In nozzles why the pressure at inlet is more than outlet and vice-versa for velocity?

Question

Applying Bernoulli's theorem to the steam nozzle,

(p1/density*g)+((v1^2)/(2*g))+z1=(p2/density*g)+((v2^2)/(2*g))+z2........(1)

do we get,

(p1/density*g)-(p2/density*g)=((v2^2)/(2*g))-((v1^2)/(2*g))........(a)

since,
by can celling z1 and z2,

Is z1 always equal to z2 for steam nozzle?

There is another equation similar to the above mentioned equation 1 ie...,
(h1)+((v1^2)/2)+z1*g+Q=(h2)+((v2^2)/2)+z2*g+W.............(2)

In what cases do we apply equation (2)?

plz explain the terms in equation (2).

When to apply equation (2) for steam nozzle?and when to apply equation (1) for steam nozzle?

If equation (a) is true then can we say nozzle converts pressure drop into gain in kinetic energy?

It is said that nozzle converts heat energy into kinetic energy?can u plz explain how is it possible?

These questions keeps on haunting my mind!!
My heartily request is to please answer all or at least few of these questions.
Thanking you!!!!

Answer 1

Your equations display incompletely. I'll try to answer your other questions.
In the outer part of the nozzle (beyond the throat, or minimum-area location) the pressurized gas expands. The shape of the expansion section of the nozzle directs most of the expansion in an axial direction. This produces the velocity increase. Of course the gas cools as it expands, and rockets obtain greater expansion and resulting exhaust velocity when using hotter-burning fuels. See the ref.

Answer 2

Ok, let me give this a shot. Think of it as a car wash. Normal water pressure is 90 psi or less. However, when you apply compressed air at a higher pressure, it increases velocity. If water pressure is less than 90 psi, and you run it to a "gun" with a 150 psi air source, you get a suckion effect. The "vacuum effect", which is at 150 psi, will suck the water out at a much higher rate than 90 psi. That's why your car is cleaner at the car wash.

Answer 3

Just remember that movement represents kinetic energy and pressure represents potential energy. And also that the -total- energy of the system has to remain constant. Then it all makes perfect sense ☺

Doug