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Copper, due to its ease of machining and high thermal conductivity, is the most commonly used substrate for heat sink applications. This paper presents an experimental investigation of the effect of boiling-induced copper ageing on the heat transfer and critical heat flux (CHF) characteristics of flow boiling of water in a mini/micro-channel. Agein...
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... heat loss is then expressed as a function of the difference between the average wall temperature and ambient temperature ( T tw − T amb ). A plot of heat loss against ( T tw − T amb ) is made as shown in Fig. 3 . In order to evaluate the heat loss during twophase experiments where higher wall temperatures prevail, the linear fit obtained between heat loss and ( T tw − T amb ) is extrapolated. The same procedure can be found in literature [ 30-32 ]. The effective power supplied to the fluid is evaluated by subtracting the heat loss to ambient ...
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... on the copper surface before and after the Case-1 and Case-2 experiments. During the measurement, the copper block was orientated in such a way that the baseline of droplet as seen by the camera was parallel to the length of the channel. A schematic showing the arrangement of the test section during the contact angle measurement is presented in Fig. S3 (available in Supplementary Material) and a photograph of the arrangement is shown in Fig. S4 (available in Supplementary Material). The results of the contact angle measurement are presented in Fig. 8 and Fig. 9 . Fig. 9 shows that the average value of the contact angles at five locations along the length of the channel reduced from ...
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... It can also be seen that the second tests for 38 cm 3 /s flow rate (light green squares) and 47 cm 3 /s flow rate (light blue squares) are flipped, i.e., the second test boiling curve shifts to the right as compared to the first test for 38 cm 3 /s. Since heat transfer at 38 cm 3 /s flow rate has a significant contribution from nucleate boiling, the decreasing HTC in the second test can be attributed to the reduction in entrapped non-condensable gases that facilitates the nucleation on boiling surface [39] and aging phenomena [40]. ...
This paper presents an experimental characterization of liquid nitrogen (LN 2) flow boiling in additively manufactured minichannels. There is a pressing need of concerted efforts from the space exploration and thermal transport communities to design high-performance rocket engine cooling channels. A close observation of the literature gaps warrants a systematic cryogenic flow boiling characterization of asymmetrically heated small (<3 mm) non-circular channels fabricated with advanced manufacturing technologies at mass flux > 3000 kg/m 2 s and pressure > 1 MPa. As such, this work presents the LN 2 flow boiling results for three asymmetrically heated additively manufactured GR-Cop42 channels of 1.8 mm, 2.3 mm, and 2.5 mm hydraulic diameters. Twenty different tests have been performed at mass flux~3805-14,295 kg/m 2 s, pressures~1.38 and 1.59 MPa, and subcooling~0 and 5 K. A maximum departure from nucleate boiling (DNB)-type critical heat flux (CHF) of 768 kW/m 2 has been achieved for the 1.8 mm channel. The experimental results show that CHF increases with increasing LN 2 flow rate (337-459 kW/m 2 at 25-57 cm 3 /s for 2.3 mm channel) and decreasing channel size (307-768 kW/m 2 for 2.5-1.8 mm channel). Finally, an experimental DNB correlation has been developed with 10.68% mean absolute error.
... Therefore, with the continuous progress of electronic system technology and the increasing demand for information processing, a higher power consumption of electronic components has been promoted, and the technical requirements for high temperature operation and heat exchange of electronic components have been continuously improved [4]. However, when the heat source is highly concentrated in small integrated electronic components, the improper heat exchange management of the electronic components will lead to serious damage to the functions of the integrated circuits, or even complete shutdown [5]. The demand for high performance makes most electronic components operate under the limitations of existing heat exchange management technology. ...
With the rapid development of information science and technology, the demand for computer data processing is increasing, resulting in the rapid growth of the demand for high-power and high-performance solid-state drives (SSDs). The stable operation of SSDs plays an important role in ensuring the reliable working conditions and appropriate temperature of information technology equipment, rack servers, and related facilities. However, SSDs usually have significant heat emissions, putting forward higher requirements for temperature and humidity control, and consequently the heat sink system for cooling is essential to maintain the proper working state of SSDs. In this paper, a new type of thin heat pipe (THP) heat sink is proposed, and the heat transfer performance and cooling effect are experimentally and numerically studied. The numerical results are compared with experimental results, which showed an error within 5%. Single and double heat pipes were investigated under different input powers (from 5 W to 50 W) and different placement angles between 0° and 90°. The heat transfer performance of the new heat sink is analyzed by the startup performance, the evaporator temperature, and the total thermal resistance. The results show that the new double THPs with a 90° angle have a great advantage in the heat transfer performance of SSDs. The research is of great significance for the design and optimization of the SSDs’ cooling system in practical applications.
... It becomes stable in the last two tests. These changes may be attributed to the aging effect of the microchannel surface, which was also reported in [40,52,53]. The heat sink was cleaned with water and acetone before the assembly, whose surface is bright and clean, as shown in Fig. 3 (c). ...
... After several tests, even though the DO content was less than 1 ppm, the surface was oxidized at such a high temperature. The oxidized surface is more hydrophilic, thus inhibiting the nucleation and deteriorating the heat transfer [52][53][54]. Surface wettability may also cause a variation of the pressure drop. As the oxidation layer becomes dense, the flow and heat transfer characteristics no longer change. ...
Flow boiling of water in a copper foam fin microchannel (FFMC) heat sink is investigated experimentally. The heat sink has nine channels, which are 487 μm in width and 1061 μm in height. Experiments are conducted under a wide range of operating conditions: inlet temperature of 80 ℃, outlet pressures of 100 ∼ 134 kPa, mass fluxes of 76 ∼ 408 kg/m²s, effective heat fluxes of 0 ∼ 296.5 W/cm², and outlet qualities of -0.020 ∼ 0.874. Heat transfer and pressure drop characteristics of the FFMC are compared with those of a solid fin microchannel (SFMC) heat sink with the same geometry. The heat transfer coefficient of the FFMC is improved by up to 80 %, and the pressure drop is increased to 1.2 to 2 times. The critical heat flux of the FFMC is improved by 25% at the mass flux of 102 kg/m²s. Flow instability of the FFMC is mitigated significantly, including the reverse flow, the wall temperature fluctuation and the pressure drop fluctuation. Heat transfer mechanisms in the FFMC are analyzed with the help of the flow visualization. Nucleate boiling and thin film evaporation dominate in different Bo number ranges. The heat transfer coefficient of the FFMC first increases and then decreases with increasing the heat flux (also the quality) at low mass fluxes, and increases monotonically at high mass fluxes. The reduction of the wall temperature fluctuation and the pressure drop fluctuation are due to the transverse flow between the channels in the FFMC heat sink.
... However, the heat source (i.e., chip) becomes highly concentrated in miniaturized ICs. Consequently, the functionality of ICs is severely impaired or even totally being shut down when the heat is not properly managed [3]. For safe and effective operation of the microprocessor, the chip temperature needs to be maintained below a threshold value, therefore effective thermal management becomes a must-have issue beforehand [4,5]. ...
The heat sink with vapor chamber heat spreader has been the emerging design as it offers tremendous reduction in spreading resistance. However, this type of heat sinks suffer from the fin side temperature non-homogeneity, which hinders the heat transfer enhancement. The present study aimed to develop parallelogram fins integrated with heat pipes to increase the heat transfer performance of the heat sink with the vapor chamber heat spreader. The experimental and numerical investigations were performed on different heat sinks with different heat spreaders, including flat plate, vapor chamber, and vapor chamber combined with heat pipe. The air-cooled heat sink features a parallelogram fin configuration is proposed to tailor the temperature non-uniformity alongside the fins. The results showed that the overall thermal resistance of the heat sink with the vapor chamber and the vapor chamber combined with heat pipe spreader (no-cut fins) is about 50% and 55% lower than in the flat plate case. The proposed heat sink with vapor chamber combined with heat pipe spreader having a parallelogram fin structure offered about 61% reduction in thermal resistance and 45-50 °C reduction in chip temperature over the heat sink with flat plate heat spreader.
This study investigates the effect of the response surface method (RSM) on heat sinks designed in block types using various fluids. The RSM method is applied to the data obtained from heat sinks designed in block types using water, mono-nanofluids, and hybrid nanofluids placed in both vertical and horizontal directions. The data were collected under five different pressure boundary conditions and applied to 144 data sets. The results show that the R2 values for thermal resistance (Rth), CPU mean temperature (Tm) and Performance Evaluation Criterion (PEC) in horizontal arrangements are 99.21%, 99.21% and 99.37% respectively. The Box-Behnken method was used to analyze the design parameters and derive equations for seven different parameters: density, viscosity, specific heat, thermal conductivity, block thickness, block distances, and inlet pressure boundary conditions. Equations were used to determine the average CPU temperature, thermal resistance, and Performance Evaluation Criteria (PEC). The R2 values for vertically oriented geometries were 97.66%, 97.66%, and 98.45%, indicating a strong correlation between the results obtained from FLUENT and the ANOVA statistical results. The linear, square, and cubic effects of each variable significantly affected each solution. The study concludes that the RSM method has a significant impact on heat sinks with higher R2 values in horizontal arrangements and a higher distance between blocks
In the presented numerical study, the effect of the use of mono and hybrid (CuO/Water at 2% volume concentration and CuO + Fe/Water (1% CuO + 1% Fe)) type nanofluid in heat sinks designed in new geometric structures used to increase the processor cooling performance was investigated. The geometries used are circular, triangular, square, hexagonal, square, and hexagonal, and their perforated structures and their effects on a total of eight geometries were analyzed. In addition to these, the rate of improving the temperature distribution and heat transfer in the heat sink, i.e., the Performance Evaluation Criterion (PEC), was also examined. According to the results obtained, the lowest thermal resistance value is seen in the circular cross-section with Rth = 0.289 K/W, while the highest thermal, i.e., cooling performance is seen in the triangular perforated structure with Rth = 0.63 K/W and at the lowest pressure inlet condition. In terms of temperature distribution, the most uniform distribution was obtained between 311.82 and 308.98 K in the circular section. The most interesting result in terms of the results was the PEC = 1.4 for the triangular hole structure in the heat transfer improvement performance. The main reason for this is that the range of the temperature distribution shown is very high (319–311.5K).
