Mechanical Engineering - Steam Nozzles and Turbines - Discussion


A nozzle is said to be a convergent nozzle

[A]. when the cross-section of the nozzle increases continuously from entrance to exit
[B]. when the cross-section of the nozzle decreases continuously from entrance to exit
[C]. when the cross-section of the nozzle first decreases from entrance to throat and then increases from its throat to exit
[D]. none of the above

Answer: Option B


No answer description available for this question.

Salman said: (Sep 18, 2013)  
Convergent as name implies decrease in size mainly by cross section So, Answer is B. This shape is mainly used to decrease pressure and conversely increasing velocity.

Yogesh H B said: (Nov 15, 2013)  
I disagree with a @Salman statement because decrease in cross section will increases the pressure and velocity also increases.

Nkcool said: (Nov 24, 2013)  
When area increase than pressure decrease.

Sudha said: (Nov 27, 2013)  
When area decreases pressure will decreases, then fluid velocity become increses.

Suresh Kumawat said: (Dec 29, 2013)  
When area decrease pressure will also decrease, but velocity will increase.

Sarif Anwar said: (Mar 16, 2014)  
When exit area of nozzle decrease then velocity energy increase.

Mohan said: (Nov 28, 2014)  
Nozzles are 3 types:

1) Convergent type.
2) Divergent type.
3) Convergent-Divergent type.

Pankaj Das said: (Dec 29, 2014)  
Because its cross section area of tube gradually decreases from entrance to the throat. Venturimeter is a good example of convergent nozzle.

Saikumar said: (Mar 12, 2015)  
The pressure drops in a convergent nozzle because of the Bernoulli Principle.

A nozzle is a spout on the end of a hose or pipe used to control the movement of a fluid like water or air. A convergent nozzle is a nozzle that starts big and gets smaller-a decrease in cross-sectional area. As a fluid enters the smaller cross-section, it has to speed up due to the conservation of mass. To maintain a constant amount of fluid moving through the restricted portion of the nozzle, the fluid must move faster.

The energy to make this fluid speed up has to come from somewhere. Some energy is in the random motion of molecules, which we observe as pressure. The energy in this random motion is converted into faster forward motion, known as stream flow. This change makes the pressure drop.

Pressure is inversely proportional to area, if everything else stays the same. In this case, the energy that causes pressure is converted to another type of energy, so both pressure and area decrease.

Surya said: (Jan 5, 2016)  
Convergence means gradually decrease area of flow line. That means answer should be B.

Ind said: (Mar 17, 2016)  
Convergent Nozzle means decrease in cross-section gradually from entrance to exit.

Which is increase in cross section gradually from entrance to exit is called Divergent Nozzle.

Arun said: (Sep 10, 2016)  
The area increase then the pressure decrease.

Srinivasan said: (Nov 10, 2016)  
You explanation is very correct & good @Saikumar.

Audut Hattale said: (Oct 10, 2018)  
Convergent Nozzle means decrease in cross-section gradually from entrance to exit.

Kamlesh said: (Jan 4, 2019)  
Well said, Thanks @Saikumar.

Vivek said: (Mar 3, 2019)  
Well said, Thanks @Ssaikumar.

Chakri said: (Apr 1, 2020)  
If pressure decreases then what about the velocity in the convergent nozzle?

Imroz Alam said: (Aug 14, 2021)  
Well said thanks @Imroz Alam.

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