For which of the following purposes might a Venturi tube be used? ...

[ARLKQ]

For which of the following purposes might a Venturi tube be used? 1. To restore fluid pressure distal to a restricted orifice 2. To help keep entrainment ratios constant with varying flows 3. To make possible entrainment of large volumes of gas
 
  a. 1, 2, and 3
  b. 2 and 3 only
  c. 1 and 2 only
  d. 1 and 3 only

Question 2

According to Poiseuille's law, the pressure needed to drive a fluid through a tube will increase under which of the following conditions?
 
  1. Increased fluid viscosity
  2. Decreased tube length
  3. Decreased rate of flow
  4. Decreased tube radius
  a. 1 and 2
  b. 2, 3, and 4
  c. 1 and 4
  d. 1, 3, and 4

[14vl19]

Answer to Question 1

ANS: A
The Venturi tube, as compared with a simple air injector, provides greater entrainment. Moreover, this design helps keep the percentage of entrained fluid constant, even when the total flow var-ies. A Venturi tube widens just after its jet or nozzle. As long as the angle of dilation is less than 15 degrees, this widening helps restore fluid pressure back toward prejet levels. However, the Venturi tube has one major drawbackany buildup of pressure downstream from the entrain-ment port decreases fluid entrainment.

Answer to Question 2

ANS: C
The difference in pressure required to produce a given flow, under conditions of laminar flow through a smooth tube of fixed size, is defined by Poiseuille's law:
P = 8nl/r4,where P is the driving pressure gradient, n is the viscosity of the fluid, l is the tube length, is the fluid flow, r is the tube radius, and 8 is a constant.

[ARLKQ]

Gracias!

[gcook]

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