Heat exchangers and radiators play a key role in the long-term and stable operation of equipment. 3D printing is used in the manufacture of heat exchangers and radiators to meet the development trend of products that are compact, efficient, modular, and multi-material. Especially for the processing of special shapes, integrated structures, thin walls, thin fins, micro-channels, very complex shapes, lattice structures, etc. 3D printing has advantages that traditional manufacturing technologies do not have.
In terms of 3D printing superalloy heat exchangers, the typical ones are the HEWAM project of AddUp, Sogeclair and TEMITsh, and the Inconel 718 material heat exchanger developed to ensure that the thin wall (<0.5mm) is free of leakage and thin fins (0.15mm) ).
Through the development of the project to try to incubate future industrial production prospects, the project team designed a heat exchanger appearance with a curvature that is suitable for various surfaces used in the conformal aerospace industry. The double curve design allows it The appearance is fitted to the curvature of the aircraft engine. In addition, thermal, fluid, and mechanical constraints are considered in the design to adapt the local geometry to the requirements for functional realization.
One boundary condition of the heat exchanger is that oil enters at 110 ° C, ambient air at -50 ° C, and the mass flow rate of the oil is fixed. The air mass flow rate is determined by the dynamic pressure of the air flow reaching the HX area and the pressure drop characteristics of the equipment. The purpose is to eliminate the 2200W oil circulation (32g / s ~ 2.4L / min) of HX by ensuring that sufficient air flows through the HX area.
The material selected for design is Inconel 718. Inconel 718 alloy is a precipitation hardening nickel-chromium-iron alloy containing niobium and molybdenum. It has high strength, good toughness and corrosion resistance in high and low temperature environments at 700 ℃. This material is more than 3 times heavier than aluminum and has lower conductivity, but for additive manufacturing, it exhibits more interesting characteristics. Using Inconel, the team can ensure that thin walls (<0.5mm) are not leaked and thin fins (0.15mm) are manufactured. Due to this, designing a heat exchanger with a good structure can achieve similar quality and performance as an aluminum AM shell.
The challenge of 3D printing heat exchangers comes from the need to maximize the surface area of a given volume without compromising the weight of the parts, which makes the design very complicated, and the complex design brings simulation challenges and brings 3D The challenge of printing files is too large, the creation and operation of the entire CAD geometry, simulation, and the establishment of print data is very time-consuming. AddUp, Sogeclair and Temisth have developed a specific methodology to ensure that the thermal requirements have mechanical constraints and the feasibility of additive manufacturing.
Another challenge that needs to be met is the need to ensure that sufficient airflow in the heat exchanger has a high heat transfer coefficient. Engineers consider that changes in air temperature (from -50 ° C to + 25 ° C) affect its density. Therefore, by increasing the channel width, the air acceleration is limited, thereby limiting the pressure drop. To maintain thermal performance, the design of the fins has an adaptive geometry along the air flow in order to account for changes in air velocity and channel size. The CAD modeling design of the entire heat exchanger needs to follow the DfAM additive design thinking rules, and check the consideration factors such as pressure resistance and leakage through mechanical simulation.
Heat exchangers are very suitable for manufacturing by additive manufacturing, but an attractive design is often not enough. According to the market observation of 3D Science Valley, this also includes mastering the basic principles of heat transfer / fluid mechanics, a deep understanding and combination of thermal fluid simulation and AM-additive manufacturing process, which is a convincing competition Required for sexual results.
The HEWAM project carried out CAD, CFD (Computational Fluid Mechanics) iteration and mechanical simulation, and then used the AddUp Manager software to ensure the feasibility of the 3D printing manufacturing process. The preparation of 3D printing includes: part construction direction selection, support settings, laser strategy, Process simulation and so on.
The combination of simulation and optimization is carried out in several aspects: local optimization of channels with fine fins; mesoscale optimization of different fin modes and channels of different sizes. It also includes the use of curved shapes for macro optimization to achieve better system integration.
The significance of the HEWAM project lies in its commercial potential. The aerospace industry has a wide range of thermal applications, including air conditioning, brake cooling systems, embedded cold plates for electronics, and thermal management of engines. In the future, with the increase in heat of aircraft electrical systems and motor thermal systems, in order to ensure the performance of light equipment, more and more customized solutions for heat exchange will be needed.