The optimized design of one-side-heated plasma-facing components (PFC) is dependent on knowing the local distribution of inside wall heat flux in the flow channels. The local inside wall heat flux can be obtained from selectively chosen local PFC wall temperatures close to the inside boundary of the flow channel. To this end, three-dimensional thermal measurements for a one-side-heated monoblock were made and show: (1) the three-dimensional variation of the wall temperature close to both the heated and fluid-solid surface boundaries, (2) the resultant effects of local subcooled flow boiling on the 3-D wall temperature/outside heat flux relationship – one of which is the 3-D wall temperature profile is almost unchanged in the vicinity for incident heat flux levels between the onset to fully developed boiling and CHF, and (3) the occurrence of local CHF and local post-CHF. The monoblock has a 180.0 mm heated length, has a 10.0 mm inside diameter, and has a circular-like cross-section with a 30.0 mm nominal outside diameter.