Calibration of single-surface hot films and in-line hot-film arrays in laminar or turbulent flows

Abstract

Experimental and numerical investigations were performed concerning the heat balance and calibration of single-surface hot films and surface hot-film arrays in laminar or turbulent flows. Emphasis is placed on the influence of the thermal interaction among sensor, fluid and the wall and among different sensors from an in-line hot-film array on the calibration of the sensors. Experimental and numerical investigations of the coupled flow and structure temperature field in the vicinity of an in-line surface hot-film array are presented. The mechanism of thermal interactions is demonstrated, namely the strong effect of an increasing thermal boundary layer thickness on the convective and conductive heat losses of each single sensor of the array due to an increasing number of upstram sensors being `operated'. The numerical simulations were performed both for laminar and the turbulent flow as well as for a different number of sensors. The results are compared with experiments demonstrating that, due to the thermal interaction, the downstream decrease in the total heat losses of a sensor from an in-line array has a great effect on the calibration.