 #1
 77
 3
Homework Statement:

Dry saturated steam has pressure of 475 kPa flows at 0.1 kgs through 60m length of insulated pipe diameter 110mm
I) Calc heat loss  ambient temp 20 degrees
II) Calc dryness fraction of steam as it leaves pipe
Temp of dry saturated steam at 475 kPa is 150 degrees, its latent heat condensation is 2114 kJ kg1
The heat transfer coeffecient for lagged pipe is 1.0 W m2 K1
Relevant Equations:

q= UADT
Q=mDh
I) Area = 3.14 x L xD
3.14 x 60 x 0.11
= 20.72m2
Q=UADT
= (1.0Wm2k1)(20.72m2)(15020)
= 2693.6 W
Changed flow rate from 0.1kgs1 to 360kghr1
II) Enthalpic Capacity in dry steam = steam flow rate x latent heat vaporisation
Q=mDh
= 360 x 2114 (formula looks for lat heat vap but we have latent heat condensation?
= 761,040kj
Enthalpic capacity of wet steam = enthalpic capacity in dry steam  heat loss
761,040  2693.6kJ
=758,346.4 kJ
Dryness fraction = enthalpic capacity wet steam / dry steam
758,346 / 761,040 = 0.99kJ
Am I correct here?
3.14 x 60 x 0.11
= 20.72m2
Q=UADT
= (1.0Wm2k1)(20.72m2)(15020)
= 2693.6 W
Changed flow rate from 0.1kgs1 to 360kghr1
II) Enthalpic Capacity in dry steam = steam flow rate x latent heat vaporisation
Q=mDh
= 360 x 2114 (formula looks for lat heat vap but we have latent heat condensation?
= 761,040kj
Enthalpic capacity of wet steam = enthalpic capacity in dry steam  heat loss
761,040  2693.6kJ
=758,346.4 kJ
Dryness fraction = enthalpic capacity wet steam / dry steam
758,346 / 761,040 = 0.99kJ
Am I correct here?
Last edited: