What Is Free Convection?

Free convection, a term in the field of atmospheric science, also known as free convection heat transfer, referred to as natural convection, refers to the flow of fluids involved in heat exchange due to the unevenness of its temperature field. The non-uniform temperature causes the non-uniform density field, and the resulting buoyancy becomes the motive force of the flow. Natural convection heat exchange refers to the heat transfer phenomenon caused by natural convection. Natural convection heat transfer is widely found in nature, such as the heat dissipation of electrical components that are not forcedly cooled by fans. Natural convection is widely used in nuclear power plants and other practical productions. ^[1]

Free convection, also known as "free convection heat transfer", referred to as "natural convection". Formed due to uneven temperature of each part

The buoyancy that causes natural convection actually comes from the density gradient of the fluid and the

Natural convection heat transfer problems are often divided into two categories based on the characteristics of the space in which the fluid is located: If the fluid is in a relatively large space,

In recent years, many numerical calculation methods have been proposed to solve the problems of fluid flow and convective heat transfer. Common methods are:

Natural convection heat transfer in an enclosed space is computational fluid dynamics and

For structural thermal analysis, the main purpose is to obtain the temperature distribution on the structure, that is, the wall temperature is unknown, so the temperature difference T between the fluid temperature and the wall temperature is also unknown. In this case, the heat transfer coefficient cannot be calculated from the natural convection experimental correlation alone. On the other hand, ANSYS steady-state thermal analysis uses fluid temperature and heat transfer coefficient as the boundary conditions for structural thermal analysis, and the temperature field distribution of the structure can be obtained through finite element analysis. Therefore, this paper combines ANSYS steady-state thermal analysis and natural convection heat transfer experimental correlation, and proposes an iterative calculation method, which is described in detail as follows: First, assuming a trial heat transfer coefficient, the structure temperature is calculated using ANSYS steady-state thermal analysis Field distribution, and then the temperature difference is obtained based on the actual fluid temperature and the wall temperature calculated by the finite element method. The stress is calculated by the natural convection experimental correlation equation for the corresponding heat transfer coefficient, and then it can be iterated by ANSYS for the second steady state thermal analysis analysis. If the difference between the heat transfer coefficients before and after ANSYS steady-state thermal analysis does not exceed 1%, then iterative convergence is considered and the final heat transfer coefficient is obtained.

This method has the following advantages: (1) Strong versatility. This method has no special pertinence, so it is suitable for the calculation of heat transfer coefficient caused by natural convection; (2) No additional calculation model is needed. Because structural thermal analysis itself requires the establishment of a thermal analysis finite element model, this method only needs to call the model; because ANSYS iterative calculations are performed through structural thermal analysis, there is no need to establish a fluid model. (3) Can use ANSYS parameterized design language (APDL), through programming, to achieve the purpose of ANSYS iterative calculation, improve work efficiency. ^[1]