Problem Statement And Methodology Engineering Essay

Problem Statement And Methodology Engineering quizRefrigeration or Cooling may be defined as the process of removing genus Oestrus. This process may be accomplished by exploitation one of the refrigeration formations vapor muscular contraction, submergence or thermo galvanic refrigeration systems. The first twain systems need laid- endure and low pressure steads of a working fluid to complete the refrigeration cycle. The thermoelectricalal refrigeration system, however, recitation of goods and servicess electrons preferably than refrigerant as a wake carrier. (Davis, 2005)thermoelectrical callers ar greatly needed, particularly for the developing countries situation where long life and low attention be needed. In this aspect, thermoelectrics lowlifenot be challenged, in spite of the fact that their coefficient accomplishment is not as noble as for a vapor compression cycle. thermoelectrical refrigerators commence the advantages of universe sensitive, ligh tweight, rugged, reliable, and insensitive to orientation, noiseless, portable and low personify in mass production. (Davis, 2005) Thermoelectric cooler has been widely used in legions, aerospace, instrument, and industrial or commercial products, as a cool down cunning for specific purposes. This technology has existed for roughwhat 40 twelvemonths. (Riffat, 2000) Many researchers ar bear on just about the physical prudishties of the thermoelectric real(a) and the manufacturing technique of thermoelectric modules. In addition to the improvement of the thermoelectric material and module, the system analysis of a thermoelectric refrigerator is equally important in designing a game- carrying out thermoelectric refrigerator. (Huang, 2000)The change flux gene graded in the processor fleck is rising day by day at a genuinely fast rate with development because of reduction in processor sizes and round cadence of warmth load generated at the chip. Consequently, it is be coming a ambitious task for researchers to handle much(prenominal) enormous amounts of rage fluxes.Moores had proved that deed of transistors on a integrated circuit is change magnitude exponentially year after year .So rage load in the central processing unit as well as increases at the equivalent rate with the increase in the speed provided the size of the chip today which we normally talk about is of the found of mm which is in turn making problem more complicated. The high light up generation inside the CPU may sequel in slowing down the computation speed, hardship of the processor chip, gate oxide breakdown, heart on screen resolution and some more electrical failures as well as mechanical failures (Davis, 2005)Presently in CPU truly complicated designs of railway line cooled waken come abouts argon used which dissipates alter to the environment by fluxing large volumes of note. These heat slip aways go through dickens major(ip) shortcomings.Due to sp ace constrains bearing should be thrown at in truth high velocities and to maintain much(prenominal) velocities big size fan has to be used.Also, the air silklike at high velocities creates a lot of noise.Moreover, in air cooled units there is no active temperature reduction device so we cant go beneath the close temperature. As a result working at high speeds in the hot ambient conditions had pass away extremely difficult.Chip temperature reduction is one of the bottlenecks in the high density electronics. There is need of some better chill system techniques for the same. So, now a day researchers are working a lot on liquifiable cooled systems, because they have nearly 10 times (Davis, 2005) the heat transfer coefficient than that of air cooled ones. In piss based mobile cooling systems, the heat is wield to piss avoid by some cooling device from which piddle offsprings away the heat to finally throw it in the surroundings . The most(prenominal) commonly used d evice to pump heat to water block in such(prenominal) system is investigator (Thermoelectric coolers). detective consumes their own function and cool down the chip by extracting the heat from it and transferring it to the water block. water runs inside the channel in the water block and takes away the heat from it. The hot water is further cooled in the condenser. With the help of Thermoelectric water cooling system the chip temperature can be easily do to go below ambient temperature which is not possible by the real systems, and thus the CPU can be made to operate at high speeds and high loads in notwithstanding hot ambient conditions. Thus TEC have potential opportunities for chip cooling and can prove very legal if a proper system is veritable for the same.1.2 Problem statementChip cooling is one of the bottlenecks in high density electronics. An enormous amount of heat flux is generated by the recent processor chip. Nowadays many complicated designs of air cooled hea t sinks are used, but off late the heat fluxes have attained such a direct that to handle them very large volume flow rate of air is deald. So due to space constraint, in decree to achieve large flow rates, air should be blown at very high velocities which in turn result in change magnitude levels of noise. Another major disadvantage of air cooling is that we cant go below ambient temperature and as a consequence, tendency of chip failure in the computers working in ambient condition of about 35C 45C increases a lot.For all these reasons it has become unvarnished that the heat fluxes have reached such a level that air cooling cant handle them efficiently. Thus the present scenario necessitates the use of active cooling devices. Thermoelectric coolers having the ability to cool below ambient and having advantage of being compact, light weight, free of moving parts and precise temperature control have high potentials for chip cooling.It is known that the temperature of the therm oelectric module is the main banner for its reliability and carrying out. The temperature rise of the hot side preceding(prenominal) ambient is dependant on the thermic bulwark of the running that the heat sink. Reducing the thermic resistance of the heat sink contributes to the reduction of the thermal resistance of the path and hence an increase in the performance. So a liquid heat exchanger with spiral flow passage having dimples is used. Dimples result in setive heat transfer by creating turbulence and thus enhancing the performance of the system.1.3 seek ObjectivesUnderstanding the basics of Thermoelectric coolers, working of Thermoelectric Cooling Systems and parameters that governs the performance of such systemsDesign, fabrication and development of an efficient thermoelectric cooling system for computer chipsCarrying out experimentation and analysis of the performance of the developed system1.4 Methodology1.5 Work PlanThese are some of the important tasks that would be performed during this researchUnderstanding the basic concepts of thermoelectric coolingStudy of the animated CPU cooling techniquesLiterature review regarding the topic and study about the erect due dimples along the flow of waterDeciding the miscellaneous parameters for which system has to be designedDeciding about the thermoelectric module which entrust produce the desired cooling operationDesign of the observational set up and identification of the various equipments to be required grocery store survey for all the required equipmentsProcurement of the equipmentsDesign and fabrication of the dimpled water blockDesign and fabrication of the heat exchangerPreparation of the experimental set upCarrying out experiments and obtaining the resultsAnalysis of resultsChecking out the performance of the thermoelectric module usedComparison of the designed water block with some commercially existing water blockDiscussions and conclusionReport piece of writing1.6 Expected Outcome sAn understanding of the application of thermoelectric cooling systems would be developed. burning(prenominal) advantages of the thermoelectric cooling systems in incumbent scenario of high density electronics would be presented. The complete thermoelectric cooling unit for CPU chip would be designed, fabricated and tested for the desired loadsChapter 2LITERATURE reexamination2.1 The History of ThermoelectricsIn 1821, Thomas Seebeck discovered that a continuously flowing current is created when two wires of different materials are joined unitedly and heated up at one end. This idea is known as the Seebeck Effect (Figure 1.1). The Seebeck core has two main applications including temperature measurement and office staff generation. (Global Techno Scan, nd)Figure 1.1 Seebeck EffectS= dV / dTS is the Seebeck Coefficient with units of Volts/KS is positive when the educational activity of electric current is same as the direction of thermal currentIn 1834, a French watchmaker and p art time physicist, Jean Peltier found that an electrical current would produce a temperature slope at the pairing of two dissimilar metals. This effect is known as the Peltier Effect. This idea forms the basis for the thermoelectric refrigerator (Global Techno Scan, nd)Figure 1.2 Negative Peltier effecta) For When current is allowed to pass with n-type semiconductor shown in above circuit, high zip fastener electrons move from remunerate to left resulting in cooling of far end. Thermal current and electric current flow in opposite directions (Global Techno Scan, nd)Figure 1.3 Positive Peltier effectb) For 0 Positive Peltier coefficientWhen current is allowed to pass through p-type semiconductor shown in above circuit, high vital force holes move from left to right resulting in alter of far end. Thermal current and electric current flow in same direction (Global Techno Scan, nd)q=*j, where q is thermal current density (Heat flux) and j is electrical current density.Also, = S *T (Volts) Peltier coefficientWhere, T is the Absolute TemperatureScottish scientist William Thomson (later gentle Kelvin) discovered in 1854 that if a temperature difference exists mingled with any two points of a current carrying conductor, heat is either evolved or absorbed depending upon the material. If such a circuit absorbs heat, then heat may be evolved if the direction of the current or of the temperature gradient is reversed.2.2 Thermoelectric RefrigerationA thermoelectric device is one that operates on a circuit that incorporates both thermal and electrical effect to convert heat cleverness into electrical energy or electrical energy to a temperature gradient. Thermoelectric elements perform the same cooling function as Freon -based vapor compression or absorption refrigerators. Energy is taken from a region thereby reducing its temperature. The energy is than rejected to a heat sink region with a higher(prenominal)(prenominal) temperature. Thermoelectric elements are in a totally solid state, opus vapor cycle devices have moving mechanical parts that require a working fluid (Tellurex, nd)Thermoelectric modules are small, sturdy, quiet heat pumps operated by a DC precedent source. They usually last about 200,000 hours in heating mode or about 20 historic period if left on cooling mode. When power is supplied, the surface where heat energy is absorbed becomes stone-cold the opposite surface where heat energy is released becomes hot. If the sign of the zodiac of current flow through the module is reversed, the cold side will become the hot side and vice-versa. Thermoelectric modules can also be used as thermocouples for temperature measurement or as generators to supply power to spacecrafts and electrical equipment. (Tellurex, nd)Thermoelectric devices can also be used as refrigerators on the bases of the Peltier effect. To create a thermoelectric refrigerator, heat is absorbed from a refrigerated space and than rejected to a warmer environme nt. The difference between these two quantities is the net electrical work that needs to be supplied. These refrigerators are not overly popular because they have a low coefficient of performance. The coefficient of performance for thermoelectric refrigerators can be calculated by dividing the cooling effect by the work input. (Tellurex, nd)2.3 SemiconductorsThe semiconductor materials are N and P type, and are so named because either they have more electrons than necessary to complete a perfect molecular lattice structure (N-type) or not affluent electrons to complete a lattice structure (P-type). The extra electrons in the N-type material and the holes left in the P-type material are called carriers and they are the agents that move the heat energy from the cold to the hot junction. Heat absorbed at the cold junction is pumped to the hot junction at a rate proportional to carrier current passing through the circuit and the digit of couples. Good thermoelectric semiconductor mat erials such as bismuth telluride greatly impede conventional heat conduction from hot to cold areas, withal provide an easy flow for the carriers. In addition, these materials have carriers with a subject for transferring more heat. Since semiconductors were found to have large Seebeck coefficients, good electrical conductivities, and pitiful thermal conductivities, one has made a breakthrough in the use of the Peltier-effect in thermoelectric devices to produce refrigeration. Currently, thermoelectric refrigerators, made of semiconductor, materials, have many interesting applications because of their small size, simplicity, quietness and reliability.2.4 Basic Working Principle of Thermoelectric CoolersThermoelectric coolers are semiconductor devices which works on the principle of Peltier effect (Haung, 2005) i.e. when a current is passed between the junctions of two dissimilar materials then a temperature difference is created between the two junctions. In thermoelectric coolers we have a P type and an N type semiconductor connected together when we pass the current, at the cold junction electrons travel from P side to N side as P type being at press down energy level and N type at higher energy level. So when electron travels it absorbs energy at the cold side. also at the hot side electron travels from N side to P side thereby releasing the energy. And in this way a temperature gradient is established between hot side and cold side (Haung, 2005)2.5 Advantages of Thermoelectric CoolersThermoelectric coolers have some unique advantages over other cooling systems. The various advantages are (Chien, 2004)Ideal for localized cooling due to small sizeHighly controllable cooling powerConvenient power supplyPrecise temperature controlSub-ambient cooling depicted objectSpot coolingCompact, Quite, and free of moving partsLow maintenance2.6 A emblematic thermoelectric cooling systemFig. 1 shows working of a thermoelectric system. The heating and cooling functio ns of the thermoelectric system can be interchanged by reversing the polarity of the direct current applied to it. Capacity control in a thermoelectric system can be achieved by alter the electromotive force applied to the couples either by a variable voltage control or by switching series and parallel circuits. As the voltage drops, the temperature difference between the hot and cold side is reduced. (Chien, 2004)On the cold side of the module we have the heat source from which heat is to be removed and on the hot side we have a heat sink which finally throws the heat into the ambient. Design of the heat sink is an important parameter for improving the performance of the thermoelectric module. For many applications, the advantages of TEC outweigh its main disadvantage of low coefficient of performance. (Chien, 2004)Figure 2.1 Thermoelectric cooler (Chien, 2004)2.7 Thermal Parameters Governing Performance of TECThe selection of a thermoelectric for a particular application is main ly dependent on the tierce important parameters. These are temperature of the hot surface (Th), the temperature of the cold surface (Tc) and the amount of heat to be extracted at the cold side of the module (Qc) (Haung, 2005).The heat sink is attached at the hot side of the module where the heat gets released when the DC power is applied to the module. The hot side temperature of the module art object using a air cooled heat sink whether natural or forced convection, can be found out using below equations (Haung, 2005)Th = Tamb + Rth(Qh) (1.1)Qh = Qc + Qp (1.2)The temperatures rise above ambient, of the hot side, takes place because of the thermal resistance of the heat. If we know the thermal resistance of the heat sink then the universal estimates of the rise in temperature above ambient are as state below (Haung, 2005)20C to 40C in lesson of Natural Convection10C to 15C in occurrence of Forced Convection2C to 5C in suit of clothes of Liquid Cooling (In this case is the ris e above the liquid coolant temperature)The performance coefficient for a thermoelectric cooling system can be calculated with the help of the following equation2.8 Application of thermoelectric coolingTEC (Thermoelectric Cooler) is different from conventional compression refrigeration there are no moving parts. Since there are no moving parts, there is aught to wear out and nothing is generating noise. There is no refrigerant to take away so the problem of handling a two-phase change over is simplified. twinge tight tubing is replaced by electrical wiring. There is no ozone layer hazard (Melcor, nd). Thermoelectric coolers offer the potential to enhance the cooling of electronic module packages to reduce chip operating temperatures or to allow higher module powers. Thermoelectric coolers also offer the advantages of being compact, reliable, and their degree of cooling may be controlled by the current supplied. Unfortunately, compared to vapor-compression refrigeration, they are limited in the heat flux that they can accommodate and exhibit a lower coefficient of performance (COP). These two limitations have generally limited thermoelectrics to niche.The thermoelectric coolers are used in the electronics of the cruise missile, critical equipment on aircraft, critical tv camera components in a pod aircraft navigation system and many military applications. Thermoelectric coolers provide compact heat exchangers that are not attitude-sensitive and do not contain excessive tubing and fittings that can be unresistant to vibration2.9 Previous Work done at International levelTill today air coolers are meeting the needs of CPU cooling, with the change magnitude size of heat sinks and an increase in fan speed. The emblematic resistance of air coolers with high fan speeds is 0.2C/W (Bar Cohen, 2000). nevertheless with further increase in the heat flux, air cooling techniques seems to be diminishing because of the limitations already mentioned. The next best soluti on to the problem is the use of liquid cooling techniques as the liquids have relatively very high convective heat transfer coefficients then air and thus minimizing the thermal resistance. The liquid cooling systems involves water block for efficient heat transfer to the liquid.Experiments have been carried out by mounting water blocks directly over the CPU chip and they have shown to be very efficient then the air cooled techniques. With the use of direct water-cooling techniques the chip temperature can be kept at 30C for an ambient condition of 25C with a CPU load of 60W whereas with air cooling it goes to 45C (Bar Cohen, 2000). still with the development of thermoelectric coolers it had made possible to take the chip temperature even below ambient. Thermoelectric Coolers have unique advantages over other cooling devicesChein and Huang (2004) studied usage of thermoelectric cooler for electronic cooling. The cooling capacity, junction temperature, coefficient of performance (COP ) of TEC and the required heat sink resistance at the hot side were computed. They found that the cooling capacity could be increased as Tc is increased and T is reduced. The maximum cooling capacity and chip junction temperature obtained were 207 W and 88C, respectively. The required heat sink resistance on TEC hot side was found to be .054C/W. A micro channel heat sink ( with size of 55mm x 55mm with channel width of 0.3 mm) using water or air as coolant was also demonstrated to meet the low thermal heat sink resistance requirement for TEC operated at maximum cooling capacity conditions.Huang et al in 2005 studied the distribution of temperature for a thermoelectric cooler under the effects of Joule heating, Fourier Heat conduction, Thomson effect and convection and shaft of light heat transfer. They tried to enalyze and explore some of the important things like Thomson effects influence on the distribution of temperature, on the amount of heat that flows back to the cold side, t he maximum temperature difference attained and the maximum amount of heat extracted etc. They finally concluded that other than improving the thermoelectric materials for increasing the cooling efficiency of the module the other possible way is to take the advantage of Thomson effect this also helps in improving the cooling efficiency.Researches are already going on for incorporating thermoelectric water cooling systems for the CPU. The differentiate factor in using such kind of systems is to have super efficient water blocks with low thermal resistances and to have thermoelectric modules with proper Qmax. Many complicated water block design exist in the present market. The typical thermal resistances of the water blocks used presently for such systems are 0.08C/W (Bar Cohen, 2000).