An Al2O3 protective coating on magnesium alloy AZ31 was prepared by a repeated direct sol-gel process annealing at 300℃and a composite coating was also deposited using Al2O3 particles dispersed sol followed by phosph...An Al2O3 protective coating on magnesium alloy AZ31 was prepared by a repeated direct sol-gel process annealing at 300℃and a composite coating was also deposited using Al2O3 particles dispersed sol followed by phosphating treatment and annealing at 300℃.The morphologies,structures and critical adhesive loads as well as corrosion properties of the coatings were comparatively investigated by scanning electron microscopy(SEM),X-ray diffractometry(XRD),nanoscratch test and electrochemical measurement.The results show that the composite coating has a more uniform,crack-free layer and improved adhesion to the substrate as compared with that of the repeated direct sol-gel coating owing to its lower heat strain.The main phases in both coatings consist ofγ-Al2O3 andδ-Al2O3 derived from annealed alumina sol,and the composite coating has an anticorrosion performance which is superior to that of the repeated direct sol-gel coating.展开更多
The airside heat transfer and friction characteristics of seven interrupted fin-and-tube heat exchangers with hydrophilic coating under dehumidifying conditions are experimented.The effects of number of tube rows,fin ...The airside heat transfer and friction characteristics of seven interrupted fin-and-tube heat exchangers with hydrophilic coating under dehumidifying conditions are experimented.The effects of number of tube rows,fin pitch and inlet relative humidity on airside performance are analyzed.The test results show that the influence of fin pitch on the friction characteristic under dehumidifying conditions is similar to that under dry surface,and the friction factors decrease slightly with the increase of number of tube rows.The heat transfer performance decreases as fin pitch and number of tube rows increases.The heat transfer performance and the friction characteristic are independent of inlet relative humidity.Based on the test results,heat transfer and friction correlations in terms of the Colburn j factor and Fanning f factor,are proposed to describe the airside performance of the interrupted fin geometry with hydrophilic coating under dehumidifying conditions.The correlation of the Colburn j factor gives a mean deviation of 9.7%,while the correlation of the Fanning f factor shows a mean deviation of 7.3%.展开更多
基金Project(2005Z023)supported by the Scientific Research Initial Funding of Chongqing University of Technology
文摘An Al2O3 protective coating on magnesium alloy AZ31 was prepared by a repeated direct sol-gel process annealing at 300℃and a composite coating was also deposited using Al2O3 particles dispersed sol followed by phosphating treatment and annealing at 300℃.The morphologies,structures and critical adhesive loads as well as corrosion properties of the coatings were comparatively investigated by scanning electron microscopy(SEM),X-ray diffractometry(XRD),nanoscratch test and electrochemical measurement.The results show that the composite coating has a more uniform,crack-free layer and improved adhesion to the substrate as compared with that of the repeated direct sol-gel coating owing to its lower heat strain.The main phases in both coatings consist ofγ-Al2O3 andδ-Al2O3 derived from annealed alumina sol,and the composite coating has an anticorrosion performance which is superior to that of the repeated direct sol-gel coating.
文摘The airside heat transfer and friction characteristics of seven interrupted fin-and-tube heat exchangers with hydrophilic coating under dehumidifying conditions are experimented.The effects of number of tube rows,fin pitch and inlet relative humidity on airside performance are analyzed.The test results show that the influence of fin pitch on the friction characteristic under dehumidifying conditions is similar to that under dry surface,and the friction factors decrease slightly with the increase of number of tube rows.The heat transfer performance decreases as fin pitch and number of tube rows increases.The heat transfer performance and the friction characteristic are independent of inlet relative humidity.Based on the test results,heat transfer and friction correlations in terms of the Colburn j factor and Fanning f factor,are proposed to describe the airside performance of the interrupted fin geometry with hydrophilic coating under dehumidifying conditions.The correlation of the Colburn j factor gives a mean deviation of 9.7%,while the correlation of the Fanning f factor shows a mean deviation of 7.3%.
