CoolVent Workshop Alejandra Menchaca, PhD, Payette Associates Alonso Dominguez, MIT

Transcription

1 CoolVent Workshop Alejandra Menchaca, PhD, Payette Associates Alonso Dominguez, MIT

2 Outline Part I: Introduction to CoolVent Multi-zone models Interface Assumptions Demo Future improvements Part II: Using CoolVent with real buildings

3 PART I Introduction to CoolVent 3

4 Tools to model natural ventilation Wind-driven flow Buoyancy-driven flow Thermal mass effects Required expertise Simulation runtime Design stage Computational Fluid Dynamics (CFD) Yes Yes No High Hours/Days Late 4

5 Tools to model natural ventilation Computational Fluid Dynamics (CFD) Multi-zone models Wind-driven flow Yes Yes Buoyancy-driven flow Yes No Thermal mass effects No No Required expertise High Low Simulation runtime Hours/Days Minutes Design stage Late Early 5

6 Tools to model natural ventilation Computational Fluid Dynamics (CFD) Multi-zone models CoolVent Wind-driven flow Yes Yes Yes Buoyancy-driven flow Yes No Yes Thermal mass effects No No Yes Required expertise High Low Low Simulation runtime Hours/Days Minutes Minutes Design stage Late Early Early 6

7 How does CoolVent work? Each zone has one temperature and a pressure Every link has an area and a discharge coefficient Applies buoyancy and wind pressure equations, zone by zone 7

8 Inputs

9 Inputs Select from 5 building geometries Internal heat gains / schedule Building / glazing / openable area dimensions Outdoor conditions (.epw file / custom conditions) Thermal mass properties Night cooling schedule Use of fan-assisted ventilation (general or custom fan curves) Thermal comfort settings (ASHRAE 55 / adaptive / custom)

10 Outputs Graphical hourly representation of flowrate through space Hourly temperature and air flowrate variation for every zone Thermal comfort conditions Fan energy consumption Thermal stratification profile

11 Critical assumptions Flow is unidirectional through each opening Well mixed air in each zone No conduction through walls through roof to ground No heat gains through atria, chimneys Windows are open all the time (except night cooling) 11

12 Future Improvements Heat transfer through walls and roof Personalized fenestration elements; internal opening configuration Improved control for hybrid ventilation with thermal mass (windows, air conditioning, heating and fan) Comfort analysis using ASHRAE Adaptive Comfort Model Improved UI: Zoom for buildings with many floors Export results to Microsoft Excel

13 PART II Using CoolVent on Real Buildings

14 Case Study 1: 1 Bligh Street Objective: translate actual geometry into CoolVent model Modern building in Sydney s business district Buoyancy case only Top 11 floors

15 Case Study 1: 1 Bligh Street Open spaces Sections isolated from open office

16 Case Study 1: 1 Bligh Street Last three floors do not get air from the outside, but the atrium extends through them

17 Case Study 1: 1 Bligh Street Building type: look at expected airflow pattern

18 Case Study 1: 1 Bligh Street Can we try with a ventilation shaft building? Lengths of airflow paths are different!

19 Case Study 1: 1 Bligh Street Will the temperature in zone 1 be higher or lower than in the other zones? Zones 4 and 11 have similar airflow rates. Why? Will the temperatures in zones 4 and 11 be the same? Let s try to improve performance. Which would you suggest: increase height of the chimney or increase roof area? Add another floor worth of chimney (new chimney height is: m = 18 m). What happened to the percentage of time under comfortable conditions in the least comfortable floor? Why?

20 Case Study 2: Atlanta Marriot Marquise Objective: analyze mixed buoyancy-wind ventilation, thermal mass effect and night cooling feasibility Executive and Presidential Suites

21 Case Study 2: Atlanta Marriot Marquise Thinking of the buoyancy-driven case, what flow pattern do you expect in the building? Now think of the wind-driven case. What airflow pattern do you expect in the building? Is this the best orientation for wind-driven natural ventilation? Which orientation is better? Considering both buoyancy and wind-driven components, is this a good orientation? Compare the temperature profile in zone 1 with and without thermal mass Compare the temperature in zone 1 (with thermal mass) with and without night cooling