(a) Schematic depiction of probing upstream (⁠$Δx/w<0$⁠) or downstream (⁠$Δx/w>0$⁠) the pump induced hot-spot in the microchannel. (b) Anisotropic TDTR measurements for Ti-coated glass with flowing or stagnant water in the microchannel. (c) Corresponding thermal effusivity of water (left axis) and HTC (right axis) based on our differential TDTR analysis scheme (⁠$τd=$ 100 ps, $fmod=$ 962 kHz, $w=$ 9.5 μm).