Can someone identify what this graph is used for?

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SUMMARY

This discussion focuses on the identification and application of a specific graph used to compare Continuous Stirred Tank Reactors (CSTRs) and Plug Flow Reactors (PFRs) performance for first-order reactions. The graph is identified as a nomogram, which is utilized to represent complex relationships in chemical engineering. Key dimensionless groups discussed include Dd/(vxL), which measures axial dispersion and is the inverse of the Peclet number, and kL/vx, representing the ratio of residence time to characteristic decay time for the reaction. The variables are defined as follows: Dd is the axial dispersion coefficient, vx is the axial velocity, L is the length of the tube, and k is the first-order reaction rate constant.

PREREQUISITES
  • Understanding of first-order chemical reactions
  • Familiarity with reactor types: Continuous Stirred Tank Reactors (CSTRs) and Plug Flow Reactors (PFRs)
  • Knowledge of dimensionless numbers in fluid dynamics
  • Basic concepts of axial dispersion in chemical engineering
NEXT STEPS
  • Research the application of nomograms in chemical engineering
  • Study the Peclet number and its significance in reactor design
  • Explore the mathematical modeling of first-order reactions in tubular reactors
  • Learn about the impact of axial dispersion on reactor performance
USEFUL FOR

Chemical engineers, process engineers, and students studying chemical reaction engineering who are interested in reactor design and performance optimization.

Dong Aleta
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Hi, I was asked by my senior to find out what this graph is and how to use it. No details were given as to where they found it.

I know already that this is used to compare CSTRs and PFRs performance for first order reactions, but I can't deduce what the expressions Dd/(vxL) and kL/vx are for and what the variables represent.

Thanks a lot!

graph.png
 
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jedishrfu said:
In general, these kinds of graphs are called nomograms or nomographs:

https://en.wikipedia.org/wiki/Nomogram

They were popular before the advent of personal computers and calculators.

What this particular one is, I'm not sure but I found this website with a similar chart:

http://slideplayer.com/slide/10044354/
Hey, thanks for the response!

Yeah, I'm familiar with nomographs. I just can't determine what the variables in the graph represent.

But thanks a lot for this information! I really appreciate it!
 
This graph is for a tubular chemical reactor in which there is axial mixing/dispersion. The velocity profile is assumed to be flat. The reaction is assumed to be first order decay. The dimensionless group ##D_d/v_xL## is a measure of the axial dispersion, and is the inverse of the Peclet number. The dimensionless group ##kL/v_x## is the ratio of the residence time in the tube to the characteristic decay time for the reaction.

##D_d## = axial dispersion coefficient
##v_x## = axial velocity
L = length of tube
k = first order reaction rate constant
 
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