Prediction of wet snow shedding from surfaces under various heat transfer modes. (5th March 2022) - Mohammadian, Behrouz
Highlights: Real-time snow liquid water content was measured using a surface-mountable sensor. Heat balance equations were developed to calculate snow's liquid water content. Different mechanisms of snow shedding from surfaces were recognized and classified. A new algorithm was proposed to predict snow sliding from surfaces. Abstract: Prediction of snow shedding from overhead structures is crucial to minimize threat to public safety due to snow falling from these structures. Liquid water content (LWC) of snow impacts snow adhesiveness to various surfaces; therefore, its measurement and prediction are crucial in estimating snow shedding from structures. Here, a theoretical heat model was developed to calculate and predict the LWC of snow as a function of temperature, radiation intensity, and wind velocity. To verify the predictions, snow LWC was measured using a surface-mountable sensor in a real-time and non-destructive way, indicating a good agreement between the theoretical results and experimental values. Despite three to four orders of magnitude smaller wind force when compared to snow adhesion force, it was found that wind has a significant effect on snow melting. At ≈ 3 °C average air temperature, a wind with an average velocity of ≈ 2 m/s increased the snow melting rate by at least 90%, when compared to the free convection experiments. In addition, an inclined setup was used to measure snow adhesion on HDPE plates and study effects of snow weight and its LWC on snow shedding from these surfaces. It was observed that the shear adhesion of snow on the HDPE plates decreases from ≈ 59 (Pa) to ≈ 34 (Pa) when LWC changes from ≈ 3% to ≈ 23%. Three snow shedding mechanisms - detachment, melting followed by sliding, and complete melting - were identified. Detachment occurred for snow with LWC of < ≈ 5% when snow shearing weight force dominated snow shear adhesion. Snow melting might reduce its adhesion to a level that its shearing weight force can dominate it, leading to snow sliding. During complete melting experiments shearing weight force never exceeded shear adhesion forces. Finally, snow shedding mechanisms were predicted theoretically and verified experimentally, and a flowchart was presented to predict snow shedding from the HDPE plates.