Experimental determination of the recovery factor on cylindrically flow-around temperature sensors Part 2: Determination of the local, tangential surface temperature distribution

Abstract

It is known in the literature that in the case of compressible fluids, higher values than the fluid temperature are displayed on temperature sensors, among other things due to the accumulation point flow, which is taken into account with the help of the recovery factor. In Part I of this series, the test rig and integral results for the determination of the recovery factor on cross-flowed temperature sensors between 1.5 mm and 8 mm diameter were presented. The Mach number as well as the Reynolds and Prandtl numbers have an influence on the recovery factor. These integral results will be verified by measuring the tangential temperature distribution. For this purpose, a special sensor carrier was developed and moved quickly through the ambient air at different angular positions so that the tangential temperature distribution could be determined. In accordance with the theory, the highest temperature is at the accumulation point with the total temperature and the local recovery factor is 1. The temperature drops continuously to an angle of about 80°. In the wake of the cylinder there is a roughly constant temperature level. If an average value is formed from the measured values of the local recovery factors, a good agreement with the integral results from Part I is obtained.