Factors affecting convective heat transfer of heat exchange vessel

There are many factors that affect convection heat transfer. Mainly include:

(1) The cause of the flow, that is, forced convection or natural convection. The flow of the fluid in forced convection is driven by an external force, while the flow of fluid in natural convection is driven by the temperature difference (density difference) in the fluid caused by the heat exchange itself.

(2) Whether the fluid has a phase change. The boiling heat transfer or condensation heat transfer with phase change is quite different from the heat transfer law of single-phase fluid, and the latent heat of vaporization needs to be considered. For example, in the process of constant pressure vaporization of saturated water, the fluid absorbs heat and vaporizes, but the temperature remains unchanged.

(3) The state of flow, that is, turbulent flow or laminar flow. The thermal convection in the turbulent boundary layer is strong, while the thermal convection in the laminar boundary layer is weak.

(4) The geometry of the wall. When fluid flows through solid surfaces of different shapes, the flow pattern is affected by the geometrical factors of the wall. For example, when the same fluid and the same incoming velocity flow through the flat plate and the transversely swept circular tube, the heat exchange conditions are different.

(5) The physical properties of the fluid, including the thermal conductivity, density, specific heat capacity, kinematic viscosity and bulk expansion coefficient of the fluid.