Pump Database

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Navigation: User Guide -> Data Libraries -> Pump Database


The pump/fan curves database SysCAD uses is stored in an MS Access database file called Pumps.mdb located in folder \SysCAD91\BaseFiles. It contains some sample pump curves in the pumps table. The layout for the compressors table is set up but no sample curve is given.

Each of the tables is set up to be used by SysCAD, so care should be taken to keep the design of these tables unchanged. As well, the Pumps.mdb file should always have write access, ie, do not mark this file read-only.

Pumps Table (Pump Curves)

Some sample pump curves are stored in this table located in \SysCAD91\BaseFiles\pumpdb.mdb.

New pump curves can be added to this file for use, the fields for the pumps table will be explained below.

Specification

This is the name of the curve. This will appear in the Pump_GP unit Access Window if the pump database option is selected as the pump equation name. Each pump must have a unique name. SysCAD will search the whole file for the specification name to identify number of curves for each pump. Thus if a pump has a series of curves, it can be grouped by the same specification name.

Control

For a fixed speed pump:

Format: Speed=number, Dimension(engineering units)
Eg: Speed=10
Speed=100, pS(rpm)

SysCAD recognise the keyword speed and will automatically assign it to the pS group with default engineering unit rps. If different units are required, you must assign it to a dimension/unit group with valid engineering units.

For a variable speed pump:

Format: Speed=minimum, maximum
Eg: Speed=5,10.83
Note that values need to be specified in rps.

The fields Speed, MinSpeed, MaxSpeed will be displayed in the pump access window when the pump curve is loaded.

Type

The valid entries are:

Format: Example(s):
Head(L) Head(m)
Press(DP) Press(kPa), Press(Pa)
Isentropic(Enthalpy) Isentropic(Nm/kg)
Adiabatic(L) Adiabatic(m)

SurgePt (m^3/s)

Defines the surge limit. This is also the first valid point in the fan curve.

If nothing is entered in this column, it is assumed 0.

Head (m)

The pump curve data is placed here:

Fixed Pressure Drop equation

Fxd_1(a, b, c, mn1, mx1, mn2, mx2)
y = a.x2 + b.x + c

Variable Pressure drop equation

Var_1(a,b,c,d,e, mn1, mx1, mn2, mx2)
f(a*Qv*Qv + b*Qv + c*Reg*Reg + d*Reg + e)

Use Spline to enter a series of pump curves

TSpline(sig,slp,x1,y1,(optional slp),x2,y2..xn,yn,slp)
Example:
TSpline(Sig=1.0,Slp=0.0,0,53,0.056,52.3,0.111,51.2,0.167,49.8,0.222,47.8,0.278,
45.9,0.333,43.5,0.389,40.8,0.444,37.9,0.5,34.7,0.555,31.4,0.639,25.9,Free)
Let x1, x2 ∙∙∙∙∙∙∙, xn be given real numbers with x1 < x2 < ∙∙∙∙∙∙∙ < xn. A spline function S(x) with knots x1, x2 ∙∙∙∙∙∙∙, xn is a function (defined for all real numbers) consisting of polynomial pieces on each of the sub-intervals (xi, xi+1) for i=0, 1,...,n (where we let x = - ∞ and xn+1 = + ∞), such that the pieces are joined together with certain smoothness conditions.

Sig (0.01 to 100): This determines the smoothness of the fitted curve. The smaller the Sig value, the closer it represents the cubic spline. The larger the Sig value, the tighter it pulls between data points, resulting in a less smooth curve.

Slp (Slope): is the slope of the segment. The curve must have negative slopes. A slope is given at the beginning (must be flat) and at the end of the function. The ending slope can be replaced by free to let SysCAD do the extrapolation.

Data points: Data points must be entered in pairs and must be in increasing flowrate and decreasing pressure delivered. Therefore, enter the values for the highest point of the curve first. (Surge point)

Data points are entered in pairs separated by commas. As a rule, the more data points entered, the smoother the curve will become. However, excel has limit on the maximum number of character allowed in a formula bar, this will in turn become the limit for number of data points allowed in the spline function.

Viewing Of Data Curves

When a valid function has been entered, SysCAD will interpret the points and add in a page called curves for the user to view the curves. From this page, the user can check whether data has been input correctly, that is, check if the slopes and sigma values are entered correctly.

If there are a series of pump curves, SysCAD will try and added in intermediate pump curves estimated from the data sets. These interpolated pump curves will appear in different colours.

Efficiency (%)

To be completed.

Power (kW)

To be completed.

Description

A description of the pump curve can be added. This will not be visible from SysCAD.

Compressor Table (Compressor/Fan Curves)

The format for the Compressors Table is identical to that of the Pumps Table. No sample file is given. The fields for the compressors table will be explained below.

Specification

This is the name of the curve. This will appear in the GasPump_GP unit Access Window if the compressor database option is selected as the equation name. Each compressor/fan must have a unique name. SysCAD will search the whole file for the specification name to identify number of curves for each compressor/fan. Thus if a fan has a series of curves, it can be grouped by the same specification name.

Control

The compressor/fan curve data is placed here:

Format: DisplayTag=number, Dimension(engineering units)
Examples:
Speed=1300, pS(rpm)
Vane=-15, Ang(deg)
Drive=95, Frac(%)

The DisplayTag will be added in the GasPump_GP Access Window when the curve is loaded.

Type

The valid entries are:

Format: Example(s):
Head(L) Head(m)
Press(DP) Press(kPa), Press(Pa)
Isentropic(Enth) Isentropic(Nm/kg)
Adiabatic(L) Adiabatic(m)

SurgePt (m^3/s)

Defines the surge limit. This is also the first valid point in the compressor/fan curve.

If nothing is entered in this column, it is assumed 0.

Head (m)

There are four options to this.

Linear

Linear(a,b,mn,mx)
y = a.x + b

The result can be ranged by the minimum and maximum values entered.

Quadratic

Quadratic(a,b,c,mn,mx)
y = a.x2 + b.x + c

The result can be ranged by the minimum and maximum values entered.

Cubic

Cubic(a,b,c,d,mn,mx)
y = a.x3 + b.x2 + c.x + e

The result can be ranged by the minimum and maximum values entered.

Use Spline to enter a series of compressor/fan curves

TSpline(sig,slp,x1,y1,x2,y2..xn,yn,slp)
Examples:
TSpline(Sig=1.0,Slp=-0.001,13,3000,22.6,2500,27.8,2000,30.5,1500,Slp=-450)
TSpline(Sig=1.0,Slp=-0.001,0.8,0.4,4.58,0.4,5.56,0.4,8.33,0.15,8.77,0.03,Free)
Let x1, x2 ∙∙∙∙∙∙∙, xn be given real numbers with x1 < x2 < ∙∙∙∙∙∙∙ < xn. A spline function S(x) with knots x1, x2 ∙∙∙∙∙∙∙, xn is a function (defined for all real numbers) consisting of polynomial pieces on each of the sub-intervals (xi, xi+1) for i=0, 1,...,n (where we let x = - ∞ and xn+1 = + ∞), such that the pieces are joined together with certain smoothness conditions.

Sig (0.01 to 100): This determines the smoothness of the fitted curve. The smaller the Sig value, the closer it represents the cubic spline. The larger the Sig value, the tighter it pulls between data points, resulting in a less smooth curve.

Slp (Slope): is the slope of the segment. The curve must have negative slopes. A slope is given at the beginning (must be flat) and at the end of the function. The ending slope can be replaced by free to let SysCAD do the extrapolation.

Data points: Data points must be entered in pairs and must be in increasing flowrate and decreasing pressure drops. Therefore, enter the values for the highest point of the curve first. (Surge point)

Data points are entered in pairs separated by commas. As a rule, the more data points entered, the smoother the curve will become. However, excel has limit on the maximum number of character allowed in a formula bar, this will in turn become the limit for number of data points allowed in the spline function.

Viewing Of Data Curves

When a valid function has been entered, SysCAD will interpret the points and add in a page called curves for the user to view the curves. From this page, the user can check whether data has been input correctly, that is, check if the slopes and sigma values are entered correctly.

If there are a series of compressor/fan curves, SysCAD will try and added in intermediate compressor/fan curves estimated from the data sets. These interpolated compressor/fan curves will appear in different colours.

Efficiency (%)

To be completed.

Power (kW)

To be completed.

Description

A description of the compressor/fan curve can be added. This will not be visible from SysCAD.