\frac {1}{2} \, v^{2} +
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The mechanical energy equation for a turbine - where power is produced - can be written as: p in / ρ + v in 2 / 2 + g h in = p out / … 0000003900 00000 n
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\left(\frac{\text{work}}{\text{mass}}\right) =
An overall mass balance is a mass balance which models the entire mass of the system, as opposed to the mass of one component of the system. Steady state can only be applied to flow systems, or batch systems in which no changes are taking place. The general balance equation is a fundamental concept of chemical engineering which is based on the principles of conservation of mass and conservation of energy.The general balance equation states that the total or component mass or energy of any system can be modeled by: In - Out + Generation - Consumption = Accumulation The Elements of Chemical Reaction Engineering, Prentice Hall. The general balance equation states that the total or component mass or energy of any system can be modeled by: The equation is used to describe and design almost every process unit within chemical engineering. Thus the general balance equation applied to a batch system is: If the system is at steady state, then the accumulation term is 0. This type of situation is also known as chemical equilibrium. 0000191025 00000 n
• Only ONE energy balance equation is written for any system (or sub-system) irrespective of the number of components in the product(s) Note: Once mass and energy balance equations are written, make sure that the number of equations and number of unknowns are equal. Chemical and Bio-Process Control, Texas Tech … Another way the general balance equation is used is the mole balance, that is, a balance on the number of moles of one component of the system. \frac{W}{\epsilon} =
\left(\frac{P}{\rho} +
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Chemical Process Control: A Time-Domain Approach, The University of Michigan. \left(\frac{P}{\rho} + \frac {1}{2} \, \alpha \, v_{avg}^{2} + g \, z \right)_{1} =
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(\(\alpha=1\)). 0000005609 00000 n
Mathematical formula derived from Eq. 0000189852 00000 n
The general balance equation is a fundamental concept of chemical engineering which is based on the principles of conservation of mass and conservation of energy. g \, z \right)_{2} -
This page was last modified on 13 July 2016, at 13:20. However, mole balances still have advantages over mass balances in some situations (for example, if the flow rates are given in moles per time). You may assume that the velocity adjustment factor is unity
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w_{s} - w_{f}\], \[ \begin{align}\begin{aligned}\text{Power} = \frac{\text{work}}{\text{time}}
Thus the overall balance is shown by: If the system is also at steady state, then the equation reduces to: Note that an overall mass balance can not be performed on a batch system, as all terms would equal 0. <<845EAA49F2A2214AB2A85E904FBD3CC9>]>>
Introduction to Chemical Engineering Processes/Unsteady state energy and mass balances. Riggs, James B.; Karim, M. Nazmul. One of the ways chemical engineers ensure their calculations on linked process units have been performed correctly is to perform a mass balance over the entire system. endstream
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Energy Balances - Leon Grado ... Chemical engineers do a mass balance to account for what happens to each of the compounds used in a chemical process. g \, z \right)_{1} =
From Wikibooks, open books for an open world < Introduction to Chemical Engineering Processes. 0000003466 00000 n
\frac {1}{2} \, v^{2} +
\frac {1}{2} \, v^{2} +
\frac {1}{2} \, v^{2} +
The mass balance for a steady state system is: A batch system is one in which all of the materials of the system are placed into a fixed vessel and left to react for an amount of time. \left(\frac{P}{\rho} + \frac {1}{2} \, \alpha \, v_{avg}^{2} + g \, z \right)_{\text{in}} =
2. 2. 0
w_{s} - w_{f}\], \[\left(\frac{P}{\rho} + \frac {1}{2} \, \alpha \, v_{avg}^{2} + g \, z \right)_{2} -
Mathematics in Chemical Engineering" within 3rd year of study. 0000004944 00000 n
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Unreviewed. g \, (z_{2} - z_{1})= 0\], \[\left(\frac{P}{\rho} + \frac {1}{2} \, \alpha \, v_{avg}^{2} + g \, z \right)_{\text{out}} -
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The same principles used to form mass balances can be used to form mole balances. The balance equation then becomes. {\text{power to operate the pump}}\end{aligned}\end{align} \], \[\text{Power required to operate a pump} =
Chapter 7 A general Strategy for Solving Material Balance Problems The strategy outlined below is designed to focus your attention on the main path rather than the detours: 1. 0000008077 00000 n
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When the general balance equation is applied to the mass of a component or of the entire system, it is called a mass balance. For such a purpose, the general principle of balancing is reduced to the bookkeeping procedure. 0000004059 00000 n
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This page has been accessed 28,890 times. \frac{1}{2} \left(v_{2}^{2} - v_{1}^{2} \right) +
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Since each mole of any given chemical must weigh the same, a mole balance is simply a direct product of the mass balance. \left(\frac{P}{\rho} +
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Read and understand the problem statement This mean read the problem carefully so that you know what is given and what is to be accomplished. https://www.conservapedia.com/index.php?title=General_balance_equation&oldid=1256382. 0000189615 00000 n
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g \, z \right)_{2} -
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g \, z \right)_{1} = 0\], \[\frac{P_{2} - P_{1}}{\rho} +
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\dot m \, w_{s} = \rho \, \dot V \, w_{s}\\\epsilon = \text{Efficiency} = \frac{\text{power delivered to the fluid}}
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Since there is no flow in or out, the in and out terms are both 0. Assuming an efficiency of \(\epsilon = 0.8 \, (80 \text{%})\),
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the internal energy consists of ‘rate of flow’ work only (\(\dot W_{S} = 0\)) Under these conditions, we arrive at the Bernoulli Equation, which is often employed in engineering to relate velocities and pressures in various types of flows. This means that the in, out, generation, and consumption terms are constants, and the accumulation term is 0. What IS accumulation? 0000002938 00000 n
If the system is at steady state then there are no terms which vary over time. 0000008611 00000 n
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The energy equation is often used for incompressible flow problems and is called the Mechanical Energy Equation or the Extended Bernoulli Equation. Jump to navigation Jump to search. \left(\frac{\text{mass}}{\text{time}}\right)
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what size pump (in units of \(\si{hp}\)) would be required? w_{s} - w_{f}\], \[\left(\frac{P}{\rho} +
Since mass can not be created or destroyed, the consumption and generation terms for an overall mass balance are 0. ISBN 0-13-047394-4; Kravaris, Costas. Mass balances are the simplest forms of the general balance equation and one of the first forms a chemical engineer learns. Below is a general description of how to use mass balances for different situations. %PDF-1.6
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\frac{\dot m \, w_{s}}{\epsilon}\], \[ \begin{align}\begin{aligned}\SI{1}{hp} = \SI{550}{ft.lb_{f}/s}\\\SI{1}{hp} = \SI{0.746}{kW}\end{aligned}\end{align} \], generalized form of the conservation of energy equation.