Lecture Objectives:

1. Lecture Objectives: • Define the midterm project • Lean about eQUEST • Review exam problems

2. Midterm Project Objective: - Learn to use eQUEST - Learn to conduct parametric analyses for design optimization

3. 18’ 40’ 60’ Midterm Project • Use eQUEST to model 2 buildings: • Residential house • Duplex – 2 floors single zone per floor • Focus on envelope, zoning, and internal loads • Commercial Building • ECJ building

4. Midterm Project • Major Output: Energy consumption for both buildings • Electricity and • Gas • Part 1: Parametric analysis for residential building • Windows (glazing and shading) • Wall insulation • Wall surface properties • Shading • Part 2: Complex geometry, internal loads, and detailed mode

5. eQUEST • Example of • Defining envelope and internal loads • Selecting HVAC system • Presenting results • Finding design cooling and heating loads • Extracting simulation detail

6. Review • Heat transfer • Thermal analysis of building elements • External and internal boundary conditions • Weather data for boundary conditions • Modeling procedures • Numerical methods for solving equations

7. Review of heat transfer How to model: • Convection at surfaces • Radiation between surfaces • Conduction through building elements Steady state or unsteady state

8. Building elements

9. Weather data (TMY2 database) Use them for External boundary conditions Convection Long-wave Radiation Solar radiation • Direct • Diffuse • Reflected (diffuse)

10. Discretization

11. Discretization for conduction • T – temperature [C] • ρ – density [kg/m3] • cp – specific capacity [J/kgK] • k- conductivity [W/mK] • time [sec] x distance [m] Section considered in the following discussion Discretization in space Discretization in time

12. Finite volume (difference) method Boundaries of control volume Fir each node conservation of energy: explicit implicit

13. Implicit methods - example After rearranging: 2 Equations with 2 unknowns!  =0 To Tw Ti  =36 system of equation Tw Ti  =72 system of equation Tw Ti

14. Unsteady-state conductionImplicit method with linearization b1T1 + +c1T2+=f(Tair,T1,T2) a2T1+b2T2 + +c2T3+=f(T1 ,T2, T3) Air 1 4 3 2 5 Air 6 a3T2+b3T3+ +c3T4+=f(T2 ,T3 , T4) ……………………………….. a6T5+b6T6+ =f(T5 ,T6 , Tair) Matrix equation M × T = F for each time step M × T = F

15. Numerical methods PROBLEM Unsteady-state Steady-state System of equations for unsteady state process (nonlinear) System of equations for steady state process (nonlinear) Explicit Implicit Implicit Linearization (Matrix solver) Nonlinear (Newton-Raphson method) For each time step

16. Building Heating/Cooling System Plant Integration of HVAC and building physics models Load System Plant model Building Qbuiolding Heating/Cooling System Q including Ventilation and Dehumidification Plant Integrated models

17. Modeling steps • Define the domain • Analyze the most important phenomena and define the most important elements • Discretize the elements and define the connection • Write the energy and mass balance equations • Solve the equations (use numeric methods or solver) • Present the result

18. concrete Lconcrete insulation Linsulation Plenum (air) Lplenum acoustic tile Ltile QHVAC mS ,TS Room (air) TR Walmart store (L>>H, D>>H) TF Floor D=100m H-5m door L=200 m Practice for the ExamExample #1

19. Practice for the ExamExample #2 You are considering using the ventilated windows for ventilation of your new building and a sales person claims that it will reduce your annual energy bill by 10%. To check this claims you decided to model the performance of this window for your climate condition. QHVAC TRA Building fan creates under pressure in the room Building fan creates pressure in the room TRA QHVAC Air cavity open to outdoor air at the top, and to indoor air at the bottom