Building Energy Research Laboratory Department of Mechanical and Industrial Engineering University of Massachusetts Amherst Heat Transfer Analysis For The Fenestration System Simulation Round Robin 1998-99 Using Finite Element Method MIE 605 FINITE ELEMENT ANALYSIS Prof. Dr. Ian Grosse Submitted by Petar Blanua Project Outline Introduction Problem Definition Objective Physical System Definition Conduction model Finite Element Model Mesh
Results Conclusions/Future Work Introduction Improving the thermal performance of building envelope (walls, windows, doors, ceilings, attics, roofs, etc.). Computer modeling vs. experimental measurements Comparison of the same product easier Problem definition... ...Problem Definition Objective This computer finite element calculation will be used to: Show temperature and heat flux distribution.
Obtaining heat flows through the window. Calculation of ASHRAE based U-factor. Comparison to other labs results in NFRC simulation RR Mathematical Model Governing Equations 1. HEAT CONDUCTION only energy equation is present since there is solid body 2T T Q Cp t xi xi 2. THERMAL TRANSMITTANCE (to take into account frame effects) The governing equation is developed by imposing energy-balance which describes steadystate heat transfer by conduction. Must specify the frame/edge-glass geometry and the corresponding thermal conductivity for each of the various materials.
Numerical solver of the FEA software (THERM 2.0) is generating 2-D heat flow and temperature that satisfy the governing equation (by ISO 15099 Standard). In Cartesian coordinates this equation is: 2 2 T T q x 2 y 2 3. HEAT FLUX q, must be conserved across any surface where two materials meet and is given by: 2 2 T T
q fe ex e y y x where ex and ey are the components of the normal vector to the surface. Material Properties MA TE R I AL N A ME VI NYL (FLEXI BLE) SI LI CONE POLYI SOBYTULENE ( PI B) SI LI CA GEL ( DESI CCANT) STEEL - ANSI 304 STAI NLESS URETHANE ( LI QUI D) ALUMI NUM MOHAI R ( POLY) SWEEP
CONDUCTI VI TY ( W/ MK) 0.12 0.36 0.24 0.03 14.3 0.31 160 0.14 MA T E R I A L S U SE D FOR G LA ZI NG S Y ST E MS H A V E ALL CLEAR GLASS W I TH NOMI NAL THI CKNESS OF 3 MM, 4 MM, 5 MM, 6 MM. Sr. No. 1 2 3 4
Glazing Options 1.000" overall thickness Grid Option Clear glass (4mm) - Argon 95% - Low-e coating Grids type A Grids type A Clear glass (5mm) - Argon 95% - Low-e coating No grids Clear glass (6mm) - Argon 95% - Low-e coating No grids Clear glass (3mm) - Argon 95% - Low-e coating All materials in this window are treated
as having constant properties. Boundary conditions for indoor side (warm side) for glazing systems Nominal glass thickness Environmental temperature (C) Overall surface coeffi cient (W/ m2C) 6 mm 21.11 7.602 5 mm
21.11 7.614 4 mm 21.11 7.626 3 mm 21.11 7.628 Boundary conditions for outdoor side (cold side) for glazing systems Nominal glass thickness Environmental temperature (C)
Overall surface coeffi cient (W/ m2C) 6 mm -17.769 28.656 5 mm -17.769 28.658 4 mm -17.769 28.672
3 mm -17.769 28.673 Boundary Condition s Boundary conditions for indoor side (warm side) for frame* . Cross sections All Thermally Broken Aluminum Frame Overall surface coeffi cient (W/ m2C)
Thermally Unbroken Aluminum Frame Overall surface coeffi cient (W/ m2C) 7.893 * Temperature is 21.11C for all applied boundary conditions 8.29 Software THERM - Detailed finite element analysis of the two dimensional (2-D) heat transfer of fenestration product is done by public domain software THERM 2.0 (LBNL, 1998) Window 4.1 - PC based program used to calculate total window thermal performance indices (i.e. U-values, solar heat gain coefficients, shading coefficients and visible transmittance). (LBNL, 1994)
Mesh Number of Elements RESULTSIsotherms 1. Useful for predicting extreme temperature gradients (isotherms are very close together) that may lead to thermal stress or structural problems. 2. Isotherms are also useful for identifying hot or cold areas in the cross section, in order to predict thermal degradation or condensation. Color Infrared Results - Temperature gradients in the cross sections.
- Each temperature is represented by a different color - Cooler colors (purples and blues) are low temperatures, and warmer colors (yellows and reds) are higher temperatures. Color Flux Magnitude - Results Represent the heat flux vectors, with the magnitude of the flux represented by color Cooler colors are low flux (purples and blues) Warmer colors are higher flux (yellows and reds). No indication of the flux direction Results WINDOW 4.1 Report
ID:22 04/18/99 12:51:56 FrID: 28 FrID: 24 Name:Al - Double =============================== Mode:Design || EnvCond:1 || ||GlzSysID: 23#||GlzSysID: 23#| ||
Type:Horz Slider || FrID: 25|| Wid:660.6mm|| Wid:708.1mm|| Div ID: 12 || Div ID: 12||FrID: 29 Tilt: 90 || #H: 2 #V: 2 || #H: 2 #V: 2|| Size:Horz Slid AA || || ||
Width:1524.00mm || FrID: 27 || Height: 914.40mm || || || Results (cont.) (FEA Therm analysis results assembled in Window 4.1) S U M M A R Y O F R E S U LT S F O R F E A
T H E R M C O MPU T E R S I MU LAT I ON 6mm 5mm 4mm 3mm nominal nominal nominal nominal thickness thickness thickness thickness U-factor U-factor U-factor U-factor 2 2 2 (W/ m C) (W/ m C) (W/ m C) (W/ m2C) 3.616 3.520
3.418 3.413 Future work - Creation of three-dimensional (3-D) geometry of selected fenestration system - Finite element heat transfer calculations of selected fenestration system - Comparison of obtained results with two-dimensional (2-D) heat transfer analysis results - Comparison with experimental measurements - Developing correlation for 2-D heat transfer analysis results to account for 3-D effects Thank you.
