Chapter 1313.1 ConvectionSlide 3Slide 4Slide 513.2 ConductionSlide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 1413.3 RadiationSlide 16Slide 17Slide 1813.4 ApplicationsSlide 20Chapter 13The Transfer of Heat13.1 ConvectionCONVECTIONConvection is the process in which heat is carried from one placeto another by the bulk movement of a fluid.convection currents13.1 ConvectionConceptual Example 1 Hot Water Baseboard Heating and RefrigeratorsHot water baseboard heating units are mounted on the wall next tothe floor. The cooling coil in a refrigerator is mounted near the top ofthe refrigerator. Each location is designed to maximize the production of convection currents. Explain how.13.1 Convection“Thermals” can be used by glider pilots to gain considerablealtitude.13.1 ConvectionForced Convection13.2 ConductionCONDUCTIONConduction is the process whereby heat is transferred directly througha material, with any bulk motion of the material playing no role in the transfer.One mechanism for conduction occurs when the atoms or moleculesin a hotter part of the material vibrate or move with greater energy thanthose in a cooler part.By means of collisions, the more energetic molecules pass on some oftheir energy to their less energetic neighbors.Materials that conduct heat well are called thermal conductors, and thosethat conduct heat poorly are called thermal insulators.13.2 ConductionThe amount of heat Q that is conducted through the bar depends on a number of factors:1. The time during which conduction takes place.2. The temperature difference between the ends of the bar.3. The cross sectional area of the bar.4. The length of the bar.13.2 ConductionCONDUCTION OF HEAT THROUGH A MATERIALThe heat Q conducted during a time t through a bar of lengthL and cross-sectional area A is LtTkAQSI Units of Thermal Conductivity: J/(s·m·Co)thermalconductivity13.2 Conduction13.2 ConductionMaterials with dead air spaces are usually excellent thermalinsulators.13.2 ConductionExample 4 Layered insulationOne wall of a house consists of plywood backed by insulation. The thermal conductivities ofthe insulation and plywood are, respectively,0.030 and 0.080 J/(s·m·Co), and thearea of the wall is 35m2.Find the amount of heat conducted through the wall in one hour.13.2 Conduction   plywoodinsulationLtTkALtTkABut first we must solve for the interface temperature.plywoodinsulationQQQ        m 019.0C0.4CmsJ080.0m 076.0C0.25CmsJ030.0 tTAtTAC8.5T13.2 Conduction     J105.9m 076.0s 3600C8.5C0.25m 35CmsJ030.052insulationQ13.2 ConductionConceptual Example 5 An Iced-Up RefrigeratorIn a refrigerator, heat is removed by a cold refrigerant fluid that circulates within a tubular space embedded within a metalplate. Decide whether the plate shouldbe made from aluminum or stainless steeland whether the arrangement works betteror worse when it becomes coated witha layer of ice.13.3 RadiationRADIATIONRadiation is the process in whichenergy is transferred by means ofelectromagnetic waves.A material that is a good absorber is also a good emitter.A material that absorbs completelyis called a perfect blackbody.13.3 RadiationTHE STEFAN-BOLTZMANN LAW OF RADIATIONThe radiant energy Q, emitted in a time t by an object that has aKelvin temperature T, a surface area A, and an emissivity e, is givenbyAtTeQ4The emissivity e is a dimensionless number between zero and one. It is the ratio of what an object radiates to what the object would radiate ifit were a perfect emitter. 428KmsJ1067.5 Stefan-Boltzmann constant13.3 RadiationExample 6 A Supergiant StarThe supergiant star Betelgeuse has a surface temperature ofabout 2900 K and emits a power of approximately 4x1030W. Assuming that Betelgeuse is a perfect emitter and spherical,find its radius.AtTeQ424 r13.3 RadiationtrTeQ244    m103K 2900KmsJ1067.514W1044114428304TetQr13.4 ApplicationsA thermos bottle minimizes heattransfer via conduction, convection,and radiation.13.4 ApplicationsThe halogen cooktop stove createselectromagnetic energy that passesthrough the ceramic top and is absorbeddirectly by the bottom of the