Category: ENERGY BALANCE COMPUTATIONS

The principle of the conservation of energy forms the basis of energy balance computations. This chapter presented the different forms of energy of interest in chemical processes and the quantification of the principle of conservation of energy in terms of these forms of energy. The concept of enthalpy and its dependence on temperature was also…

A chemical engineer has to perform a wide variety of energy balance computations for a large number of transformations and processes. These computations require application of the principles discussed in section 7.1. The myriad energy balance computations performed by chemical engineers can very broadly be classified into two types: those involving determination of heat effects in…

The previous discussion should make it clear that it is possible to obtain the values of specific enthalpy of any substance at any temperature. It follows that if a process is carried out at a certain temperature—that is, both the feed and product streams are at that specified temperature—then a certain enthalpy change is associated…

Enthalpy is a measure of the energy (or heat) content of a substance [3]. It is a thermodynamic quantity whose absolute value cannot be determined; however, enthalpy of a substance with respect to its value at some reference conditions can be calculated [4, 5]. The reference state, also called the standard state, is specified in terms of pressure and temperature of…

Consider an arbitrary process represented by the block flow diagram shown in Figure 7.1. Figure 7.1 Energy balance on a process unit; Streams: 1—Inlet, 2—Outlet, 3—Heat, 4—Work. This diagram is similar to the one shown in Figure 6.1 for the material balance, except for the following important differences: First, the streams represent energy flows rather than material flows. The…

Three primary forms of energy are encountered in a chemical process [1]: 1. Kinetic energy (KE)—Energy associated with motion. Kinetic energy of a body of mass m and velocity v is ½mv2. Clearly, a body moving at a higher velocity has higher kinetic energy than one of equal mass but lower velocity. 2. Potential energy (PE)—The energy associated with position. Potential energy of…

Because energy can take several different forms, it is necessary for us to understand the forms that are of primary interest to a chemical engineer. These forms are briefly described in the following section.