software prototype documentation

7/30/2019 Software Prototype Documentation

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LINE SIZING FOR LIQUID

Basic principles

Calculation of pressure drop-flow rate relation in liquid lines is simplified by the near

incompressiblity of liquids.

For near isothermal conditions, the fluid viscosity does not change drastically from one end ofpipe run to the other.

Thus, a calculation method that assumes constant properties can be used over lengths of piping.

The calculation methods presented in this section:

1. Assume constant fluid properties

2. Applicable to pipe lengths with relatively constant temperature and no flashing

Momentum equation

General Consideration

When the momentum equation is written for a section of pipe carrying a fluid of constant fluidproperties, the resulting equation

is expressed as:

where:V1 = Upstream fluid velocity, ft/sec

V2 = Downstream velocity, ft/sec

P1 = Upstream pressure, psi

P2 = Downstream pressure, psi

Z1 = Upstream elevation, ftZ2 = downstream elevation, ft

hL = frictional head loss, ft

Y = acceleration of gravity

g = 32.17 ft/sec2

Figure below illustrates the condition for which this equation is written. This equation forms the

basis for pressure drop predictions using the Darcy Equation.


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Bernoulli Equation

When the frictional head loss term is omitted, the momentum equation becomes the bernoulli

equation. The Bernoulli equation was derived through a momentum balance on a frictionless fluid

Units

Each term in the momentum equation has the unit s of feet, which is the form presented incivil

engineerng textbooks and is used for computations in this section

Mechanical and chemical engineering textbooks use and equivalent form in which each term has

the dimensions of pressure.

Analysis of equation terms

Definition of terms

V2 terms represent acceleration effects in the fluidP terms represent pressure gradient effects

Z terms represent elevation effects

hL term represents the frictional pressure drop effect

Velocity term

Since acceleration effects are generally small for steady state flow in piping pressure drop

calculations, the V2 terms are usually ignored.

For a constant diameter pipe with an incompressible fluid, is identical to , and velocity

terms make no net contribution.

Pressure terms

y is the weight density and is expressed in units of , r,where :

where:

Y = weight density, lbf/ft3


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r = mass density, lbm/ft3

g = acceleration gravity, 32.17, ft/sec2

Gc = 32.17 (ft-lbf/lbm sec2)

For all practical situations, g = 32.17 ft/sec2 and there is no numerical distinction between y and

r

The computational convenience of the civil engineering form of the momentum equation arisesfrom the incorporation of the factor

Gc into y, weight density

Darcy and Fanning Equations

The momentum e quation has the frictional effects included in the term, and the methode for

calculating frictional effects is unspecified

Darcy and Fanning equations provide a means of calculating these friction effects.

Coefficient Darcy and Fanning equations can be calculated by Churchil Equation if the flow in

laminar condition and Chen equation if the flow in turbulent conditions.


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Compressor

Compressor is one of the fluid flow operation equipment. The objective of compressor is to

increase the gas stream pressure. Because of many limitation on materials and the shape of

compressor, it is usually used in the compression ratio of 3 to 8 for a centrifugal compressor up

to 12 to 24 for axial compressor.

To select the most satisfactory compression equipment, chemical engineers must consider a

wide variety of type, each of which has peculiar advantages for particular applications. Among the

major factors to be considered are flow rate, head or pressure, temperature linitations, methode of

sealing, method of lubrication, power consumtion serviceability, and cost.

Step in Compressor 0.0.2

1. Selecting Component and Thermodynamic Model

Before you could use the program, you must determine the component(s) will be processed.

Component DataBase for this free software is limited only for 45 components. Beside the

component, user should also select the Thermodynamic model will be used in the calculation.This free software is limited only for 4 model. This Thermodynamic model is used in the

determination of compressibility factor at suction and discharge condition. If user select Ideal

System for it, compressibility factor will be used is one at any condition. The others is used via

Equation Of State (EOS) and depend on Temperature, Pressure, mole fraction, and component's

critical properties.

2. Determination of Component(s)'s Mole Fraction

After component(s) and Thermocynamic model have selected, user must define their fraction on

the stream. User could define this at the end of user specification, but still could not calculate

before component(s)'s mole fraction is defined. If user do not know their composition, but their

molar flow rate (each component), then i t could b e used. Because of mole fraction only

determined if its total is unity, then user must normalize them by click Normalize button.


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3. User Specification Input

The next step of this program is specification of the condition of its operation. They are stream

condition and one of their efficiency (between adiabatic and polytropic). In this step, user couldenter a value for relative density or not. The difference of it is that if user enter a value of stream's

relative density, then program use that value for the determination of specific heat ratio of stream

via Champbell's Generalization(1). If i t is not be entered with a valid value or zero value, then

program automatically left it as blank and use the specific heat capacity of component(s) in

determining that specific heat ratio. the disadvantage of i t is that the program use ideal heat

capacity. Otherwise in the use of relative density on it , Chambell limitize the use of his

generalization for Hydrocarbon Compounds.

In the stream condition frame, program show in a taskbar what phase does the stream because a

compressor could only be used for a vapor phase stream and so if it's show Liquid with a red

color as the background, then user (and the program) could not calculate the operation.

There also a big taskbar available to tell user which part of specification that should be entered. If

the specification do not completed, i ts color will stil l be yellow and if the program could calculate(i.e. all inputs has entered) then its color will be green and it wil l tell you Ready To Calculate.

After calculation has been done, its color will be blue and its word say Solved. User could see

his/her compressor's parameters on the Result's Frame.


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Calculation:

It has been told you about user specification inputs that must be entered and about the

calculation of specific heat ratio. other important parameter on the calculation are:

Duty, which based on the compressibility factor of suction and discharge stream and not be

based on heat content of each streams.

Exponent, which is the ratio of k for adiabatic and n for polytropic. Exponent is required as the

parameter of compression ratio's significancy in the operation.

SCFM (standard cubic feet per minute), which is the standard flow rate of the stream, which onthe condition of 288 Kelvin and 100 kPa. In the user specification input, user could select the unit

of flow rate of the stream. They are ACFD (actual cubic feet per day), ACFM (actual cubic feet per

minute), ACMD (actual cubic meter per day), ACMM (actual cubic meter per minute) and their

standard.

More:

This free software is completed with a curve of only three profiles based on user specifications.

This could be loaded from Tools Menu. As like in the basic process calculation, curves also

could be generated if only user has entered all of inputs required.


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HEATING/COOLING

This software is created only for single phase fluid operation. Its mean you will not able to

calculate heating cooling system with phase change. And for information, this software is

developed with base of calculation:

1. Heat Duty = Heat content of outlet stream - Heat content of inlet stream

2. Heat content is calculated use specific heat capacity

a. For gas, specific heat capacity is calculated using ideal heat capacity

b. For liquids, specific heat capacity is taken from data of "Reklaitis"(see refference)

Equation (1):

Equation (2):

Heat Duty = HTout - HTin

,

3. Phase change Temperature is based on mixture's Saturated Temperature. The saturated

temperature of component is calculated by Lee-Kesler Correlation, and for mixture Kay's Rule

methode is use to calculate pseudocritical.

4.The limitation of software, both of Tout and Tin must greater than 0 K, and Tin must less than

1000 K.

Note:- "Phase is determined based on saturation condition and not based on Vapour-Lquid

Equilibrium".

- "Step for using heating/cooling software similar with compressor"


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Gas-Solid Cyclone

Input Variable

Inputs are parameter when we create a unit process. Input variables that you must enetered are:

1. Feed Gas condition and Parameters

a. Gas inlet velocity (Vc)b. Diameter of particle that 50% removed (Dpc)c. Gas temperatured. Gas pressure

e. Gas density ()

f. Solid density (s)

g. Gas viscosity ()

Note:- The diameter of particle that 50% removed and gas inlet velocity used to calculate width ofrectangular cyclone inlet duct (Bc)

so, if Bc is known another dimension of cyclone will get.- The number gas stream Turn in cyclone (Ne) is optional function. That's mean you can write thevalue or you can leave it and the software will assume it has value 5. But we recomended foryou to give value in this part.

2. Approximation to calculate pressure drop parameter

This part is equation to calculate pressure drop parameter and you must select one. We give you4 optional and there are:a. Lappleb. Stepherd and Lapple


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c. Casal and Martinet-Benetd. ter linden

What result will you get it?

This part show of calculation of the result. You can get the result in:

a. Calculation of result and this show on frame cyclone dimension

b. The cyclone figure with fractional efficiency

This form will show after you write the input and then click show figure .


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and if you click next then form of fractional efficiency will shows.


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System Reporting

In nawapanca we give facilities that can make you print the result in Microsoft Excell. How'screate this?After you find the result then click Report, without opened the microsoft excell.


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Note: 1. If you will print the result you must cl ick Report.2. You can select and change the dimension on Cyclon dimension with click one dimension

you want in Dimension unit (frame of cyclone dimension).


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Line Sizing Two Phase

This software is developed with two commonly used correlation.

1. AGA (American Gas Association) Equation

Basis: - High gas-liquid ratios

- Duckler for frictional component pressure drop

- Flanigan for elevation component at pressure drop

Overall two phase pressure drop

Defined as

Pt = Pf + Pe

Frictional component of pressure drop is

Elevation component of pressure drop is

Calculation procedure

1. Determine the following liquid volume fraction


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2. Determine the mixture viscosity for the Duckler

3. Calculate the superficial liquid velocity

4. Calculate the superficial gas velocity

5. Calculate the mixture velocity

6. Calculate the friction factor ratio

7. Calculate the two-phase mixture density

8. Calculate an estimate for the mixture Reynolds number

9. Determined a better estimate for the Duckler liquid holdup fraction (HLD), using and the

Reynolds number

10. Recalculate the mixture density (k) using the improved estimate of HLD.11. Using this new value of k, recalculate the mixture Reynolds number (Re)

12. Go back to step 9 to determined a new value for HLD. Continue this iterative procedure

until convergence.

13. Calculate the single phase friction factor

14. Calculate the frictional pressure drop

15. Determined the Flanigan liquid hold-up fraction

16. Calculate the elevation component17. Calculate the overall two-phase pressure drop

2. API (American Petroleum Institute)

Basis assumptions: - pressure drop is less than 10% P1- Bubble or mist flow exist- No elevation changes- No irreversiblr energy transfer between phases


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Calculation procedure

1. Determine the following liquid volume fraction

2. Determine the mixture viscosity for the Duckler

3. Calculate the superficial liquid velocity

4. Calculate the superficial gas velocity

5. Calculate the mixture velocity

6. Calculate the two-phase mixture density

m= W/(Qg+QL)

8. Calculate an estimate for the mixture Reynolds number

9. Calculate Darcy friction factor (fn)10. Calculate the frictional pressure drop

11. Determined the Flanigan liquid hold-up fraction

12. Calculate the elevation component

13. Calculate the overall two-phase pressure drop

Where:

Pt = Total two phase pressure drop, psi

Pf = Frictional component of pressure drop, psi

Pe = Elevation component of pressure drop, psi

fn = single friction factorftpr = friction factor ratio

k = two phase mixture density, lb/ft3

Vm = mixture of velocity, ft/sec

Lm = pipeline length, miles

d = pipe inside diameter, inches

Hlf = Flanigan liquid holdup fraction

Ze = sum of vertical elevation rises of pipe

(no elevation drops are considered), ft


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= flowing liquid volume fraction

QL = liquid flow rate at flowing conditions, ft3/secQg = Gas flow rate at flowing conditions, ft3/secn = mixture viscosity, cpL = liquid viscosity, cpg = Gas viscosity, cp

VSL = Superficial liquid velocity, ft/secA = Cross sectional area of pipe, ( d2)/4, ft2.VSg = Superficial gas velocity, ft/sec = -ln ()

= Density of liquid, lb/ft3g = Density of gas, lb/ft3HLD = Duckler liquid holdup fraction

( for the first estimate (assumption))

Re = Mixture Reynolds numberfn = Darcy friction factor


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Line Sizing for Gases

Basic Principles

Calculation of pressure drop-flow rate relations in single-phase gas lines differs from pressure drop

determination in single-phase liquid lines, because of the variation of gas density with pressure

and temperature changes.While liquids are nearly incompressible, the density of gases varies strongly with temperature,

and more imporantly, with pressure.The momentum wquation assumed that fluid density was

constant over the pipe segment under consideration. There are two ways of compensanting for

constant fluid density in the momentum equation:

1. Momentum equation may be applied segmentally over sufficiently short pipe segments, so that

the gas density is effectively constant over each segment. Differ gas densities are applied

in each segment. This approach uses computer where the increased

computational effort of multi-segmental evaluation is not problem.

2. For hand calculations, some closed form integration of an essentially differential momentum

equation is required. If effect elevations are ignored, and real gas behavior law of the

form:

where:P = fluid pressure, psia = fluid density, lbm/ft3Z = Gas compressibility factorR = universal gas constant, 1545 ft-lbf/lb-mole oRT = Fluid temperature, oTM = Molecular weight of gas, lbm/lb-mole

Is assumed, the a closed form integration of the momentum equation is possible. The resultingintegrated form is the basis for each of the several gas flow equations that are discussed

in this section.

Even though each of the gas flow equations are different due to the refinement of the basic gas

equation to different sets of experimental data, they are similar.

Each equation calculates flowline capacity when inlet and outlet pressure are given.

Volumetric flow rates calculated by each of the gas equations are at some standard condition

of pressure and temperature.

Most equations contain an empirical correction factor known as an efficiency factor to permit

adjusment of calculated results with field data.

General Considerations

Assumption:

- Isothermal

- No work is performed

- Steady state conditions

- friction factor (f) is constant

Determining specific volume at upstream conditions


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Rearranging and solving for ,we have:

where:

Qg = Gas flow rate, MMSCFDP1 = upstream pressure, psiaP2 = downstream, psiaS = specific gravity of gasZ = compressibility factor for gasT = gas flowing temperaturefD = Darcy friction factord = pipe inside diameter

The "Z" factor is assumed to be constant but in reality it will change from point 1 to point 2, thus

it is chosen form an average pressure defined as follows:

Approximation of general equation for small pressure drops

This equation yields reasonable results when P1-P2 < 10% of P1

Weymouth Equation

Weymouth's data base consisted of pipes having diameters ranging from 0.8 to 11.8 inchies, thusthe equation is most accurate for pipes having a diameter less than 12 inches. For larger pipe,Weymouth equation becomes increasingly conservative, that is, predictive flow capacitiesbecome increasingly less compared to actual flow capacities.

Assumptions:

- Turbulent flow, high reynolds number exist and- Friction factor is dependent upon relative roughness (/D)

For fixed absolute roughness (), the friction factor was assumed as

Substitution of the above friction value into the general equation for gas yields the Weymouth

Equation.The Weymouth equation is of the form


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where:

Qg = volumetric flow rate, MMSCFDP1 = upstream pressure, psiaP2 = downstream, psiaS = specific gravity of gasZ = compressibility factor for gas

d = pipe inside diameterL = pipeline length, feetT1 = gas flowing temperature, oR

Assuming a temperature of , a gas compressiblity factor of 1.0 and specific gravity of 0.6 equation

reduces to

where:

Qg1 = volumetric flow rate, SCFDLm = pipeline length, miles

Panhandle Eastern Equations

General considerations

Two gas flow equations were developed by Panhandle Eastern for calculating flow rates in large

diameter, 12 inches and above, cross country gas transmission lines.

Panhandle equation that have revised is best used for larger diameter pipes. This equation hasrevised exponents and includes the gas compressiblity factor. It assumes that the friction factorcan be represented by a straight line of constant negative slope (fD=C/Ren) in the moderateReynolds number region of the Darcy Friction Factor diagram.

where:Q = Volumetric gas flow rate, MMSCFDd = pipe inside diameterP1 = upstream pressure, psiaP2 = downstream, psiaLm = pipeline length, milesS = specific gravity of gasZ = compressibility factor for gasT = gas flowing temperatureE = Efficiency factor

= 1.0 for brand new type= 0.95 for good operating conditions= 0.92 for average operating conditions= 0.85 for unfavourable operating conditions

AGA Equation

General considerations

Most contemporary and most accurate of the gas equations in use. Contains several features


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lacking in the earlier gas equations. Contains explicit inclusion of gas compressibilty factoreffects with the "Z" factor being evaluated at effective average pressure in the line segment.Includes an elevation correction factor lacking in the original versions of the other equations.

Includes a transmission factor (F) that is related to the fanning Friction Factor (ff). This factordepends on pipe relative roughness, and for sufficiently low Reynolds number, it includes aReynolds number effect. Its assumes an isothermal flow.

The AGA equations is expressed as

where:

Q = Volumetric gas flow rate, ft3/D @ T0 and P0T0 = Temperature base, oRP0 = Pressure base, psiad = pipe inside diameterP1 = upstream pressure, psiaP2 = downstream, psiaT = gas temperature, oRLm = pipeline length, milesS = specific gravity of gasF = transmission factorEc = elevation correction factorZs = compressibil ity factor

Elevation correction factor(Ec)

where:h1 = elevation of pipeline inlet, fth2 = elevation of pipeline outlet, ft

Compressiblity factor at average conditions (Za)Its determined from average pressure (Pa), fluid flowing temperature() and by use of a generalizedcompressibility chart. Average pressure (T) is determined from the following equation:

Transmission factor (F)For high Rynolds number it is determined from the following equation

For a flow Re less than critical Re, the transmission factor is calculated according to the folowingequation:


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This equation is implicit in and must be solved iteratively.The flow Re is calculated according tothe following equation:

where: = gas viscosity, lbm/ft-sec

While the critical Re is calculated using the following equation

Spitzglass Equation

Modification of general equation that was developed for piping that would operate nearatmospheric pressure. It is derived by making the following assumptions:

a. f = (1 + 3.6/d + 0.03 d) (1/100)

b. T = 520oRc. P1 = 15 psid. P < 10% P1

with the above assumptions, and expressing pressure drop in terms of inches of water, theSpitzglass equationcan be converted to oil filds units.

Substituting P = 0.036 hw; P1=15 psi; and T = 520 oR, we have:

where:

Qg = volumetric flow rate, MMSCFD, at 14.7 psig and 60oF

hw = pressure loss, inches of water

d = pipe inside diameter

S = specific gravity of gas

L = pipeline length, feet

Note:

- specific gravity for air = 1

- For standard conditions P = 14.7 psi and T = 520oR

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