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Question: q2 as an engineer in a chemical factory you are...

Question details

Q2. As an engineer in a chemical factory you are required to choose the
type and size of control valve to be used in the system shown below,
FIGURE 2. A pump is used to pass a chemical through a heat exchanger
and then on to a reactor. The valve is used to throttle the pipe line
connecting the heat exchanger to the reactor.
The sizing of the valve is important as the chemical is part of a sensitive
reaction and inaccurate additions will ruin the entire batch.
The liquid chemical, which has a density of 600 kg/m3, is pumped at 5.5
bar gauge at a nominal rate of 16 litres per second. However the design
must permit the flow rate to vary over the range of 8 to 25 litres per
second. The design must also allow for a pressure loss of 0.7 bar across the
heat exchanger and the pressure in the reactor must be kept at 2.1 bar. It
can be assumed that the flow is turbulent and non-choked.
FIGURE 1

5.5 bar 16Us Control Vahe Heat Exchanger 0.7 bar Reactor 2.1 bar


FIGURE 2
a) Select, giving your reasons, the type of valve you would
recommend from:
Ball / Butterfly / Plug / Globe
b) Suppose the valve you have chosen has the size-KV values shown in
the table below.
i) Use the table to determine the required valve size for a
nominal flow of 16 litres per second.
[you will need to apply Equation 5 from lesson 4-4: π‘žπ‘£ = πΎπ‘£βˆšΞ”π‘
𝑑 ]
ii) Check to see if this valve size is suitable over the range of the
full flow-rate {8 to 25 litres per second} and amend your
sizing if necessary.

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