A study of the heat transfer of an atomizer gas jet impinging perpendicular on a circular cylinder

This contribution presents the methodology and results from an experimental and numerical study of the heat transfer behavior of the gas-only jet flow from a close-coupled atomizer (CCA) configuration impinging on a heated cylindrical surface. A set of experiments are conducted under different operating conditions (gas pressures 0.6, 0.8 and 1.0 MPa) to measure the local heat transfer coefficient (HTC) on the surface of the cylinder by recording the cooling curve at specific locations along circumferential and axial directions. The numerical study of the heat transfer is executed by employing computational fluid dynamics (CFD) under the same conditions as in the experiments. The Transition SST model is selected for turbulence closure as it obtained results most close to the experimental ones. Predictions of HTC on the cylindrical surface are derived from this model with variable parameters, i.e., nozzle-to-substrate distance (110, 130 and 150 mm), diameter of the cylinder (80, 100, 120 mm) and the temperature difference between the cylinder and ambient temperature (20-730 K). In addition, the gas flows from a circular nozzle and the atomizer configuration with same exit area are compared by the CFD simulation, which shows that the gas jet flow becomes self-similar when the distance to the nozzle is > 80 mm. The experimental and numerical results both show that at each measured position the heat flux q obtains a linear relationship with the temperature difference. The fitted line in the stagnation region has a small negative intercept while that at other positions is close to 0. The local HTC variation in the circumferential and axial directions on the cylinder surface and the parameters affecting the distribution of the HTC are outlined and discussed.