Question 11.23: Solve Illustrative Problem 11.16 taking into account both co...

Because the conditions of Illustrative Problem 11.16 are the same as for Illustrative Problems 11.21 and 11.22, we can solve this problem in two ways to obtain a check. Thus, adding the results of these problems yields \dot{Q}_{\text{total}}=206.2+214.5=420.7 Btu/h.
We can also approach this solution by obtaining a combined radiation and convection heat-transfer coefficient. Thus, hcombined h_{\text {combined }}=0.9+0.94=1.84 . \dot{Q}_{\text {total }}= 184(\pi \times 3.5 / 12) 5 \times(120-70)=421.5Btu/h. This procedure of obtaining combined or overall heat transfer coefficients is discussed further in Sections 11.5 and 11.6.