Field measurement of outside convective heat transfer coefficient on horizontal roof using naphthalene sublimation technique

The outside convective heat transfer coefficient (CHTC) of building roof is an important parameter for accurately calculating heat transfer through roof and simulating airflow around buildings. However, the correlations concerning CHTC in various studies seem to be discrepant. The experiment using naphthalene method to measuring CHTC was carried out on a nine-story building roof during 15 August 2006-22 August 2006. Test specimens with glazed surface were ranged at twenty points on building roof. Test specimens used in this study were cast by molten naphthalene in molds. The experimental result shows that the CHTC on building roof is linear function of representative wind speed, the slope of the linear function is 7.64 and the correlations coefficient is 0.92. The variances of temperature on test specimen's surfaces and the difference between air temperature and surface temperature of naphthalene didn't influence measurement result. The CHTC obtained in this study was compared with those in references using heat balance method. It is shown that the CHTC obtained in this study is larger than previous works, especially in large wind velocity range. The difference may be interpreted by different size of target building, height of representative wind velocity and wind turbulence.