IMD

Ancient Zulu tradition is entrenched with the elements of migration, expansion and conquest. Donovan White campaigns to land King Shaka International Airport’s HVAC story.

It is unusual to find a ‘greenfield’ airport these days, but with the robust South African economy continuing to improve, Durban goes against the norm to provide travellers with first class African hospitality. Since the La Mercy grounds were acquired 40 years ago, the plan was to move Durban International up coast and provide the province with augmented travelling and cargo capabilities. This airport has kept the Zulu empire’s identity and provided a modern architectural and HVAC feel to the central hut of the tribe in their eponymous province of Kwa-Zulu Natal. 

Wind beneath our wings
Patrick Köhler, Spoormaker & Partners associate and HVAC engineer on this project says that the client’s design requirements called for a maximum of 25°C indoor design temperatures in public areas and 24°C to offices based on the outside air conditions of 31°C (dry bulb) and 26°C (wet bulb). The client called for heating to be omitted and for fresh air to be supplied at 51/s per person in offices and public areas, and 7.51/s per person in the airport’s retail components. Designs were based on an occupancy density of 5m2 air conditioned floor area per person in public areas and 10m2 per person in office areas.

Four Carrier water-cooled chillers with a total cooling capacity of approximately 9.5MW have been located in the plant room basement. This area is in close proximity to the HT/LT switchgear to limit electrical cabling requirements. Chilled water is supplied at approximately 6ºC and is distributed through externally insulated black steel pipes to the chilled water air-handling units located in the air-handling unit plant rooms through a primary-secondary pumping arrangement with variable speed secondary pumps.

Variable speed secondary pumps have been used in order for chilled water supply to match the cooling demand of the building at any time, explains Köhler. Water-cooled chillers are used to limit exposure of expensive dry cooled equipment to the high humidity corrosive exterior environment and reduce energy consumption of the cooling plant. Once chilled water has left the primary-secondary pumping arrangement it is passed on to the close-control air conditioning units feeding the server rooms and ceiling fan-coil units feeding the data and electrical rooms.

Two IT server rooms and one UPS (uninterrupted power supply) room are located in the basement and approximately 60 IT data and electrical rooms are distributed throughout the main terminal building. All require 24-hour air-conditioning and standby. The sensitive areas are air-conditioned on a full time basis through a separate chilled water system consisting of two Trane air-cooled chillers with chilled water close-control air-conditioning units and fan-coil units. The Trane chillers were selected for these critical applications to avoid dependence on a constant water supply. Located in an exposed plant room in the northern airside corridor, these chillers operate in a duty-standby configuration and are connected to emergency generator power supply.

Four Evapco closed-circuit cooling towers with total heat rejection capacity of about 12MW are located in a separate outside cooling tower building north west of the main terminal building. These cooling towers are linked to the main terminal via a service tunnel. Linking the cooling towers and the main terminal building, condenser water from the water-cooled chillers (at approximately 33oC) is pumped through 500mm diameter galvanized pipes located within a the service tunnel. The total absorbed power of the chiller and cooling tower plant operating at maximum capacity is approximately 2.5MW.

KSIA is split vertically into arrivals and departures components. The four air handling unit (AHU) plant rooms in the basement supply the arrivals levels whereas one AHU plant room on the roof supplies the departures and offices levels. Additionally, the plant rooms on the apron level supply the northern and southern airside corridors. In total, 20 Trox constant air volume AHUs serve the airports’ large open spaces. Offices, retail and lounges are served by 19 Trox variable air volume air-handling units with either ceiling mounted VAV diffusers or VAV dampers installed in the supply ducts. The total absorbed power of the air-handling and fan-coil units is approximately 320kW. 

The VAV and CAV AHUs have a total air supply capacity of 295m3/s. 24 Trox up-blow chilled water fan-coil units serveing the northern and southern air-side corridors with a total air-supply of 85m3/s. Due to the high outside humidity levels in Durban, fresh outside air is pre-conditioned (cooled only, no heating has been used in the terminal building) through a chilled water coil and then distributed to the various air-handling units. Four Trox constant air volume AHUs provide a total fresh outside air supply of approximately 70m3/s. All air conditioning operates with the environmentally friendly R-134A refrigerant.

Köhler states that the plant rooms, distribution shafts and ceiling spaces was were sufficiently provided for which limited the amount of coordination problems. The architects prepared a complete 3D model of the main terminal building that included all services and they also dedicated a team member responsible for coordination of individual services. This was very conducive in to identifying potential clashes with other services prior to it them becoming problems on site, he says.

To distribute the comfort of cooled air, Tekweni Air provided the galvanized sheet metal ducts for the air conditioning and ventilation systems, and aluminised ducting for the kitchen canopy exhaust systems. The total length of the ducting installed in the main terminal building is approximately 10km, says Köhler. Controls to main HVAC equipment are integrated into a Honeywell Building Management System (BMS), which links up on a front-end basis with an Alcatel BMS, which has been installed for other services.

Lungs of a warrior

No natural ventilation is used in the main terminal building and infiltration of outside air is limited. With the high outside humidity levels experienced there is a risk of condensation forming on cold indoor surfaces with infiltration of humid air. Mechanical ventilation is provided to the kitchens, ablution facilities (at 15l/s/m2), change rooms and smoking rooms. Conditioned fresh outside air is supplied to the storage facilities and baggage handling section to limit high humidity and dust infiltration in these areas.
Additionally, mechanical ventilation and smoke ventilation has been provided to the  basement street area and to the food and beverage (F&B) outlets and lounges to allow for canopy extraction. Exhaust canopies remove cooking smells and smoke from restaurants and the smoke extract ventilation has been provided for with a total extract volume of approximately 1100m3/s. All the air-handling units are interfaced with a smoke detection system which will shut units down in the event of a fire. They are also connected to an emergency generator power supply should a break in energy supply occur.

Modern Day Hut

Köhler explains that the KSIA main terminal has been constructed with a sheet metal roof that has been insulated to achieve an overall heat transmission coefficient (U-value) of 0.45W/m2K. The insulation limits heat gains through the roof and acts as an important acoustic requirement to limit noise transmission into the building, especially from aircrafts. Additionally the roof has an aluminium finish that reflects solar heat gains.

The thermal performance of the building envelope was optimized to limit heat gains.
High performance single glass glazing enhances visual, thermal and acoustic performance with an overall heat transmission coefficient (U-value) of 3.8W/m2K and a shading coefficient of 0.52. High performance single glazing has been utilized on external overhangs and shading devices to limit solar heat gains through the airport’s glass. The main terminal’s orientation is determined by the runway to a north-south axis with substantial east and west exposures. The impact on comfort and heat gains have been limited though the aforementioned overhangs and external shading devices.

Today’s Impi Army
In response to the limited expansion possibilities at Durban Airport KSIA was constructed to cater for more international and domestic flights and increased cargo handling capacity. Köhler tells of how Spoormaker & Partners and DTM JV were requested to be part of the ILembe EPC Joint Venture Bid for this project which has included the main terminal building, cargo terminal, control tower, fire rescue building and ancillary buildings. “We were excited and privileged to be part of such a high profile project especially the challenge to finish such an extensive project within the short construction period prior to the 2010 World Cup”, he says.

Construction started mid 2007 and continued for 32 months until the airport opened on 1 May 2010. ILembe says that the project had to be fast-tracked in order to achieve their target date. Should this date have been missed, a penalty of R55 000 would have been incurred per day over deadline. Communication between the 16 ILembe joint venture companies was enhanced through a web-based document management system, ACONEX.

All official correspondence including reports, design and construction drawings, quality inspection sheets, commissioning results and hand-over documentation were uploaded on the ACONEX system, therefore ensuring consistency between different team members in the format and way that documentation was issued and resulted in a centralised record of all official documentation. Documentation control offices were set up on site to verify that documentation was issued in the correct format and distributed to all concerned parties.

‘Mfecane’: Crushing the Difficulties
“The difficult element was not so much meeting the design specifications but to cater for changes during the construction phase as the design and construction proceeded together”, commented Köhler. Difficulties were experienced in the retail, F&B and the sensitive area components. Their extent and location were finalised when a large portion of first fix services were installed and main service reticulation routes finalised.

To overcome these challenges, Köhler details the way the VAV system serving the retail and F&B areas provided the required flexibility to cater for changes in these areas. The chilled water system serving the sensitive areas provide the required flexibility and also allows future adaptability to cater for changes in location and additional data rooms. The ventilation installations serving the F&B components and lounges, such as where there are canopy exhaust.