Quantitative measurement of spatio-temporal heat transfer to a turbulent water pipe flow

•IR thermography was applied to measure turbulent heat transfer in water pipe flow.•Local and instantaneous heat transfer coefficient was evaluated quantitatively.•Spatio-temporal feature of the heat transfer was clearly visualized.•Statistical values of the spatio-temporal fluctuation were confirmed to be reasonable.

A technique using high-speed infrared thermography was applied to measure the spatio-temporal heat transfer to a turbulent water flow in a horizontal circular pipe. The instantaneous distribution of the heat transfer coefficient and its temporal fluctuation was evaluated by solving inverse heat conduction equation of the heated thin-test-surface. As a result, it was demonstrated that the quantitative measurement, not only the time-averaged heat transfer, but also the statistics of the spatio-temporal fluctuation, was possible using this technique. In addition, a unique feature of the spatio-temporal heat transfer was clearly visualized for the turbulent pipe flow, which was dominated by the streaky structure similar to that for the turbulent boundary layer and the turbulent channel flow.