An Investigation Of Aircraft Heaters 1 Elementary Heat Transfer Consideratin In An Airplane

This report was written in an attempt to clarify the basic factors of heat transfer applied specifically to aircraft heating and to guide the experimenter in planning experiments to obtain further data. In the absence of exact test results, the authors have studied the literature and tentatively present equations and charts for the various thermal resistances encountered in aircraft work. These recommendations will be changed as more is known about the various components of the system under consideration.

An analysis is presented of the factors determining the power efficiency of radiation thermopiles of that type in which the receivers consist either of parts of the conductors themselves or of coatings or other electrically insulating materials in intimate contact with these conductors. On the basis of this analysis, which is applicable to thermopiles of a wide variety of constructions and materials, criterions for maximum power efficiency can be calculated. Such criterions are obtained for a silver-constantan plated-type thermopile. The design and construction of thermopiles in accordance with these criterions are described, and test data are reported, showing agreement between actual and predicted performance.

An approximate method for determining the convective cooling requirement in the laminar-boundary-layer region of a body of revolution in high-speed flight was developed and applied to an example body. The cooling requirement for the example body was determined as a function of Mach number, altitude, size, and a surface-temperature parameter. The maximum value of Mach number considered was 3.0 and the altitudes considered were those within the lower constant-temperature region of the atmosphere (40,000 to 120,000 ft). The extent of the laminar boundary layer was determined approximately at each condition as a function of the variables considered.

Presented herein is an analysis of parallel flow and contraflow single pass heat exchangers, together with charts which allow the direct evaluation of the thermal performance of such units without recourse to trial-and-error techniques. The use of the equations and charts is illustrated by several examples. The analysis indicates that one of the frequently stated restrictions on the use of the logarithmic mean temperature difference - that is, that the exchanger must be perfectly insulated - is not always necessary.