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glardner1-Visitor
1-Visitor
May 6, 2010
Question

3D surface plot of function of 2 variables

  • May 6, 2010
  • 19 replies
  • 8880 views
I am trying to plot as a 3D surface a function of two independent variables, but I am struggling to get it to work as I want.

The function calculates power availability (kW) as a function of steam pressure (40-80 bar) and steam temperature (400-500�C).

The function is expressed in the form W(P,T). If I put W in the placeholder on the surface plot, it gives the error message "parameters are out of range". But I do not know how to give units (kW, bar, �C) to the axes. If I enter W(P,T), the error becomes "This value must be an array"

How do I plot this type of function?

Gerard Lardner

19 replies

T
TomGutman1-Visitor
1-Visitor
May 6, 2010
You need to go into the plot properties, quickplot parameters, to set the ranges of the independent variables.
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� � � � Tom Gutman
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GerardLardner10-Marble
10-Marble
May 6, 2010
I did try that, but without success.

It might help if I knew in which order the parameters relate to the axes; also, what is the effect of units - i.e. do the ranges understand �C or bar, or must they follow the SI defaults (K and Pa, for example)?

Thanks,

Gerard Lardner
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TomGutman1-Visitor
1-Visitor
May 6, 2010
The quickplot parameters are in the order in which they are specified in the function. Units are not provided for. I usually have my functions scaled so that the parameters are dimensionless, but I believe that otherwhise they must be specified in base SI units.

You can also use createmesh on the function, and plot the resulting array set. I think units can be used with that.
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� � � � Tom Gutman
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ptc-13682881-Visitor
1-Visitor
May 6, 2010
"How do I plot this type of function ? "
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Attach your work sheet "Save as" version 11 or lower.

jmG
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glardner1-VisitorAuthor
1-Visitor
May 6, 2010
I hadn't attached the file before as it makes use of the WaterSteamPro library. However, since you have asked, here it is.

The basic function is that HP steam passes through a turbine, with MP extraction at about 17 bar and LP exhaust at around 10 bar - lower, if we can persuade our client to modify some other old plant; we would like the LP pressure to be 6 bar or less.

Process heaters for driers heat air in two stages, first using LP steam and then boosting the temperature using the MP steam to achieve a final air temperature of 190�C in one drier and 194�C in the other. Our aim has been to minimise the use of MP steam; an earlier version of this worksheet showed the effect of varying the LP pressure while using constant MP and HP pressures.

Thanks in advance for any assistance you can give.

Regards,

Gerard Lardner
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ptc-13682881-Visitor
1-Visitor
May 6, 2010
On 5/6/2010 11:58:15 AM, Gerard_Lardner wrote:
>I hadn't attached the file
>before as it makes use of the
>WaterSteamPro library.
...
>Gerard Lardner
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This software is proprietary and not included in the work sheet. Your best bet is Valery. However it seems you want to plot the surface of either a square matrix or a rectangular matrix, which in other words means "interpolate", no problem. Attach the data table you want to plot.

jmG



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