Question

Which of the following is the function of draft tube?

(a) Decrease the pressure

(b) Increase the velocity

(c) Maximize kinetic energy

(d) Minimize kinetic energy

The question was asked in my homework.

I want to ask this question from Bioreactor Configurations in portion Reactor Engineering of Bioprocess Engineering

Answer 1

Right option is (c) Maximize kinetic energy

To explain I would say: The draft tube is a conduit which connects the runner exit to the tail race where the water is being finally discharged from the turbine. The primary function of the draft tube is to reduce the velocity of the discharged water to minimize the loss of kinetic energy at the outlet. This draft tube at the end of the turbine increases the pressure of the exiting fluid at the expense of its velocity. This means that the turbine can reduce pressure to a higher extent without fear of back flow from the tail race.