Heating, ventilation and air conditioning (HVAC) has always been about more than simply cooling a space. Rising energy costs, more demanding indoor air requirements, and increasingly specialised manufacturing and processing are placing greater emphasis on how temperature, humidity, ventilation and air quality are collectively managed.
“A well-designed HVAC system can support occupant comfort, process requirements, productivity and the overall energy performance of buildings,” says Alin Gomes, director of Industrial Climate Engineering (ICE). “For decision-makers in commercial, manufacturing and industrial sectors, the real value lies in working with an experienced HVAC specialist that understands clients’ building, process and operating requirements and can translate these into a practical, efficient solution.”
Every building is different
For ICE, effective HVAC design starts with a clear principle: every building and process has its own requirements. Rather than applying a one-size-fits-all solution, ICE considers the building layout, occupancy, internal and external heat loads, required air flow, filtration, pressure relationships, and applicable safety and ventilation requirements before developing a system. ICE’s turnkey capability extends from design to fabrication, installation, commissioning and the co-ordination of related construction and electrical works, with a focus on performance, efficiency and long-term reliability.
Standard packaged or off-the-shelf equipment can be entirely suitable for many applications, but is not automatically the best fit for every building or process. “The key point is correct selection and control. Equipment needs to be sized for the actual load profile and selected for the required operating range, rather than simply chosen on nominal capacity,” Gomes advises. Modern HVAC equipment may use staged capacity, variable-speed compressors, inverter drives or other controls to respond to changing loads. An oversized or poorly controlled system can still cycle excessively, operate inefficiently and struggle with humidity control. “Good design is about matching the HVAC plant to the building’s actual demand and ensuring it can operate efficiently at full and partial load,” Gomes adds.
Ventilation and indoor air quality
People exhale carbon dioxid and occupied buildings also contain moisture, odours and other indoor contaminants. Outdoor air is introduced to dilute these contaminants and maintain acceptable indoor air quality. The required outdoor air quantity depends on the occupancy and application, in accordance with SANS 10400-O. Ventilation rates vary by occupancy type and may be expressed as litres per second per person or air changes per hour, so the design must be checked against the requirement applicable to the specific space.
Gomes cites examples where clients have called on ICE to improve ventilation after indoor air quality assessments identified insufficient outdoor air. “In one case, the system was recirculating too much return air and introducing too little outdoor air. We rebalanced the system so that the required volume of outdoor air could be introduced while maintaining the overall supply air performance.” Where the air-conditioning equipment configuration limits outdoor air provision, a dedicated fresh air system can be installed and integrated with the air-conditioning system.
Outdoor air also forms part of the building’s cooling or heating load. On very hot or cold days, bringing untreated outdoor air into a conditioned space increases the energy requirement of the HVAC plant. Where appropriate, ICE tempers or pre-conditions outdoor air and considers measures such as heat recovery, so that ventilation requirements are met without placing unnecessary load on the main air-conditioning plant.
Turnkey projects in process environments
ICE’s turnkey approach is illustrated by two recent projects in specialised process environments where climate control formed an integral part of the production requirements.
The first involved a large-scale central HVAC plant serving multiple controlled environment production areas. The system provides heated and chilled water together with multiple stages of filtration, including HEPA filtration, to maintain closely controlled temperature and relative humidity conditions. “The filtration and environmental control requirements were significantly more stringent than those of a typical comfort-cooling installation,” Gomes observes. The temperature-sensitive production process shaped the air distribution strategy: directing cold supply air onto the product could have caused damaging localised temperature stress, so the air movement was designed to avoid direct cold draughts across the sensitive production area while using controlled circulation to achieve a more even temperature.
The second process-cooling project required a simpler solution, but equally careful control. Large circulation and ventilation fans manage air movement, while the key requirement was to maintain the process medium and supply water at a stable temperature. “We cooled the water to a carefully controlled set point suited to the production requirement, using heat exchangers to separate the chiller’s closed water circuit from the client’s process-water circuit. Rather than passing process water directly through the chiller, the heat exchanger transfers cooling between the two circuits. This protects the chiller water loop while allowing the process water to be managed according to the specific water-quality requirements of the application,” Gomes explains.
Energy efficiency and technology improvement
HVAC technology continues to improve, particularly in compressor control, heat exchanger design, fans, controls and refrigeration selection. Gomes points to an ICE project in Johannesburg where measured electricity consumption fell by approximately 21 to 23% after the rooftop chiller plant was replaced, while noting that savings vary from project to project and depend on the efficiency of the existing plant, operating hours, controls, load profile and the replacement technology. “The opportunity for performance and sustainability improvement is not only in replacing equipment. Correct sizing, controls, commissioning and ongoing optimisation all contribute to HVAC energy efficiency while maintaining the climate conditions the building or process requires.”
For more information contact Alin Gomes, Industrial Climate Engineering,
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