Introduction

Outdoor Units (ODU) of HVAC system are usually placed within balcony of High-rise buildings. It is very important that ODU receive adequate cooling within balcony so that temperature of the refrigerant can be kept below critical limits. Placement of ODU at each floor i.e., one above the other creates stack effect. Seasonal variation in wind flow direction along with the stack/buoyancy effect makes the performance evaluation of ODU more complex and it can be achieved using CFD.

Challenges

• Modelling and meshing of building with details of utility balcony & ODU.
• Modelling of heat dissipation by ODU along with the hot air short circuiting at ODU inlets.
• Design modifications in limited space of balcony.

SOLUTION

Thermal CFD simulation of Building with ODU is carried out for “No wind flow condition” and for “Wind flow from different directions condition (as per seasonal wind flow direction). Stack effect, hot air recirculation regions near ODU-Inlets and hot air short circuiting from ODU-Outlet to ODU-Inlets were causing the performance issue in ODU by raising ODU-Inlets temperature. Combined & separate effect of “stack & wind flow direction” on ODU performance is studied by identifying the hot air recirculation regions near ODU & hot air short circuiting at ODU-Inlets. ODU performance is improved by changing the elevation of ODU within balcony, by reducing flow obstructions nearby ODU & by modifying the grill opening present in front of ODU–Outlet.

BENEFITS

• For various scenarios, maximum temperature at all ODU-Inlets is predicted beforehand.
• Quick turnaround time to high swirl angle problem at ODU-Inlets.
• Cost effective solution for Reduced number of trials with efficient ODU performance.