Comparative Experimental Study on Heat Transfer Characteristics of Building Exterior Surface at High and Low Altitudes

The external surface heat transfer coefficient of building envelope is one of the important parameters necessary for building energy saving design, but the basic data in high-altitude area are scarce. Therefore, the authors propose a modified measurement method based on the heat balance of a model building, and use the same model building to measure its external surface heat transfer coefficient under outdoor conditions in Chengdu city, China at an altitude of 520 m and Daocheng city at an altitude of 3750 m respectively. The results show that the total heat transfer coefficient (h(t)) of building surface in high-altitude area is reduced by 34.48%. The influence of outdoor wind speed on the convective heat transfer coefficient (h(c)) in high-altitude area is not as significant as that in low-altitude area. The fitting relation between convection heat transfer coefficient and outdoor wind speed is also obtained. Under the same heating power, the average temperature rise of indoor and outdoor air at high-altitude is 41.9% higher than that at low altitude, and the average temperature rise of inner wall is 25.8% higher than that at low altitude. It shows that high-altitude area can create a more comfortable indoor thermal environment than low-altitude area under the same energy consumption condition. It is not appropriate to use the heat transfer characteristics of the exterior surface of buildings in low-altitude area for building energy saving design and related heating equipment selection and system terminal matching design in high-altitude area.