E,7 • INTRODUCTION 



E,6. Concluding Remarks. The calculation of turbulent flow and 

 heat transfer in passages from the conservation equations of momentum, 

 energy, and continuity alone has not yet been found practicable. By intro- 

 ducing physical assumptions to relate the eddy diffusivity to the mean 

 flow, however, and determining several dimensionless constants by meas- 

 uring a velocity profile, heat transfer and friction in a number of circum- 

 stances can be calculated. These cases include heat transfer and friction 

 for various Prandtl numbers for fully developed flow, for the entrance 

 region, for constant and variable properties, and for noncircular passages. 

 In most cases where an experimental check is available the agreement 

 between theory and experiment is good. A particularly good check for the 

 case where the fluid properties are variable was obtained for heat transfer 

 to carbon dioxide in the critical region. 



Although considerable progress has been made in turbulent forced 

 convection heat transfer, much work, both analytical and experimental, 

 remains to be done. The relation between eddy diffusivities of heat and 

 momentum should be more clearly established. Experimental work on 

 heat transfer for liquids with variable properties is desirable. Knowledge 

 of local heat transfer in noncircular passages is still limited and more 

 definitive research on liquid metals is needed. 



CHAPTER 2. SURVEY OF PROBLEMS IN 

 BOILING HEAT TRANSFER 



R. H. SABERSKY 



E,7. Introduction. Boiling heat transfer is defined as the heat 

 transfer from a surface to a liquid under such conditions that the temper- 

 ature at and near the surfaces is sufficient to create the vapor phase. The 

 temperature of the bulk of the fluid is equal to or below the saturation 

 temperature, and the difference between the saturation temperature and 

 the actual bulk temperature is usually called the subcooling. The exist- 

 ence of this type of heat transfer has of course been recognized for a long 

 time. The first technical discussion of the problem is probably that con- 

 tained in a paper by Mosciki and Broder [63] in 1926. The interest in 

 boiling heat transfer has increased, particularly in the last ten years, 

 during which the problem has become of great technical importance in 

 connection with the cooling of rocket engines, the construction of rapid 

 response boilers, and the operation of nuclear power producers. 



Boiling heat transfer may be subdivided into problems occurring under 

 conditions of free convection or forced convection. A typical experimental 

 apparatus for studying free convection boiling may consist of a vessel 

 filled with the test fluid into which an electrically heated metal strip is 



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