E • CONVECTIVE HEAT TRANSFER AND FRICTION 



that the Nusselt and Reynolds numbers for a tube are given by 



2r* Pr 



Re = 2w*r* 



where r* = r^ Vtw/pw/ ii^^/pw) , r^ being the tube radius, 



/rr* Jo 



and 



//" w*(r* - y*)dy' 



u*{r* — y*)dy* 



(3-4) 

 (3-5) 



(3-6) 

 (3-7) 



The Nusselt number in Eq. 3-4 is based on the difference between the 

 wall temperature and the mixed mean or bulk temperature T*. The relation 



10,000 



1000 



Q 



100 



1000 



1 0,000 



Re 



100,000 



pUbD/jji 



1,000,000 



Fig. E,4c. Predicted fully developed Nusselt numbers plotted 

 against Reynolds number for various Prandtl numbers. 



among Nusselt, Reynolds, and Prandtl numbers can be obtained from 

 these equations and the generalized distributions given in Fig. E,4a and 

 E,4b. The parameter r* appears in all the equations and is assigned arbi- 

 trary values for plotting the curves. 



Predicted Nusselt numbers for fully developed heat transfer are 

 plotted against Reynolds number for various values of Prandtl number 

 in Fig. E,4c. Examination of the curves indicates that the slopes of the 



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