Author: admin
-
Basic Computational Problems
Chemical engineers encounter problems ranging in complexity from simple arithmetic calculations to highly involved ones requiring programming. The following examples present of a few of these problems along with solution techniques using Excel and Mathcad. EXAMPLE 5.1 FRICTION FACTOR FOR PIPE FLOW Calculate the Fanning friction factor using the Nikuradse equation for the flow of…
-
Pressure Drop Across a Flow Conduit
The frictional losses due to the flow of fluids result in a decrease of pressure from the point upstream to the point downstream. In other words, a higher upstream pressure is needed to overcome frictional losses in order to transfer fluid from the point upstream to the point downstream. The pressure drop can be viewed…
-
Reynolds Number
As previously mentioned, the flow regime is laminar at low flow rates. Frictional viscous forces predominate at these flow rates. As the flow rate increases, the orderly laminar arrangement is disrupted and the inertial forces associated with the movement of material begin to predominate. The ratio of these two forces can be related to the…
-
Viscosity
The concept of friction is easily understood for a rigid, solid object. For a solid object to move, it must overcome the resistance from another object in contact with it. A similar situation can be envisioned in the case of a flowing fluid. Consider the velocity profile for laminar flow shown in Figure 5.2. The molecules…
-
Energy Balance for Fluid Flow
The energy balance for systems involving a simple flow of a fluid is characterized by the lack of conversion of chemical, thermal, or any other kind of energy into mechanical energy. Essentially, the resulting mathematical formulation is simply a mechanical energy balance wherein the energy contributions arise from the potential and kinetic energy terms and flow work…
-
Quantitative Analysis of Fluid Flow
As mentioned previously, one of the major responsibilities of a chemical engineer involves determination of power and energy requirements for the flow of fluids. This requires understanding the energy balance for the fluid flow, presented in section 5.2.1.
-
Qualitative Description of Flow in Conduits
Consider a pipe closed at both ends and filled with a liquid. The liquid is composed of a very large number of molecules, each one of which occupies a certain position in the stagnant body of the liquid. The position of the molecule is not completely fixed, as it would be in the case of…
-
Summary
Chemical engineers perform a wide variety of computations ranging from simple arithmetic calculations to solving partial differential equations and simulating entire process plants. Technological advances have enabled engineers to access high-performance computing machines and use advanced software for obtaining solutions rapidly. As envisioned by Leibniz, this has allowed them the freedom from time-consuming, laborious, repetitive computational…
-
Computational Tools—Machines and Software
The two components enabling the computations are the hardware—machines that perform the calculations—and the software—the instructions to run solution algorithms by the machines. Both these components are described in the sections that follow. 4.3.1 Computational Machines A counting frame, or an abacus, is one of the earliest devices and has been used for more than three…
-
Integration
As mentioned previously, numerical computation of an integral is needed when it is not possible to integrate the expression analytically. In other cases, discrete values of the function may be available at various points. Numerical integration of such functions involves summing up the weighted values of the function evaluated or observed at specified points. The fundamental…