4 replies to this topic

[Alicia Selway]

Hey guys,

I got a problem to complete which requires me to use Aspen. I have Aspen Plus installed and working correctly. This is a part of my project:

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System Parameters
The total length (L) of pipe in the system is 100 ft.. The change in height (Δz) between the inflow point
and the point where the fluid exits the system is 8 ft.
The pipe is copper tubing with an actual internal diameter of 1.0195 inches. Assume that a scale 0.25
mm thick has formed on the internal surfaces. A friction loss factor of KROT=3.0 can be assumed for the
rotameter. Use Aspen to determine the physical properties.

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The pipe system diagram has a number of different types of valves and bends. I'd like to know how I go about calculating the physical properties using Aspen (the friction factor or more). From there on, I can figure out how to solve the rest. Can the K-values for different types of valves and bends also be calculated using Aspen? I can supply more information about the problem and the project pdf is the attachment.

I'd really appreciate if you could point me in the right direction. I am completely new to Aspen.

Thanks again for any help!

Attached Files

•  project 2.PDF   1.65MB   59 downloads

[kkala]

My impression is that your instructor aims through this exercise at your familiarization with frictional pressure drop calculations by hand or spreadsheet. Adequate data has been given for this, K values for fittings can be found in project pdf, as well as how to estimate ΔP for orifices. Aspen will be used only to specify physical properties (density, viscosity) of water or methanol.

Some views that could probably help action to this direction.
1. Relative pipe roughness (e/d)= 0.00965~0.01 (to estimate friction factor, together with Re). Alternatives for e/d=0.02 or e/d=0.005, as well as for d=0.9998 inche (smooth pipe).
2. I would not involve roughness in fitting ΔP, calculated by the velocity head method, since no relevant info is given in project pdf and matter is rather complex. But I would note it as a comment (see an example: Perry, 7th ed, p. 6-17, example 6, ΔP in 90 0 bend, among other matters).

Note: Liquid ΔP is not a strong point of Simulators (unless a specific module is added), according to my experience (only) in Design II. At any case given data indicates intent of hand made (or spreadsheet) calculations, without use of specific software on flow.

[Alicia Selway]

Thank you very much kkala!

Yeah, I was not sure what I was to use Aspen for. I thought I had to create a pipe module which would calculate the friction factor for me.

But I guess I will only be using it for finding the density, viscosity etc. I was just completely new to Aspen and was wondering if anyone knew any good websites/tutorials on how to use it.

Once again, thanks for your help!

[Alicia Selway]

Hey guys! Happy New Year!!!

I got a short question.

I'm working on this project again and was surprised to get K values of around 6 for a Flow Transmitter with Orifice plates (as shown in the attachment).

Is this realistic?

I'm only using the 2nd formula in the image I attached with this post. my B values are .642 and .846.

Thanks again!

Attached Files

•  flowmeter.jpg   90.26KB   22 downloads

Edited by Alicia Selway, 04 January 2010 - 05:45 AM.

[kkala]

I'm working on this project again and was surprised to get K values of around 6 for a Flow Transmitter with Orifice plates (as shown in the attachment).Is this realistic?
I'm only using the 2nd formula in the image I attached with this post. my B values are .642 and .846.

Respond may be late, nevertheless your calculation seems correct.
E.g. for β=.642, Cd=0.61 (assuming Re>30000), C=0.67, Korifice=7.70 (Ref. for C :"Unit Operations of Chem. Eng." by McCabe, Smith, Harriott).

I did not know that orifice head loss coefficient K is given by this formula; but it is not out of ball park (same as ~40% open gate valve).
ΔP for orifices can be taken as 0.2 bar preliminarily, to estimate pump head (having an orifice at discharge), which does not seem far from above.