C19 -- Dual Core Hot Well Approach for High Rise Buildings PDF

Building designers, architects, and engineers have a substantial responsibility to ensure that MEP systems are integrated and in harmony with thebuilding’s architectural elements. A hot well concept is an integrated design concept developed to manage heat rejection from direct expansion (DX)refrigeration and air conditioning systems within high rise buildings. The working principle is to capture and collect heat rejection from condensingunits, which can in turn produce passive ventilation in an efficient manner to optimize the overall efficiency of the building’s HVAC systems.The hot well approach is an alternative to the classical heat rejection practice employed in most high-rise buildings using DX units (VRF, split unitsor refrigeration). Such buildings generally suffer from air-conditioning system performance concerns specifically at the higher floors due to heataccumulation. High rise buildings have outdoor condensing units commonly stacked on a strip of the building façade and covered with louvers to fitthe purpose of air circulation. In such cases, hot air extracted from condensing units will mix with the makeup air intake from almost the same location,causing the ambient air to heat up as it rises (and surrounding the outdoor condensing units), reaching very high temperatures at the upper floors. Theambient air temperature will increase and as such, the performance of the condensing units will be negatively impacted.

The alternative hot well approach is an integrated dual core concept: the first core is an equipment shaft connected with floor gratings andthe adjacent second hot well core is dedicated for heat rejection. The dual core hot well application is an integrated design approach which can be used inaddition to DX condensing units as a passive basement/parking ventilation. This will be accomplished via the heat stack effect and from theoperation of fans in condensing units. CFD analysis is carried out to support the design in four aspects:

• Ensuring equipment performance during operation, with complete separation between makeup air and rejected hot air.
• Generating a passive parking ventilation, i.e. reduction / elimination of the parking ventilation fans and corresponding energyconsumption.
• Enhancing the building facade from aesthetical and day lighting aspects.
• Enhancing equipment operating conditions and extending equipment lifetime.