Convection heat transfer coefficient of building glasses under salt deposition conditions

Abstract

Glass buildings in coastal regions and islands exposed to the hydrothermal marine environment, in addition to salt deposition and erosion, lead to a change in the surface convective heat transfer coefficient (CHTC) and gradual degradation of the building energy and thermal performance. However, limited research has been conducted on the influence of salt deposition on the CHTC of building glasses. Hence, in this study, the salt deposition characteristics of the glasses were obtained by conducting an accelerated salt spray test. In addition, the influence of salt deposition on the CHTC and heat transmission coefficient (HTC) was investigated. The results indicate that the sizes of the salt spots on the glass surface increased significantly and unevenly. The salt deposition per unit area (p) exhibited a logarithmic growth trend between 14.4 and 40.0 mg/m2, considering the spray time. Under the 10% saline condition, p was larger than that under the 5% saline condition, ranging between 15.6 and 44.3 mg/m2, with an average increase rate of 11.6%. The CHTC exhibited a monotonic increase in terms of the deposition amount on the glass. Compared with the salt-free scenario, the maximum increase in CHTC was 178.7%, which exhibited a linear relationship with p. When p increased to 40.0 mg/m2, the HTC increase rate of the single clear glass and hollow Low-E glass reached 20.1% and 5.2%, respectively. The findings of this study provide insights into the influence of salt deposition on the CHTC of building glasses and can serve as a basis for energy consumption studies in coastal regions.