Article ID: 24-11HE
Flow boiling heat transfer of water in a horizontally placed rectangular minichannel (cross sectional area 2 mm × 2 mm) was measured with high spatio-temporal resolution (4000 fps, 25 μm/pixel) using a high speed infrared (IR) camera. At the same time, two high speed cameras were used to photograph the behavior of the gas liquid interface. To achieve this measurement, we fabricated a heater that transmits visible light by depositing an indium tin oxide (ITO) film on calcium fluoride (CaF2) and installed it on the bottom of the rectangular minichannel. Furthermore, we performed unsteady three dimensional heat conduction analysis inside the visible light transparent heater using the measured temperature distribution of the ITO film as a boundary condition. After evaluating the unsteady heat loss inside the measurement surface, we calculated the spatio-temporal fluctuations of the wall heat flux. The experimental conditions were a wall heat flux of 20 kW/m2, a mass flow rate of 100 or 200 kg/(m2·s), and a vapor quality ranging from slag flow to annular flow. As a result, the high speed and complex heat flux fluctuations corresponding to each flow pattern were quantitatively clarified.
