A highpowersemiconductordevice with integralheatsink capable of accommodating substantial heat flux on the order of one kw per cm.sup.2. Theintegral heatsink is formed on the active surface of the semiconductor and utilizes an AlN thin film of high purity to provide a low thermal impedance heatconductor for removing heat directly from the active semiconductor surface. A microchannel heatsink is formed on the A1N thin film and has a source of cooling fluid flowing through the microchannel heatsink for conducting heat away from thesink. The result is the ability to conduct large heat fluxes away from the intimately contacted heat generating semiconductor surface to the cooling fluid in the microchannel heatsink and thus operate the semiconductor under substantially higher power than has been practical heretofore in a device of such simplicity.
To prevent expansion, heat needs to be dissipated through the use of a sandwich-like structure. Solder de- gradation increases the silicon resistance. Cyclical tem- perature changes result from the creep strain and plastic strain that are produced by the power cycle, which in turn produces cracking in the solder due to fatigue. It is necessary for the structure to release heat from the sili- con. The contact area of the aluminum nitride plate is larger than that of the laminated structure between the silicon and the heatsink plate. In Figure 1, boundaries (i) and (ii) are on the collector side and emitter side, re- spectively. The current flows from the collector side (i) to the emitter side (ii) through aluminum wires. The cur- rent on boundary (i) is the collector current. The differ- ence in voltage between (i) and (ii) is the collec- tor-emitter voltage.
internal quantum efficiency, cavity loss, series resistance, threshold current and effective heat dissipation pack- aging measures, etc. . By analyzing the factors affecting the power efficiency of the semiconductor laser, this paper designed the epitaxial structure of the high efficiency 1060 nm semiconductor laser, and carried out the fabrication of devices, then obtained the highpower efficiency of the device.
AlGaN/GaN high electron mobility transistors (HEMTs) are ideal candidates for use in applications with requirements of very highpower densities . However, due to poor thermal properties of commonly used starting substrate materials for GaN epitaxial growth (such as Sapphire, Silicon), the usable power densities are limited and the peak operational capability of AlGaN/GaN HEMTs remains unachieved. In order to attain reliable operation and harness the true performance of GaN devices, improved thermal management is necessary . CVD Diamond with its high room-temperature thermal conductivity that is almost 3 to 10 times higher than even thermally conductive substrates such as Silicon Carbide (SiC) could emerge as the ideal substrate option to address the heat transfer issues and aid the development of power electronics with extremely high reliability and power densities. This area of research is gaining focus and reports evaluating integration of Diamond and GaN for device technologies have been published [4, 5]. It has already been shown through simulation and experimental demonstration that GaN-on-Diamond platform can significantly outperform GaN-on-SiC platform for Radio Frequency (RF) applications by reducing thermal resistance and thereby increasing power density [3, 6, 7]. Fig. 3 shows that with GaN-on-Diamond wafers, a nearly threefold improvement in RF power density could be achieved for a given channel temperature when compared to GaN-on-SiC . It should be noted that most of the work which has been accomplished on GaN-on-Diamond till date has been primarily focussed on RF devices.
A novel cross-fin heatsink consisting of a series of long fins and a series of perpendicularly arranged short fins was proposed to enhance natural convective heat transfer. The design principle of the cross-fin heatsink was based on overcoming internal thermal fluid- flow defects in a conventional plate-fin heatsink. The thermal performance of the proposed heatsink was compared with a reference plate-fin heatsink in horizontal orientation. A numerical model considering both natural convection and radiation heat transfer was developed to obtain thermal fluid-flow distributions and heat transfer coefficients of both the cross- and plate-fin heat sinks. Corresponding experiments were performed to validate the model predictions. It was demonstrated that, compared to the reference plate-fin heatsink, the cross-fin heatsink enhanced the overall (including natural convection and radiation) and convective (excluding radiation) heat transfer coefficients by 11% and 15%, respectively. Importantly, the enhancement was achieved without increasing the overall volume, material consumption, and too much extra cost. The proposed cross-fin heatsink provides a practical alternative to the widely adopted plate-fin heat sinks.
Many researchers investigated the enhancement design or calculation of different heat sinks using numerical and experimental methods. Bejan and Sciubba (1992) obtained the optimal rib spacing for maximum heat transfer from a package of parallel plates that was cooled by forced convection. Knight et al. (1992) developed a rib optimization method for a heatsink with micro channels by iterative solution of nonlinear equations. Bessaih and Kadja (2000) carried out the numerical simulation of air turbulence on several electronic components in a vertical channel, and the influence of the heat dissipation of the components was obtained and a method of heat dissipation was proposed. Etemoglu (2007) had experimented with and analyzed the new technologies of cooling the electronic equipment such as jet-flow and
analysis is carried out for this fluid – structure case. Two cases are simulated with a velocity of flow as 4 m/s and 10 m/s. The base of the heatsink is given with heat flux boundary. The results of both the scenarios are showing good coherence with the physical phenomenon. As velocity increases the temperature of the heatsink decreases, so the heat generated in the heatsink will become less. The rate of heat transfer will be more.
These intricate parts in the plastic industry, comes with toughest quality requirements, could be achieved through injection moulding technology (Nardin et al., 2002). Due to its ability to produce multifaceted shape plastic parts with good dimensional accuracy and very short cycle times, injection moulding has become one of the processes that is greatly preferred in manufacturing industry (Bozdana & Eyercioglu, 2002). These injected moulded parts, however, are very prone to defects. To avoid such quality control problems, it is desirable to successfully predict the optimum processing conditions, such as pressures, temperatures, and times (Hill, 1996). Any change in these variables can affect the process stability and the quality of the manufactured parts. Unfortunately, it has been found difficult to control and adjust simultaneously between the processing conditions and the properties of the product; and there is no single set of rules to designate which parameters to use in order to manufacture consistently a part with no defects (Dumitrescu et al., 2005). Furthermore, failures or damages of these parts become more frequent when it exposed to high temperature environment.
At present, the semiconductor laser has been widely used in industrial, commercial, scientific research, information, military and medical aspects due to its advantages such as light weight, small size, high efficiency, stable output power, easy to optical fiber transmission and so on [1-8] . Laser medical equipment has been widely adopted in various fields of disease treatment, such as ophthalmology, surgery, cardiology, dermatology, etc. New 1470nm semiconductor laser with high water absorption coefficient, strong cutting ability, certain solidification, hemostatic effect, high fat absorption, can be effectively applied in the treatment of common diseases such as minimally invasive surgery, skin beauty and vascular lesions and high lipolysis. STM32F103 series microprocessors with the architecture of ARM Cortex-M3 have high performance, low cost and rich external interface, with built-in nested vector interrupt controllers are built to meet the real-time security control requirements of medical devices. In order to meet the development needs of laser medical instruments and provide convenient intelligent control platform for instrument operators, this report designs a 1470nm high-powersemiconductor laser medical treatment control system based on STM32F103.
Piezoelectric fan placed vertically, and the piezoelectric fan was placed in front of flat fins. As the piezoelectric fan was placed in different positions, right behind the heatsink fluid flow structure was somewhat different, but the impact of piezoelectric fan for the heatsink, that was mainly generated by the front end of jet flow and the surface of the entrained flow of piezoelectric fan, the two different placement of piezoelectric fan induced the disturbance moving gas for local cooling heatsink was obviously different. When the center position of piezoelectric fan was higher than heatsink fins, the affected area of entrained flow should be taken as a priority consideration. When the center position of piezoelectric fan was lower than heatsink fins, the effect of impact flow area should be taken as a consideration. The cooling performance increased as the fan centers to the flow channel height (H w ) relatively decrease.
All electronic equipment relies on the flow of and control of electrical current to perform a variety of functions. Whenever electrical current flows through a resistive element, the heat is generated. Regarding the appropriate operation of the electronics, heat dissipation is one of the most critical aspects to be considered when designing an electronic box. Heat generation is an irreversible process and heat must be removed in order to maintain the continuous operation. With various degrees of sensitivity, the reliability and the performance of all electronic devices are temperature dependent. Generally the lower the temperature and the change of temperature with respect to time, the better they are. Pure conduction, natural convection or radiation cool the components to some extend whereas today’s electronic devices need more powerful and complicated systems to cope with heat. Therefore new heat sinks with larger extended surfaces highly conductive materials and more coolant flow are keys to reduce the hot spots.
(optional), limited memory, a position finding system and a battery. The network topology is unknown and nodes have restricted energy and unattended in nature are main facet of the network. Due to limited resources and deployment of nodes in hostile environments sensor network arise many design issues. For human being, where it is impossible and infeasible to interact or monitor the environments conditions, sensor nodes are placed in area. Many military and social applications affect the efficiency of theses unattended sensor nodes i.e. battlefield surveillances, target field imaging, Military situation awareness, Sensing intruders on bases, distributed computing and inventory control. Small size of sensors is a pre-requisite for some applications; additionally the transmission range of sensor nodes is small, which reduce the chances of detection by some attacker. The speed of CPU, battery lifetime, memory and bandwidth are also constraints due to the size issue of nodes. For rising the lifetime and superiority of information gathering some efficient techniques are necessary and reducing the communication latency in wireless network is also required. In WSN, nodes are mainly to be fixed for the whole lifetime rather than not fixed in mobile ad hoc network. Even though the position of sensor nodes are fixed but their topology and routing path of the network can change. When the data is not being transmitted, sensor nodes may go to sleep mode to save energy in wireless network. New nodes may be added in the network when some nodes are dying and run out of battery. In the network initially all the sensor nodes have same amount of energy, and result of region may experience higher activity in which nodes are located. The behavior of sensor application is data-centric and intermittent communication paradigm is followed. A main factor of WSN is need of the sensor nodes to constantly broadcast the information (data) to destination/receiver or the sender/transmitter within the fixed time interval that is given by the controller/user application to reply to the information in affixed time. Out of date information may lead to disastrous results and there is no use of that information in network. To change the node density; network topology; network size, scalability are another main feature. The density of the sensor nodes in WSN is more than the mobile ad hoc and wired network. The fact arises because the communication range is larger than the sensing range, so to get satisfactory sensing power large amount of nodes are needed. Resistance against attacks and failure is requirement of sensor nodes.
Farhad et al.2013 solve .Navier–Stokes equations and RNG based k- turbulent model for array of solid and perforated fins mounted in vertical flat plates used to predict turbulent flow parameters. Flow and heat transfer features are presented for Re. no. from 2×104 - 3.9 × 104.Prandtl numbers was taken as 0.71. Numerical simulation is validated by compare with experimental results.
This paper includes the evaluation of the existing design of the heatsink having trapezoidal fin array with thickness of 2.75mm at the base to 1.5mm at the tip. Various parameters like heat flow though the fin, efficiency, effectiveness and number of fins required to dissipate the heat are calculated. Due to space constraints currently only 25 fins are being employed. A new design of the heatsink having rectangular fin array is proposed. Fin parameters of the two designs are compared and tabulated.
Present study focuses on the thermoelectric generator (TEG) using heat pipe as heatsink and Waste heat can be used to generate electricity using thermoelectric generator (TEG). TEG utilizes the thermoelectric effect to generate electric power from a temperature difference across the device. The combined heat pipes thermo-electric generator (CHP-TEG) has been introduced in this study of recovering the free energy from the industrial and automobile waste heat. Two technologies identified to be of use for waste heat recovery are TEGs and heat pipes. Both TEGs and heat pipes are solid state, passive, silent, scalable and durable. The use of heat pipes can potentially reduce the thermal resistance and pressure losses in the system as well as temperature regulation of the TEGs and increased design flexibility. TEGs do have limitations such as low temperature limits and relatively low efficiency. Heat pipes do have limitations such as maximum rates of heat transfer and temperature limits. When used in conjunction, these technologies have the potential to create a completely solid state and passive waste heat recovery system. The conversion efficiency of thermoelectric generator is function of temperature difference (Heat source and heatsink temperature). The thermal performance of thermoelectric generator will be improved or enhanced by using heat pipe as a heatsink on thermoelectric generator.
ABSTRACT: Radar is an electronic system that is widely used in the field of object detection to determine the range, velocity and angle of objects. Radar systems consist of various components that produce excessive heat during operation. Since usually these components are housed on a thermally conducting material, thermal design and analysis of such systems plays a very important role in ensuring optimal functionality of radar. Air cooled radar transmitter system is considered here. The aim of this paper is to ensure the optimum functioning of a transmitter unit by maintaining the maximum temperature at a specified location on the thermal base plate to within 70 . The environment temperature is considered to be 49 which determines the range of temperature in which the radar system is used. This involves the design of a heatsink that is effective in dissipating the heat that is rejected onto it by the components at this specified location. It is known that around 420Watts of heat is being rejected onto an area of around 71.25cm 2 on the heatsink. The material of the heatsink used is Copper. Commercially available software packages like PTC Creo Parametric 3.0 and Autodesk CFD simulation 2012 are used for modelling and analysis respectively. Analysis is carried out with the operating conditions of air cooled transmitter system given as input. Theoretical validation of the CFD result is carried out and excellent convergence in obtained. MATLAB is used in plotting the various graphs which determine the final fin parameters of the newly designed copper heatsink. Comparisons of the design currently in use in a manufacturing company for the aforementioned scenario versus the new design is presented. KEYWORDS: Triangular fin, Rectangular fin, Efficiency, Effectiveness, fin spacing, Optimum thickness.
Abstract: This project reviews pin fin heat sinks of different cross- sections, low density versus high density pin configurations and more factors in figuring out what is required for an application. The experiment will be conducted with two different pin fins i.e., a circular cross section and a square cross section in an open circuit suction type wind tunnel, the temperature variations and heat dissipation are compared between both the fins and conclusions are drawn. The experiment is concluded with comparing the results obtained from the experimental setup with that of the analysis of the setup.
There are two flows, i.e., vertical and horizontal flows, around the radial heatsink. The vertical flow is in the upward direction, since air is heated by the heatsink (which is maintained at a higher temperature) and becomes lighter than the surrounding air. The horizontal flow is created by air entering from outside the heatsink to make up for the vertical flow in the inner region. Therefore, the overall flow pattern is chimney-like. The heat transfer rate in the outer region of the heatsink was higher than in the inner region. This was because the temperature difference between the air and the heatsink decreased as the cool air proceeded towards the inner region of the heatsink. It is shown in figure 2.
We have provided an overview of the research performed in analysis of microchannel heat sinks with carbon nanofluids. Currently lot of research is going on microchannel heat sinks with various applications and our research will helpful for development on new IC cooling devices. Heat transfer enhancement carbon nanotubes –water nanofluid flow inside semicircular microchannel heatsink is studied both theoretically and experimentally. It is concluding that microchannel heat sinks with nanofluid will best help for extraction of heat from modern heat exchangers and IC devices. The two function objective optimization validates the design the heatsink geometry and it is remarking that 0.1% nanotube concentration is referred as best concentration which will avoid particle clogging inside microchannel grooves and flow under laminar region will leads to uniform heat dissipation and main pressure drop rise is less which will ultimate proves less cost of equipment. The given application flow is best optimized at Reynolds number 550 to 750 and concentration 0-0.1% and performance improvement is observed. Further design with continuous variables such as fin width, fin heights, different new class coolant fluids, flux and wall temperature condition will emerge the field of microcovective heat transfer and microfluidic areas.
Usually, the investigation of heat transfer has been carried out for a straight microchannel by selecting the criteria of temperature distribution, pressure drop and heat transfer coefficient as cooling performance. It has been concluded that the straight microchannel give better result at Reynolds number in range of 400 to 450 with flow rate in between 320.0 ml/min to 350.0 ml/min (Gawali et. al, 2014). The experimental results in heat transfer indicated that forced convection in the micrcohannel exhibited excellent cooling performances, especially in the phase change regime. It was applied as heat removal and temperature control devices in highpower electronic components. When the critical nucleate heat flux condition appeared, the flow mechanism changed into fully developed nucleate boiling and accompanied with wall temperature decreased rapidly while pressured drop increased sharply (Chen et al., 2004).