G,5 • TRANSPIRATION-COOLED PIPE FLOW 



ber decreases almost linearly with an increase of the coolant Reynolds 

 number. This is due to the fact that the range of coolant Reynolds num- 

 bers considered in the present investigation is rather small (X ^ 1). As 

 the coolant Reynolds number increases further, the Nusselt number then 

 decreases more gradually. The above phenomenon was also obtained in 

 the case of nonisothermal flow over a plate with coolant injection. 



Nu 



MARINE 

 BIOLOGICAL 



LABORATORY 



libr arT 



WOODS HOLE, f:^A3S. 

 W. H. 0. 1. 



0.25 



0.50 



A 



0.75 



1.00 



Fig. G,5d. Local heat transfer coefficient for various rates of 

 coolant injection {0./PrRe){l/D) = 0.075). (From [32].) 



The ratio of temperature difference (Ti — T^)/(T^ — To) is plotted 

 against the coolant flow ratio vJ/u^D in Fig. G,5e. For a predesignated 

 wall temperature the amount of coolant required per unit time can readily 

 be determined provided that the entrance temperature Ti and the coolant 

 temperature To are known. 



The results obtained from the studies of nonisothermal laminar flow 

 over a plate with coolant injection show that the friction coefficient at 

 the wall decreases with the increase of coolant injection. They also indi- 



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