pappas-nasa-tn-2473-blowing

pappas-nasa-tn-2473-blowing - NASA T E C H N I C A L N O T...

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NASA TECHNICAL NOTE NASA TN D-2473 - -- -_ /i . HEAT-TRANSFER MEASUREMENT FOR BINARY GAS LAMINAR BOUNDARY LAYERS WITH HIGH RATES OF INJECTION by C. C. Puppus and Arthur F. Okuno Ames Reseurch Center Moffett Field, Cui$ 1 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 0 WASHINGTON, D. C. 0 SEPTEMBER 1964 B il r" II
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TECH LIBRARY KAFB, NY 0079576 HEAT-TRANSFER MEASUREMENT FOR BINARY GAS LAMINAR BOUNDARY LAYERS WITH HIGH RATES OF INJECTION By C. C. Pappas and Arthur F. Okuno Ames Research Center Moffett Field, Calif. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION ~ For sole by the Office of Technical Services, Deportment of Commerce, Washington, D.C. 20230 -- Price $1.25
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HICAT-TRANSFER MEASUREMENT FOR BINARY GAS LAMINAR BOUNDARY LAYERS WITH HIGH RATES OF INJECTION By C. C. Pappas and Arthur F. Okuno Ames Research Center Moffett Field, Calif, SUMMARY Local values of surface heat transfer, wall temperature, and recovery factor were measured on a 15' porous cone with helium, air, and Freon-12 gas injection into the air stream. The effective Reynolds numbers were within the range of 1.4x1O5 to l.3X106. Mach numbers 3.66 and 4.35. Helium and Freon-12 injection tests were made at Mach number 4.34. Air injection tests were made at the cone With air and Freon injection, the wall temperature shows a sharp rise from the laminar value at the start of transition to a peak in the transition region, then falls to the turbulent value. The peak wall temperature for one air injection test exceeded the air stream total temperature by 30' F and the coolant temperature by 184' F. changed slightly at the start of transition but did not peak in the transi- tion region. With helium injection the wall temperature The laminar heat-transfer coefficients with air injection agree with other experiments and with theory. The values go to zero at finite injection rates and remain near zero at higher injection rates. The recovery factor decreases uniformly with injection and agrees with theory. With Freon injection, the heat-transfer coefficients decrease with increasing injection rate more rapidly than predicted. The values go to zero at finite injection rates and remain near zero at higher injection rates. The recovery factor with injection decreases uniformly to a value of 0.70. For helium gas injection, the Stanton numbers initially increase to 1.19 times the zero injection value and then fall off with increased injection to approach the theoretical value. The rise in heat-transfer coefficient occurs at the lower Reynolds numbers of the test and decreases with increased Reynolds numbers. At the highest Reynolds numbers the heat-transfer coeffi- cient initially decreases from its zero injection value. The binary laminar boundary-layer theories should be reconsidered in view of these results. The recovery factor values are essentially in agreement with the theory of Baron which considers the effects of thermal diffusion.
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INTRODUCTION One of the more effective heat protection mechanisms of an ablating cooling system is the heat blockage effect which results from the efflux of gases from an ablating surface. This effect is difficult to isolate and
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pappas-nasa-tn-2473-blowing - NASA T E C H N I C A L N O T...

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