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Engineering Equation Solver EES Cengel Thermo Iso

Engineering Equation Solver EES Cengel Thermo Iso -

Engineering Equation Solver EES Cengel Thermo Iso

How to Use Engineering Equation Solver (EES) for Thermodynamics Problems

EES (pronounced 'ease') is a general equation-solving program that can numerically solve thousands of coupled non-linear algebraic and differential equations[^1^]. It is widely used by engineers and students for solving thermodynamics problems, especially those involving complex property data and equations of state. In this article, we will show you how to use EES for some common thermodynamics problems based on the textbook "Thermodynamics: An Engineering Approach" by Cengel and Boles[^2^]. We will also introduce some useful features of EES, such as units conversion, uncertainty analysis, and optimization.

Problem 1: Ideal Gas Law

One of the simplest thermodynamics problems is to find the pressure, temperature, or volume of an ideal gas given the other two variables and the number of moles. The ideal gas law relates these variables as follows:

PV = nRT

where P is the pressure, V is the volume, n is the number of moles, R is the universal gas constant, and T is the temperature. To solve this problem using EES, we need to enter the equation and the known values in the Equations window. For example, suppose we want to find the pressure of 2 moles of air at 25ÂC and 0.5 m of volume. We can enter the following in EES:

P*V = n*R*T

n = 2 mol

R = 8.314 J/mol.K

T = 25 C

V = 0.5 m^3

EES will automatically convert the units to be consistent and solve for P. The solution can be viewed in the Solution window or in a formatted table. The result is:

P = 83.4 kPa

Problem 2: Van der Waals Equation of State

For real gases, the ideal gas law may not be accurate enough, especially at high pressures or low temperatures. In such cases, we can use a more realistic equation of state, such as the van der Waals equation:

(P + a/V)(V - b) = RT

where a and b are constants that depend on the type of gas. To use this equation in EES, we need to enter the values of a and b for the gas we are interested in. For example, suppose we want to find the volume of 1 mole of carbon dioxide at 100 kPa and 50ÂC using the van der Waals equation. We can enter the following in EES:

(P + a/V^2)*(V - b) = R*T

P = 100 kPa

R = 8.314 J/mol.K

T = 50 C

n = 1 mol

a = 0.365 Pa.m^6/mol^2

b = 4.27e-5 m^3/mol

EES will solve for V using a numerical method. The result is:

V = 0.0249 m

Problem 3: Steam Tables

Another common thermodynamics problem is to find the properties of water or steam at different states, such as saturated liquid, saturated vapor, superheated vapor, or compressed liquid. These properties include pressure, temperature, specific volume, enthalpy, entropy, and quality. To find these properties using EES, we can use the built-in functions that access the steam tables data. For example, suppose we want to find the enthalpy and entropy of saturated steam at 200 kPa. We can enter the following in EES:

P = 200 kPa

Tsat = Tsat(P) C // function that returns saturation temperature at given pressure

h = hVap(P) kJ/kg // function that returns enthalpy of saturated vapor at given pressure

s = sVap(P) {kJ/kg 248dff8e21


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