- #1

- 12

- 0

## Homework Statement

Steam is passing a pipe that has cold water flowing through. I need to find the change in temperature from when the water enters the pipe to when it leaves the pipe.

## Homework Equations

First i found the total thermal resistance using:

R_total=R_in+R_(f,in)+R_conduction+R_out

Where R_in and h_in is:

R_in=1/(h_in pi D_in L_pipe )

h_in=k_w/D_H Nu

R_(f,in) = 0 due to negligble build up on the pipe

R_conduction is:

R_cond=ln(D_out/D_in )/(2k_m πL_pipe )

R_out is:

R_out=1/(h_out A_(total,out) )

I then put R_total into this formula:

Q=UA= 1/R_total =m ̇Cp(T_out- T_in )_cold

and rearranged for:

(T_out- T_in )_cold=Q/(m ̇C_p )=1/(R_total m ̇Cp)

## The Attempt at a Solution

These are the values that I have either been given or calculated from the above equations. I'm more worried about my method as opposed to the correct value.

Constant / Variable Value Units

D_in 0.032 m

L_pipe 3.68 m

k_w 0.58 -

D_H 0.032 m

μ 855e-06 Ns/m^2

ρ 1000 Kg/m^3

V 20 m/s

Re 60000 -

c_p 4.1818 J/(kgK)

Pr 7.21 -

Nu 8.91 -

n 0.4 -

h_in 161.5 W/(m^2K)

R_in 0.0167 °C/W

D_out 0.035 m

k_m 16 -

R_cond 2.42e-04 °C/W

A_(total,out) 0.002959 m^2

h_out 4455 W/(m^2K)

R_out 0.07586 °C/W

R_total 0.0928 °C/W

Q 10.77 W

m ̇ 0.2 kg/s

THIS GAVE ME A TEMPERATURE DIFFERENCE OF ABOUT 12 DEGREES CELCIUS WHICH SEEMS WAY TOO BIG.

Any help at all would be good, and I'm wide open to criticism. I would really appreciate your help with this as it is going in my undergrad thesis.

Thank you very much,

Brandon