Replot the data points of Figure 5.9(b) on log-log paper and find an equation approximating the best correlation line. Compare your results with Figure 5.10. Then, suppose that steam at 1 atm and 100°C is flowing across a 5-cm-OD pipe at a velocity of 1 m/s. Using the data in Figure 5.10, estimate the Nusselt number, the heat transfer coefficient, and the rate of heat transfer per meter length of pipe if the pipe is at 200°C and compare with predictions from your correlation equation.

Question

GIVEN

Figure 5.9(b) in text

Steam flowing across a pipe

Steam pressure = 1 atm

Steam temperature (Ts) = 100°C

Pipe outside diameter (D) = 5 cm = 0.05 m

Steam velocity (U?) = 1 m/s

Pipe temperature (Tp) = 200°C



FIND

(a) Replot Figure 5.9(b) on log-log paper and find an equation approximating the best correlation line

(b) Find the Nusselt number (Nu), the heat transfer coefficient (hc), and the rate of heat transfer per

unit length (q/L) using Figure 5.10

(c) Compare results with your correlated equation

ASSUMPTIONS

Steady state

Radiative heat transfer is negligible

SKETCH



PROPERTIES AND CONSTANTS

From Appendix 2, Table 35, for steam at 1 atm and 100°C

Answer 1

(a) The data taken from Figure 5.9(b) is shown below and plotted on a log-log scale





Fitting this data with a linear least squares regression yields:



(b) For the given data,



Although Figure 5.10 applies to Reynolds numbers between 3 and 100, we will apply its results to the

larger Reynolds number for this case for the purpose of comparison



From Table 5.3



The rate of convective heat transfer is given by Equation (1.10)



(c) The correlation from part (a) yields



The results obtained from Figure 5.10 are 28% lower than these results.