Thermal management of electronic devices using carbon foam and PCM/nano-composite (2023)

The high power of blade servers inside small data centers (DCs) can cause heat accumulation, which can degrade the performance of DCs. To address the problem of heat dissipation, we performed periodic experiments on a thermal management system based on a phase change material. The effects of time ratio, heating power, and cooling water temperature on the performance of thermal control and periodic stability were investigated. Information entropy reflects uncertainty by transforming a variable changes over time into a single parameter representing inhomogeneity of time. Herein, it was introduced as an evaluation index of thermal control performance. The results verified that the peak temperature of the heating surface can be maintained below 80°C for several periods under specific conditions. Additionally, the information entropy results of the experimental data reflected the thermal control performance of the system and validated the experimental conditions. Based on the experimental results and the corresponding information entropy analysis, we proposed a design strategy for the system parameters and a method for reducing the number of measuring points. The obtained results formed the basis for the thermal management design of the server level of DCs, other electronic equipment, and electric vehicles.

Effects of phase change materials (PCMs) filling height and copper foam pore densities on the cooling performance of a bio-PCM composite-based heat sink are investigated. In this respect, three filling height ratios of 1.0, 1.3, and 1.6 as well as three copper foam samples with pore densities of 35, 80, and 95 pores per inch (PPIs) are examined. Temperature profiles of the flat plate, the time required to reach specified temperatures, and the enhancement ratios at various temperatures and filling ratios are used to evaluate the thermal performance of the PCM composite-based heat sink. The investigation enables the determination of the optimal PCM filling height for maximum cooling performance of the heat sink. The results show that the optimal PCM filling height is 1.3 times the copper foam thickness and that a PCM/copper foam composite with 95 PPI pore density produces the best cooling performance with enhancement ratios of 1.54 and 1.44 under 10 and 15W heat loads, respectively.

Although lithium-ion batteries are increasingly being used to achieve cleaner energy, their thermal safety is still a major concern, particularly in the fields of energy-storage power stations and electric vehicles with high energy-storage density. Therefore, the battery thermal management systems (BTMs) have been extensively applied, among which phase-change-material (PCM)-based BTMs are being developed at a high growth rate. As highlighted here, because of the risk of battery thermal hazards such as thermal runaway or battery fires, meeting the prerequisites of PCM-based BTMs is imperative not only for aiding in heat dissipation in regular operation conditions, but also for facilitating thermal hazard mitigation in the case of extreme accidents. The thermo-physical properties of modified PCMs are compared, highlighting their thermal stability and flame retardancy. Structure-enhanced PCM-based BTMs are compared in terms of their structural design for hazard mitigation. Finally, future research directions based on critical thinking are proposed for the use of PCM-based BTMs in system resilience. We anticipate that this review will provide new insights and draw more attention to the material/system reliability of self-safety PCM-based BTMs in future designs, especially in terms of thermal safety issues.

This paper presents an experimental study on the thermal performance of a composite heat sink consisting of a bio-based phase change material and copper foam. The experiments are carried out at three different heat loads (10, 15, and 20W) using five copper metal foam samples with the same dimensions (10×9×0.3cm), porosity (98%), and pore densities of 20, 35, 60, 80, and 95 pores per inch (PPI). The thermal performances are evaluated using the temperature profiles, the time required to reach specific temperatures, and the enhancement ratios of the heat sinks. The results favor the PCM-Copper composite sample with 95 PPI because it took the longest time to achieve a constant temperature when compared to its other pore density counterparts. Also, for the same sample under 20W power input, the enhancement ratios are 1.29, 1.45, and 1.23 at critical temperatures of 50, 55, and 60°C, respectively.

This paper thoroughly reviews the development and characterization of carbon-based form stable organic phase change materials (FS-OPCMs) for latent heat storage applications. The O-PCMs such as paraffin, fatty acids, polyethylene glycols (PEGs), etc., suffer from poor thermal conductivity and flow ability in their molten state, which restricts their many applications. Carbon-based materials are seen as a promising and viable way to overcome these challenges. They have a very high thermal conductivity and can hold liquid phase change materials (PCMs) in their pores. This review provides comprehensive coverage of the carbon structures and their classifications, including carbon nanotubes (CNT), carbon nanofiber (CNF), expanded graphite (EG), graphene, graphene oxide (GO), carbonized industrial solid wastes, and other carbon-based materials that can be used as supporting porous materials in developing FS-OPCMs for thermal energy storage (TES) applications. In addition, the thermal and chemical performance of carbon-based FS-OPCMs is extensively investigated and given. The applications of such composites are also discussed and summarized. Finally, the potential of these materials for thermal energy storage is presented. This review provides an in-depth insight into the potential of carbon-based materials for latent heat thermal energy storage (LHTES).

To protect electronic devices and batteries from sharp temperature rise and thermal runaway, active/passive/hybrid thermal management using phase change materials (PCMs) shows prominent and promising potential to maintain them within an optimum temperature range. However, not all PCMs are suitable for practical applications owing to their undesirable thermophysical properties. Therefore, this paper focuses on the selection criteria of PCMs and various techniques for enhancing the thermal conductivity and improving the latent heat of fusion of PCMs. Over 200 PCMs as candidate covering the relevant operating temperature range of 0–100°C are presented and compared in terms of different selection criteria. Furthermore, a comprehensive review of PCMs employed in cooling of electronic devices and thermal management of power batteries is provided. Finally, future outlooks and research topics on physico-thermal properties enhancement for PCMs and thermal management technologies with PCMs for electronic devices and power batteries are proposed.

International Communications in Heat and Mass Transfer, Volume 98, 2018, pp. 155-162

Owing to enormously high surface area and high thermal conductivity, copper foam based heat sinks for electronic cooling are investigated in this paper. Copper foam1 with porosity 0.95 and pore density 15 pores per inch and copper foam2 with 0.97 porosity and pore density 35 pores per inch are used to investigate the performance of heat sinks filled with phase change material (PCM). Various configurations of heat sink with PCM volume fractions 0.0, 0.6, 0.7 and 0.8 are investigated under heat load of 8–24 W to figure out the optimum performance of the heat sink. Experimental results revealed that base temperature of the heat sink is reduced as the volume fraction of PCM is increased. Anyhow, discharging process is not affected significantly. Furthermore, copper foam1 (0.95 porosity) exhibited better heat transfer both in charging and discharging as compared to that of copper foam2 (0.97 porosity). Maximum temperature reduction of 9.81% was found for copper foam1/PCM at 8 W and PCM volume fraction of 0.8 when it is compared with copper foam2/PCM composite. For the same porosity, maximum reduction in base temperature was observed for 0.8 volume fraction of PCM at 16 W heat input. Finally, it is concluded that copper foam1/PCM composite impregnated with 0.8 volume fraction is an optimized configuration of heat sink.

Applied Thermal Engineering, Volume 111, 2017, pp. 271-279

In this paper, an experimental investigation is performed to study the effects of using nano/phase-change-materials (NPCM) as coolant for an electronic chipset in various scenarios that include both free and forced convection. Development of efficient cooling methods in electronic technology is significant mainly for enhancement of functionality and lifetime of electronic devices. Six different scenarios of cooling systems are conducted for an electronic chipset under various values of heat flux. The cooling scenarios include simple heat-sink (referred to HS in this paper), heat-sink that contains a phase change material (HS/PCM), and heat-sink that contains NPCM (HS/NPCM) in both free and forced convection. The PCM used in this study, Mn(NO₃)₂, is an inorganic salt-hydrate type; and the selected nanoparticles are Fe₃O₄ dispersed in the PCM by an ultrasound mechanism by a weight fraction of 1%. The steady and transient thermal behavior of the electronic chipset are investigated under different operating conditions by applying various heat fluxes from 1000 to 4000W/m². Results show that presence of the PCM and NPCM can decrease the steady temperature of the chipset up to 14°C and 10.5°C compared to that of the HS for both free and forced convection, respectively. Furthermore, it is observed that the HS/PCM has better cooling and time efficiency for longer period usage whereas the HS/NPCM is preferable in temporary and intermittent use.

Applied Thermal Engineering, Volume 128, 2018, pp. 966-972

In this Short Communication, the transient performance of a phase change material (PCM)-based heat sink filled with a copper foam was experimentally studied. Attention was paid to revealing the influence of filling height ratio of the copper foam on the performance. The effects of pore size of the copper foam and the heating power were also studied parametrically. The results showed that the PCM-based heat sink could inhibit the temperature excursions during the heating period, and that the performance could be improved almost monotonously with increasing the filling height ratio. However, the performance improvement was found to become saturated approaching the full-filling case, regardless of the pore size and heating power. A new parameter, i.e., the filling effectiveness, was defined to help make a trade-off analysis between the performance gain and cost saving. As can be assessed by the filling effectiveness, the 2/3 partial filling was demonstrated to be more economical than full filling because the save in cost of materials and system weight is obvious with only a negligible sacrifice in the gain of performance improvement. The results suggested that the partial filling strategy can be applied to attain a better comprehensive performance of PCM-based heat sinks.

International Journal of Heat and Mass Transfer, Volume 112, 2017, pp. 649-661

Efficient thermal management (TM) based on phase change material (PCM) is adopted for the cooling of portable electronic devices. PCM namely n-eicosane is employed to absorb thermal energy released by such electronics. Four different configurations of circular pin-fin heat sinks with fin thickness of 2mm, 3mm and 4mm including a no fin heat sink (used as a reference heat sink) were adopted. Pin-fins were made of aluminum due to light weight and good thermal conductivity to act as a thermal conductivity enhancers (TCEs). Pin-fin heat sinks of constant (9%) volume fraction of TCE are filled with four volumetric fractions of PCM to explore the best amount of PCM volume. A wide range of heat flux is provided at the heat sink base and the effect of fin configuration, PCM volume, latent heat phase, power densities, thermal capacity and thermal conductance are reported in this study. Three different critical set point temperatures (SPTs) are selected for this investigation. Enhancement ratios are reported against various PCM fractions to illustrate the thermal performance for passive cooling. The results show that 3mm fin thickness heat sink has best enhancement in operation for TM module controlling temperature of electronic devices.

International Journal of Heat and Mass Transfer, Volume 146, 2020, Article 118852

In this paper, experimental investigations are carried out to study the thermal performance of metallic foams impregnated with phase change material (PCM) based heat sinks for thermal management of electronics. Herein, RT-35HC with melting point 34–36 °C is chosen as PCM and copper foam1 (95% porosity), copper foam2 (97% porosity) and Iron-Nickel foam (97% porosity) are used as thermal conductivity enhancer. Various configurations of the heat sink are investigated for 5400 s each for charging and discharging processes under heat flux 0.8–2.4 kW/m² for PCM volume fractions 0.0, 0.6, 0.7 and 0.8. Results revealed that copper foam-based heat sink showed 5–6 °C less base temperature as compared to that of Iron-Nickel foam. While investigating the effect of foam porosity, copper foam with lower porosity (95%) has shown 11% less base temperature at the end of the charging cycle. It was also noticed that the maximum thermal conductivity enhancement of PCM was found to be 34 times for 95% porosity copper foam with the latent heat reduction of 37%. Copper foam1-PCM composite posed the maximum enhancement in operation time of heat sink 7.9 times more as compared to that of the empty aluminum heat sink. Copper foam -PCM composite with 95% porosity of foam with 0.8 vol fraction of PCM is best recommended configuration for the present experimental study.

Renewable and Sustainable Energy Reviews, Volume 59, 2016, pp. 550-582

Generally, the commercial and industrial electronic devices are required to be operated under 100°C.Therefore, there is a need to remove heat effectively from these devices under different loading conditions. Till now, Phase Change Material (PCM) based heat sinks are emerging as one of the effective techniques for removal of heat from the electronic devices. However, the low thermal conductivity of PCM situates a hindrance to the development. Thus, current research focuses on improving the thermal performance of PCM using thermal conductivity enhancer (TCE). At present internal fins, metallic foams and nano particles are mixed with PCM to enhance the performance of heat sinks. These are called as thermal conductivity enhancers. This article reviews methodologically various papers on the methods used for enhancement of PCM performance in cooling of electronic components. The effect of various parameters influencing the performance of the TCE-PCM based heat sinks are discussed in systematic order. The performance of these heat sinks under constant and variable thermal load are also evaluated. Out of these three TCE, metallic foams in heat sinks provides a higher surface area to volume ratio, good thermal conductivity and considerable weight advantage.