The escalating demands of modern electronics, driven by the exponential growth of data, communication, and the continuous drive for miniaturization, present a formidable challenge: thermal management. As power densities in electronic devices surge, so do the energy consumption and coolant requirements of traditional cooling systems.
This creates a significant environmental impact, highlighting the urgent need for new technologies that can achieve more sustainable heat extraction, thereby reducing both coolant usage and energy consumption. In this context, microchannel heat exchangers have garnered considerable attention for their compact structure and superior heat transfer performance over the past two decades.
Manifold Microchannel (MMC) Heat Sinks: A Bio-Inspired Solution
A promising advancement in this field is the development of Manifold Microchannel (MMC) heat sinks. These innovative designs integrate manifold flow dividers directly onto microchannels. This strategic integration ensures a highly uniform distribution of the working fluid and significantly shortens the flow path, remarkably mimicking the efficiency of the blood circulation system within the human body.
Early experimental and numerical studies on single-phase MMC heat sinks have already demonstrated their impressive advantages. Compared to traditional heat sinks, MMC designs show substantial reductions in both pump power requirements and thermal resistance, making them a more efficient and less energy-intensive cooling solution.
Experimental Setup for Flow Boiling Analysis
To rigorously test the performance of these advanced heat sinks, a specialized experimental setup was constructed. This setup, building upon previous research, features a key component: an MMC test module. Deionized water serves as the working fluid. To eliminate non-condensable gases, the water is initially heated to boiling in a storage reservoir.
The degassed water then embarks on a carefully controlled journey through the system. It is propelled by a gear pump, its flow rate precisely measured by a mass flow meter. The fluid then passes through a series of preheaters: a first one heated by a high-temperature bath, followed by a second electric preheater, before finally entering the test module itself. After the heat transfer or boiling process occurs within the test module, the working fluid is efficiently cooled by a condenser and returned to the storage tank, completing the closed loop.
Anatomy of the MMC Test Module
The MMC test module itself is meticulously designed, primarily composed of a glass-based cover plate, a glass-based manifold plate, and a copper-based microchannel bottom block. It also incorporates four inlet and outlet modules. These specific modules are crafted using a nano-ceramic resin material, chosen for its exceptional toughness and high-temperature resistance. By carefully stacking the glass plates onto the copper-based microchannel, the flow path of the water is strategically altered and shortened, optimizing its interaction with the heat-generating surface.
Computational Domain and Simulation Methodology
For computational analysis, the entire MMC heat sink, encompassing its temperature measurement points, microchannels, and the copper block above the manifold channel, is treated as a single computational domain. Since the manifold baffles and cover plates are made of glass, which possesses significantly lower thermal conductivity than copper or water, they are simplified and considered as insulated walls for the manifold channel in the simulations.
The boundary conditions for the inlet and outlet are set to constant velocity and constant pressure, respectively, accurately simulating pump-driven flow conditions. No-slip boundary conditions are applied to all fluid domain walls, representing the interaction between the fluid and the solid surfaces. The bottom wall of the solid domain is subjected to a constant heat flux condition, calculated from the effective heat flux observed in physical experiments. All other solid walls are considered insulated. Recognizing that heat loss is less pronounced at higher mass fluxes, simulations are focused exclusively on conditions with varying inlet subcooling and heat flux, maintaining a consistent mass flux.
To ensure the accuracy of the simulations, a detailed grid independence study was performed. Comparing temperature distributions across different grid densities, it was observed that finer grids yielded very similar and reliable temperature distributions on the computational domain’s bottom surface. Based on these findings, a specific grid density was selected for all subsequent simulations. These complex flow boiling cases were implemented using a powerful computing node, with each simulation requiring several days to reach a quasi-steady state, indicating a stable and representative flow time.
This meticulous approach, combining innovative design, detailed experimental validation, and robust computational modeling, is crucial for advancing thermal management solutions that are both highly efficient and environmentally sustainable for the future of electronics.