Abstract
The authors call attention to the increasing importance of the economic design of refrigerator cars and discuss the factors which must be taken into account in finding the proper thickness of insulation. The outstanding feature of the paper is the use of alignment charts to determine readily answers to problems involving many variables. By aid of these, or similar charts, one may determine not only the economic thickness of insulation but also the saving which would result from the adoption of the correct thickness compared with any other thickness; furthermore, the economic advantage of one kind of insulation over another may be found.
The paper gives a brief discussion on the economy of using regranulated cork or air spaces in some constructions. It outlines, by aid of average shade-temperature maps, the means of approximating external surface temperatures and notes the results of tests on roofs, sides, and floors as affected by direct sunlight and color of paint.
Reference is also made to the analysis by the authors of the cost of transporting extra weight of insulation, or extra weight of cars as a whole, and the final average figure is found to be about 0.10 cent per ton-mile for transcontinental routes.
All of the above and other factors form a part of the data for a complete solution for economic thickness, whether it is solved by a formula or by charts.
