There are evident obstacles to the accurate ot prediction of thermal conditions in soils. In the first place, the term “prediction” must be limited to determination of variations of temperature expected on the basis of observed or assumed initial distributions and subsequent surface‐conditions. The great difficulty of measuring thermal properties, which are subject to complex varition with structure and packing as well as with moisture‐content, remains the most severe limitation. Moreover, the migration of water durIng freezing is likely to invalidate the most painstaking determination of initial soil‐properties.
Nonconvective radiators of single or double-active surface design are analyzed for surface temperature distribution; also for view factors in the case of fin-and-tube geometry. Methods and examples of maximizing heat rejection per unit weight are given.
Despite the advances in the statistical theory of turbulence, the PRANDTL [see 1 of “References” at end of paper] concept of mixing‐length still affords the most convenient method of evaluating momentum‐transfer from velocity‐profiles in turbulent flow. In symmetrical conduits, eddy‐diffusivity is known directly from the BOUSSINESQ quotient of shear‐stress and velocity‐gradient. Hence mixing‐length is not essential for the expression of eddy‐diffusivity in pipe‐flow, but is convenient when the distribution of shear‐stress is not known, as in most flow‐problems in meteorology and hydrology.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.