F • CONVECTIVE HEAT TRANSFER IN GASES 

 Rearrangement of Eq. 10-9 gives 



(0-^(--")^(l;) 



(10-10) 



which is Unear and first order in h^/Prra. as a function of u^ at const x. 

 Symbols h^ and % denote h/K and u/ue, respectively, and the primes 

 indicate differentiation with respect of u^ alone. Integration of Eq. 10-10 

 at const X results in [22] 



Eq. 10-11 gives the enthalpy distribution all the way across the turbulent 

 boundary layer. As expected, the equation is identical in form to Eq. 

 3-17 for laminar flow. 



F,ll. Heat Transfer. Since the equation for enthalpy distribution 

 for a turbulent boundary layer has the same form as for a laminar bound- 

 ary layer, the heat transfer characteristics will also have the same form, 

 viz. 



(Heat transfer) 

 (Stanton number) 



q^ = —StpeUeiK 



ICf 



-K) 



St = 



s 2 



(Recovery enthalpy) h^ = he -]r r 



(11-1) 

 (11-2) 



(11-3) 



where s = ^(1) and r = 272(1). 



In order to compute the local heat transfer g„, it is therefore necessary 

 to determine the recovery factor r, the Reynolds analogy factor s, and the 

 local skin friction coefficient C/. 



Recovery factor. As suggested by experimental data [23], the velocity 

 profile can be conveniently divided into three parts: a laminar sublayer, 

 a transition or buffer zone, and a fully turbulent region [24]. With this 

 artifice, an algebraic formula for the recovery factor as a function of 



( 372 ) 



