The main methods of single-phase convection heat transfer enhancement are analyzed in this paper, and the unity of contradiction between heat transfer enhancement and energy consumption(or exergy destruction)is expounded.The thermodynamic relationship between heat(or exergy)transfer efficiency and energy consumption(or exergy destruction)as well as driving forces is established,and a general theoretical principle for single-phase convection heat transfer enhancement is further obtained. The principle shows that temperature gradient field distribution and velocity field distribution constrain each other,and that the optimum heat transfer efficiency can be obtained when they are synergetic.If the level of the synergy of temperature gradient field distribution with velocity field distribution is determined,the relative uniform temperature gradient is required,and vice versa.The principle also shows the relationship of relative temperature gradient with specific heat and coefficient of heat conductivity.The deduced results can be used as a theoretical guidance for single-phase convection heat transfer enhancement and optimum design of heat exchangers. The main methods of single-phase convection heat transfer enhancement are analyzed in this paper, and the unity of contradiction between heat transfer enhancement and energy consumption (or exergy destruction) is expounded. Thermodynamic relationship between heat (or exergy) transfer efficiency and energy consumption (or exergy destruction) as well as driving forces is established, and a general theoretical principle for single-phase convection heat transfer enhancement is further obtained. The principle shows that temperature gradient field distribution and velocity field distribution constrain each other, and that the optimum heat transfer efficiency can be obtained when they are synergetic.If the level of the synergy of temperature gradient field distribution with velocity field distribution is determined, the relative uniform temperature gradient is required, and vice versa. The principle also shows the relationship of relative temperature gradient with specific heat and coefficient of hea t conductivity. The deduced results can be used as a theoretical guidance for single-phase convection heat transfer enhancement and optimum design of heat exchangers.