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Heat Transfer Calculators

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coolingZONE Library – where engineers and researchers go to see the latest and archived developments in thermal management.


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Library  »  Qpedia - Monthly Thermal eMagazine

Using Integrated Planar Thermosyphon PCBs to Enhance Cooling of High Brightness LEDs

 - high power led lighting systems bring with them a lot of promise and numerous challenges. the advantages of led lamps are compact size, long life, easy maintenance, rugged construction, ability to withstand cold temperature, reduced ir radiation and increased performance. thermal management, cost competitiveness and quality are the challenges faced in widespread usage of such lamps. thermal management is a notable roadblock to the implementation of such systems. there is 70 to 80 % of the electrical power in a high brightness led is converted to heat which has to be efficiently dissipated. poor thermal design leads to high operating temperatures resulting in reduced brightness, shift in wavelength (color) and reduced life. table 1 shows the potential advantages and the challenges of a led lighting system. Read more »

Fundamentals: Thermal Resistance of Heat Pipes

 - the question often arises that what is the effective thermal conductivity of a heat pipe. the correct answer depends on the construction and the wick material inside the heat pipe. this qpedia explains fundamentals explains the thermal resistance of heat pipes and how to calculate it. Read more »

Technology Review: Phase Change Materials

 - qpedia reviews innovative technologies developed for electronics cooling applications. in this article we review new developments in phase change materials (pcm). liquid coolant with microencapsulated phase change materials for automotive batteries and a new invention and application of phase change materials for led lamp assemblies. Read more »

Nanofluids In Heat Pipes

 - heat pipes are simple heat transfer devices that are ubiquitous in electronics cooling applications. they transfer heat with a very low thermal resistance but are limited in the maximum load by various factors. the performance of the heat pipe is defined by both the maximum heat load and the thermal resistance when operating within that limit. figure 1 shows the schematic of a heat pipe and the different component thermal resistances. one of the variables that determine the performance of a heat pipe is the thermophysical properties of the working fluid. because of the temperature range of electronics, the most cost effective working fluid is water. although water is the best heat transfer fluid, its properties can be enhanced by introduction nano-particles. Read more »

Cooling Chip On Board LED

 - heat generated by an led, and how it affects its response time, makes cooling a primary concern. because leds are semiconductor devices their light output is directly impacted by temperature. up to 80% of the power for leds turns into waste heat, so if the thermal situation is not managed it will cause the led to perform improperly, stop functioning, or shorten its expected life. Read more »

Technology Review: Mobile Device Thermal Management

 - qpedia reviews innovative technologies developed for electronics cooling applications. this section presents selected patents that were awarded to developers around the world to address cooling challenges. in this issue our spotlight is on the thermal management of mobile devices. Read more »

Industry Developments: Cooling With Lasers

 - while electronics inside laser systems may require thermal management, lasers may also one day have a major role in cooling electronic components. such developments are already underway, as researches are hoping laser cooling could lead to a new form of computer chip that could cool itself on its own. this article will discuss the promosing future that lasers have in the electronics cooling field. Read more »

Fundamentals: Basic Definition of Thermal Resistance

 - in this new section, qpedia reviews fundamental thermal engineering principles, calculations and equations needed for the successful cooling of electronics. this issue focuses on thermal resistance, a vital component of heat transfer. Read more »

Measuring Heat Flux from a Component on a PCB

 - it is vital to understand heat dissipation from electronic components during their operation in order to properly design the cooling system and selection of the appropriate heat removal methodologies. heat dissipation from a component in an electronic package not only influences its own performance but also affects the performance of neighboring components, leading to their failure. this article will discuss a new method of measuring the heat flux from a component on a pcb. Read more »

Design Parameters In Immersion Cooling

 - two phase immersion cooling can be a viable option to cool power electronics and high performance computers. however, non-thermal aspects play a significant role in the proper functioning of the system. this article will review these parameters that thermal engineers need to understand in order for a successful implementation of two phase immersion cooling technology. Read more »

Heat Transfer Calculations of a Thermosyphon

 - thermosyphons and heat pipes are used to transport large amounts of heat over a particular distance by using a two-phase fluid inside a hollow pipe. the more widely used heat pipe uses a wicking structure to transport the liquid back to the hot end whereas a thermosyphon is a simple hollow tube that uses gravity. the lack of a wicking structure makes the thermosyphon much less expensive than the traditional heat pipe. however, because of the integral role that gravity plays in the operation of the thermosyphon, it is only effective when the evaporator is below the condenser. in this article we will focus only on the non-looped single tube, known as the thermosyphon pipe, with water as the working fluid. Read more »

Data Center Hybrid Cooling

 - data center's are the backbones' of today's information economy providing fertile ground for application development, communications and running the very applications that make business possible. approaches to cooling data centers have tended to look at polarized strategies of all liquid or all ambient air or all refrigeration. but could a hybrid approach be more fitting and still save both money and energy? our technical paper shows yes it is possible and how it is done. Read more »

Modeling Vapor Chamber As Heat Spreading Device In Cfd

 - as the power dissipated by the devices increases, and the devices get smaller, the heat densities increase rapidly, and heat dissipation gets more localized. the heat fluxes approach 100 w/cm2 and local heat fluxes at hot spots are even higher, however the proper junction temperature must be maintained to meet performance and reliability requirements. in some cases this temperature has to be as low as 85 degree c or even lower. this trend drives the need for the fast heat spreading. one such device is a vapor chamber. Read more »

Application of TEC Using Heat Exchanger for Sub-Ambient Liquid Cooling

 - thermoelectrics are solid-state devices capable of transferring heat across a temperature gradient. as a solid-state technology, there are no moving parts and no working fluids, which translates into simple integration, essentially no maintenance, quiet operation, and acceptable reliability. for applications involving relatively steady state cooling and low humidity with a continuous and uniform supply of dc voltage, thermoelectric module reliability is extremely high. mean time between failures (mtbfs) in excess of 200,000 hours are not uncommon in such cases and it is generally considered to be an industry standard. in addition, the degree of cooling may be readily controlled by means of the current supplied to the thermoelectrics. Read more »

Experimental and CFD Analysis of a Typical Telecom Board

 - in the multi-trillion dollar industry of electronics, the ever-rising demands on product capabilities are driving the importance of thermal management toward the leading edge of design cycles. to maintain spatial efficiency, engineering teams deploy products with higher complexity, more dense pcb topologies, higher power dissipations, etc. resulting in harsher operating conditions. due to an abundance of competition, and reduced design cycle times program budgets continue to be reduced. while system capabilities, and design budgets once followed parallels, now teams are pulled apart by departmental directives while implementing strategies to solve complex thermal management challenges that yield high roi. when faced with solving a thermal design challenge, strategies may include: analytical modeling, computational fluid dynamics (cfd) and empirical testing. these approaches are subjective, often based on budgets, company culture, an engineers background and training, etc. this article will investigate these three methodologies used to solve thermal management challenges found on common communications boards. Read more »

Enhancing Heatsink Performance in Natural Convection Using EHD

 - electrohydrodynamics (ehd) is the study of the dynamics of electrically charged fluids. more specifically, it is the study of the motions of ionized particles or molecules and how their interactions with electric fields affect the surrounding fluid. with more research, ehd has the potential to start entering the thermal management scene of the electronics industry because of its ability to cool heatsinks that do not have a system flow available, while staying completely quiet. there are various ways to apply ehd to enhance heat transfer. utilizing electrostatic force is one of the most promising methods among various active techniques because of its several advantages. this engineering article explores this topic and its application. Read more »

New Design Concepts in 3D Stacked Chips and Their Thermal Challenges

 - in todays mobile handset market the trend is to provide high performance, low cost components with integration of functionality and small form factor. the ever increasing demand of handset makers to provide smaller, thinner and lower cost packaging solution drives the packaging industry to develop packages that integrates more devices in the same footprint in which devices are integrated within the package in vertical direction, named 3d packaging. in this, the logic device and memory devices are packaged and tested together and then stacked together in a package form typically known as package on packages (pop) technology which is popular and widely used in mobile phone industry. while a boon to smaller and thinner handsets, and the consumers who use them, thermal engineers have new challenges to address. Read more »

Enhancing Heat Transfer Using Single Phase Self Oscillating Jets

 - innovative cooling technologies are being developed as the power dissipation of electronic components is increasing rapidly over the years. in general a cooling technique is evaluated by a term called the heat transfer coefficient(htc) which is a measure of heat removal. literature is rich with htc values for different fluids and data shows that jet impingement cooling seems to offer a high heat transfer coefficient and is expected to result in better cooling than natural or traditional forced convection methods. this engineering paper explores jet impingement cooling, with a focus on single phase self oscilatting jets. Read more »

Thermal Modeling for Small Form Factor Pluggable Devices: Different Approaches

 - most of the industrial routers and switches today use optical transceivers for transmitting and receiving data over fiber-optic cables. there are many types of these opto-electronic packages such as xenpaks, x2s, xfps , sfp , sfp+. one widely used optical transceiver is the sfp or small form factor pluggable device for which different thermal modeling techniques will be discussed and reviewed in this article. Read more »

Simple Analytical Calculations for Free Convection Cooled Electronic Enclosures

 - natural convection cooling is the preferred method of cooling for electronicsenclosures, since, it is silent, reliable, and it is environmentally sound because no additional energy is used to remove the excess heat. on the other hand, natural convection cooling is more complicated to design because it may be challenging to identify if a certain application is suitable for fan-less cooling at the very early stage of the product development process. computational fluid dynamics is one way of analyzing this problem this but it is time consuming and not a feasible way of determination at the very early stage. instead, a quick estimation is required which will help this assessment. the better box analytical model developed by luiten is instrumental in doing quick calculations for convection cooled enclosures. Read more »

3D Cooling Technology: Segmentation, Thermoelectrics, and Enhancing the Die Package

 - in this technology review article, our engineers present three technology that are currently under patent and could be useful for new designs involving 3d ic packaging. the first is segmentation of a die stack for 3d packaging thermal management, the second thermoelectric 3d cooling and the third included techniques for enhancing the die package in 3d semiconductors. Read more »

Thermal Characteristics of Wickless Vapor Chambers

 - spreading resistance continues to play a dominant role in the overall heat transfer from the source to sink. with trends towards smaller component footprint and higher power dissipation in electronic components, the need to spread the heat over the base of the heat sink has become very important to reduce the spreading resistance. in some applications such as high power lasers, there might be a need to have a fairly uniform temperature distribution. in such situations a vapor chamber can be one arsenal in the design tools to tackle these problems. this article will help engineers get an overview of vapor chambers and their use in electronics cooling. Read more »

Using Phase Change Material Inside and Outside of Electronics Thermal Management

 - for engineers working in electronics thermal management, phase-change materials, or pcms, are an effective type of thermal interface material (tim). they are typically used between cooling solution and power generating electronics and devices and can provide thermal performance superior to dry tim pads. but phase-change materials have much wider applications in and outside of electronics thermal management. these include cooling commercial goods and different applications used for cooling buildings. Read more »

Conduction-Convection Cooling Solution for 3D Stacked Electronics

 - future electronics must provide enhanced functionality within a minimal form factor. to address this demand, 3d stacking of ics has emerged as an extremely promising technology able to address the performance requirements of tomorrows high speed computing. this novel technology enables integration of logic, memory, rf and optoelectronic devices on a single chip. the miniaturization comes with the penalty of significant thermal management issues, however. the rate of heat generated per unit volume and thermal resistance increase significantly with each added layer. also, heat removal from the chips placed in the middle of the stack constitutes a major challenge. this article reviews the design and thermal parametric study of a unique liquid interface thermal management solution for a 3d chip stack. Read more »

Pulsating Heat Pipes And Their Use in Thermal Management

 - heat pipes are passive heat transport devices that work via phase change (evaporation and condensation) to transfer heat from the evaporator site to a condenser location where heat is dissipated. traditional heat pipes feature an internal wick structure for returning condensate back to their evaporator section. pulsating heat pipes (phps), on the other hand, use thermo-hydrodynamic characteristics that involve several different processes. but, like all effective heat pipes, they can provide continuous, passive heat transport in many electronics applications. Read more »

Thermal Characterization of Multi-Chip Modules

 - multi-chip modules (mcms) look like single chip components, but as the name describes, they actually contain multiple chips in one package. one example of an mcm is intels core i7 cpu series. these are still called cpus, but they are actually modules that house the cpu itself, along with other components such as the memory controller and graphics processor. the advantages of mcm construction are many, including reduced size vs discrete components, faster data rates and better signal quality (with less emi) between the components on an mcm, and simpler motherboard design, since many connections are now made within the mcm. mcms do create challenges for thermal engineers however, not only because of the possible increase in power density, but because the traditional jedec jesd51 standard only holds true when the junction-to-case thermal resistance, ?j-c, describes the thermal path from one heat source to the case (or other reference point). Read more »

Cooling Using Phase Change Materials - Technology Review

 - a phase-change material (pcm) is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. heat is absorbed or released when the material changes from solid to liquid and vice versa; thus, pcms are classified as latent heat storage (lhs) units. phase change materials are useful for cooling a wide range of products and their application varies. in this technology review, we review two applications of phase change materials: two for cooling batteries and one for a heat sink with a cavity filled with phase change material. Read more »

Boundary Condition Dependence of Junction to Case Thermal Resistance

 - the junction to case (?jc) thermal resistance of a semiconductor package is a useful and frequently utilized metric in thermal management of electronics. this metric is not an intrinsic property of the device but depends to some extend on the cooling condition at the case surface intended for heat sinking. also, ?jc can be measured only with limited accuracy by the methods existing today. this article investigates the dependence of the ?jc of power packages on different cooling boundary conditions and gives an assessment of the accuracy of two measurements. methods: the traditional method using thermocouples to measure the case temperature and the recently proposed transient dual interface (tdi) method. this accuracy is measured against results generated by computer simulations. Read more »

1U Server Chassis Thermal Management Technology Review

 - in this technology review, we consider three relatively new technologies available for the thermal management of 1u computer servers. flow through cooling, integrated forced air and side exhause cooling are all reviewed in this paper. Read more »

Cooling Super and Quantum Computers

 - supercomputers that can perform billions of calculations per second (gigaflops) also contend with the same issue that affects laptops and handheld devices; excessive heat. cooling supercomputers has typically been achieved with facility-level air conditioning. some systems also run cold water through heat exchangers to extract the heat from these machines. Read more »

Loop Heat Pipes with a Flat Evaporator

 - a loop heat pipe (lhp) is a two-phase heat transfer device that uses capillary action to remove heat from a high temperature source and transfer heat to a condenser, where the heat is removed by other cooling methods. lhps are completely passive and self-driven. they are similar to heat pipes but have the advantage of being able to provide reliable operation over long distance and the ability to operate against gravity, which transports large heat flux with a small temperature difference. Read more »

Thermal Management of Electric Vehicles

 - the u.s. department of energy (doe) freedom car program sets certain goals and technical targets for the electric traction system (consisting of power electronics and electric machines) of advanced vehicles [1]. these requirements are designed so that hybrid electric vehicles (hev) and electric vehicles (ev) gain enough market penetration to ensure a significant reduction in united states dependence on foreign oil. in order to achieve these targets, significant reductions in volume, weight and cost of the thermal management system have to be achieved. at the same time, the performance and lifetime requirements have to be met. this paper reviews possible approaches for replacing the current cooling system used in hybrid electric vehicles (hevs). Read more »

Heat Spreader Options and Materials

 - a heat spreader is typically a solid or liquid filled chamber that disperses the heat on a surface that is larger than the heat source size. a heat spreader is generally used when the heat source tends to have a high heat-flux density, (high heat flow per unit area), and its size is much smaller than the contact area to the heat exchanger or heat sink. a typical example is a plate between a small component and the base of a larger footprint heat sink. the heat sinks performance can be improved with a heat spreading plate. the plate, e.g. made of copper, has a high thermal conductivity and heat from a smaller source will spread out over the plate and more effectively transfer into the secondary heat exchanger. along with copper, heat spreaders are made from different high thermal conductivity materials and in some designs feature an internal vapor chamber for added thermal spreading. our review considers what's leading in the industry today. Read more »

Thermoelectric Cooler Optimization for Deployment in Electronics Thermal Management

 - thermoelectric coolers (tec) are solid state refrigeration devices which use dc current to generate cooling or heating. unlike traditional vapor-compression refrigeration system, thermoelectric cooling has no moving parts and circulating fluid. its simple structure and small size makes it a good choice for a thermal management device in electronics. however, the low coefficient of performance (cop) of a tec hampers its wide deployment. our article consider the optimization for best cooling effect. Read more »

Technology Review: Liquid Filled Heat Sinks, 2002-2013

 - in this issue our spotlight is on liquid filled heat sinks. we consider three innovative approaches to liquid filled heat sinks being taken in the market: optically transparent, heat conductive fluid heat sinks; a high reliability cooling system for led lamps using a dual mode heat transfer loop; a heat sink apparatus and electronic device that have the same. Read more »

Theoretical Cooling Limit of a Thermosyphon

 - passive, two phase liquid cooling schemes for thermal management of electronics rely on heat pipes and thermosyphons. thermosyphons are passive cooling devices able to overcome the capillary limitation of heat pipes by using gravitationally induced buoyancy to drive the flow. there are several configurations in which thermosyphons can be deployed. this article reviews an analytical approach for finding the theoretical cooling limit for a thermosyphon with a flow boiling arrangement. a pressure model was developed and used to predict the critical heat flux (chf) of such a device. Read more »

Thermal Conductivity of Printed Circuit Boards

 - when performing an analysis of heat generating electronic components on a printed circuit board (pcb or pwb), the pcb is often used to dissipate a significant portion of the heat. some components are designed to dissipate heat with the use of a heat sink, and they often have a low resistance from their junction to case in order to facilitate the thermal transfer. when specifying heat sinks for these components, the heat dissipated through the pcb can still be significant, but it depends on operating conditions and pcb design. Read more »

Compliant Cold Plate Technology Review: 1991-2007

 - compliant cold plates can take many different forms, as this link http://goo.gl/9wsxah to a google image search shows. in this technology review, the author covers developments in this area from 1991-2007 including technologies in high conduction flexible fin cooling modules, flexible cold plate having a one-piece coolant conduit and employing discrete cold plates compliantly coupled between a common manifold and electronics components of an assembly to be cooled. Read more »

Passive Thermal Management Technology for Fuel Cell Part 2: Passive Cooling Plates

 - the importance of fuel cells cannot be over-estimated. a fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent [1]. while hydrogen is the most common fuel, hydrocarbons such as natural gas and alcohols like methanol are sometimes used. individual fuel cells produce relatively small electrical potential, about 0.7 volts, so cells are stacked, or placed in a series, to increase the voltage and meet an application's requirements. in addition to electricity, fuel cells produce water, heat and, depending on the fuel source, very small amounts of nitrogen dioxide and other emissions. the energy efficiency of a fuel cell is generally between 40 to 60%, or up to 85% efficient in co-generation if waste heat is captured for use. Read more »

Thermally Conductive Polymers in Thermal Management

 - polymer materials are often used as heat insulators, but they are also formulated to be thermally conductive. heat conducting polymers have been in development for years. the thermal conductivity of polymers is typically 0.1-0.3 w/mk. adding thermal fillers to the compounds can increase thermal performance by modest levels. for some polymers, thermal conductivity is dramatically higher, but these materials are typically not available at market competitive prices. still, polymers have several desirable features for use in providing heat transfer. compared with metal heat conductors, polymers are easier to shape, lighter in weight, water resistant and offer some compressibility. Read more »

Carbon and Graphite Foams for Thermal Management

 - certain materials, such as diamond, provide substantially higher heat spreading capabilities compared with others. however, issues that include cost, availability and application make most of these materials unsuitable for conventional electronic cooling needs. one substance with excellent heat spreading properties is carbon. improvements in carbon materials are increasing industry interest as cooling needs mount for components and pcbs. carbon-based heat sink materials have included graphite strands, carbon nano-fibers and metal-graphite matrices. Read more »

Optimization of Evaporator to Condenser Length Ratio for Heat Pipe Maximum Performance

 - heat pipes have a multitude of applications in the thermal management of electronics. the thermal resistance of a heat pipe strongly depends, among other parameters, on so-called l-ratio, which is the ratio between the evaporator length and condenser length. the optimal l-ratio is defined as being the value for which the heat pipe thermal resistance is minimal, for a certain heat pipe assembly configuration. finding the optimal l-ratio offers a valuable tool for thermal practitioners to most effectively deploy the heat pipe in their application. this article reviews an analytical approach for finding this optimum l-ratio. Read more »

Passive Thermal Management Technology for Fuel Cells - Part 1: Control Valve Tests

 - a fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. hydrogen is the most common fuel, but hydrocarbons such as natural gas, and alcohols like methanol, are sometimes used. individual fuel cells produce relatively small electrical potential, about 0.7 volts, so cells are stacked, or placed in series, to increase the voltage and meet an application's requirements. in addition to electricity, fuel cells produce water, heat and, depending on the fuel source, very small amounts of nitrogen dioxide and other emissions. the energy efficiency of a fuel cell is generally between 40 to 60%, or up to 85% efficient in cogeneration if waste heat is captured for use. Read more »

Integrating Heat Pipes into Heat Sinks

 - in this technology review, patents covering the integration of heat pipes in to heat sinks are considered. there is much discussion about its deployment in the electronics industry, and these patents show some of the salient features that are the focus of different inventors. Read more »

Effect of Nozzle Geometry on Heat Transfer in Jet Impingement

 - jet impingement has one of the highest modes of heat transfer. its performance characteristics have been researched for a long time and numerous correlations has been developed for different situations. jet impingement performance has been correlated as a function of various parameters, such as nozzle diameter, jet to target spacing, heat source area, reynolds number, flow rate, etc. however, the shape of the nozzle has received less investigation. therefore, in this article we will review a few papers that take up this focus. Read more »

The Performance of a Heat Sink with Piezoelectric Fins

 - an led light is often made of a small piece of semiconductor, an integrated optical lens used to shape its radiation pattern, and a heat sink, used to dissipate heat and maintain the semiconductor at a low operating temperature. led lights present many advantages over incandescent light sources, including lower energy consumption, longer lifetime, improved physical robustness, smaller size and faster switching. led lights are powerful enough for room and street lighting and are relatively expensive. they also require more precise current and heat management than traditional incandescent and compact fluorescent lamp sources of comparable output. Read more »

Techniques For Measuring Thermal Performance Of Heat Pipes: A Technology Review

 - this technology review considers techniques for measuring thermal performance of heat pipes. in it we consider: method and apparatus for conducting performance test to heat pipe; performance testing apparatus for heat pipes, and a method for testing a heat pipe and corresponding test device Read more »

Diamond-Based Thermal Management Systems

 - the heat transfer conduction in diamond is very high (2000 w/m-k). that is attributable to the fact that diamond is composed of carbon atoms with stiff chemical bonds between them. heat transfer in diamond is carried by vibrations, known as phonons. in a crystal, atoms are arranged in an orderly fashion. the bond between these atoms is like a spring. when one set of atoms get excited, it creates a wave by exciting the other atoms. this phenomenon is called phonon. by comparison, heat transfer in metals is transmitted by free electrons. in copper, heat flows five times slower than in diamond. early thermal management applications of natural diamond included microwave and laser diode devices. but, the availability and cost of natural diamond restricted its wider development. industrial-made synthetic diamonds, however, opened new opportunities. [1] Read more »

The Impact of Orientation on Heat Pipe Performance with Different Wick Structures

 - the thermal performance of a heat pipe depends strongly on its orientation in operation relative to gravity. for a specific orientation, this performance is determined by the wick structure present inside the heat pipe. wick structures exhibiting low capillary pressure perform best in gravity-assisted applications, where the evaporator is located below the condenser. however, a wick structure producing high capillary pressure will be needed if a heat pipe is to be operated in a gravity adverse orientation. a previous qpedia article detailed how a heat pipe?s performance is really dependent on both orientation and wick structure [1]. this article builds on that same topic, as it presents a review of experimental results obtained with heat pipes, in the shape of round cross sections, in different orientations [2], [3]. the results are compared with data published in the literature [4], [5]. Read more »

Reducing Spreading Resistance in Heat Sinks: A Technology Review

 - in this technology review, our spotlight is on reducing thermal spreading resistance in heat sinks. we'll examine the following methods to do that: a heat sink base plate with heat pipe; a semiconductor assembly having reduced thermal spreading resistance and methods of making same; and a thermal diffusion apparatus. Read more »

Application of TECs to Thermal Management of 3D ICs

 - the advent of vertical chip integration, in recent years, has allowed 3d chips to overcome issues such as delay, bandwidth limitation and power consumption in interconnects, which occurs in traditional integrated circuits. by stacking the chips, the footprint of an ic has been drastically reduced; also, the length of the interconnecting wires has been considerably shortened by using vertical vias. from the thermal perspective, 3d stacked chips pose different challenges than what has been experienced in 2d packaging. for example, the heat dissipation of 3d ics is highly non-uniform and multidirectional, due to the intrinsic chip architecture and the available real estate. when cooling at sub-ambient temperatures is necessary, as may be the case for future applications, the small footprint of a 3d chip becomes an impediment to deploying a cooling solution. additionally, precision temperature control becomes difficult, since the surface to be controlled may be buried deep in the 3d stack. in response to cooling concerns about 3d ics, this article presents a review of methods available for cooling 3d ics to sub ambient temperatures using tecs. Read more »

Challenges in Testing Thermal Interface Material

 - when choosing a thermal interface material (tim), most of the time we look at the datasheet and find the thermal impedance if it is a solid material, or the thermal conductivity if it is a grease. then, we calculate the thermal resistance and temperature rise with those numbers. but, how do we know that a tim is performing as advertised? can we really tell if one tim will perform better than another, based on their specs? Read more »

Technology Review: Enhancing Heat Transfer on Surfaces, 1991-2013

 - in this technology review, we cover technologies developed from 1991-2013 dealing with enhancing heat transfer on surfaces. key technologies covered include a heat transfer device with fluid and using lobes, technology for enhancing thermal transmission efficiency of an endothermic/exothermic article and a technology for a heat transfer enhancing system and method for fabricating heat transfer device. Read more »

Industry Developments: Portable Cooling Systems

 - buildings and rooms constructed to house data centers are getting larger, more congested and warmer. many of these structures have sophisticated thermal management systems featuring high-powered coolers or harnessing cold local water or air. for some needs, however, a portable cooling system can provide a much simpler and less costly solution. these systems can deliver direct cooling relief to equipment hot spots, and some can lower a room?s temperature when a central cooling system is inadequate or nonexistent. self-contained, easily installed, and turnkey, portable coolers offer increasingly advanced features to help keep data center electronics running reliably. Read more »

Thermal Performance of Heat Sinks with Heat Pipes or Vapor Chambers for Servers

 - most blade servers for data and telecommunication systems use air to cool the high power chips inside. as the power level of these chips keep increasing, the pressure is on thermal engineers to design ever higher performance air-cooled heat sinks. in recent years, advancements in manufacturing of thinner heat pipes and vapor chambers have enabled engineers to integrate the heat pipes and vapor chambers into the blade server heat sinks. Read more »

Fan Heat Sinks Technology Review

 - fan heat sinks are heat sinks with an air moving source, usually a fan, integrated or embedded onto or into the heat sink. one key advantages to this configuration of heat sink plus fan is that air can be targeted directly at the heat source. a disadvantage is that the fan can fail, resulting in a lack of air in your thermal design and putting it's performance and life at risk. this technology review article, courtesy of our media sponsor, qpedia, considers some latest awarded patents for this technology including a heat sink with a centrifugal fan, heat sink with heat pipe and fan, and circular heat sink with circular fan. Read more »

EV Battery Thermal Management

 - as electric vehicles and hybrid electric vehicles become more sophisticated, demands are growing for greater battery efficiency and life, and longer driving range. achieving this must include improvements in thermal management. there is a critical need for maintaining optimal battery temperatures. engineers are working on more innovative and effective methods for intelligent thermal management for expensive ev and hev batteries. a battery that can function within the right temperature range will last longer and need fewer charges. this is especially true given current demands for rapid charging, which can heat up batteries faster, thus potentially shortening their life. Read more »

Designing Efficient Fans for Electronics Cooling Applications

 - in modern day equipment racks, the power consumed by the cooling fans represents a significant percentage of the overall system power budget. with the advent of data centers and their large energy costs, the issue of cooling power is exacerbated. it is, therefore, becoming crucial to design and implement methods for reducing data centers power consumption. as an example, a large data center contains about 400,000 servers and consumes 250 mw of power [1]. it has been estimated that about 20 % of the total power supplied to a high end server is consumed by fans. Read more »

Thermal Performance of Thin Flat Heat Pipes

 - a heat pipe is a device with high thermal conductance that can transport large amounts of heat with small temperature differences between its hot and cold ends. it is normally used to transport heat from one location to another location or to smooth the temperature distribution on a solid surface. the heat pipe is widely used in aerospace applications, military devices, temperature control system, and personal computers. this article explores the manufacturing process, properties and capabilities of thin flat heat pipes. Read more »

Technology Review: Air Delivery Systems

 - in this months technology review we cover a review of the technology and awarded patents for air delivery systems. three are highlighted: low-profile axial-flow single-blade piezoelectric fan; blade for a cooling fan; piezofan and heat sink system for enhanced heat transfer. this technology review comes to coolingzone courtesy of our media sponsor, qpedia. we are presenting selected patents that were awarded to developers around the world to address cooling challenges. after reading the series, you will be more aware of both the historic developments and the latest breakthroughs in both product design and applications. we are specifically focusing on patented technologies to show the breadth of development in thermal management product sectors. please note that there are many patents within these areas. limited by article space, we are presenting a small number to offer a representation of the entire field. you are encouraged to do your own patent investigation. further, if you have been awarded a patent and would like to have it included in these reviews, please send us your patent number or patent application. in this issue our spotlight is on air delivery systems using piezofan or standard fans. there is much discussion about its deployment in the electronics industry, and these patents show some of the salient features that are the focus of different inventors. Read more »

Smartphone Cooling Systems

 - when it comes to water and smartphones, the topic usually concerns how resistant a phone is to incidental water, or even to full immersion, e.g., in the bathtub. today, however, water is being seen as more of an ally of reliable function because of its utility in cooling hot internal components. with increasingly processor-intensive apps being used on mobile devices, the powerful chipsets in smartphones are running hotter than ever. many desktop computers and larger, powerful computing systems use water cooling to keep their cpus from overheating. now, smaller versions of these cooling systems are being employed in warm smartphones. Read more »

Next Generation Processor Cooling and Power Trends

 - cmos semiconductor technology has been faithfully following moore's law for several decades now. this law states that the number of transistors per unit area doubles about every year [1]. this trend is likely to continue in the foreseable future. in addition, two other technical trends will accompany the roadmap of future processors: manycore chip multiprocessors and 3d integration. as thermal engineers, it is important to investigate the cooling options available for future 2d and 3d chip multiprocessors and to identify the limits of different cooling solutions and their implications on future processor architectures. one particular question that needs an answer is if or when air cooling will become inadequate? since the 1980s, it has been predicted that air cooling will not suffice for future high power density ics, yet today the main method of cooling electronics remains active air cooling. Read more »

Technology Review: Innovative Cold Plate Designs 2007-2012

 - qpedia, a media sponsor of coolingzone, continues its review of technologies developed for electronics cooling applications. qpedia is presenting selected patents that were awarded to developers around the world to address cooling challenges. after reading the series, you will be more aware of both the historic developments and the latest breakthroughs in both product design and applications. we are specifically focusing on patented technologies to show the breadth of development in thermal management product sectors. please note that there are many patents within these areas. limited by article space, we are presenting a small number to offer a representation of the entire field. you are encouraged to do your own patent investigation. further, if you have been awarded a patent and would like to have it included in these reviews, please send us your patent number or patent application. in this issue our spotlight is on innovative cold plate designs. there is much discussion about its deployment in the electronics industry, and these patents show some of the salient features that are the focus of different inventors. Read more »

Industy Developments: Piezo Electric Cooling

 - the first piezoelectric effects were discovered in the late nineteenth century, when it was found that deforming certain materials, e.g. crystals and ceramics, would generate a voltage. soon after, the reverse effects were seen: applying electrical current to certain materials caused them to deform. this became known as the inverse or converse piezoelectric effect, where the application of an electric field creates mechanical deformation. Read more »

Immersion Liquid Cooling for Servers in Data Centers

 - a data centers is a large infrastructure used to house large quantities of electronic equipment, such as computer servers, telecommunications equipment, and data storage systems, etc. the datacenter requires non-interrupted power, communication and internet access to all equipment inside, it also has dedicated environment control system which provides appropriate working condition for the electrical devices hosted inside. Read more »

Enhancing Heat Sink Performance Using Thermoelectric Coolers

 - with the increase in the power dissipation of components and the parallel reduction of their size, engineers and researchers across the globe have been predicting that the era of air cooling might come to an end. even though in some applications, with very high power dissipations such as igbts, air cooling may not be adequate and liquid cooling is a must; air cooling will continue to be the first choice for most electronic cooling applications for many years to come. advances in air cooling continue to extend its use and the implementation of thermoelectric coolers (tecs) in heat sink applications is one such effort. Read more »

Heat Transfer In Metal Foam Heat Exchangers

 - metal foams have found increasing use in thermal management. their surface area is much larger than regular finned heat sinks, making the available surface area for heat transfer attractive. on the other hand, their increased pressure drop and interfacial resistance makes them vulnerable to not being useful for some applications. understanding the underlying physics behind the mesh heat sink and heat exchangers is a necessity for using them effectively in thermal management. savery [1] used comsol [2], which is a commercial cfd finite element software to simulate the natural convection in a metal foam heat sink. before embarking on presenting the equations that govern the flow and heat transfer in porous media, it is helpful to understand the characteristics of porous media. Read more »

Waste Heat Recovery of Electronic Equipment

 - with the rapid increase of power dissipate in electronics' components, the energy needs for cooling are also increasing at rapid page. during the process of activating and cooling components, heat is generated and dumped into the atmosphere. this wasted energy on a global scale is significant and, if only a percentage of this "waste" heat can be recovered, it would account for a significant amount of energy reclamation. this paper describes a successful method to reclaim such energy. Read more »

Synthetic Air Jet for Electronics Cooling

 - jet impingement is one of the more effective solutions for cooling electronic devices, as it can create a very high heat transfer rate on the impacting surface. as the power density of modern chips keeps increasing, using fluid jets as a thermal management method shows great potential. in most air jet cooled electronic systems, continuous jets are created by using fans, blowers or a high pressure air jet source. for the continuous jets, parameters such as jet configuration (free -surface jet, submerged jet or confined jet), the spacing between the jet outlet and the impingement surface, the magnitude of the jet velocities, the angle of impingement, etc. are major factors affecting the jets cooling performance. to enhance jet impingement heat transfer, a pulsed air jet impingement configuration was investigated by some researchers who are looking for exciting the coherent structures in the jet flow and breaking the boundary layer on the impingement plate. however, creating pulsed jet impingement by traditional methods requires complicated mechanical design and flow routing arrangement. Read more »

Heat Sink Manufacturing Using Metal Injection Molding

 - rapid developments in microprocessor technology have led to a need for the efficient high-volume production of advanced heat sink devices. the metal injection molding (mim) process is highly suited to the production of the next generation of these high performance products. similar to plastic injection molding, mim offers product designers a greater freedom to adapt traditional heat sink designs, in order to offer both increased thermal efficiency and substantial cost savings in high volume production. Read more »

Honeycomb Heat Sinks for LED

 - to better cool some led lights, ma et al, proposed to use the honeycomb heat sinks as a thermal management device. they suggested that the honeycomb heat sinks have a larger surface area and smaller weight than other led heat sinks. numerical simulations and experimental tests were conducted to investigate the performance of the honeycomb heat sinks under natural convection condition. their findings are discussed in this article. Read more »

Ultra Thin Flat Heat Pipes for Thermal Management of Electronics

 - the decrease in size of the new generation of portable electronic devices imposes a severe constraint on their incorporated thermal management devices. thinner and more compact laptops, for instance, require ultra thin form factor cooling devices. for example, newly developed mobile processors in bga packages must be thin enough for use in notebooks only 18 mm thick. traditionally, flat heat pipes have been used for this type of application. Read more »

Pin Fin Heat Sink Performance Under Air Jet Impingement

 - jet impingement is one of the most efficient methods of cooling hot electronic devices, as it can create a very high heat transfer rate on an impacting surface. as the power density of modern chips keeps increasing, using air jet impingement to remove heat from a heat sink or electronic components has been employed on numerous applications. the most common example is the fan sink with a fan mounted on top of heat sink to create air jets. Read more »

Recent Innovations in Axial Air Movers

 - active cooling of electronics typically implies the use of fans to move air to cool electronic components, chipsets or racks. active heat sinks include an integral fan that blows air across the sink fins for more effective cooling performance. there have been a number of developments in this space that are important to thermal engineering design and our article covers this important topic. Read more »

Graphene Fillers Promise Major Improvements in TIM Thermal Conductivity

 - thermal interface materials (tims) facilitate the transfer of heat from hot chips to heat spreaders. tims have soft material components that fill into the air gaps between the package and spreader joining surfaces. one type of tim is a phase change material that contains a high viscosity fluid, e.g. paraffin, as well as thermally conductive fillers that provide the heat transfer. but, traditional fillers, typically particles of alumina or glass, are inherently limited in their abilities to conduct heat. as a result, thermal transfer into spreaders is limited and chips may not be cooled to the levels they require. with power dissipation rising, there is a need for tims with higher levels of thermal conductivity. Read more »

Basic Finite Volume Concepts in Computational Fluid Dynamics

 - computational fluid dynamics (cfd) has become an essential tool in modern engineering analysis and thermal management, leading to faster solutions and an increase in productivity. it is also a very rich field that has benefitted from decades of work to improve its accuracy and speed. thus, today, engineers have at their disposal an array of different choices of cfd packages to solve theirthermal problems. it is beneficial, however, if the user possesses a basic understanding of the underlying concepts, so that he or she can utilize the cfd software more effectively. Read more »

Optimization of Microchannel Heat Exchangers

 - it's no secret that power densities in electronics have continued to rise, and researchers have been forced to explore new thermal management technologies to keep those electronics from overheating. the thermal management challenge becomes even more complicated by the trend towards miniaturization and the prevalence of mobile electronics. microchannel heat exchangers hold much promise as a solution to these problems. Read more »

Liquid Cooling for Computer Servers

 - to meet growing data center cooling challenges, many organizations and are turning to liquid cooling. liquid cooling is a powerful alternative to ambient air cooling, as water can carry thousands of times more heat than air. rather than tweaking or re-engineering existing methods, disruptive cooling technologies are transforming the entire data center industry with wholesale changes at even the most basic level. the writer explores some of these technologies and industry developments. Read more »

Are More Efficient Heat Sinks Really More Costly?

 - the question arises, why pay more for a higher-efficient heat sink that is also smaller and lighter in weight, especially in cases whereby a simple, larger but heavier cast or extruded heat sink can also do the job? in most cases, the single-piece part price is the main driver as to why engineers and purchasers stay with lesser effective solutions. this is generally because they believe that they are saving money for the company in the long-run. but, is this really true? Read more »

Jet Impingement Cooling Using FC-72

 - jet impingement is one of the most efficient solutions for cooling hot electronic devices, as it can create a very high heat transfer rate on an impacting surface. direct cooling of high-power chips, by using jet impingement via dielectric liquids, shows great potential even though its implementations are more complicated than traditional air and liquid impingement cooling methods. unlike the conventional air and liquid impingement cooling which rely on heat sinks or cold plates, using dielectric liquids in intimate contact with silicon devices eliminates, deleterious effects of solid-solid interface resistances and thermal impedance created by thermal interfere materials. Read more »

Industry Developments: Thermally Conductive PCBs

 - a wide range of printed circuit board materials are available for electronic assemblies requiring heat management characteristics (high-power devices, rf and wireless, lighting/led boards, etc.). in widening use are metal-clad pcbs with a standard dielectric, and metal cores of various thicknesses of aluminum and copper. providers of these pcbs offer tight machining tolerances and high-quality fabrication services for effective thermal management. Read more »

TEC Selection in Thermal Management

 - with the push towards reducing component size, increasing power dissipation and lowering junction temperature, engineers must utilize different and more effective means for achieving their goals. thermo electric coolers (tecs) are one such means to achieve their ends. tecs have been on the market for decades and their application in component cooling can be attractive, if they are designed properly or chosen correctly. even though their cop is much lower than a carnot cycle efficiency, they can solve some problems if the fundamentals of a tec are well understood by the engineering team. Read more »

Direct-Bond-Copper Aluminum Nitride Microchannel Heat Sink for IGBT Modules

 - the advancement in semiconductor technology has coerced engineers into looking for more innovative and effective methods to cool semiconductor devices with increasing power density. the continuing efforts towards the shrinking of the metal oxide semiconductor field-effect transistor (mosfet) and the insulated gate bipolar transistor (igbt) gate size have made it impossible for standard electronics packages and pure air-cooled devices to handle the heat load dissipated by some high-power devices, such as high end cpus, power transistors, dsp chips, etc. Read more »

Technology Review - Cold Plate, 2001 to 2003

 - qpedia continues its review of technologies developed for electronics cooling applications. we are presenting selected patents that were awarded to developers around the world to address cooling challenges. after reading the series, you will be more aware of both the historic developments and the latest breakthroughs in both product design and applications. Read more »

Industry Developments: Thermal Gap Fillers

 - thermally efficient pads and fillers have become vital in meeting demands to increase the performance and reduce the size of electronic assemblies, such as power supplies and control units, without compromising reliability. today's thermal materials are typically ceramic-filled silicone elastomers, which are easy to handle. they also conform well to the shape and surface texture of heatsinks or electronic components. and, they have high thermal conductivity relative to the still air they're designed to eliminate. Read more »

Application of Thermoelectric Coolers in Thermal Management

 - with the increase in power dissipation and the shrinkage of package sizes, air cooling is getting to its limit or soon will reach a point at which liquid cooling becomes inevitable. in order to comply with moore's law, higher heat transfer mechanisms are needed to achieve the goal. in some applications with limited space or lack of refrigerated liquid, liquid cooling by itself might not even be enough. in these circumstances tec can play a vital role. in this article we will look at some work done by researchers using tec in the liquid cooling arena. Read more »

The Thermal Resistance of Microchannel Cold Plates

 - the trend towards ever higher power dissipation rates has pushed liquid-cooled cold plate designers to look for more effective methods and structures to transfer heat from device to liquid. this paper studies how the channel size and material affects the overall thermal resistance of cold plate. when designing a cutting edge cold plate, engineers should pay a lot of attention to pressure drop, pumping power, system complexity and reliability while pursuing high performance. Read more »

Technology Review - Loop Heat Pipe, 2010 to 2012

 - in this issue, our spotlight is on loop heat pipes. there is much discussion about their deployment in the electronics industry, and these patents show some of the salient features that are the focus of different inventors. Read more »

Industry Developments: Thermal Potting Compounds and Epoxies

 - potting compounds may be used to provide an environmental barrier, dielectric protection characteristics, thermal conduction paths, and structural enhancement of an assembly or component. many thermal epoxies are designed for the demanding needs of die-attach heat sink bonding and surface mount applications. this article explores the latest potting compound products on the market. Read more »

Accelerated Reliability Testing

 - today's manufacturers face strong pressure to develop new, cutting edge technology products in record time, while improving productivity, product field reliability and overall quality. the requirements of higher reliability have increased the need for more up-front testing of materials, components and systems. in this article, the author explores the different kinds of accelerated tests currently employed in reliability testing. Read more »

Heat Sinks and Heat Exchanger Fin Optimization

 - as the electronics industry continues to use components dissipating more and more power, new heat sink solutions must be able to accommodate large heat fluxes while keeping the same spatial dimensions. finned heat sinks and heat exchangers are largely employed in many engineering fields, and this demand spurs researchers into devising and testing new geometries for the heat sinks. this article examines the advantages and disadvantages of different fin geometries. Read more »

Technology Review: Loop Heat Pipes, 2001 to 2005

 - in this issue, our spotlight is on loop heat pipes. there is much discussion about their deployment in the electronics industry, and these patents show some of the salient features that are the focus of different inventors. Read more »

Industry Developments: Recent Innovations in Axial Air Movers

 - at the basic level when considering an axial fan, for most applications the main concerns should be noise, air flow (cfm), static pressure, physical size, bearing type, motor type, motor protection and life expectancy. there are models of axial fans that will meet particular needs in any of these areas. a thorough supplier search or discussion with a thermal management expert will usually result in the choice of a better suited axial fan. Read more »

Turbulent Models for CFD Simulation in Electronics Cooling

 - commercial cfd software solves both fluid flow and heat transfer throughout the system, which enable engineers to predict air flow distribution, chip junction temperature, local heat transfer coefficient and heat sink performance, etc. due to the complex geometries of components on pcbs and the forced convection cooling of high power chassis, the air flow is turbulent in nature for most cases. to accurately predict the airflow, engineers using the cfd software are required to have certain knowledge of turbulent models to select an appropriate one for their application. Read more »

Advanced Cooling of Electronics Using Liquid Metal as the Coolant

 - in applications where air cooling is not adequate or not practical, liquid cooling can play a significant role. liquid cooling can be achieved either using conventional pumps to run some sort of liquid, such as water/ethylene, or by utilizing liquid metal instead of conventional liquids. using liquid metals has the advantage of employing an mfd (magneto fluid dynamic) pump with no moving parts, free of vibration. Read more »

Technology Review: Liquid Cooling, 2010-2011

 - this is the second article in the new series. qpedia reviews the different technologies that have been developed for electronics cooling applications. further, this series looks at the patents awarded to developers for liquid-air hybrid cooling. Read more »

Graphene Fillers Promise Major Improvements to TIM Thermal Conductivity

 - traditional fillers, typically particles of alumina or glass, are inherently limited in their abilities to conduct heat. as a result, thermal transfer into spreaders is limited and chips may not be cooled to the levels they require. with power dissipation rising, there is a need for tims with higher levels of thermal conductivity. graphene-filled tims may be the first major breakthrough to the continuing need for higher performing interface materials. Read more »

Heat Transfer in Metal Foam Heat Exchangers

 - metal foams have found increasing use in thermal management. their surface area is much larger than regular finned heat sinks, making the available surface area for heat transfer attractive. on the other hand, their increased pressure drop and interfacial resistance makes them vulnerable to not being useful for some applications. in this article, the goal is to gain an understanding of porosity and permeability of metal foams and their role in electronics cooling. Read more »

Application of a Thermoelectric Cooler in Chip Temperature Reduction

 - thermoelectric coolers (tecs) are semiconductor modules which use the peltier effect to create a heat flux between the junctions of two different types of materials. because of their simplicity, reliability, and miniaturized size, researchers are finding intuitive ways to use tecs to lower the chip temperature. this article explores what is being done to improve their performance and extend their application in electronic cooling. Read more »

Technology Review: Liquid Cooling, 1992-2003

 - in a new series, qpedia reviews the different technologies that have been developed for electronics cooling applications. this series looks at the patents awarded to developers in industry and academia around the world who are actively involved in addressing cooling challenges. Read more »

Performance of Fans and Blowers in Thermal Management

 - fans have been traditionally been used in cooling devices and will be used for the foreseeable future, since their implementation is the easiest. as the world becomes more concerned about energy uses and efficiencies of the systems, it is imperative that the designer takes into account all the factors that influence the performance of the fan. Read more »

Liquid Cooling Utilizing Stacked Microchannels

 - moore's law, which states that the numbers of transistors that can be placed inexpensively on an integrated circuit will double every 18 months, has been valid for more than 50 years. to extend moore's law to the foreseeable future, it will require a change from mere transistor scaling to novel packaging architectures such as so-called 3d integration, the vertical integration of chips and innovative cooling solutions. Read more »

Industry Developments: Liquid Cooling of Data Center Servers

 - most data centers have relied on ambient air cooling solutions (alternating cool and hot rows) to meet their cooling needs. however, ambient air cooling solutions are often unable to handle high heat loads, are not targeted and can be cost and energy inefficient. as high power applications and server densities increase, new ways are needed to dissipate heat. Read more »

Technology Review: Liquid Cooling, 2003-2009

 - in a new series, qpedia reviews the different technologies that have been developed for electronics cooling applications. this series looks at the patents awarded to developers in industry and academia around the world who are actively involved in addressing cooling challenges. Read more »

Using a Refrigeration System for Electronic Cooling

 - the advance in semiconductor technology and leap in transistor density has coerced engineers into looking for more innovative and effective methods to cool semiconductor devices loaded with increasing power density. traditionally, the air-cooled heat sinks dominate the electronic cooling market, due to their simple design, low cost, high reliability and versatility. one of the promising cooling techniques is refrigeration. Read more »

Effect of Flow Oscillation on Enhancing Heat Transfer or a 3D Object

 - with the increase in heat dissipation of components and management of heat extraction, innovative cooling solutions are proposed on a continuous basis. the active researchers in this area are trying to come up with new technologies to increase the heat transfer and remove the heat from the component at a reasonable cost. one of the techniques that might be useful is flow induced oscillation that enhances the heat transfer. Read more »

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