Flowrate (Q) Pressure (P) Temperature (T) Viscosity (μ) Pipe Length (L) Internal Diameter (Di) External Diameter (Do) Thickness Insulation (x) Outside Pipe Temperature (T) C. Steel Thermal Conductivity (k) Wet Polyurathene Thermal Conductivity (k) Air coeficient heat transfer @ 20 oC (hair)

= 925.0 = 4.50 = 150.0 = .014 = 120.0 = 193.675 = 219.075 = 50.0 = 40.0 = 50.0 = .40 = 3.0

Saturated Steam 13.8 m3/hr P = 4.5 kg/cm2g T = 150 oC

Wet Polyurethane 50 mm thickness K = 0.4 W/m/C

kg/hr 2 kg/cm o C cP = 14.0E-6 kg/m.s m mm mm mm o C (asumption outside pipe temperature) W/m/C W/m/C 2 o W/m . C Carbon Steel Pipe 8" Sch 80 120 m Length ID = 193.675 mm OD = 219.075 mm K = 50 W/m/C

Heat Transfer (q) based on Fourier Law can be determined by below equation.

q=

2πL(T1 − T3 ) r r ln ⎛⎜ 2 ⎞⎟ ln ⎛⎜ 3 ⎞⎟ ⎝ r1 ⎠ + ⎝ r2 ⎠ k CS kP and the heat loss per unit length of pipe can be calculated based on this equation.

q L

=

q/L =

2π (T1 − T3 ) r r ln ⎛⎜ 2 ⎞⎟ ln ⎛⎜ 3 ⎞⎟ ⎝ r1 ⎠ + ⎝ r2 ⎠ k CS kP 1,338.389 W/m

Since the pipe has length of 120 m, the total heat loss is: ql =

160,606.687 W 548,379.639 Btu/hr

Molar flowrate for 925 kg/hr saturated steam is: Q=

925 kg/hr 2039.276 lb/hr 113.198 lbmole/hr

o

2

Latent Heat (h) of saturated steam 150 C @ 4.5 kg/cm g is 16,371.57 Btu/lbmole. So total steam energy which is entering the pipe is: qt = Qh 1,853,231.074 Btu/hr Therefore, total steam condensate (QSC) which is will be performed inside the pipe can be calculated. ql = QSCh 548,379.639 = 16,371.57QSC QSC =

33.50 lbmole/hr 603.431 lb/hr 273.712 kg/hr

Recommendation Since thickness of insulation is only 50 mm, therefore heat loss to environment is quite big. The critical thickness of insulation can be calculated based on below equation :

rc = rc =

kP hair 0.133333333 m 133.3333333 mm

So insulation thickness shall be minimum of 134 mm for maintening heat loss to environment or change the insulation with dry polyurathane (k = 0.04 W/m/C).