The heat transfer coefficient of the external surface of building envelope （） is a fundamental parameter in thermal calculations. However

the unique climatic conditions in high-altitude regions result in significant deviations in compared to standard values used for low-altitude areas. To determine the measurement methods and calculation values of in high-altitude areas

this study employed the naphthalene sublimation method and simplified radiation theory to measure the convective heat transfer coefficient （） and radiative heat transfer coefficient （） of the external surface of an exhibition hall in Lhasa. Based on typical annual meteorological data

the hourly values of for the entire year are calculated. The results demonstrate that the naphthalene sublimation method has a measurement error of 4.3%

confirming its applicability in Lhasa. The measured ranges from 2.22 to 20.33 W/（m·K）

with horizontal surfaces exhibiting values 0.86 W/（m·K） higher than vertical surfaces

showing a linear correlation with wind speed. The ranges from 4.50 to 5.61 W/（m·K）

with small variation

and an average value of 4.88 W/（m·K） is recommended. Considering the actual wind speed and radiation conditions in Lhasa

the calculated annual values most frequently fall within the range of 10.00-15.00 W/（m·K）

with winter and summer averages of 15.63 and 16.69 W/（m·K）

respectively

both of which are lower than the standard recommended value of 18.00 W/（m·K）.