Analysis of external heat dissipation enhancement of oil-immersed transformer based on falling film measure

Abstract

With the increase of power load, the overheating problem of oil-immersed transformer in operation cannot be ignored. Therefore, it is necessary to propose reasonable heat dissipation enhancement measure for oil-immersed transformer in operation and study the influence of the measure on the internal temperature of transformer. The heat transfer process of oil-immersed transformer is analyzed, and the air-side heat transfer coefficient is pointed out to be the important parameter limiting the heat dissipation capacity of the transformer. In order to improve heat dissipation capacity, the measures based on cooling fans and falling film are proposed and the calculation methods for the air-side heat transfer coefficient are conducted, respectively. Moreover, the top-oil temperature and hot-spot temperature under two measures are compared by the thermal-fluid coupling model of oil-immersed transformer. For the transformer operating at rated load and the ambient temperature of 25?C, after the cooling fans are adopted, the top-oil temperature and hot-spot temperature can be reduced by 22.4?C and 20.7?C, while after the falling film is adopted, the top-oil temperature and hot-spot temperature can be reduced by 31.2?C and 28.7?C, respectively. The results show that the falling film is a more effective heat dissipation enhancement measure, which can meet the higher load demand of oil-immersed transformer.