By Deo du Plessis, mechanical engineer at Spoormaker & Partners | All photos by Simoné Senekal
The iconic new Engineering 4.0 facility on the University of Pretoria’s Experimental Farm campus was completed in February 2020 and features a state-of-the-art HVAC installation that combines specific laboratory technical requirements, energy efficiency, comfort and aesthetics.
The 6 800m2 facility is an expansion of the University of Pretoria’s (UP) prestigious Department of Civil Engineering, providing a new home for the Civil Engineering concrete and timber laboratories. In addition, the building also includes the new National road materials Referencing Testing laboratory and a training laboratory for the South African National Roads Agency (SANRAL), as well as a common multivolume foyer that will link the building to future phases as the School of Engineering expands even further.
Engineering 4.0 comprises a variety of spaces, each requiring different and room-specific design conditions. These include enclosed specific-use laboratories, open-plan training laboratories, curing and high-humidity rooms, sample preparation rooms, workshops, patch and server rooms, offices, a foyer, and an auditorium. The tests and experimental work being conducted in the Civil Engineering and SANRAL laboratories typically involve a range of concrete, bitumen, asphalt and soil sample preparation and property testing under different conditions.
The associated mechanical design criteria for the spaces therefore provided unique engineering challenges. Indoor environmental condition requirements for each individual space were agreed upon with the client and ranged from typical 22.5 ± 1.5°C laboratories, all the way to humidity rooms simultaneously requiring 25±2°C and 95±5% RH. Ventilation needs involved adhering not only to regulatory fresh air and fire rational requirements, but also ensuring that test-specific ventilation needs are met. These included fume cupboard ventilation, negative pressure spaces, positive pressure spaces, dedicated toxic gas ventilation, and dust filtration.
In addition to HVAC and building management systems (BMS) services, the spaces also required a plethora of other building services such as a compressed air network, various laboratory gas supplies, a hydraulic network to heavy machinery, as well as electrical and wet services to the various laboratory equipment and services. Furthermore, the architectural design intent involved mostly exposed services to align with the educational purposes of the facility. The design challenge was therefore to ensure the individual laboratory needs are met, whilst also providing the most sustainable design possible, all within the context of a service-intensive and aesthetically sensitive building.
Chiller plant and screened SANRAL plant room.Chiller plant and screened SANRAL plant room.
The HVAC system at UP Engineering 4.0 involves a central air-cooled chilled and hot water generation plant as cooling and heating source, located at ground level. Chilled water at 8°C and hot water at 50°C is circulated via a 4-pipe closed-loop piping system to a network of air handling units and fan coil units. The pumping arrangement includes a decoupled primary-secondary loop with hot and cold buffer tanks and variable volume secondary pumps to ensure pumping power is minimised whenever possible, in line with the cubic flow-power affinity law. Using a 4-pipe system reduced the baseline HVAC electrical energy usage by 68% with an estimated payback period of 3.9 years. Furthermore, no water consuming heat rejection systems were used, and all refrigerants were specified with an Ozone Depletion Potential (ODP) of zero.
The SANRAL laboratories are served by a series of above-ceiling chilled water fan coil units and various ventilation systems. A dedicated fresh air unit provides filtered, tempered and pre-conditioned fresh air to all spaces. A general central extraction system ensures neutral pressure in general laboratories. An independent bitumen extraction system ventilates from canopies and grilles located over oven areas where bitumen fumes are generated and ensures negative pressure in these spaces to avoid smell and fume contamination. Seven different fume cupboards ensure that tests involving toxic gasses such as Toluene can be carried out safely.
These fume cupboards are connected to two dedicated extraction systems using centrifugal fans and above-roof level exhausts. Each fume cupboard extraction system is also interlocked with a dedicated fresh air make-up system to ensure that the airflow in the rooms are always correctly balanced, with or without cupboards operational. In addition, safety features such as no-flow warnings and run statuses are indicated on purpose-made indicators in the user space. All of the above systems are located in one single plant room in order to be effectively screened. A seemingly complex but carefully planned plant room space separates intake and exhaust air, whilst ensuring required maintenance access, coordination and identification of all seven subsystems.
The Civil Engineering concrete laboratories are served by various internal subsystems and a dedicated fresh air unit located in an external screened plant room. The large multi-volume open plan heavy machinery laboratory is ventilated with tempered and pre-conditioned fresh air only to minimise energy usage, with air supplied via long-throw jet nozzles to increase air velocity at ground level and hence improve occupant thermal comfort in this semi-industrial environment. Various enclosed laboratories are air conditioned using exposed chilled water fan coil units and ventilated as per room requirements. PVC ducting and spark-proof ventilation systems are utilised where chemical corrosivity and explosive risks are applicable. The materials handling area where raw materials are loaded and distributed is separated from the main laboratory and inversely ventilated with fresh air supply from a high level and extraction at low level. This ensures that the space is not only always under negative pressure and properly ventilated, but that the heavier-than-air dust particles are captured effectively at low level.
A sample preparation room is used to cut and prepare concrete samples, resulting in high dust loading of fine particles. This space is ventilated by means of various canopies and strip curtain combinations to effectively capture concrete dust at the source, extracting it via high-velocity ducting to an external industrial baghouse filtration system. The system ensures high efficiency filtration, capturing extracted concrete dust in a series of cartridges and baghouse hoppers automatically pulsed clean via a compressed air nozzle manifold, before the clean air stream is sound attenuated and exhausted to atmosphere.
The concrete laboratories include five climate rooms where samples are cured in heated water baths. These rooms are air conditioned via dedicated chilled water fan coil units located outside the rooms to avoid continuous exposure of systems and controls to high room moisture levels. The coils are therefore also selected with high latent cooling abilities in order to dehumidify the air sufficiently when needed. The fan coil units are located above the concrete slab over the rooms, within an access floor void level which serves as a mezzanine floor to a series of offices above the laboratories. The units remain accessible for maintenance and are also visible via selected access floor tiles being transparent to keep with the exposed services theme. The offices are in turn served by further fan coil units above, creating yet another level of services.
Two special humidity and creep test rooms in the concrete laboratories present interesting psychrometric design and control challenges. The rooms are used to test concrete samples at specific and continuously controlled relative humidity and temperature levels of up to 95% relative humidity and 25°C dry-bulb temperature simultaneously. Each room was specified to be fully internally insulated with cold room panels, sealable and provided with floor drainage. A dedicated air handling unit located externally serves each room, with supply and return air recirculated via externally insulated ducting and special internally insulated air terminal plenums to avoid condensate issues inside ducting as far as possible.
Each room is provided with two in-room steam humidifiers. Air flow, cooling coil, heating capacity and steam supply volumes were psychrometrically designed to supply a high air change rate at high supply air temperature to improve controllability and minimise diffuser face condensation. With multiple and interdependent parameters of dry-bulb temperature, wet-bulb temperature and vapour pressure and the design condition requiring a room that is essentially always on the limit of full moisture saturation, the control requirements and variables had to be carefully planned to avoid oversaturation or over- and under-cooling. Similarly, control loop commissioning had to be fine-tuned to ensure sufficient dampening and stability.
The facility foyer space is a large multi-volume area served by two air handling units equipped with coils sufficient for full fresh air tempering but designed with return air and economy cycle functionality in order to minimise energy usage when ambient conditions are favourable. Exposed spiral duct networks were coordinated to suit the building’s curved shape and exposed floating ceiling panels and align with the network of exposed steel trusses. Local reception desks are provided with underfloor heating to improve local thermal comfort in winter. The auditorium is served by a dedicated air handling unit via high volume radial diffusers and double noise attenuators. Lastly, the central server room is served by a dedicated up-blow DX CRAC unit in a cold-isle configuration, and the patch rooms by DX blower coil units.
Top view of chiller plant and screened SANRAL plant room.Top view of chiller plant and screened SANRAL plant room.
A modern BMS system was installed at UP Engineering 4.0 to monitor and control all HVAC systems. The system has its own standalone IP network and comprises a series of field controllers in all the plant rooms, connected to a central front-end computer. The front-end is web-based, enabling remote or offsite connectivity when needed. The BMS facilitates full interrogation of HVAC systems, including set point management, all control parameters, room conditions, water temperatures, system statuses, and all system scheduling. Automatic alarming alerts the user to any problems such as tripping statuses, dirty filters or high temperatures.
Selected other services are also connected and monitored, including the compressed air plant, laboratory gas alarm panels, fire panel, generator and transformers. Continuous historic trending and logging of all conditions, loads, statuses and set points ensures traceability and enables informed decision making and tuning of systems to improve efficiency and service delivery.
Project take away
A project such as this can only be a success if a team of individuals work together and bring their expertise to the table in an enterprising way. As end-user client, Prof. Wynand Steyn (head of Department Civil Engineering) and Johan Scholtz (Laboratory Control instructor) ensured that complex design requirements were clarified and ensured throughout the project that the end product is nothing short of world class. The draughtsperson, Stephanie Esterhuizen, ensured the complex systems are accurately modelled in Revit and the design is well coordinated to ensure workable solutions. Andrew Wills and his team at Airgro did a great job with the mechanical installation and challenging commissioning requirements. Riaan van der Walt provided a state-of-the-art BMS and control system installation.
Overall, the end-user client is very satisfied, appreciative and excited about the world-class mechanical engineering services design and installation at the facility. UP Engineering 4.0 is an inspiring example of a facility where building services star one of the leading roles in the functionality, sustainability and aesthetics to create a comfortable and educational environment to its occupants – by engineers, for engineers.
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