Unsteady Heat Transfer in a Multilayer Composite Cylinder Containing Porous Media

• ·The heat transfer of porous media is simplified by the local heat balance assumption. • ·An experiment was designed to validate the reliability of this model. • ·Temperature control can be simplified by using a centralized and surrounding heat source. • ·Effect of material parameters on temperature indicates the heat-insulation property. The influence of heating equipment with low thermal conductivity, such as vacuum drying equipment and electric heating atomization systems, on the temperature distribution of heated objects is vital for structure design. The transient temperature of small heating equipment is difficult to obtain, particularly when the geometric size of the equipment is less than 0.1 m . Based on Fourier’s law, a heat transfer model for a multilayer composite cylinder with porous media is established to solve this problem. The heat transfer of the porous media is simplified by the local heat balance assumption. An experiment is designed to validate the reliability of the model. The results of this study indicated that the temperature difference between the inner and outer parts of the composite cylinder with thermal conductivity is noticeable when heated by a centralized heat source. When the temperature of the centralized heat source is approximately 190 °C, the temperature difference between the inner and outer parts of the porous medium layer in the composite cylinder is approximately 50 °C. Moreover, when the temperature of the outer part of the porous medium layer in the composite cylinder is approximately 50 ℃, the temperature increased by approximately 1 °C for every 10 % decrease in the porosity. The centralized heat source cannot be used to uniformly heat a material with low heat transfer performance. Increasing the equivalent thermal conductivity of porous media materials or changing the heating structure can effectively improve this problem. Furthermore, the temperature distribution of the composite cylinder can be easily controlled by adjusting the temperatures of the surrounding and centralized heat sources. This study proposes a simple and accurate unsteady temperature prediction method for composite cylinders containing porous media. The temperature of the heating structure and the surrounding environment of the composite cylinder are obtained through simple experiments, and a theoretical model is used to predict the transient temperature of the composite cylinder during the heating process. Moreover, the influence of various factors affecting the heat source and heated object on the unsteady temperature of the composite cylinder with porous media is clarified. This new technology can solve the difficulty in measuring the temperature field of heating structures and heated objects in small heating equipment. This work can aid in the heat source design of small heating equipment.