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 foraccurately calculating heat transfer through roof and simulating airflow around buildings. However, thecorrelations concerning CHTC in various studies seem to be discrepant. The experiment usingnaphthalene method to measuring CHTC was carried out on a nine-story building roof during 15 August2006-22 August 2006. Test specimens with glazed surface were ranged at twenty points on buildingroof. Test specimens used in this study were cast by molten naphthalene in molds. The experimentalresult shows that the CHTC on building roof is linear function of representative wind speed, the slope ofthe linear function is 7.64 and the correlations coefficient is 0.92. The variances of temperature on testspecimens surfaces and the difference between air temperature and surface temperature ofnaphthalene didnt influence measurement result. The CHTC obtained in this study was compared withthose in references using heat balance method. It is shown that the CHTC obtained in this study islarger than previous works, especially in large wind velocity range. The difference may be interpretedby different size of target building, height of representative wind velocity and wind turbulence.