Question

The level of toluene (a flammable hydrocarbon) in a storage tank may fluctuate between 10 and 400 cm from the top of the tank. Since it is impossible to see inside the tank, an open-end manometer with water or mercury as the manometer fluid is to be used to determine the toluene level. One leg of the manometer is attached to the tank 500 cm from the top. A nitrogen blanket at atmospheric pressure is maintained over the tank contents. To atmosphere 500 e Toluene Manoseer luld (H,0 or Hg)
a) When the toluene level in the tank is 150 cm below the top (h=150cm),the manometer fluid level in the open arm is at the height of the point where the manometer connects to the tank. What manometer reading, R (cm), would be observed if the manometer fluid is (i) mercury, (ii) water? Which manometer fluid would you use, and why?
b) Briefly describe how the system would work if the manometer were simply filled with toluene. Give several advantages of using the fluid you chose in Part (a) over using toluene.
(c) What is the purpose of the nitrogen blanket?

Answer 1

Answer:

A. 23.9

B.22.9

C. The levels will be equal

D. Obviously that will be to maintain atmospheric pressure

Explanation:

For mercury the pressure in both tubes at R is same so

P_left = P_right

Thus

=>>>Po + rho_t x g x (5 + R - 1.5) = Po + rho_ m x g x R

rho_t x g x (5 + R - 1.5) = rho_m x g xR

rho_t x (3.5 + R) = rho_m x R

3.5 + R = (rho_m/rho_t) x R

3.5 + R = (13560/867) x R

3.5 + R = 15.64 x R

R x (15.64 - 1) = 3.5

R = 3.5/14.64

= 0.239 m

= 23.9 cm  this is for Mercury

ii)water

similarly,

3.5 + R = (rho_w/rho_t) x R

3.5 + R = (1000/867) x R

3.5 + R = 1.153 x R

R X (1.153 - 1) = 3.5

R = 3.5/0.153

= 22.9m for water