A small pre-cooling heat exchanger with 0.38 mm tubes has been built and tested using conditions reflecting the operating characteristics of the helium flight precooler in the air breathing rocket engine of the SKYLON aerospaceplane. This paper discusses the manufacturing techniques developed for the construction of fine tube high pressure heat exchangers with compactnesses up to 3000 m2/m3. Work centred on brazing large numbers of very thin wall tubes to high reliability. Repeatability of the results was ensured by the use of a plating technique for pre-placement of the braze alloy. Process conditions were also refined to facilitate good wetting of high chromium steels with very low erosion on thin wall tubes in standard industrial vacuum furnaces. The paper also discusses the results obtained from heat transfer experiments using the exchanger. Power transfer rates close to 2 GW/m3 with temperature changes of up to 500°C were observed. The results showed that heat transfer performance remained predictable down to hydraulic diameters of a third of a millimetre. The paper also discusses inconsistencies that were encountered in the matrix pressure loss predictions. These could not be explained using the one dimensional correlations currently employed.
|Translated title of the contribution||An experimental precooler for airbreathing rocket engines|
|Pages (from-to)||199 - 209|
|Number of pages||11|
|Journal||Journal of the British Interplanetary Society|
|Publication status||Published - May 2001|