Also to be considered when deciding to use the technology: nonthermal benefits including little to no impact on weight, little to no impact on structural strength, and passive operation with no power consumption and long life. In terms of performance gains, these plates have demonstrated keffective ranges between 500 and 1,200 W/m-K, depending primarily on length. The base of the mounting frame was coupled with the higher-level thermal solution, and the discrete electronics were mounted on the vertical face. A practical example of such a solution used in a radar application is shown in Figure 1: In this instance, several heat pipes were strategically positioned and implemented vertically into the T-shaped design. When embedding heat pipes into a structural heat spreader, the resulting solution is known as a high thermal conductivity plate. The internal wick structure passively pumps the fluid back to the evaporator section using capillary force (See Figure 1). The fluid gives up its latent heat at the condenser, which is coupled to the system’s heatsink. From here, an internal pressure gradient is created, rapidly transporting the fluid vapor to colder regions of the heat pipe. This section is commonly known as the evaporator. Heat pipes are closed-loop devices that are implemented near the critical electronics to promote fluid vaporization. In rugged systems, the most common passive two-phase heat-transfer devices are embedded heat pipes. By utilizing the latent heat of vaporization, one can achieve heat transfer rates in an order of magnitude greater than metallic conduction. To combat this issue, passive two-phase heat transfer can be considered. Lower k-values lead to local hot spots and failures well before the heat gets to the primary cooling solution. In many cases, the challenge is to manage the local heat flux with highly efficient heat transfer to the next-level thermal assembly – in this case, the liquid loop.Īluminum spreaders are often used due to weight and producibility considerations however, they are limited in conductive heat transfer by their ~180 W/m-K thermal conductivity (k). As electronics and power amplifiers increase in power densities, the need for more advanced heat spreading becomes critical. To break down the challenge and technology options, three areas of the overall thermal-management system (TMS) must be examined: local, high-heat flux electronics the systems liquid loop and the ultimate heat-rejection system.ĭiscrete electronics are a key piece of a radar’s functionality. The thermal-management system must therefore be robust and high-performance. The problem is amplified when adding in mechanical requirements (often vehicle-mounted or requiring rotation/movement to enhance coverage) and environmental requirements (large range of operating temperatures, MIL-STD-810-G requirements, etc.). Losses in the system can result in waste heat ranging from tens to hundreds of kWs, primarily from discrete electronics throughout the antenna and control system. The thermal challenge for large-scale radar systems can be highly complex. There exist a number of practical solutions to expand thermal capacity while staying mindful of size, weight, and power (SWaP) considerations. As the demand for increased distance in coverage grows, more electronics are used, with the resulting waste heat becoming a primary challenge for designers. national security, giving troops advanced abilities to detect and combat enemy strikes. Large-scale radar systems are critical to U.S.
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