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Component Material Balance
Chemical engineers require additional information (apart from the overall material balance) about material flows of components in the process and conduct component material balances over the process units. Let us assume that the process shown in Figure 6.1 is that of simple mixing of a concentrated aqueous solution of salt A (stream 1) with pure water (H2O; stream 2), yielding a…
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Overall Material Balance
Consider an arbitrary process represented by the block flow diagram shown in Figure 6.1. The process unit has two influent flows (streams 1 and 2) feeding into a tank and one effluent flow (stream 3) leaving the tank. Figure 6.1 A simple process unit. Physically, the material being fed to the process must either accumulate in it…
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Quantitative Principles of Material Balance
A chemical process typically consists of several units that may involve chemical reactions and/or simple physical separation and mixing operations, as described in previous chapters. The process streams may be constituted of a single phase (gas/liquid/solid) or may be multiphase in nature. A unit may or may not be operating at steady state. Regardless of the…
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Summary
This chapter presented the elementary principles of fluid flow both qualitatively and quantitatively. Examples of various computation problems were presented. The problems included solution of transcendental equations, regression analysis and interpolation, numerical integration, and numerical differentiation. The solution techniques for the problems were demonstrated using two alternative approaches: a spreadsheet program (Excel) and a computational…
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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…
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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…
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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…
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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…
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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…
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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.