Question

6. A pure copper pipe with inner diameter Di = 12 mm and outer diameter Do-15 mm is surrounded by saturated steam with pressure p 08 bar and convection coefficient h,-7000R. The pipe carries water with a convection coefficient h _ 5000 m2 R. Determine the steam condensation rate (per unit length) around the pipe at the location where the mean water temperature reaches 95°C.

Answer 1

Obtain the properties of water at p=0.08 bar. T = 41.5°C; h=he = 2577 kJ/kg Obtain the properties of pure copper: k = 400 W/mK Calculate the heat transfer rate through the pipe: AT 9= 1 Rcow.out - + 1 Rcond ΔΤ 1 Rcom in 1. "D). 1 hA, 2rkl "WA, - +- AT q= D. +- h (ADL) 2rkl h (TD,L)

AT XL a= 7 - + h (TD.) 20k *h, (ID) (Tm-T) h (nD.)* 2nk *h, (ID) (95 – 41.5) - + 7000x (7x15x10-3) 20 x 400 5000x(7x12x10-3) (95–41.5) L 0.00303+8.87x10- +0.0053 q_ (95 – 41.5) L 0.008418 1 = 6350.45 W/m Calculate the steam condensation rate.

6350.45 = mx 257 m=0.00246 kg/s(per unit length)