关键词: 对流换热 , 导热 , 临界污垢层厚度 , 临界热绝缘层厚度

Abstract: Based on the effect of fouling on heat transfer process，the critical fouling layer thickness was firstly put forward． The expressions of the critical fouling layer thickness were given and the effect of relative parameters on the critical fouling
layer thickness was discussed．In the meantime， the critical fouling layer thickness was compared with the critical thermal insulation layer thickness．The results show that the critical fouling layer thickness may be theoretically used to explain the phenomena of enhancement heat transfer at the initial forming period of fouling under fixed conditions． Furthermore， the critical fouling layer thickness is determined by mass flow rate of fluid， the physical properties of fluid and the thermal conductivity of fouling layer itself， etc． Meanwhile， the presence of the critical fouling layer thickness is subjected to the specific conditions of convective heat transfer，and the critical fouling layer thickness is different from the critical thermal insulation layer thickness although the fouling layer and thermal insulation layer both have poor thermal conductivity．

Key words: Convective heat transfer , Conduction , Critical fouling layer thickness , Critical thermal insulation layer thickness