Mass Balances

Question 1

Degrees of freedom

Answer 1

Subtract equations from unknowns
If zero it’s well defined
1+ is underspecified
1- is overspecified

Question 2

DoF for whole system

Answer 2

Do DoF on each process
Add the DoF from each process together
Subtract the repeated unknown variables
Add double up equations - usually there aren’t any

Question 3

Rejection

Answer 3

Rj = (1 - Cp/Cf) x 100%

How efficient the membrane is at removing salt

Question 4

Recovery

Answer 4

R = Vp/Vf x 100%

How much permeate is produced relative to inlet feed water

Question 5

Mixing points

Answer 5

A mixing point gets its own block diagram

Question 6

Distillation Block Diagram

Answer 6

Optional: Nf, Nl and Nv

Then always mol fraction for compounds in mixture labelled x,y and z

Question 7

Raoults Law

Answer 7

The relationship between the mol fraction of A in the liquid phase and the partial pressure of A in the vapour phase

Pa = xa.pa(T)
So YaPt = Pa = xa.pa(T)

Question 8

Cardiac output

Answer 8

Stroke volume/heart rate

Gives unit of volume/min

Question 9

Tidal volume

Answer 9

Volume of air inhaled during quiet breathing

Question 10

Spirometry

Answer 10

Measurement of volume of inhales and exhales

Cannot measure entire lung capacity, only difference

Question 11

Lungs block diagram

Answer 11

Remember lungs consume O2 as well as exhale a small amount