Thermal Conductivity In Physical Engineering Engineering Essay

Thermal conduction In Physical design Engineering EssayThermal Conductivityis an essential physical airscrew for designing engineering process and measuring the capacity of temperature exchange among arouse and mothy passing through a satisfying mass. Techniques were real to sum caloric conduction in a various materials, hence the objective of this work was to evaluate the feasibility of utilizing different method actings for measuring thermic conduction as intimately as construction of the data-based create to heartbeat caloric conduction of numerous materials with the aim of analysis of the experimental in degreeation. This paper illust drifts the methods of the criterions of caloric conductivity and the process by which it bequeath be brought to a successful culmination.The study of caloric conductivity is important for engineers to survive the nature of thermic energy, temperature and how materials store thermic energy as well as to predict the perf ormance of all given material everywhere its life sentence in a specific application. Also to identify the thermal properties of material so as to assess the performance of certain material and develop efficient come alive carry-forward materials for engines and spacecrafts. This jump out has been taken on board, due to a lack of training and research available on thermal conductivity measuringments. warmheartedness is transferred by three procedures which include conductivity, Convection and Radiation. It engages transfer of thermal energy from one place to another. Thermal conductivity is a signifi toleratet parameter for the analysis of heat transfer through conduction. Conduction takes place due to the particle collision which results in the transfer of thermal energy. Thermal conductivity (k) is an essential property of a material and delimitate as amount of heat transferred in a unit ponderousness of materials in a direction because of change in temperature in contin ual boundary state in a direction perpendicular to the domain of transfer. It is measured in watts per Kelvin per meter (WK-1m-1) and determines the rate of energy spillage through a material.The formulate is titled as study of methods for measurement of thermal conductivity. The project will present the lit recapitulation astir(predicate) the methods as well as conducting an experiment to measure the thermal conductivity of different materials. In addition, a thorough analysis of the experimental data is to be obtained while perform the experiment. The aims and objectives of this report copy as understand of theoretical and experimental methods to measure thermal conductivity of solids, pellucids and suckes. whirl of experimental rig.A thorough analysis of the experimental data.DELIVERABLES3.1 GENERIC DELIVERABLESBased on the module guide, the pursual be the generic deliverables for the academic year 2010-2011Semester ennobleStart DateSubmission DateSemester 1Preliminar y parachuteMonday 27th SeptemberSubmit exteriorize Planning Report + pound BookFriday 26th NovemberSemester 2Dissertation startMonday 31st JanuaryProject seminars and posterWeek commencing 11th AprilSubmission of final report atomic number 90 28th AprilTable 2 Delivery dates set by capital of Jamaica University for entire project3.2 PROJECT DELIVERABLESThe objectives of the project have been place and analysed to set off the following deliverables that will have been produced at the end of the projectConstruction of an experimental rig to measure thermal conductivity of selected material abridgment of the experimental DataComparison of the resultsANALYSIS OF TASKSThe tasks that need to be execute in lodge to achieve the aims of the project, produce the deliverables on schedule and pay back the project to a successful end are as followslit review of conductivity methodsJournalsBooksE-re originationsResearchConductivity methods of solidsConductivity methods of LiquidsConductivi ty methods of gasConstruction of the experimental RigResults ComparisonA literature review will give an insight into various methods of conductivity. Journals, books and other forms of resources will be used to get an understanding of actual concepts of methods and recent accommodations (Advantages, disadvantages and limitation). This will form the base of the construction of the experimental rig. Once the proficiency is selected to perform, various materials will be used to determine their conductivity and hence, the data obtained will be analysed.GANTT CHARTA sequenceline/Gantt chart should be produced, showing the sequence and continuation of the tasks over the project life sentence. A set of key milestones by which the project progress apprise be monitored may in like manner be produced. experience 1 Illustrate an Inital Gantt ChartPROGRESSION TO DATEAs of 26/11/10 the project is at the beginning of the research phase. The literature review has been completed by looking int o journals and online resources. The information collect has been on advantages, disadvantages, limitation, process and setup of the conductivity measurement techniques. I have gathered and read a number of journals relating to conductivity measurements.6.1 systemS TO MEASURE caloric conduction OF SOLIDSIn solids, particles are packed close together by chemic bonds. As heat is transferred, the particles gains energy which results in increase in kinetic energy and particles vibrate against theneighbouring particles ca victimisation transfer of energy amongst the particles. increase in temperature causes increase in thermal conductivity because of the mobility of boundless electrons. Heat energy is transferred in solids by means of fretwork waves, electrical carriers and electromagnetic waves. In metallic elements, the heat is largely transferred by electrical carriers whilst in insulators grille waves carry large amount of heat. The change in magnitude and temperature of th ermal conductivity of solids is due to the dislocations, imperfections of lattice forces and interface between lattice waves and carriers. up to now the change of thermal conductivity varies depending upon materials. A compend of different techniques to measure thermal conductivities is shown on next page.C-THERM TCi SYSTEM fleeting PLANE character reference mannerHOT-WIRE orderNEEDLE PROB METHOD manikin 2 Summary of Techniques to measure thermal conductivity of solidsTransient TechniquesMethods to measure thermal conductivity of solidsSteady State TechniquesComparative MethodPipe analyse MethodCut Bar Method follow anxious coat Method6.1.1 HOT-WIRE METHODIt exists in three forms which include single, cross resistive wires and two parallel wires distant apart. It is apply to measure thermal conductivity of refractories and takes several assumptions into account which pursue as Isotropic framework with Uniform preliminary TemperatureFigure 3 Setup of tropic-Wire method(20 10, Home, Internet, ready(prenominal) at http//www.tpl.fpv.ukf.sk/engl_vers/hot_wire.htm , accessed on 8 October 2010)Hot wire an ideal, infinite snub, and colossal line heat emergeThermal Conductivitycan be intractable by temperature vs. time repartee (K) due to production of heat flux (q) in the wire encircled in the sample. compare 2 measuring rod of thermal Conductivity exploitation Hot-Wire MethodAdvantagesDisadvantagesPreciseExtensive routine of measuring at specified temperatureSimplistic in Configurationnot utilized to measure thermal conductivity of anisotropic material wrinscribed Duration in MeasurementExpertise requiredTable 3 Advantages and Disadvantages of start Method6.1.2 NEEDLE PROB METHODIt is utilized to measure thermal conductivity of materials as well as thermal diffusivity and specific heat. It has the mightiness for in-situ measurements and effective contact of the sample with a single particular gap.When measuring the thermal conductivities of sol ids, samples are outfitted with hole machined in order to enclose probe diameter whilst measuring liquids, probes are pushed into the samples that are to be streaked. This method consists of hollow tube functioning as heat supply element and temperature sensor estrange by means of medium with spunky thermal conductivity and electrical insulation to ensure minor release of radial temperature within the probe.6.1.3 TRADITIONAL TRANSIENT PLANE SOURCE METHOD (TPS)Figure 4 utensil of TPS(2010, Home, Internet easy at http//www.ask.com/wiki/Thermal_conductivity_measurement , 10 October 2010)It is also acknowledged as Hot Disk Method and has several advantages such(prenominal) as accurate, comprehensiveness and ease of application. It consists of a insipid sensor on with continuous double spiral of electrically conducting nickel metal etched out of thin gravel and clad between two work of kapton which provides mechanically stability and electrically insulation to the sensor. The ri se in temperature is caused when current passes through nickel spiral and heat formed is dispersed by sample. Thermal conductivity is measured by recording temperature vs. time response in the sensor.In addition, modified traditional transient plane source method imparts maximum flexibility for scrutinizing thermal conductivity of liquids and powder and control heating element on a support. It utilizes single surface interfacial heat reflectance sensor that provides uniform heat to the sample and functions temporarily.6.1.4 TRANSIENT LINE SOURCE METHOD (C-THERM TCi SYSTEM)It is the infinite line source with constant top executive per unit length and identical in principle to Hot-wire method. In order to determine temperature at a certain quad the following equivalence was taken into considerationEquation 3 Measurement of temperature using C-Therm TCi Systemwhere Q = Power per unit LengthE = exponential function Integralt = Time Passed since Heating6.1.5 PIPE TEST METHODFigure 5 Apparatus of Pipe Test Method(2010, Home, Internet, Available at http//www.evitherm.org/default.asp?lan=1ID=894Menu1=894 , 13 October 2010)It is identical in concept to the follow hot plate method. It consists of a central heater which contains a piston chamber placed in such a way that the heater achieves a constant temperature by means of alteration in spacing of windings in the heater in permutation with the utilization of concise split prophylactic heaters at the ends.It can operate horizontally and vertically by situating the weapon in a stable environment. It employs radial flow to determine thermal conductivity of minerals, plastics etc.6.1.6 COMPARATIVE TECHNIQUEFigure 6 Apparatus of Comparative Technique(2010, Home, Internet, Available at http//www.evitherm.org/default.asp?lan=1ID=893Menu1=893 , 15 October 2010)A test model is crammed under load flanked by two reference materials to each one is bounded by longitudinal guard cylinder. This results in production of tem perature side along with the stack as well as longitudinal heat flows as consequences of temperature gradient in the guard cylinder to that in prototype stack. Therefore, the thermal conductivity is measured by recording the engagement in temperature across the reference and test sample. It has several advantages which pursue as variedSimple in implementationAdaptableIt is also cognize as the workhorse of the thermal conductivity field and can be utilized to measure homogenous and heterogeneous composite solids.6.1.7 GUARDED HOT-PLATE METHODFigure 7 Apparatus of Guarded Hot Plate Method(2010, Home Internet, Available at http//www.azom.com/details.asp?ArticleID=2667 , 16 October 2010)The test material is positioned on a flat plate heater with electrically heated inner plate surrounded by guard heater. Its function is to maintain similar temperature at virtually(prenominal) sides of the gap extricating the main and guard heaters as a result, prevention of squinty heat flow an d heat energy flows in the direction of sample. deliberate direct current is functioned to the hot plate and numerous temperatures across cold plates and heater is controlled in order to give off constant temperature at the sample surfaces. Hence, the accuracy of thermal conductivity measurements is dependent on saving of constant temperature conditions and is measured by Fourier heat flow equation Equation 4 Measurement of Thermal Conductivity using Guarded Hot plate methodwhere W = Electrical Power InputdT = divergency in temperature across the specimensd = Sample thickness6.1.8 CUT-BAR TECHNIQUEFigure 8 Apparatus of Cut-Bar Technique(2010, Home, Internet Available at http//www.anter.com/TN67.htm , 17 October 2010)It is utilized for axial thermal conductivity measurements. An strange thermal conductivity phonograph record sample is sandwiched between two known thermal conductivity cylinder metal brass by thermal grease and pliable metal in order to reduce interfacial thermal b etween the cylinders. In addition, a thermocouple situated along the three material pieces produces information on the rate of heat flow by the two known thermal conductivity. Hence, thermal conductivity is calculated using the following equation Equation 5 Measurement of thermal Conductivity using cut-bar techniqueThere are around other techniques to measure thermal conductivity of solids which include Steady-State techniquesTransient TechniquesFour-Probe MethodLaser Flash MethodGuarded Heat menstruum MethodAngstrom MethodHeat stop Meter MethodPhoto thermal MethodTransient Hot Strip MethodTable 4 Other Techniques to measure thermal conductivity of solids6.2 METHODS TO MEASURE THERMAL CONDUCTIVITY OF LIQUIDSLiquids particles are situated in a cubic lattice, as energy moves from a single lattice plane to the following at a speed at which fit passes through the liquid of interest. Thermal conductivity can be estimated using Bridgemans equation Equation 6 Bridgemans Equationwhere N = Avogadros Constant = (6.023 x 1023)K = (Boltzmanns Constant) = (1.3807 x 10-23 J/K)V= Molar Mass = M/= Speed of sound through fluid sampleA summary of different techniques to measure thermal conductivities of liquids is shown on next page.LASER gimcrack METHODHOT-WIRE METHODDIFFRENTIAL SCANNING CALORIMTERTRANSIENT TECHNIQUES3 ezed METHODSTEADY STATE TECHNIUQESRADIAL warming FLOW instrumentCALORIMETERPHOTOPYROELECTRIC DEVICEMETHODS TO MEASURE THERMAL CONDUCTIVITY OF LIQUIDSFigure 9 Techniques to measure thermal conductivity of liquids6.2.1 HOT-WIRE METHODThe apparatus consists of hot-wire cells utilizing electrically insulated hot wires dependent on an electrically conducting fluid. Wires of minute diameter are immersed within the fluid and utilized simultaneously as an electrical underground as well as resistance thermometers, thus to enable reckoning of the increase in temperature due to the resistance heating. Thermal conductivity is determined using the same process as me ntioned to a higher place. Finite dimensions of the fluid can be improved, however modification to the finite dimension of wire can be reduced by utilizing minute hot-wires.6.2.2 3-OMEGA METHODIts features include a heating frequency (of 10 KHz), direct measurement of thermal conductivity and temperature range of -190 to 500. It comprises of alternating current and lock in amplifier to estimate thermal conductivity of the dielectric materials directly. Advantages of 3-Omega Method are being precise and unshakable. sheer metal situated on the specimen, an alternating current with frequency exceeds via cartoon leach causing heating of the material and measurement of voltage v (t) simultaneously. In addition, assumption of the heat flow along the cross plane axis of the film results in determination of the thermal conductivity using the following equation Equation 7 Determination of thermal conductivity using 3 Omega Methodwhere P1 = Powerb = Width of the strip=Increase in temp erature oscillation of the strip6.2.3 LASER FLASH METHODA liquid sample is sandwiched between a minute thin metal disk and a sampler holder. Sample holder minimizes thermal contact with the sample plus suppresses stray light transmitted from the optical maser to the IR detector. At the time when the laser beam is taken in the front surface of the metal disk, the heat flows downward through liquid sample and temperature rises. Thus, thermal conductivity can be estimated by the disks foil temperature without measuring the thickness of the sample liquid stratum and reference material.6.2.4 derivative instrument SCANNING CALORIMETER (DSC)It is a linear heating process that has super impose sinusoidal oscillation which yields in cyclic heating of the sample. Advantages of the method pursue as Short Analysis timeNo instrument modificationFigure 10 Apparatus of DSC(2010, Home, Internet, Available at http//pslc.ws/macrogcss/dsc.html, 1 November 2010)http//pslc.ws/macrogcss/dsc.html deli cate thermal gradient across the sampleExperiment is performed in a non-adiabatic surrounding numerous unknown specimens with identical length and cross sectioned areas are formed. Furthermore, known specimens with their conductivity and a density supplied to the unknown specimen are formed with identical length and cross sectional to the unknown specimen. Each specimen is subjected to an equal amount of rise in heat to estimate the specific heat capacity. Therefore, the thermal conductivity obtained isEquation 8 Measurement of thermal conductivity using DSCwhere D = diameter of the specimenM = Mass of the specimen= Specific heat capacity6.2.5 CALORIMETERA device designed to overcome the effects of convection that Prevents accurate measurement of liquids conductivities. Measures entire liquids conductivity rapidly and has several advantages which follow as Short time measurementAccuracyConstant current passes via thermistor which functions as a heating element immersed in the liqui d sample. As conductivity varies with liquid, the rate of temperature varies with liquids. Hence, thermal conductivity is inversely proportional to rate of temperature change.6.2.6 RADIAL HEAT FLOW APPARATUSFigure 11 Apparatus of Radia Heat Flow(2010, Home, Internet, Available at http//www.scielo.br/scielo.php?pid=S0104-66321999000400009script=sci_arttext, 27 October 2010)A steady-state technique which offers variation of conductivity under pressure as well as absolutes values of conductivity. It is fast and requires a small pressure gradient. Liquid sample is situated between two concentric cylinders (brass and Pyrex glass construction), the axis of the inner cylinder acts as a supply of heat which flows out radially crossways the point of fluid.Measurements of difference in temperature between inner and an outer surface of the layer of the fluid are taken to obtain thermal conductivity.6.3 METHODS TO MEASURE THERMAL CONDUCTIVITY OF GASFigure 12 TCD to measure thermal Conductivity of Gas(2010, Home, Internet, Available at http//www.scielo.br/scielo.php?script=sci_arttextpid=S0103-50532004000600009, 2 November 2010)Thermal conductivity detector (TCD) is utilized to measure thermal conductivity of gas by pulse injection. Heat is transmitted from hot to cold element by way of thermal conduction passing through the carrier gas. However, the difference in temperature between hot and cold element is maintained. Due to the thermal flow energy into the gas medium thermal gradient is generated. The power need to heat the hot element is a direct military rating of the electrically signal output for the thermal conductivity.DISCUSSIONAs mentioned above, the project is currently at the beginning of the research phase. Investigation into the areas described above is vital as the information gathered will have implications on the selection of the technique for the experiment. The project objectives should be met on schedule as there are not any limitations restricting the project from completion. Whilst performing the experiment in the near future, there may be some timing conflicts as there will be other students using the same machinery in the workshop but as enough time is allocated for the task in hand there should not be any difficulty in completing the objectives. Although there may be some complications when obtaining results, however with the knowledge and experience available via the lab technicians any problem(s) shall be duly addressed.CONCLUSIONIn conclusion the project aims and deliverables have been identified and the required tasks needed achieve the aims and produce the deliverables have been identified and discussed. An initial Gantt chart has been drawn up to illustrate the sequences and durations of the tasks to be completed. It can be seen that the performance so far is coincident with the planned set of activities for this time period within the Gantt chart. As a result, it is expected that the project is credibly to be complet ed on time.