410 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 17 



characterize a handbook on the subject. Moreover the problems 

 which were investigated first because of their greater importance 

 and which were the subjects of the reports published earliest, are 

 for that reason not so well covered as is now possible because the later 

 work threw much additional light upon matters not settled at the time 

 of publication of the early reports. Accordingly, the present paper 

 is much more than a reprint of earlier reports, being a complete revi- 

 sion and recompilation of the material available. 



The special investigations reported included development of the 

 methods of measuring air flow in radiator tubes ; experiments upon the 

 effect of nature of surface upon air flow and upon heat dissipation 

 from the surface of metal tubes to a high velocity air stream; experi- 

 ments to ascertain the degree of turbulence in the air tubes of a radia- 

 tor core; mapping of temperature distribution, axially and trans- 

 versely, in the air tubes of radiator cores. In addition to recording 

 these special investigations, the paper contains a full description of 

 laboratory methods and instruments for those tests of radiator cores 

 properly made in the laboratory both of physical properties and geo- 

 metrical characteristics such as size and shape of air tubes and of 

 water tubes. 



The work included laboratory measurements of cooling power, 

 head resistance, and geometrical characteristics of over one hundred 

 types of radiator core. These data are tabulated in an appendix 

 and the performance characteristics of 66 types of core are given in 

 graphical form. The general conclusions from these measurements and 

 from the special laboratory experim.ents mentioned above are incor- 

 porated into an exposition of the fundamental relations between the 

 conditions under which a radiator operates, its characteristics of form 

 and construction, and the properties which describe its performance. 

 This portion of the designer's field is by no means the whole, however, 

 and the paper does not treat the important considerations of stur- 

 diness, ease of construction and repair, cost, form of design imposed 

 by the structure of the aircraft, etc. 



The heat-dissipating power of a given type of core construction 

 was found to be specified completely when the mass rate of air flow 

 was specified. It makes no difference whether a given mass rate is 

 obtained by high velocity and low density or low velocity and high 

 density, a relation which was studied in some detail because of its 

 significance in respect to behavior of aircraft radiators at high alti- 

 tudes of flight. The empirical relation 



