Experimental study of forced convection heat transfer of graded metal honeycomb fabricated by additive manufacturing

In this paper, the experimental study is carried out on the convective heat transfer performance of the graded and uniform rectangular honeycomb structure fabricated by additive manufacturing under the constant temperature boundary. The samples are made of the 316 L stainless steel powder. The graded and uniform honeycomb samples have the same mass, overall size, cell width and wall thickness. The cell height is variable for the graded honeycomb and is constant for the uniform honeycomb. First, the overall pressure drop and the surface temperature of the upper and lower surfaces of the samples are directly measured under the different air velocities. The overall convective heat transfer coefficient of the sample is calculated based on the measured data. Then, the whole process of the experiment is simulated in detail based on the numerical method of computational fluid dynamics (CFD). Results show that the experimental results of graded honeycomb and uniform honeycomb are in good agreement with the numerical simulation results, which indicate that the experimental and numerical results are reliable. In addition, the experimental results also confirm that the assumption of Constant Cross-sectional Fluid Temperature (CCFT) will lead to relatively large error, and the crosssectional temperature distribution of cooling fluid must be considered in analyzing the heat transfer performance of graded honeycombs. The new assumption that every individual channel has the same fluid temperature is reasonable. These results provide basis for further optimization design of the graded metal honeycomb to improve the heat transfer performance.