Heat pipe cooled leading edge design for hypersonic flow survey rake

A cooling design was needed for a hypersonic flow survey rake leading edge. A heat pipe cooled leading edge was designed for the rake. The external and internal heat transfer relationships were established and incorporated into a FORTRAN computer code for analysis using preliminary design concepts. The results of the code were used to down select a final concept for thermal and structural stress analysis. The two working fluid candidates were water and mercury and the operating temperature range of investigation was 600 to 1400°R.

The water heat pipe was found to be limited by boiling in the wick structure. The mercury heat pipe was found to be limited by the vapor velocity in the heat pipe vapor channel and the thermal stresses in the heat pipe case, but showed potential as a viable option to cool the rake leading edge. The minimum operating temperature of the mercury heat pipe was found to be 950°R. A finer mesh three dimensional finite element model of the heat pipe outer case was recommended for the steady state structural and thermal analysis. Investigation of start-up loads and associated thermal stresses was recommended. Fabrication and testing of a portion of the survey rake leading edge mercury heat pipe was also recommended.