Reconsider Prob. 5–49. Using EES (or other) software, investigate the effects of the steam temperature and the outer heat transfer coefficient on the flange tip temperature and the rate of heat transfer from the exposed surfaces of the flange. Let the steam temperature vary from 150°C to 300°C and the heat transfer coefficient from 15 W/m² · K to 60 W/m² · K. Plot the flange tip temperature and the heat transfer rate as functions of steam temperature and heat transfer coefficient, and discuss the results.

Data from problem 49

Two 3-m-long and 0.4-cm-thick cast iron (k = 52 W/m · K, ε = 0.8) steam pipes of outer diameter 10 cm are connected to each other through two 1-cm-thick flanges of outer diameter 20 cm. The steam flows inside the pipe at an average temperature of 200°C with a heat transfer coefficient of 180 W/m² · K. The outer surface of the pipe is exposed to convection with ambient air at 8°C with a heat transfer coefficient of 25 W/m² · K as well as radiation with the surrounding surfaces at an average temperature of T_surr = 290 K. Assuming steady one-dimensional heat conduction along the flanges and taking the nodal spacing to be 1 cm along the flange 

(a) Obtain the finite difference formulation for all nodes,

(b) Determine the temperature at the tip of the flange by solving those equations,

(c) Determine the rate of heat transfer from the exposed surfaces of the flange.

Transcribed Image Text:

-10 cm -9.2 cm 20 cm Steam 200°C Tair = 8°C 1 cm 1 cm