Question

Liquid kerosene flows through a venturi meter, as shown in fig. p1.36. the pressure of the kerosene in the pipe supports columns of kerosene that differ in height by 12 cm. determine the difference in pressure between points a and b, in kpa. does the pressure increase or decrease as the kerosene flows from point a to point b as the pipe diameter decreases? the atmospheric pressure is 101 kpa, the specific volume of kerosene is 0.00122 m3/kg, and the acceleration of gravity is g 5 9.81 m/s2.

Answer 1

we know
Pa=Patm+dgh+dgl
here Pa is pressure in pipe with higher level of liquid
Patm is atmospheric pressure
d is density
g is gravitational constant
h is height of lower liquid
l is difference is height of higher liquid
So Pb= Patm+dgh
here Pb is pressure lower level pipe
so
Pdiff=Pb-Pa
Pdiff=-dgl
We know
Density of kerosene is the reciprocal of it’s specific volume
so d=1/v=1/0.00122=820kg/m3
as g=9.81 and l=12cm
Pdiff= - 820*9.81*12/100
Pdiff = -965.304 Pa

Negative sign shows pressure decreases as the kerosene flows from point A
to point B as the pipe diameter decreases.