Wall effect on the hot-wire signal without flow

The effect of four metal and four non-metal wall materials on the hot-wire signal has been examined using three different hot-wire probe orientations under no-flow condition. The results indicate that the effect of the wall on the hot-wire signal at a given distance from the wall increases with wall thermal conductivity up to a relative thermal conductivity, k/k 0 , of 100, and thereafter the signal due to wall proximity remains at this asymptotic value. It has been further observed that the wall effect becomes negligible for distances greater than 0.5 mm from the wall.