Numerical Study on Convective Heat Transfer Performance in Helix Lattice Sandwich Panel

Abstract

Sandwich structures have been widely used as thermal and load-bearing materials in astronautic and aeronautic applications. owing to their advantages of high specific strength and stiffness. Among them, the X-type lattice cored sandwich panel has a superior thermal performance, with a larger pressure drop. In order to solve the disadvantage of higher pressure drop of the X-type lattice, this paper propose a new structure of helix lattice sandwich panel by modifying the structure of the X-type lattice at a similar porosity level. Forced convection of air in the helix lattice sandwich panel was numerically studied based on the validated model in available literature. The flow and heat transfer characteristics between the helix lattice and X-type lattice were compared. Results reveal that the fluid flow pattern of the helix lattice and the X-type lattice have similarities and differences. The similarity is that both of them cause a spiral type of flow and two same type of secondary flow, the difference is that compared with X-type lattice, the smaller blockage of flow area by the ligaments of the helix lattice leads to a large smooth mainstream. Besides, the overall Nusselt number of the helix lattice is slightly lower than that of X-type one with an average value of 6.69% at a certain Reynolds number, the same material thermal conductivity and similar porosity level. Although the flow pattern in the helix lattice is similar to that in X-type lattice, the smooth mainstream in the helix lattice inevitably limited the flow mixing which lead to a lower area-averaged Nusslet number on both the substrates and the ligaments relative to X-type one. However, in terms of pressure drop, the helix lattice is significantly lower than the X-type lattice due to smaller flow area blockage and smooth ligament structure, which is reduced by nearly half. The helix lattice core sandwich panel can maintain a high level heat transfer performance with little loss of pressure drop. For a given pumping power, the helix lattice outperforms X-type lattice by up to 6.65%. Furthermore, as the pumping power increases, the heat transfer performance of the helix lattice will be better than X-type lattice. Therefore, it can be considered that the helix lattice core sandwich panel solves the disadvantage of relatively high pressure drop in the X-type lattice, greatly reduced the pressure drop and the required pumping power with less heat transfer performance loss. The helix lattice core sandwich panel has a superior comprehensive heat transfer performance than X-type one.