See How 3D Printing Can Help Counterflow Heat Exchangers Improve Heat Exchange Efficiency

- Dec 18, 2018-

Heat exchangers have been used for decades to transfer thermal energy from one fluid to another. The fluid can be either a liquid or a gas, or one can be a liquid and the other can be a gas, such as air. Heat exchangers are used in a variety of industries and applications – from automotive radiators to aerospace applications, such as engine oil cooling and jet fuel preheating, to power generation and computing applications. And 3D printing technology is changing the design and manufacturing methods of heat exchangers and heat sinks with its unique process characteristics.

In a constrained flow heat exchanger, there are three main heat exchanger classifications depending on the flow arrangement of the two fluids. In a cross-flow heat exchanger, the hot fluid and the cold fluid travel substantially perpendicular to each other through the heat exchanger. In a parallel flow heat exchanger, the two fluids enter the heat exchanger at the same end and travel parallel to each other to the other end. In a countercurrent heat exchanger, two fluids enter the heat exchanger from opposite ends.

One way to increase the efficiency of the heat exchanger is to increase the number of channels through which the fluid flows and to reduce the size of the channels. For a given heat exchanger length, the small channel size enables more complete transfer of thermal energy from the hot fluid to the cold fluid. Therefore, the design of the heat exchanger is essentially a cubic channel matrix arranged in rows and columns, wherein the number of rows and columns is several hundred. In this complicated heat exchanger structure, although the efficiency advantage of the countercurrent device is desirable. But until now, making this design is challenging.

Northrop Gramman Systems is developing an innovatively designed heat exchanger featuring a greatly simplified external piping, but this innovatively designed heat exchanger is difficult to construct with traditional manufacturing techniques. In particular, brazing or welding of the joints is difficult, especially considering that the materials involved are very thin, very small in size, and that the joints must be leak-proof. However, these structures are easily constructed by additive manufacturing techniques (also known as 3D printing). Additive manufacturing not only replaces the brazing or welding process, but also builds the heat exchanger channel matrix by additive manufacturing, and builds the entire heat exchanger assembly by additive manufacturing – including all sets, where a large number of headers are required Tubes become an effective way of manufacturing. We understand that it is worth noting that, through additive manufacturing, the passage does not have to be straight, and the entire heat exchanger can take almost any shape – including bending, twisting, warping and the like.

Additive manufacturing techniques enable the fabrication of alternating channels in counterflow heat exchangers, which is essentially impossible for conventional manufacturing techniques. The counterflow design of the alternating channels provides maximum heat exchanger efficiency, which minimizes the size and mass of the heat exchanger and reduces the fluid flow rate.

Northrop Grumman, one of the major aerospace vehicle manufacturers in the United States, has significant capabilities in electronics and systems integration, military bombers, fighter aircraft, reconnaissance aircraft, and military and civilian aircraft components, precision weapons, and information systems. Advantage.

Not only is Northrop Grumman developing innovative heat exchangers through 3D printing technology. Raytheon, another large US defense contractor, is also developing a 3D printing additive manufacturing process to enable the manufacture of phase change material (PCM) heat sinks. The basic structure of the radiator developed by Raytheon includes the lower case, the upper case and the internal matrix. The lower shell, upper shell and internal matrix structure are fabricated as a single component by additive manufacturing techniques. The internal matrix is designed to hold the space of the phase change material. The additive manufacturing process allows individual components to be integrated and manufactured together. The result is a 3D printed heat sink that is less expensive to manufacture and more robust than conventional heat sinks. Moreover, its internal matrix can have a more complex design to address specific issues such as heat dissipation of high power density components.

There are several main ideas for 3D printing in the manufacture of heat sinks: one is the alternative brazing mentioned in the text and combined with the use of phase change materials, one is to achieve very complex geometries. The application of very complex geometric aspects such as hyperbolic cross winding is of course more typical of the application of lattice structures.

And what is the impact and coverage of 3D printing in the industrialization of heat exchangers, not only depends on the 3D printing equipment, the price of materials, but also depends on whether the process quality can be consistently controlled, as well as standards and certifications. The perfection, and the most important thing is how to obtain a positive design breakthrough based on product function realization from the design side. Many companies have made progress in 3D printing heat exchangers and heat sinks. These include GE, Raytheon, Northrop Grumman, and Unison Industries in the aerospace industry; heat exchangers developed by HiETA Technologies and Renishaw in the automotive industry, and new high-efficiency heat developed by Conflux Exchanger ConfluxCore and aluminum radiators developed by Fiat Chrysler (FCA Automotive Group); microprocessor cooling solutions and thermal management systems developed by companies such as Microsoft, IBM, and Ebullient LLC in IT electronics.

It can be said that in the positive design dominated by additive thinking, heat exchangers and radiators are undergoing continuous innovation at the product design level. These innovations will enhance the efficiency of human thermal management in a commercialized way. And ability.