Chemical Engineering - Fluid Mechanics - Discussion

Tb/Ta = (Pb/Pa)^1-Cv/Cp

1-Cv/Cp~0.65 for water.

90/15 = (rho*g*h2/rho*g*34)^0.65

h2~8

AT a 90 c temperature water is converted into the vapour phase so the centrifugal pump is used for transfer liquid and also cavitation is generated by a vapour through the impeller. So their fluid transfer capacity is reduced.

So, the Answer is 8.

The pressure due to water should be more than the atmospheric pressure. Until and unless the pressure of water is more than atmosphere pressure pumping is possible.

1. In the first case, at 15 C, the water pressure is almost equal to the atmospheric pressure at 34 feet.

2. In the second case, at 90 C, the water pressure will be lesser than the atmospheric pressure at 34 feet. It means the height should be adjusted in such a way that the atmospheric pressure must equal the water pressure at 90 C.

Find the water pressure data from internet and calculate. As Div and I said, it will be lesser than 34 ft. But, according to my calculations, I got 24 ft. The number is wrong, but, I think, the approach is right.

Due to cavitation in pump suction.

When the water temperature is raised to 90 degrees the vapour pressure of the liquid. Increases so we have to raise NPSH are in order to make liquid pressure equal to or greater than VP of liquid. So we decrease the suction pipe length.

What's the relation?

See the maximum theoretical suction lift for water is at 15 c is 34.

Now at 90 c, The vapour formation is taking place in water so cavitation takes place inside the pump and it lift less than the 34 ft so answer is 8.

Can anyone explain?

Not cleared with the solution. Please explain it.

Please anybody explain it.