compressor and pump curves

7/21/2019 Compressor and Pump Curves

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Compressor and Pump Curves 1

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Compressor and Pump Curves

1999 - AEA Technology plc - All Rights Reserved.

ADV 1_2.pdf


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2 Compressor and Pump Curves

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WorkshopIn this module, compressor and pump curves will be used to model the

behaviour of simulated compressors and pumps. Using curves to

model these unit operations allows HYSYS to accurately simulate actual

plant equipment.

Learning ObjectivesOnce you have completed this module, you will be able to:

Specify and attach head and efficiency curves to compressors

Use single and multiple curves to model compressors

Attach head curves to pumps

Accurately model existing plant equipment with HYSYS

PrerequisitesBefore beginning this module, you need to know how to:

Define and import a fluid package

Add streams and unit operations to the PFD


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Compressor CurvesUsing compressor curves in your HYSYS simulation allows you to

accurately model existing plant equipment. You can determine if an

existing compressor is able to meet the specifications of your process.

Using compressor curves allows HYSYS to calculate heads and

efficiencies that are dependant on the flow rate. If the flow rate through

the compressor is known to be constant, a single flow rate and

efficiency can be supplied. If, however, the flow rate is expected to

change, using a compressor curve will allow HYSYS to calculate new

heads and efficiencies based on the current flow rate.

This results in greater accuracy in the simulation, and allows HYSYS to

more closely model actual plant equipment.

Defining the Fluid Package

Before we begin any simulation in HYSYS, we must first define the

appropriate fluid package.

1. Start a New Case and add a Fluid Package.

2. Select the Sour PREOS package

3. Add the following components: H2O, H2S, CO2, C1, C2, C3, i-C4,and n-C4.


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Installing a Stream1. Add a Material Steam to the PFD with the following data:

In This Cell... Enter...

Name Feed

Temperature 70 oC (160 oF)

Pressure 130 kPa (19 psia)

Molar Flow 500 kgmole/hr (1100 lbmole/hr)

Mole Fraction [H2O] 0.24

Mole Fraction [H2S] 0.07

Mole Fraction [CO2] 0.06

Mole Fraction [C1] 0.04



Mole Fraction [i-C4] 0.08

Mole Fraction [n-C4] 0.15


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Adding the Compressor1. Add a Compressorto the PFD.

2. Enter the following information on the Connectionspage:

3. On the Parameterspage, ensure that the Polytropic and Adiabaticefficiency boxes both read .

These values must read because the efficiencies will be

calculated from the compressor curves, and defining the same value in

two places will alwaysresult in a consistency error.


Inlet Stream Feed

Outlet Stream Outlet

Energy Stream Comp Duty

Compressor button


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4. On the Curvepage, select theAdiabaticradio button in theEfficiencygroup. Press theAdd Curvebutton, and enter the dataas shown here:

5. Close the above view and activate Curve-1 on the Curvespage.Ensure that the Enable Curves box on the Curves page ischecked.

Be sure to use the correct unitsfor the curve.

We do not need to enter acompressor speed because weare only entering one curve.However, multiple curves withdifferent speeds can be used.


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6. The pressure of the outlet stream can be seen on theWork Sheetpage, or you can choose Show Tablewhen object-inspecting theoutlet stream on the PFD. The compressors efficiencies can befound on the Resultspage.

Optional ExerciseIt is desired to have an outlet pressure of300 kPa (44 psia).

Use an Adjust operation with the following information:

What is the Outlet Pressure of the compressor? __________

What is the Adiabatic Efficiency? __________

The Polytropic Efficiency?___________


Adjusted Variable Feed - Molar Flow

Target Variable Outlet - Pressure

Specified Target Value 300 kPa (44 psia)

Step Size 5 kgmole/hr (10 lbmole/hr)

Iterations 50

What is the Molar Flow rate if the Outlet Pressure is set at300 kPa (44 psia)? __________

Can you think of an easier way of doing this? __________

How? __________

Save your case!


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Multiple CurvesTypically, industrial compressors are able to run at multiple speeds

depending on the current demand. HYSYS allows users to enter

multiple compressor curves that each represent a specified speed.

Once the curves are entered, any compressor speed can be specified

and the head and efficiency are calculated automatically.

In this exercise, a Natural Gas compressor will be examined to

determine the outlet pressure of a multi-speed compressor.

1. Begin a new case and import the fluid package Nat-Gas.fpkfrom

the diskette provide with this course.

2. Add a new stream to the PFD with the following data:

3. Add a Compressorto the PFD with this data:

4. Delete the default Adiabatic Efficiency value on theParameterspage. Again, the efficiency will be calculated from the compressorcurves.


Name LP Gas



Molar Flow Rate 1500 kgmole/hr (3300 lbmole/hr)

Comp. Mole Fraction - C1 0.99



Comp. Mole Fraction - N2 0.005

Comp. Mole Fraction - CO2 0.0025


Inlet LP Gas

Outlet HP Gas

Energy Comp Duty


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5. Add the four curves shown below to the compressor. Note thatthe curves have been supplied in Field units. (If you are using SIunits, you must change the Flow and Head units to those shownhere beforeyou enter the curve data).

Note that compressor speedsmust be entered here asmultiple curves are beingused.


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The plots for efficiency andhead versus flow can be seenby pressing the Plot Curvesbutton on the Curvespage.


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6. Ensure that all of the curves are activated, and the Enable Curvesbox is checked. These curves are polytropic curves, therefore thePolytropicradio button must be checked in the Efficiencygroupon the Curves page.

7. On the Curvespage, enter a speed of 11 000 per min.

Optional Exercise

1. Delete the specified compressor speed of 11 000 per minute.

2. Enter a pressure of 5000 kPa (725 psia)for the HP Gasstream.

3. HYSYS will automatically calculate the compressor speed neededto meet this outlet pressure.

What is the pressure of the HP Gas stream? __________

What is the compressor speed needed to achieve thespecified outlet pressure? __________

What are the Adiabatic and Polytropic efficiencies of thecompressor under these conditions? __________

What is the temperature of the HP Gas? __________

Instead of entering all of thecurve data, open the HYSYScase Comp_Shortcut.hsconthe disk supplied with thismodule, and begin on step 6.

Save your case!


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Pump CurvesAs with compressor curves, pump curves are used to allow HYSYS to

accurately model existing pumps. Pump curves allow the pressure rise

across the pump to be dependent on the flow rate of liquid.

The pump curves are entered into HYSYS using a form different than

the form used for compressor curves. With pump curves the

coefficients of an expression, up to the fifth order, are entered into

HYSYS rather than the actual data points.

Defining the Fluid Package

1. Begin a new case and select the Peng RobinsonEOS package.

2. Add the components n-Hexane, n-Heptane, andn-Octane.

Installing a Stream

Add a new stream to the PFD and enter the following information:

The coefficients can beobtained from a spreadsheetprogram capable of nonlinearregression, such as EXCEL, or

may be supplied by the pumpsmanufacturer.


Name LP Mixture



Liquid Volume Flow 500 m3/hr (76,000 BPD)

Comp. Mass Fraction [Hexane] 0.60

Comp. Mass Fraction [Heptane] 0.30

Comp. Mass Fraction [Octane] 0.10


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Adding the Pump1. Add aPumpto the PFD and enter the following information:

2. On the Curvespage, enter the following data:


Inlet LP Mixture

Outlet HP Mixture

Energy Pump Duty

Efficiency (ParametersPage) 75 %

Pump button


Coefficient A 3000

Coefficient B -2.0

Coefficient C -0.005

All Other Coefficients 0

Units for Head m

Flow Basis Act. Vol. Flow

Units for Flow m3/hr


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3. Ensure that theActivate Curvesbox is checked.

4. The pressure of the product stream can be seen on theWorksheettab.

What is the outlet pressure of the pump? __________

The pump sales representative, who supplied the curvedata, guaranteed an outlet pressure of 5000 kPa (725 psia)at the specified flow rate. Should you fill out the purchaseorder? __________

Save your case!

compressor and pump curves

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