adjust our energy balance by exercising. Various forms of exercise require different average energy outputs. Exercise involves doing thermodynamic work. The table in the next column Indicates that the amount of work depends on the type of exercise and the amount of mass being displaced. 

Based on the law of conservation of energy, energy balances are a statement of the first law of thermodynamics. The internal energy depends, not only on temperature, but also on the mass of the system and its composition. For that reason, mass balances are almost always a necessary part of energy balancing. 

O. A. Hougen, K. M. Watson, and R. A. Ragatz, Chemical Process Principles, Part I, Material and Energy Balances and Part II, Thermodynamics, Second Edition, Wiley, New York, 1954, 1959. 

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