13.2 Unsteady cooling process of a multilayer ball非稳态多层圆球冷却问题T=303KT=723KBall_2AluminumBall1 Stellh=24W/(m2K)T=303KFocus: Compared with previous example, this examplefocuses on setting of unsteady heat conduction.6/46
6/46 Focus: Compared with previous example, this example focuses on setting of unsteady heat conduction. 13.2 Unsteady cooling process of a multilayer ball 非稳态多层圆球冷却问题
13.2 Unsteady cooling process of a multilayer ballKnown:A multilayer ball with initial uniform temperature of 723K was placed in air of303 K.Steel ball: D,=5 cm, density is 8030 kg/m3, capacity is502.48 J/(kg K), thermal conductivity is 16.27 W/(m K) .Al ball: D2=2 cm, density is 2719 kg/m3, capacity is 871J/(kg K), thermal conductivity is 202.4 W/(m K) .Outside boundary condition : convective BCFluid temperature:303KHeattransfercoefficient:h=24W/(m?K)Inside :initial temperature is 723 K.7/46
7/46 13.2 Unsteady cooling process of a multilayer ball Known： A multilayer ball with initial uniform temperature of 723 K was placed in air of 303 K. Steel ball：D1 =5 cm, density is 8030 kg/m3 , capacity is 502.48 J/(kg K), thermal conductivity is 16.27 W/(m K) . Al ball：D2 =2 cm, density is 2719 kg/m3 , capacity is 871 J/(kg K), thermal conductivity is 202.4 W/(m K) . ◼ Outside boundary condition : convective BC Fluid temperature: 303 K Heat transfer coefficient: h=24 W/(m2K) . ◼ Inside :initial temperature is 723 K
T=303KT=723KBall2Aluminum3rdkind ofboundarycondition.Ball 1 Stellh=24 W/(m2K)T=303KFig.1 Computational domain8/46
8/46 h=24 W/(m2K) 3rd kind of boundary condition. Fig.1 Computational domain Tf=303 K T=723 K T=303 K Ball_2 Aluminum Ball_1 Stell
Find: Temperature evolution in the multilayer ball.Solution:OC.TEnergy:div(gradT)atIt is an unsteady heat conduction problem with variable GAMA.Remark: here we write the energy governing equation inthe improved form with nominal density pCp . Theimproved form is adopted in our general teaching codeaswell in Fluent.9/46
9/46 Find: Temperature evolution in the multilayer ball. Solution: Energy: ( ) = ( ) T p div g C T t radT It is an unsteady heat conduction problem with variable GAMA. Remark: here we write the energy governing equation in the improved form with nominal density . The improved form is adopted in our general teaching code as well in Fluent. 𝜌𝐶𝑝
StarttheFluent softwareDinension1,Select3D dimension as it isO2Da 3Dproblem.O3DUptlonsDouble Precision2. If "display mesh afterDisplayMeshAfterReadingJLoadACTreading" is selected, after theStart ServerFluent is launched, the meshParallel (Local Iachine)8Solver Processeswill automatically shown in1Solver GPGPUs per Machine0the interface.3, For most cases single precision version of Fluent issufficient. For heat transfer problem, if the thermalconductivity ratio between different components arehigh, it is recommended to use Double precision version.10/46
10/46 Start the Fluent software 1、Select 3D dimension as it is a 3D problem. 2、If “display mesh after reading” is selected, after the Fluent is launched, the mesh will automatically shown in the interface. 3、For most cases single precision version of Fluent is sufficient. For heat transfer problem, if the thermal conductivity ratio between different components are high, it is recommended to use Double precision version