Water at 40ºC with a mass flow of 0.5 kg/s enters a 2.5 cm ID tube whose wall is maintained at a uniform temperature of 90 C. Calculate the tube length required for heating the water to 60ºC and also...

Water at 40ºC with a mass flow of 0.5 kg/s enters a 2.5 cm ID tube whose wall is maintained at a uniform temperature of 90C. Calculate the tube length required for heating the water to 60ºC and also the resulting pressure drop.

Hints: At T_f
=
 = 50C, find the properties of water from the appendix: v, Pr,
,
, c_p, k. From
, find
 and Red. If the flow is turbulent, you may use Sieder–Tait Eq. (4.211). At T_w
= 90C, find

is used to find
. With T_w
= constant, use Eq. (4.188), to fi nd Q_c
=
A(T)
_l.m.

A =
 and L. Find friction factor for turbulent fl ow through a pipe, Eq. (4.206),

  and then
 can be found.

You could also use Dittus–Boelter equation to find
.