A Novel Approach to Low Profile Heat Sink Design

Released in 2018, China’s Standards of English Language Ability (CSE) set a benchmark for language education and assessment in China, integrating with international standards. This study investigates whether CSE assessment literacy (understanding and applying CSE standards in assessment practice) enhances Language Assessment Literacy (LAL) among 233 university EFL teachers in China. Using a self-designed questionnaire assessing current LAL and CSE assessment literacy, the findings indicate that the teachers’ self-assessed LAL, classified into high, moderate, and low LAL profiles, was generally unsatisfactory. Awareness of the principles was highest in teachers with a moderate LAL profile and was minimal in teachers with a low profile. Proficiency in “CSE Background,” “Competence Classification,” and “Table Scales” was closely linked to elevated LAL profiles. Specifically, “CSE Background” improved LAL across low and moderate profiles, while “Competence Classification” and “Table Scales” mainly benefited the moderate profile, informing effective LAL and CSE training strategies.

Reliable and efficient cooling solutions for portable electronic devices are now at the forefront of research due to consumer demand for manufacturers to downscale existing technologies. To achieve this, the power consumed has to be dissipated over smaller areas resulting in elevated heat fluxes. With regard to cooling such devices, the most popular choice is to integrate a fan driven heat sink, which for portable electronic devices must have a low profile. This paper presents an experimental investigation into such low profile cooling solutions, which incorporate one of the smallest commercially available fans in series with two different heat sink designs. The first of these is the conventionally used finned heat sink design, which was specifically optimized and custom manufactured in the current study to complement the driving fan. While the second design proposed is a novel “finless” type heat sink suitable for use in low profile applications. Together the driving fan and heat sinks combined were constrained to have a total footprint area of 465 mm2 and a profile height of only 5 mm, making them ideal for use in portable electronics. The objective was to evaluate the performance of the proposed finless heat sink design against a conventional finned heat sink, and this was achieved by means of thermal resistance and overall heat transfer coefficient measurements. It was found that the proposed finless design proved to be the superior cooling solution when operating at low fan speeds, while at the maximum fan speed tested of 8000 rpm both provided similar performance. Particle image velocimetry measurements were used to detail the flow structures within each heat sink and highlighted methods, which could further optimize their performance. Also, these measurements along with corresponding global volume flow rate measurements were used to elucidate the enhanced heat transfer characteristics observed for the finless design. Overall, it is shown that the proposed finless type heat sink can provide superior performance compared with conventional finned designs when used in low profile applications. In addition a number of secondary benefits associated with such a design are highlighted including lower cost, lower mass, lower acoustics, and reduced fouling issues.

This paper presents the novel hooked loop antenna (HLA) concept. The HLA is suitable for Bluetooth headset applications and it has been implemented into the SonyEricsson HBH-60 headset. Advantages of the HLA are large bandwidth, low profile and low losses. The HLA is a half wavelength long loop placed above a ground plane. Simulations show large bandwidth for small ground planes and low profiles. Bandwidths of 5% for VSWR<2 can easily be achieved on a 35 by 17 mm large ground plane using a HLA of height 4 mm given the center frequency 2500 MHz. The HLA is relatively insensitive to nearby metal objects, thereby making efficient use of the ground plane area possible. The HLA is also tolerant to mechanical reshaping, an important feature for small products such as headsets where the antenna must conform to the shape of the product.

The increasing heat flux densities from portable electronics are leading to new methodologies being implemented to provide thermal management within such devices. Many technologies are under development to transport heat within electronic equipment to allow it to be transported into the surroundings via conduction, natural convection and radiation. Few have considered the approach of implementing a forced convection cooling solution in such devices. This work addresses the potential of a low profile integrated fan and heat sink solution to electronics thermal management issues of the future, particularly focusing upon possible solutions in low profile portable electronics. We investigate two heat sink designs with mini channel features, applicable to low profile applications. The thermal performance of the heat sinks is seen to differ by approximately 40% and highlights the importance of efficient heat sink design at this scale.

Space and power constraints in many contemporary electronic systems place a greater importance than ever on efficient thermal management solutions. This paper investigates the performance and optimisation of air cooled heat sinks suitable for deployment in compact electronic devices. The heat sinks examined have circular footprint, with air flowing from the centre, radially outwards through radially aligned channels. Heat sink height is examined through experiments which were performed on heat sinks with high and low fins, with two and three dimensional flow and heat transfer phenomena respectively. In both cases the effect of angular fin spacing is investigated to determine optimum fin spacing for a range of heat sink pressure drops. Heat transfer correlations from literature which were originally developed for parallel finned heat sinks are compared with the experimental data. The main findings of the paper are that the performance of the high profile two dimensional heat sink is more sensitive to fin angular displacement than low profile three dimensional heat sinks. The parallel fin correlations from literature were found to predict the performance of the three dimensional heat sinks more accurately than the two dimensional heat sinks.

Reliable and efficient cooling solutions for portable electronic devices are now at the forefront of research due to consumer demand for manufacturers to downscale their existing technologies. The power required for these technologies now has to be dissipated over smaller areas resulting in elevated heat fluxes. The most popular choice among engineers in terms of cooling solutions is to integrate a fan with a heat sink and for portable electronic devices this involves the use of a low profile solution. In this paper an experimental investigation on the thermal performance of a finned and finless heat sink integrated with an axial fan, for the purpose of cooling a microchip, is presented. The objective is to characterise the performance of each heat sink in terms of thermal resistance and to develop an understanding of the flow structures in such systems. One of the smallest commercially available fans is used in conjunction with each heat sink giving a total footprint area of 465m2 and profile height of 5mm. Thermal resistances are measured over a range of fan speeds and detailed velocity measurements were taken of the flow within the heat sinks using Particle Image Velocimetry (PIV). The thermal analysis results indicate that the thermal resistance of the system is of order 30 deg C/W for both heat sinks. However, the finless heat sink resulted in slightly lower values over a range of intermediate fan speeds. Hence, indicating that the maximum heat transfer density, for a range of fan speeds, can be achieved with a finless heat sink. The results also define the limiting heat fluxes that can be dissipated in low profile miniature applications.

High-aperture-efficiency antennas are very desirable for applications such as satellite communications and automotive radars, as they can provide the narrowest beams at the smallest footprint. However, typical high-aperture-efficiency antennas are cumbersome to design, costly to fabricate, and do not exhibit a low profile. This paper proposes to engineer the resonances of simple 2D transmission-line grids, based on photonic crystal concepts, to achieve high-aperture-efficiency radiation. It was found that these grids can be realized with extremely low profiles, and they require the smallest possible real estate for a given beam size. This design can be a desirable compact antenna solution for the aforementioned applications of satellite communications and automotive radars, among a few others.

Cooling of Laser Slab by Forced Convection through a Heat Sink

Heat exchangers are important structures widely used in power plants, food industries, refrigeration, and air conditioners and now widely used in computing systems. Finned type of heat sink is widely used in computing systems. The main aim of the design of the heat sink is to maintain the optimum temperature level. To achieve this goal so many geometrical configurations are implemented. This paper presents a characterization of radially curved fin heat sink under natural and forced convection. Forced convection is studied for the optimization of temperature for better efficiency. The different alternatives in geometry are considered in characterization are heat intensity, the height of the fin and speed of the fan. By recognizing these alternatives the heat sink is characterized by the heat flux usually generated in high-end PCs. The temperature drop characteristics across height and radial direction are presented for the constant heat input and air flow in the heat sink. The effect of dimensionless elevation height (0 ≤ Z* ≤ 1) and Elenbaas Number (0.4 ≤ El ≤ 2.8) of the heat sink were investigated for study of the Nusselt number. Based on experimental characterization, process plan has been developed for the selection of the similar heat sinks for desired output (heat dissipation and temperature distribution).

The drive for small and compact electronic components with higher processing capabilities is limited by their ability to dissipate the associated heat generated during operations, and hence, more advanced heat sink designs are required. Recently, the emergence of additive manufacturing techniques facilitated the fabrication of complex structures and overcame the limitation of traditional techniques such as milling, drilling, and casting. Therefore, complex heat sink designs are now easily realizable. In this study, we propose a design procedure for mathematically realizable architected heat sinks and investigate their performance using the computational fluid dynamics (CFD) approach. The proposed heat sinks are mathematically designed with topologies based on triply periodic minimal surfaces (TPMSs). Three-dimensional CFD models are developed using the starccm+ platform for uniform heat sinks and topologically graded heat sinks to study the heat transfer performance in forced convection domains. The overall heat transfer coefficient, surface temperature, and pressure drop versus the input heat sources as well as the Reynolds number are used to evaluate the heat sink performance. Moreover, temperature contours and velocity streamlines were examined to analyze the fluid flow behavior within the heat sinks. Results showed that the tortuosity and channel complexity of the Diamond solid-networks heat sink result in a 32% increase in convective heat transfer coefficient compared with the Gyroid solid-network heat sink which has the comparable surface area under the examined flow conditions. This increase is at the expense of increased pressure drops which increases by the same percentage. In addition, it was found that expanding channel size along flow direction using the porosity grading approach results in significant pressure drop (27.6%), while the corresponding drop in convective heat transfer is less significant (15.7%). These results show the importance of employing functional grading in the design of heat sinks. Also, the manufacturability of the proposed designs was assessed using computerized tomography (CT) scan and scanning electron microscopy (SEM) imaging performed on metallic samples fabricated using powder bed fusion techniques. A visible number of internal manufacturing defects can affect the performance of the proposed heat sinks.

The rapid advancement in technology of microprocessors has led electronics thermal system designers to pay increased attention to the folded fin heat sink. The advantages of using a folded fin heat sink are light weight, low profile, and small footprint. There are three manufacturing methods for bonding the folded fin to the base of heat sink: adhesive bonding, soldering, and brazing. Brazing is a high temperature process which takes place at around 550/spl deg/C. The major concern with using the brazing process to manufacture heat sinks is dimensional deformation. The adhesive process, on the other hand, requires only sub 200/spl deg/C or room temperature curing process. However, its thermal contact resistance at the joint is higher than others. Solder bonding is an alternative solution to above problems. The soldering process requires much lower temperature, less than 200/spl deg/C, yet it gives excellent thermal contact and bond strength at the joint. This paper presents the theoretical study of thermal contact resistance at the joint between the folded fin base and the spreader plate of heat sink, and also presents the experimental results which support this theory.

For improvement of heat dissipation performance, heat analysis is conducted on the newly designed heat sinks under two convection conditions by using computational fluid dynamics(CFD). Three types of heat sink, plate, wave and top vented wave, are used, and convection conditions are the variations of gravity direction at natural convection and of fan location at forced convection. The results of analysis showed that the heat resistances of top vented wave heat sink were <TEX>$0.17^{\circ}C$</TEX>/W(forced convection) and <TEX>$0.48^{\circ}C$</TEX>/W(natural convection). In the case of natural convection, gravity direction affected heat flow change, and protection against heat performance was superior in case of z-axis gravity direction. Under the forced convection, all the heat sinks revealed superior thermal characteristics in the fan position of z-axis rather than y-axis. In this study, it was observed that the top vented wave type heat sink showed the best ability of heat radiation comparing with the others.

CO_2 is recognized as one of the most suitable natural working fluid for compression heat pump to heat cold water to hot temperature region. But the coefficient of performance (COP) for cooling is not high. This is because the temperature of the working fluid discharged from compressor is so high to the heat sink that is often the outside air temperature. When a low temperature heat sink is available, cooling for the air conditioning by CO_2 heat pump can be realized. In this study, river water, underground water and ground are supposed as heat sink. When the low temperature heat sink is used and expansion at 25 C is realized, cooling COP is improved and shows the value 5.89 for single stage compression and 6.67 for two stage compression with flash cycle. These values are very close to those obtained by the conventional system that uses R410A.

An Experimental investigation on the thermal performance of copper with aluminium based finned heat sinks for electronics cooling system was studied. The heat sinks have different material proportions containing major constituent of aluminium and minor constituent of copper. Considered with straight finned heat sink for the experiments for its easiness in fabrication and efficient heat transfer properties. The observational results for aluminium with copper alloy are compared with pure aluminium heat sink. Heat sink geometry, fin pitch and its height were taken from the commercially available heat sinks. In this research work best heat sink geometry is chosen and cooked up with different volume of copper added with aluminium. Selected four different spots of heat sinks and the temperature raising characteristics were measured for natural convection. also the temperature is raised to a fixed temperature and the temperature lowering characteristics were measured in forced convection as the air circulation takes more heat to keep the heat sink temperature within the desired level.

In the present study, we examined whether profiles of temperamental features in adolescence (a) predict internalizing and externalizing symptoms in early adulthood, and (b) differ in family processes (i.e., cohesion, conflict) during early adolescence. Participants were 662 youth (72% male; 76% White). Mothers reported on family cohesion and conflict during participants’ early adolescence (ages 12–14, Time 1). Youth completed measures of temperament in middle adolescence (ages 16, Time 2), and of their symptoms in middle adolescence (Time 2), late adolescence (age 19, Time 3), and early adulthood (age 22, Time 4). Latent profile analysis identified three temperamental profiles: low positive mood, low rhythmicity, and well-regulated. Individuals in the low rhythmicity profile reported higher levels of externalizing symptoms compared to the well-regulated profile. No between-profile differences were found for internalizing symptoms. Mothers of youth in the low positive mood and low rhythmicity profiles reported higher levels of family conflict than the well-regulated profile. In addition, mothers of youth in the low positive mood profile reported lower levels of family cohesion than the well-regulated profile. Research implications of the study findings are presented.