Virtual Room Simulator (VRSIM)

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

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

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

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

CASE 1Air Throw Distance

CASE 1: Air Throw Distance Estimation

8.0 m 8.0 m

4.0 m

Domain Layout

Unit height = 3.0 m

CASE 1: Air throw Distance Estimation

≈ 5.4 m

WM15G

CASE 1: Air Throw Distance Estimation- Compare with Experimental Data:

VRSIM Experiment

WM10G 4.5 5.1

WM15G 5.4 6.0

VRSIM Experiment

WM10G 6.3 6.0

WM15G 7.0 6.9

Terminal velocity = 0.3

m/s

Terminal velocity = 0.2 m/s

CASE 2Unit Failure

Analysis

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)

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.

CASE 2: Unit Failure Analysis

UNIT

BANNER

WALL

Side Photo:

UNIT (SL15C)

FLOOR

WALL

BANNER

ATMOSPHERE

BUILDING WALL

SIDE GAP

BOTTOM GAP

CASE 2: Unit Failure Analysis

- Simulation domain:

CASE 2: Unit Failure Analysis

0.10 m

BANNER 1.4 m

0.10 m

0.15 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.

CASE 2: Unit Failure Analysis

Result: Temperature Contour Side View

Temperature vs Time Plot at specific point

CASE 2: Unit Failure Analysis

CASE 2: Unit Failure Analysis

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)

THANK YOU