Scaling pressure drop to other temperatures

  • #1
freddie_mclair
35
1
TL;DR Summary
I have pressure drop measurements at a certain temperature. How can I scale it to other temperatures?
Hi,
I have some measurements for pressure drop of Helium at room temperature and I would like to scale it to other temperatures. Taking into account that, i) the flow is turbulent, ii) the pressure drop, ##\Delta p##, happens always in the same piping and iii) there is only variation on the temperature of the fluid, woud it be sufficient to do:

##\Delta p_T = \Delta p_{RT} \frac{\rho_{RT}}{\rho_T}##

Where ##\rho## is the density and the subscripts RT is for room temperature and T is for other temperature. I can get ##\rho(T)## from thermodynamic tables.
Thanks!
 

Answers and Replies

  • #2
russ_watters
Mentor
22,065
9,173
I don't understand what you are trying to do. What would scale and why? Can you post a diagram of the system with states labeled?
 
Last edited:
  • #3
22,343
5,210
There is much more required to determine the pressure drop of a gas in a pipe than you may think. And certainly, the effect of density on pressure drop is not the only factor. The outlet pressure and the viscosity of the gas are also parameters. For how to determine the pressure drop in a pipe for a compressible gas, you first need to know how it is done for an incompressible liquid. For how to do all this, see Chapter 7 of Transport Phenomena by Bird, Stewart, and Lightfoot.
 
  • #4
freddie_mclair
35
1
I have measurments of Helium at room temperature across some piping. We have set different mass flows, while always keeping the inlet pressure constant and then we measured the pressure in the outlet. With this we have the pressure drop at different mass flows.
Now, I would like to extrapolate this data to 80K using the pressure drop calculated at room temperature. So, my idea is to do a sort of scaling using the related parameters that change with the temperature, which is the density, and now that I think of it, probably also the mass flow.
 

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