Lecture Objectives: Review linearization of nonlinear equation for unsteady state problems Learn about whole building modeling equations
Linearized radiation means linear system of equations Calculated based on temperature values from previous time step B0 C0 T0 F0 A1 B1 C1 T1 F1 A2 B2 C2 T2 F2 These coefficient will have Some radiation convection coefficients x = A3 B3 C3 T3 F3 A4 B4 C4 T4 F4 A5 B5 C5 T5 F5 A6 B6 T6 F6
Energy balance for air unsteady-state heat transfer QHVAC
System of equation for more than one element Roof air Left wall Right wall Floor Elements are connected by: Convection – air node Radiation – surface nodes
Example Tair is unknown and it is solved by system of equation :
System of equations (matrix) for single zone (room) 8 elements Three diagonal matrix for each element x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x Air equation
System of equations for a building Matrix for the whole building 4 rooms Rom matrixes Connected by common wall elements and airflow in-between room – Airflow simulation program (for example CONTAM) Energy Simulation program “meet” Airflow simulation program
HW3 Discuss the Analysis
Weather File for boundary conditions Typical Meteorological Year TMY, TMY2, TMY3 http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/
From Homework Assignment 3 Solution from previous years Day 1 Day 2 Day 3
Next HW (Project 1) We will use software: http://www.doe2.com/equest/ Soon we will have a class in the computer lab
eQUEST (DOE2) US Department of Energy & California utility customers eQUEST - interface for the DOE-2 solver DOE-2 - one of the most widely used ES program - recognized as the industry standard eQUEST very user friendly interface Good for life-cycle cost and parametric analyses Not very large capabilities for modeling of different HVAC systems Many simplified models Certain limitations related to research application - no capabilities for detailed modeling