Can Mass Fractions be Determined from Given Mass Flow Rates?

Click For Summary

Discussion Overview

The discussion revolves around the determination of mass fractions from given mass flow rates of two chemical species in a simulation context. Participants explore the relationship between mass flow rates and mass fractions, particularly in the context of calculating bulk velocity for a fluid mixture.

Discussion Character

  • Homework-related
  • Conceptual clarification

Main Points Raised

  • One participant states the need to compute bulk velocity using a mass-weighted average but expresses uncertainty about how to do this without knowing the mass fractions.
  • Another participant questions the initial assumption that mass fractions are unknown.
  • A later reply suggests that mass fractions can indeed be determined using the formulas (m1_dot)/(m1_dot+m2_dot) and (m2_dot)/(m1_dot+m2_dot), indicating a potential method for calculation.
  • There is a reiteration of the suggestion regarding the determination of mass fractions, with one participant expressing initial doubt about the validity of this approach.

Areas of Agreement / Disagreement

Participants appear to have differing views on the initial assumption of not knowing the mass fractions, but there is a suggestion that mass fractions can be calculated from the provided mass flow rates. The discussion remains somewhat unresolved regarding the initial uncertainty.

Contextual Notes

The discussion does not clarify the assumptions underlying the calculation of mass fractions or the conditions under which the proposed formulas are applicable.

pyroknife
Messages
611
Reaction score
4

Homework Statement


I'm running a simulation and was given 2 mass flow rates (let's say m1_dot and m2_dot) for 2 chemical species at the inlet.

Homework Equations


mass flow rate = density*velocity * area

The Attempt at a Solution


I need to compute the bulk velocity for the fluid (consisting of the 2 species), so it needs to be some mass-weighted average that I'm computing, but how can I do this when I don't know the mass fractions?
 
Physics news on Phys.org
Please explain why you think you don't know the mass fractions.
 
Chestermiller said:
Please explain why you think you don't know the mass fractions.
Wait, can the mass fractions be determined from (m1_dot)/(m1_dot+m2_dot) and (m2_dot)/(m1_dot+m2_dot)?
FOr some reason, I didn't think that would work.
 
pyroknife said:
Wait, can the mass fractions be determined from (m1_dot)/(m1_dot+m2_dot) and (m2_dot)/(m1_dot+m2_dot)?
FOr some reason, I didn't think that would work.
Sure.
 

Similar threads

  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 18 ·
Replies
18
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 13 ·
Replies
13
Views
11K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
1
Views
6K