In addition, the measured transient response against the injected slow but high energy 4 kV surge pulse through traditional GDT protector and fabricated EMP protection configuration was compared. For the surge pulse absorption characteristic through a traditional GDT protector, its residual voltage is 688 V because the slower surge pulse can be attenuated through the traditional GDT protector. A further reduction of residual voltage is observed when the 4 kV surge pulse is injected to our proposed MBPF EMP protection configuration. A residual voltage of 396 V is observed, which proved the better suppression ability in our proposed MBPF EMP protection configuration. The injected pulse and residual voltage behavior of the traditional and proposed MBPF EMP protection configuration are presented in Table 1. It infers that the proposed MBPF EMP protection configuration exhibits the better ESD and surge suppression performance as compared to the traditional EMP protector. The residual voltage of 511 V and 396 V are observed against the injected 6 kV ESD pulse and 4 kV surge pulse, respectively. This demonstrated that our proposed MBPF EMP protection configuration has great potential for use in EMP protection application.
A new power device structure is proposed, conceived to operate in a high temperature, harsh environment, for example within a motor drive application down hole, as an inverter in the engine bay of an electric car, or as a solar inverter in space. The lateral silicon power device resembles a laterally diffused MOSFET (LDMOS), such as those implemented within silicon on insulator (SOI) substrates. However, unlike SOI, the Si thin film has been transferred directly onto a semi-insulating 6H silicon carbide (6H-SiC) substrate via a wafer bonding process. Thermal simulations of the hybrid Si/SiC substrate have shown that the highthermalconductivity of the SiC will have a junction-to-case temperature approximately 4 times less that an equivalent SOI device, reducing the effects of self-heating. Electrical simulations of a 600 V power device, implemented entirely with the silicon thin film, suggest that it will retain the ability of SOI to minimise leakage at high temperature, but does so with 50% less conduction losses.
Abstract: Flexible vertical InGaN micro-light emitting diode (LED) arrays have been fabricated and characterized for potential applications in flexible micro-displays and visible light communication. The LED epitaxial layers were transferred from initial sapphire substrates to flexible AuSn substrates by metal bonding and laser lift off techniques. The electrical characteristics of flexible micro-LEDs degraded after bending the devices, but the electroluminescence spectra show high stability even under a very small bending radius 3 mm. The highthermalconductivity of flexible metal substrates enables highthermal saturation current density and high light output power of the flexible micro-LEDs, benefiting the potential applications of flexible high-brightness micro-displays and high-speed visible light communication. We have achieved ~40 MHz modulation bandwidth and 120 Mbit/s data transmission speed for a typical flexible micro-LED.
A BAT ingot was prepared by melting at 1,073 K for 4 h with high purity (99.999%) Bi, Sb, and Te granules in an evacuated quartz ampoule. The ingot was crushed into powder and sieved to obtain < 75-μm-diameter particles. The Bi 0.5 Sb 1.5 Te 3 powder was dry-mixed with Cu(OAc) 2
The single-pinch design of the oil bubble chip was capable of producing monodispersed, triacetin oil covered, DSPC, DSPE-PEG2000-coated air bubbles for several hours non-stop as shown in Figure 4.2. This produc- tion stage was relatively easy to reproduce. Also, high production rates (>50 000 bubbles per second) have been achieved with the single-pinch design using low viscosity heptane (386 µPa s) as the oil and 5 % Dreft desolved in the water as a surfactant. The results with heptane were very difficult to reproduce. The resulting bubbles in both cases were unstable in time meaning that most of the bubbles had already disappeared or coalesced in less than one minute.
Abstract: Use of Nanofluids is widely adopted to enhance the thermal performance of conventional fluids. Numerous experiments have been done on Nanofluid to increase the heat transfer in which different nanoparticles and base fluids are selected. Here, two different nanoparticles (copper oxide (CuO) and titanium dioxide (TiO2)) with 1-5% by volume are introduced in six different base fluids to make Nanofluids, and then thermal property of Nanofluid is inspected. Two distinct correlations are used to investigate the thermal property of Nanofluids of which one is theoretical and other is experimental. Results are compared with both the correlations which shows that CuO/Benzene Nanofluid is better than TiO 2 /Benzene for heat
There are almost 20% or more losses due to improper insulation. Health hazard associated with improper insulation like electrocution and ozone depletion potential. This project will address the recurrent issue of energy losses due to poor insulation. The thermalconductivity of many of our locally available woods will be determined. Traditionally, the design field has been identified with particular end products, e.g., mechanical design, electrical design, ship design. In these fields, design work is largely based on specific techniques to foster certain product characteristics and principles.
The ability of granular activated carbon (GAC) to adsorb large mass of refrigerant gases makes it ideal for use in thermal compressor. In order to make thermal compressor economically viable, the size must be reduced and for that reason thermal responses should be increase as much as possible during heating and cooling process. This paper investigates the effect of GAC bed density on the thermal transient responses when a sudden change in temperature is imposed on wall of a test sample reactor. The test sample consists of 1” OD stainless steel with 0.71 [mm] thickness and 200[mm] length that is loaded with compacted granular activated. The granular carbon used is 208C (coconut shell base) with 13×30 mesh size and provided by ‘Chemviron Carbon Company’. To find the heat transfer coefficient of the contact wall/packed carbon (h) and packed bed thermalconductivity (k) a numerical inverse heat conduction method is used in conjunction with an iterative process based on minimizing the Mean Square Error (MSE) from measured temperatures. Experimental work is carried out by measuring the wall and centre temperatures of submerged sample in a temperature controlled water bath at around 85 [ o C]. Five samples with the packed bed density ranging from 500 [kg/m 3 ] to 800 [kg/m 3 ] were tested and the results show a quasi-linear increase of both thermalconductivity (k) and heat transfer coefficient of the contact wall/packed carbon (h) with the packed bed density: 0.15 [W/m.K] < k < 0.45 [W/m.K] and 150 [W/m 2 .K] < h < 1400 [W/m 2 .K].
As mentioned in the background of the study, thermoelectric materials with high figure of merit which have high electrical conductivity, high Seebeck coefficient, as well as low thermalconductivity are in great need but as a family of possible good candidate materials for TE exposition, the literature on electronic properties of PdX 2 (where X is either S, Se, or Te) for either bulk phase or monolayer
The investigations indicate that the greatest stress appears on the upper end of the piston and stress concentration is one of the main reasons for fatigue failure. On the other hand piston overheating-seizure can only occur when something burns or scrapes away the oil film that exists between the piston and the cylinder wall. Damaged or broken parts are generally too expensive to replace and generally are not easily available. So to avoid this problem it needs design of a new part the main requirement of a piston is a good sealing of the cylinder. The Second is that the weight of the piston and the entire crank mechanism is a minimum, particularly for high speed machines, in order to reduce the inertia force and to improve thermal efficiency.
In the formulation, manufacture and supply of conformal coatings, thermal pastes, encapsulants, cleaners and lubricants, we have the solution. Through collaboration and research, we’re developing new, environmentally friendly products for many of the world’s best known industrial and domestic manufacturers – always to ISO standards. Combine this unique ability to offer the complete solution with our global presence and you have a more reliable supply chain and a security of scale that ensures you receive an exemplary service.
With these composite features, Al-SiC is an advanced packaging material for high technology thermal management. Al-SiC having wide range of metallic and ceramic substrate and plating materials used in microelectronic packaging for aerospace, automotive, microwave applications. Metal matrix composite allows for a new packaging technology that can replace traditional W-Cu, Mo, Mo-Cu, AlN, AlSi, and Al2O3. Aluminium matrix composites find wide applications in the present industrial scenario due to their desirable properties.
Due to unpredictable and unstable nature of solar radiation, it becomes very difficult to satisfy the gap between supply and demand of electricity. The only solution to this problem is to have storage in the system which can satisfy the demand regardless of unavailability of radiation. In storage, the extra energy that is not required, is collected and used it during hours when sunlight is not ample to satisfy the demand. Thermal storage can also be used for process application where a waste heat can be stored in thermal storage and used when it equired. Table 1.1 shows the advantages of using thermal
In order to validate the thermal simulation, a Netzsch Heat Flow Meter HFM 436/3/1E was used to measure the thermalconductivity of a glass fibre blanket, with the simulation aiming to model a glass fibre geometry that is representative of the glass fibre blanket. This required the use of a 30cm by 30cm square of the glass fibre, with a thickness of 1cm. As this would involve a very large number of fibres, the simulation version used a significantly smaller geometry of the same thickness.
The electrical, thermal and mechanical properties of functionally graded materials vary with microstructure and composition. Consequently it is very important to know quantitatively the properties of composites for the design of functionally graded materials. However, few methods of quantitative and theoretical evaluation for material properties on wide compositional range have been established. In this research, a method that estimates the material properties of composites directly from their microstructure assisted with ﬁnite element analysis was investigated. As an example of the estimation of material properties, the thermalconductivity of Mo ﬁber-Cu matrix composites has been evaluated. Calculated results of thermalconductivity are well in agreement with the experimental data measured by using a laser ﬂash apparatus and the smallest deviation is 1.9%. The ﬁnite element analysis using a metallographic model is a very accurate method for estimation of composite properties.
vol.% CNT/Cu composites at 650°C is not well understood. We propose that it may be related to the segregation of CNTs at the Cu grain boundaries resulted from the matrix grain growth, which can be explained via a schematic diagram of the distribution of CNTs at the Cu grain boundary displayed in Fig. 5 in combination with the microstructural observations. After the composite is fully densified, the growth of matrix grains occurs when con- tinuously increasing temperature (Fig. 5a, b). The grain growth induces the grain rearrangement that leads to the redistribution of CNTs at the grain boundary. As the grain size becomes larger, the volume of grain boundary decreases, and some ‘‘redundant’’ CNTs segregate at the juncture of grain boundary (Fig. 5d). It is well accepted that the phonon–phonon Umklapp scattering makes the major contribution to the thermalconductivity of CNTs . The segregation of CNTs can evoke the intensive tube–tube interactions that can severely suppress Umklapp scattering. The thermalconductivity is thus remarkably decreased. Whereas a low CNT content can effectively avoid the segregation of CNTs during such grain rear- rangement process because the most of ‘‘redundant’’ CNTs can fill up the initial CNT-free grain boundary (Fig. 5f). Hence, only a slight decease in thermalconductivity is observed for the composite with 5 vol.% CNTs at 650°C. The increase in holding time also leads to the similar results, as shown in Fig. 4, with the increase in holding time from 5 to 10 min, there is a moderate decease in thermalconductivity. As clear, the effect of holding time is small compared to that of sintering temperature. Although, in most cases, the addition of CNTs can inhibit the matrix grain growth during the sintering process due to the pin- ning effect of the CNTs , the present analyses indicate that this pinning effect of CNTs can be conquered if con- tinuously increasing sintering temperature or prolonging holding time after accomplishing the materials densifica- tion. The grain rearrangement can further influence the thermal properties of the composites. However, the further experiments at higher temperature and higher CNT content, which combine the microscope observations, such as TEM or HRTEM studies to carefully examine the presence of CNTs segregation, are necessary for the evaluation of the above explanations.
ments CFD to characterize the performance of carbon composite and copper heat sinks on the heat transfer in a computer CPU. The work of  utilizes CFD to perform trade studies on the modeling of finned heat sinks, while  has married experimental and CFD analysis to quan- tify the effects of heat sinks and base plates on heat tran- sfer behavior. Finally the work of  performs CFD and presents heat transfer correlations for the optimization of fin heat sinks. At a desk-top computer level, CFD has been used to study the heat transfer in computer chassis and computer box such as the work in  which focus- es on computer chassis heat transfer performance. The study of  implements CFD to investigate PCB heat transfer in a computer. The study of  investigates computer heat transfer and cooling using a heat-pipe. More generic analyses of using CFD to electronic sys- tems are given in the work of [12-14], wherein system’s level analysis is performed using CFD to gain insight on heat transfer and thermal performance of various elec- tronic devices, ranging from hand-held devices to desk- top computers. The tutorial offered by  allows the novice to gain insight on how to use electronics pac- kaging design lay-out strategies to realize more effective heat transfer flow field patterns. In the arena of rack mounted servers, several pertinent CFD based investiga- tions have been carried out over the last decade or so. The most noteworthy of these is the study of , where- in a CFD tool is implemented to study the temperature distribution in rack mounted servers. The investigation of  uses a liquid cooling thermal management system to enhance the heat transfer in a rack cooling data center application, while the work of  outlines a road-map for future CFD work related to rack mounted cooling systems. For the intermediate length scale, the works of [19,20] address this type of hardware, but the studies only address moderate power density heat transfer ther- mal control strategies. The work of  includes the fi- delity of the thermal vias, solder, PCB, and shelf inter- face. Other applications of using numerical heat transfer and CFD in electronic and avionic systems are given in [21,22]. Presently, there appears to be a void of CFD si- mulation databases addressing the so-called intermediate application level. The goal of this current study is to ad- dress this absence of literature by simulation of an inter- mediate sized electronics enclosure, which is subject to very large power densities. This is in an effort to address the ever changing requirements of affording more power in a smaller packaging level.
Understanding and controlling the thermal properties of nanostructures and nanostructured materials are of great interest in a broad scope of contexts and applica- tions. Indeed, nanostructures and nanomaterials are get- ting more and more commonly used in various industrial sectors like cosmetics, aerospace, communica- tion and computer electronics. In addition to the asso- ciated technological problems, there are plenty of unresolved scientific issues that need to be properly addressed. As a matter of fact, the behaviour and relia- bility of these devices strongly depend on the way the system evacuates heat, as excessive temperatures or temperature gradients result in the failure of the system. This issue is crucial for thermoelectric energy-harvesting devices. Energy transport in micro and nanostructures generally differs significantly from the one in macro- structures, because the energy carriers are subjected to ballistic heat transfer instead of the classical Fourier’s law, and quantum effects have to be taken into account. In particular, the correlation between grain boundaries, interfaces and surfaces and the thermal transport prop- erties is a key point to design materials with preferred thermal properties and systems with a controlled behaviour.
Heat transfer through nonwoven fibrous structure has been studied extensively in order to optimize product design and development. Bhattacharyya developed a model to calculate thermalconductivity of fibrous materials and showed that effective thermalconductivity increases by increasing material thickness and mean temperature . Stark and Fricke improved Bhattacharyya’s model by introducing variable fiber orientation concept. By considering the coupling between the solid and gaseous conduction, they found a good agreement between the developed model and the experimental results as a function of temperature, density, and air pressure . Lee and Cunnington developed a theoretical model for radiation heat transfer for high porous fiber insulation and validated their model experimentally by using silica fibers . Mohammadi et al. measured effective thermalconductivity of multilayered ceramic and fiberglass needled nonwovens. Their statistical analysis revealed that fabric weight, thickness, and porosity along with the applied temperature are enough for an accurate prediction of effective thermalconductivity . They also calculated the conduction component of total heat transfer analytically and estimated the radiative thermalconductivity of the tested samples. It is concluded that addition of fiberglass into the structure increases radiative conductivity, since fiberglass has lower packing density than ceramic causing a higher mean free path for the photons . Wang et al. numerically modeled the effective thermalconductivity of fibrous materials by using lattice Boltzmann algorithm. Their model revealed that thermalconductivity increases with increasing fiber length and becomes almost constant when the fibers get sufficiently long enough .
Table 3 gives our measured values of the thermal con- ductivity enhancement for silver nanofluids. As noted previously, each data point represents the average of five measurements at a specific concentration and room temperature. The experimental data along with calcula- tions using Equation 6 with and without considering the size dependence are presented in Figure 3. First, the size dependent model (Equations 3, 5, and 6 was used to correlate the data and a value of n = 0.088 was found to give the best fit with an AAD = 2.01%. Then, the same value of n was used in the size independent model (Equation 6) and resulted in an AAD = 3.64%. Figure 3 appears to confirm that the thermalconductivity of the nanofluid decreases with decreasing particle size, although the results are not conclusive. This could be due to the higher than expected thermalconductivity of nanofluids containing 20 nm silver particles resulting from aggregation (Figure 2a). Since the dry 20 nm parti- cles were highly aggregated when purchased, we consider it likely that they are aggregated in the dispersion despite being subjected to sonication. In an aggregated structure, a fraction of the particles form a conductive pathway, which could result in enhanced conduction . This is supported by numerical simulations and molecular dynamics studies [27-29]. On the other hand, the value of n = 0.088 obtained by fitting our data implies that the extent of aggregation was probably small and most parti- cles were randomly dispersed in the fluid. Values of n close to ±1 in Table 2, obtained by fitting literature data, do not appear to be physically reasonable because they imply series or parallel alignment of particles.