From the analysis of convective heat transfer mechanism, it can be known that the convective heat transfer coefficient is determined by the temperature gradient in the thermal boundary layer. The temperature gradient or the thickness of the thermal boundary layer is related to many factors such as the physical properties of the fluid, temperature, flow conditions, and geometrical conditions of the wall.
Thermal conductivity is a measure of thermal conductivity and is the thermal property of a substance. It is numerically equal to the heat transfer flux per unit temperature gradient. The larger the thermal conductivity, the faster the thermal conductivity. The convective heat transfer film is numerically equal to the convective heat transfer rate per unit heat transfer area under unit temperature difference, which reflects the speed of convective heat transfer. The larger the convective heat transfer coefficient, the faster the convective heat transfer. It is not a physical property of the fluid. Instead, it is affected by multiple factors, reflecting the size of convective heat transfer resistance.
The total heat transfer coefficient represents the unit heat transfer area and the heat transfer rate under the unit heat transfer temperature difference, and reflects the intensity of the heat transfer process. It should be noted that the total heat transfer coefficient must correspond to the selected heat transfer area, which means that Important parameters of heat exchanger performance. The factors that affect the total heat transfer coefficient mainly include fluid physical properties, operating conditions and heat exchanger types.