Question

Refrigerant-134a enters a 28-cm-diameter pipe steadily at 200 kPa and 20°C with a velocity of 5.5 m/s. The refrigerant gains heat as it flows and leaves the pipe at 180 kPa and 40°C. The specific volumes of R-134a at the inlet and exit are 0.1142 m3/kg and 0.1374 m3/kg. Determine (a) the volume flow rate of the refrigerant at the inlet, (b) the mass flow rate of the refrigerant, and (c) the velocity and volume flow rate at the exit.

Answer 1

(a) The volume flow rate of the refrigerant at the inlet is 0.3078 m3/s

(b) The mass flow rate of the refrigerant is 2.695 kg/s

(c) The velocity and volume flow rate at the exit is 6.017 m/s

Step-by-step explanation:

According to the given data we have the following:

diameter of the pipe=d=28 cm=0.28 m

inlet pressure P1=200 kPa

inlet temperature T1=20°C

inlet velocity V1=5.5 m/s

Exit pressure P2=180 kPa

Exit Temperature T2=40°C

a. To calculate the volume flow rate of the refrigerant at the inlet we would have to use the following formula:

V1=AV1

=π/4(0.28∧2)5

V1=0.3078 m3/s

b. To calculate the mass flow rate of the refrigerant we would have to use the following formula:

m=p1 V1

m=V1/v1

=0.3078/0.11418

=2.695 kg/s

c. To calculate the velocity and volume flow rate at the exit we would have to use the following formula:

m=m1=m2

V1/v1=V2/v2

V2=(v2/v1)v1

=(0.13741/0.11418)5

=6.017 m/s