Question

7. A person needs to siphon ethanol from the IBC tank shown in the figure at 40 °C using a hose with constant diameter of 0.5 cm. What is the required h (see figure below) to siphon the ethanol without being worried about cavitation (see Module 1 lecture 1 slides on vapour pressure and cavitation)? (4 marks) 100 90 100 cm 50 30 cm 40 3 30 10 304 Temperature [K] 288 320 336 Vapour pressure of ethanol at different temperatures

Answer 1

From the pressure-temperature diagram for ethanol the vapor pressure at 40 ^oC is approximately 17 kPa = 17,000 Pa.

Now the gauge pressure at the point 3 should be equal to vapor pressure.

$\rho =density =789 kg/m3$

g = 9.8 m/s²

h+0.30 = 17000/(789 x 9.8) = 2.2 m

h = 2.2 - 0.3 = 1.9 m

h = 190 cm.

Here