Will velocity change for constant mass flow rate process

[Spar10]

Dear Professionals, please help me in below problem
A steam enters a insulated pipe with P1 = 44 barg, Temp = 440deg and leaves at other end with P2 = 36barg (pressure reduced due to friction loss in pipe and mass flow rate (m) = 25kg/s ) what will be the velocity at the other end v2?
if consider h1 + v1²/2 = h2 + v2²/2 ---eq1 (energy balance equation) (considering Q=0 (no heat transfer due to insulation,W=0 (no work ),?PE = 0 (no elevation change))
got h1 from steam table by using P1 and T1 and h2 by using P2 and T2 ( considered T1=T2 due to insulated line)
from eq1 getting v1 equal to v2. Is this correct?

if consider m1 = m2 (mass flow rate equals at both end by considering no mass flow loss)
rho1*v1*A1 = rho2*v2*A2 ---eq2 (same area in inlet and outlet A1=A2)
got rho1(density of steam) from steam table using P1 and T1 and similarly for rho2(P2,T2)
by eq2 getting v1 not equal to v2. Is this correct?

Can any one help which equation is correct?

 

[LittleInch]

Student post?

Also please don't post questions in the FAQ section.

The FA section is for answers not questions. ...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ETSeelye]

The process in the pipe is a no-work expansion(delta h=0). And, since you have insulation and are assuming no heat loss, h2 will equal h1. Do a steam table look-up at p2 and h1 to find the specific volume and temperature at point 2. Then use the mass flow, point 2 specific volume and pipe area to calculate the point 2 velocity. It will increase due to the expansion along the pipe.

 

[Spar10]

Thanks for your replies,

Got your point ETSeelye, h1 = h2 for a process inside a pipe and velocity increasing due to expansion. thank you.

Hi LittleInch, raised request to remove the FAQ, thanks for your information.