Refrigerant 134a flows at steady state through a horizontal pipe having an insid

ID: 1812412 • Letter: R

Question

Refrigerant 134a flows at steady state through a horizontal pipe having an inside diameter of 4cm

entering as a saturated vapor at - 8 C with a mass flow rate of 17 kg/min At the exit of the pipe the

superheated vapor exits at 2 bars. Q pipe=3.4 kW

This is hw problem 4.29 7th edition

a)What is the exit temperature of the gas in C and what is the exit velocity? T2 and V2 are shown

above.?

b)Draw a sketch of the process on a T-v phase plane and explain physically how

the exit velocity can be significantly greater than the fluid velocity at the inlet if the mass flow rate

at the outlet equals the mass flow rate at the inlet and the pipe diameter is constant?

For Interactive Thermodynamics

T1 = -8//C

p1 = Psat_T("R134A",T1)

x1=1

Qdot=3.4 //kW

Wdot=0

mdot=17/60 // kg/s

p2=2

d1=.04

d2=d1

A1=(22/7)*((d1)^2)/4

A2=(22/7)*((d2)^2)/4

mdot1=(A1*Vel1)/vsat1

mdot2=(A2*Vel2)/Vel2

// Mass balance

0=mdot1-mdot2

mdot=mdot1

// Energy balance

0=Qdot-Wdot+mdot*((hsat1-h2)+(Vel1^2/2-Vel2^2/2))

hsat1=hsat_Px("R134A",p1,x1)

h2=h_PT("R134A",p2,T2)

v2=v_PT("R134A",p2,T2)

vsat1=vsat_Px("R134A",p1,x1)

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