1. Virtual Room Simulator (VRSIM)

2. Outline Introduction to VRSIM - What is CFD - What is VRSIM - VRSIM Application - Problem Analyzed by VRSIM Case Solved by VRSIM - CASE 1: Air Throw Distance Estimation - CASE 2: Unit Failure Analysis

3. What is CFD? CFD (computational fluid dynamics) is a branch of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows

4. What is VRSIM? -OYL customized in-house CFD software for HVAC problem -To enable the result generate in short time by person who is not CFD expert. -Two version available: VRSIM 2 - Simple block shape / Cartesian mesh, IAQ VRSIM 3 - Complex shape / Tetrahedral / triangle mesh

5. Problem Analyzed by VRSIM - Air Throw Distance & Air Flow Path - Temperature Distribution - Cooling time analysis - IAQ ( Draught Risk, Draft Temperature, Predicted Percentage Dissatisfied, Predicted Mean Vote) - Unit Failure Analysis

6. CASE 1 Air Throw Distance

7. CASE 1: Air Throw Distance Estimation 8.0 m 4.0 m Domain Layout Unit height = 3.0 m

8. CASE 1: Air throw Distance Estimation ≈ 5.4 m WM15G

9. CASE 1: Air Throw Distance Estimation - Compare with Experimental Data: VRSIMExperiment WM10G4.55.1 WM15G5.46.0 VRSIMExperiment WM10G6.36.0 WM15G7.06.9 Terminal velocity = 0.3 m/s Terminal velocity = 0.2 m/s

10. CASE 2 Unit Failure Analysis

11. CASE 2: Unit Failure Analysis Problem statement: 1) Outdoor unit is place close to each other/stack up to save space 2) Louver/wall to cover the outdoor unit from being see by the people, and often in limited space QUESTION: Will units fail due to short circuit/overheating? IF YES, WHO TO BLAME? (Both side will point finger to each other, for sure)

12. CASE 2: Unit Failure Analysis - Instead of design failure or manufacturing fault, in most cases it is cause by layout design problem (blocking flow, lack of fresh air, etc) - To prove the short circuit happen, VRSIM can be one of the quick and low cost solution.

13. CASE 2: Unit Failure Analysis UNIT BANNER WALL Side Photo:

14. UNIT (SL15C) FLOOR WALL BANNER ATMOSPHERE BUILDING WALL SIDE GAP BOTTOM GAP CASE 2: Unit Failure Analysis - Simulation domain:

15. CASE 2: Unit Failure Analysis 0.10 m BANNER 1.4 m 0.10 m 0.15 m 0.60 m BANNER Assumption: - The grill effect is negligible when compare with banner. - The opposite side of the “WALL” is open (as no information is provided) - The gap around the banner is only approximated. - Ambient temperature is 35 ˚C.

16. CASE 2: Unit Failure Analysis Result: Temperature Contour Side View

17. Temperature vs Time Plot at specific point CASE 2: Unit Failure Analysis

18. Simulation Conclusion: -The outdoor unit is subjected to high temperature operating condition in long run. - Unit will not fail instantaneously as operating temperature still below maximum allowed ( 46˚C ) - However, the life span of the compressor will definitely reduced due to continuous high temperature condition ( 40 – 42˚C )

19. THANK YOU