Calculate (a) average overall heat transfer coefficient Uo based on the outside tube area;
(b) average water-side heat transfer coefficient hw (assume steamside coefficient at
hs = 11,000 W/(m2 K)), (c) local overall coefficient Ux based on the outside tube area for
each of the 10 sections between temperature stations, and (d) local waterside coefficients
hwx for each of the 10 sections. Plot all items vs. tube length. Tube dimensions: ID = 2 cm,
OD = 2.5 c. Temperature station 1 is at tube entrance and station 11 is at tube exit.
GIVEN
Saturated steam condensing on copper tubing with water flowing within
Steam pressure = 1.35 atm = 136,755 N/m2
Tube length (L) = 2.6 m
Water flow rate mw = 5 kg/h = 0.00139 kg/s
Water temperatures given above as a function of distance along pipe
Tube diameters
Di = 2 cm = 0.02 m
Do = 2.5 cm = 0.025 m
FIND
(a) Average overall heat transfer coefficient based on the outside tube area (Uo)
(b) Average water-side transfer coefficient hw
(c) Local overall coefficient (Ux) for each of the 10 sections
(d) Local water-side coefficient hwx for each of the 10 sections
Plot all items vs. tube length
ASSUMPTIONS
The steam-side heat transfer coefficient hs = 11,000 W/(m2 K)
No scaling resistance
Variation of the specific heat of water is negligible
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Table 13, for saturated steam at 136,755 N/m2: Ts = 107°C
For water at the average temperature of 55°C, the specific heat (cpw) = 4180 J/(kg K)
From Appendix 2, Table 12, the thermal conductivity of copper (k) = 392 W/(m K) at 127°C