Abstract:

In this paper, some problems in the current researches on external convective heat transfer of buildings are analyzed, and a new naphthalene sublimation method is developed for the field measurement of external convective heat-transfer coefficient （CHTC） of building roof. Experimental results show that the CHTC of the roof is in a positive linear relation with the representive velocity of wind flowing on the roof, and that the CHTC ranges from 5 to 50 W/（m²·K） at a representive wind velocity of less than 5.6 m/s. Analytical results also indicate that the fluctuation of the temperature on the surface of naphthalene test specimens and the temperature difference between the air and the roof sligthly affect the measurement resluts. Moreover, by considering the influence of building dimensions and by choosing the distance from the roof edge to the measurement point as the representive length, a dimensionless corelation about the external convective heat-transfer characteristics is obtained. The effectiveness of the proposed naphthalene sublimation method is finally validated by a heat balance experiment.

Key words: horizental roof, convective heat transfer, naphthalene sublimation method, field measurement